vekas

1st Nanoforum Workshop, Sinaia, Romania, 5-7 October, 2003

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MAGNETIC NANOFLUIDSPreparation, properties and some

applications

L.VÉKÁS and Doina BICA

Laboratory of Magnetic Fluids Centre of Fundamental and Advanced Technical Research, Romanian Academy,

Timisoara Division, Timisoara, Romania


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Magnetic nanofluids

� Magnetic nanofluids (magnetic fluids, ferrofluids): ultrastable colloidal suspensions of magnetic nanoparticles (3-15 nm) in non-polar and polar carrier liquids; S. Pappel, NASA (1965), Rosensweig, Nestor, Timmins (1965)

� Nanofluids- novel enhanced heat transfer fluids; S.U.S. Choi, Argonne National Lab.(1995)

� Magnetizable complex fluids: magnetic fluids, emulsions, magnetofluidic composites, magneto-rheological nano/micro fluids

� “Magnetic” soft matter �a special category of soft matter composites: magnetic nanofluids�magnetorheological fluids�magnetic nanocomposites�magnetic gels�


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Magnetic nanofluids

� New MHD: ferrohydrodynamics, Neuringer and Rosensweig (1964)σ=0 µ≥µ0

an extension of classical MHD:σ≥0 µ=µ0

� Magnetic fluids as magnetizable complex fluids with �internal” angular momentum →non-symmetrical stress tensor


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Magnetic nanofluids

Ferrohydrodynamics-specific phenomena


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Magnetic nanofluids


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Magnetic nanofluids

Preparation of magnetic nanofluids

� Synthesis of magnetic nanoparticles by chemical condensation

� Stabilization/dispersion of magnetic nanoparticles in various carrier liquids


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Magnetic nanofluids

Aqueous solutions

Fe3+, Fe2+ CoprecipitationNH4OH

(solution 25%)

Subdomain Fe3O4nanoparticles

Surfactant

(pure oleic acid 96%)353 K

Sterical stabilisation

(chemisorption)

Phase separation

Magneticdecantation

Aqueous solution of

residual salts

Monolayer coveredmagnetic particles

Distilled water

t = 70 - 80o CRepeated washing

Magnetic decantation Aqueous solution

residual salts

Monolayer coveredmagnetic nanoparticles +

free oleic acid

Acetone Extraction

Magnetic decantation Acetone, water,

free oleic acid

Stabilised magneticnanoparticles

Hydrocarbon Dispersion

t=120-130oC

Primary monolayerstabilised magnetic fluid

on light hydrocarboncarrier

Magnetic decantation /filtration

Repeated flocculation /redispersion of surfacted

nanoparticles

Free oleic acid

NONPOLAR PURIFIED MAGNETIC FLUID

Preparation procedure of nonpolar magnetic fluids


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Magnetic nanofluids

- Coprecipitation Fe2+, Fe3+, NH4OH sol. 25%- Sterical stabilisation, (chemisorbtion, oleic

acid 96%)- Phase separation- Repeated washing- Dispersion

Primary magnetic fluid onlight hydrocarbon carrier

- Magnetic decantation- Filtration- Repeated flocculation /

redispersion of surfactednanoparticles

Free oleic acid

Nonpolar purifiedmagnetic fluid

Acetone Flocculation

Magnetic decantation Acetone + hydrocarbon

Monolayer stabilisedmagnetic nanoparticles

DBS or PIBSA (C≥8) - Secondary stabilisation(physical adsorbtion)

- Dispersion

Alcohols C3-C10/HVO/

Diesters(DOA/DOS)

MF/HIGHVACUUM OIL

MF/ALCOHOLS(Polialcohols)

MF/DIESTERS(DOA, DOS)

