Effects of promoters on the product quality of nanophase SiC/alpha-Si3N4 composite powders synthesized through carbothermal reduction nitridation

The effect of additives is investigated for the carbothermal reduction synt hesis of nanophase silicon carbide/silicon nitride composite powders. Mixtu res of silica, carbon, seed silicon nitride, and additive are reacted in a thermogravimetric analyzer. The mass loss information combined with composi tional and spectroscopic analysis allows product quality (morphology, surfa ce area, alpha -Si3N4 and beta -SiC contents, oxygen content, etc.) informa tion to be obtained. It was observed that all of the additives used in this study increased the reaction rate. Lithium carbonate produced a silicon ni tride/silicon carbide composite that was not significantly different from e xperiments without promoter. However, the product quality was severely affe cted in other instances. (C) 2001 Kluwer Academic Publishers.