CVD synthesis of nanometer SiC coating on diamond particles

Poor interfacial bonding between diamond and matrices has limited industrial applications of diamond-containing composites. Herein, continuous and dense nanometer SiC coatings were deposited on both large size (200 μm) and small size (1.0 μm) diamond particles to improve the wettability of diamond and protect it from oxidation and graphitization. Coating procedure consisted of first pretreating diamond particles followed by chemical vapor deposition (CVD) using methyltrichlorosilane (MTS: CH₃SiCl₃) as a precursor. Effects of deposition temperature, time, and gas flowing rate on microstructures of SiC coatings were all studied. Results showed that diamond surfaces were fully coated by SiC with thicknesses of 30 nm and 20 nm for large and small size diamond particles, respectively. Meanwhile, onset oxidation temperatures of large and small SiC-coated diamond particles increased by 250 and 130 °C, showing greatly enhanced oxidation resistance than that of raw diamond particles. The compressive fracture strength (CFS) of SiC-coated diamond (200 μm) is 226 N, improved by 8.5% compared with that of the raw diamond (201 N). In sum, CVD method is promising for the preparation of homogeneous nanometer SiC coatings on diamond particles for its modification and further application in composites.