VEGETALOILS

Fe3+, Fe2+ solutions

θ=75-80oCNanoparticle synthesis

Fe3O4, γ- Fe2O3

NH4OH 25 %

Magneticdecantation

Aqueous solution of

residual salts

Distilled water

t = 70 - 80o CMagnetic nanoparticles

Repeated washingup to pH=8.5

Magnetic decantation Aqueous solution

residual salts

DBS and/or lauric

acid (LA) θ=75oC

Double layer stabilizationand dispersion

Ultrasonation (2)

MF/Water (primary)

Magnetic decantation/filtration

MAGNETIC FLUID/Water

Preparation procedure of polar magnetic fluids Preparation procedure of water based magnetic fluids


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Magnetic nanofluidsMAGNETIC FLUIDS

for fundamental and applied researches

Medium and high concentration magnetic fluids (selection)

Nr. Indicative Carrier liquid Nominalmagnetization (G)

* 1. TM � P petroleum/nonpolar 200-400-800* 2. TM � K kerosen/nonpolar 200-400-800* 3. TM � T toluen/nonpolar 200-400-800

4. TM � Izo izooctan/nonpolar 200-400-8005. TM � H heptan/nonpolar 200-400-8006. TM � Cyc cyclohexan/nonpolar 200-400-8007. TM - TR � 30 transformer

oil/nonpolar200-400-800

8. TM � DHN decahydronaphtalene/nonpolar

200-400-800

9. TM � HVO high vacuum oil/polar 200-400-80010. TM � DOA dioctyladipate/polar

(synthetic oil)100-300-700

11. TM � DOS dioctylsebacate/polar(synthetic oil)

100-300-700

12. TM � Prop propanol/polar 100-300-60013. TM � But butanol/polar 100-300-60014. TM � Pent pentanol/polar 100-300-600

** 15. TM � Hexa hexanol/polar 100-300-60016. TM � Hept heptanol/polar 100-300-600

** 17. TM � Octa octanol/polar 100-300-60018. TM � Nona nonanol/polar 100-300-60019. TM � Deca decanol/polar 100-300-60020. TM � H2O water/polar 50-300-600

* Specially developed for inductive sensors (AEM Co, Timişoara). ** Specially developed for capacitive sensors (Inst. for Space Sciences, Bucharest).


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Magnetic nanofluids

Structural investigations

� Transmission electron microscopy (TEM): size distribution of magnetic nanoparticles

� Small angle neutron scattering (SANS) and small angle X-ray scattering (SAXS):structure of surfactant covered nanoparticles, ordering processes, particle interactions and pre-existing or field induced agglomerates, interface structures


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Magnetic nanofluids

The Guinier plots of ln(In(Q,x)) versus Q2 for several values of D-benzene

volume fraction (0, 0.2, 0.5, 0.8 and 1.0). Good straight lines are evident.

JINR Dubna

Guinier plot of SAXS measurement of cyclohexane based magnetic

fluid. The linearity up to small q indicates that clusters are absent.

Debye Inst. Utrecht


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Magnetic nanofluids

Mean intensity <I> as a function of time τ after demagnetization for water based magnetic fluid sample (a) and pentanol based magnetic fluid sample (b). Horizontal lines in the graphs correspond to the mean intensity value of the initial ferrofluids before they are set in the magnetic field: ■, □ - applied field (B=1.2 T); �, ····· - zero field (B=0 T).Budapest Neutron Center

(a) Water based magnetic fluid (b) Pentanol based magnetic fluid


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Magnetic nanofluids

-0,02 0,00 0,02 0,04 0,06 0,08 0,10 0,12 0,14 0,16 0,181E-8

1E-7

1E-6

1E-5

1E-4

1E-3

0,01

0,1

1

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Ref

lect

ivity

qz, A-1

Structure of magnetite/oleic acid/benzene magneticnanofluid at the interface with silicon (1)

Typical scattering pattern (Sample 1) from the interface of silicon and

ferrofluids under study.

Example of the experimental reflectivity curve (Sample 1) and model calculations. Solid line

corresponds to the best fit of the two-layer model; dashed line corresponds to the model with

additional surfactant layer.

