Synthesis of SiC/SiO2 core-shell powder by rotary chemical vapor deposition and its consolidation by spark plasma sintering

SiC (core) and SiO2 (shell) powders were synthesized via rotary chemical vapor deposition (RCVD). The SiC particles (3C, <1 μm in diameter) were coated with a layer of SiO2 (10-15 nm in thickness). Using spark plasma sintering, the SiC/SiO2 nanopowders were then synthesized into SiC/SiO2 composite bodies. Although a phase transformation from 3C to 6H was observed at above 2123 K in the sintered monolithic SiC bodies, sintered SiC/SiO2 bodies did not display such phase transformation. In addition, SiC/SiO2 bodies did not exhibited grain growth until the sintering temperature reached 2223 K. The density and Vickers hardness of the sintered SiC/SiO2 bodies increased with increasing sintering temperature. The highest density and hardness of SiC/SiO2 composite bodies were 98.1% and 24.4 GPa at 2223 K, respectively, which were higher than the corresponding values of 90% and 14 GPa for monolithic SiC bodies.