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Proceedings
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HTPP14 Munich
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HTPP14 Munich
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HTPP14 Munich
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TIME SUNDAY
03.07.16
MONDAY
04.07.16
TUESDAY
05.07.16
WEDNESDAY
06.07.16
THURSDAY
07.07.16
Chairs
Session 1 Session 4 Session 7 Session 10
Jürgen Mentel
Karsten Hartz-Behrend
Jochen Schein
Jean-Luc Meunier
John Lowke
Maryam Aghaei
Yann Cressault
Dan Lev
9:30 Jochen Schein Andre Anders Jürgen Mentel John Lowke
Introduction
Magnetron sputtering:
From the historic roots to
recent discoveries of spoke
and breathing modes
What for high intensity
discharge lamps beneficial
in the age of LEDs
Contributions of plasma
physics to metal-inert-gas
welding
10:00 Dava Feili Maryam Aghaei Mikhail Benilov Jean-Luc Meunier
Electric Propulsion Mis-
sions at the European Space
Agency (ESA)
Inductively Coupled Plas-
ma Mass Spectrometry:
what can we learn from
modelling?
State-of-the-art in the sim-
ulation of plasma-electrode
interaction in arc discharges
Tuning nucleation and
functionalization of
nanostructures in a thermal
plasma: the case of graphene
10:30 - 10:45 Coffee Break
Chairs
Session 2 Session 5 Session 8 Session 11
Mikhail Benilov
Andre Anders
A. J. M. Pemen
Laurent Fulchéri
Michael Keidar
Gervais Soucy
Klaus-Dieter Weltmann
Syed Salman Asad
10:45 A. J. M. Pemen Michael Keidar Klaus-Dieter Weltmann Suresh Joshi
Perspectives of supercritical
fluids for switching appli-
cations
Recent Progress in Cold
Plasma Application for
Cancer Therapy
Plasma Medicine – innova-
tive physics for medical
application
Novel plasma-antimicrobial
solution and the mecha-
nisms of bacterial inactiva-
tion
11:15 Masaya Shigeta Marco Boselli Syed Salman Asad Yann Cressault
Modelling for flu-
id-dynamic transport of
nano-powder growing
around a thermal plasma jet
Design oriented modeling
of thermal plasma sources
and processes with a focus
on nanoparticles synthesis,
metal welding and cutting
Atmospheric pressure
plasma sources: from la-
boratory and publications to
real applications and indus-
trial production
Study of the radiation of
high power arcs
11:45 Georg Mauer Gervais Soucy Laurent Fulchéri Dan Lev
Understanding plasma
spray-physical vapor depo-
sition (PS-PVD): current
state and challenges
DC thermal submerged
plasma treatment of con-
taminated solution con-
taining carboxylic acid
Direct decarbonization of
methane by thermal plasma
for the co synthesis of car-
bon black and hydrogen
Plasma Propulsion System
Development for Commer-
cial Satellites
12:15 -13:30 Lunch Closing
Session 3 Session 6 Session 9
Chairs Marina Kühn-Kauffeldt
Masaya Shigeta
Dava Feili
Marco Boselli
Georg Mauer
Suresh Joshi
13:30 -14:15 Poster Introduction
14:15 -14:25 Coffee Break
14:25 -15:10 Poster Introduction
15:10 -17:00 Poster Session
Seminar
17:00 -18:00
Andre Anders
"How to get published"
SOCIAL EVENTS
17:00
-21:00
Opening
19:30 - 21:30
Munich City Tour
19:00 - 23:00
Visit to Hofbräuhaus
19:00 - 23:00
Gala Dinner
Conference program
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Session 3: Poster Introduction
Poster
Number
Introduction
time Speaker Title
S3-1 13:30 Surov Alexander Steam, methane and carbon dioxide thermal plasma interac-
tion with perhalocarbons
S3-2 13:35 Francesco Strappavec-
cia
H2020 NanoDome Project: A Multiscale Approach to Gas
Phase Nanoparticle Synthesis
S3-3 13:40 Boselli Marco
Treatment of infected ex-vivo human skin tissue with a low
power atmospheric inductively coupled plasma source op-
timized through design oriented simulations
S3-4 13:45 Benmouffok Malyk Numerical study of spark generated in a 3D configuration:
preliminary results
S3-5 13:50 Wang Fei Theoretical study of Ar-CO2-Fe arc plasmas used in hybrid
laser MAG welding: calculation of radiative properties
S3-6 13:55 Müller Meike Cold Atmospheric Plasma Technology for Decontamination
of Space Equipment
S3-7 14:00 Lisnyak Marina Numerical modelling of an electric arc and its interaction
with the anode
S3-8 14:05 Alkhasli Ilkin Modelling of the Temperature Distribution Inside a Sprayed
Particle in Air Plasma Spraying
S3-9 14:10 Bredack Mathias Development of an AC-GMAW process for welding
high-strength fine grained steels
S3-10 14:25 Oh Jeong-Hwan
Numerical analysis of RF thermal plasma for the preparation
of metal boride nanoparticles embedded soft radiation
shielding material
S3-11 14:30 Quéméneur Jean Electrical arc movement and commutation modelling in the
Low-Voltage Circuit Breaker
S3-12 14:35 Quéméneur Jean Experimental investigations on arc movement and commu-
tation in the Low-Voltage Circuit Breaker
S3-13 14:40 Tanaka Manabu Diode-rectified multiphase ac arc with bipolar electrodes for
degradation of electrode erosion
S3-14 14:45 Jeong Hyung Geun Selective synthesis of anatase and rutile TiO2 nanoparticles
by DC thermal plasma
S3-15 14:50 Benilov Mikhail Simple model of current transfer to rod anodes of dc and ac
high-pressure arc discharges
S3-16 14:55 Kühn Marvin Plasma actuators for flow control
S3-17 15:00 Valensi Flavien
Synthesis and characterisation of carbon nanostructures
substituted with boron and/or nitrogen using electric arc
plasma
S3-18 15:05 Kirpichev Dmitry Synthesis of oxygen-free TiN compounds nanosized powders
in the DC plasma arc reactor
Poster schedule
HTPP14 Munich
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Session 6: Poster Introduction
S6-1 13:30 Mallon Michael Physical simplified arc model for Gas Metal Arc Welding
(GMAW) process including cathode and anode layers
S6-2 13:35 Atzberger Alexander Investigations of a pulsed current wire arc spraying process
S6-3 13:40 Kozakov Ruslan Combined electrical and optical partial discharge diagnostics
S6-4 13:45 Valensi Flavien Anode energy transfer in a transient arc
S6-5 13:50 Zhong Linlin
Effects of Copper on Thermophysical Properties and Net
Emission Coefficients of CO2-N2 Mixtures in High-Voltage
Circuit Breakers
S6-6 13:55 Cressault Yann Properties of air thermal plasma contaminated with AgC and
AgNi vapours resulting from electrodes' erosion
S6-7 14:00 Chen Zhexin Composition of Non-LTE CO2-CH4 Plasma with Condensed
Phase
S6-8 14:05 Tanaka Yasunori
High rate synthesis of Si/SiOx nanoparticles/nanowires using
modulated induction thermal plasmas with controlled feed-
stock feeding
S6-9 14:10 Kim Keun Su Role of hydrogen in high-yield growth of boron nitride nano-
tubes by induction thermal plasma
S6-10 14:25 Kirpichev Dmitry Leucoxene carbothermal treatment in DC plasma-arc reactor
S6-11 14:30 Surov Alexander High voltage AC plasma torches with long electric arcs for
plasma-chemical applications
S6-12 14:35 Surov Alexander The Investigation of the AC Plasma Torch Working Conditions
for the Plasma Chemical Supplement
S6-13 14:40 Tanaka Yasunori
Development of a loop type of inductively coupled thermal
plasma torch for large-area and rapid surface oxidation of Si
substrate
S6-14 14:45 Szulc Michal
Suitability of thermal plasmas for large-area bacteria inactiva-
tion on temperature-sensitive surfaces – first results with Ge-
obacillus stearothermophilus spores
S6-15 14:50 Iha Shugo Investigation of Inter-electrodes Plasma Composition in Re-
moval of Oxide layer from Steel Surface by Vacuum Arc
S6-16 14:55 Ilkin Alkhasli Influence of Powder Particles on the Plasma Characteristics in
Multi-arc Plasma Spraying
S6-17 15:00 Kodama Naoto 2-D temperature estimation in Ar-O2 induction thermal plas-
mas for TiO2 nanopowder synthesis
S6-18 15:05 Kirner Stefan Anode surface structure influence on high current moving arcs
in atmosphere
HTPP14 Munich
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Session 9: Poster Introduction
S9-1 13:30 Dobkevicius Mantas Double-Sided Ion Thruster for Contactless Space Debris
Removal
S9-2 13:35 Belinger Antoine Parasitic capacitances in DBD tranformerless power supply:
an issue?
S9-3 13:40 Mohanta Antaryami Optical emission spectroscopic study of CH4 plasma during
the production of graphene by induction plasma synthesis
S9-4 13:45 Boselli Marco
Design oriented modelling for the synthesis process of
copper nanoparticles by a radio-frequency induction thermal
plasma system
S9-5 13:50 Cressault Yann Plasma of Electric Arc Discharge in Air with Silver Vapours
S9-6 13:55 Uhrlandt Dirk Optical study of anode phenomena in vacuum switching arcs
S9-7 14:00 Valensi Flavien Arc tracking power balance for copper and aluminium wires
S9-8 14:05 Mostaghimi Javad A Novel Inductively Coupled Plasma Torch for Mass Spec-
trometry (ICP-MS)
S9-9 14:10 Wang Panpan Computational fluid dynamic analysis of Plasma Spray
Physical Vapor Deposition
S9-10 14:25 He Wenting Excitation temperature and concentration profiles of an
Ar/He jet under Plasma Spray-PVD conditions
S9-11 14:30 Ondac Peter Arc-anode attachment area in DC arc plasma torch
S9-12 14:35 Paniel Elodie Study of BSO properties dedicated to measurement of elec-
tric charge on dielectric surface
S9-13 14:40 Zhang Hantian Influence of gas medium on the switching arc decaying be-
hav-iour by non-chemically equilibrium calculation
S9-14 14:45 Zimmer Felix Investigations of low temperature atmospheric pressure
plasma sources for surface treatment
S9-15 14:50 Hashizume Taro Influence of doped oxide on tungsten-based electrode
evaporation in multiphase AC arc
S9-16 14:55 Lee Seungjun Preparation of silicon nanopowder from wafer waste by us-
ing thermal plasma
S9-17 15:00 Benilov Mikhail Comparing models of near-cathode sheaths in high-pressure
arcs
S9-18 15:05 Mavier Fabrice Pulsed arc plasma jet synchronized with drop-on-demand
dispenser
S9-19 15:15 Surov Alexander
The Analysis of Physics Processes in the Electric Discharge
Chamber of the AC Plasma Torch under the High Pressure of
the Working Gas
HTPP14 Munich
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3rd
July 17:00 - 21:00: Welcome reception After the long journey to the capital of Bavaria we would like to welcome all the participants with some traditional snacks
as well as what Bavaria is most famous for – excellent beer out of a real keg!
The registration and welcome reception will be held on campus of the Universität der Bundeswehr München in the foyer
of the Audimax.
4th
July 19:30: Excursion - Munich insider city tour
Join one of the unconventional city tours and become a Munich insider! A highly trained team of real insiders
will expertly guide you around Munich.
You can choose between following tours
Legends and Myths
Mysterious Signs and Symbols
Crime Scene Munich
You can sign up for one of these tours at the conference desk. The excursions will start at three different locations
in downtown Munich.
Social events
HTPP14 Munich
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5th
July 19:00: Visit to Hofbräuhaus - “Where the whole world meets up!“
Munich, beer and the Hofbräuhaus – they've all belonged together for the past 400 years. Since the early 19th
century, the famous beer cellar at the heart of the city has been a magnet for the people of Munich and travelers
from every corner of the globe. It’s delicious beer, traditional specialties, the legendary Bavarian Gemütlichkeit
and fascinating history have made the Hofbräuhaus into the most famous beer cellar in the world.
All conference participants are kindly invited to experience the Hofbräuhaus located at the Platzl in the heart of
Munich.
The Hofbräuhaus can be conveniently reached by public transport from the conference venue (Directions can be
found here; recommended departure from the conference site 18:15).
Further informations will be provided at the conference.
6th
July 19:00: Gala dinner at Schloss Blutenburg
Built as a country residence by Duke Albrecht III in the 1430th the Blutenburg castle next to the river Würm still
reflects 15th-century atmosphere. Located in the west of Munich Schloss Blutenburg is far less crowded, however
not less picturesque than its famous neighbor, the Nymphenburg palace. Through the whole year the moated
castle with its spacious bailey attracts attention of many visitors. It is a perfect place for concerts, craft markets,
weddings and other festivities.
We hope, that the idyllic atmosphere in- and outside the castle walls together with traditional and international
culinary delights will make this evening a memorable gala dinner experience.
We will provide a bus transport to the gala dinner and back. The bus will leave the conference site at 18:00 and
will also stop at the U-Bahn station Neuperlach Süd. The bus from the gala dinner will leave at 23:00.
The city center and the gala dinner location are also connected to the public transport system
HTPP14 Munich
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Abstracts
HTPP14 Munich
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HTPP14 Munich
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Monday
HTPP14 Munich
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HTPP14 Munich: Session 1
3
Electric Propulsion Missions at the European Space Agency (ESA) J Gonzalez del Amo
1*
1European Space Agency, ESTEC, Keplerlaan 1, 2200 AG Noordwijk ZH, The Netherlands
General
ESA missions such as AlphaBus, GOCE, Smart-1 and Ar-
temis have paved the way for the use of electric propulsion
in future ESA missions: Lisa-pathfinder, Bepi Colombo,
Small GEO, Al-phabus, LISA, etc. Furthermore, ESA is the
coordinator of an activity with the European Community
that will provide a clear roadmap for preparing the future of
the Electric propulsion in Europe. This paper will present
the current and future challenges of the electric propulsion
in Europe.
ESA is supporting the European Industry in the field of
space telecommunications by having more performing sat-
ellites capable of saving more than one thousand kilos of
propellant by using electric propulsion for orbit raising
manoeuvres. ESA Neosat and Electra satellites will per-
form orbit raising and station keeping manoeuvres with
Electric Propulsion systems which will allow to reduce the
launching costs by selecting smaller launchers or partici-
pating as a co-passenger with another spacecraft in the
same launcher. Besides, new Scientific and Earth observa-
tion missions dictate new challenging requirements for
propulsion systems and components based on advanced
technologies such as microNewton thrusters. New space
missions in the frame of Exploration will also require so-
phisticated propulsion systems to reach planets such as
Mars or Venus and in some cases bring back to Earth sam-
ples from asteroids or comets. Finally the use of Electric
Propulsion to perform orbit raising saving huge amounts of
propellant has also attracted the attention of the future Gal-
ileo programme at ESA, the use of EP will allow to place 4
spacecraft in Ariane 5 and 3 spacecraft in Soyuz, allowing
low launcher costs. Due to all these new space projects,
ESA is currently involved in activities related to spacecraft
electric propulsion, from the basic research and develop-
ment of conventional and new concepts to the manufactur-
ing, AIV and flight control of the propulsion subsystems of
several European satellites.
HTPP14 Munich: Session 1
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HTPP14 Munich: Session 2
5
Perspectives of Supercritical Fluids for Switching Applications A J M Pemen
1*, E J M van Heesch
1, J Zhang
1, F J C M Beckers
1, T Huiskamp
1,
W F L M Hoeben1
1 Eindhoven University of Technology, Faculty of Electrical Engineering
Introduction
Fast and repetitive switching in high-power circuits is a
challenging task where the ultimate solutions still have to
be found. Areas of application are power switches in
high-voltage networks and heavy duty switches for pulsed
power applications.
Supercritical switch media
We propose a new approach: the use of supercritical fluids
as switching medium. Supercritical fluids have insulation
strength and thermal properties like liquids and fluidity,
self-healing and absence of bubbles like gases. These prop-
erties are very beneficial of power switching, and in partic-
ular allow very high breakdown voltages (thus compact
switches) and very fast recovery behaviour (thus repetitive
switches). We will present the concept of a supercritical
switch, and data of breakdown behaviour of a prototype
supercritical switch [1]. In addition, a model for calculating
the recovery time will be presented, supported by experi-
mental data on the recovery behaviour of supercritical ni-
trogen.
Results of experiments
The figures below give some results on breakdown behav-
iour and dielectric recovery behaviour of supercritical ni-
trogen.
Figure 1: Breakdown field for supercritical nitrogen for various electrode
gap distances and voltage rise rates (room T, 70 bar).
Figure 2: Measured and simulated time resolved recovery voltage in
supercritical nitrogen (room T).
References
[1] J Zhang, E J M van Heesch, F J C M Beckers, T
Huiskamp, A J M Pemen, 2014 Breakdown Voltage
and Recovery Rate Estimation of a Supercritical Ni-
trogen Plasma Switch, IEEE Trans Plasma Science,
42-2
[2] Zhang J, van Heesch E J M, Beckers F J C M, Pemen A J
M, Smeets R P P, Namihira T, Markosyan A H, 2015
Breakdown strength and dielectric recovery in a high
pressure supercritical nitrogen switch, IEEE Transac-
tions on Dielectrics and Electrical Insulation, 22-4
HTPP14 Munich: Session 2
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HTPP14 Munich: Session 2
7
Modelling for fluid-dynamic transport of nanopowder growing
around a thermal plasma jet
M Shigeta1*
1 Joining and Welding Research Institute, Osaka University, Japan
1. Introduction
Thermal plasmas have been anticipated as a powerful tool
for nanopowder fabrication [1]. However, it is difficult to
investigate the collective growth of nanopowder generated
in/around a thermal plasma flow because the process in-
volves remarkably rapid phase conversion. Furthermore,
the plasma fringe is fluid-dynamically unstable and there-
fore the growing nanopowder is transported by dynamic
convection as well as diffusion and thermophoresis. A
model which simply describes such complicated processes
with low computational costs has been developed.
2. Model description Extending the previous model which simply but consist-
ently described spherical nanoparticles’ growth through
nucleation, condensation and coagulation [2], the govern-
ing equations including transports by convection, diffu-
sion and thermophoresis have been derived [3]. Because it
is indispensable for numerical simulation to express mul-
ti-scale eddies which result in turbulent-like feature of a
thermal plasma flow and capture steep gradients in the
spatial distributions of temperature and nanopowder, a
solver implemented with suitable schemes and algorithm
has also been developed. An argon plasma jet is ejected
from the nozzle. Assumed that the raw material was already
vaporized in the nozzle, silicon vapor is supplied at 0.1
g/min with the plasma jet.
3. Results and discussion
Figure 1 show instantaneous distributions of the tempera-
ture and vorticity of the thermal plasma and the number
density and mean volume diameters of the silicon na-
nopowder at the same moment. The high-temperature
plasma jet forms eddies because of Kelvin-Helmholtz
instability and entrains the surrounding non-ionized gas.
As the jet goes downstream, the eddies break to smaller
ones and the plasma jet is deformed. These features of
turbulence transition were also reported in the experi-
mental study [4]. Transported with the plasma convection,
the silicon vapor also diffuses across the plasma’s fringe
where the vapor experiences the temperature decrease. As
a result, the vapor becomes supersaturated and changes its
phase to nanopowder through nucleation and condensation.
The nanopowder is transported by convection and diffu-
sion. The regions of large diameters coincide with those of
low number densities of nanoparticles, because the size of
nanoparticles increases through coagulation among them-
selves decreasing their own numbers.
Figure 2: Spatial distributions of (a)plasma temperature, (b) vorticity
contour lines, (c) particle concentration,(d) mean volume diameters.
Acknowledgements
This work was partly supported by a Japan Society for the
Promotion of Science Grant-in-Aid for Scientific Research
(B) (Grant No. 15H03919).
References
[1] Shigeta M, Murphy A B, 2011 Thermal Plasmas for
Nanofabrication J. Phys. D: Appl. Phys. 44 174025
[2] Nemchinsky V A, Shigeta M, 2012 Simple equations
to describe aerosol growth Modelling Simulation Ma-
ter. Sci. Eng. 20 045017
[3] Shigeta M, 2015 Simple nonequilibrium model of
collective growth and transport of metal nanomist in a
thermal plasma process Theoretical Appl. Mech. Ja-
pan 63 147
[4] Pfender E, Fincke J, Spores R, 1991 Entrainment of
Cold Gas into Thermal Plasma Jets Plasma Chem.
Plasma Process. 11 529
HTPP14 Munich: Session 2
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HTPP14 Munich: Session 2
9
Understanding Plasma Spray-Physical Vapor Deposition
(PS-PVD): current state and challenges G Mauer
1*, W He
1, R Vaßen
1
1 Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research,
IEK-1: Materials Synthesis and Processing
PS-PVD development Plasma spraying at very low-pressures (VLPPS) has been
developed with the aim of depositing uniform and thin
coatings with large area coverage. At typical pressures of
50-200 Pa, the characteristics of the plasma jet change
compared to conventional low-pressure plasma spraying
processes (LPPS, formerly often termed vacuum plasma
spraying, VPS) operating at 5-20 kPa. Using VLPPS,
quite thin and dense metallic coatings can be obtained as
well as ceramic layers for some special applications. Such
processes operate at a conventional power level similar to
atmospheric plasma spraying (APS).
The enhancement of VLPPS by higher electrical input
power has led to the development of the LPPS-TF process
(TF = thin film) [1]. An input power level of 180 kW was
achieved at electrical currents up to 3000 A and plasma
gas flow up to 200 slpm. The plasma plume expands to a
length of more than 1.5 m and to 200-400 mm in diameter.
With LPPS-TF, the deposition still occurs predominantly
by molten droplets forming highly flowable splats and
thus enabling very thin and dense microstructures, e.g. for
ceramic gas separation membranes or electrolytes for solid
oxide fuel cells. Beyond LPPS-TF, it is even possible to
evaporate the feedstock material substantially by using
specific feedstock powders and process parameters so that
deposition takes place considerably from the vapor phase.
Such a process is termed plasma spray-PVD (PS-PVD) [2]
and enables advanced microstructures, as applied e.g. for
thermal barrier coatings (TBCs).
Plasma jet characteristics At low pressure, generally higher ionization rates are ob-
tained since the ionization temperatures are decreased.
However, investigations of PS-PVD plasma jets by optical
emission spectroscopy [3] revealed that at spray distances
between 400 mm and 1200 mm, the recombination of ions
and electrons in a plasma jet at typical PS-PVD conditions
is already advanced so that the degree of ionization is rel-
atively small. Furthermore, at the lowest investigated
chamber pressure of 200 Pa, a moderate departure from
local thermal equilibrium (LTE) was identified as the
temperatures of electrons and heavy species (ions and
atoms) were slightly different.
At typical PS-PVD conditions, the pressure at the nozzle
exit is larger than the ambient chamber pressure; thus, the
jet is under-expanded. Supersonic conditions with Mach
numbers >2 are attained at the nozzle exit.
Feedstock particle treatment Knudsen numbers were calculated for a representative
feedstock particle with a diameter of 1 µm at typical
PS-PVD plasma jet conditions [4]. The results indicate
that free molecular flow conditions prevail. Thus, contin-
uum gas dynamics approaches are not appropriate and the
kinetic theory of gases must be used instead to describe
the plasma particle interaction. Applying such methods,
the degree of feedstock vaporization was estimated. The
results showed that the feedstock treatment, particularly
along the very first trajectory segment between injector
and nozzle exit, is essential. Besides feedstock character-
istics and plasma parameters, the spray distance, substrate
temperature, and substrate material have significant im-
pact on coating formation mechanisms [5].
Challenges We currently have limited understanding of interactions
between low pressure thermal plasma and feedstock parti-
cles. Phase transformation pathways are not well under-
stood. In particular, if large feedstock fractions are evapo-
rated, also the gas flow around the substrate and the for-
mation of a boundary layer are obviously important as
even non-line of sight deposition is observed.
References
[1] Smith M F, Hall A C, Fleetwood J D, Meyer P, 2011
Very Low Pressure Plasma Spray – A Review of an
Emerging Technology in the Thermal Spray Commu-
nity Coatings 1 117
[2] von Niessen K, Gindrat M, 2011, Plasma Spray-PVD:
A New Thermal Spray Process to Deposit Out of the
Vapor Phase J. Therm. Spray Technol. 20 736
[3] G Mauer, R Vaßen 2012, Plasma Spray-PVD: Plasma
Characterization and Impact on Coating Properties J.
Phys.: Conf. Ser. 406 012005
[4] G Mauer, 2014 Plasma Characteristics and Plas-
ma-Feedstock Interaction Under PS-PVD Process
Conditions Plasma Chem. Plasma Proc. 34 1171
[5] G Mauer, A Hospach, N Zotov, R Vaßen, 2013 Process
Conditions and Microstructures of Ceramic Coatings
by Gas Phase Deposition Based on Plasma Spraying, J.
Therm. Spray Technol. 22 83-89
HTPP14 Munich: Session 2
10
HTPP14 Munich: Session 3, Poster S3-1
11
Steam, methane and carbon dioxide thermal plasma interaction
with perhalocarbons A V Surov
*, S D Popov, V E Popov, D I Subbotin, N V Obraztsov, J A Kuchina, E O Serba, Gh V Nakonechny, V A
Spodobin, A V Pavlov, A V Nikonov
Institute for Electrophysics and Electric Power of Russian Academy of Sciences (IEE RAS), Dvortsovayaemb. 18, 191186,
St.-Petersburg, Russia
Perfluorinated and perchlorinated compounds are formed
as waste in the manufacture of many up-to-date industrial
chemicals and during the operation of equipment contain-
ing these substances – refrigerators, air conditioners, elec-
trical equipment, etc. Furthermore, a need exists in the
processing of persistent organic pollutants (for example
dichloro-diphenyl-trichloroethane). Nowadays accumu-
lated amount of mixtures of high-boiling organochlorine
compounds, including PCBs and chlorobenzenes, as well
as increasing amount of used plastics require environ-
mentally safe recycling.
Alternative to conventional low-temperature methods of
toxic wastes incineration is their processing in thermal
plasma. Usage of the electric arc plasma with average
temperatures up to 5000 K allows destruction of complex
organic and inorganic compounds to form less toxic
chemicals.
Decomposition of organic material must be carried out
with the complete mixing and high rate of reactions be-
tween raw material components [1]. In the case of effec-
tive quenching there is no reverse synthesis of the polya-
tomic compounds decomposed in plasma. For example,
the method of tetrafluorocarbon decomposition by micro-
wave steam plasma is proposed [2].
However, complete destruction to only inorganic halogen
compounds (HF, HCl) is possible with large excess of
steam in the reaction system and increased power con-
sumption because of hydrogen deficiency.
The paper presents the method of perhalocarbons decom-
position by the thermal plasma of steam, methane, and
carbon dioxide mixture produced in the AC arc plasma
torch (Figure 1) [3]. The required hydrogen is produced
by thermal steam and carbon dioxide plasma reforming of
methane [4]. Hydrogen halides are corrosive compounds
so carbon dioxide is used to protect the plasma torch elec-
trodes. Besides, it does not introduce additional chemical
elements in the system. Generalized scheme of a stoichi-
ometric process is described by the equation:
0.15925 CCl4 + 0.167 H2O+0.068 CO2 + 0.07575 CH4 =
0.303 CO + 0.637 HCl
Flow rates of main components for the certain plasma
torch model are: H2O - 3 g/s, CO2 - 3 g/s, CH4 - 1.21 g/s.
Calculated plasma enthalpy for complete decomposition
of carbon tetrachloride, without heat loss (in adiabatic
conditions) is 2.5 MJ/kg.
Figure 1: Three phase steam AC plasma torch.
This is due to its low thermal resistance, but other orga-
nochlorine compounds can be formed without additional
energy.
The tests of carbon tetrachloride decomposition with di-
rectly feeding of reagents into the plasma torch and the
analysis of main products were carried out.
In this case, carbon tetrachloride flow rate did not exceed
10 % of the stoichiometric value (2.44 g/s).
The experimental data agree satisfactorily with the theo-
retical calculations. This method will allow efficient de-
composition of any halogenated compounds.
Acknowledgements
The work is partially supported by the RFBR grant 15-08-
05909-a.
References
[1] Fulcheri L, Fabry F, Takali S, Rohani V, 2015
ThreePhase AC Arc Plasma Systems: A Review
Plasma Chem Plasma Process 35 565
[2] Narengerile, Saito H, Watanabe T, 2009 Decomposi-
tion of tetrafluoromethane by water plasma generated
under atmospheric pressure Thin Solid Films 518 929
[3] Rutberg Ph, Nakonechny Gh, Pavlov A, Popov S,
Serba E, Surov A, 2015 AC plasma torch with a
H2O/CO2/CH4 mix as the working gas for methane
reforming J. Phys. D: Appl. Phys. 48 245204
[4] Rutberg Ph, Kuznetsov V, Popov V, Popov S, Surov A,
Subbotin D, Bratsev A, 2015 Conversion of methane
by CO2 + H2O + CH4 plasma Applied Energy 148 15
HTPP14 Munich: Session 3, Poster S3-1
12
HTPP14 Munich: Session 3, Poster S3-2
13
H2020 NanoDome Project: A Multiscale Approach to Gas Phase
Nanoparticle Synthesis E Ghedini*
1,2, F Strappaveccia
1, V Colombo
1,2
1 Department of Industrial Engineering (DIN), Alma Mater Studiorum – Università di Bologna, Bologna, Italy
2 Industrial Research Centre for Advanced Mechanics and Materials (CIRI-MAM), Alma Mater Studiorum – Università di
Bologna, Bologna, Italy
Introduction
Nanoparticle synthesis processes have been developed for
a wide range of materials such as pure metals (e.g. Si, Ni,
W), oxides (e.g. ZnO, TiO2) or alloys (e.g. Au-Cu). How-
ever, none of the available processing routes is able to
precisely control properties such as particle size distribu-
tion, composition, purity and dispersibility in a reliable
and reproducible way, and at the same time guarantee a
high-volume, continuous production at attractive
cost/benefit ratios. Wet-phase methods produce nanoparti-
cles with very well-defined size and morphology, but they
often lack scale-up capabilities and cost-effectiveness. On
the contrary, GP synthesis processes, such as plasma pro-
cesses, provide a good balance between precision synthe-
sis and production scale, even though accurate control of
particle properties still remains a big challenge.
The H2020 NanoDome project is aimed to solve some of
these issues by providing an open source modelling tool to
improve existing nanoparticle gas phase synthesis process
design capabilities, at research and industrial level. In this
contribution, a general overview of the NanoDome physi-
cal model developed during the first year of the project is
provided.
Concept
The NanoDome model describes the phenomena occur-
ring at all the length scales involved in the nanoparticle
synthesis process (Figure 1), from individual atoms to
macroscopic reactor scale flow, using a multiscale ap-
proach. Atomistic scale: Atomistic modelling (MD) is
performed within the project with the aim to provide fun-
damental understanding and data for setting up the basic
mechanisms of formation (nucleation) and growth (con-
densation) and inter-particle interaction (sintering and
aggregation).
Mesoscale: The core of the project is a coarse grained
mesoscopic model for the description of nanoparticles
behaviour and aggregate formation, including homogene-
ous and heterogeneous nucleation, coagulation, coales-
cence and sintering. Nanoparticles and aggregates mutual
interaction and formation is predicted using a Langevin
dynamics based motion prediction.
Continuum scale: Continuum reactor models are linked
with the mesoscopic model to provide information on the
environment in which the particles are evolving (i.e. p, T,
species concentration).
Figure 1: NanoDome mulstiscale approach.
Chemical kinetics: Chemical kinetics for the continuum
and the mesoscopic model will be developed using DFT
and statistical thermodynamics: a detailed chemistry mod-
el will be developed for each material system and then
reduced in order to be implemented in the continuum and
mesoscopic models.
Interfacing: Coupling and linking between mesoscopic
model and continuum reactor models is included in the
modelling tool.
Figure 2: Nanoparticle structures predicted by NanoDome.
Expected results
The model will be able to predict the nanoparticles size
distribution at the end of the synthesis process, together
with the morphology of the aggregates (i.e. partially sin-
tered nanoparticles) and agglomerates (i.e. softly bounded
larger structure) (Figure 2) and nanoparticles chemical
composition. Coupling and linking with reactor scale
models will enable a realistic process conditions for the
mesoscopic model and a direct exploitation at industrial
level.
Acknowledgements
This project has received funding from the European Un-
ion’s Horizon 2020 research and innovation programme
under grant agreement No 646121.
HTPP14 Munich: Session 3, Poster S3-2
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HTPP14 Munich: Session 3, Poster S3-3
15
Treatment of infected ex-vivo human skin tissue with a low power
atmospheric inductively coupled plasma source optimized through
design oriented simulations D Barbieri
1, E Bondioli
3, M Boselli
1,2,4*, V Colombo
1,2,4, M Fiorini
1, M Gherardi
1,2,4, M Ghetti
3, R Laurita
1,4, A Liguori
2,4,
D Melandri3, P Minghetti
3, A Miserocchi
2, V Purpura
3, A Scaramelli
1, E Simoncelli
1, A Stancampiano
1,4, E Traldi
1
1Department of Industrial Engineering and
2Industrial Research Centre for Advanced Mechanics and Materials
Alma Mater Studiorum-Università di Bologna, Via Saragozza 8, Bologna 40123, Italy 3 Burn Centre and Emilia Romagna Regional Skin Bank,“M. Bufalini” Hospital, viale Ghirotti 286, Cesena 47023, Italy
4AlmaPlasma s.r.l., Viale del Risorgimento 2, Bologna 40136, Italy
Bacterial contamination is very common in wounds and
Staphylococcus aureus appears to be the bacterial species
most frequently isolated therein. Traditional treatments
are frequently used to counteract this clinical condition
and new alternatives were developed when the first ones
resulted ineffective [1]. Among them, the use of cold at-
mospheric plasmas as a source of reactive species, radi-
cals, UV, heat and charged particles is a promising tech-
nology to reduce bacterial load in infected and chronic
wounds. In particular, low power inductively coupled
plasma sources integrated with a quenching device (cold
ICP) were recently developed in order to efficiently pro-
duce reactive species at atmospheric pressure that, in turn,
could be used for potential biomedical applications, in-
cluding the antibacterial activity [2]. The present study is
aimed to realize an optimized device (Figure 1) by means
of design oriented simulations and evaluate the decon-
tamination potential of the ICP plasma source on infected
human dermis and its effects on the structural properties
of this tissue. In order to optimize the generation of reac-
tive species and ensuring the biocompatibility of the ef-
fluent temperature values, a simulative study oriented to
process design of an optimized quenching device was
performed with FLUENT commercial software. Through
modelling of several different inner geometries and oper-
ating conditions of the device its optimal layout was de-
fined. The device has been then experimentally charac-
terized in terms of temperature reached by the (bio) sub-
strate in the downstream region of the cold ICP source
during the treatment, as well as for the production of ni-
tric oxide species (NO and NO2) and the total UV irradi-
ance at the biointerphase. The most promising operating
conditions were selected to perform test on Ex-vivo hu-
man skin tissue. Fresh dermis samples were taken from
the multi-organ and/or multi-tissue donors and cut under
sterile conditions into 2x2cm pieces. 100 µl of suspen-
sions with different concentrations (106–10
4 CFU/ml) of
Staphylococcus aureus (ATCC® 6538) were applied to
the surface of dermis samples and were left for 15
minutes to permit bacterial attachment. Each sample was
exposed to the effluent of the cold ICP plasma source for
2 minutes. Untreated samples were used as positive con-
trol (CTR). After treatment small uniform fragments
(1x1cm) of all samples were incubated on Columbia Agar
+ 5% sheep blood plates (bioMérieux) at 37°C for 24 h
for microbiological analysis. Cell viability and skin in-
tegrity were also evaluated after plasma treatment. This
preliminary study shows that the treatment with the cold
ICP plasma source can effectively decontaminate human
dermis from Staphylococcus aureus preserving tissue
structural properties and cell viability.