ILL - Grenoble


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Magnetic nanofluids

-40 -20 0 20 40 60 80 100 120 140-1

0

1

2

3

4

5

6

7

ρ ×

10−6

A-2

h,A

OA

C6D

6

Fe3O4

<ρ>

-40 -20 0 20 40 60 80 100 120 140-1

0

1

2

3

4

5

6

7

ρ ×

10−6

A-2

h,A

OA

C6D6

Fe3O

4

<ρ>

Structure of magnetite/oleic acid/benzene magneticnanofluid at the interface with silicon (2)

Scattering density profiles for Samples 1 � 3 (a) and 4, 5 (b). Color solid lines show values of the bulk scattering length density of the fluids and its components.

ILL - Grenoble


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Magnetic nanofluids

The normalized sedimentation velocity U/Uoas a function of the volume fraction φ of the aqueous magnetic dispersions FF7-H2O, FF7-TMA and FFWA. The solid line is the result of a linear fit

The normalized sedimentation velocity U/Uo against the volume fraction of theferrofluid MaS in 1-pentanol. The solid line is the result of a linear fit

Debye Inst. Utrecht


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Magnetic nanoparticles

Flow properties

� Dynamic viscosity vs. particle volume fraction

� Dynamic viscosity vs. temperature

� Effective viscosity vs. applied magnetic field induction, magnetoviscous effect

� Field induced structure formation, non-Newtonianbehaviour, degree of colloidal stability

� Fits to various semi-empirical and theoretical formulas


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• VAND( )

−−+

=h

2h122h1

o Q1kkrk

expϕ

ϕϕηη

− η - the viscosity of the magnetic fluid− η0 - the viscosity of the carrier liquid− ϕh=p⋅ϕρ - the hydrodynamic volume fraction− ϕρ - the volume fraction of the dispersed solid particles− p - a proportionality factor− Q=0.609 - a constant that characterizes the hydrodynamical interactions− k1=2.5 - the shape factor for isolate spherical particles− r2=4 - a time constant for binary collisions− k2=3.175 - the factor for the ensemble of two colliding particles

3h

d21p

+== δ

ϕϕ

ρ CLS

CLMF

ρρρρϕ ρ −

−=

− δ - surfactant layer thickness− d - mean physical diameter of magnetic nanoparticles− ρMF - magnetic fluid density− ρCL - carrier liquid densityρS - solid particles density


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• KRIEGER-DOUGHERTY[ ] x

xh

o 1expϕη

ϕϕηη

−

−=

− ϕx - the maximum packing fraction (the fraction at which η→∞)− [η] - intrinsic viscosity

• QUEMADA

2

xh

o 1exp−

−=

ϕϕηη

• CHOW

−+

−

=x

2h

2h

hh

oA1

A1

5.2expϕϕ

ϕϕϕηη

- A - the coupling coefficient between particles


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VAND QUEMADA KRIEGER-DOUGHERTY CHOW

t

(oC)

p=ϕϕϕϕh/ϕϕϕϕρρρρ ⇒⇒⇒⇒

(fitparameter)

δδδδ=(p1/3-1)d/2

(effective stabilizantlayer thickness) (nm)

ϕϕϕϕmQ

(max. hydrodyn. vol.fraction)

ϕϕϕϕmK

(max. hydrodyn.vol. fraction)

[ηηηη]

(intrinsicviscosity)

A

(fit with ϕϕϕϕmQ)

A

(fit with ϕϕϕϕmK)

-10 3.897 2.466 0.703 0.670 2.858 3.186 3.317

0 3.763 2.389 0.693 0.654 2.886 3.491 3.663

10 3.620 2.305 0.685 0.637 2.925 3.747 3.975

20 3.541 2.255 0.678 0.625 2.953 3.910 4.170

30 3.425 2.182 0.675 0.614 2.971 4.051 4.356

40 3.366 2.146 0.672 0.607 2.980 4.135 4.460

50 3.308 2.108 0.669 0.600 2.988 4.208 4.552

60 3.272 2.083 0.668 0.596 2.997 4.241 4.599

70 3.251 2.067 0.667 0.593 3.000 4.261 4.627

Atheor(Chow)=4.67

Volumic concentration dependence of dynamicviscosity for pentanol magnetic fluids


