Preparation of nanocrystal SiC powder by chemical vapour deposition

Nanosized silicon carbide powders of high purity and low oxygen content have been prepared by thermal chemical vapour deposition (CVD) of dimethyldichlorosilane at pyrolytic temperatures, 1100-1400 degrees C. The nanosized silicon carbide particles prepared at 1400 degrees C consist of small crystallites of beta-SiC arranged randomly in the particles. At pyrolytic temperature below 1300 degrees C, the particles consist of amorphous phase and beta-type SiC crystallites. The average particle size changed from 70 nm to 40 nm and the average size. of the beta-SiC crystallite changed from 7.3 nm to 1.8 nm depending on the pyrolysis conditions. The C/Si molar ratios of the product powders changed from 0.5 to 1.07 with the CVD conditions. The near theoretical values of C/Si molar ratio of the product powders within 0.95-1.05 can be controlled by CVD conditions such as pyrolytic temperature and reactant concentration. Finally, the product powders were characterized by chemical analysis, X-ray diffraction, electron microscopy, and infrared spectroscopy.