In-Situ Fabrication of Ceramic Matrix Composites by RH-SHS Technique

A rapid heating self propagating high temperature synthe-sis (RII-SHS) technique is developed for the fabrication of in-situ A1203 -SiC„ composites. The adiabatic tempera-ture for the system is calculated to be 2375 K. The green compacts are heated rapidly (w 300 - 400 K/min) from room temperature to various soaking temperatures (T,) ranging from 1473 to 2023 K either in air or argon atmosphere.
Two exothermic reactions are observed successively during synthesis. XRD analyses show that the reduction of SiO2 proceeds through aluminothermic route and a holding time of = 30 minutes at T, is sufficient for the completion of reactions. SiC is observed to be present in the form of a-Sic, and the size and proportion of the whiskers depends upon the soaking time and temperature. Dimensional stabi-lity of the sintered products indicates the possibility of near net shape fabrication of composites using this technique.