SYNTHESIS AND CHARACTERIZATION OF ULTRAFINE POWDERS OF SIC-SI3N4

Nanometer size SiC-Si3N4 composite powders have been synthesized by th e chemical vapor phase reaction method. Reaction conditions such as NH 3/SiH4(mol), C2H4/SiH4(mol), cell pressure, gas flow rate and reaction temperature have significant effects on the composition, size, shape and crystallinity of the resulting particles. The particle sizes of Si C-Si3N4 powders are in the range 8.9 nm to 26 nm depending on the reac tion conditions. The particles increase in size with increasing cell p ressure, C2H4/SiH4(mol) and NH3/SiH4(mol) and decreasing gas flow rate . The composite powders are primarily composed of beta SiC, alpha-Si3N 4 and free Si crystallites. The surface and the interface of the parti cles are amorphous.