Authors O.V. Karban, E.I. Salamatov, G.N. Konygin, O.Yu. Goncharov, F.Z. Gilmutdinov
Month, Year 10, 2016 @en
Index UDC 546.621/623:17
DOI 10.18522/2311-3103-2016-10-4052
Abstract Powder compaction method used for synthesys of thermocrystals provides control of the structure formation process, grain and pore size, it permits to realize the required material struc-ture which forms the gap on phonon spectrum. Proposed is the new method of creation of thermocrystals based on the composites Al2O3+хFe, it permits to preserve the nano-disperse structure of material in absence of spinel phase in interface areas. The process involves a mixture of aluminium oxide mechanoactivation powders and pre mehanosynthesized nanocrystalline iron carbide followed by compaction and sintering. The cementite reduction followed by decomposition of iron and formation of metal particles in a ceramic matrix during the sintering process inhibits the formation of a spinel phase. The homogeneous powders were obtained by mechanical activation of the mixture of aluminium oxide and nano-crystal Fe3C. The homogeneous structure of the powder formed in the process of mechanical activation contributes to the consolidation of a metal grains and ceramic. Finishing structure and phase composition of the composites are determined by compaction. Application of methods of magnetic-impulse pressing (MIP) and uniaxial dry pressing with ultrasonic exposure (US) allows us to obtain the compacts with apparent density 0,5–0,65 without any change in the phase composition of compacts. The composition and size of metal particles are determined by the method and conditions of compacting. For the MIP-samples, decomposition of cementite is observed during sintering, resulting in iron reduction and formation of -iron metal particles in ceramic matrix. For US-samples, particles of irregular solid solution Fe-Al are formed. It was shown that unlike sintering of Al2O3+хFe, if content of Fe3C in initial mechanical mix of powders is more than 5% the spinel phase is not generated during sintering.

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Keywords Thermocrystals, composites Al2O3+хFe, nanoceramics.
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