Synthesis and Sintering of Monolithic and Composite Ceramics under High Pressures and High Temperatures

This paper summarizes the research and developmental activities, carried out at the High Pressure\ud Laboratory, NAL, Bangalore, for the synthesis and sintering of ceramic materials (both monolithic and composites)under high pressures and high temperatures . A number of processing techniques namely, high pressure sintering (HPS), high pressure self-combustion synthesis (HPCS), high pressure reaction sintering (HPRS), reactive hot pressing (RHP), fabrication of ceramic-ceramic composites through intermediate soft phase processing (ISPP), reaction sintering of intermetallic matrix-ceramic composites were explored . These processing techniques were used effectively to fabricate sintered ceramic compacts with density - 99% of the theoretical density . In many of the cases, especially for the development of materials for the high temperature applications, no liquid phase forming additives were used. Extensive characterization of the sintered compacts was carried out to establish (i) the mechanisms of reaction and densification, (ii) microstructural evolution during synthesis, and (iii) microstructureproperty relationship .\u