Figure 1: Low power ICP with optimized quenching device.
References
[1] Barbieri D, Boselli M, Cavrini F, Colombo V, Gher-
ardi M, Landini M P, Laurita R, Liguori A, Stan-
campiano A, 2015 Investigation of the antimicrobial
activity at safe levels for eukaryotic cells of a low
power atmospheric pressure inductively coupled
plasma source Biointerphases 10 029519
[2] Boselli M, Cavrini F, Colombo V, Ghedini E, Gher-
ardi M, Laurita R, Liguori A, Sanibondi P, Stan-
campiano A, 2014 High-speed and Schlieren imag-
ing of a low power inductively coupled plasma
source for potential biomedical applications IEEE
Trans. Plasma Sci. 42 2748
HTPP14 Munich: Session 3, Poster S3-3
16
HTPP14 Munich: Session 3, Poster S3-4
17
Numerical study of spark generated in a 3D configuration:
preliminary results M Benmouffok
1, P Freton
2, P Teulet
2, J J Gonzalez
2
1Continental Automotive France, 1 avenue Paul Ourliac 31100 Toulouse, France
2LAPLACE, Université de Toulouse, CNRS, INPT, UPS, 118, route de Narbonne, 31062 Toulouse, France
Introduction
Due to the need to protect environment and population
from pollutants and global warming, the legislation con-
cerning emissions becomes stricter, specifically in Europe
with Euro standards. Consequently car manufacturers
have to improve the engines. The effort is done on
spark-ignited (SI) engines for cost considerations but also
due to its high potential of evolution. Several ways are
investigated for the improvement of SI engines particu-
larly the working with highly diluted mixture with air
(lean mixture) or with EGR (Exhaust Gas Recirculation).
For this, it’s necessary to develop high performance igni-
tion systems by a better understanding of the spark’s
physics.
The importance of the early phase of the spark in a simpli-
fied 2D configuration for MHD simulations has been
highlighted in a previous work [1]. In this paper we real-
ized a 3D numerical simulation in order to observe the
behaviour of the discharge with or without a laminar
crossing flow. Numerical model
In order to study the plasma flow and the expansion of the
hot gases, the commercial Ansys Fluent software is used
allowing developing a magneto-hydrodynamic model
(MHD) based on the finite volume method. The Na-
vier-Stokes equations are solved coupled with the scalar
potential conservation to ensure the current continuity.
The whole conservation equations system has to be writ-
ten under the generalized form of Patankar as shown be-
low:
Transport and thermodynamic properties of air are tabu-
lated as functions of the temperature and the pressure in
the ranges respectively 300-60000 K and
1-400 bar under the Local Thermal Equilibrium assump-
tion (LTE). The radiation losses are taken into account
using the Net Emission Coefficient approximation. Elec-
trodes are not taken into account in the computational
domain and the current intensity is imposed by the mean
of a specific boundary condition on the electrode surface.
The magnetic field is neglected due to the short duration
(t≤200 ns) of the pulsed current applying. The flow is as-
sumed to be laminar.
Geometry
The computational domain is based on a calorimeter
chamber developed in order to study the energy deposition
produced by the spark. The volume is closed and all the
boundary conditions are adiabatic.
Figure 1: Cutting plane – Mesh of the calorimeter chamber.
Results
The model allows us to observe the propagation of tem-
perature and pressure fields across the computational do-
main. The spark will be studied by two means:
Numerical visualization of temperature and pressure
fields
Reconstructed gradients of density
The first point will allow us to explain the specific shape
of hot gases. The second point will be used to follow the
position of the pressure wave and hot gases toward several
directions. Finally, we will show the influence of a cross-
ing flow imposed by a source term on the discharge. We
will compare the obtained result with the simulation in
quiescent air without crossing flow.
Acknowledgements
This work was funded by the National Research Agency
(ANR) under contract no. ANR- 12 -VPTT-0002-01,
FAMAC project.
References [1] Benmouffok M et al., 2014 2D numerical simula-
tion of spark discharge in air XIIIth
High-Tech Plasma Processes
HTPP14 Munich: Session 3, Poster S3-4
18
HTPP14 Munich: Session 3, Poster S3-5
19
Theoretical study of Ar-CO2-Fe arc plasmas used in hybrid laser
MAG welding: calculation of radiative properties Y Cressault
1, F Wang
1, 2, H Li
2, K Yang
2 Ph. Teulet
1
1LAPLACE (Laboratoire Plasma et Conversion d'Energie), Université de Toulouse; CNRS, UPS, INPT; 118 route de
Narbonne, F-31062 Toulouse, France 2Tianjin Key Laboratory of Advanced Joining Technology, Tianjin University, Tianjin, 300072, P. R. China
Hybrid laser gas active metal arc (MAG) welding has re-
ceived much attention in both academia and industry in
recent years, which contributed to the improvement of
weld quality and efficiency and reduction of disad-
vantages of each method used separately [1]. In the weld-
ing process, metal vapour (Fe for steel workpiece and
electrode) can be formed by laser beam and the Ar-CO2
(for example, composed of 82% Ar and 18% CO2) arc
plasmas, and iron vapour can definitely affect the arc
plasmas and thus the welding process.
In a previous work [2], the mutual attraction between iron
vapour and Ar-CO2 plasmas were experimentally investi-
gated and the maximum electron temperature is about
16 kK. To complete the experimental study further and
develop numerical models, this paper deals with the radia-
tion of Ar-CO2-Fe plasmas and demonstrates the effect of
different iron proportion on the radiation. Although some
values can be found in the literature concerning pure CO2
[3] and plasma mixturesAr-Fe [4] and CO2-Cu [5], few
data are available for Ar-CO2-Fe plasmas.
The plasma composition was calculated for the atmos-
pheric pressure considering 39 species. In order to take
into account the iron vapours issued from the erosion of
the workpiece and the droplets, we calculated the radiative
losses using the Net Emission Coefficient assuming iso-
thermal and homogeneous plasma. The radiation coming
from atomic continua, molecular continua, molecular
bands and atomic lines were taken into account according
to previous works [3-5]. 16 molecular systems and 119621
atomic lines were considered. As a very small concentra-
tion of metal vapours strongly increases the role of the
resonance lines and strongly modifies the radiative prop-
erties, a particular attention was paid to broadening’ lines.
With the Net Emission coefficient, we can estimate not
only the total radiative losses but also the integrated emis-
sions for specific spectral intervals [i-i+1]. This second
possibility is very interesting since the ratio α between
two integrated emissions (corresponding to two spectral
intervals) can be used to determine the plasma’s tempera-
ture from optical measurements [6]. As a consequence of
that, several results will be presented: variation of the net
emission coefficient of Ar-CO2-Fe plasma in function of
temperature, plasma sizes and iron concentration; varia-
tion of α for a large selection of spectral intervals. Our
next work will concern fast temperature and iron compo-
sition determination for Ar-CO2-Fe plasmas used in hybrid
laser MAG welding by high speed CCD cameras coupled
with narrow optical filters. The research is expected to
further demonstrate the footprint of iron vapour and its
effect on hybrid welding process.
Acknowledgements
This work was supported by National Natural Science
Foundation of China (No. 51475325), Tianjin Research
Program of Application Foundation and Advanced Tech-
nology (No. 14JCYBJC19100). This work was supported
by the program of China Scholarship Council (CSC) for
joint-PhD students (No. 201506250116).
References
[1] Bagger C, Olsen F O 2005 Review of laser hybrid
welding J. Laser Appl. 17 2
[2] Gu X Y, Li H, Yang L J, Gao Y 2013 Coupling
mechanism of laser and arcs of laser-twin-arc hybrid
welding and its effect on welding process Optics &
Laser Technology 48 246
[3] Cressault Y, Teulet Ph, Gonzalez J J, Gleizes A, Rob-
in-Jouan Ph 2005 Transport and radiative properties
of CO2 arc plasma: application for circuit-breaker
modelling, XVIth
Symposium on Physics of Switching
Arc, Brno (Czech Republic), 1, 46
[4] Cressault Y and Gleizes A 2013 Thermal plasma
properties for Ar-Al, Ar-Fe and Ar-Cu mixtures used
in welding plasmas process: I Net emission coeffi-
cients at atmospheric pressure J. Phys. D: Appl. Phys.
46 415206
[5] Billoux T, Cressault Y, Boretskij V F, Veklich A N,
Gleizes A 2012 Net emission coefficient of CO2-Cu
thermal plasmas: role of copper and molecules
Journal of Physics: Conference Series. 406 012027
[6] Rouffet M E, Cressault Y, Gleizes A, Hlina J 2010
Thermal plasma diagnostic method on the analysis of
large spectral regions of plasma radiation J. Phys. D:
Appl. Phys. 41125204
HTPP14 Munich: Session 3, Poster S3-5
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HTPP14 Munich: Session 3, Poster S3-6
21
Cold Atmospheric Plasma Technology for Decontamination of
Space Equipment M Müller
1*, I Semenov
1, S Binder
2, J L Zimmermann
2, T Shimizu
2, G E Morfill
2,
P Rettberg3, M H Thoma
4, H M Thomas
1
1 DLR-Forschungsgruppe Komplexe Plasmen, 82230 Wessling, Germany
2 terraplasma GmbH, 85748 Garching, Germany
3DLR-Institut für Luft- und Raumfahrtmedizin, 51147 Köln, Germany
4Justus-Liebig-Universität, 35392 Gießen, Germany
Introduction
For future planned space expeditions one of the chal-
lenges will be the compliance of the planetary protection
policy [1]. Therefore, the Committee on Space Research
COSPAR defines five categories of missions with differ-
ent requirements of sterilisation [1]. The common meth-
ods for the sterilisation of spacecraft equipment are dry
heat and H2O2. These procedures could have a negative
effect on heat-sensitive materials [2]. Cold atmospheric
plasma (CAP) technology can provide a very fast and
effective inactivation of various kinds of microorganisms,
like bacteria and endospores, at low temperatures. In the
first study, we could show that CAP technology is a very
fast and promising alternative to inactivate different kinds
of microorganisms on surfaces. [3].
Aims
In this follow-on study, we aim to reach a high applica-
tion level for the sterilisation of space equipment using
CAP. It is necessary to find proper CAP conditions for a
maximal sporicidal effect and a minimal influence on the
treated materials. Additionally, we plan to investigate a
relation between the plasma production and the treatment
volume for the sterilization of lager space equipment.
Methods
For the aims mentioned above, we redesigned the experi-
mental setup, as shown in Figure 1. Here the plasma gas
generated in a plasma source is transported in a treatment
chamber by a gas flow, where the samples are placed. The
plasma gas is further transported back to the plasma source
through a humidifier. Since it takes time to transport the
plasma gas from the plasma source to the treatment cham-
ber only long living species reach the samples.
For the first test, we treated 2.6 ∗ 106 Bacillus atrophaeus
spores on stainless steel disks which are often used as a
standard bioindicator to test sterilisation methods [2]. The
relative humidity was kept close to 99%. For the estima-
tion of sporicidal effect, our detection limit is a 6-log re-
duction by using filtration.
Results
The first experiments showed a higher sporicidal effect
than described in [3]. The results of Shimizu et al. showed
a 3-4 log reduction with a treatment time of 90 min. In the
redesigned setup, a 6-log reduction was achieved in 10
min. Our new treatment provides a D-value of 1.62 min
for Bacillus atrophaeus. This D-value is equivalent to that
by dry heat at a minimal temperature of 150 °C [4].
Conclusions
The newly proposed setup can provide an efficient decon-
tamination on sensible materials of spacecraft facilities. A
further study will be carried out to increase the treatment
volume for treatments of larger components. Moreover,
the possible damage on the treated materials by the CAP
system will be tested.
Figure 1: Sketch of plasma system in this study. The produced plasma gas is cycled among the plasma source, treatment cham-
ber and humidifier by gas flow.
References
[1] Hofmann M, Rettberg P, Williamson M, 2010 Pro-
tecting the Environment of Celestial Bodies 38th
COSPAR Scientific Assembly
[2] Klaempfl T G, 2012 Cold Atmospheric Air Plasma
Sterilization against Spores and Other Microorgan-
isms of Clinical Interest Applied and Environmental
Microbiology 825077-5082
[3] Shimizu S, 2014 Cold atmospheric plasma – A new
technology for spacecraft component decontamina-
tion Planetary Space Science 90 60-71
[4] Kempf M J, 2009 Determination of Lethality Rate
Constants and D-Values for Bacillus atrophaeus
(ATCC 9372) Spores Exposed to Dry Heat from
115°C to 170°C Astrobiology 8 1169-1182
HTPP14 Munich: Session 3, Poster S3-6
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HTPP14 Munich: Session 3, Poster S3-7
23
Numerical modelling of an electric arc and its interaction with the
anode M Lisnyak
1*, M Chnani
2, A Gautier
2, J-M Bauchire
1
1 GREMI, UMR 7344, CNRS/Université d’Orléans, 14 Rue d'Issoudun, Orléans, 45067, France
2 Zodiac Aero Electric, Zodiac Aerospace, 7, rue des Longs Quartiers, 93108, France
Introduction
Electric arcs have been studied for many decades by the
scientific and engineering communities due to their wide-
spread applications. The arc column plasma has been in-
vestigated theoretically by many authors and its modelling
is now well-established [1].
Electric arc is taking part in many industrial applications,
for most of them interaction between plasma and anode
plays a significant role.
The interest of the present study is to establish a numerical
model of interaction between the arc column described in
local thermodynamic equilibrium (LTE) and the solid an-
ode and to make it accessible through the use of the com-
mercial software COMSOL Multiphysics®.
Arc column model
In most of the cases, the plasma in the arc column is de-
scribed using LTE approximation with one temperature.
Hence, the arc column can be reasonably modelled with a
magneto-hydrodynamic (MHD) approach [2]. This
re-quires thermodynamic properties and transport coeffi-
cients of the LTE plasma as well as radiative losses which
are presented in for different pressures and gases.
The MHD model is solved numerically for an arc in argon
at atmospheric pressure and an electric current of 200 A.
The geometrical configuration and the boundary condi-
tions are the same as in [3].
Plasma-anode interaction
The plasma-anode interaction can be established by in-
troducing the energy balance between the plasma and the
anode, and at the same time current conservation between
plasma and anode has to be valid.
In this work, mathematical investigations have been made
in order to establish the energy transfer between the LTE
plasma and the solid anode, excluding the anode sheath
simulations. Thus, the flux from the plasma to the anode
is:
where 𝑗 is the current density, 𝑇𝛿 is the plasma tempera-
ture at the interface between the LTE plasma and the an-
ode sheath, 𝐴𝑓 is a work function of the anode material, 𝑘
is the Boltzmann constant, 𝑒 is the elementary charge, 𝜑𝑎
potential fall in the anode layer, for the present case 𝜑𝑎 ≤
0𝑉, and 𝑊𝑟𝑎𝑑 is the radiation losses in the layer.
Results
Numerical simulation of a free burning arc in 2D and 3D
configurations has been solved using COMSOL Mul-
tiphysics® software. The model of the arc column and the
solid anode has been solved independently and matched at
the interface by introducing the flux according to (1).
The temperature distribution in the arc column and the
anode are presented in figure 1. The computed tempera-
ture distribution has a well-known bell shape, and the
maximum of the temperature is on the axis around 0.7 mm
from the cathode tip. Due to the energy transfer between
the arc and the anode, temperature of the later increases
and achieves T = 1130 K on the anode axis.
Figure 1: Temperature distribution in the arc and in the anode. Isotherm
in the plasma 11 kK. Vectors: velocity field.
In conclusion, the present work attempts to establish a
method to include the plasma-anode interaction in numer-
ical simulations of LTE arc column. A rather simple ap-
proach to introduce the energy and the current conserva-
tion between two medias allows estimating the anode
heating. One of the advantages of such approach is that it
can be applied for more sophisticated anode shapes.
References
[1] Gleizes A, Gonzalez J J, Freton P, 2005 Thermal
plasma modelling J. Phys. Appl. Phys., Vol. 38, No.
9, R153
[2] Mitchner M, Kruger C H, 1973 Partially ionized
gases. New York: Wiley
[3] Hsu K C, Etemadi K, Pfender E, 1983 Study of the-
free‐burning high‐intensity argon arc, J. Appl.
Phys.,Vol. 54, No. 3, 1293–1301
HTPP14 Munich: Session 3, Poster S3-7
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HTPP14 Munich: Session 3, Poster S3-8
25
Modelling of the Temperature Distribution Inside a Sprayed
Particle in Air Plasma Spraying K Bobzin
1, M Öte
1, M A Knoch
1, I Alkhasli
1 *, U Reisgen2, O Mokrov
2, O Lisnyi2
1 RWTH Aachen University, IOT - Surface Engineering Institute, Kackertstr. 15, 52072 Aachen, Germany 2 RWTH Aachen University, ISF – Welding and Joining Institute, Pontstr. 49, 52062 Aachen, Germany
General
Plasma spraying is a coating process which is widely used
for the application of thermal barrier coatings. High plas-
ma jet temperatures allow the processing of ceramic mate-
rial particles which characteristically exhibit low thermal
conductivities [1]. This, in turn, produces high tempera-
ture gradients inside the particles and vaporization on the
particles’ surface during their dwell time in plasma jet. In
other words, a single particle in the plasma-jet can exhibit
3 states of matter simultaneously: solid in the core, molten
exterior and boiling on the surface. The temperature dis-
tribution inside the particles is the foremost factor which
influences the particle’s behaviour during its impact on the
substrate surface. Experimental investigations can provide
only the surface temperature of the particles [2], which is
not a good indicator of the molten status for ceramic par-
ticles [3]. This study focuses on the determination of the
temperature distributions inside the particles during their
flight in the plasma and the free jet with the help of simu-
lations (Figure 1).
Figure 1: Temperature distribution and trajectories of the particles in
the plasma and the free jet.
Approach
For this purpose, a mathematical model of the plasma
spraying process that describes the plasma and the free jet
loaded with sprayed particles was developed. The model
includes two sub-models; a sub-model of plasma jet flow
and a sub-model of sprayed particles (Figure 2). The first
sub-model calculates the kinetics of temperature and ve-
locity fields of turbulent plasma jets generated by the
plasma torch. This information is used in the second
sub-model to calculate the kinetics of temperature
distribution in the particles, their molten status and mass
losses due to evaporation. The second sub-model obtains
heat and mechanical impulse loses due to the parti-
cle-plasma interaction, which in turn is coupled with the
first sub-model, plasma jet flow. The calculated results are
compared with the lumped capacitance model as well as
with experimentally determined in-flight particle surface
temperatures.
Core Exterior
Figure 2: Temperature distribution inside a 100 µm diameter particle
during its free flight at different times.
Acknowledgements
All presented investigations were conducted in the context
of the Collaborative Research Centre SFB1120 "Precision
Melt Engineering” at RWTH Aachen University and
funded by the German Research Foundation (DFG). For
the sponsorship and the support we wish to express our
sincere gratitude.
References
[1] Bobzin K, 2013 Oberflächentechnik für den Maschie-
nenbau. Germany: Weinheim Wiley-VCH Verlag.
[2] Fauchais P, Vardelle M, 2010 Sensors in Spray Pro-
cesses. Journal of Thermal Spray Technology: 668–94
[3] Zhang W, 2008 Integration of Process Diagnostics and
Three Dimensional Simulations in Thermal Spraying;
Dissertation
HTPP14 Munich: Session 3, Poster S3-8
26
HTPP14 Munich: Session 3, Poster S3-9
27
Development of an AC-GMAW process for welding high-strength
fine grained steels M Bredack
1*, G Huismann
2, J Schein
1
1 Lab for Plasma Technology (LPT), Universität der Bundeswehr München, Munich
2 Lab for Welding Technology, Helmut-Schmidt-Universität, Hamburg
Introduction
High-strength fine grained steels are increasingly gaining
importance in economic and in constructive ways. In
comparison to conventional steels a reduction of the
weight by the same strength can be achieved, which lead
to significant cost savings, e.g. for crane manufacturers.
For the welding process of these temperature-sensitive
steels an accurate heat control in order to influence the
mechanical properties is essential. From an economic
point of view, the DC-GMAW process would be very
suitable for the processing of these steels due to its high
melting rate. The relatively rigid coupling of the deposi-
tion rate to the heat input into the base material is a sig-
nificant disadvantage. The heat input is often too high, so
that the desired strength and toughness values can only be
achieved through major economic and technological effort.
The goal is to vary the heat input into the base material
over wide ranges by using the AC-GMAW process, de-
pending on the ratio of positive to negative polarity (EN
content). The prospected benefit of higher EN content is
the reduced heat input into the base material. By doing so,
temperature sensitive high-strength fine grained steels
could be welded in a more economic and safer way. In the
context of this publication, the AC-GMAW process was
investigated and compared with an equivalent DC process.
Test setup
In order to investigate the AC-GMAW process for the
application of high-strength fine grained steels a free pro-
grammable welding machine by OTC type 300+ was used.
With this machine it is possible to obtain an EN content
up to 70%. The EN content is the ratio of the negative
current phase compared to the sum of the positive and
negative current phase over one period. In order to de-
scribe the characteristics of the AC-GMAW process a se-
ries of investigations has been conducted and compared to
an equivalent DC-GMAW process. The effect of different
EN-contents on the process were examined by calorimet-
ric measurements with an inclined calorimeter as well as
mircosections of the weld.
The heat input into the base material can be determined by
using the inclined calorimeter. Also the efficiency of dif-
ferent EN-contents of the AC-GMAW and the DC-Process
are compared to each other. For this purpose a metal sam-
ple is stored in a pool with a water quantity of 20 kg at an
angle of 4° to the horizontal. The welding torch, which is
mounted on a linear unit, moves parallel to the metal sam-
ple during the welding process. The water basin is lifted in
the vertical direction synchronously to the speed of the
welding torch. This ensures that the water front stays right
behind the arc and thus the water is able to take up the
resulting heat input into the base material by the welding
process. By measuring the water temperature using ther-
mocouples before and after the welding process, the heat
input into the base material can be determined.
Results
Current and voltage measurements of the process have
shown that by increasing the EN content only a relatively
small decrease (~10 %) of the process current as well as
the process power and thus the heat input could be inves-
tigated. The microsections have shown that when increas-
ing the EN content from 20 % to max. 70 % the penetra-
tion is declining and the weldseam narrows and overarch-
es. A possible assumption is that by varying the EN con-
tent the energy-flow between the electrodes is being
changed, which might lead to the shape of the weldseam
as mentioned above.
Measurements conducted with the inclining calorimeter
underpin that the heat input into the base material of the
AC- and the DC-GMAW process is almost in the same
region. An explanation for this could be the relatively small
decrease of the process power with increasing EN-content
as mentioned above.
Conclusion
The aim of subsequent investigations is to find out why
the theoretical considerations are not consistent with the
practice in line. In specific, the relatively small decrease
of the process power with increasing EN-content of the
AC-GMAW compared to DC-GMAW process and the
rather slight change in the heat input into the base material
should be examined further. Furthermore other diagnostics
will be used to fully describe the AC-GMAW process e.g.
Fume-Box measurements, where the flue gas emssions of
the welding process can be determined and high-speed
stereo-optics to reconstruct plasma radiation, wire and
droplet geometry. The exact influence of the AC-GMAW
process behavior remains to be explored in future work.
Acknowledgements
The presented results derive from the IGF-project “De-
velopment of an AC-GMAW process for welding
high-strength fine grained steels” (funding number 18.458
B). The project, coordinated by the Research Association
on Welding and Allied Processes of the DVS, is funded by
the Federal Ministry of Economic Affairs and Energy
(BMWi) on basis of a decision by the German Bundestag
as part of the AiF Industrial Collective Research (IGF)
program.
HTPP14 Munich: Session 3, Poster S3-9
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HTPP14 Munich: Session 3, Poster S3-10
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Numerical analysis of RF thermal plasma for the preparation of
metal boride nanoparticles embedded soft radiation shielding ma-
terial J-H Oh
1, S Gwon
2, J-Y Sun
2, S Choi
1,*
1Department of Nuclear and Energy Engineering, Jeju National University, Jeju, Republic of Korea
2Department of Materials Science and Engineering, Seoul National University, Seoul, Republic of Korea
Abstract
Ratio Frequency (RF) thermal plasma can synthesize na-
noparticles with a high purity, because it generates the
thermal plasma of high temperature without the pollution
of impurities by electrode erosion. In addition, any kind
of raw material can be used in RF thermal plasma due to a
high temperature over 10.000 K. The rapid temperature
gradient of thermal plasma, however, causes a difficulty
to find out an appropriate condition for nanoparticles
synthesis [1]. Therefore, numerical simulation was con-
ducted for RF thermal plasma in this study. Since boron
has high melting and boiling points, numerical analysis
was carried out to find a high temperature condition in
different operating and design conditions. Figure 1 shows
the computational domain and variables for RF thermal
plasma used in this study. From the numerical analysis, it
was confirmed that the high temperature region is en-
larged along with the central part of the plasma torch by
increasing the flow rate of sheath gas. At the torch exit,
the high temperature region is expanded in radial direc-
tion by increasing the number of coil turns and by de-
creasing the flow rate of sheath gas as shown in Figure 2.
In the present work, the target material is metal boride
nanoparticles. Boron is effective to absorb the neutron
and it is used as a control rod in nuclear plants. Metal
with a high atomic number and a high density can de-
grades γ-ray. Therefore, metal boride is a promising mate-
rial for radiation shielding. Synthesized metal boride can
be embedded in a soft material. As shown in Figure 3 (a),
metal boride nanoparticles can be embedded in a hydrogel
with a high density. It is because the coherence of alginate
and acrylamide are reduced when a large amount of mi-
cro-size particles are contained [2]. As a preliminary study,
micro sized metal oxides were used to evaluate the radia-
tion shielding characteristics of hydrogels including dif-
ferent metal oxide particles. The hydrogel with lead oxide
particle shows the highest attenuation coefficient of 0.296
cm-1
.
Acknowledgements
This research was funded by Nuclear Research Base Ex-
panding Program through the National Research Founda-
tion of Republic of Korea (No. NRF-
2015M2B2A9030393).
References
[1] Watanabe T, Nucleation mechanism of boride nano-
particles in induction thermal plasmas Trans. Ma-
ter.Res. Soc.Jpn. 29 3407
[2] Sun J, Highly stretchable and tough hydrogel Nature
480 133
Figure 1: Computational domain and variables for the numerical sim-
ulation of RF thermal plasma.
(a) (b) Figure 2: Radial temperature profiles at the torch exit according to
(a) the number of coil turns and (b) the flow rate of sheath gas.
(a) (b)
Figure 3: (a) Concept of soft radiation shielding and (b) measured
attenuation coefficients for hydrogel with different metal oxide micro-
particles.
HTPP14 Munich: Session 3, Poster S3-10
30
HTPP14 Munich: Session 3, Poster S3-11
31
Electrical arc movement and commutation modelling in the
Low-Voltage Circuit Breaker J Quéméneur
1*, P Freton
1, J J Gonzalez
1, M Masquère
1, P Joyeux
2
1 Université Toulouse III UPS; LAPLACE (UMR 5213); 118, route de Narbonne, 31 062 Toulouse cedex 9, France
2 Hager Electro SAS, 132, boulevard d’Europe, BP3, 67 210 Obernai, France
Introduction
Numerical simulation of the electrical arc behaviour in
the Low-Voltage Circuit Breaker (LVCB) is a powerful
tool for the development of new industrial products. It
allows analysing physical quantities that are not easily
reachable by experimental way while jointly reducing the
need for long and expensive prototype testing. Anyway
arcs in this situation prove to be difficult to model since
many phenomena are involved such as walls ablation,
sheath physics, electromagnetics or fluid dynamics. The
work presented here constitutes a contribution toward a
complete model of the arc in LVCB.
Numerical model
The proposed approach is a magneto-hydrodynamic
model of the electrical arc using Finite Volume Method
based on previous work of our team [1]. Conservation of
energy, momentum, mass, scalar and vector potentials are
solved using the generalised form of the conservation
equation:
Since electrical arcs are subject to a wide variation of
temperature and pressure, the thermodynamic properties
such as the density ρ and the various diffusion coeffi-
cients ΓΦ (as the thermal conductivity) have to be calcu-
lated using real gas model. Also radiative transport of
energy is taken into account with the net emission coeffi-
cient source term.
Hypotheses
Several assumptions have to be made:
- The medium is air plasma in local thermodynamic equi-
librium, which is a correct assumption for the arc core but
reveals inexact for the plasma sheaths and the cold areas;
- This plasma is a laminar Newtonian fluid;
- The effect of gravity is neglected;
- The magnetic behaviour is assumed to be static;
- The initial stages of the arc ignition are not described;
- Arc root movement is driven by the arc column and not
by the electrode physics, this assumption will lead to two
different methods of modelling arc root which will be
explained now.
Global Current Resolution Method (GCRM)
This first method to describe the arc root movement as-
sumes that electric potential and energy between the
plasma and the electrodes can be described only by
con-duction phenomenon. This strong hypothesis, which
neglects most of the sheath phenomena, yet permits an
auto-determined motion of the arc root on the electrode
surface.
Mean Electrical Conductivity Method (MECM)
In this second method, based on the work of Swierczyn-
ski & al. [2], arc root position is imposed on the electrode
where the surrounding gas presents the highest electrical
conductivity. In order to represent correctly the arc com-
mutation or restrikes phenomena, improvements have to
be made. Indeed, experimental evidences show that there
are at least two arcs in parallel when those events occur.
Therefore, this method is now able to set two arc roots on
one electrode by detecting the two highest maxima of the
mean electrical conductivity along the arc runner. The
total current is then distributed between the two arc roots
weighted by the value of the local mean electrical con-
ductivity.
Magnetic boundary conditions
Magnetic field is only calculated for the fluid domain of
the geometry. Therefore, it must be precisely calculated at
the boundaries since they can be close to the arc. We use
the Biot & Savart equation to determine the value of the
vector potential [3]. Since it also takes into account the
current inside the arc runners the external magnetic field
can be modelled.
Proposed results
This model will be applied for several geometries. Sim-
plified ones with rectangular box shape or real industrial
LVCB geometries. The physical quantities and electrical
values calculated will be compared with experiments.
References
[1] Gleizes A et al., 2005 Thermal Plasma Modelling J.
Phys. D: Appl. Phys. 38
[2] Swierczynski B et al., 2004 Advances in low-voltage
circuit breaker modelling J. Phys. D: Appl. Phys. 37
[3] Freton P et al., 2011 Magnetic field approaches in dc
thermal plasma modelling J. Phys. D: Appl. Phys. 4
HTPP14 Munich: Session 3, Poster S3-11
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HTPP14 Munich: Session 3, Poster S3-12
33
Experimental investigations on arc movement and commutation in
the Low-Voltage Circuit Breaker J Quéméneur
1*, M Masquère
1, P Freton
1, J J Gonzalez
1, P Joyeux
2
1 Université Toulouse III UPS; LAPLACE (UMR 5213); 118, route de Narbonne, 31 062 Toulouse cedex 9, France
2 Hager Electro SAS, 132, boulevard d’Europe, BP3, 67 210 Obernai, France
Introduction
Industrial Low-Voltage Circuit Breakers (LVCB) are very
sophisticated products where complicated design have
been inherited from decades of empirical developments.
Nowadays, with the appearance on the market of competi-
tive LVCB from the newly industrialized countries, there
is a growing need for innovative products with different
geometries or materials. Those improvements require a
better understanding of the arc behaviour. But since LVCB
arc chambers are much complex, interpretation of the ex-
perimental results is still difficult.
Therefore, we decided to realize experiments in a simpli-
fied configuration with geometric parameters that can be
easily modified. Our experimental set-up serves two pur-
poses: conducting a wide range of parametric studies and
comparing with multi-physic simulations [1].
Experimental set-up
The simplified arc chamber used in this work is displayed
in Figure 1. Its width and height are 10 mm, and 22 mm
respectively. The length is adaptable thanks to the red
blocks, represented in Figure 1, which can slide on the arc
runners. There are also four 20 mm2
openings (two on
each red block) allowing the hot gas to flow out of the
device. On the back of the chamber, along the arc runners,
there are eight locations where pressure measurements can
be performed. The front wall is transparent in order to
allow high-speed imaging of the arc.
Figure 1: View of the simplified arc chamber.
The (yellow) moving contact can be seen in the middle of
the chamber in Figure 1. It is triggered by a mechanism
allowing the contact opening at a specified time and at a
controlled speed between 2 and 8 m/s. It is synchronised
with a 50 Hz pulse current source so there is arc ignition
by contact opening at a given current.
Then, measures of pressure, images of the arc, arc voltage,
current in the moving contact and total current are ac-
quired. Measuring those two currents is helpful to analyse
arc commutation from the moving contact to the upper arc
runner.
Experimental results analysis
Breaking arcs in LVCB are subject to great variability.
Therefore it is better to conduct statistical analysis on a
large sample of tests before concluding on the parameters
importance. Consequently, we automated the treatment of
the experimental results by developing a software capable
of determining several data as the times of arc ignition, arc
commutation and arc extinction, the occurrence of re-
strikes and calculating the average, maxima, minima and
standard deviation of the physical quantities measured.
Meanwhile, for the analysis of the pictures taken by the
high-speed camera, an algorithm was developed in order
to determine the positions of the arc and its two roots ac-
cording to the light intensity of each pixel. For this pur-
pose we used a weighted mean like previously defined by
McBride & al. [2]. The pictures are also edited as seen in
Figure 2.
Figure 2: Example of edited picture with the red box being the size of the
chamber, the blue and red curves being the voltage and current.
Proposed results
With this experimental set-up we are able to perform
many parametric studies showing arc voltage, current,
imaging of the arc and pressure monitoring inside the
chamber. Comparisons with our numerical model will also
be proposed.
References
[1] Quéméneur J & al., 2015 Cathode Arc Root Move-
ment: Models Comparison Plasma. Phys. Technol. 2
[2] McBride J W & al., 1998 Arc Root Mobility During
Contact Opening at High Current IEEE Trans.
Comp. Packag. Manufact. Technol. 21
HTPP14 Munich: Session 3, Poster S3-12
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HTPP14 Munich: Session 3, Poster S3-13
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Diode-rectified multiphase ac arc with bipolar electrodes for deg-
radation of electrode erosion M Tanaka
1*, T Matsuura
2, T Hashizume
1, T Watanabe
1
1 Dept. Chemical Engineering, Kyushu University,
2 Taso Arc Co. Ltd.
Abstract
A new method to generate a multiphase ac arc (MPA) with
diode rectification was proposed to solve electrode erosion
in MPA. MPA is expected to be utilized in massive powder
processing as novel heat source because MPA possesses
many advantages; high energy efficiency, large plasma
volume, low gas velocity. However, a few issues remain to
be solved before MPA become a reliable heat source in
industrial fields. Erosion of tungsten based electrode is one
of the important issues to be solved. Electrode erosion
mechanism has been investigated based on high-speed
visualization. Erosion due to larger droplet ejection than
100 μm in diameter is dominant at cathodic period while
evaporation at anodic period is dominant mechanism. The
droplet ejection at cathodic period is basically caused by
the electrode melting due to high heat flux to electrode at
anodic period. Therefore, to separate the electrode into a
pair of cathode and anode can be a solution of electrode
erosion issue. Then, rectifier diodes are focused to rectify
ac currents. The purpose of the present study is to fabricate
the diode-rectified multiphase ac arc (DRMPA). Another
purpose is to investigate erosion mechanism of electrodes.
