Nitridation of whisker-reinforced reaction bonded silicon nitride ceramics

Ceramic matrix composites were fabricated from silicon carbide whisker-reinforced reaction bonded silicon nitride. Optimal dispersion of the SiC whiskers in the silicon powder slip was achieved by milling and pH control; a pH range of 4–5 giving the best results. Only a slight drop in green density was observed for a 30 wt% addition of SiC whiskers. The effects of the whisker additions on the nitridation kinetics of reaction bonding were investigated and the additions were found to increase the induction period before nitridation and to slightly decrease the nitridation rate but green density and temperature were still found to be the main factors controlling nitridation. Modulus of Rupture measurements for the composites showed a decrease in strength compared to the monolithic material.