Structural Formation and Mechanism in Combustion Synthesis of Nitrogen Ceramics (AIN, Si_3N_4 and AIN-SiC)

摘要

Structure and phase formation mechanisms were investigated for gaseous nitrogen react with solid reactants in combustion mode. Various systems including Al-N, Si-N and Al-Si-C-N are discussed. Thermokinetic analysis indicated that vapor-crystal mechanism play dominate role in both systems when the initial particle size is small, while, surface nitridation of Si particles followed by the spallation of nitride layer in Si-N systems accounts for the combustion mechanism when coarse Si particles (>20μm) are used as reactants. In regarding to the Al-N combustion reaction, characteristic eggshell-type structure formed via an explosive fracturing of reacting powder caused by the Al vapor pressure that developed inside the AlN crust. Besides, for the Si-N combustion reaction in large samples, evidence for the formation of Si_3N_4 via the reaction of liquid Si with nitrogen was also observed.