Schematic of electric circuits are shown in Figure 1. Mul-
ti-diodes are placed between the electrodes and the trans-
former. Thus, the electrodes can be divided into pairs of
cathode and anode, namely bipolar electrodes. Figure 2
shows the schematic of the electrode configuration. Each
electrode consists of cathode made of indirect wa-
ter-cooled 2wt%-ThO2 W rod with 3.2 mm in diameter and
anode made of water-cooled Cu rod with 20 mm in diam-
eter. 6 pairs of electrodes are symmetrically arranged at the
angles of 60 deg. Odd numbered cathodes are placed
above the corresponding anodes, while even numbered
anodes are placed above the cathodes. DRMPA were gen-
erated among these parallel rod electrodes in argon at-
mosphere. Electrode phenomena and arc behaviours were
visualized by high-speed camera. Electrode erosion rate
was measured by weight difference between before and
after arcing for 20 min.
High-speed snapshots of electrode No.1 region in DRMPA
are shown in Figure 3(a). Corresponding arc current is also
shown in Figure 3(b). Stable arc re-ignition was con-
formed even after the half period break during anodic pe-
riod. This is due to existence of multi-arcs around the elec-
trode, resulting in easier arc re-ignition.
Electrode erosion rates are summarized in Table 1. The
erosion rate in DRMPA was successfully reduced to one
third of that in MPA. This result can be explained by the
negligible larger droplet ejection. The cathode melting and
droplet ejection were not confirmed according to the
high-speed observations. Measured temperature also found
that the cathode temperature was less than melting point of
tungsten. The proposed technique to generate DRMPA
enables us to utilize MPA in industrial fields.
Figure 1: Schematic of multiphase ac circuit; (a) conventional MPA
with 6 transformers, (b) DRMPA with 6 transformers and 12 diodes.
Figure 2: Top view of electrode region for DRMPA (a) and cross
sectional side view showing the plasma torches No. 1 and 4 (b).
Figure 3: High-speed snapshots of electrode No. 1 in DRMPA (a)
and corresponding arc current waveform (b).
Table 1: Comparison of electrode erosion rates for MPA and
DRMPA.
Acknowledgements This work was supported by JSPS KAKENHI Grant
Number 15K18265
HTPP14 Munich: Session 3, Poster S3-13
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HTPP14 Munich: Session 3, Poster S3-14
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Selective synthesis of anatase and rutile TiO2 nanoparticles by DC
thermal plasma H Jeong, T-H Kim, D-W Park
*
Department of Chemistry and Chemical Engineering and Regional Innovation Center for Environmental Technology of
Thermal Plasma (RIC-ETTP ), Inha University, Incheon, Republic of Korea
Titanium dioxide (TiO2) has been widely used and many
researches have been performed to investigate the charac-
teristics according to their phases, morphologies, sizes, etc
[1]. There are three phases such as the anatase, the rutile,
the brookite structures. Among them, the anatase and the
rutile phases TiO2 are mainly used in wide application for
industry [2]. The anastase phase is the metastable phase
and has advantages such as the large surface area for cat-
alytic active sites and wider band gap (3.2 eV) than rutile
phase (3.0 eV). Therefore, it has been used usually as
photocatalysts [3]. On the contrary, the rutile phase is
thermodynamically stable. It has been used for pigments
and cosmetics because of the higher refractive index and
is promising for an ink of electronic paper and DSSCs due
to its brilliant whiteness [4]. Therefore, it is anticipated
that the rutile will be used more effectively in the future.
The characteristics and applications fields of TiO2 pow-
ders are different according to their phases; therefore, the
selective synthesis technique of the anatase or the rutile
TiO2 powders would be important. Selective synthesis of
anatase and rutile phases TiO2 nanopowders was carried
out by using the DC thermal plasma as shown in Figure 1.
Titanium chloride (TiCl4) was used as a raw material for
synthesis of TiO2 nanopowders. TiCl4 was vaporized for
injecting by a vaporizer in Figure 1. Vaporized precursor
was injected into the thermal plasma jet with nitrogen (N2)
carrier gas. TiCl4 was oxidized with an additional air reac-
tive gas. As-synthesized powders were collected as spher-
ical nano-sized TiO2. Three variables were investigated to
control the phase ration of the anatase and rutile TiO2 na-
nopowders as adjust the temperature inside of the reaction
tube. The variables were established as the flow rate of the
air reactive gas, the input power and the reaction tube di-
mensions. The ratio of the anatase TiO2 nanopowders grew
as increasing the flow rate of the air gas due to decreasing
of the temperature inside of the reaction tube. The ratio of
the rutile TiO2 nanopowders was raised as increasing the
input power resulting in the higher temperature region.
Comparing with the above results, the phase ratio was
significantly changed by using different types of the reac-
tion tubes which had different inner diameter and material.
The narrower inner diameter was superior to obtain the
high rutile phase ratio. Moreover, the graphite inner tube
was the appropriate materials to achieve the high ratio of
rutile TiO2 nanopowders by increasing the temperature
inside of the reaction tube. It was revealed that the phase
ratio of TiO2 nanopowders was effectively controlled by
varying the process conditions.
Figure 1: The schematic diagram of the DC arc plasma system for syn-
thesis TiO2 (a) power supply (b) reaction tube (c) chamber (d) band
heater (e) vaporizer (f) scrubber.
Acknowledgements
This research was supported by Basic Science Research
Program through the National Research Foundation of
Korea (NRF) funded by the Ministry of Education (Grant
number: 2015R1A4A1042434).
References
[1] Hanaor D A H, Sorrell C C 2011 Review of the anatase
to rutile phase transformation J Mater. Sci.46855
[2] Oh S M, Li J G, Ishigaki T, 2005 Nanocrystalline TiO2
powders synthesized by in-flight oxidation of TiN in
thermal plasma: Mechanisms of phase selection and
particle morphology evolution J. Mater. Res. 20 (2)
529
[3] Sun J, Gao L, Zhang Q, 2003 Synthesizing and Com-
paring the Photocatalytic Properties of High Surface
Area Rutile and Anatase Titania Nanoparticles J. Am.
Ceram. Soc. 86 (10) 1677
[4] Popov A P, Priezzhev A V, Lademann J, Myllylä R,
2005 TiO2 nanoparticles as an effective UV-B radia-
tion skin-protective compound in sunscreens J. Phys.
D: Appl. Phys. 38 2564
HTPP14 Munich: Session 3, Poster S3-14
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HTPP14 Munich: Session 3, Poster S3-15
39
Simple model of current transfer to rod anodes of dc and ac
high-pressure arc discharges M D Cunha and M S Benilov
*
Departamento de Física, FCEE, Universidade da Madeira, Largo do Município, 9000 Funchal, Portugal
Instituto de Plasmas e Fusão Nuclear, IST, Universidade de Lisboa, Portugal
*[email protected] A number of different models more or less complex, de-
scribing the plasma-cathode interaction in high-pressure
arc discharges can be found in the literature (e.g., [1] and
references therein). On the other hand, only complex
models describing the plasma-anode interaction can be
found (e.g., [2]).
A simple model of plasma-anode interaction high-pressure
arc discharges is proposed in this work. The model ex-
ploits the two following features of current transfer to
anodes of high-pressure arc discharges. First, it has been
established experimentally and theoretically that the anode
power input is governed primarily by, and is approxi-
mately proportional to, the arc current; e.g., [3] and [4].
Second, the thermal regime of thin rod electrodes of arc
discharges is not significantly affected by the way as the
current is collected at the electrode surface if the electrode
operates in the diffuse mode.
In this work the plasma-cathode interaction is described in
the framework of the model of nonlinear surface heating
(e.g., [1]) and the plasma-anode interaction is implement-
ed in such a way that the energy flux from the plasma to
the anode was defined as the product of the current densi-
ty by the anode heating voltage; the density of electric
current is defined by the ratio of the arc current to the area
of the front surface of the anode where the current is as-
sumed to be collected. The model has only one empirical
parameter, the anode fall.
A number of numerical simulations have been performed,
with the above-described simple model of plasma-anode
interaction, for experimental conditions [3], [4] and [5],
and a good agreement between modelling and experiments
was obtained. As an example, we present in Figure 1 the
temporal evolution of the electrode sheath voltage and
electrode temperature of a rod electrode (with a diameter
of 1 mm and a length of 20 mm) operating with a
switched dc current of amplitude 1.41 A and frequency
50 Hz, operating in an argon plasma under the pressure of
2.6 bar [5]. From Figure 1, one can see the formation of a
sharp peak of electrode sheath voltage of approximately
180 V after current zero crossing, with a decreasing during
the rest of the half-cycle. The electrode operates in the
spot mode during the cathodic half-cycle. During the sub-
sequent anodic half-cycle, there is a decrease of the elec-
trode temperature and the electrode operates in the diffuse
mode. The decrease of the electrode sheath voltage is re-
lated with the increase of the electrode temperature during
the cathodic phase.
Figure 1: Temporal evolution of electrode sheath voltage (ESV) and
maximum temperature of a tungsten rod electrode of a switched dc cur-
rent. Dashed and dotted lines: modelling. Solid line: experiment [5].
The simple model used in this work to describe the plas-
ma-anode interaction is able to reproduce a variety of
phenomena and one can hope that the present approach
can provide a useful guide to experimentalists.
Acknowledgements
The work was supported by FCT - Fundação para a Ciên-
ciae a Tecnologia of Portugal through the project
Pest-OE/UID/FIS/50010/2013.
References
[1] Benilov M S, 2008 J. Phys. D: Appl. Phys.41 144001
[2] Trelles, J P 2013 Plasma Sources Sci. Technol. 22
025017
[3] Redwitz, M et al 2006 J. Phys. D: Appl. Phys.392160
[4] Almeida, N A et al 2009 J. Phys. D: Appl. Phys. 42
045210
[5] Langenscheidt, O et al 2007 J. Phys. D: Appl. Phys.
40 415
HTPP14 Munich: Session 3, Poster S3-15
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HTPP14 Munich: Session 3, Poster S3-16
41
Plasma actuators for flow control
M Kühn1*
, M Kühn-Kauffeldt1, J Schein
1, A Belinger
2
1 Laboratory for Plasma Technology, Universität der Bundeswehr München
2 LAPLACE, Université de Toulouse, CNRS, INPT, UPS, France
Introduction
Nowadays strict laws against air pollution require more
efficient aircrafts in order to fulfil environment protection
regulations. This can be achieved by introducing actuators
on the wing surface, which are able to improve the flow
induced drag and hence lower the overall energy con-
sumption. Various passive and active mechanical systems
have been developed for this purpose.
Besides mechanical actuators electrically driven plasma
actuators can also induce flow perturbations. Their main
advantage is that the strength and the frequency of pertur-
bation can be electrically controlled, introducing a flexible
system, applicable for a whole variety of problems. They
either can be used as a tool for investigation turbulent in-
stabilities or as a system which is able to react to big range
of instabilities. In the last decade, different types of plas-
ma actuators for various flow control applications have
been developed and investigated [1].
Low pressure turbines (LPT) is one of the applications for
which flow control can improve the overall performance
by influencing the flow induced drag and flow separation.
In a LPT the energy loss is induced by Tollmi-
en-Schlichting waves (TSW), which break up the laminar
flow and create high frequency turbulences at high aero-
dynamic loads [1]. Active flow actuators in the TWS evo-
lution zone can keep the flow more stable and reduce the
drag significantly [2]. Flow simulations have shown, that
perturbations induced at frequencies up to 37 kHz can
extinguish TSW and thus delay the stall [3, 4].
In this work, a plasma actuator is developed for experi-
mental studies of TWS extension and verification of the
simulation results.
Figure 1: Schematic of the power circuit andh the plasma actuator.
Experimental Setup
In order to implement a plasma actuator in the desired
frequency and power range a high voltage, high frequency
discharge was suggested. In the design presented in this
work the discharge is ignited between several electrodes,
which are positioned in a row on an insulating carrier
plate (Figure 1). The power supply unit consists of a sim-
plified high voltage fly-back transformer circuit together
with an external pulse generator. It provides an average
discharge voltage in the range of 1 to 3 kV with an ad-
justable frequency of up to 20 kHz.
The actuator was operated at a pressure form 50 to
100 mbar in order to simulate pressure conditions in the
LPT. At this pressure the electrodes work around the
Paschen minimum for air. Thus, the breakdown voltage is
significantly reduced. In this manner, a discharge along
the electrodes could be ignited, which is desired for the
flow dynamic measurements.
Voltage and current measurement along with high speed
imaging and plasma spectroscopy were used to character-
ise the evolving plasma. Scanning electron microscopy
was used to evaluate the actuator surface after the opera-
tion. First results demonstrate that this setup is able to
produce a stable pulsed discharge along the electrodes.
However further development of the power supply unit for
long term application is necessary
Acknowledgements
This work was supported by Laboratory for Plasma
Technology, Universität der Bundeswehr München.
References
[1] Goldin N, 2013, Widerstandsreduktion durch laminare
Strömungskontrolle – Direkte und bionische Verfah-
ren, PhD Thesis Technische Universität Berlin
[2] Herbert T, 1988 Secondary instability of boundary
layers. Annual Review of Fluid Mechanics 20 (1),
487-526
[3] Niehuis R, Mack M, 2015 Active Boundary Layer
Control with Fluidic Oscillators on Highly-Loaded
Turbine Airfoils. In Active Flow and Combustion Con-
trol 2014, pp. 3-22, Springer International Publishing
[4] Cossu C et al, 2002 Stabilization of Tollmi-
en-Schlichting waves by finite amplitude optimal
streaks in the Blasius boundary layer, Physics of fluids
14, L57
++HV
electrodes
-
GND
carrier plate
HV-Transformer
HTPP14 Munich: Session 3, Poster S3-16
42
HTPP14 Munich: Session 3, Poster S3-17
43
Synthesis and characterisation of carbon nanostructures substitut-
ed with boron and/or nitrogen using electric arc plasma D E Gourari
1, M Razafinimanana
1, M Monthioux
2, S Joulié
2, R Arenal
3, F Valensi
1
1 LAPLACE (Laboratoire Plasma et Conversion d’Energie), CNRS-INPT-Université Toulouse III, 118 Route de Narbonne,
31062 Toulouse cedex 9, France 2 CEMES (Centre d'Elaboration des Matériaux et d'Etudes Structurales), CNRS-Université Toulouse III, 29 rue Jeanne
Marvig, F-31055 Toulouse Cedex 4, France 3Instituto de Nanociencia de Aragon (INA), Universidad de Zaragoza Calle Mariano Esquillor 50018 Zaragoza, Spain
General
Carbon based nanoparticles such as fullerenes, graphene
or nanotubes (CNTs) present outstanding properties.
However limitations appear when considering practical
applications. For instance the conductivity of CNTs is
determined by their geometry, which can vary from one
tube to another within the same batch. The partial substi-
tution of carbon atoms by other atoms such as boron or
nitrogen, leading to so-called heterogeneous CNTs is a
way to control the conductivity. Similarly, graphene elec-
tronic structure can be tuned by substitution with foreign
elements. The electric arc method allows synthesizing a
wide range of products thanks to its numerous tuneable
operation parameters. The main advantage is to perform
in-situ substitution which avoids the material degradation
usually encountered with two-step procedures. The work
reported here is dedicated to the synthesis of single-wall
CNTs substituted with boron and/or nitrogen. Graphene
nanoflakes were also obtained. The growth conditions are
analysed to get a better understanding of the involved
phenomena, in order to improve synthesis control. The
method is based on the analysis of product morphology
and structure in correlation with the study of plasma pa-
rameters, for various experimental conditions.
Synthesis Setup
The synthesis reactor is a cylindrical chamber with a
volume of 25 L. The electrodes are in a vertical configura-
tion. The plasma gas is helium or various nitrogen/helium
mixtures with initial pressure of 60 kPa. In order to limit
the pressure increase due to arc heating the experiment
duration is limited to 1 minute. The anodes are heteroge-
neous, i.e. they are prepared from drilling a coaxial 6 mm
diameter cavity in graphite rods which is subsequently
filled with graphite, catalysts, and boron powders to reach
the desired composition. The graphite grain size is 1 µm
and catalyst are nickel (0.6 at. %) and yttrium (0.6 or
1.2% at.%). Boron content ranges from 1 to 8 at. %. The
optimal conditions determined so far to get a reasonable
yield of substituted SWCNTs with limited impurity con-
tent correspond to a 80 A arc current, an anode doped with
4 at.% boron nitride, 0.6 at.% nickel and 0.6 at.% yttrium
and 1 mm electrode gap. During the synthesis the plasma
diagnostic is performed using optical emission spectros-
copy and the temperature of the gas surrounding the arc is
measured with thermocouples. This allows monitoring the
temperature of both the plasma and the zone where
SWCNTs form.
Products analysis
The carbon products collected after synthesis are analysed
using High Resolution Transmission Electron Microscopy
(HR-TEM). The chemical composition is studied using
Electron Energy Loss Spectroscopy (EELS) and X-Ray
photoelectron spectrometry (XPS).
Results
The presence of boron appeared to be an inhibitor to the
SWCNT growth, which was related to its cooling effect on
the plasma. However this could be compensated by in-
creasing the current and the yttrium content. Particular
attention was paid to the validation of the actual substitu-
tion, and results show the strongest evidences to date that
boron is indeed inserted in the graphene lattice of
SWCNTs. Boron-substituted graphene was also obtained
and results indicate that the graphene grew in the plasma
and was not just exfoliated from the anode. When com-
pared to SWCNTs, graphene growth needs a lower plasma
temperature and a weaker radial thermal gradient. The C2
concentration is also lower, which is compatible with the
carbon leaving the plasma through recombination, thus
forming the graphene flakes.
HTPP14 Munich: Session 3, Poster S3-17
44
HTPP14 Munich: Session 3, Poster S3-18
45
Synthesis of oxygen-free TiN compounds nanosized powders in
the DC plasma arc reactor A Samokhin, D Kirpichiev, N Alexeev, M Synaiskiy, Y Tsvetkov
A. A. Baikov Institute of Metallurgy and Materials Science, Russian Academy of Sciences (IMET RAS), Russia
Introduction
Titanium nitride possesses unique set of physicochemical
and physicomechanical characteristics. Plasma synthesis is
the most universal production method of the TiN na-
nopowders in the wide range of disperse and chemical
structures. In the paper results of thermodynamic calcula-
tion of the Ti –Cl–N– H system and results of experiments
on plasmochemical synthesis of the nanopowder TiN at
interaction of TiCl4 vapour with H2 – N2 – Ar arc plasma
are presented.
Thermodynamic analysis
Calculations of equilibrium composition and thermody-
namic properties of the TiCl4 – H2 – N2 system was exe-
cuted with use of the program TERRA complex at the fol-
lowing parameters: the interval of temperatures from
400 K to 4000 K, pressure is 0.1 MPa, a mole ratio of
N / Cl from 4 to 40, a mole ratio of N/Ti from 1 to 10.
It is calculated that TiN output values of 95 % are provid-
ed at H/Cl = 10, N/Ti ≥ 10 and temperature 1300 – 1400 K
(Figure 1). There is a TiN output decrease at temperature
exceeding 1400 K and at the same time in system there is
a formation of the lowest chlorides of the titan.
Figure 1: TiN output temperature dependence with ratio H/Cl=10
mole/mole and different mole ratio N/Ti calculation results.
TiN produce energy consumption is 16 – 20 MJ/kg de-
pending on excess of nitrogen (Figure 2).
Figure 2: TiN produce energy consumption temperature dependence
calculation results.
Maximum TiN output may be provided at H/Cl = 10 and
N/Ti ≥ 5 (process temperature – 1300 K) and enthalpy of
nitrogen-hydrogen plasma is about 1.5 MJ/nm3. This value
of an enthalpy can be easily reached and exceeded when
using of the existing designs of arc plasmatrons.
Experiment results and discussion Experimental setup consisted of DC arc 25 kW thermal
plasma generator, TiCl4 vaporizer, reactor and exhaust gas
utilization system. Vapor feeded with transport gas to
plasma jet through mixing chamber. Condensed reaction
product deposited on the reactor water cooled walls and
filter. Contained in exhaust gas chlorine was trapped with
alkaline solution scrubber. The produced powders were
analysed by the X-ray diffraction (XRD) analysis
(RIGAKU Ultima – 4), Specific Surface Area measure-
ments (Micromeritics TriStar 3000); particle morphology
(Helios 650 NanoLab); nitrogen content (LECO ТС-600).
Nitrogen content was in the range of 18 – 22 % in titanium
nitride produced nanopowders depending on process pa-
rameters. In accordance with Xray and SEM results TiN
powders represented by cubic nanoparticles ensembles
with particle sizes of 30 – 100 nm (Figure 3). The maxi-
mum TiN output was equal 94 % in experiments
Figure 3: TiN nanopowders produced X-ray and SEM results.
Change of plasma flow enthalpy in the range of
3.0-5.18 kWh/m3 allows to produce powders with mean
particle size in the range of 51-234 nm. Increase in con-
sumption of TiCl4 leads to growth of the particles size.
Acknowledgements
This work was supported of the Russian Ministry of Edu-
cation and Science (Federal Target Program «Research
and development on priority directions of scien-tific-technological complex of Russia for 2014 - 2020
years», project «Development of bases of plas-ma-chemical technologies for production of nanosized
powders of titanium anoxic compounds - nitride, carbide and carbonitride for developing of new structural and
functional materials», agreement № 14.607.21.0103,
unique code RFMEFI60714X0103).
HTPP14 Munich: Session 3, Poster S3-18
46
HTPP14 Munich
47
Tuesday
HTPP14 Munich
48
HTPP14 Munich: Session 4
49
Magnetron sputtering: From the historic roots to recent discoveries
of spoke and breathing modes A Anders
Lawrence Berkeley National Laboratory, Berkeley, California
Extended Abstract
Cathode disintegration, as sputtering was originally called,
has its humble beginnings in the 19th
century with discov-
eries related to generating and storing electrical energy
and inventions establishing “empty space”: vacuum. In the
1930s, Penning described the trapping of electrons in cer-
tain electric and magnetic field configurations, concepts
leading to the development of our modern magnetrons in
the 1970s (Chapin, Clarke, Penfold and Thornton). To
utilize plasma for both sputtering of targets and plasma
assistance to the deposition process, magnetic unbalancing
was developed in the 1980s. This step and the addition of
an auxiliary RF discharge can be seen as precursors to
high power impulse magnetron sputtering, HiPIMS, were
pulses of high power lead to the ionization of the sputtered
atoms. Still, more than a decade after the birth of HiP-
IMS, there are surprising features to be discovered, ex-
plained, and exploited, such as the recent (2012) observa-
tions of traveling ionization zones or spokes [1-3], which
have profound influence on magnetron operation and par-
ticle transport, like the creation of plasma flares (Figure
1).
Figure1: Shallow angle view on half of a 75 mm diameter aluminum
target in 0.5 Pa argon, 1 µs exposure time of the camera, taken near the
end of a 50 µs HiPIMS pulse, 200 A peak current. One can see ionization
zones (“spokes”) and a plasma flare.
In analogy to thrusters and other ExB discharges, there
have also observations of “breathing” [4]. With those de-
velopments come a host of new observations and explana-
tions. Even the well-accepted Thornton paradigm of elec-
tron heating via secondary electrons has been shown to be
incomplete. An new energy balance was developed by
Hou et al. [5] using a global discharge model. This model
can be extended to electron heating in spokes [6]. Heating
of electrons and self-organization are related: ionization is
amplified by locally heated electrons, and local heating
facilitates the formation of double layers and a potential
hump. Clearly, we have not completed the journey of
magnetron research.
Acknowledgements
Much of the recent research at LBNL on HiPIMS plasmas
was done by Y. Yang, X. Zhou, M. Panjan, and others,
whose contributions are gratefully acknowledged. Work at
LBNL was supported by the U.S. Department of Energy
under Contract No. DE-AC02-05CH11231.
References
[1] A Anders, P Ni, and A Rauch, 2012 Drifting localiza-
tion of ionization runaway: Unraveling the nature of
anomalous transport in high power impulse magne-
tron sputtering, J. Appl. Phys., Vol. 111, p. 053304
[2] A P Ehiasarian, A Hecimovic, T de los Arcos, R New,
V Schulz-von der Gathen, M Böke, et al., 2012 High
power impulse magnetron sputtering discharges: in-
stabilities and plasma self-organization, Appl. Phys.
Lett., Vol. 100, p. 114101
[3] A Kozyrev, N Sochugov, K Oskomov, A Zakharov,
and A Odivanova, 2011 Optical studies of plasma in-
homogeneities in a high-current pulsed magnetron
discharge, Plasma Physics Reports, Vol. 37, p.
621-627
[4] Y Yang, X Zhou, J X Liu, and A Anders, 2016 Evi-
dence for breathing modes in direct current, pulsed,
and high power impulse magnetron sputtering plas-
mas, Appl. Phys. Lett., Vol. 108, p. 034101
[5] C Huo, D Lundin, M A Raadu, A Anders, J T Gud-
mundsson, and N Brenning, 2013 On sheath energiz-
ation and Ohmic heating in sputtering magnetrons,
Plasma Sources Sci. Technol., Vol. 22, p. 045005
[6] A Anders, 2014 Localized heating of electrons in ion-
ization zones: Going beyond the Penning-Thornton
paradigm in magnetron sputtering, Appl. Phys. Lett.,
Vol. 105, p. 244104
HTPP14 Munich: Session 4
50
HTPP14 Munich: Session 4
51
Inductively Coupled Plasma Mass Spectrometry:
what can we learn from modeling? M Aghaei
*, A Bogaerts
PLASMANT research group, University of Antwerp, Belgium
Abstract
A self-consistent model for an atmospheric pressure in-
ductively coupled plasma (ICP), operating at typical ana-
lytical chemistry conditions (see Table 1) is presented.
The 2D axisymmetric model is based on solving partial
differential equations for the gas flow dynamics coupled
with the energy conservation and Maxwell equations. It is
built within the commercial computational fluid dynamics
(CFD) program FLUENT (ANSYS). The power coupling
into the ICP is a source term in the energy conservation
equation, whereas the emitted radiation is treated as a loss
term. Some user defined functions were added to calculate
the electromagnetic fields, the amount of ionization, as
well as the material parameters, i.e., electrical conductivity,
viscosity, heat capacity, thermal conductivity and diffusion
coefficients as a function of the actual gas composition
and plasma temperature. This makes it possible to apply
the model to a wide variety of gas mixtures, including
carrier gas and sample material.
The ICP torch is connected to a mass spectrometer (MS)
interface cone, considering the large pressure drop from
upstream to downstream (i.e. 1 atm to 1 torr) [1]. We per-
formed calculations for a wide range of gas flow rates and
applied power, and also for various sizes of the injector
inlet and sampler orifice [2, 3]. In order to optimize the
flow behavior inside the ICP torch, recirculation of the gas
flow was specifically investigated [4]. Furthermore, a dis-
crete phase model for elemental droplets was recently
built [5]. This case is relevant for “laser ablation” ICP-MS,
where the sample is injected as ablated elemental particles.
The trajectory of each droplet is calculated by integrating
the force balance acting on the particles. The heat lost or
gained by the particle will also appear as a source or sink
in the continuous phase energy equation. From the ioniza-
tion degree and the mass and charge conservation equa-
tions, the number densities of electrons and of the atoms
and ions of the sample material are calculated.
This model enables us to track the particles to determine
their position, their phase, velocity and temperature, both
in the ICP torch and at the sampler orifice. By integrating
the flux of ions passing through the sampler, and compar-
ing it to the flux of the entering material, we can calculate
the transport efficiency at different conditions and also
explain the underlying behavior. Figure 1 compares results
for on-axis and off-axis injection, and shows to what ex-
tent the ion clouds move in the radial direction and deviate
from the central axis in the case of off-axis injection
compared with on-axis injection. It should be realized that
early evaporation and more expansion from the central
axis, which are caused by none-optimal operating condi-
tions, have to be avoided since they cause that some part
of the sample ions
does not reach the sampler.
Table 1: Geometry and range of operating conditions
Frequency 27 MHz
Input power 750 – 1500 W
Carrier gas flow rate 0.3 - 2.5 L/min
Auxiliary gas flow rate 0.3 - 1.2 L/min
Coolant gas flow rate 12 - 16 L/min
Torch dimension 20 x 35 mm
Sampler distance from the load coil 7 – 17 mm
Figure 3: Effect of injection position on the ion clouds inside the ICP
torch, for on-axis (upper panel) and off-axis (lower panel) injection.
References
[1] Aghaei M, Lindner H, Bogaerts A, 2012 Effect of a
mass spectrometer interface on inductively coupled
plasma characteristics, J. Anal. At. Spectrom. 27 60
[2] Aghaei M, Lindner H, Bogaerts A, 2012 Optimization
of operating parameters for inductively coupled
plasma mass spectrometry: A computational study,
Spectrochim. Acta Part B, 76 56
[3] Aghaei M, Lindner H, Bogaerts A, 2013 Effect of
sampling cone position and diameter on the gas flow
dynamics in an ICP, J. Anal. At. Spectrom. 27 1485
[4] Aghaei M, Flamigni L, Lindner H, Gunther D, Bo-
gaerts A, 2014 Occurrence of gas flow rotational mo-
tion inside the ICP torch: a computational and ex-
perimental study, J. Anal. At. Spectrom 29 249
[5] Aghaei M, Bogaerts A, 2016 Particle transport through
an inductively coupled plasma torch: elemental droplet
evaporation, J. Anal. At. Spectrom. 31 631
HTPP14 Munich: Session 4
52
HTPP14 Munich: Session 5
53
Recent Progress in Cold Plasma Application for Cancer Therapy M Keidar
The George Washington University, Washington DC 20052
Plasma medicine is a relatively new field that outgrew
from research in application of low-temperature (or cold)
atmospheric plasmas in bioengineering. One of the most
promising applications of cold atmospheric plasma (CAP)
is the cancer therapy. Convincing evidence of CAP selec-
tivity towards the cancel cells has been accumulated. This
talk will summarize the state of the art of this emerging
field presenting various aspects of CAP application in
cancer such as role of reactive species (reactive oxygen
and nitrogen), cell cycle modification, in vivo application,
CAP interaction with cancer cells in conjunction with na-
noparticles, computational oncology applied to CAP [1].
CAP provides a unique, rich environment of reactive ox-
ygen species (ROS), reactive nitrogen species (RNS),
charged particles, photons, and electric field. Some chem-
ical components of the CAP are highly selective, such as
oxygen, which might promote a “plasma killing effect,”
while others such as nitric oxide could produce a “plasma
healing” effect. It should be pointed out that CAP produc-
es a level of reaction chemistry and unique chemical
composition similar to endogenous ROS/RNS cell chem-
istry. Combining these species in various controlled
blends provides an unprecedented possibility to activate
specific signaling pathways in cells and tissue. This is
critical in fields such as cancer therapeutics in which in-
troduction and delivery of these potentially selective
highly reactive species into tumors would enable selective
removal of cancer cells, while sparing healthy tissue.
The efficacy of cold plasma in a pre-clinical model of
various cancer types such as lung, bladder, breast, head,
neck, brain and skin has been demonstrated. Both in-vitro
and in-vivo studies revealed that cold plasmas selectively
kill cancer cells. It was shown that: (a) cold plasma appli-
cation selectively eradicates cancer cells in vitro without
damaging normal cells. (b) Significantly reduced tumor
size in vivo.
Plasma-stimulated media (PSM) shows remarkable an-
ti-cancer capacity as strong as the direct cold atmospheric
plasma (CAP) treatment of cancer cells. PSM is able to
effectively resist the growth of several cancer cell lines.
To date, the sole approach to strengthen the anti-cancer
capacity of PSM is extending the plasma irradiation time.
Recent study demonstrated that the anti-glioblastoma ca-
pacity of PSM could be significantly increased by adding
20 mM lysine in DMEM. It was also shown that the deg-
radation of PSM over time is mainly due to the reaction
between the reactive species and specific amino acids;
mainly cysteine and methionine in medium.
Tumor growth and its response to plasma treatment were
simulated using a three-dimensional hybrid dis-
crete-continuum model. The results compare untreated
and treated tumors of varying sizes by measuring spatio-
temporal data to predict trends of tumor evolution. The
simulation results show that the treated tumor death, irre-
spective of tumor volume, follows an exponential decay
and that the untreated tumor follows an expected growth
pattern.
Synergy between nanotechnology and CAP technology
can provide an additional strong benefit in biomedical
applications. In one of the first reports in this arena it was
shown that a special antibody-conjugated gold nanoparti-
cles could selectively target cancer cells. In fact in that
study a five-fold increase in melanoma cell death over the
case of the CAP alone by using air plasma with gold na-
noparticles was achieved. Additional recent result indi-
cated that strong synergy exists between gold nanoparti-
cles and cold atmospheric plasma in cancer therapy. Gold
nanoparticles (AuNPs) in combination with CAP can sig-
nificantly promote glioblastoma cell death. In fact, cancer
cells viability decreased by 30 % in comparison with con-
trol group having the same plasma dosage but no AuNPs
applied. Results of that study correlates well with the the-
ory that intracellular ROS accumulation results in oxida-
tive stress, which further changes the intracellular path-
ways, causing damage to the proteins, lipids and DNA. In
addition, CAP can promote nanoparticle uptake by cells.
In fact it was shown that gold nanoparticles were endocy-
tosed at an accelerated rate in the U87 cell membrane due
to the plasma treatment while no significant difference in
gold nanoparticle penetration into normal cells was ob-
served. Thus, combining CAP advantage with nanoparti-
cles opens up multiple benefits such as enhancing plasma
action and nanoparticle uptake outlined above. In addition,
using this strategy can lead to reduction of overall toxicity.
References
[1] M Keidar, 2015 Plasma for Cancer Treatment Plasma
Source Science & Technology, 24 033001
HTPP14 Munich: Session 5
54
HTPP14 Munich: Session 5
55
Design oriented modeling of thermal plasma sources and processes
with a focus on nanoparticles synthesis, metal welding and cutting M Boselli
1,2*, V Colombo
1,2, E Ghedini
1,2, M Gherardi
1,2
1Department of Industrial Engineering and
2Industrial Research Centre for Advanced Mechanics and Materials
Alma Mater Studiorum-Università di Bologna, Via Saragozza 8, Bologna 40123, Italy
Thermal plasma systems have relied extensively on mod-
eling techniques in the past years. Simulation is a power-
ful tool for both predicting the plasma thermo-fluid dy-
namics and for studying basic physical mechanisms. Re-
sults obtained from modeling can be used for new and
improved strategies for the design and optimization of
plasma sources and processes. The synthesis of nanopar-
ticles through inductively coupled plasma RF torches can
be strongly influenced by the reaction chamber geometry.
For instance, vortices can occur near the side walls of a
non-properly designed reaction chamber, causing a de-
crease in production yield due to material deposition on
the side walls, as well as an higher residence time in the
chamber for the nanoparticles, then characterized by an
increases in mean particle size diameter. An auxiliary
quench gas flow rate can be used to further tune and im-
prove the nanoparticle synthesis, but its injection can
occur with two different strategies that are active or pas-
sive quenching. They both have positive effects, but ac-
tive quenching is mainly used to reduce the mean particle
size, while passive quenching is mainly used to improve
the yield. In order to find the best operating conditions
for nanopowders production, different reaction chambers
geometries and quenching strategies can be investigated
by a design oriented modeling approach that deals with
nanoparticle synthesis and transport by means of the
Method of Moments.