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Magnetic nanofluids

Magnetic properties

� Full magnetization curves

� Low field reduced magnetization curves, particle agglomerates

� Fits to theoretical models


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Magnetic nanofluids

Reduced magnetization curves of high concentration C3- C10alcohol based magnetic fluids


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Magnetic nanofluids


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Magnetic nanofluids

MF water (1985): 50.38 kA/m (630 G)MF pentanol (2000): 56.92 kA/m (715 G)MF warter (1999): 14.95 kA/m (190 G)

Full magnetization curvesof strongly polar magnetic fluids


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Magnetic nanofluids

Initial susceptivity vs. physical volume fraction. Comparison between polar (Pent) and nonpolar MFs (TR30)

The non-linear behaviour can be a result f both particle interaction and aggregate formation in the samples. A

preliminary fit with Ivanov�s model (Col. J., 2001) shows that the interactions might play the main role.


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Initial susceptibility vs. magnetic volumefraction for Pentanol MF sample

Magnetic nanofluids

Measured initial susceptibility for Pent samples, and calculated initial susceptibilities with various models vs. magnetic volume fraction. For

Pent based samples the deviation from ideal behaviour is mainly due to particle interactions; Thermodynamic Perturbation Theory and Mean

Spherical Model almost fit the data.


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Magnetic nanofluids

� Non-magnetic fluid/magnetic nanofluidinterfaces in magnetic field

� Bubbles and drops in magnetic field

� Nucleate boiling of magnetic nanofluids in applied magnetic field

� Magnetically controlled boiling in reduced gravity conditions

Magnetically controlled heat transfer processes


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Magnetic nanofluids

Above: Without buoyancy or convection, boiling fluids behave quite differently in space. Image courtesy NASA Glenn Research Center .


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Magnetic nanofluids

Heat transfer in the presence of an electric field Heat transfer in the presence of a magnetic field

( ) EfugTpuutu rrrrrr

+∇+−−∇=

∇⋅+

∂∂ 2, ηρρρ

0=∇ ur

p

e

cETaTu

tT

ρσ 2

2 +∇=∇⋅+∂∂ r

0Eε∇ ⋅ =r

0E∇× =r

0vJt

∂ ρ∂

∇ ⋅ + =r

( )Tpp ,ρ=

( ) MfugTpDt

uD rrrr

+∇+−−∇= 2, ηρρρ (1)

0=∇ ur (2)

( ) Φ+∇⋅∇=

∂∂+ T

DtDH

TM

DtDTc

Hp κµρ 0 (3)

0=⋅∇ Br

(4)

0=×∇ Hr

(5)

( )HTMM ,= (6)

( )Tpp ,ρ= (7)

Governing Equations of Heat Transfer in the Presence of an External Field (Electric or Magnetic)


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Magnetic nanofluids

Experimental bench :1 � compressor, 2 � reservoir, 3 � pressuregauge,4 � electromagnet power supply,5 � gaussmeter; 6 �Hall probe,7 � electromagnetic poles, 8 � precision valve,9 � experimental cell,10 � flow regulating valve,11 � PC with NIST DAQ system,12 � flow transducer,13 � pressure transducer

N S

1 2 3 4 5 6

7

8

9

10 11 12 13

Experimental researches regarding the effects of a magnetic field on the dynamics of gas bubbles injected in a complex magnetizable fluid


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Magnetic nanofluids

The influence of magnetic induction and of its gradient on the relative

bubble emission frequency

Variation of the relative volumic gas flow rate through a submerged needle

in magnetic fluid in nonuniformmagnetic field

Behaviour of complex magnetizable nanofluidsin microgravity conditions


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Magnetic nanofluids

Lattice Boltzmann model for the simulation of interfacial phenomena in magnetic fluids

