Synthesis of sinterable SiC powders by carbothermic reduction of gel-derived precursors; and pyrolysis of polycarbosilane

Abstract

Silicon carbide powders were synthesized by 1) carbothermic reduction of carbon-doped silica gel derived from colloidal silica or methyltrimethoxysilane and 2) pyrolysis of polymeric SiC precursors. Powder characteristics, including sinterability, depended on the type and composition of the precursor. The colloidal silica-sucrose and -pitch SiC powders doped with boron and carbon were sintered to 95% to 96% of theoretical density at 2100C in argon. The microstructures of these sintered SiC bodies consisted of mixtures of elongated grains (up to 50 m) and equiaxed grains (approx. = 10 m) with residual pores (up to 8 m) at grain boundaries or inside grains. 12 references, 7 figures, 2 tables.