Arc welding techniques are characterized by a wide range
of possible operating conditions, for instance for what
concerns the electric current waveform and the shielding
gas compositions, as function of the material to be weld-
ed and the technique to be used. A time dependent model
that takes into account melting and vaporization of the
metal wire, as well as droplet formation and detachment
by volume of fluid model, was developed in order to in-
vestigate globular and pulsed current transfer mode in gas
metal arc welding. The model was validated by compari-
son to experimental campaigns making use of high speed
imaging. Additionally, the Method of Moments was used
to investigate production and distribution of welding
fumes during a droplet transfer (Figure 1).
Plasma cutting torches are complex assemblies of several
part sets which are designed in order to give the best cut-
ting quality as possible for each given current level, plate
thickness, metal and cutting gas typology. The electrode
and the nozzle of the torch are consumables which can
experience major wear phenomena during a cutting pro-
cess when inadequate operating conditions or geometries
are selected. The hafnium emitter molten surface of the
electrode for instance is particularly sensitive to swirl
velocity of the gas coming from the plasma diffuser, as an
increase in gas flow rate increases the electrode erosion
rate. On the other hand the confinement of the arc column
in the nozzle orifice is improved by the increase in swirl
gas flow rate, with a reduction of occurrence of double
arcing and an increase in nozzle service life. An integrat-
ed investigation through experimental high speed imag-
ing and numerical modeling of the effects of different
plasma gas diffusers and consumables geometry allowed
to design several new set of consumables for different
operating currents with improved consumables service
life and cutting quality.
Figure. 1: Results from time dependent modelling of a pulsed MIG
welding process of a 1 mm diameter mild steel wire in argon atmos-phere during current pulse [Boselli et al. 2013 J. Phys. D: Appl. Phys.
46 224009].
Acknowledgements
Partial support by European Union’s Horizon 2020
re-search and innovation programme under grant agree-
ment No 646155 (INSPIRED project). The contribution
of Dr. P. Sanibondi is thankfully acknowledged as coau-
thor of some of the results that will be presented.
HTPP14 Munich: Session 5
56
HTPP14 Munich: Session 5
57
Direct Current (DC) Thermal Submerged Plasma Treatment of
Contaminated Solutions with Carboxylic Acid G Soucy
1*and S Safa
2
1Department of chemical and biotechnological engineering, Université de Sherbrooke, Sherbrooke, Canada, J1K 2R1
2 Department of chemistry, Université de Sherbrooke, Sherbrooke, Canada, J1K 2R1
Abstract
Several industries produce process liquors which are con-
taminated by organic compounds. It is the situation of
many Bayer plants using a caustic solution for the extrac-
tion of alumina trihydrate. Organic compounds contami-
nation can decrease liquor productivity either by increas-
ing alumina solubility or by covering active sites on alu-
mina hydrate seeds. [1] An innovative technology based
on submerged thermal plasma technology has been de-
veloped by Bernier, JL, et al. [2]. As presented in Figure 1,
the process involves a direct contact with thermal sub-
merged plasma. The solution is recirculated at high veloc-
ity by using an internal draft tube.
Figure 1: First experimental set-up of submerged thermal plasma [1].
Since this development of submerged thermal plasma
technology for treatment of caustic solution, many studies
have been accomplished by using plasma in liquid and
solutions. A full literature review on thermal plasma in
liquid and solution treatment has been completed by Safa
and Soucy [3]. The results of the different plasma sources
(DC plasma torches and radio frequency (RF) induction
plasma) have been discussed.
To improve the application of thermal plasma in sub-
merged mode, understanding the mechanism of organics
decomposition is necessary. In this paper, plasma in liquid
has been evaluated to decompose contaminated solutions
with a carboxylic acid
The sebacic acid (C10H18O4) has been selected as a mole-
cule to represents a molecular weight carboxylic acid. A
thermodynamic study has been completed to evaluate the
equilibrium composition of such complex species solu-
tion.
The experimental program [4] has included many tests to
measure the effect of some operating parameters such as
type of plasma gases (air, oxygen, etc.), addition of cata-
lyst, solution concentration by changing pH, operating
pressure, etc. The decomposition rate of this carboxylic
acid and the evaluation of the intermediate products have
been investigated. To perform this study, a new analytical
method for quantification of dissolved carboxylic acids
has been developed using IC/MS (Ion Chromatography
coupled with Mass Spectroscopy). The TOC analyzer
(Total Organic Carbon) has also been used to characterize
the amount of inorganic carbon in the solution.
The treatment by using oxygen plasma gas has allowed to
decompose up to 80 % of the sebacic acid solution after
30 min treatment. The intermediate products include a
large fraction of carbonic acid and a trace of other
low-molecular dicarboxylic acid (oxalic acid). Reaction
mechanism of the sebacic acid decomposition will be pre-
sented as a function of the operating parameters. Many
results have demonstrated the potential of using thermal
submerged plasma in process liquor and wastewater
treatments.
Acknowledgements
Grateful acknowledgements are made to NSERC (Natural
Sciences and Engineering Council of Canada) for its fi-
nancial support.
References
[1] Soucy G, Larocque E L and Forté G, 2004 Organic
control technologies in Bayer process, Light Metals,
Edited by A.T. Tabereaux, TMS (The Minerals, Metals
& Materials Society)
[2] Bernier J L, Fortin L, Kimmerle F, Boulos M I,
Kasireddy V, Soucy G 2001 Thermal plasma reactor
and wastewater treatment method. US patent
6,187,206, Patent Cooperation Treaty (PCT)
WO9722556 (1996)
[3] Safa S, Soucy G, 2013 Liquid and solution treatment
by thermal plasma: a review, Int. J. Environ. Sci.
Techno. DOI 10.1007/s13762-013-0356-3
[4] Safa S, Soucy G, 2014 Decomposition of high mo-
lecular weight carboxylic acid in aqueous solution by
submerged thermal plasma, Chemical Engineering J.
244 178-187
Vapor and gases
Feed
D.C. plasma torch
Sight tube
.229 m
Draft tube
Submerged plasma
HTPP14 Munich: Session 5
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HTPP14 Munich: Session 6, Poster S6-1
59
Physical simplified arc model for Gas Metal Arc Welding
(GMAW) process including cathode and anode layers M Mallon, J Schein
Institute of Applied Plasma Physics and Mathematics, University of the Federal Armed Forces Munich, 85577 Neubiberg
J L Marqués
Institute of Automation and Control, University of the Federal Armed Forces Munich, 85577 Neubiberg
General
This work presents the first steps of building a simplified
model for the description of the arc dynamics in the
GMAW process. It only requires the gas composition, the
applied current and the electrode geometry as inputs. Such
model includes the effect of metal vapour and instabilities
in the arc anode attachment. Since reliable GMAW data
for the evolution of the anode layer are difficult to obtain,
the new developed anode model will be first verified by
comparing the simulation with the observed behaviour in
a Gas Tungsten Arc Welding (GTAW) process. Subse-
quently the model will be applied to a GMAW arc whose
temperature is decreased by the presence of metal vapour.
Anode Layer Model
A detailed physical modelling of GMAW is required for a
feedback control aiming at a more stable process. Most
models being developed however describe only stationary
arcs [1]. Control theory on the other side needs simplified
dynamic equations which are eventually the main goal of
this work. As a first component in this new approach the
electrode layers are considered in detail.
The transition from the bulk plasma to the anode metal is
subdivided into two different sublayers (Fig 1). They en-
sure the uninterrupted flow of energy and current, as well
as determine the anode attachment.
Figure 1: Schematic of the anode layers.
The three essential parameters to describe the anode layer
behaviour are the anode attachment radius, the anode
voltage drop and the anode root temperature. Depending
on the boundary conditions provided from the bulk plasma
the attachment radius is derived from the current conser-
vation equation. Analogously the anode voltage drop is
calculated using the stationary energy flow equations from
the bulk to the pre-sheath and further to the sheath. The
sheath is assumed to be very thin so no dissipative pro-
cesses need to be considered. At last the anode root tem-
perature is derived from the stationary energy flow into
the anode metal.
Results
The simulation parameters for the anode model are the
applied current in the range of 5-400 A, an inter-electrode
separation of 10 mm, a radial distance to the cold sur-
roundings ranging from 1 to 10 mm and a temperature of
the cooling wall equal to 300 K.
Within the given current range the combined anode volt-
age drop increases constantly with the current, while al-
ways remaining negative (Figure 2). Such negative anode
voltage is also consistent with the more general discussion
in Ref. [2]. Additionally, the resulting anode attachment
radius keeps a larger value than the bulk plasma radius
(Figure 3).
Figure 2: Anode voltage drop as a function of the applied current for a
radius of 6 mm to the cooling surrounding.
Figure 3: Anode attachment radius and arc bulk radius as a function of
the applied current for a radius of 6 mm to the cooling surrounding.
References
[1] Murphy A B, 2010 The effects of metal vapour in arc
welding, J.Phys.D:Appl.Phys. 43, 1-31
[2] Londer Va I, Ul’yanov K N, 2013 Generalized
Bohm’s Criterion and Negative Anode Voltage Fall
in Electric Discharges, Plasma Phys. Rep. 39, 849
HTPP14 Munich: Session 6, Poster S6-1
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HTPP14 Munich: Session 6, Poster S6-2
61
Investigations of a pulsed current wire arc spraying process
A Atzberger1, G Huismann
2, M Szulc
3, S Kirner
1, S Zimmermann
1, G Forster
1 and J Schein
1
1 Lab for Plasma Technology (LPT), Universität der Bundeswehr München, Munich
2 Lab for Welding Technology, Universität der Bundeswehr Hamburg, Hamburg
3Zierhut Messtechnik GmbH, Munich
Introduction
Wire arc spraying is one of the oldest thermal spray pro-
cesses, which is preferably used due to its low operating
costs, easy handling and high deposition rates. With wire
arc spraying being the most cost-efficient of all thermal
spray processes, it is a technique commonly used in today’s
industries (e.g. automotive and aerospace industry).
The arc behaviour is being investigated, as it will re-ignite
in the smallest gap between the electrodes again when the
fluid and magnetic force on the arc is too strong.These
movements are called arc fluctuations and they are taking
place repetitively. However, these arc fluctuations are
taking place randomly and could not be controlled so far.
Investigations of the plasma cutting process have shown
that when a specific current pulse is applied the anodic arc
attachment can be influenced – the voltage drops and the
arc shortens respectively due to the changing attachment of
the arc. Having identified that experimental phenomenon
for plasma cutting, the transfer to the wire arc spraying
process has been carried out in the following investiga-
tions.
Test setup
An experimental wire arc spray system was built at the LPT
and used in the following experiments. As power supply
serves the GMAW power source “Phoenix 451” by the
company “EWM”, which can be run in DC as well as in
pulse mode. The Phoenix power source is equipped with a
second wire feeder and is responsible for the control of the
wire feed rate (which is directly linked to the current). It is
possible to adjust the two wire feeder rates separately. In
further experiments an additional GTAW power source
“Tetrix 300 puls“ also by “EWM” was used. In that pulse
combination, the Phoenix serves as DC source and the
Tetrix adds current pulses onto the existing DC signal –
thus a pulsed signal is being generated. The behavior of the
droplet ablation as well as the arc movement has been
recorded and evaluated using high speed shadow imaging.
The resulting coating properties were analysed by micro-
sections in order to evaluate the oxide content as well as the
porosity.
Results
First of all, a regular DC process has been analysed. The
voltage fluctuations take place randomly, but the overall
frequency range is rising with increasing gas pressure.
When analysing the HS images, a direct relationship be-
tween the length of the arc and the resulting process voltage
has been evaluated using an in-house image-processing
algorithm. In the next step, a Fast Fourier Transformation
has been carried out in order to evaluate a peak frequency
for a given gas pressure. This specific peak frequency was
used to pulse the current. Since the pulse mode of the
Phoenix 451 is not destined for high-frequent pulses, it was
not able to adjust the shape of the pulse any further. Thus,
the possibility of linking a GTAW power source to the
GMAW source was tested. In that constellation, the Phoe-
nix operates as a standard DC source and the Tetrix mod-
ulates the current on top of the DC signal. With this setup
the resulting current pulses showed a constant pulse shape
and the voltage dropped respectively. Simply put, the arc
re-ignites for every current pulse applied.
When analysing the resulting microsections it has been
recognized, that for a very specific position the oxide
content was significantly lower than a comparable DC
coating. A possible explanation could be that the current
pulses broaden the resulting particle distribution and
shifting the mean particle diameter to a higher values. With
the particles being larger, the surface-to-volume ratio is
smaller compared to the DC coating which results in a
lower oxidation of the particles. The density of the coating
is thus greater.
Conclusion
The investigation results show that by applying current
pulses in a specific frequency range it is possible to con-
trol the movement of the arc in its periodicity. Differences
in the resulting coating properties between DC and pulsed
mode have been investigated. The exact influence of the
current pulses on the particles remain to be explored in
future work.
Acknowledgements
The presented results derive from the IGF-project “Im-
provement of the layer quality of the wire arc spray pro-
cess by current modulation” (funding number 18.088 N).
The project, coordinated by the Research Association on
Welding and Allied Processes of the DVS, is funded by
the Federal Ministry of Economic Affairs and Energy
(BMWi) on basis of a decision by the German Bundestag
as part of the AiF Industrial Collective Research (IGF)
program. The support of this research project is gratefully
acknowledged.
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63
Combined electrical and optical partial discharge diagnostics R Kozakov
1*, M Bogaczyk
1, S Gortschakow
1
1Leibniz-Institute for Plasma Science and Technology, 17489 Greifswald, Germany
Introduction
Partial discharge (PD) diagnostics is a commonly accepted
procedure in the electric power generation and delivery
industry. The phase resolved partial discharge diagram
(PRPD) is the technique most frequently used. These dia-
grams represent statistical evaluation of the phase and
frequency of PD appearance accompanied by the meas-
urement of the amplitude of the so called apparent charge.
Based on the reference measurements it is possible to
identify specific defects in the high-voltage apparatus.
PD measurements are performed according to the existing
standard [1] which does not require the correct knowledge
on the form of each individual current pulse. On the other
side such information can give an additional insight in the
physics of PDs and give new tool in the evaluation of PD
status and degradation status of electro-technical appa-
ratus.
The typical rise times of sub-nanosecond scale represent a
challenging task for measurements of the current pulse
form. This work concentrates on the precise measure-
ments of both the electric current of an individual PD and
the optical signal produced by PD event. The optical sig-
nals do not suffer on the transmission line limitations and
are shown to carry same information as traditional PRPD
diagrams.
Experiments
Typical defects for medium-voltage cable like an electric
tree in epoxy resin and a void in cross-linked polyethylene
were investigated. Electric measurements were performed
with the help of ultra-wide band frequency devices with
4 GHz bandwidth. Although such device can resolve the
sub-nanosecond profile of the measured current, the
transmission lines between PD location and measuring
point introduce distortions in the obtained waveform. In
order to obtain the initial waveform the inversion algo-
rithm is applied to the measured signal which is known to
be a convolution of the real signal with the instrumental
profile of the experimental set-up: I measured (t) I real ( ) A(t )d . (1)
The instrumental profile of the set-up was determined as
the response of the measuring system to the step-up pulse.
The inverse problem (1) was solved based on the
Tikhonov regularization method [2].
Optical measurements were performed with the help of a
photomultiplier (PMT). The light detection from individu-
al PDs was possible. Typical waveforms of a measured
electrical current and optical signal are shown in Figure 1.
Results
The obtained waveforms were used for determination of
integral quantities – charge and light intensity. The PRPD
of both quantities show (Figure 2) that there exists a cer-
tain correlation in their distributions. Two branches can be
identified which belong to two different types of PDs –
surface discharge and void discharge.
Figure 1: Electrical current waveform (top) and corresponding signal of
the PMT (bottom).
Figure 2: Charge-light diagram shows two branches helping to distin-
guish between two types of coexisting PDs.
References
[1] Norm DIN EN 60270:2001-08, 2000 VDE
0434:2001-08 High-voltage test techniques - Partial dis-
charge measurement, IEC
[2] Tikhonov A N, 1963 Solution of ill-posed problems
and method of regularization Sov.Phys-Dokl 151 501-504
(in Russian)
HTPP14 Munich: Session 6, Poster S6-3
64
HTPP14 Munich: Session 6, Poster S6-4
65
Anode energy transfer in a transient arc F Valensi
1*, P Ratovoson, M Razafinimanana
1 and A Gleizes
1,2
1 LAPLACE (Laboratoire Plasma et Conversion d’Energie), CNRS-INPT-Université Toulouse III, 118 Route de Narbonne,
31062 Toulouse cedex 9, France 2CNRS, LAPLACE, 118 route de Narbonne, 31062 Toulouse Cedex 9
General
The separation of two contacts in an electric circuits leads
to so called transient arcs. They occur for instance in cir-
cuit breakers operation [1] or in the case of pantograph
arcing [2]. They are characterized by duration of a few
milliseconds to a few hundreds of milliseconds with cur-
rent of several hundreds or thousands amperes. Even with
an electrode gap of a few millimetres the arc voltage is up
to a few tens of volts. The resulting power is sufficient to
cause electrodes erosion, in particular at the anode. A bet-
ter understanding of the involved phenomena is then nec-
essary to improve contact materials resistance and systems
performances.This work is dedicated to the study of the
erosion of electrode and energy transfer analysis for sev-
eral arc conditions. Two pure anode materials (copper and
graphite) were studied and the work is extended to panto-
graph contact strip samples made of C-Cu composite.
Experimental setup
The detailed description of the experimental setup is given
in [3]. It is based on a capacitor bank and the maximum
current and time constant can be set independently. Ex-
periments were performed with peak current up to 2 kA
and time constants from 24 to 92 ms.The arc phase ends
when the voltage becomes too low but it is also possible to
shut down the arc after a given delay, as short as 1 ms.
The capacitor bank can also be split in two independent
parts, thus allowing double shots separated by a few mil-
liseconds. The cathode is made of a 6 mm cylindrical
graphite rod with tapered end. Two anode diameters
(6 mm and 15 mm) were used in the case of copper; tests
with graphite were performed with a 10 mm diameter an-
ode.The square contact strip samples (25% wt. Cu) were
15 mm wide. In all experiments the anode thickness was
about 10 mm. The distance between the two electrodes
can be set from 1 to 10 mm. The arc geometric configura-
tion and electrode erosion are observed with high speed
camera (4000 to 6000 fps). Qualitative information about
plasma composition can be obtained by using interference
filters corresponding to anode material or plasma gas
emission lines. The mass loss is measured by weighting
the samples before and after each experiment.
The electrical parameters were also recorded with a time
resolution of 25 µs.
Results
The erosion has been studied as a function of maximal
current, time constant and arc length. For all studied anode
material it appears that there is a current limit below
which erosion is negligible. This limit is about 500 A for
graphite and is lower than 300 A in the case of copper.
This threshold is likely to be related to the energy trans-
ferred to the anode needed to heat the material and cause
significant ablation. Then the first part of the current pulse
will cause no visible damage although the current reaches
its highest value. In the case of copper this first step dura-
tion is about 1 ms.The ablated mass increases with current,
especially with small diameter copper anodes. While mass
loss is mainly due to vaporization for current below 500 A
the contribution of melted metal ejection (in particular as
droplets) becomes predominant. Besides, according to the
anode size the arc length increase can lead to higher or
smaller erosion. The study of double arc experiments al-
lowed demonstrating non stationarity of the arc electrode
interaction. This is due to the fact that while the duration
of the experiments is far larger than plasma phenomena
time constants, it is the same order than electrode heating
and melting process.
References
[1] McBride J W, Weaver P M, 2001 Review of arcing
phenomena in low voltage current limiting circuit
breakers IEE Proc.-Sci. Meas. Tech 148-11–7
[2] Bormann D, Midya S, Thottappillil R, 2007 DC
components in pantograph arcing: Mechanisms and
influence of various parameters Proceedings of 18th
International Zurich Symposium on Electromagnetic
Compatibility, Munich, Germany 369–372
[3] Ratovoson P, Valensi F, Razafinimanana M, Tmeno-
va T, 2014 Journal of Physics: Conference Series
550 012012
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67
Effects of Copper on Thermophysical Properties and Net Emission
Coefficients of CO2-N2 Mixtures in High-Voltage Circuit Breakers L Zhong
1,2, Y Cressault
2*, X Wang
1*, M Rong
1, P Teulet
2
1 State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, No 28 XianNing West
Road, Xi'an, Shaanxi Province 710049, P. R. China 2 LAPLACE (Laboratoire Plasma et Conversion d'Energie), Université de Toulouse; CNRS, UPS, INPT; 118 route de
Narbonne, F-31062 Toulouse, France
*[email protected], [email protected]
CO2, N2 and their mixtures have been studied since a few
decades ago because of their wide applications in indus-
tries. In metal-inert-gas (MIG) welding and gas metal arc
welding (GMAW), CO2 and N2 are often used as shielding
gases. In gas circuit breakers (GCB), due to the high glob-
al warming potential (GWP) of SF6 (24000 times higher
than that of CO2), CO2 and N2 are also applied to replace
SF6 and reduce GWP.
However, few attention was paid to effects of impurities
(e.g. metallic vapour) on CO2-N2 plasma. Actually, the
presence of such impurities could modify significantly
characteristics of plasmas. Therefore, this paper is dedi-
cated to the investigation of influences of copper vapour
on thermophysical properties and net emission coeffi-
cients of CO2-N2 mixtures.
Firstly, the equilibrium compositions of CO2-N2 mixtures
contaminated by copper was calculated by the minimiza-
tion of the Gibbs free energy, assuming local thermody-
namic equilibrium (LTE). Totally 76 species were taken
into account. And based on the results of compositions,
the thermodynamic properties (including mass density,
specific enthalpy, and specific heat) were determined di-
rectly according to the formulas in our previous work [1].
Next, in order to obtain the transport coefficients, the col-
lision integrals between each species in the mixtures were
calculated. Four kinds of interactions for neutral-neutral,
neutral-ion, neutral-electron, and charged-charged interac-
tions were considered [2]. Then, the transport coefficients
(including electrical conductivity, viscosity, and thermal
conductivity) were calculated and discussed.
Using the collision integrals determined above, the four
kinds of combined diffusion coefficients, namely the
combined ordinary diffusion coefficient, combined elec-
tric field diffusion coefficient, combined temperature dif-
fusion coefficient, and combined pressure diffusion coef-
ficient, which describe the diffusion due to composition
gradients, applied electric fields, temperature gradients,
and pressure gradients respectively [3], were calculated.
Lastly, the radiation of the mixtures is estimated according
to the net emission coefficient [4]. Atomic and molecular
lines and continua were taken into account as described in
[5, 6]. The influence of copper and the role of the molec-
ular lines and continuum are presented depending on the
temperature, the pressure and the plasma’s size.
Acknowledgements
This work was supported by National Key Basic Research
Program ("973" Program) of China (No. 2015CB251001),
National Natural Science Foundation of China (No.
51407136 and No. 51521065), Fok Ying Tong Education
Foundation (No. 141058). This work was also supported
by the program of China Scholarship Council (CSC) for
joint-PhD students (No. 201506280131).
Refer-
ences
[1] Rong M, Zhong L, Cressault Y, Gleizes A, Wang X,
Chen F, Zheng H, 2014 J. Phys. D: Appl. Phys. 47,
495202
[2] Wang X, Zhong L, Cressault Y, Gleizes A, and Rong
M, 2014 J. Phys. D: Appl. Phys. 47, 495201
[3] Zhong L, Wang X, Rong M, Wu Y, and Murphy A B,
2014 Phys. Plasmas 21, 103506
[4] Cressault Y, 2015 AIP Advances 5, 057112
[5] Billoux T, Cressault Y, Gleizes A 2015 J.Q.S.R.T 166,
42-54
[6] Billoux T, Cressault Y, Borestskij V F, Veklich A N,
Gleizes A, 2012 J. Phys. D: conference series 406,
012027
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69
Properties of air thermal plasma contaminated with AgC and AgNi
vapours resulting from electrodes’ erosion Y Cressault
1*, Ph Teulet
1, V Boretskij
2, A Veklich
2
1 Université de Toulouse; UPS, INPT; LAPLACE (Laboratoire Plasma et Conversion d’Energie) ; 118 route de Narbonne,
F-31062 Toulouse Cedex 9, France 2 Taras Shevchenko Kyiv National University, Radio Physics, Electronics and Computer Systems Faculty,
64, Volodymyrs'ka Str., Kyiv, 01033, Ukraine
The thermal plasmas often exist in several industrial pro-
cesses: aeronautics, welding, cutting, high pressure lamps,
plasma spraying, or circuit-breakers. An electrical arc is
generally created between two electrodes manufactured
with specific materials such as copper, silver, or carbon.
The process’ efficiency depends on several parameters
(temperature, pressure, concentrations of the species, size
of the plasma …) which influence the energy transfers in
the plasma (by radiation, conduction, convection, diffu-
sion or joule effect). The medium is then modified by the
presence of the arc and more particularly by new species
resulting from the contacts’ erosion. The nature of the
materials constituting these contacts and their erosion
phenomena are two key points to be considered for a bet-
ter understanding of the plasma’s behaviour.
Nowadays, the numerical simulation are enough per-
formed to characterize the electrodes’ phenomena (near
cathode and anode), the sheaths and the arc channel. The-
oretically, the methods available for the calculation of the
radiative and transport properties under LTE assumption
are well-known in the community [1]. The comparisons
between calculations and measurements of radiation are
often in good agreement. At contrary, few experimental
studies exist helping us to validate the transport properties
used in the numerical modelling, probably due to complex
physical mechanisms, fast change of the plasma’s behav-
iour, diffusion of vapours in the volume, presence of gra-
dients, or strong radiation. From the temperature and pop-
ulations number densities profiles deduced from optical
emission spectroscopy technics, we can estimate the
compositions of the mixtures and calculate the corre-
sponding thermal and electrical conductivities or viscosi-
ties [2].
This work proposes to study the influence of specific me-
tallic vapours (AgC and AgNi constituting electrodes or
contacts) on the transport coefficients of air plasmas, at
atmospheric pressure. The plasma composition (popula-
tion number densities of the species in the plasma) was
calculated for temperatures between 300 K and 30000 K.
From these data, the specific heat at constant pressure and
the transport coefficients such as thermal and electrical
conductivities or viscosity have been estimated. The
well-known Chapman-Enskog method has been applied
using the collision integrals obtained either from previous
works
or from empirical expressions given by Hirschfelder [3]
and assuming Lennard-Jones potential to characterize col-
lisions between neutral particles, polarizability potential
for charged-neutral interactions, and Screened Coulomb
potential for collision between charge particles including
electrons. Previous works on air-silver mixtures [4] high-
lighted the strong effect of metallic vapours on electrical
conductivity (see figure 1). Here, this influence is pre-
sented on the three transport coefficients in the case of air
plasmas contaminated with AgC and AgNi vapours.
Figure 1: Electrical conductivity of air-silver plasmas atmospheric
pressure (Figure 9 in [4]).
Further works will consist in calculating the radiative
properties. Thanks to a superposition of the measured
spectra with the theoretical simulations for several tem-
peratures, it will be possible to evaluate the consistency of
both studies, to estimate the plasma’s composition and to
determine the corresponding transport coefficients.
Acknowledgements
This work is supported by Campus France (PHC Dnipro
No. 34827ZF).
References
[1] Cressault Y, 2015 AIP Advances 5, 057112
[2] Boretskij V, Cressault Y, Veklich A, Teulet Ph, 2011
XIXth Symposium on Physics of Switching Arc, Brno
University of Technology (Czech Rep.)
[3] Hirschfeleder J O, Curtis C F, Bird R B, 1964 Molec-
ular theory of gases and liquids (2nd
ed, Wiley, NY)
[4] Cressault Y, Teulet Ph, Hannachi R, Gleizes A, Gonnet
J P, Battandier J-Y, 2008 PSST 16, 035016
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Composition of Non-LTE CO2-CH4 Plasma with Condensed Phase Z Chen, Y Wu
*, F Yang, M Rong, H Zhang, C Wang
State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, China
Introduction
The plasma composition is one of the most basic and im-
portant data in plasma property calculation and plasma
simulation. For non-LTE plasma, which is common espe-
cially in circuit breaker during current-zero periods, the
2-Temperature composition is a prerequisite for further
research and calculation. The widely used 2-T mass action
law method does not take into account the influence of
condensed species which could be significant at low tem-
perature. In this paper, a new method of considering con-
densed species in 2-T mass action law based on local
chemical equilibrium (LCE) and local phase equilibrium
is presented. The composition of CO2-CH4 mixture, which
may be a possible substitution for SF6, is calculated by
this method as an example.
2-T Composition with Condensed phase
The classic 2-T mass action law presented by Van de
Sanden has been widely used in calculation of non-LTE
plasma composition [1]. However, the phase transition
process cannot be considered by this method and therefore
this method could be inaccurate for plasma system where
the condensing effect is not negligible.
According to the second law of thermodynamics, when a
multi-component system reaches phase equilibrium, the
chemical potential of condensed particle equals to that of
corresponding gaseous particle, which is given by
i gas
i cond (1)
where i gas and i cond are chemical potential of gaseous
particle and corresponding condensed particle respectively.
By using this equation, the composition of condensed spe-
cies is calculable.
Calculating chemical potential of condensed particle and
its corresponding gaseous particle is the crux for using this
method. The chemical potential of a gaseous particle can
be derived from its molar fraction, formation enthalpy and
molar tempered Gibbs energy, which is determined by
partition function. For the condensed particle, the chemi-
cal potential cannot be established by calculation with
sufficient accuracy and therefore the data are derived from
measurement data. In the present calculation, we use the
fitting data presented by Coufal [2] on the assumption that
the chemical potential of condensed particle is governed
by temperature of heavy species.
A Sample Calculation
In recent research, CO2-CH4 mixture is thought to be a
possible substitution for SF6. In this part, the 2-T compo-
sition of 50% CO2 - 50% CH4 mixture by molar fraction at
atmospheric pressure is calculated for different
non-equilibrium parameter using the method presented
above. Totally 31 different species including condensed C
(graphite) are considered.
Figure 1 shows the molar fraction of 50% CO2 - 50% CH4
mixtureat atmospheric pressure. Under LTE, the graphite
does influence the composition significantly (nearly 50 %),
which consists with research presented by Aubretonet al
[3], as shown in Figure 1 (a). The non-LTE effect on con-
densed phenomenon shows in two ways (Figure 1(b)).
Firstly, the sublimation process is mainly governed by Th
and therefore this process is shifted to higher electron
temperature in non-LTE system. Secondly, at same Th, the
higher non equilibrium parameter ( = Te
/ Th ) in
non-LTE system leads to higher Te, higher molar tempered
Gibbs energy and lower chemical potential of gaseous
particle. It means that at same Th, the non-LTE system is
able to contain more gaseous particles than LTE system.
This is the reason of low molar fraction of graphite in
non-LTE system.
Figure 1: (a) molar fraction of 50 % CO2 – 50 % CH4 mixture in low
temperature under LTE at atmospheric pressure. (b) Molar fraction of
graphite in 50% CO2 - 50% CH4 mixture with different non-equilibrium
parameters at atmospheric pressure.
Acknowledgements
This work is supported by the National Key Basic Re-
search Program of China (973 Program, No.
2015CB251002), the National Natural Science Founda-
tion of China (Nos. 51521065, 51577145)
References
[1] Wu Y, Chen Z et al., 2015 J. Phys. D: Appl. Phys. 48,
415205 (25pp) [2] Coufaland O, Zivny O, 2011 THE EUROPEAN
PHYSICAL JOURNAL D, 61, 131–151 [3] Aubreton J, Elchinger M-F et al., 2009 J. Phys. D:
Appl. Phys. 42, 415205 (13pp)
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73
High rate synthesis of Si/SiOx nanoparticles/nanowires using modu-
lated induction thermal plasmas with controlled feedstock feeding Y Tanaka
1*, Y Ishisaka
1, N Kodama
1, K Kita
1, Y Uesugi
1, T Ishijima
1, S Sueyasu
2, K Nakamura
2
1Faculty of Electrical & Computer Engineering, Kanazawa University, JAPAN
2Research Center for Production & Technology, Nisshin Seifun Group Inc., JAPAN
Introduction
We have originally developed a unique method to synthe-
size nanopowder with a high production rate using a
pulse-modulated induction thermal plasma (PMITP) with
time-controlled feedstock feeding (TCFF) [1]. We call it
‘PMITP-TCFF method’. The PMITP provides a periodi-
cally changed temperature field in the plasma torch. Dur-
ing the high-temperature period, the feedstock powder is
selectively supplied to the PMITP by opening the valve
installed between the torch and the powder feeder. This
selective feeding offers efficient and complete evaporation
of the feedstock. During the successive lower-temperature
period, the feedstock feeding is stopped by closing the
valve. We found that the PMITP-TCFF method could
synthesize nanopowder with a high production rates
500 g/h for TiO2 nanopowder, and 400 g/h for Al-doped
TiO2 nanopowder at 20 kW [1, 2]. These production rates
are 10-20 times higher than those by the conventional
thermal plasma method.
The present report describes the application of this method
to silicon (Si) nanoparticles synthesis. Silicon nanoparti-
cles are anticipated as high-capacity anode materials for
lithium ion batteries (LiB), solar cell materials,
bio-medical labels, etc. In addition, we also found, that the
PMITP-TCFF method can provide Si/SiOx nanowires,
which is also a candidate material for the anode materials
of the next-generation LiB.
Experimental condition
In the present work, the same PMITP-TCFF system was
used to that in our previous work [1, 2]. The PMITP was
operated at a base input power of 20 kW. The modulation
condition of the coil current was set to 80 % shimmer cur-
rent level (SCL), 80 % duty factor (DF) and a cycle of
15 ms. The pressure in the chamber was fixed to be
300 torr. The Ar gas was supplied as a sheath gas with a
flow rate of 90 L/min, and H2 gas is supplied as a plasma
gas with flow rate of 1 L/min. The Si feedstock powder
(𝑑 ̅~19.2 μm) was fed to the PMITP with Ar carrier gas,
being synchronized intermittently [2]. For nanopowder
synthesis, the feedstock feeding rate was set to 3.9 g/min
and Ar quenching gas was injected downstream of the
torch with a flow rate of 50 L/min. Synthesized nanoparti-
cles were collected in the collection filter. On the other-
hand, nanowire was synthesized with a heavy-load feeding
rate (~6.9 g/min) of Si feedstock powder without quench-
ing gas injection. Nanowires were collected around the
wall surface of the reaction chamber.
Results of Si nanoparticles and Si/SiOx nanowires
Figure 1 shows a FE-SEM image of synthesized Si parti-cles collected in the filter. Many nanoparticles were found with a mean diameter around 84 nm using the PMITP-TCFF method. The equivalent mean diameter was also evaluated as 99 nm from BET method. The XRD analysis indicates Si crystalline nanoparticles synthesized. The production rate was estimated as 120 g/h at 20 kW.
Figure 2 presents a FE-SEM image of nanowires fabri-
cated with a heavy-load feeding without quenching gas
injection. Many nanowires of diameter around 10 nm can
be obtained. It is inferred that high Si atom density and its
moderate cooling promotes to grow nanowires. From
EDX analysis, synthesized nanowires were composed of
Si and O. The production rate of nanowire was estimated
as more than 1 g/h.
Figure 1: FE-SEM image of synthesized Si nanoparticles.
Figure 2: FE-SEM image of Si/SiOx nanowires synthesized.
