New Preparation of Powders with Fine Particles and Their High-Pressure Sintering Using SHS, SPS, and HIP

Abstract

Various kinds of powder production methods (solution techniques) have been developed and utilized to prepare single-phase (monolithic or solid solution) and composite powders consisting of fine particles with a sharp sizedistribution; sol-gel techniques using metal alkoxides and acetylacetonates, and a newly developed hydrazine method.The latter solution technique has some merits i.e. easy and simple process to produce fine sinterable powders at relatively low cost due to use of aqueous metal salts as starting materials. By adopting these powder preparation techniques, dense structural materials and functional perovskite oxides (rare-earth chromites), nanocomposite materials with high densities have been fabricated.On the other hand, high-pressure techniques such as self-propagating high-temperature synthesis (SHS), spark plasma sintering (SPS), hot isostatic pressing (HIP), and their combined use have also been used for the fabrication of dense structural materials, i.e., silicides, nitrides, aluminides, borides, such as MoSi2, α-Ti(N), NiAl/ZrO2(3Y), CrB, etc. The present paper describes briefly some characteristics of powders thus prepared, and mechanical properties of condensed materials fabricated using SHS, SPS, and HIP in relation to their microstructures.