Deformation of a magnetic fluiddrop in magnetic field

Magnetic field induced deformation of gas bubbles in magnetic fluid

Development of normal field instability


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Magnetic nanofluids

Applications� Magnetofluidic leakage-free rotating seals

� Magnetogravimetric separations, low noise MF bearings

� Acceleration/inclinations sensors

� Aerodynamic sensors: differential pressure, volumic flow

� Magnetic nanofluids for polymeric nanocomposites

� Nano/micro-structured magnetorheological fluids for semi-active vibration dampers

�Biomedical applications in plant genetics (e.g.biostimulators) and veterinary medicine(e.g. radioprotectingand antiinflammatory composites, magnetically driven drugs(citostatics))


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|∇ H|≅ 109A/m2

Magnetic nanofluids

Principle of magnetic fluid rotating seals

High vacuum magnetic fluidfeedthrough - ROSEAL Co.


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Magnetic nanofluids

Magnetorheological suspensions damping mechanisms


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Magnetic nanofluids

Flow behaviour of nano/micro-structuredmagnetorheological fluids for semi-active vibration dampers


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Magnetic nanofluids

X 5 X 20 X 50Optic microscopy of nanomagnetic composite

Optic microscopy of reinforced nanomagnetic compositeX 5 X 20


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Magnetic nanofluids

Conclusions

Magnetic nanofluids and compositesare magnetic soft matter materials with magnetically controllable fluid propertieswide range of technological and biomedical applications


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Magnetic nanofluids

⇒ Lab. of Magnetic Fluids - Romanian Academy, Timisoara Division;⇒National Center for Engineering of Systems with Complex Fluids � Univ. �Politehnica� Timişoara; ⇒Univ. of Agricultural Sciences and Veterinary Medicine, Timisoara;⇒Romanian Space Agency; Institute of Space Sciences �Bucharest;⇒ZARM � Univ. Bremen; Van�t Hoff Lab. � Univ. Utrecht; Frank Lab. � JINR, Dubna; Budapest Neutron Center (Hungarian Academy of Sciences); ILL Grenoble; Inst. of Experimental Physics (Slovak Academy of Sciences) �Kosice; Univ. Pisa � Dept. of Energetics;⇒Industrial partner: ROSEAL Co. Odorheiu Secuiesc, Romania (manufacturer of rotating seals with nanomagnetic fluids).

Research partners


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Magnetic nanofluids

• Prof.Dr.Eng. Ioan ANTON, member of the Romanian Academy, Director of CFATR Timisoara

• Prof.Dr.Eng. Ioan DE SABATA

Acknowledgements


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Magnetic nanofluids

LMF - CFATR Timisoara:Dr. Doina BICA, Senior scientist; Dr. Victor SOFONEA, Senior scientist;Dipl.-Eng. Iosif POTENCZ, Senior scientist;Dr.-Eng. Calin POPA, Senior scientist; Dipl.-Phys. Artur CRISTEA, Researcher, PhD student

NCESCF - Univ. Politehnica Timisoara:Dr.-Eng. Floriana STOIAN, Assoc. Prof.;Dr.-Eng. Gheorghe POP, Assoc. Prof.; Dr. Daniela S.-RESIGA, Assoc. Prof.; Dr.-Eng. Nicolae CRAINIC, Assoc. Prof.; Dipl.-Phys. Oana MARINICA, Researcher, PhD student; Dr. Marin LITA, Assoc. Prof.; Dipl.-Eng. Virgil STOICA, PhD student

Univ. of Agricultural Sciences and Veterinary Medicine Timisoara:Dr. Gallia BUTNARU, Prof. and Dr. Mariana SINCAI, Prof.

Industrial partner ROSEAL Co., Odorhei: Dipl.Eng. IstvanBORBATH, director and group leader

Timisoara MF research team:

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