References [1] Tanaka Y et al. 2012 J. Phys. Conf. Ser., 406,
012001 [2] Kodama N et al. 2014 J. Phys. D: Appl. Phys. 47,
195304
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Role of hydrogen in high-yield growth of boron nitride nanotubes
by induction thermal plasma K S Kim
1*, M Couillard
2, M Plunkett
1, B Simard
1
1 Security and Disruptive Technologies Portfolio, National Research Council Canada, Ottawa, Ontario K1A 0R6
2 Energy, Mining and Environment Portfolio, National Research Council Canada, Ottawa, Ontario K1A 0R6
Boron nitride nanotubes (BNNTs) are rolled-up cylinders
of single or few-layered hexagonal boron nitride (h-BN)
sheets. Despite their structural similarity to carbon nano-
tubes (CNTs), BNNTs exhibit a range of physical and
chemical properties distinct from CNTs mainly attributed
to the partial ionic bonding character of BN [1]; they ex-
hibit an extraordinary heat resistance up to 900˚ C in the
air, electrical insulation with high thermal conductivity,
and the ability to create electricity when subjected to me-
chanical twisting or stretching. Despite their potential as
new class of multifunctional materials, it has been very
difficult to produce BNNTs at large scales.
Recently, we reported scalable manufacturing of
high-quality boron nitride nanotubes (BNNTs) directly
from h-BN powder by using induction thermal plasma
with an unprecedentedly high-yield rate approaching to
20 g/h [2]. The main finding was that the presence of hy-
drogen in the reaction stream is crucial for the rapid
growth of BNNTs at atmospheric pressure (Figure 1(b)
and 1(d)); however, in the absence of hydrogen, the prod-
ucts are largely amorphous B, illustrating the inefficiency
of the direct recombination of B and N2 into BN phase
(Figure 1 (a) and (c)).
Figure 1: Effects of hydrogen on the BNNT growth in induction thermal
plasma.
Here we investigate the hydrogen-mediated plasma chem-
istry using in-situ optical emission spectroscopy (OES) to
understand the detailed role of hydrogen in the rapid
growth of BNNTs in our plasma process. The emission
spectra were measured with and without hydrogen to in-
vestigate the spatial evolution of chemical species along
the reactor axis at three different positions: z=23, 33 and
73 cm from the plasma torch exit.
We found that, in the early stage of the process, hydrogen
promotes the formation of NH and BH radicals from the
dissociation of the feedstock. They are all effective pre-
cursors for h-BN phase formation. The SEM and TEM
analysis also suggest that the presence of hydrogen en-
hances the feedstock treatment efficiency by improving
the heat transfer rate. Based on this new observation we
will discuss a growth mechanism of BNNTs in our plasma
process.
Figure 2: The emission spectra measured without (top) and with (bot-
tom) hydrogen during the BNNT synthesis by induction thermal plasma.
References
[1] Shin H, Guan J, Zgierski M Z, Kim K S, Kingston C
T, Simard B, 2015 Covalent functionalization of bo-
ron nitride nanotubes via reduction chemistry ACS
Nano 91 2573
[2] Kim K S, Kingston, C T, Hrdina A, Jakubinek M B,
Guan J, Plunkett M, Simard B, 2014 Hydro-
gen-catalyzed, pilot-scale production of small diame-
ter boron nitride nanotubes and their macroscopic as-
semblies ACS Nano 8 6211
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Leucoxene carbothermal treatment in DC plasma-arc reactor D E Kirpichev, A A Nikolaev, A V Nikolaev, A V Samokhin
A.A.Baikov Institute of Metallurgy Science RAS, Russia [email protected], [email protected]
Introduction
The main titan ore reserves in Russia are concentrated in
leucoxene oil-bearing sandstone. Leucoxene ore prepara-
tion includes flotation, concentrate processing in auto-
claves with subsequent chlorination. The autoclave stage
can be replaced by more effective on resources car-
bothermal treatment. At the same time there is a selective
SiO2 reduction to volatile monoxide SiO, its evaporation
and removal out of reactor in exhaust gas to the subse-
quent condensation.
Thermodynamic analysis
Calculations of equilibrium composition and thermody-
namic properties of the TiО2 – SiO2 – C system was exe-
cuted with use of the program TERRA complex at the
following parameters: the interval of temperatures from
1000 K to 3000 K, pressure is 0.1 MPa, carbon content is
in the range 5- 40 mass%. It is calculated that effective
leucoxene carbothermal treatment with full TiO2 and SiO2
separation is possible with carbon content is equal
10 mass/%, temperature is T = 2200 K and atmospheric
pressure‘Figure 1’.
Figure 1: The equilibrium composition .0.45 TiO2 – 0.45 SiO2 – 0.10 C
system in the temperature range 1000-3000 K.
Experiment results and discussion
Experimental setup is 100 kW DC plasma-arc reactor with
source, gases and power supply systems. Exhaust gas is
cooled and powder separated via heat exchanger and filter.
The produced materials were analysed by the X-ray dif-
fraction (XRD) analysis (RIGAKU Ultima – 4), Specific
Surface Area measurements (Micromeritics TriStar 3000);
particle morphology (Helios 650 NanoLab). Leucoxene
and carbon mixture was loaded with argon into the anode
spot on the pool surface via the channel of the hollow
graphite cathode. Melt collected in the graphite crucible
which was connected to a positive pole of the power sup-
ply. Vaporized material was taken out with exhaust gas
from the reactor, after cooling and condensation it was
collected on the filter. There were two condensed prod-
ucts: an ingot in a crucible and powder in the filter. The
ingot represented the synthetic rutile in a varying degree
cleared of silicon. Filter powder consisted of SiO2 and Si.
Three experiments differing in excess of carbon contain in
charge and arc power have been carried out. Experiment
parameters are presented in the Table 1.
Table 1: Process parameters and products characteristics (carbon con-tent in charge is equal 10 – 20 % and the arc power is equal 10 –
20 kW).
The structure of filter powder is presented generally by
silicon fibers about 10 nm thick and up to 1 μm long ‘Fig-
ure 2’.
Si O Ti Al Fe
78,61 14,5 4,85 0,94 1,1
Figure 2: Filter powder produced SEM results.
Conclusion
Leucoxene carbothermal treatment in DC plasma-arc re-
actor allows to reduce approximately five times the con-
tent of silicon in a initial leucoxene concentrate and to
receive the titaniferous raw materials, suitable for further
processing, containing 49.2 % of Ti and 3.6 % of Si. The
second product of plasma-arc leucoxene carbothermal
treatment is nanopowder in fiber form. Energy consump-
tionat experimental setup is 6111 – 11806 kWh/t a con-
centrate, the specific output is 20 t / (m3day).
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High voltage AC plasma torches with long electric arcs for
plasma-chemical applications A V Surov
1, 2*, S D Popov
1, 2, E O Serba
1, A V Pavlov
1, Gh V Nakonechny
1, V A Spodobin
1, A V Nikonov
1, D I Subbotin
1,
A M Borovskoy1
1Institute for Electrophysics and Electric Power of Russian Academy of Sciences (IEE RAS), Dvortsovayaemb. 18, 191186,
St.-Petersburg, Russia 2Peter the Great St. Petersburg Polytechnical University, Polytechnicheskaya 29,195251, St.-Petersburg, Russia
Powerful AC plasma torches are in demand for a number
of advanced plasma chemical applications [1], they can
provide high enthalpy of the working gas. At the present
time thermal chemical processes are significantly inferior
to catalytic process on a selectivity and a specific energy
consumption. However, thermal plasma techniques may
be used for obtaining and processing of certain chemicals.
Their main aims are plasma hydrocarbons reforming [2],
toxic waste destruction [3] and electric arc methane py-
rolysis. In this case, it is possible to achieve an extremely
small amount of byproducts and high conversion of raw
materials. Thus, it is important that applied plasma torches
are operated with high power, efficiency and long lifetime.
One of the problems of thermal plasma technology is us-
age of air and inert gases as plasma forming gases. This
causes a formation of nitrogen oxides and increases
amount of ballast gases and processing costs. So now an
urgent task is development of a powerful (more than
500 kW) steam plasma torch for chemical applications.
IEE RAS specialists have developed a number of models
of stationary thermal plasma generators for continuous
operation on air in the power range from 5 to 500 kW, and
on mixture of H2O, CO2 and CH4 at 120 kW [4]. The
powerful AC plasma torch with lifetime of continuous
operation on air more than 1000 hours and thermal effi-
ciency about 90 % is shown in Figure 1. This is device
with hollow electrodes and the gas vortex stabilization of
arc in cylindrical channels. The electric arc length be-
tween two electrodes of the plasma torch exceeds 2 m. It
allows working with a high arc voltage drop (~ 2-3 kV) at
relatively low currents (no more than 100 A) what favora-
bly affects the lifetime of electrodes. Investigations on the
experimental installation equipped with supply systems,
mass flow controllers for plasma forming gases, acquisi-
tion of electrical parameters, high-speed video and spec-
tral diagnostic equipment were carried out to create such
device. A series of experiments with power from 100 to
450 kW and flow rates of air 20-100 g/s were carried out.
Arc column of the plasma torch has several specific areas
with different ambient conditions: the near-electrode sec-
tions; arc columns stabilized on axes of long cylindrical
channels; transversely blown section out of channels.
Temperature measured at the outlet of the channels of the
plasma torch operating on mixtures of H2O/CO2/CH4 with
power of 80-120 kW was about 8.5 103K, electric field-
strength values of the arc column were 14-18 and
14-22 V cm-1
for arc sections in channels and out of them
respectively. Temperature measured at the outlet of the
channels of air plasma torches were about 5·103 K. Elec-
tric field strength values of the arc column for low-power
plasma torch (up to 10 kW) were about 30-40 V cm-1
, and
for high-power air plasma torch (over 400 kW)
7-11 V cm-1
.
Carried out investigations allowed to start developing a
high-power plasma torch required for different chemical
applications (for example steam and carbon dioxide plas-
ma reforming [5]).
Figure 1: High voltage AC plasma torch. Operation power 450 kW.
Acknowledgements
The work is supported by the RFBR grant 15-08-05909-a.
References
[1] Fulcheri L, Fabry F, Takali S, Rohani V, 2015 Three
Phase AC Arc Plasma Systems: A Review Plasma
Chem Plasma Process 35, 565
[2] Fridman A, Gallagher M J, 2011 Fuel Cells: Technolo-
gies for Fuel Processing. Ch. 8. Plasma Reforming for
H2-Rich Synthesis Gas, Elsevier
[3] Evangelisti S, Tagliaferri C, Clift R, Lettieri P, Taylor
R, Chapman C, 2015 Integrated gasification and plas-
ma cleaning for waste treatment Waste Management
43, 485
[4] Rutberg Ph, Nakonechny Gh, Pavlov A, Popov S,
Serba E, Surov A, 2015 AC plasma torch with a
H2O/CO2/CH4 mix as the working gas for methane re-
forming J. Phys. D: Appl. Phys. 48, 245204
[5] Rutberg Ph, Kuznetsov V, Popov V, Popov S, Surov A,
Subbotin D, Bratsev A, 2015 Conversion of methane
by CO2+H2O+CH4 plasma Appl. Energy 148, 159
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The Investigation of the AC Plasma Torch Working Conditions for
the Plasma Chemical Supplement A A Safronov
1, O B Vasilieva
1, J D Dudnik
1*, V E Kuznetsov
1, V N Shiryaev
1, D I Subbotin
1, A V Pavlov
1
1Institute for Electrophysics and Electric Power of RAS Saint-Petersburg,191186 Dvortsovaya nab. 18
Abstract
Different types of plasma chemical technologies (such as
processing, destruction of the various kinds of wastes in-
cluding technogenic and dangerous wastes, conversion or
chemical creation, obtaining nanomaterials, etc.) are very
promising, in relation of the process efficiency. Their ap-
plication on the commercial-size basis is complicated due
to the lack of the inexpensive and reliably working plasma
generators of a rather big power [1], with the technical
characteristics providing necessary conditions for carrying
out the technological process. The presented design of a three-phase AC plasma torch
with the power up to 150–500 kW, providing a working
gas flow rate 30–50 g/sec [2], creating a plasma jet with
almost invariable temperature about 5000 K in the big
region of space could become the solution of this problem.
Therefore it becomes possible to create the plasma chem-
ical industrial-scale plant on the basis of the above men-
tioned plasma torch. Furthermore this plasma torch could
be used for various gas-phase chemical supplements (a
plasma reforming of natural gas [3] etc.), and also for ob-
taining fine powders and oxide nanopowders with high
temperatures of the phase transition.
The railgun effect i.e. the principle of an electric arc
movement in the field of its own current is the basis for
the plasma torch work. Arcs, arising in the electric dis-
charge chamber of the plasma torch, move along elec-
trodes under the action of the electrodynamics forces ap-
pearing as a result of the interaction between the arc cur-
rent and its own magnetic field, which is possible in virtue
of the single admission of the arc power supply. There is a
transition of the arc from one electrode to another [4]
while changing anodic and cathodic phases with the fre-
quency of 300 Hz, thanks to the three-phase supply volt-
age.
An opportunity to organize the arc binding movement [5]
along the electrode is the main feature of this design. That
allows providing equilibrium distribution of the thermal
burdening and the usage of rather cheap materials with
low heat resistance.
References
[1] Rutberg Ph G, Safronov A A, Goryachev V L, 1998
Powerful AC Plasma Torches Proceedings of the Rus-
sian Academy of Sciences: Power Engineering №1.
1998, 80-92
[2] Vinogradov S E, Vasilieva O B, Kuznetsov V E,
Kuzmin K A, Safronov A A, Ovchinnikov R V, Sche-
kalov V I, Shiryaev V N, 2010 The investigation in-
fluence of the chrome submicronic particles on the
electrode material properties of the low-temperature
plasma torches from alloys on the basis of copper
Material science quiestions № 4. 111-117
[3] Vasilieva O B, Kumkova I I, Rutberg A F, Safronov A
A, Shiryaev V N, 2013 Possibilities of application of
plasma technologies to recycle organic-containing
substances: particularities of the processes in the arc
chambers of plasma torches, High Temperature, Vol.
51, No. 1, 29-33, Pleiades Publishing, Ltd., ISNN
0018-15IX
[4] Kuznetsov V E, Popov S D, Spodobin V A, Ovchinni-
kov R V, Dudnik Yu D, Vasilieva O B, 2015 The in-
vestigation of methods for increasing the electrodes
lifetime and the continuous work of electric arc AC
plasma torches Proceedings of the Russian Universi-
ties: Physics № 9/2, Volume 58, 17-20
[5] Rutberg Ph G, Kuznetsov V A, Popov V E, Popov S D,
Surov A V, Subbotin D I, Bratsev A N, 2015 Conver-
sion of methane by CO2+H2O+CH4 plasma, Applied
Energy, Volume 148, 159–168
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Development of a loop type of inductively coupled thermal plasma
torch for large-area and rapid surface oxidation of Si substrate Y Tanaka
1*, T Tsuchiya
1, Y Maruyama1, H Irie
1, Y Uesugi
1, T Ishijima
1, T Yukimoto
2, H Kawaura
2
1 Faculty of Electrical & Computer Engineering, Kanazawa University, JAPAN
2 CV Research Corporation, JAPAN
Introduction
The inductively coupled thermal plasma (ICTP) has been
widely used for various materials processing such as
plasma spray coating, nanopowder synthesis, etc. Howev-
er, the conventional cylindrical ICTP is hardly adequate to
large-area materials processing because it need a large
volume and then high input power. For the purpose of
large-area surface modification using thermal plasmas, we
first developed a planar-type of ICTP [1], and then a loop
type of ICTP (loop-ICTP) [2]. This report describes the
trial adoption of the developed loop-ICTP for
two-dimensional (2D) surface oxidation of a Si substrate.
As a result, only one minute irradiation of Ar-O2
loop-ICTP provided an oxide layer with a 100 nm thick-
ness on the Si substrate surface. Furthermore, scanning the
substrate offered 2D oxidation of the 2 inch Si substrate.
Loop type of induction thermal plasma torch
Figure 1 shows the loop-ICTP torch and the scanning sub-
strate holder developed. The loop-ICTP torch has a loop
quartz tube with 8 mm diameter. Lower parts of the loop
quartz tube are connected with a rectangular quartz vessel.
Argon gas can be supplied from the top of the loop torch,
whereas O2 gas is fed from the top of the rectangular
quartz vessel under the loop through a porous ceramic.
The porous ceramic is used because O2 gas is almost uni-
formly supplied on the substrate. The rectangular quartz
vessel is evacuated with a vacuum pump from the lower
side. In the vessel, there is a scanning substrate holder
made of Si3N4. The holder is movable perpendicular to the
loop plane. On this holder, a 2-inch substrate can be
placed. Two coils are located sandwiching the loop-tube.
To this coils, an rf current is supplied from an rf inverter
power source. The thermal plasma is established in the
loop tube and also on the substrate located on the holder.
Scanning the substrate offers a 2D oxidation processing of
the substrate.
Experimental conditions
The experimental condition for 2D oxidation test is as
follows: Ar gas was supplied from the top of the torch
with a flow rate of 1.5 slpm. Oxygen gas was fed with a
flow rate of 0.2 slpm. The pressure was set to 10, 15, and
20 torr. The input power was fixed at 5 kW. A Si (100)
substrate with a 2-inch diameter was placed on the sub-
strate holder. The loop-ICTP was twice irradiated to the Si
substrate with a scanning speed about 0.5 mm/s. The
thickness of the oxide layer fabricated on the Si substrate
was measured with optical interference method.
Results for 2D oxidation of Si substrate
From the experiments we found only one minute irradia-
tion of Ar-O2 loop-ICTP could create the oxide layer with
a thickness deeper than 100 nm. This indicates that ther-
mal plasma irradiation provides extremely high oxidation
rates more than 100 nm/min. Figure 2 illustrates the
two-dimensional distribution of oxide layer thickness on
the 2-inch Si substrate after irradiation of Ar/O2 ICTP at
20 torr. The Si substrate has almost uniform oxide layer
with a thickness around 114 nm just after two scanning.
This indicates that loop-ICTP is adoptable to rapid surface
modification for 2" substrate.
Figure 1: Loop type of inductively coupled thermal plasma torch.
Figure 2: Two-dimensional distribution of thickness of oxide layer fab-
ricated by scanning loop-ICTP irradiation.
References
[1] Akao M et al., 2013 21st Int. Symp. Plasma Chem.
(ISPC-21), No. 247
[2] Tanaka Y et al., 2015 22nd Int. Symp. Plasma Chem.
(ISPC-22), O-21-3
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Suitability of thermal plasmas for large-area bacteria inactivation
on temperature-sensitive surfaces – first results with Geobacillus
stearothermophilus spores.
M Szulc1*
, S Schein2, J Schaup
2, S Zimmermann
2, J Schein
2
1 Zierhut Messtechnik GmbH, Munich
2 Lab for Plasma Technology (LPT), Universität der Bundeswehr München, Munich
Introduction
Treatment with non-thermal plasmas is by now a
well-established method for bacteria inactivation in medi-
cal and biological research and has been extensively inves-
tigated. As stated in the literature various plasma agents
and properties are responsible for the sterilisation effect. In
general, the main agents are: temperature, UV radiation,
reactive nitrogen and oxygen species (short RNS and ROS,
respectively) and short-lived charged particles. Although
the sterilizing agents can be defined, many researchers state
that the interaction effects between plasma and bacteria are
not fully understood. This may be due to insufficient or
missing plasma diagnostics. Furthermore, efforts to create a
large-area surface sterilisation by upscaling a non-thermal
discharge or stringing together several plasma jets had been
undertaken by various researchers. The stability and plasma
sheath homogeneity is one of the main concerns of such
systems. No literature which described the application of
thermal plasmas for bacteria inactivation on tempera-
ture-sensitive surfaces could be found.
The LARGE, a long arc plasma generator developed at
LPT, showed good suitability for large-scale surface treat-
ment of temperature-sensitive substrates as had been re-
ported in previous works. LARGE is a linear DC-plasma
source with an up to 450 mm long electrical arc discharge,
where the plasma gas is fed perpendicularly to the arc. The
arc is being stabilized by water-cooled cascades and a
magnetic barrier. Such a gas injection allows the generation
of thermal plasmas with different (also aggressive or oxida-
tive) gases. According to that, all main agents responsible
for plasma enhanced decontamination can be generated and
adjusted within a relatively wide range, and so the LARGE
should be used within this work.
Test setup
To show the suitability of thermals plasmas for bacteria
inactivation on temperature-sensitive surfaces a simple
two-step analysis method (screening and quantification)
have been applied. At first, tests with a dense bacteria layer
have been conducted to screen the parameters and deter-
mine the main influencing factors. Spores of Geobacillus
stearothermophilus ATCC 7953 have been used as they
appear to be particularly well suited for such an investiga-
tion. After the determination of the influencing factors,
disinfection rates have been determined by cell counting to
quantify the plasma effects. The results have been com-
pared with a commercially available non-thermal plasma
generator (Relyon Plasma PB3, Relyon Plasma GmbH,
Regensburg).
Results
The first tests with a dense microbal biofilm of geobacillus
endospores showed that a significant amount of spores could
be killed after just 60 s of treatment with the thermal plasma
generator LARGE. In comparison, a significant desactiva-
tion of the endospores could not be observed even after a
four times longer treatment of 240 s with the non-thermal
plasma generator Relyon Plasma PB3. Further, it could be
shown that the plasma carrier gas composition plays a key
role in sterilisation processes regardless of the used plasma
generator type. For thermal plasmas, a significant im-
provement in disinfection rates could be observed when
small amounts of nitrogen or oxygen were added to the
plasma gas (Ar). A similar percental arc current increase
also improved the kill rates, the positive effect was however
much lesser in comparison to gas composition change.
Hence, as the intensity of UV radiation is expected to in-
crease with rising current, UV is not the main killing
mechanism. Thermal degradation of the agar, which could
be partially observed after treatments with the non-thermal
plasma generator, could not be seen after LARGE treat-
ments. Although the estimated energy densities being in a
similar range, significantly lower gas temperatures when
using LARGE could be measured in the treatment distance
of 60 mm. Thus, heat seems not to be responsible for the
killing. The agents responsible for bacteria desactivation
seem to be RNS and ROS. As stated above, to quantify the
effects the disinfection rates have been determined with
diluted spore suspensions.
Conclusion
The investigation results show, that thermal plasmas can be
applied for large-area bacteria inactivation on tempera-
ture-sensitive surfaces. Furthermore, due to the wide range
of possible parameter adjustments, the long arc plasma
generator LARGE showed good potential for sterilisation
applications. The exact plasma agents responsible for bac-
teria inactivation remain to be explored in future work.
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Investigation of Inter-Electrodes Plasma Composition in Removal
of Oxide Layer from Steel Surface by Vacuum Arc S Iha
1*, M Sugimoto
1
1 Faculty of Systems Science and Technology, Akita Prefectural University
Introduction
Authors have investigated behavior of cathode spots re-
moving oxide layer on steel plate surface in vacuum arc
cleaning. The cathode spots have high density energy and
irregularly move around the steel plate surface served as
cathode. Therefore, the oxide layer on the surface is evap-
orated and can be removed [1]. Previous research reveals
that the cathode spots can exist not only on the side faced
to the anode (Figure 1 (a)) but also on the opposite surface
of the steel plate (Figure 1 (b)). When the cathode spots
are generated on the opposite side from the anode, a very
bright plasma is observed in inter-electrodes space as
shown in Figure 1 (b), although a dark plasma fills that
region when the cathode spots are on the side faced to the
anode. Conventionally, it is considered that the evaporated
cathode surface material by the cathode spots is ionized in
the inter-electrodes space in vacuum arc. Although it can
explain the existence of such plasma as shown in Figure 1
(a), there is no accounting for the phenomenon shown as
Figure 1 (b). In this study, the material in the in-
ter-electrodes plasma is captured and its composition is
investigated with elemental analysis by SEM-EDS.
(a) Cathode spots on the side faced to anode.
(b) Cathode spots on the opposite side to anode.
Figure 1: Photographs of cathode spots and inter-electrodes plasma in
removal of oxide layer from steel plate surface.
Experimental results
Figure 2 shows results of elemental analysis of the cap-
tured materials in the inter-electrodes plasmas of (a) Fig-
ure 1 (a) and (b) Figure 1 (b). Figure 2 (a) indicates that
the captured material is from the oxide layer on the steel
plate surface because the strong signals of iron and oxy-
gen are obtained. This result agrees with the conventional
explanation of the supplied cathode surface material by
the cathode spots. On the other hand, in the case of Figure
2 (b), the signal strength of oxygen becomes lower com-
pared to that of iron. This result implies that the cathode
surface material, which must be mainly iron in this case, is
supplied and ionized in spite of that no cathode spots are
on that surface of the steel plate.
(a)
(b)
Figure 2: Elemental analysis results of captured material in in-
ter-electrodes plasma.
Conclusion
The results imply that vacuum arc is sustained by com-
pletely different mechanism which has no relation with
the cathode spots, after the oxide layer removal of the side
faced to the anode is completed.
References
[1] Takeda K, Takeuchi S, 1997 Removal of Oxide Layer
on Metal Surface by Vacuum Arc, Material Transac-
tions, JIM, Vol. 38, No. 7, 636-642
HTPP14 Munich: Session 6, Poster S6-15
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HTPP14 Munich: Session 6, Poster S6-16
89
Influence of Powder Particles on the Plasma Characteristics in
Multi-arc Plasma Spraying K Bobzin
1, M Öte
1
1RWTH Aachen University, IOT - Surface Engineering Institute, Kackertstr. 15, 52072 Aachen, Germany
Introdution
All previous works, which have dealt with particle-plasma
interaction in plasma spraying, have in common that the
authors have employed different model simplifications to
explain certain aspects, mostly dealing with so-called
non-transferred conventional single-arc torches. A com-
prehensive numerical research focusing on plasma-particle
interaction in case of new generation multi-arc torches has
not been conducted yet. Therefore, this study focusses on
multi-arc plasma spraying of ceramic feedstock materials.
One of the major assumptions employed in numerical
works done so far is that influence of particles on the
plasma jet characteristics is negligible in plasma spraying
[1, 2]. The aim of this study is therefore to investigate this
effect and identify the validity of the above mentioned
assumption.
Mathematical Model and Boundary Conditions
Plasma exits the plasma generator at the nozzle outlet at
high temperatures and velocities. The set of equations
which are used for modelling the plasma jet outside the
plasma torch corresponds to the set of equations used for
plasma generator simulations with the exception of the
equations describing the electromagnetic phenomena. For
an overview, please refer to [3]. The calculation domain
involves the region downstream of torch outlet. The
boundary conditions at the nozzle outlet are imported
from a-priori conducted plasma generator simulations.
Opening boundary condition at the outer surface of the
calculation domain represents the flow behavior in the
infinity of the air atmosphere. Moreover, an inlet bounda-
ry condition over which powder particles are injected in
the calculation domain with defined mass flow rates, ve-
locities and size distributions has been defined.
Results and Discussion
In case of so called numerical approach “one-way cou-
pling”, only the influence of the fluid phase on the partic-
ulate phase is considered and the influence of the particu-
late phase on the fluid phase is neglected. On the other
hand, “two-way coupling”allows the particles to influence
the fluid phase via source terms of heat, momentum and
mass. The former is a common simplification used in lit-
erature and its justification is argued with that the rate of
particle injection is being too low in plasma spraying to
influence the plasma jet [2]. However, the results in this
work disprove this argumentation. In Figure 1, the results
of the simulations conducted with one-way and two-way
coupling is illustrated. The comparison is conducted for a
particle mass flow rate of 24 g/min pro injector, which is a
typical rate employed in plasma spraying for ceramic
feedstock materials. The results show that the particle in-
jection clearly reduces the plasma temperatures leading to
a slightly shorter plasma jet length. The calculated particle
velocities and temperatures are significantly influenced by
the change of the plasma gas temperatures.
Figure 1: Comparison of one-way and two-way coupling.
Acknowledgements
All presented investigations were conducted in the context
of the Collaborative Research Centre SFB1120 "Precision
Melt Engineering” at RWTH Aachen University and
funded by the German Research Foundation (DFG). For
the sponsorship and the support we wish to express our
sincere gratitude.
References
[1] Bobzin K, Kopp N, Warda T, Petkovic I, Zimmer-
mann S, Hartz-Behrend K, Landes K D, Foster G,
Kirner S, Marqués J-L, Schein J, Prehm J, Möhwald
K, Bach Fr-W, Improvement of Coating Properties in
Three-Cathode Athmospheric Plasma Spraying,
Journal of Thermal Spray Technology, 22 (4),
503-508
[2] Westhoff R, Trapaga G, Szekely J, Plasma-particle
interactions in plasma spraying systems, Metall.
Trans. B 23, 683-693
[3] Bobzin K, Bagcivan N, Zhao L, Petkovic I, Schein J,
Hartz-Behrend K, Kirner S, Marqués J-L, Forter G,
Modelling and diagnostics of multiple cathodes
plasma torch system for plasma spraying, Frontiers
of Mechanical Engineering, 6 (3)
HTPP14 Munich: Session 6, Poster S6-16
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HTPP14 Munich: Session 6, Poster S6-17
91
2-D temperature estimation in Ar-O2 induction thermal plasmas for
TiO2 nanopowder synthesis N Kodama
1*, K Kita
1, Y Ishisaka
1, Y Tanaka
1, Y Uesugi
1, T Ishijima
1, K Nakamura
2, S Sueyasu
2
1Faculty of Electrical & Computer Engineering, Kanazawa University, JAPAN
2Research Center for Production & Technology, Nisshin Seifun Group Inc., JAPAN
*[email protected],[email protected]
Introduction
To understand feedstock evaporation and nanoparticles
(NPs) nucleation processes is essential for controlling NPs
synthesis in the inductively coupled thermal plasma
(ICTP) torch. The authors found that it is possible to ob-
serve spatio-temporal distributions of Ti I and TiO radia-
tion intensities using a two-dimensional optical emission
spectroscopic (2-D OES) measurement system during TiO2
NPs synthesis [1]. This 2-D OES system consists of an
imaging spectrometers and a high speed video camera,
which can capture 2D images of spectral lines specified.
This paper describes the results of 2-D distribution of Ti
excitation temperature (TTi
ex) in the ICTP torch during
TiO2 NPs synthesis using the 2-D OES system because the
temperature is one of the important parameters for thermal
plasma processings. From these results, a possibility is also
discussed for TiO2 NPs nucleation in the torch.
Experimental conditions
The experimental conditions were similar to our previous
work [1]. In this work, the coil-current frequency was
315 kHz. Titanium powder feedstock was intermittently
injected into the ICTP torch with a solenoid valve. The
open and close times of the solenoid valve were 8 ms and
22 ms, respectively. The 2-D OES measurement region
was
set to 46×47 mm2 area below the coil-end. The 2D images
were observed of two different Ti I spectral lines at wave-
lengths of 453.32 nm (4s-4p) and of 521.04 nm (4s2-4s4p)
using the 2-D OES system. The wavelength resolution was
0.4 nm. The framerate of the high speed video camera was
3000 fps. From the 2-D OES results for two different Ti I
spectral lines, TTi
ex was determined using the two-line
method.
Results for temperature distributions in the torch Fig-
ure 1 illustrates the 2-D OES result of radiation intensity
of Ti I spectral lines.Both Ti I lines have strong intensities
around the center axis. From these observation results,
TTi
ex was determined without consideration of continuum
spectra for simplicity. Figure 2 (a) depicts 2-D distribution
of TTi
ex estimated in the ICTP torch. Region was illustrated
in black for temperatures below 2.5 kK and with low Ti I
radiation intensity. The estimated TTi
ex was between
2.5-4.0 kK around on-axis region and that was more than
4.0 kK in off-axis region. The lower temperature on the
axis arises from cooling effect from cool carrier gas injec-
tion and from energy consumption of feedstock
evaporation. In addition, the off-axis temperature could be
higher due to joule heating. Figure 2 (b) presents TiO radi-
ation intensity distribution observed in our previous work
[1]. From figure 2 (a) and (b), the 2-D low-temperature
region on the axis agrees well to the region with high radi-
ation intensities of TiO. This suggests that precursor TiO
molecules can be formed only around on-axis region. Fur-
ther, nucleation temperature of TiO2 nuclei was calculated
by homogeneous nucleation theory [2] as 2.6-2.8 kK.This
nucleation temperature was lower than TTi
ex estimated in
the ICTP torch. Thus, TiO2 NPs could be nucleated mainly
in the reaction chamber located downstream of the torch.
On the other hand, there is a region with low temperatures
below 2.5 kK and with high TiO radiation intensity at the
same time in the torch, where TiO2 nucleation can occur.
References
[1] Kodama N et al., 2015 ICRP-9/GEC-68/SPP-33,
FT4.00004
[2] Abraham F F, 1974 Homogeneous nucleation theory,
Academic Press, New York.
Figure 1: Ti I radiation intensities.
Figure 2: TTiex and TiO radiation intensity.
HTPP14 Munich: Session 6, Poster S6-17
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HTPP14 Munich: Session 6, Poster S6-18
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Anode surface structure influence on high current moving arcs in
atmosphere S Kirner
1*, G Forster
1, J Schein
1
1 Lab for Plasma Technology (LPT), Universität der Bundeswehr München, Munich
Introduction
High current moving arcs in atmosphere are present in
many industrial applications like welding, cutting and
thermal spraying. In all these systems the arc serves as heat
source in order to melt material. Especially the boundary
layers of the arc, with its high gradients of the electric field
and the temperature, are mainly responsible for the heat
flow to anode and cathode. In contrast to the cathode there
are still different theories concerning the boundary layer of
the anode. For example the amount and the polarity of the
anode fall voltage are not completely clarified. Assump-
tions like the negative anode fall voltage and the distribu-
tion of the anode fall voltage into a large anode drop volt-
age and a small voltage across the boundary layer are
proofed by many experimental and numerical studies. In
consideration of these observations the anode surface in-
fluence on high current moving arcs in atmosphere is in-
vestigated in this work. Especially the field enhancement
induced by micro peaks is a matter of particular interest.
Field enhancement simulation
The field enhancement factor β is estimated by approxi-
mating the surface structure as ideal peaks and simulating
the electric field in the vicinity using the software “femm”.
The example in Figure 1 shows the principle setup consist-
ing of a triangle and a straight electrode, whose dimensions
are determined with the help of roughness and REM meas-
urements. In addition the anode drop voltage Ua,d is meas-
ured using a Langmuir-probe.
Figure 4: Principle setup for the simulation of the electric field strength
consisting of a triangle and a straight electrode.
Experimental setup
For the investigations a water cooled copper plate with
2 mm tungsten layer is used as adapter for copper, alumi-
num and mild steel samples. Before moving an arc across
them, the samples are sandblasted with different grain sizes
to achieve certain surface roughness. During welding be-
sides the measurement of arc voltage and current high
speed stereo imaging is performed. In addition after shut-
ting down the arc the cathode surface temperature is deter-
mined using a two color pyrometer.
Results
For all materials and currents a direct proportionality be-
tween the simulated filed enhancement factors and the
measured arc voltages was determined.
For the investigation of the field enhancement influence on
the anode boundary a modified form of the Child-Langmuir
law solved for Ua,d is used (see Equation 1).
2/3
20,
0
9
4 2
a d s
mjU d
e (1)
By assuming a constant current density j, a constant voltage
drop across the boundary layer and a constant cathode fall
voltage, the anode drop voltage for β=1 can be calculated
using two arc voltages UB,1 and UB,2 measured at different
field enhancement factors (see Equation 2).
