1. SYNTHESIS AND CONSOLIDATION OF NANOPOWDERS: APPROACHES AND METHODS Cracow, 2014 Michail Alymov ISMAN

2. 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.

3. 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

4. MethodsTechnologiesMaterials Powder metallurgyConsolidation 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

5. Pressure Temperature Time Powder Size of Ni particles = 70 nm Bulk material Grain size = 100 nm

6. Hydroxyapatite ceramics from nanopowders Pressure 3 GPa Sintering temperature 670°С Grain size 35-50 nm Microhardness 5,8 GPa Fomin A.C., Barinov C.M., Ievlev V.М. a.o. 2008. After pressing After sintering

7. 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

8. 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.

9. The ratio between the average particle size and performance of methods 0 200 400 Size of particles, nm Capacity, g / h 200 0 400 Levitation-jet method EEW 4 Plasma- chemical Chemical and metallurgical 800 SHS Calcium-hydride method Evaporation- condensation Alymov M.I. Composites and Nanostructures, 2012, v.3.

10. 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

11. 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.

12. Cold pressing - uniaxial (static, dynamic, vibrational), - multiaxial (hydrostatic, gasostatic), - severe plastic deformation, - cold rolling.

13. 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 Relative density, % 23 nm 26 nm 28 nm 60 nm 120 nm 1 mkm 40 mkm Diameter of dislocation free iron particle is equal to 23 nm

14. 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.

15. Consolidation process of nanopowders is strongly affected by: - particle size distribution, - concentration of impurities, - surface conditions, - particle shape, - pressing technique.

16. 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.

17. Sintering of gold nanoparticles

18. Influence of pressure on sintering Sintering temperature 100 Density, % Sintering under pressure 90 80 70 Т1Т1 Sintering without pressure Т 2 < Т 1 d1d1 d 2 < d 1

19. Equipment for the sintering under the pressure thermocouple bellows entrance of gas sample anvil yield of gas vessel heating element punch padding Pressure

20. Pressure sintering of iron nanopowder 400 500 600 700 800 Temperature, °С 100 Density, % 380 MPa 90 80 70 60 0 MPa 90 MPa 280 MPa М.И. Алымов, ФХОМ, 1997

21. Influence of the mode of deformation on sintering HIP – pressing in dies – forging – extrusion - ECAP Hydrostatic component of pressure Tangential component of pressure

22. Gas extrusion method gas chamber sample die die block

23. Compacts of iron and nickel nanopowder after extrusion Iron Nickel 10 cm Nickel nanopowder green compact after hydrostatic pressing

24. TEM microstructure image of nickel nanopowder compact after hot forging Grain size near 70 nm

25. MECHANICAL PROPERTIES OF THE COMPACTS MethodMaterialParticle size, mkm Grain size, mkm  в, MPa , % Hot isostatic pressing Ni 62544036 0,0615457 Fe 405535041 0,0414601 ExtrusionNi0,060,170015

26. Mechanical properties of nanocrystalline and coarse-grained nickel Nano-grainedCoarse-grained  , MPa 53080  B, MPa 625400 , % 2240 ψ, %19,5- K c, MPa ∙m 1/2 82,351,7 Toughness, J/cm 2 63-66198-203 The crack growth resistance for nanocrystalline Ni is on 30% higher the crack growth resistance coarse grained Ni.

27. Ni Valiev R. 2001 Fe Cu Ultimate strength, MPa Relative elongation, %

28. 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 Hardness HV, GPa 14 16 18 20 22 24 26 Alymov M.I. a.o. Composites and Nanostructures. 2012.

29. SHS pressure sintering 3 4 2 1 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.

30. Before SHS extrusion Stolin A.M. Initial charge billets Form of a matrix Ignition system The mold assembly Guide caliber

31. After SHS extrusion Stolin A.M. Material after SHS (press residue) Extruded material (finished product)

32. Effectiveness for bulk nanopowder materials MaterialsEffectiveness Hard alloysIncrease of hardness by a factor of 5-7 High strength steels and alloysIncrease of strength by a factor of 1,5-2 Ceramic materialsFormability as for titanium alloys Nanopowder materials with special properties Mechanical, chemical, optical and other properties Wear resistance coatingsIncrease of resistance by a factor of 170

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