Recent developments in combustion synthesis of nanosize silicon nitride and silicon carbide powders

Synthesis of ceramic and intermetallic materials in a self-sustaining regime has been explored for more than twenty years. The main drawbacks of this approach are lack of homogeneity and relatively wide particle size distribution of resulting products. Recently, a significant progress has been made to control both phase composition and particle size of combustion synthesized ceramic powders. It has been demonstrated that an addition of certain volatile compounds such as NH4HF2 NH4Cl, NH4F, KClO3, and Tenon, changes the overall mechanism of the reaction and leads to a formation of nanosize particles. Recently, both a-silicon nitride and silicon carbide with average particle size below 200 Mn were synthesized in a self-sustaining regime by nitridation of silicon at elevated nitrogen pressures and by a direct reaction between silicon and carbon at elevated argon pressure, respectively. Analyses of reaction conditions and product characterization are presented in detail. A formation of silicon nitride whiskers in a combustion regime is presented as well.