1
, ,2 ,1 2/3 2/32 1
1 1
a d B BU U U (2)
The field enhancement independence of the cathode fall
voltage could be proved by the measurement of same sur-
face temperatures at different β-factors. In addition the
calculated anode drop voltages are in good agreement with
the Langmuir-probe measurement.
Conclusion
In this work the influence of the surface structure on the
anode boundary of high current moving arcs in atmosphere
is investigated. For this purpose samples sandblasted with
different grain sizes are used as anode. In order to approx-
imate the expected field enhancement induced by the micro
peaks on the sample surface, an innovative method is ap-
plied. With the help of these values, the measured arc volt-
ages and a modified form of the Child-Langmuir law, the
anode drop voltages are calculated. Furthermore the as-
sumption of negative anode falls and the results calculated
with Equation 2 are proved by Langmuir-probe measure-
ments.
Acknowledgements
This work was supported by the DFG (Grant No. SCHE
428/10-1).
HTPP14 Munich: Session 6, Poster S6-18
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HTPP14 Munich
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Wednesday
HTPP14 Munich
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HTPP14 Munich: Session 7
97
What for high intensity discharge lamps are beneficial
in the age of LEDs J Mentel
Ruhr University Bochum, Electrical Engineering and Plasma Technology,44780 Bochum Germany
The design of high intensity discharge (HID) lamps de-
veloped up to the beginning of this century very rapidly.
To improve the emission spectrum of lamps the buffer
gas within the lamps, mercury or xenon, was seeded
with metal iodides, especially rare earth iodides. Higher
temperatures of the burner walls and with it higher metal
vapour pressures were realized by substituting quartz
burners for ceramic burners. By these measures the effi-
cacy of so called ceramic metal halide (CMH) lamps
operated with an AC or switched DC current was en-
hanced above 100 lm/W and the colour rendering above
90 CRI. Moreover the life time of CMH lamps was in-
creased above 104 h by a reduction of the operation
temperature of the tungsten electrodes within the lamps.
This is achieved by covering the electrode surface with a
dipole layer, which is formed by a monolayer of atoms
being electronegative with respect to tungsten. The layer
is formed by an ion current towards the electrode within
the cathodic half period in lamps seeded with special
metal iodides, e.g. thorium iodide or rare earth iodides.
This so called gas phase emitter effect is much more
effective in case of AC or switched DC operation than
the emitter effect generated by using doped tungsten
electrodes.
Simple CMH lamps are still in use for street lighting and
expensive versions in professional lighting systems
providing a high lumen output and a colour rendering
above 90 CRI. Other examples for HID lamps operated
in quartz tubes are so called xenon lamps for car head-
lights, also called D-lamps, ultra-high pressure mercury
lamps for video beamers and high power xenon short arc
lamps, which emit a luminous flux of several ten
k-lumen, e.g. for video projection, by a plasma spot in
front of the cathode.
HID lamps have some disadvantages. Thoriated elec-
trodes are subject of restrictions owing to the radioactiv-
ity of thorium, but it can be replaced quite easily with
other emitter materials, e.g. with rare earth metals. The
same applies to the popular but toxic buffer gas mercury.
It can also be substituted in most lamps for xenon. The
ignition of HID lamps may require some efforts, also the
generation of instant light, which is necessary for car
headlights. A challenge is dimming of HID lamps and a
control of their colour temperature. It can only be
reached by considerable efforts
Originally it was expected that CMH lamps will displace
in a next step incandescent and fluorescent lamps in res-
idential lighting. But in the middle of the nineties
Nakamura presented the first efficient blue LEDs based
on the research of Akasaki and Amano on GaN, which
were able to emit light in the wavelength region between
390-500 nm. This was the start signal for the develop-
ment of white light LED lamps. The result is two ver-
sions of white light LED lamps. In a less expensive one
with a moderate colour rendering the emission of a LED
in the near UV is transformed into white light by phos-
phors, which are already used in fluorescent lamps. In a
more expensive one white light with a better colour ren-
dering is generated with a combination of LEDs with
different colours, e.g. red, green and blue LEDs.
White light LEDs have clear advantages compared to
HID lamps. The efficacy is comparable to CMH lamp;
their lifetime is at least two times longer. Switching,
dimming and generation of instant light is uncomplicat-
ed. An instant change of the colour temperature is much
easier than in case of CMH lamps. On the other hand the
operation temperature of LED lamps is limited approxi-
mately to 1000C. Higher operation temperatures cause a
considerable reduction of the lamp efficacy and lifetime.
Therefore, at least a passive cooling of LED lamps is
required. It may be expensive for powerful LED lamps.
The maximum luminous flux, being generated by an
individual LED lamp is limited to values below 2000 lm.
However, this deficit can be compensated in many cases
by applying LED matrices.
Standard white light LED lamps are superior for resi-
dential lighting with moderate demands on colour ren-
dering. But in case of public lighting it is doubtful that
LED lamps are always a better solution. It depends on
the marginal conditions weather LED lamps or CMH
lamps offer a more appropriate solution in professional
lighting systems. In case of car head lights LED lamps
offer more adjustment options, but D-lamps a higher
efficacy at lower costs. The displacement of ultra-high
pressure mercury lamps may be difficult especially in
the case of a high power demand in spite of the devel-
opment of fluorescent ceramics which are excited with
UV semiconductor lasers. The substitution of high pow-
er xenon short arc lamps with a point shaped light emis-
sion by LEDs is quite unlikely in the near future.
HTPP14 Munich: Session 7
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State-of-the-art in the simulation of plasma-electrode interaction in
arc discharges M S Benilov
Departamento de Física, FCEE, Universidade da Madeira, Largo do Município, 9000 Funchal, Portugal
Instituto de Plasmas e Fusão Nuclear, IST, Universidade de Lisboa, Portugal
Significant advances have been achieved in recent years in
the modelling of plasma-cathode and plasma-anode inter-
action in high-pressure arc discharges and plasma-cathode
interaction in vacuum arcs. The aim of this work is to re-
view the numerical models developed and the most im-
portant results obtained.
A standard approach to simulation of cold plasmas is to use
a single set of equations, including the Poisson equation, in
the whole interelectrode gap, without a priori dividing the
computation domain into quasi-neutral plasma and
space-charge sheaths. However, such unified modelling is
highly computationally intense in the case of arc plasmas,
where the charge particle density is very high, space-charge
sheaths occupy only a tiny fraction of the computation do-
main, and the separation of charges in the bulk plasma is
very small. Therefore, works dedicated to modelling of
plasma-electrode interaction in arc discharges rely on ap-
proximate models. The exceptions are papers where the
above-described unified approach was used for 1D model-
ling of near-electrode regions which separate the electrodes
from the bulk of the arc where local thermodynamic equi-
librium holds; e.g., [1, 2].
Different approximate models available in the literature and
their physical basis are discussed in this work. Special at-
tention is paid to the account of near-electrode
space-charge sheaths and their matching to the qua-
si-neutral plasma. If the sheath if collisionless, the match-
ing is performed with the use of the Bohm criterion. Many
authors, including some recent ones (e.g., [3, 4]) employ
some or other version of the so-called collision-modified
Bohm criterion. However, the investigation of mathemati-
cal nature of the Bohm criterion [5] has revealed that the
classical Bohm criterion has a distinct mathematical inter-
pretation, while collision-modified criteria do not – there is
simply no sense in talking of a speed with which ions enter
a collisional sheath. Boundary conditions for equations
describing the quasi-neutral non-equilibrium plasma, which
account for collisionless space-charge sheaths, have been
derived in [6] and a numerical model of high-pressure arcs,
based on these boundary conditions, developed in [7]. Re-
sults of application of different models to simulation of
various modes of current transfer to cathodes of
high-pressure and vacuum arcs and of stability of these
modes are discussed.
An approximate approach to modelling the diffuse mode of
current transfer to anodes of high-pressure arcs was pro-
posed in [8]. Combining this approach with the unified 1D
modelling of near-anode layers (e.g., [1]) allows one to
develop a simple and free of empirical parameter model of
diffuse-mode operation of rod electrodes of high-pressure
arcs, including the anode and cathode dc regimes and ac
regimes.
The work was supported by FCT of Portugal through the
project Pest-OE/UID/FIS/50010/2013.
References
[5] Almeida N A, Benilov M S, Hechtfischer U, and Naidis
G V, 2009 Investigating near-anode plasma layers of
very high-pressure arc discharges J. Phys. D: Appl.
Phys. 42 045210
[6] Semenov I L, Krivtsun I V and Reisgen U, 2016 Nu-
merical study of the anode boundary layer in atmos-
pheric pressure arc discharges J. Phys. D: Appl. Phys.
49 105204
[7] Pekker L and Hussary N, 2014 Effect of boundary
conditions on the heat flux to the wall in
two-temperature modeling of ‘thermal’ plasmas J.
Phys. D: Appl. Phys. 47 445202
[8] Pekker L and Hussary N, 2015 Boundary conditions at
the walls with thermionic electron emission in two
temperature modeling of “thermal” plasmas Phys.
Plasmas 22 083510
[9] Almeida N A and Benilov M S, 2012 Physics of the
intermediate layer between a plasma and a collisionless
sheath and mathematical meaning of the Bohm crite-
rion, Phys. Plasmas 19, 073514
[10] Benilov M S, Almeida N A, Baeva M, Cunha M D,
Benilova L G and Uhrlandt D, 2016 Account of
near-cathode sheath in numerical models of
high-pressure arc discharges J. Phys. D: Appl. Phys. 49
215201
[11] Baeva M, Benilov M S, Almeida N A and Uhrlandt D,
2016 Novel non-equilibrium modelling of a dc electric
arc in argon J. Phys. D: Appl. Phys. 49 245205
[12] Luijks G M J F, Nijdam S and v Esveld H, 2005 Elec-
trode diagnostics and modelling for ceramic metal
halide lamps J. Phys. D: Appl. Phys. 38 3163
HTPP14 Munich: Session 7
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HTPP14 Munich: Session 8
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Plasma Medicine – innovative physics for medical application K-D Weltmann
1, T von Woedtke
2
1 + 2 Leibniz Institute for Plasma Science and Technology(INP Greifswald), Greifswald
Plasma medicine means the direct application of cold at-
mospheric plasma (CAP) on or in the human body for
therapeutic purposes. Experimental research as well as first
practical application is realized using two basic principles
of CAP sources: Dielectric Barrier Discharges (DBD) and
Plasma Jets [1].
Figure 1: Plasma sources suitable for therapeutic applications: BDs and
plasma jets.
An interdisciplinary research approach bringing together
plasma physics and technology on the one side and life
sciences and medicine on the other was the basis for excel-
lent progress to achieve a sound and reputable scientific
basis of plasma medicine which will be further consolidat-
ed. Originating from the fundamental insights that biologi-
cal effects of CAP are significantly caused by changes of
the liquid environment of cells, and are dominated by re-
dox-active species, mechanisms of biological plasma activ-
ity are identified and it was demonstrated that the risk of
cold plasma application is low, assessable, and manageable
[2]. Mainly based on both the very effective inactivation of
a very broad spectrum of microorganisms by CAP and its
ability to stimulate proliferation of mammalian cells, the
main focus of clinical application is in the field of wound
healing and treatment of infective skin diseases, yet [3]. A
few CAP sources are CE certified as medical devices now
with the kINPen Med as the first cold atmospheric-pressure
plasma jet for therapeutic purposes [4].
Figure 2: left: Atmospheric-pressure plasma jet (kINPenMED, neoplas
tools GmbH) for experimental biomedical applications (right: schematic
set-up).
Actually, application for cancer treatment becomes a more
and more important research field in plasma medicine.
Other potential medical fields are in dentistry, ophthalmol-
ogy, plastic and aesthetic surgery, but also endoscopy.
Therefore, a further in-depth knowledge of control and
adaptation of plasma parameters and plasma geometries is
needed to get suitable and reliable plasma sources for the
different therapeutic indications.
References
[1] K-D Weltmann, E Kindel, Th von Woedtke, M Hähnel,
M Stieber, R Brandenburg, 2010 Atmospheric-pressure
plasma sources: Prospective tools for plasma medicine.
Pure Appl. Chem. 82, 1223-1237
[2] Th von Woedtke, S Reuter, K Masur, K-D Weltmann,
2013 Plasmas for medicine. Phys. Rep. 530, 291-320
[3] Th Von Woedtke, H-R Metelmann, K-D Weltmann,
2014 Clinical Plasma Medicine: State and Perspectives
of in Vivo Application of Cold Atmospheric Plasma
Contrib. Plasma Phys. 54, 104 – 117
[4] S Bekeschus, A Schmidt, K-D Weltmann, Th von
Woedtke, 2016 The plasma jet kINPen – A powerful
tool for wound healing. Clin. Plasma Med.
http://dx.doi.org/10.1016/j.cpme.2016.01.001
HTPP14 Munich: Session 8
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Atmospheric pressure plasma sources: from laboratory and publi-
cation to real applications and industrial production S S Asad
1
1 Plasmatreat GmbH, Bisamweg 10, 33803 Steinhagen, Germany
General
Atmospheric pressure plasma sources have been around for
many years and subject to intensive research, given the
possibility of using them in open environments, which is
not possible with their low pressure counterparts. The de-
velopment of different types of sources and different pro-
cesses has led to a large number of sources, and innumera-
ble applications and potential applications. Plasmas are a
rich source of active species and energy, which allows them
to exhibit unique capacity of modifying the matter they
come in contact with. Therefore, plasmas can be used in-
tensively used to modify surfaces physically and chemical-
ly for different applications like bonding and adhesion, fine
cleaning of the surfaces from existing organic molecules,
charging or neutralize surfaces and particles, disinfecting
and sterilizing of different surfaces and materials, welding
of different metals, chemically decompose precursor mate-
rials and make them react on a surface to form coatings, or
as a thermal source for spraying the powder coatings on a
substrate, and list goes on. However, the industry is still on
the way of accepting different processes as standard.
In this presentation we would go through an overview of
different existing atmospheric pressure plasma sources and
the resulting processes and their applications. The ad-
vantages/disadvantages presented by atmospheric pressure
plasma sources compared to their low pressure counterparts
for industrial processes are detailed and the ways to over-
come these disadvantages. Special attention would be given
to the coating processes specially the ones that are being
currently of great interest to the industry.
Acknowlegements
The author is thankful to his R&D team of Plasmatreat and
C. Buske, CEO, Plasmatreat GmbH.
HTPP14 Munich: Session 8
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Direct decarbonization of methane by thermal plasma for the co
synthesis of carbon black and hydrogen L Fulcheri
*, M Gautier, V Rohani
MINES ParisTech, PSL - Research University, PERSEE - Centre procédés, énergies renouvelables
et systèmes énergétiques, 1 Rue Claude Daunesse, 06904 Sophia Antipolis, France
General
In the present context of fossil fuel depletion, global
warming and other major environmental impacts, the ener-
gy sector definitively remains one of the most critical. The
future of humanity will certainly depend on our ability,
during the next fifty years, to develop new original, sus-
tainable and environmental friendly solutions in the field of
energy. In the perspective of large scale deployment of Re-
newable Energy for electricity production, plasma process-
es could open the way towards new breakthrough original
family of environmental friendly processes likely to answer
tomorrow’s challenges. Indeed, plasma can favorably act as
a robust tunable enthalpy source without direct CO2 emis-
sions as well a radical, excited or ionized species source,
able to significantly improve the reactivity of number of
chemical reactions. This presentation will particularly focus
on the direct decarbonization of methane for the co synthe-
sis of Carbon Black and hydrogen. The economic viability
of the process relies on the ability to simultaneously pro-
duce hydrogen and high added value carbon black having
well-controlled characteristics, particularly concerning the
particle size. After a comprehensive review of gas phase
carbon particles nucleation and growth phenomena, a mod-
el for the study of carbon particle size distribution during
allothermal cracking of methane is presented.
History
First publications on the production of CB in an electric arc
process date back to 1920 by Rose [1]. These publications
were followed by many publications and patents in the
1960s. In the 1990s the engineering company Kvaerner
investigated intensively a direct current (dc) technology for
the industrial production of CB and hydrogen at the pilot
scale. Major technological challenges were addressed and
eventually, the technology using the hydrogen co-product
directly as plasma gas reached a development stage, where
commercial feasibility seems to be proven [2]. Unfortu-
nately, the industrial facility, with an annual capacity of
20000 tons of CB and 70 million normal cubic meters of
hydrogen constructed in Canada in 1999, never went into
successful industrial operation as apparently a number of
parameters could not be transferred from the laboratory to
the pilot scale. Meanwhile many research groups, including
Fulcheri et al [3, 4] have dedicated their efforts to the study
of complementary processes investigating a multitude of
plasma configurations and operating conditions.
Gas phase nucleation and growth
The CFD model presented in this study takes into account:
heat transfer by conduction, convection, particle and gas
radiation, homogeneous and heterogeneous reactions of
methane dissociation, and nucleation and growth of solid
carbon particles. The nucleation model is related to a sim-
plified PAH (Polycyclic Aromatic Hydrocarbons) for-
mation and growth up to a critical size [5] from where nu-
clei evolve toward solid macroscopic particles by the
means of chemical surface growth [6] and physical coales-
cent coagulation [7]. Since large uncertainties remain con-
cerning kinetic parameters for plasma conditions, a para-
metric study is developed in order to see the influence of
the nucleation rate versus the heterogeneous reaction rate
on the particle size distribution at plasma temperature con-
ditions.
References
[1] J R Rose, 1920 Process of and apparatus for producing
carbon and gaseous fuel US Patent 1,352,085, 1920
[2] B Gaudernack and S Lynum S Hydrogen from natural
gas without release of CO2 to the atmosphere Int. J.
Hydrog. Energy 23 1087, 1998
[3] L Fulcheri and Y Schwob From methane to hydrogen,
carbon black and water. 1995 Int. J. Hydrogen Energy,
vol. 20, n° 3, p. 197-202
[4] L Fulcheri et al. Plasma processing: a step towards the
production of new grades of carbon black. Carbon, 40,
p. 169-176
[5] M L Botero, D P Chen, S Gonzalez-Calera, D Jefferson,
M Kraft, 2016 HRTEM evaluation of soot particles
produced by the non-premixed combustion of liquid
fuels, Carbon, 96 459-473
[6] M Frenklach, H Wang, Detailed Mechanism and
Modeling of Soot Particle Formation, in: H. Bockhorn
(Ed.) Soot Formation in Combustion: Mechanisms and
Models, Springer Berlin Heidelberg, Berlin, Heidelberg,
1994, pp. 165-192
[7] S K Friedlander, Smoke, Dust, and Haze: Fundamentals
of Aerosol Dynamics, Oxford University Press2000
HTPP14 Munich: Session 8
106
HTPP14 Munich: Session 9, Poster S9-1
107
Double-Sided Ion Thruster for Contactless Space Debris Removal M Dobkevicius1*, D Feili2, M Smirnova3, A M Perez3
1University of Southampton, 2ESTEC (ESA),
4TransMIT Gmbh,
Introduction
LEOSWEEP mission proposes to de-orbit a 1.5-ton
launcher upper stage from a nearly polar Low Earth Orbit
(LEO) in 170 days using the Ion Beam Shepherd (IBS)
method proposed by Bombardelli [1]. The IBS method is
a contactless space debris removal concept where the
momentum to the debris is imparted by high-energy col-
limated neutralized plasma beam produced by the Impulse
Transfer Thruster (ITT). To compensate for the thrust
produced by the IT thruster, a second Impulse Compensa-
tion Thruster (ICT) is also required. The LEOSWEEP
project team plans to use a radio-frequency (RF) thruster
for the IT due to its capability to produce a low divergence
beam, which was shown to greatly increase the momen-
tum transfer efficiency. Nevertheless, the most optimum
thruster option for the IC has not been chosen yet. We
propose a novel thruster concept for the LEOSWEEP mis-
sion where, instead of the proposed two-thruster design, a
single double-sided thruster simultaneously producing two
ion beams is used as shown in Figure 1.
Figure 1. Double-sided ion thruster concept geometry.
The beam from one side of the thruster is used for the IT,
while the beam from another side is employed for IC. The
advantage of such a design is that it requires two times
less RF power than two single-ended thrusters. Addition-
ally, it is expected that such a system would have a much
simpler sub-system architecture, lower cost, and lower
total mass. The double-sided thruster has been designed
using the computational tools developed by the authors. It
was shown that the screen voltage of 3 kV results in the
lowest total power. Simulations indicate that the thruster
should be comparable if optimized, to a system of two
single-sided RF ion thrusters that need around 2.5 kW of
power and approximately 30 kg of fuel for the duration of
the LEOSWEEP mission as illustrated in Table 1.
Table 1: Different propulsion system combinations for the LEOSWEEP
mission.
ITT
ICT Total
power
(W)
Total propel-
lant
mass (kg)
LEOSWP. Double-sided 2840 21
LEOSWP. LEOSWP. 2928 30
LEOSWP. RIT 15 2531 29
LEOSWP. SPT-70 2050 47
LEOSWP. NEXT 2350 38
The thruster has been designed and built, with the testing
campaign planned to start shortly at a newly built vacuum
facility at the University of Southampton. We aim to pre-
sent the methodology behind the design of the thruster and
the final thruster geometry at the conference. Additionally,
we want to present the preliminary test results with re-
gards to the thruster performance and, if possible, plasma
parameter measurements. For the concept to work, The
FIC thrust must be about 30% larger than the FIT thrust.
Therefore, the main goal of the test campaign is to vali-
date the concept and to confirm whether different thrust
magnitudes can be extracted from each end of the thruster.
This is challenging because the plasma voltage, controlled
using a single beam power supply, is common to both ex-
traction sides with respect to the ground. The initial plan is
to adjust the number of apertures so that 30 % larger beam
current can be extracted from one side of the thruster. The
extracted beam current can also be adjusted by modifying
the plasma sheath shape in front of the grids. This can be
done by manipulating the negative power supply voltages.
References
[1] Bombardelli C, Peláez J, 2011 Ion Beam Shepherd for
Contactless Space Debris Removal Journal of Guid-
ance, Control and Dynamics, vol. 34, no. 3, pp.
917-920
HTPP14 Munich: Session 9, Poster S9-1
108
HTPP14 Munich: Session 9, Poster S9-2
109
2
Parasitic capacitances in DBD tranformerless power supply:
an issue? M A Diop
1, A Belinger
1*, J M Blaquiere
1, H Piquet
1
1 LAPLACE, Université de Toulouse, CNRS, INPT, UPS, France
2 rue Charles Camichel BP 7122, 31071 TOULOUSE Cedex 7
From an electrical point of view, cold plasmas are com-
plex loads to control. This is because, for ignition, high
voltages are required, and once established at atmospheric
pressure, the plasma can easily go into the arc regime
(thermal plasma). In Dielectric Barrier Discharge (DBD)
setups, at least one dielectric is placed between the two
metal electrodes that supply the gas. The capacitive char-
acter of the dielectric barriers limits the current and there-
fore prevents it from going into the arc regime. This prop-
erty makes the DBD particularly appealing in various ap-
plications that require the use of plasmas with low tem-
peratures: UV excimer lamps, thin film deposition and
surface treatment, controls of flows and disinfection. Fur-
thermore, to ignite the discharge at atmospheric pressure,
the applied voltage usually reaches several kilovolts. This
high alternating voltage is traditionally obtained via am-
plification using a step-up transformer. Unfortunately, the
parasitic elements of the transformer (leakage inductance,
inter-turn and inter-winding parasitic capacitance) specific
to the physical structure of this equipment limit the power
transfer: parasitic capacitance has generally low values but
often are of the same order of magnitude as those of the
DBD. It is parallel to the DBD, so it diverts a significant
proportion of the current transferred to the DBD device. It
slows down the voltage rise and delays the ignition of the
discharge. Thus, the plasma remains OFF during a higher
percentage of the operating period.
During this OFF time, the excited species created by the
previous discharge disappear. In some processes the de-
crease of the number of these species change the behavior
of the discharge. As a matter of fact, the main conse-
quences of the parasitic capacitance of the transformers
concern the functioning of the discharge and not the ener-
getic efficiency of the system.
Improving these performances incited us to investigate
power supplies for DBD without transformer. The solution
is to directly connect a high-voltage inverter to the DBD.
This involves using high-voltage switches. To our
knowledge, only theoretical developments have been
proposed to date [1], because high-voltage switches have
only been available for a few years. In this study, several
switch solutions are evaluated and tested experimentally:
10 kV SiC power DMOSFETs designed by CREE
Low voltage (1700 V) power MOSFET in series
High voltage power MOSFET in series
Using these devices, an innovative transformerless
pulsed-current source topology (Figure 1) is proposed and
will be detailed. We will analyze all the parasitic capaci-
tances presented in Figure 1 and highlight their impact on
the quality of the power transfer. In the proposed topology,
the largest parasitic capacitances (switches) are isolated
from the DBD by an inductance. So they do not affect the
OFF time and the behavior of the discharge. However,
they can produce some oscillations when all the switches
are open. This is not a real problem but should be noticed.
Figure 1: Power supply and DBD electrical model with parasitic capac-
itances (arrows indicate the variability)
The main issue is in fact related to the efficiency of the
supply: indeed, parasitic capacitances (Coss) of the switch-
es hold a high voltage and so a high energy before
switching (1/2. Coss.VMOS ). This energy is integrally dissi-
pated in the MOSFET at turn ON. These losses depend
only on the voltage sustained by the switch (for a given
Coss value). When the converter transmits high power,
these losses are acceptable; however, when the power in-
jected into the DBD decreases, the efficiency of the con-
verter decreases significantly. For low power, the best way
is to decrease the global capacitance of the switches.
10 kV switches are currently designed for high current
application (switch currents up to 10 A): their parasitic
capacitances are high (Coss=150 pF). Thus, the only solu-
tion is the use of series connected MOSFETs. It allows
naturally to decrease the equivalent capacitance but re-
quires an accurate voltage balance.
The design of high voltage converter without transformer
is not an obvious process. We highlight the main negative
effects caused by the parasitic capacitances on the DBD
and on the converter, and we propose a set of solutions in
order to reduce these issues.
References
[1] El-Deib A, Dawson F, Zissis G, 2011 Transform-
er-less current controlled driver for a dielectric barrier
discharge lamp using HV silicon carbide (SiC)
switching devices Energy Conversion Congress and
Exposition (ECCE) IEEE, 1124-1131, 17-22 Sept.
2011
HTPP14 Munich: Session 9, Poster S9-2
110
HTPP14 Munich: Session 9, Poster S9-3
111
Optical emission spectroscopic study of CH4 plasma during the
production of graphene by induction plasma synthesis
A Mohanta,* B Lanfant, M Asfaha, M Leparoux
EMPA–Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Advanced Materials Processing,
Feuerwerkerstrasse 39, 3602 Thun, Switzerland
Inductively coupled RF thermal plasmas have been re-
ceived increasing attention due to various applications in
materials processing [1]. In recent years, high purity ul-
trafine powders have been synthesized by inductively
coupled thermal plasma. In this study, we have synthe-
sized graphene using inductively coupled plasma (ICP)
and powder synthesis system which consists of an ICP
torch, a synthesis chamber, a filtration unit and a precur-
sor injector. More details about the synthesis system can
be found elsewhere [2]. The 13.56 MHz ICP torch is
mounted on the top of the synthesis chamber and is oper-
ated with argon and hydrogen up to a maximum input
power of 35 kW. The methane gas was introduced into
the plasma by the injector mounted axially on the central
position of the torch at the height of the first induction
coil. In this experiment, the power and pressure were
varied from 12 to 18 kW and 400 to 700 mbar, respec-
tively. The main objective of the study was to compara-
tively investigate the Ar/CH4/H2 thermal plasma and the
synthesized Graphene powder. The thermal plasma was
investigated by optical emission spectroscopy (OES) us-
ing a fiber coupled spectrometer (Ocean Optics) moni-
tored through a view port. The synthesized graphene
powder was characterized by transmission electron mi-
croscopy (TEM), Raman Spectroscopy and x-ray diffrac-
tion. The production rate was determined by weighing the
synthesized powder after growth. Figure 1 shows the op-
tical emission spectra of Ar/CH4/H2 thermal plasma in the
spectral range of 350 to 700 nm obtained at 18 kW and
700 mbar. The Y-axis is in the logarithmic scale. The inset
shows the same spectrum with Y-axis in linear scale. It
contains several emissions at 359.2 nm, 388.7 nm,
406.2 nm, 431.1 nm, 437.7 nm, 472.5 nm, 516.7 nm,
563.5 nm, 612.2 nm, 619.5 nm, and 656.3 nm which are
represented by a–k in the spectrum (Figure 1). We have
assigned the observed emissions based on their spectral
positions. The spectrum is dominated by the optical emis-
sion from C2 swan band (e, f, g, h, j). The bands e, f, g, h,
and j corresponds to the Δυ = +2, +1, 0, -1, -2 vibration
sequences of the (d3g-a
3u) electronic transitions. In
addition, the emissions a, b, c, d, i, and k corresponds to
C2, CH B-X (2 -
2) C3, CH A-X (
2
2), H2 and Hα
transitions, respectively [3]. The appearance of Hα emis-
sion indicates the formation of atomic hydrogen due to
the decomposition of CH4 and H2. Decomposition of CH4
further results the formation of hydrocarbon species C2H2
which produces C2 dimers under the influence of the Ar
gas. In the spectral region from 350 to 700 nm, Ar plasma
emissions are not observed. Figure 2(a) shows the emis-
sion spectra with fixed power of 15 kW at varying pres-
sures. At lower pressures, the plasma species propagate
with less obstruction. So, the plasma species remain
highly energetic. As the pressure increases, the highly en-
ergetic thermal plasmas collide with the species of the
ambient resulting in rapid cooling of the plasma that leads
to the chemical reaction and formation of nano-powder.
Thus, no powder is formed at lower pressure of 400 mbar
at 15 kW since thermal plasma is not sufficiently cooled
for condensation which can be envisaged from figure 2
(a). However, with increase in pressure, the production
rate increases and is 1.1 g/h at 700 mbar at 15 kW.
Moreover, as the input power increases from 12 to 18 kW
at 700 mbar, the plasma emission intensity increases as
shown in figure 2(b) due to reduction in cooling rate
which encumbers the formation of nano-powder and de-
creases the production rate from 2.4 to 0.8 g/h. More de-
tailed correlation between OES and the properties of
synthesized graphene powder will be presented at the
conference.
Figure 1: Plasma emission spectra.
Figure 2: Emission spectra (a) at 15 kW at different pressures, (b) at
700 mbar at different input powers.
References
[1] Reed T B, 1961 Induction–Coupled Plasma Torch J.
Appl. Phys. 32 821
[2] Shin J W, Miyazoe H, Leparoux M, Siegmann St,
Dorier J L, Hollenstein Ch, 2006 The influence of
process parameters on precursor evaporation for alu-
mina nanopowder synthesis in an inductively coupled
rf thermal plasma Plasma Sources Sci. Technol.15
441
[3] Zhou H, Watanabe J, Miyake M, Ogino A, Nagatsu M,
Zhan R, 2007 Diamond & Related Materials 16 675
HTPP14 Munich: Session 9, Poster S9-3
112
HTPP14 Munich: Session 9, Poster S9-4
113
Design oriented modelling for the synthesis process of copper na-
noparticles by a radio-frequency induction thermal plasma system S Bianconi
1, M Boselli
1,2*, V Colombo
1,2, E Ghedini
1,2, M Gherardi
1,2
1Department of Industrial Engineering
2Industrial Research Centre for Advanced Mechanics and Materials
Alma Mater Studiorum-Università di Bologna, Via Saragozza 8, Bologna 40123, Italy
Radio-frequency inductively coupled plasma (RF-ICP)
technology has proven to be a viable means for continuous
production of nanoparticles (NP), thanks to its distinctive
features, such as high energy density, high chemical reac-
tivity, high process purity, large plasma volume, precur-
sors long residence time and the high cooling rate (104–
105 Ks
−1) in the tail of the plasma, and its large number of
process variables, e.g. frequency, power, process gases,
phase of the precursor and system geometry [1]. Nonethe-
less, this high versatility comes at a price, as process op-
timization (in terms of yield and size distribution of the
NP) is a challenging process that can hardly rely on try
and fail experimental approaches due to equipment costs
and to the limited amount of information that can be ob-
tained from conventional diagnostic techniques. Therefore,
process optimization of the NP synthesis process in
RF-ITP systems has to rely extensively on modelling
techniques [2-3].
In this work, we report on design-oriented modelling for
the optimization of an RF-ICP synthesis process of Cu NP
starting from a solid precursor. In particular, the effect of
i) the geometry of the reaction chamber (the volume
downstream the plasma source, where NP are formed and
grow) and of ii) the quenching strategy (injection of gas in
the reaction chamber that affects flow fields, temperature
distributions, cooling rates and particle deposition at the
chamber walls, which must be minimized) will be inves-
tigated. The adopted simulative model can describe plas-
ma thermo-fluid dynamics, electromagnetic fields, pre-
cursor trajectories and thermal history (Figure 1), and na-
noparticle nucleation and growth [4]. Radiative losses
from Cu vapour and their effect on the precursor evapora-
tion efficiency have also been taken into account in the
model.
Acknowledgements
Work supported by European Union’s Horizon 2020 re-
search and innovation programme under grant agreement
No 646155 (INSPIRED project).
Figure 1: Temperature field for different reaction chamber geome-
tries.
References
[1] Boulos M I, 1996 New frontiers in thermal plasma
processing Pure Appl. Chem. 5 681007
[2] Gonzalez N Y M, Morsli M E, Proulx P, 2008 Pro-
duction of nanoparticles in thermal plasmas: a model
including evaporation, nucleation, condensation, and
fractal aggregation J. Therm. Spray Technol. 17 533
[3] Shigeta M, Watanabe T, 2007 Growth mechanism of
silicon-based functional nanoparticles fabricated by
inductively coupled thermal plasmas J. Phys. D:
Appl. Phys. 27 946
[4] Colombo V, Ghedini E, Gherardi M, Sanibondi P,
2012 Modelling for the optimization of the reaction
chamber in silicon nanoparticle synthesis by a ra-
dio-frequency induction thermal plasma Plasma Sci.
Technol 21 055007
HTPP14 Munich: Session 9, Poster S9-4
114
HTPP14 Munich: Session 9, Poster S9-5
115
Plasma of Electric Arc Discharge in Air with Silver Vapours V F Boretskij
1, Y Cressault
2*, P Teulet
2, A N Veklich
1
1 Taras Shevchenko Kyiv National University, Radio Physics, Electronics and Computer Systems Faculty,
64, Volodymyrs'ka Str., Kyiv, 01033, Ukraine 2 LAPLACE (Laboratoire Plasma et Conversion d'Energie), Université de Toulouse; CNRS, UPS, INPT; 118 route de
Narbonne, F-31062 Toulouse, France
The electric arc between evaporated electrodes has diverse
technological applications. It is well known that electrode
vapours have a determining influence on properties of arc
plasma. The insignificant impurity (about 1 %) of elec-
trode metal vapour appreciably changes plasma parame-
ters of the discharge in a rather wide temperature range [1].
Unfortunately, the influence of different metal impurity on
the plasma of electric arc discharge in air is not experi-
mentally investigated in detail yet.
The main aim of this study is an investigation of metal
vapour influence on plasma parameters as well as on
transport properties of arc discharge in air between silver
electrodes.
The arc was ignited in air between the end surfaces of
non-cooled silver electrodes. The diameter of rod elec-
trodes was 6 mm, the discharge gap was 8 mm, and the
arc current was 30 A. Optical emission spectroscopy
(OES) techniques were used for determination of plasma
parameters. The radial temperature profiles T(r) in plasma
were obtained from intensities of Ag I spectral lines by the
Boltzmann plot technique using previously selected spec-
troscopic data [2]. The radial profiles of electron densities
Ne(r) were determined from the width of Ag I 447.6
or/and 466.8 nm spectral line[3].
