Abstract - Puszynski This is a study of the fundamentals of high-pressure synthesis of silicon- nitride-based ceramics in a self-sustaining regime. Aspects investigated include particle-particle-gas interactions, product morphology, and phase composition of combustion-synthesized ceramics. The effort focuses on the effects of combustion conditions and various additives, factors that may alter crystal growth and the formation mechanisms of silicon-nitride-based ceramics. Quantitative data are obtained on the formation and crystal growth of silicon nitride, silicon oxynitride, sialon, and silicon carbide during self- sustaining, high-pressure nitridation of silicon powders containing amounts of oxides, nitrides, halogens, and/or carbon. Models are developed to describe the complex reaction and diffusion processes on a particle level during formation of single-phase silicon nitride and other solid solutions. Widespread application of advanced nitride ceramics is limited by high synthesis and processing costs. Combustion synthesis is an attractive method for overcoming this obstacle. Silicon-nitride-based ceramics are attractive for many high-technology applications because of their chemical inertness, high- temperature stability, fracture toughness and resistance to erosion, corrosion, and thermal shock.
