synthesis and consolidation of nanopowders: approaches and methods cracow, 2014 michail alymov isman
TRANSCRIPT
SYNTHESIS AND CONSOLIDATION
OF NANOPOWDERS: APPROACHES AND METHODS
Cracow, 2014
Michail Alymov
ISMAN
Outline
1. Introduction.2. Synthesis of nanopowders.3. Processing of bulk nanostructured materials. 3.1. Consolidation of nanopowders. 3.1.1. Pressing at room temperature. 3.1.2. Sintering without pressure. 3.1.3. Sintering under pressure.4. Properties of consolidated nanomaterials.5. Summary.
Classification of nanomaterials
1. Powders.
2. Layers and coatings.
3. Composite materials.
4. Bulk materials.
Powder metallurgy = synthesis of powders + consolidation of powders.By powder metallurgy methods we can produce all kinds of nanomaterials.
R.W. Siegel, Proc. Of the NATO SAI, 1993,v.233, р.509
Methods Technologies Materials
Powder metallurgy Consolidation of nanopowders:
Pressing and sintering,
Pressure sintering
Metals and alloys, ceramic, metal-ceramic, composites, polymers
Crystallization from amorphous state
Crystallization of amorphous alloys,
Consolidation of amorphous powders with further crystallization
Metallic materials
able to bulk amorphisation.
Severe plastic deformation
Equal channel angular pressing,
Torsion under high pressure,
Multiple all-round forging.
Metallic materials
Nanostructurisation by precision heat treatment and thermomechanical treatment
Heat treatment.
Thermomechanical treatment
Metallic materials
METHODS FOR PROCESSING OF BULK NANOSTRUCTURED MATERIALS
PressureTemperature
Time
Powder
Size of Ni particles = 70 nm
Bulk material
Grain size = 100 nm
Hydroxyapatite ceramics from nanopowders
Pressure 3 GPaSintering temperature 670°С
Grain size 35-50 nmMicrohardness 5,8 GPa
Fomin A.C., Barinov C.M., Ievlev V.М. a.o. 2008.
After pressing After sintering
Methods for synthesis of nanopowders
– SHS (self-propagating high temperature synthesis), – chemical – metallurgical method- plasma-chemical synthesis – mechanical alloying - electrical explosion of wires - vaporization-condensation technique - flowing gas evaporation technique - vapor phase synthesis – cryochemical synthesis - sol-gel method - hydrothermal synthesis and others
There are many methods for synthesis have been developed to produce nanopowders. The synthesis routes are diverse and result in nanoparticles with a range of characteristics, such as size, size distribution, morphology, composition, defects, impurities, and agglomeration (“soft” and “hard”). By now, several tens of methods have been developed for the synthesis of metallic, ceramic, cermet, and other nanopowders. Each method is characterized by its own advantages and disadvantages. Some methods are reasonably used for the preparation of metal powders, while other methods are useful for ceramic powders.
The ratio between the average particle size and performance of methods
0 200 400 Size of particles, nm
200
0
400
Levitation-jet
method
EEW
4
Plasma-chemical
Chemical and metallurgical
800SHS
Calcium-hydride method
Evaporation-condensation
Alymov M.I. Composites and Nanostructures, 2012, v.3.
METHODS for the NANOPOWDERS CONSOLIDATION
Uniaxial pressing: static, dynamic, vibration
Isostatic pressing
Extrusion
Sintering under pressure
Spark plasma sintering
Sock wave pressing
Severe plastic deformation
Features of the nanopowders consolidation
Impurities play an important role in densification.
Agglomeration of nanoparticles into clusters.
Low dislocation density.
The possibility of new or different mechanisms of densification.
Diffusion-induced grain-boundary migration and boundary-energy-induced rotations may alter densification mechanisms.
Cold pressing - uniaxial (static, dynamic, vibrational),
- multiaxial (hydrostatic, gasostatic),
- severe plastic deformation,
- cold rolling.