The obtained electron density and temperature in plasma
as initial data were used for simplified calculation of
plasma composition in the assumption of local thermody-
namic equilibrium (LTE) [2]. The number densities of
particles are obtained by solution of the equations system.
Those equations are the classical equilibrium laws: disso-
ciation, ionisation, conservation of the neutrality and per-
fect gas.
On the next stage, the obtained silver content in plasma
was used in the calculation of more detailed plasma com-
position as well as thermodynamic and transport proper-
ties. Composition of air-silver plasma was calculated by
the minimization of the Gibbs free energy, assuming LTE.
Then, based on the results of compositions, the thermo-
dynamic properties (including mass density, specific en-
thalpy, and specific heat) were determined.
The collision integrals between each species in the mix-
tures were calculated to obtain the transport coefficients
(i.e. electrical conductivity, viscosity, and thermal conduc-
tivity).
So, the radial profiles of thermal and electrical conductiv-
ity of plasma in arc discharge in air are determined. The
calculations were provided with taking into account of
silver admixture and without it. It was found that thermal
conductivity is not sensitive to silver presence in experi-
mental plasma temperature range at discharge current
30 A. Contrary to this transport coefficient, the electrical
conductivity of plasma is wholly determined by silver
impurity.
As conclusion, it must be noted that experimental investi-
gation by OES techniques allowed obtaining metal atom
concentration in plasma of electric arc in air between sil-
ver electrodes. The real thermal and electrical conductivi-
ty radial profiles of such plasma mixtures were calculated
in detail. It was found that the silver admixture has almost
no influence on the thermal conductivity of Ag-air plasma
in experimental temperature range 4000 K<T<10000 K.
The electrical conductivity of such mixtures strongly de-
pends on silver content in plasma.
Acknowledgements
This work was supported by joined project “Dnipro” in
the frame of research and technology collaboration be-
tween Ukraine and France.
References
[1] Gleizes A, Gonzalez J J, Freton P, 2005 J. Phys. D:
Appl. Phys., 38, R153–R183
[2] Babich I L, Boretskij V F, Veklich A N, and Se-
menyshyn R V, 2014 Advances in Space Research,
54, 1254-1263
[3] Dimitrijevic M S, Sahal-Brechot S, 2003 Atomic Data
and Nuclear Data Tables, 85, 269-290
HTPP14 Munich: Session 9, Poster S9-5
116
HTPP14 Munich: Session 9, Poster S9-6
117
Optical study of anode phenomena in vacuum switching arcs D Uhrlandt
1*, A Khakpour
1, S Gortschakow
1, R Methling
1, St Franke
1, K-D Weltmann
1, S Popov
2, A Batrakov
2,
1Leibniz-Institute for Plasma Science and Technology, 17489 Greifswald, Germany
2Institute of High Current Electronics, Russian Academy of Sciences, Tomsk 634055, Russia
Introductiom
High current vacuum interrupters are usually applied at
medium voltage. Application at high voltage is also desir-
able but needs further research and development. Contact
erosion and failure recovery depend among others on an-
ode phenomena which occur at the transition from low to
high current in the vacuum arc. Three kinds of anode dis-
charge modes are observed at high current; footpoint, an-
ode spot, and intense mode. Its occurrence is affected be-
side the current value by current waveform, contact speed,
gap geometry, and contact material. The transition to high
current anode modes is accompanied typically by abrupt
changes in the electrical characteristics of the arc, in the
light emitted by the region near the anode, as well as in the
anode surface temperature. Its formation may be triggered
by vapor emission from the anode and by magnetic con-
striction effects which lead to sudden changes of the ion
density in the region near the anode. This work is focused
on detailed studies of atom and ion radiation during
high-current anode modes which was still missing so far.
Experiments
An ultrahigh vacuum chamber with basic pressure of
about 2*10-8
mbar and an electrode system connected
with a mechanical-pneumatic actuator for the electrode
separation are used to simulaten early realistic conditions
of high-current vacuum interrupters. Constant opening
velocities can be chosen between 1 to 4 m/s dependent on
the pressure in the actuator. The maximum electrode dis-
tance is about 20 mm. The delay between electrode sepa-
ration and current can be adjusted freely with a total jitter
below 100 μs. Sinusoidal alternating currents at 50, 180
and 260 Hz as well as DC pulses of 5 and 10 ms with
peak currents up 6 kA are generated by apower source
consisting of LC elements, a triggerable spark gap,
charging and control units. Arcs between cylindrical
electrodes made of Cu, CuCr50, and CuCr7525 with di-
ameters of 10, 20, and 25 mm are studied in this work.
The arc current is measured by a Pearson current monitor,
the arc voltage by a capacitive-resistive voltage divider
and a voltage probe.Two viewports of the vacuum cham-
ber allow optical observation of the arc by a high speed
camera (IDT-MotionPro Y4) with recording speed of
10000 fps as well as by a 0.5 m spectrograph connected
also with a high speed camera to realize video spectros-
copy. Here, the inter-electrode gap and parts of the elec-
trodes are imaged to the entrance slit of the spectrograph
by means of a long distance microscope. The 2D-images
contain spectral as well as spatial information along the
arc axis with a spectral resolution of about 0.05 nm and
are recorded with a typical exposure time of 200 μs and
2000 fps.
Results
The different high-current anode modes are identified by
its characteristic voltage courses as well as the light emis-
sion near the anode (see Figure 1). Their existence regions
in the parameter space of current and gap distance have
been deduced depending on electrode diameters, materials,
separation velocities and current wave forms. The typical
time behavior and axial distribution of copper line intensi-
ties have been obtained from the video spectroscopy for
several Cu I lines, Cu II lines and Cu III lines. An abrupt
change in the axial distribution of Cu III lines occurs dur-
ing transition from footpoint to anode spot mode. The in-
tensity of Cu II lines is extremely decreased in the gap
center. The intensity and dynamic behavior of Cu I lines
indicate an active role of atoms together with the ions in
different charge states in high current anode modes.
(a)
(b)
Figure 1: Light emission of footpoint (a) and anode spot mode (b) in the vacuum gap during AC 50 Hz halfwave of 3.5 kA peak current.
HTPP14 Munich: Session 9, Poster S9-6
118
HTPP14 Munich: Session 9, Poster S9-7
119
Arc tracking power balance for copper and aluminium wires Th André
1, F Valensi
1, Ph Teulet
1, Th Zink
2
1Université de Toulouse, UPS, INPT, CNRS, LAPLACE 118 route de Narbonne, F-31062 Toulouse cedex 9, France
2Airbus Operations S.A.S., Site de Saint Martin du Touch, 316 route de Bayonne, F-31060 Toulouse Cedex 9, France
Abstract
When an electric arc occurs and propagates along two
parallel wires, this event is called arc tracking [1]. In aer-
onauticsit represents an important risk and if it cannot be
absolutely avoided the consequences should at least be
limited. Beside cable ablation (along with emission of
smoke and ejection of metal droplets), the arc may trans-
fer to the nearby structure. Arc tracking issue were for-
merly well mastered, but the new generation of aircrafts
gives rise to this problem again. In particular the use of
aluminium instead of copper (for weight reduction) and
the use of higher voltage (to increase the embedded elec-
tric power) can favour arc tracking occurrence.
Short circuits tests have been carried out with two volun-
tarily damaged aeronautic cables under alternating current.
The rms value was set to 174 or 244 A for copper (called
DR or DZ) and aluminium (called AD) cables with a sec-
tion of 3.26 or 2.59 mm. The two cables were connected
to different phases leading to relative voltage of 400 V. A
plate of aluminium (10 cm×10 cm, 1.2 mm thick) repre-
senting the fuselage, was set near the cables, and con-
nected to the neutral.
Probes have provided the evolution of the arc voltage and
current during the tests, while radiation heat flux sensors
enabled a quantification of the radiated power. Besides,
the cables have been weighed before and after each test, in
order to determine the ablated mass.
From these data, power balance has been determined, for
the total duration of the arc and during the established
tracking regime. The total average power has been esti-
mated. One part of the total power is transferred to the
electrodes, while the other part is deposited in the arc
column. The power transferred to the electrodes (estimat-
ed by means of the electrode voltage drop) causes cable
melting and vaporization, and part of it is lost by conduc-
tion and radiation. The estimation of the power needed for
electrode melting and partial vaporization is based on a
thermodynamic calculation, using the ablated mass. The
power deposited in the column is mainly radiated, and the
remaining part is lost by convection and conduction.
At 244 A, around 60 % of the total energy is transferred to
the electrodes, and around 40 % is deposited in the arc
column. It is also observed that more fumes are released in
the case of copper (which could indicate higher vaporiza-
tion) while aluminium provides abundant metal droplets.
Regarding the power radiated by the arc column, in the
case of aluminium the calculations can lead to a power
superior to the total available amount. This could be due
to chemical reactions that are not considered in the energy
balance. Indeed for those tests, we observe on the metal
droplets a white layer that may correspond to aluminium
oxide Al2O3 (which forms through a very exothermic reac-
tion). However, it is hard to conclude since the amount of
oxidized metal is difficult to estimate. In order to evaluate
the influence of oxidation reactions of aluminium (and the
amount of energy released by these reactions), a test cam-
paign of arc tracking has to be performed under
non-oxidizing conditions (nitrogen atmosphere instead of
the air). Material analysis could also bring additional in-
formation.
References [1] Dricot F, Reher H J, 1994 Survey of arc tracking on
aerospace cables and wires IEEE Transactions on Di-
electrics and Electrical Insulation 1 (5), 896–903
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A Novel Inductively Coupled Plasma Torch for Mass Spetrometry
(ICP-MS) S Alavi
1, J Mostaghimi
1*, L Pershin
1, S Yugeswaran
1, H Badiei
2, K Kahen
2
1Center for Advanced Coating Technologies (CACT), University of Toronto, Toronto, Ontario, Canada
2Per kin-Elmer Inc., Woodbridge, Ontario, Canada
* Corresponding Author: [email protected]
General The inductively-coupled plasma mass spectrometry (ICP-MS) is the fastest growing trace element analysis technique available today. It is a powerful tool for trace/ultra-trace (parts per quadrillion, ppq, levels) element evaluation and speciation analysis. Some of the major ad-vantages of ICP-MS over similar technologies, i.e., ICP optical emission spectrometry (ICP-OES), flame atomic absorption (FAA), and electro-thermal atomization (ETA) spectroscopy, are the speed of analysis, low detection limits (10 ng/L and lower), wide analytical working range, and isotopic capabilities. At the heart of this system lies the ICP torch (Figure 1) which serves as the ionization source for various samples of interest. After ionization, the sample particles pass into the mass spectrometer for detection purposes.
Figure 1: Schematics of a typical ICP torch.
ICP torches have gone through various modifications since their first introduction by Reed [1]. In spite of their major benefits, ICP-based systems suffer from a major drawback. As the most important obstacle in faster development of ICP-based systems throughout the world, especially in developing countries, these systems consume a significant amount of argon gas. Table 1 shows the typical range of ICP-MS operating parameters. Despite some efforts in reducing the argon flow rate, which was partially success-ful, on average, a typical ICP torch still needs 15 L/min of argon to keep the plasma stable and the quartz tube safe from thermal damages (i.e. T < 1300 K). Some of the important approaches to reduce the argon consumption are: increasing the swirl velocity of the coolant gas [3], miniaturization of the torch (i.e. size re-duction) [3], designing high-efficiency torches [4], build-ing torches from different materials [5], alternative coolant gases such as nitrogen or helium, external wall cooling techniques using water or air [6], plasma discharge at low pressures, and sealed/enclosed ICP discharges. In this re-search, however, an alternative approach is followed: ar-gon recycling.
Argon Recycling In a typical ICP-MS s ystem, only about 12 % of the con-sumed argon goes into the sampler orifice for analytical purposes. The remainder is discharged into environment without any further use. It would be thus reasonable if the exhausted argon could be collected and recycled back into
the system. The purity of argon needed for ICP-MS must be as high as 99.996 %. This imposes serious challenges in designing an effective purification system, considering the high concentration of H2O, N2, H2, O2, CO, CO2, etc., in the exhaust gas. A collection system was designed and tested to collect the exhaust gas before it becomes further contaminated with the surrounding air. For this purpose, a magne-to-hydrodynamic (MHD) model was developed and em-ployed to simulate the situation and the torch exit. The obtained fluid flow and temperature data were used to design an efficient system based on ICP-MS operational requirements. The collector was then tested in an actual ICP-MS system where it was observed to be suitable for this purpose. Next, an experimental setup was designed to extract the impurities from the exhaust gas. In the first step of this process, a thermoelectric Peltier cooler was employed to freeze and capture the water content by decreasing the temperature to -15°C. A gas chromatograph was used to analyse the system output. It was shown that this method can effectively extract the water content from the exhaust gas. In the second phase, other impurities, e.g. N2, O2, H2, will be filtered.
Acknowledgements Financial support of Perkin Elmer International and On-tario Centres of Excellence is gratefully acknowledged.
References [1] Reed T B, 1961 Induction‐Coupled Plasma Torch. J. of
Appl. Phys. 32 (5):821-4 [2] Thomas R, 2013 Practical guide to ICP-MS: a tutorial
for beginners: CRC press [3] Savage R N, at al., 1979 Development and characteri-
zation of a miniature inductively coupled plasma source for atomic emission spectrometry. Anal. Chem. 51(3):408-13
[4] Rezaaiyaan R et al., 1982 Design and Construction of a Low-Flow, Low-Power Torch for Inductively Cou-pled Plasma Spectrometry Appl Spectrosc 36 (6):627-631
[5] van der Plas P S C at al.,1984 A radiatively cooled torch for ICP-AES using 1 l min
−1 of argon. Spectro-
chimica Acta Part B: Atomic Spectroscopy 39 (9-11):1161-9
[6] Weiss A D at al., 1981 Development and characteriza-tion of a 9-mm inductively-coupled argon plasma source for atomic emission spectrometry Anal. Chim. Acta 124 (2): 245-258
Table 1: Typi cal range of mass spectrometry ICP source parameters [2]
Frquency (MHz)
Power (W)
Coolant gas (L/min)
Auxiliary gas (L/min)
Injector gas (L/min)
27 or 40 ~ 1600 12 - 17 ~ 1 ~ 1
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Computational fluid dynamic analysis of Plasma SprayPhysical
Vapor Deposition P Wang1*, R Mücke1, W He
1, G Mauer
1, R Vaßen
1
1 Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research, IEK-1: Materials Synthesis and Processing
Modelling of Low-pressure PS-PVD processes
Modelling of the supersonic compressible plasma flow has
been developed to describe the thermodynamic and
transport properties of the plasma spray physical vapor
deposition process (PS-PVD) for typical processing pa-
rameters used for columns microstructure formation of
thermal barrier coating (TBC). The required properties of
the plasma gas mixtures (Ar and He) were obtained as a
function of temperature and pressure from the thermody-
namic calculations in chemical equilibrium (CEA pro-
gram) with the effect of ionization [1]. Commercial com-
putational fluid dynamics software (ANSYS fluent 16.2)
has been used for the simulations. Through a
two-dimensional numerical analysis, Pressure-based and
SST k-omega model is applied to simulate the temperature
and velocity distribution of the plasma plume. Based on
user-defined functions, three different plasma mixture
compositions [2] were obtained as input to model the
plasma plume. As shown in Figure 1, the contour of the
Mach number distributes in the supersonic plasma.
Figure 1: Contour of the plasma plume Mach number.
Boundary layer thickness
A new definition of boundary layer thickness definition
was defined to analyse the boundary layer thickness the
because of the low pressure in the chamber.
∇p = ∇2u (1)
The thickness of the velocity boundary layer is normally
defined as the distance from the solid body at which the
viscous flow velocity is 99 % of the freestream velocity.
For the plasma spray process, due to the low pressure, the
boundary layer thickness defined from the surface at
which the pressureincreases. The boundary layer thickness
was found to be 15 mm.
Figure 2: Contour of the plasma pressure distribution near the sample.
Non-line-of-sight
As shown in Figure 3, vertices are formed in the back of
the sample. It would prove that there is a possibility to
deposit the coating in the back of the sample, which is
called non-line-of-sight (NLOS) effects.
Figure 3: Contour of the plasma velocity distribution near the sample.
Challenges
The two-dimensional analysis of the carrier gas effects is
not comparable to the experiment.
References
[1] Mauer G, Vaßen R, 2012 Plasma Spray-PVD: Plas-
ma Characterization and Impact on Coating Proper-
ties J. Phys.: Conf. Ser. 406 012005
[2] Mauer G, Plasma Characteristics and Plas-
ma-Feedstock Interaction under PS-PVD Process
Conditions 2014, Plasma Chem. Plasma Proc. 34
1171
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Excitation temperature and concentration profiles of an Ar/He jet under Plasma Spray-PVD conditions
W He*, G Mauer, R Vaßen
Forschungszentrum Jülich GmbH, IEK-1, Jülich, Germany
*[email protected] Plasma spray-physical vapor deposition (PS-PVD) is a
promising technology to produce ceramic coatings with
advanced microstructures. In the PS-PVD process, the
plasma gases can be different, such as argon, helium, hy-
drogen, nitrogen [1] or mixtures of them. A standard
plasma gas mixture of argon and helium is normally used
to manufacture columnar structured ceramic coatings.
Since the composition of plasma gas has a huge influence
on the microstructures of PS-PVD coatings, it is interest-
ing to know its characteristics.
Excitation temperature profiles
Plasma characteristics were measured by optical emission
spectroscopy (OES) at spraying distances (s.d.) of
1000 mm and 700 mm. Abel inversion has been utilized to
transform laterally measured intensity I(y) into local radial
emissivity ε(r) according to equation (1) to (2).
Excitation temperatures in the plasma were determined by
atomic Boltzmann plot method [2]. The radial excitation
temperature Texc(r) is calculated according to equation (3).
Figure 1 shows average excitation temperature Texc calcu-
lated with measured intensity, axial excitation temperature
Texc(0) calculated by the method without Abel inversion
proposed in [2] and Texc(r). The increase of excitation
temperature of He beyond ad is placement of 40 mm could
be caused by being far from equilibrium of helium plasma
[3].
Figure 1: Excitation temperatures of Ar and He at s.d. of 1000 mm.
Concentration profiles of Ar and He The intercept of equation (3) is related to ntot. Therefore,
the ratio between Ar and He in the plasma was calculated
according to equation (4)
The increasing ntot(Ar)/ntot(He) along radial displacement
in Figure 2 indicates that in the center of plasma jet the
main fraction is He while Ar exists mainly from the pe-
riphery of helium flow.
Figure 2: Ratio of concentration between Ar and He at s.d. of 1000 mm.
Figure 3: Axial excitation temperatures determined for different
spraying parameters.
The results in Figure 3 show that the introduction of pow-der has a remarkable loading effect on Texc(0) under PS-PVD conditions.
References
[1] Mauer G, Vaßen R, Stöver D, 2010 Thin and Dense
Ceramic Coatings by Plasma Spraying at Very Low
Pressure. Journal of Thermal Spray Technology
19(1-2):495-501
[2] Marotta A, 1994 Determination of axial thermal
plasma temperatures without Abel inversion. Journal
of Physics D: Applied Physics 27 (2):268
[3] Jonkers J, Van der Mullen J, 1999The excitation
temperature in (helium) plasmas. Journal of Quanti-
tative Spectroscopy and Radiative Transfer 61
(5):703-9
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Arc-anode attachment area in DC arc plasma torch P Ondac1,2*, A Maslani2 and M Hrabovsky2
1 Institute of Plasma Physics AS CR, Za Slovankou 1782/3, 182 00 Prague 8, Czech Republic 2 Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2,
182 00 Prague 8, Czech Republic
Introduction
The need to improve plasma spraying processes, waste
treatment and plasma synthesis has motivated us to inves-
tigate plasma in the anode attachment area of DC arc
plasma torch. Studying the processes in this area helps to
extend the lifetime of the anode, stabilize the plasma flow
and better understand a movement of the anode attach-
ment in the restrike mode. For this mode, the anode at-
tachment moves periodically downstream along the anode
surface. The movement is the result of the imbalance be-
tween the drag force caused by the interaction of the in-
coming plasma flow over the arc attachment and the elec-
tromagnetic force caused by the double curvature of the
arc [1]. However, the cause of the second curvature of the
arc close to the anode surface and the arc reattachment
process is still not well explained. In the majority of pub-
lications, the anode processes were observed only indi-
rectly. This study follows publication [2].
Methods
For our experimental investigation of the plasma in the
anode attachment area, we used the hybrid water-gas DC
arc plasma torch with the external anode (Figure 1), the
high-speed monochromatic camera and synchronized
cathodeanode voltage measurements (sample rate
80 MHz). We directly observed and analysed the move-
ment of the anode attachments and the plasma flow above
them.
Figure 1: Sketch of the hybrid water-gas DC arc plasma torch.
Observations and Results
The reattachment process is visible in two camera images
in Figure 2. The attachment inclines downstream because
of the drag force. The electric current flows mainly per-
pendicular to the anode surface (through the shortest
path); therefore, there is the second lower curvature of the
arc. As the attachment moves downstream, the electrical
resistance between the positions X1 and X3 increases. The
new current path and consequently a new attachment aris-
es between X1 and X2 because this new path starts to have
a smaller resistance than path X1-X4. In time 10 µs, only
the new attachment remained.
Figure 2: Mechanism of arc reattachment process in restrike mode.
We calculated the averaged electrical conductivity σ of the
arc plasma above the anode from the voltage between new
and former attachment, their distance and the constant
electric current flowing through the attachments to the
anode. We also extended and refined our calculations of
dwell frequencies, dwell times and attachment velocities
in publication [2] and compared the results for new and
worn anode.
Conclusion
We present a new view of reattachment process, explana-
tion of the second curvature of the arc (both consistent
with our experiments) and a new way for calculation of
the electrical conductivity of the plasma above the anode,
during the restrike mode. For the first time, the process of
punching small craters (during the dwelling) into the an-
ode surface by the attachments was studied in such detail.
Acknowledgements
The work was supported by the Grant Agency of the
Czech Republic under the project GA15-19444S.
References
[1] Wutzke S A, 1967 Conditions governing the symp-
tommatic behavior of an electric arc in a superimposed
flow field. Ph.D. thesis, University of Minnesota
[2] Ondac P et al., 2016 Investigation of the arc-anode
attachment area by utilizing a high-speed camera.
Plasma Physic and Technology J.: 3 (1): 1-5
HTPP14 Munich: Session 9, Poster S9-11
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129
Study of BSO properties dedicated to measurement of electric
charge on dielectric surface E Paniel
*, H Rabat and D Hong
GREMI, UMR 7344, University of Orléans, CNRS, 14 rue d’Issoudun, 45067 Orléans, France
In order to measure the surface charges on a dielectric, vari-
ous methods have been used including the use of an electro-
static voltmeter [1]. For the same purpose, the Pockels effect,
consisting in a birefringence of a specific crystal induced by
an electric field, was sometime used [2-3]. Indeed, applying
an electric field on some material may cause variations of
indices along its three axes. This modification of indices
changes the polarization of the transmitted light, and conse-
quently, the measured light intensity according to a given
direction. Thus the intensity measurement allows to determine
the voltage and then the surface charges.
Bismuth germanium oxide (Bi12GeO20) [2] or bismuth silicon
oxide (Bi12SiO20 (BSO)) [3] were used in previous studies.
These crystals have also rotation power [4]. For instance, the
rotation power of BSO is 22°/mm. The convolution of this
effect with the birefringence shall lead a complex modifica-
tion of the light polarization. It seems to us that this effects
convolution was not taken into account in previous studies. In
order to consider these two effects together, a numerical study
has been performed. The crystal of 1 mm in thickness was
considered as a stack of 100 thin layers. For each thin layer,
rotating and birefringent effects were applied separately.
Jones matrices were used to perform the calculation. To vali-
date our program, we have then compared the calculated val-
ues with the experimental ones.
To realize the experimental measurements, a crystal of BSO
was used. The size of this crystal was 20x20 mm2
with 1 mm
in thickness. Thin layer deposition of ITO (Indium Tin Oxide)
of about 500 nm in thickness was used to obtain transparent
electrodes. On one side, a square of 18x18 mm2
was deposited,
while a small strip of 18x4 mm2
was deposited on the other
one. A He-Ne laser at 632.8 nm (Siemens LGK 7628-1,
15 mW) was used. Laser light polarization was transformed
into circular polarization thanks to a polarization plate and a
λ/4 plate. Then the light became elliptically polarized after the
passage of the BSO. To measure the intensity in a given di-
rection, another polarization plate was used. The transmitted
intensity was finally measured with a photodiode. The first
measurements were made with DC voltage and the laser beam
was directed at the place where the two electrodes were
face-to-face. The transmitted intensity along the major axis of
the ellipse was measured for more than 20 voltage values
between -3 and 3 kV. Figure 1 shows the intensities obtained
with the program and the experimental data (x symbol). The
obtained good agreement validated our program.
Figure 1: Intensity obtained experimentally and numerically as a
function of the applied voltage.
This validated program enabled to obtain a relation between
the transmitted intensity along the major axis and the sur-
face charges.
Then, this specific relation was used to determine surface
charges on BSO from the light intensity measurement for a
surface DBD discharge supplied with a 1 kHz sinusoidal
voltage of 12 kV in peak-to-peak value, and for a DC corona
discharge in tip-plate configuration.
Refeences
[1] Paniel E, Rabat H, Hong D, 2014 Relative Residual
Charge Distribution and the Corresponding Discharge
Image of a Surface DBD IEEE Trans. Plasma Sci. 42
2696-2697
[2] Gégot F et al., 2008 Experimental protocol and critical
assessment of the Pockels method for the measurement
of surface charging in a dielectric barrier discharge J.
Phys. D Appl. Phys. 41 135204.
[3] Takeuchi N et al., 2011 Surface charge measurement in
surface dielectric barrier discharge by laser polarimetry
J. Electrostat. 69, 87-91
[4] Bayvel P, 1989 Electro-optic coefficient in BSO-type
crystals with optical activity measurement and applica-
tion to sensors Sensors and Actuators 16, 247-254
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Influence of gas medium on the switching arc decaying behavior by
non-chemically equilibrium calculation Y Wu, H Sun, M Rong, F Yang, C Niu
State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, China
Introduction
In the circuit breaker, the arc plasma will be generated
when the two electrodes are separated from each other.
Usually the investigation on the arc plasma can be divided
into two phases: the arc ignition phase and the arc decay-
ing phase. To investigate the arc behaviour numerically,
the Magneto-Hydrodynamic (MHD) method is widely
adopted, which couples the calculation of fluid dynamics
with the electromagnetic field. During the arc ignition
phase, the local thermally equilibrium (LTE) hypothesis
was commonly used in almost all the previous researches,
in which one of the important assumption is that all the
chemical reactions reach the equilibrium. However, during
the arc decaying phase, since the temperature keeps de-
creasing and all the reaction rates become slower, the LTE
hypothesis is no longer consistent during this period. In
our previous work [1], a numerical non-chemically equi-
librium (non-CE) model for the arc decaying phase was
established and the validity was confirmed by the experi-
ment. In this work, we focused on the influence of arc
quench medium on the arc decaying behaviour by this
non-CE model, the arc behaviour obtained by the LTE
model is also presented for comparison.
Calculation domain
Figure 1 presents the calculation domain in this work,
which was the same as in [1], along with the temperature
profile of air arc during the ignition phase, which was
used as the initial condition for the arc decaying calcula-
tion. In the present calculation, the arc current was set as
50 A DC during the arc ignition and at t=0 μs the current
was stepped down to 0 to simulate the free recovery
phase.
Figure 1: Calculation domain [1] and the initial temperature profile.
Results and discussions Figure 2 shows the temperature and the electron decay at
r = 0 mm, z = 80 mm after the current drops to zero by
both the non-CE and LTE calculations. The temperature
decays indicate that in LTE model, the temperature in O2
decays fastest while the temperature in N2, which decays
at a similar rate to that in the air, decays most slowly. The
reason is that in the temperature around 7000 K, the asso-
ciation reactions N+N+M→N2+M will release heat to the
arc zone. Since the mole fraction of N2 in air is less than
that in N2, less heat will be release at around 7000 K and
thus the temperature in air is slightly lower. However, the
trends in non-CE model are quite different. For example,
the temperature in air decays more slowly than that in N2,
the reason is that in air the reactions are much closer to
equilibrium than N2, which can be seen from the electron
decays in figure 2 (b), and more heat is released by the
association reactions in air. It should be also noted that the
temperature and electron decays of the same arc medium
in non-CE model are quite different from those in LTE
model, which is caused by the decrease of reaction rate in
non-CE model, as in figure 2 (b).
In the previous researches, thermodynamic and transport
properties were considered to have the crucial influence
on the arc behavior. However, in our work, it was found
out that the reaction pathway and the reaction rate has
more important influence. For example, although the
properties of air and N2 are similar, but such kind of reac-
tions in air, N+O+O→NO+O, will greatly accelerate the
reaction process, leading to the great difference of arc
behaviors between air and N2, as in figure 2.
Figure 2: Temperature and electron decays after current zero.
Acknowledgements
This work was supported in part by the National Key
Basic Research Program of China (973 Program) (No.
2015CB251002), National Natural Science Foundation of
China (Nos. 51521065, 51577145).
References
[1] Sun H, Tanaka Y, Tomita K et al., 2016 J. Phys. D:
Appl. Phys. 49 055204 (17pp)
[2] Tanaka Y, Michishita T, Uesugi Y, 2005 Plasma
Sources Sci. Technol. 14 134–151
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133
Investigations of low temperature atmospheric pressure plasma
sources for surface treatment F Zimmer
1, T Hofmann
1, J Holtmannspötter
1, S Zimmermann
2, M Szulc
3, J Schaup
2, J Schein
2
1Bundeswehr Research Institute for Materials, Fuels and Lubricants (WIWeB), Institutsweg 1, 85435 Erding / Germany
2UniBw, EIT1, LPT, Neubiberg / Germany
3Zierhut Messtechnik GmbH, Munich
Non-thermal plasmas are increasingly used for decontam-
ination, sterilization and activation of surfaces and equip-
ment. The most important reactive species produced by
cold atmospheric plasmas, regarding their antimicrobial
impact, are reactive oxygen and nitrogen species. On the
contrary the UV radiation does not yield a significant in-
fluence on the inactivation of bacteria, as UV doses of
several mWs/cm² are required, which such plasmas do not
provide. First measurements were carried out on a cold
atmospheric pressure plasma unit made by Plasmatreat
from Steinhagen, Germany. The unit consisted of an pow-
er supply of type FG 5001 and a plasma jet of type RD
1004 with a standard nozzle. Different gases (air and ni-
trogen) have been used as plasma carrier gas for the
measurements. The plasma is generated by an arc dis-
charge, which burns between an inner, high voltage elec-
trode and a rotating, grounded outer electrode (nozzle).
Surface and plasma analysis are performed to identify
how changes in the parameters affect the plasma created
and its effect on the surface modification (Hexcel
8552/IM7 manufactured with a release foil) [1]. During
and after the treatment surface and plasma analysis are
performed across the plasma track as shown in Figure 5.
Figure 5: APPJ-treatment of a specimen. Surface and plasma analysis
are performed during and after the treatment to determine distributions
across the plasma track.
The plasma is analyzed using three different diagnostic
tools:
A pco.1200s high speed camera system [2] is used to in-
vestigate the interaction of the plasma with the target,
Figure 5. The second diagnostic system is a spectrometer
from Aventes, AvaSpec 2048 for the investigations [1, 2]
of the specific intensity of different wavelength straight on
the target during the plasma process. The third results,
recorded with different spectral filters, show that a change
of plasma parameters results in a significant change in the
emitted UV light. After recording, the images have been
analyzed with the self-programmed imaging software,
which determines the jet geometry [2].
Figure 2: False color image of the interaction for different noz-
zle-substrate distances [1].
In future investigations the effect of constituent species
within the plasma shall be observed with camera based
diagnostic tools (band pass filters). A comparison between
the distributions of specific species with the surface modi-
fication effects shall identify the species that are mainly
accountable for cleaning and activation effects.
References [1] F Zimmer, T Hofmann, J Holtmannspötter, S Zim-
mermann, M Szulc, J Schaup, J Schein, 2016 Detailed
Investigation of Atmospheric Plasma – CFRP Inter-
action to Create Robust Structural Adhesive Bonding
Processes for Aerospace Manufacturing, Adhesion
Society – 39th Annual Meeting San Antonio USA, 23th
February 2016
[2] M Szulc, S Schein, J Schaup, H Karl, N Truong, S
Zimmermann, J Schein, 2015 Investigations of an
atmospheric plasma jet for different surface treat-
ments/activations -First results, 32nd
ICPIG, July
26-31, 2015, Romania
HTPP14 Munich: Session 9, Poster S9-14
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Influence of doped oxide on tungsten-based electrode evaporation
in multiphase AC arc T Hashizume, M Tanaka, S Nagao, T Watanabe
*
Department of Chemical Engineering, Kyushu University
Abstract
Multiphase AC arc is generated among multi-electrodes
by phase-shifted AC power supplies. It has high energy
efficiency and large plasma volume. However, decreasing
electrode erosion is essential because it determines the
electrode lifetime and the purity of the products. Tungsten
electrode with doped oxide is generally used because of
their good characteristics in stable arc operation, although
the influence of such doped oxide on electrode erosion has
not been clarified. In the multiphase AC arc, the erosion of
electrode due to evaporation and droplet ejection was ob-
served [1]. In previous work, the relationship between
droplet ejection and doped oxide has been clarified.
Droplet ejection rate of electrode with doped oxide was
much smaller than that of pure W electrode. On the other
hand, relationship between the electrode evaporation and
doped oxide have not been understood yet. The purpose of
this work is to investigate the influence of the doped oxide
on electrode evaporation.
The multiphase AC arc consisted of 12 electrodes, cham-
ber, and AC power supply at 60 Hz. Arc current was 100 A
for each electrode. The electrodes were symmetrically
arranged. To prevent the electrodes from oxidation, argon
was injected around the electrode as shield gas at 2 L/min.
Three types of electrode, 2 wt% ThO2-W, 2 wt% La2O3-W
and pure W were compared.
Electrode evaporation was visualized by the high-speedcamera system. One of the electrodes was ob-served by high-speed camera installed on the top of the arc generator. Conventional observation of electrode dur-ing arc discharge was prevented by the strong emission of the arc. Therefore, the band-pass filter with 393 nm was combined with the high-speed camera system to separate the emission of tungsten vapour from the emission of the arc as shown in Figure 1. Electrode mainly evaporated at anodic period according to
visualization of the tungsten vapour. Figure 2 shows the
tungsten vapour area during an AC cycle. Evaporation in
pure W hardly occurred, and vapour area for La2O3-W
was larger than that for ThO2-W. Moreover, evaporation
timing in La2O3-W was earlier than that in ThO2-W. Fig-
ure 3 shows the evaporation rate with different electrode
types. The evaporation rate was estimated by subtracting
droplet ejection rate from total erosion rate. The evapora-
tion rate of pure W was smaller than other electrodes. This
suggests tungsten evaporation is strongly influenced by
doped oxide. Moreover, the evaporation rate of La2O3-W
was larger than that of ThO2-W. The reason for this result
will be discussed in following paragraphs.
Boiling point of doped oxide is lower than that of tungsten.
