SiC matrix composites containing transition metal boride particulates internally synthesised by carbothermal reaction

Abstract

SiC matrix composites reinforced with the various borides of the transition metals in group IV a-VI a, which were synthesized from the transition metal oxide, boron carbide and carbon mixed with SiC powder. Dense composites containing boride particulates of titanium, zirconium, niobium and chromium were prepared through reactive hot-pressing. The morphology of the internally synthesized boride particles reflected that of the starting oxide powders. SiC-NbB2 composites with four-point flexural strength of 500 to 600 MPa and better oxidation resistance than SiC-TiB2 were prepared even through pressureless sintering process. Pressureless-sintered and HIPed SiC-20 vol% NbB2 exhibited the four-point flexural strength of 760 MPa at 20 °C and 820 MPa at 1400 °C.