Influence of average iron particle diameter on the density of compacts
M.I. Alymov, 1990
0 0,4 0,8 1,2 1,6 Pressure, GPa
100
60
20
Rel
ativ
e d
ensi
ty, %
23 nm
26 nm28 nm
60 nm
120 nm
1 mkm40 mkm
Diameter of dislocation free iron particle is equal to 23 nm
The friction between the nanoparticles substantially affects the densification of nanopowders. The contribution of plastic deformation to the densification of nanopowders is insignificant since the nanoparticles are free from dislocations and they cannot be deformed as coarse particles due to the movement of dislocations.
Consolidation process of nanopowders is strongly affected by:
- particle size distribution,
- concentration of impurities,
- surface conditions,
- particle shape,
- pressing technique.
Sintering mechanisms
1 - surface diffusion, 2 - volume diffusion from surface, 3 - vapor transport from surface,4 - grain boundary diffusion, 5 - volume diffusion, 6 – dislocation diffusion
Alymov M.I., Letters on Materials. 2013.
Sintering of gold
nanoparticles
Influence of pressure on sintering
Sintering temperature
100
Den
sity
, %
Sintering under pressure
90
80
70Т1
Sintering without pressure
Т2 < Т1
d1d2 < d1
Equipment for the sintering under the pressure
thermocouple
bellows
entrance of gas
sample
anvil
yield of gas
vessel
heating element
punch
padding
Pressure
Pressure sintering of iron nanopowder
400 500 600 700 800 Temperature, °С
100
Den
sity
, %
380 MPa
90
80
70
60
0 MPa
90 MPa
280 MPa
М.И. Алымов, ФХОМ, 1997
Influence of the mode of deformation on sintering
HIP – pressing in dies – forging – extrusion - ECAP
Hydrostatic component of pressure
Tangential component of pressure
Gas extrusion method
gas
chamber
sample
diedie block
Compacts of iron and nickel nanopowder after extrusion
Iron
Nickel
10 cm
Nickel nanopowder green compact after hydrostatic pressing
TEM microstructure image of nickel nanopowder compact after hot forging
Grain size near 70 nm
MECHANICAL PROPERTIES OF THE COMPACTS
Method Material Particle size, mkm
Grain size, mkm
в ,MPa
, %
Hot isostatic pressing
Ni
6 25 440 36
0,06 1 545 7
Fe
40 55 350 41
0,04 1 460 1
Extrusion Ni 0,06 0,1 700 15
Mechanical properties of nanocrystalline and coarse-grained nickel
Nano-grained Coarse-grained
, MPa 530 80
B , MPa 625 400
, % 22 40
ψ, % 19,5 -
Kc , MPa∙m1/2 82,3 51,7
Toughness, J/cm2 63-66 198-203
The crack growth resistance for nanocrystalline Ni is on 30% higher the crack growth resistance coarse grained Ni.
Ni
Valiev R. 2001
Fe
Cu
Ult
imat
e st
ren
gth
, M
Pa
Relative elongation , %
Hardness of WC-8%Co hard alloy depends on the size of WC-grain
0 0,5 1,0 1,5 2,0 Size of WC-grain, mkm
Har
dn
ess
HV
, GP
a
14
16
18
20
22
24
26
Alymov M.I. a.o. Composites and Nanostructures. 2012.
SHS pressure sintering
3
4
21
Sherbakov V.А.
1 - tungsten spiral initiating the SHS reaction
2 - tablet from powders of the initial reactants
3 - insulating porous medium (sand);
4 - mold.
Before SHS extrusion
Stolin A.M.
Initial charge billets
Form of a matrix
Ignition system
The mold assembly
Guide caliber
After SHS extrusion
Stolin A.M.
Material after SHS (press residue)
Extruded material (finished product)
Effectiveness for bulk nanopowder materials
Materials EffectivenessHard alloys Increase of hardness by a factor of 5-7
High strength steels and alloys Increase of strength by a factor of 1,5-2
Ceramic materials Formability as for titanium alloys
Nanopowder materials with special properties
Mechanical, chemical, optical and other properties
Wear resistance coatings Increase of resistance by a factor of 170
Thank you for your attention
Dziękuję za uwagę