This suggests that doped oxide evaporates before the
tungsten evaporation. Vapour addition of doped oxide into
the arc leads to the higher electrical conductivity and arc
constriction. Therefore, heat flux from the arc to the elec-
trode is enhanced after the evaporation of doped oxide,
resulting in tungsten evaporation.
Decomposition temperature of La2O3 is lower than boiling
point of ThO2. Therefore, timing of the arc constriction for
La2O3-W is relatively earlier, resulting in severer evapora-
tion of tungsten. Obtained remarks suggest the arc con-
striction due to vapour addition of doped oxide has great
importance on tungsten evaporation.
Figure 1: Schematic diagram of high-speed camera system with
band-pass filters.
Figure 2: Area of tungsten vapour during an AC cycle.
Figure 3: Electrode evaporation rate with different electrode types.
References
[1] Hashizume T, Tanaka M, Watanabe T, 2015 Investi-
gation of droplet ejection mechanism from electrode
in multi-phase AC arc Quart. J. Jpn. Weld. Soc. 33
44s
HTPP14 Munich: Session 9, Poster S9-15
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HTPP14 Munich: Session 9, Poster S9-16
137
Preparation of silicon nanopowder from waferwaste by using ther-
mal plasma S Lee, T-H Kim and D-W Park
*
Department of Chemistry and Chemical Engineering and Regional Innovation Center for Environmental Technology of
Thermal Plasma (RIC-ETTP), Inha University, Incheon, Republic of Korea
A number of silicon slurry generated by a manufacturing
process for silicon based semiconductor and wafer has
been thrown away as waste in nature. Therefore, the
technology for recycling of them as useful resources have
been studied [1].
In this work, silicon nano-sized powders were prepared
from silicon wafer waste by using radio-frequency (RF)
thermal plasma. Since the vaporizing temperature of the
silicon solid is higher than metal as 3.538 K, hydrogen gas
was added to argon plasma gas for enhancement of evap-
oration rate. Silicon wafer was cracked by a ball mill and
it was used as raw material. The injected silicon powders
were vaporized in a high temperature region formed as
nano-sized particles by rapid temperature gradient of
thermal plasma and additional quenching gas. The sche-
matic diagram of the RF thermal plasma processing for
the preparation of silicon nanopowder is indicated in Fig-
ure 1. The quenching gas was injected to opposite direc-
tion with the thermal plasma flame through quenching gas
injection apparatus of Figure 1 (d). In the preliminary ex-
periment, it is confirmed that when the quenching gas
injection apparatus was used, the silicon precursor was
more excellently vaporized compared with absence of the
quenching gas injection apparatus. The quenching gas
encountered with high velocity plasma flow in the cham-
ber of Figure 1 (c), formed the turbulent flow [2]. The
injected particles stayed during the longer time at the high
temperature recirculation by the turbulent flow. As a result,
the injection of quenching gas in the opposite direction of
plasma flow enhances the residence time in the high tem-
perature recirculation flow. Therefore, it occurred the va-
porization improvement of silicon raw material.
In order to control the turbulent flow characteristics, the
variation of the flow rate and the interval between the
torch exit and the quenching gas nozzle was established
the parameters. The flow rate of quenching gas was con-
trolled from 30 L/min to 70 L/min argon. The interval
between the torch exit and the counter flow quenching gas
nozzle was adjusted from 150 mm to 350 mm as control
the height of quenching gas injection apparatus in figure 1
(d). When the flow rate and the interval for the quenching
gas injection wererespectively 70 L/min and 350 mm, the
most precursors were vaporized and formed into na-
nopowder. In other experimental conditions, unvaporized
large silicon particles were observed. It means that the
evaporation rate of precursor was related with the recircu-
lation in the high temperature region.
Consequentially, the silicon nanopowder with average size
of 31.73 nm were prepared by the operating condition
which the interval between the torch exit and the counter
flow quenching gas nozzle was 350 mm and the flow rate
of quenching gas was 70 L/min.
Figure 1: Schematic diagram of the RF thermal plasma processing for
the preparation of silicon nanoparticles. This system consists of (a):
torch, (b): power generator, (c): chamber, (d): quenching gas injection
apparatus, (e) thermal insulation tube, (f): powder feeder, (g): cyclone,
(h): back filter and (i): vacuum pump.
Acknowledgements
This work was supported by an Inha University Research
Grant.
References
[1] Wang T Y, Lin Y C, Tai C Y, Sivakumar R, Rai D K,
Lan C W, 2008 A novel approach for recycling of
kerf loss silicon from cutting slurry waste for solar
cell applications J. Cryst.Growth 310 3403
[2] Li J-G, Ikeda M, Ye R, Moriyoshi Y, Ishigaki T, 2007
Control of particles size and phase formation of TiO2
nanoparticles synthesized in RF induction plasmas J.
Phys. D: Appl. Phys. 40 2348
HTPP14 Munich: Session 9, Poster S9-16
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HTPP14 Munich: Session 9, Poster S9-17
139
Comparing models of near-cathode sheaths in high-pressure arcs M S Benilov
1,2*, N A Almeida
1,2, M Baeva
3, M D Cunha
1,2, L G Benilova
1, D Uhrlandt
3
1 Departamento de Física, FCEE, Universidade da Madeira, Largo do Município, 9000 Funchal, Portugal
2Instituto de Plasmas e Fusão Nuclear, IST, Universidade de Lisboa, Portugal
3Leibniz Institute for Plasma Science and Technology, Felix-Hausdorff-Strasse 2, 17489 Greifswald, Germany
Three approaches to description of separation of charges
in near-cathode regions of high-pressure arc discharges
are considered. The most straightforward one is the uni-
fied modelling [1], which does not rely on apriori division
of the inter-electrode gap into quasi-neutral plasma and
space-charge sheaths.
The second approach, which may be called the
NLTE-sheath approach, is based on separate descriptions
of the bulk quasi-neutral plasma and space-charge sheaths
formed near solid surfaces (electrodes and insulators). The
description of the bulk plasma is fully non-equilibrium,
i.e., does not rely on assumptions of thermal (Te=Th) or
ionization equilibrium. Boundary conditions for the bulk
plasma equations, describing space-charge sheaths in the
framework of this approach, are derived in [2] and a nu-
merical realization of the NLTE-sheath approachis de-
scribed in [3].
The third approach employs separate descriptions of the
bulk plasma, where deviations between Te and Th are taken
into account but deviations from ionization equilibrium
are not, of the ionization layer, and the near-cathode
space-charge sheath. This approach may be called the
2T-ionization layer-sheath approach. Since processes in
the bulk have little effect over the cathodic part of the arc,
calculation of the cathodic part (the cathode, the sheath,
and the ionization layer) is decoupled from calculation of
the bulk plasma in the framework of this approach. The
reduced version, in which only the cathodic part is simu-
lated, is sometimes referred to as the nonlinear surface
heating model.
Since the unified modelling has been performed until now
only in 1D cases while the NLTE-sheath approach has
been realized only for the axially symmetric case, all the
three approaches cannot be compared at once. Results
given by the unified modelling are compared with those
given by the model of nonlinear surface heating on the
simple 1D test case of a rod cathode with thermally and
electrically insulated lateral surface. Results given by the
NLTE-sheath approach are compared with those given by
the model of nonlinear surface heating on the axially
symmetric test case of a free-burning atmospher-
ic-pressure argon arc with a rod cathode with a hemi-
spherical tip. It is found that the results given by different
models are in a generally good agreement, and in some
cases the agreement is even surprisingly good.
The unified modelling approach is at present prohibitively
intense computationally in situations of practical interest
that require multidimensional simulations. If the main
objective is to simulate the cathodic part rather than the
arc on the whole, then it seems natural to employ the
model of nonlinear surface heating, which is the simplest
one and is ready for use for a wide range of plas-
ma-producing gases (see, e.g., the free Internet tool [4]).
This model is a natural first step also in simulations of the
arc on the whole, which can be performed by means of
either NLTE-sheath approach or the 2T-ionization lay-
er-sheath approach. The former is the method of choice in
cases where deviations from ionization equilibrium occur-
ring in the vicinity of anode and in the arc fringes are of
interest. The 2T-ionization layer-sheath approach may be
used in cases where deviations from ionization equilibri-
um occurring in the vicinity of anode and in the arc fring-
es are not of primary interest.
The work at Universidade da Madeira was supported by
FCT through the projects PTDC/FIS-PLA/2708/2012 and
Pest-OE/UID/FIS/50010/2013. The work at INP
Greifswald e.V. was supported in part by the DFG under
grant UH106/11-1. The collaboration between INP
Greifswald e.V. and Universidade da Madeira has been
supported in part by funding from the European Union
Seventh Framework Programme under grant No. 316216.
References
[1] Almeida N A, Benilov M S, Naidis G V, 2008 Unified
modelling of near-cathode plasma layers in
high-pressure arc discharges J. Phys. D: Appl. Phys.
41 245201
[2] Benilov M S, Almeida N A, Baeva M, Cunha M D,
Benilova L G, Uhrlandt D, 2016 Account of
near-cathode sheath in numerical models of
high-pressure arc discharges J. Phys. D: Appl. Phys.
(to appear)
[3] Baeva M, Benilov M S, Almeida N A, Uhrlandt D,
2016 Novel non-equilibrium modelling of a dc elec-
tric arc in argon J. Phys. D: Appl. Phys. (to appear)
[4] Benilov M S, Cunha M D, 2005 On-line tool for sim-
ulation of different modes of axially symmetric cur-
rent transfer to cathodes of high-pressure arc dis-
charges http://www.arc_cathode.uma.pt/tool
HTPP14 Munich: Session 9, Poster S9-17
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HTPP14 Munich: Session 9, Poster S9-18
141
Pulsed arc plasma jet synchronized with drop-on-demand dispenser F Mavier
1*, V Rat
1, M Bienia
1, M Lejeune
1, J-F Coudert
1
1 Univ. Limoges, CNRS, ENSCI, SPCTS, UMR 7315, F-87000 Limoges, France.
Abstract
In the field of thermal spray coating processes, research
has led to the development of nanostructured coatings by
suspension plasma spraying (SPS) and precursor solution
plasma spraying (SPPS). Liquid injection are promising
techniques with the potential to become industrially viable.
However, a better control of plasma/material interactions
is necessary. Mono-electrode DC torches indeed generate
strongly fluctuating plasma that modifies the thermal and
dynamic transfers to the injected suspension droplet, re-
sulting in an inhomogeneous treatment of the latter. This
directly influences the texture and microstructure of de-
posits and subsequently their properties [1].
Efforts to understand the origins of these instabilities have
been made. Previous works have shown that these insta-
bilities are mainly due to the effects of plasma gas com-
pressibility in the cathode cavity effects, belonging to the
instability mode called Helmholtz mode. Other fluctua-
tions are due to successive phenomena of elongation,
breakdown and restrike of the electric arc, also called "re-
strike mode". As analternative to instabilities attenuations,
a new approach is proposed: the reinforcement and modu-
lation of the instabilities [2]. The adjustment of process
parameters has allowed obtaining a pulsed laminar plasma
with a modulation of its properties. A low powered
home-made DC torch is used and operates with pure ni-
trogen as plasma forming gas. This device is synchronized
with a drop-on-demand injection system to reproduce the
same conditions of plasma/material interactions for each
injected droplet [3]. Aluminum nitrate aqueous solutions
and TiO2 suspensions are injected to make homogeneous
coatings with controlled microstructure and chemical
composition.
The objectives of this work are firstly to characterize and
understand plasma / droplet heat and dynamics transfers.
Secondly, to highlight the influence of the synchronization
and operating parameters on the coatings obtained.
Figure 1: General schematic view of the process.
Acknowledgements
The French National Research Agency is thanked for
financial support in the frame of PLASMAT program
(ANR-12-JCJCJS09-0006-01).
The Electric Arc Association (AAE) is thanked for
financial support.
References
[1] Etchart-Salas R, 2007 Suspension Plasma Spraying.
Analytical and experimental approach of the phenom-
ena imply in the reproducibility and the quality of the
deposits” Thesis, (University of Limoges, 2007).
[2] Rat V, Coudert J F, 2010 Pressure and Arc Voltage
Coupling in Dc Plasma Torches: Identification and
Extraction of Oscillation Modes. Journal of Applied
Physics 108 (4): 043304
[3] Krowka J, Rat V, Coudert J F, 2013 Resonant Mode
for a Dc Plasma Spray Torch by Means of Pressure–
voltage Coupling: Application to Synchronized Liq-
uid Injection., Journal of Physics D: Applied Physics
46 (22): 224018
HTPP14 Munich: Session 9, Poster S9-18
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HTPP14 Munich: Session 9, Poster S9-19
143
The Analysis of Physics Processes in the Electric Discharge Cham-
ber of the AC Plasma Torch under the High Pressure of the Work-
ing Gas A A Safronov
1, O B Vasilieva
1, J D Dudnik
1, V E Kuznetsov
1, V N Shiryaev
1
1Institute for Electrophysics and Electric Power of RAS Saint-Petersburg,191186 Dvortsovaya nab. 18
Abstract The paper is devoted to investigate electro physics pro-
cesses in an electric discharge chamber of a three phase
AC plasma torch when using working gas under the high
pressure [1]. Physics processes, character of the arising
voltage ripples depending on various parameters of work
of the plasma torch have been investigated. Photo record-
ing of arcs burning processes in the electric discharge
chamber [2] of the three-phase AC plasma torch at various
working parameters was executed. The engineering solutions providing initiation of the elec-
tric arc in the plasma torch chamber and its reliable work
with the initial pressure up to 1.6 MPa are examined. Special features of the electrode work in the AC plasma
torch while applying the different types of plasma forming
gas in the wide range of gas flow rate and pressures were
examined. Physic technical parameters of a number of
materials for the AC plasma torch electrode production are
investigated. It is established that when using the relevant engineering
solution for the AC plasma torch, the opportunity to make
electrodes of rather inexpensive composite materials on
the basis of copper appears [3]. It is possible to obtain
high rates of the duration of the electrode continuous work
that would satisfy process requirements.
The results of the researches can be used while imple-
menting the various technological processes with the us-
age of the three-phase AC plasma torch. References [1] Rutberg Ph G, Safronov A A, Shiryaev V N, Kuz-
netsov V E, 1998 Arc three-phase plasma genera-
tors and their application, ТРР-5, Fifth European
Conference on Thermal Plasma Processes, 13-16
July 1998, St.Petersburg, 61
[2] Kovshechnikov V B, Antonov G G, Ufimtsev A A,
Surov A V, 2014 On Determination of Arc Cur-
rents in Three-Phase Single-Chamber Plasma
Generators, Journal of Engineering Physics and
Thermophysics: Volume 87, Issue 3, 715-720
[3] Budin A V, Pinchuk M E, Kuznetsov V E, Rutberg F
G 2014 The influence of the production technology
of iron-copper composite alloy on its erosion prop-
erties in a high-current high-pressure arc. Techical
Physics Letters Vol. 40, No. 12, 1061-1064, Pleadis
Publishing, Ltd., 2014, ISSN 10-63-7850
HTPP14 Munich: Session 9, Poster S9-19
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HTPP14 Munich
145
Thursday
HTPP14 Munich: Session 10
146
HTPP14 Munich: Session 10
147
Contributions of Plasma Physics to Metal-Inert-Gas Welding
J J Lowke and A B Murphy
CSIRO Manufacturing, Box 218, Lindfield, NSW 2070, Australia
General
The welding together of metals through the use of an
electric arc to promote melting and subsequent joining of
the metals has a long history. The original work was nat-
urally completely experimental, with no reference to
plasma physics, and there was little or no attempt to make
scientific predictions of weld properties for conditions
that had not been investigated experimentally. It is the
potential use of plasma physics to enable predictions to be
made for any welding metals, gases, currents or physical
configurations that spurs on such development. The sig-
nificant progress that has been made in the last 50 years is
described in this paper. For the first time, computer codes
now aspire to making predictions for hitherto unexplored
metals, such as titanium, or values of current and gas flow,
such as are used in plasma welding and cutting.
History
(1) Approximation of local thermodynamic equilibrium
[1].
(2) Calculating arc diameters neglecting electrodes.
(3) Inclusion of calculation of electrode temperatures [2].
(4) Inclusion of electrode melting at the anode.
(5) Predictions for Metal Inert Gas welding, including
droplets, wire feed, gas flow and metal vapour in three
dimensional calculations [3], as shown in Figure 1.
Equations
The energy balance equation (1) is used to predict the
dependence on time, t, and current, I, of the temperature, T,
in terms of the thermal and electrical conductivities, and
of the welding gas plasma, and liquid and solid metals
such as the welding wire and work-piece, is the density
and Cp the specific heat. In addition momentum balance
and mass continuity equations need to be solved to obtain
the velocities, ν, and pressure distribution, p.
Cp T/𝑡 ),,,,,( ItpvF (1)
Plasma physics structure
There are three quite separate branches of plasma physics
used in deriving weld predictions from equation (1) [4].
Firstly, cross sections as a function of energy need to be
known for all collision processes; for example for elec-
tron-argon collisions. Secondly, transport theory is used to
determine values of the coefficients such as and in
equation (1). Thirdly these equations need to be applied to
obtain specific solutions, for example for welding.
Figure 6: Calculated and measured weld profiles for welding aluminium,
including effects of metal vapour; 3-dimensional calculation [3].
Effect of fluxes – ATIG.
Increases in weld depth produced by fluxes covering the
workpiece surface can be explained at least approximately
by the flux confining the arc diameter. This leads to in-
creased current density and thus downward convective
flow of the molten metal increasing the weld depth [2].
Globular-spray transition
For welding arcs in argon, the current for which the tran-
sition from globular to spray mode occurs corresponds to
the pressure above which the magnetic pressure forces
from the welding current exceed the pressure that can be
provided by the surface tension of the liquid metal [5].
References
[1] Lowke J J and Tanaka M, 2006 LTE-diffusion ap-
proximation for arc calculations. J. Phys. D: Appl.
Phys. 39, 3634
[2] Lowke J J, Tanaka M and Ushio M, 2005 Mechanisms
giving increased weld depth due to a flux. J. Phys. D:
Appl. Phys. 38, 3438
[3] Murphy A B, 2013 Influence of metal vapour on arc
temperatures in gas-metal-arc-welding: convection
versus radiation, J. Phys. D: Appl. Phys. 46, 224004
[4] Murphy A B and Arundell C J, 1994 Transport coeffi-
cients of argon, nitrogen, oxygen, argon-nitrogen and
argon-oxygen plasmas, Plasma. Chem. Plasma Pro-
cess. 14, 451-490
[5] Lowke J J, 2009 Physical basis for the transition from
globular to spray modes in Gas Metal Arc Welding, J.
Phys D: Appl. Phys. 42, 135204
HTPP14 Munich: Session 10
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HTPP14 Munich: Session 10
149
Tuning nucleation and functionalization of nanostructures in a thermal
plasma: the case of graphene
J-L Meunier*, U Legrand, N Mendoza-Gonzalez, D Berk
Plasma Processing Laboratory, Chemical Engineering Dept., McGill University, Montreal, Canada.
General
Thermal plasma (TP) reactors are being used extensively
for the generation of particles having specific composi-
tions or phase structures. Nanoparticles (NPs) are also
being generated using precursors that are either in the gas
phase, in liquid solutions or even sometimes in the solid
phase. More difficult is the controlled homogeneous nu-
cleation of pure nanomaterials, or controlled heterogene-
ous nucleation in 2-step systems such as carbon nanotubes
(CNTs) where NPs are first generated and act downstream
as templates for the 1-D growth of CNTs. Most often
thermal plasma systems involve difficulties in having a
good control over the thermal history of the particles,
resulting in a lack of purity and uniformity of the product.
Another consequence of the difficult control of the resi-
dence time and trajectories in the various thermal fields is
what can be labelled as poor process “robustness”, mean-
ing strong variability of the product properties are ob-
served with fluctuations in control parameters such as
power and pressure. This is particularly true when the NP
synthesis occurs in the very high temperature regime
close to the exit nozzle of the thermal plasma device, a
region having most often strong fluctuations and turbu-
lences. Carbon-based nanomaterials fall in this category.
These also form a class of materials for which both
chemical and, more importantly “structural purity” be-
comes essential for many of the applications envisioned.
One material of strong interest is the 2-D structure of
graphene. The majority of graphene production is pres-
ently based on the strong oxidation of graphite and exfo-
liation, forming graphene oxide (GO), followed by reduc-
tion producing the reduced graphene oxide (RGO). This
process of forming GO and RGO intrinsically generates
an enormous amount of defects on the graphene structure,
to the point where the word graphene often seems mis-
used. This provides an opportunity for a TP processing
route based on high temperature homogeneous nucleation
in a bottom-up approach, provided one can control the
2-D structural evolution of the NP nucleated. The gra-
phene NPs most often require some chemical functionali-
zation for specific applications, and again a TP can pro-
vide the active species for functionalization scenarios
forming primary bonds between the functional group and
graphene. The plasma road here forms a unique environ-
ment allowing purity from the simple precursors, unri-
valed crystallinity from the extreme temperatures of nu-
cleation and growth, and in situ flexibility for tuning of
the functionalities directly inside the synthesis reactor.
This talk will describe the road for a controlled and pure
graphene nucleation, followed in the same reactor and
batch process by nitrogen, oxygen and iron functionaliza-
tion of the graphene structure. The aimed applications
here are for catalytic activity, in particular for non-noble
metal catalyst in fuel cells, and in the generation of gra-
phene-based nanofluids that show stability over time and
higher temperatures without the use of surfactants.
Graphene nucleation control
The precursors used for growing graphene are low con-
centrations of methane in argon using an ICP thermal
plasma system of 35 kW and pressures from 14 to 90 kPa.
Yield is not an issue here however purity, consistency in
the microstructure and process robustness are important.
A switch from the nucleation of spherical carbon nano-
particles to graphene structures is observed using (i) a
reactor design that generates a purely laminar flow elimi-
nating any recirculation, and (ii) a flow expansion that
pushes and enlarges the nucleation temperature field away
from the torch nozzle to the central volume of the reactor.
This allows an increased residence time in the specific
nucleation and growth temperature window
(4500 - 4900 K). CFD modeling of the nucleation/growth
fields indicate the critical clusters of carbon set the thick-
ness (number of atomic layers) of the graphene, while the
residence time in the growth field correlates with the
sheet side lengths (100 nm x 100 nm, with on average
10 atomic layers in thickness; namely graphene
nanoflakes (GNF)); this may provide separate control
parameters. The crystallinity parameters for these GNF
from TEM and Raman spectroscopy are exceptional in
comparison to regular top-down synthesis approach.
Graphene functionalization
Following deposition of the GNF on the collecting surface,
the controlled plasma expansion particularly at lower
pressures allows some active species to be maintained
downstream up to this surface. In this way, using either
nitrogen or air in argon, nitrogen and/or oxygen function-
alities can be covalently bounded to the graphene structure.
Recent results on iron functionalities will also be given,
together with the various application fields.
References
[1] Legrand U et al, 2016 Synthesis and in-situ oxygen
functionalization of deposited graphene nanoflakes
for nanofluid generation, Carbon 102 216-223
[2] Meunier J L et al, 2014 Two dimensional geometry
control of graphene nanoflakes produced by thermal
plasma for catalyst application, Plasma Chem Plasma
Proc 34 505-521
HTPP14 Munich: Session 10
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HTPP14 Munich: Session 11
151
Novel Plasma-Antimicrobial Solution and the Mechanisms of
Bacterial Inactivation
U K Ercan1,2
, A D Yost1,2
, J Smith3, H Ji
3, A D Brooks
1, S G Joshi
1,3*
1 Centre for Surgical Infections and Biofilms, Drexel University College of Medicine, Philadelphia, PA USA
2 Department of Chemistry, Drexel University, Philadelphia, PA, USA
3 Drexel School of Biomedical Engineering, Science, and Health Systems, Drexel University, Philadelphia, PA, USA
*[email protected] (presenting author)
Introduction
Recently we reported that non-equilibrium, non-thermal
plasma treated simple chemical solution generated strong
antimicrobial properties in the solution. Depending upon
the solution being treated, this solution contains reactive
oxygen species (ROS) and reactive nitrogen species
(RNS) which act probably synergistically. The solution’s
antimicrobial efficacies are retained for extended period of
time [1, 2, 3]. Here we present the findings on possible
mechanisms of inactivation of bacteria.
Material and Methods
The schematic set up of the device used for the experi-
ments is recently published [2, 4]. A range of ATCC ref-
erence strains, multidrug-resistant clinical isolates, and E.
coli K-12 and the specific gene deletion mutants were
tested for inactivation responses, using either the standard
colony count assay, XTT cell respiration assay, BacLight
Bacterial cell viability Live/Dead Assay, or biofilm inhibi-
tion assay. Cellular oxidative-stress changes were meas-
ured in E. coli for lipid peroxidation, a ratio of oxidized to
reduced forms of glutathione, disintegration of bacterial
DNA. The specific gene microarray and RT-PCR assays
were performed to investigate differentially expressed
genes during E. coli cellular responses to plas-
ma-antimicrobial solution.
Findings
The 3 min plasma-activated antimicrobial solution inacti-
vated all tested microbial strains upon contact (holding)
time of 15 min with bacteria. The antimicrobial efficacies
were strong enough to inactivated both planktonic and
biofilm-embedded forms. The solution stored for two years
at room temperature had inactivated 7 log of E. coli cells,
demonstrates that this solution has a place for commer-
cialization as potential biocides. During microarray analy-
sis the nitrosative-stress and oxidative-stress responsive
genes were found to be differentially expressed in E. coli.
The solution was able to induced membrane depolariza-
tion, membrane lipid peroxidation, oxidized glutathione,
reactive nitrogen species-specific marker, and disintegra-
tion of genomic DNA during dose-dependent kinetics in
E. coli.
Conclusion
The nonthermal plasma-activated solution have
broad-spectrum antibacterial property which is retained for
extended period of time and have potential to behave as
biocidal agent in infection control practice. The solution
completely inactivates E. coli through the activation of
RNS and ROS responsive genes. Further studies on
mammalian cell toxicities are being investigated.
Acknowledgements
Dr. Utku Ercan was supported through the fellowship from
Government of Turkey for higher education and research.
Authors thank Department of Surgery, Drexel University
College of Medicine and Coulter Foundation for partly
supporting this research. Part of the data was presented
earlier at different conference and submitted for doctoral
degree by UK Ercan to Drexel University of Philadelphia,
PA, USA
References
[1] Joshi et al., 2010 Control of methicillin-resistant
Staphylococcus aureus in planktonic form and bio-
films: a biocidal efficacy study of nothermal dielec-
tric-barrier discharge plasma. Am. J. Infect. Control 38
293-301
[2] Ercan et al., Nonequilibrium plasma-activated antimi-
crobial solutions are broad-spectrum and retain their
efficacies for extended period of time. Plasma Process
Polym. 10 544-555
[3] Yost AD and Joshi SG, 2015 Atmospheric nonthermal
plasma-treated PBS inactivates Escherichia coli by
oxidative DNA damage. PLoS ONE 10:e139903
[4] Ercan et al., 2016 Chemical changes in nonthermal
plasma-treated N-acetyl-cysteine (NAC) solution and
their contribution in bacterial inactivation. Sci Rep 6
20365
HTPP14 Munich: Session 11
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HTPP14 Munich: Session 11
153
Study of the radiation of high power arcs
Y Cressault1*
, J-M Bauchire2, P Freton
1, D Hong
2, H Rabat
2, A Gleizes
1
1 Université de Toulouse; UPS, INPT; LAPLACE (Laboratoire Plasma et Conversion d’Energie) ; 118 route de Narbonne,
F-31062 Toulouse Cedex 9, France
2 GREMI, UMR 7344, Université Orléans/CNRS, 14 Rue d’Issoudun, F-45067 Orléans
This work deals with the radiation emitted by a long high
power arc (2 m long) in air at atmospheric pressure with
the presence of metallic vapours such as copper, alumin-
ium or iron depending on the nature of the electrodes used.
We coupled experimental and theoretical studies in order
to determine the radiation energy of the arc, for several
spectral intervals. The comparison of both experimental
and theoretical results leads to represent the real arc as
three concentric homogeneous sources of radiation: pure
air plasma at temperature T0, air-metal plasma at temper-
ature T1 lower than T0 and a Blackbody source at temper-
ature lower than T1 representing the cloud of fumes. Dif-
ferent cases will be proposed for different current intensi-
ties and three kinds of electrodes.
The first part is devoted to the experimental study based
on the measurement of the radiation energy emitted by the
arc for several spectral bands 200 nm to the far IR part.
The set-up is presented in details: 3 types of electrodes
(25 mm in diameter) were used, for 4 current intensities
(from 4 kA to 40 kA rms), in ambient air. Electrical
measurements and high speed imaging were performed to
characterize the arc discharge: electrical input energy,
ablation of the electrodes, presence of fumes, and size of
the luminous zone. The radiation energy was measured
using two powermeters, positioned at 9.4 m from the
electrodes axis, and equipped with three different filters
defining 4 spectral intervals (IRC, IRA-B, Visible and
UV). Some conclusions can be done: the total electrical
energy does not really vary with the nature of the elec-
trodes at fixed current; the radiation emission depends
strongly on the presence of metallic vapours, influence
which is more pronounced with iron than aluminium or
copper electrodes (except for 40 kA); the main contribu-
tion are from the visible and the IRA-B parts with Fe and
Al electrodes, to which is added the UV part for copper.
Secondly, a theoretical study of the radiation energy of the
arc is proposed. Since the plasma is non-homogeneous
and non-isothermal according to the previous experi-
mental results, the plasma is divided into three sources of
radiation with different compositions (air-plasma, air
plasma and Blackbody), different sizes and temperatures.
From this assumption, we first estimated the local absorp-
tion coefficients (including the continuum radiation, the
atomic lines and spectral bands for the molecules [1]),
then the spectral radiance emitted by each source, and
finally the radiative fluxes received by an operator at a
distance between 1 and 10 m.
In order to enhance the understanding of the physical be-
haviour of this kind of arc, another smaller “laboratory”
configuration (10 cm long) has been studied. Furthermore,
we developed a first numerical 2D transient model of this
small arc. The aim is to obtain a helpful tool for the inter-
pretation of future experimental results. For this model,
the plasma is considered as a LTE fluid. Two cases are
considered: one for pure air and another for a mixture
5 %copper/95 %air. The radiative transfer equation is
solved by a hybrid method, mixing P1 and DOM method
considering mean absorption coefficients on some spec-
tral intervals. For the DOM, only few (2) directions are
considered during the calculation. This enables to de-
crease the computational time. In order to interpret spe-
cific results at a given time step, the number of directions
for the DOM is extended in a post-treatment process.
Then, radiative fluxes are obtained for several spectral
intervals for both cases (pure air and air/copper) and
compared with experimental data.
Acknowledgements
This work has been supported by the RTE-France Com-
pany (EDF transport).
References
[1] Cressault Y, Teulet Ph, Hannachi R, Gleizes A,
Gonnet J P, Battandier J-Y, 2008 PSST 16, 035016
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HTPP14 Munich: Session 11
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Plasma Propulsion System Development for Commercial Satellites D Lev
1*
1 Rafael - Advanced Defense Systems, Haifa, 3102102, Israel
Introduction
In recent years Rafael has been engaged in the develop-
ment of electric propulsion systems for various commer-
cial space applications such as satellite manoeuvring, or-
bit injection, drag compensation at low Earth orbits etc.
[1]. The electric thrusters developed are of the Hall
thruster type, an efficient and common type of plas-
ma-based thrusters [2]. These thrusters, and their sup-
porting components, are the focus of this presentation.
The system developed consists of thruster assemblies,
Power Processing Unit (PPU) and a Propellant Manage-
ment Assembly (PMA) responsible for controlling xenon
gas supply to the thruster unit [3]. The entire system de-
velopment scheme is based on the knowledge and exper-
tise obtained from the Venus satellite project [4]. Venus is
a plasma-propelled satellite (Figure 7) responsible for
vegetation monitoring by using a multispectral onboard
camera. The project is a joint Israeli-French project and
the satellite is scheduled for an early 2017 launch.
The “engine” of the current system development is the
Micro-satellite Electric Propulsion System (MEPS) pro-
ject in which an entire low power (150 W – 300 W) sys-
tem is developed, integrated and tested. The system,
which is dedicated for micro-satellites is a joint
Isareli-European project involving research and engineer-
ing groups from Israel, Italy and Greece [5]. All under the
supervision of the Israeli and European space agencies.
The two cardinal components developed are (1) low pow-
er Hall thrusters and (2) low current heaterless hollow
cathodes that directly support the thrusters. A brief expla-
nation on each is given hereafter. CAM200 Hall Thruster
The Hall thruster, denoted CAM200, is a low power Hall
thruster designed to operate in the 100 W – 300 W power
range [6]. The thruster uses ionized xenon gas to generate
discharge current in the 0.5 A - 1.1 A range.
CAM200 has a non-conventional structure, co-axial an-
ode, a fact that helps concentrate the generated plasma
towards the center of the thruster; therefore increasing its
thrust generation efficiency. Thanks to this unique feature
CAM200 is capable of generating thrust higher than other
conventional Hall thruster while reaching efficiencies up
to 50 %. Heaterless Hollow Cathode
Hall thruster require an accompanying electron generator
responsible for thruster ignition and ejected ion beam
neutralization. The electron source, also referred to as the
‘cathode’ is typically a hollow cathode that uses a fraction
of the xenon propellant to initiate and sustain the main
thruster discharge. Conventional cathodes require an ex-
ternal heater to heat up a low work function material,
embedded in the cathode, release electrons and ignite the
thruster. However, these heaters are limited by their
maximum number of ignition cycles, require power of
tens of watts and take minutes to heat up before thruster
ignition is possible. For this reason Rafael is developing a
heaterless hollow cathode that uses internally-generate
discharge to heat the electron emitter.
The cathode, also named the RHHC [7], is made of re-
fractory metal, generates current of 0.5 A - 1.1 A, ignites
within tens of seconds and can operate continuously for
thousands of hours. References
[1] Herscovitz J, Zuckerman Z and Lev D, Electric Pro-
pulsion Developments at Rafael". Proc. 34th
IEPC,
Japan, IEPC-2015-030
[2] Goebel D and Katz I, 2006 Fundamentals of Electric
Propulsion: Ion and Hall Thrusters. JPL Space Sci-
ence and Technology Series, Jet Propulsion Labora-
tory & California Institute of Technology
[3] Alon G, Lev D, Eytan R, Appel L, Albertoni R and
Misuri T. Development of Low Power Electric Pro-
pulsion System for Micro-Satellites, Proc. 66th
IAC,
Israel, Interactive Presentation
[4] Warshavsky A, Rabinovitch L, Reiner D, Herscovitz J,
and Appelbaum G, 2010 Qualification and Integration
of the Venus Electrical Propulsion System, Proc.
Europ. Space Propulsion Conf. (SP), Spain
[5] Misuri T, Andrenucci M, Herscovitz J, Waldvogel B
and Dannenmayer K, MEPS Programme - New Ho-
rizons for Low Power Electric Propulsion Systems,
Proc. 34th
IEPC, Japan, IEPC-2015-491
[6] Lev D, Eytan R, Alon G, Warshavsky A and Appel L,
CAM200 Hall Thruster – Development Overview,
Proc. 66th
IAC, Israel, IAC-15-C4.4.4
[7] Lev D, Alon G, Mikitchuk D and Appel L, Develop-
ment of a Low Current Heaterless Hollow Cathode for
Hall Thrusters, Proc. 34th
IEPC, Japan,
IEPC-2015-163
Figure 7: Picture of the Venus satellite propulsion system.
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