Abstract
SiC powder has been synthesized using CO2 laser-heated vapor phase reactions in the silane-methane gas system. SiC particles form via a two-step reaction: silicon particle formation and subsequent carburization of the silicon particles. It is shown that the silicon particles form at the lower edge of the reaction zone, and carburization occurs in the hottest region, through which the CO2 laser beam passes. The formation of silicon particles can be explained by silane pyrolysis and subsequent collisions and coagulation of the silicon particles. The carburization mechanism of the silicon particles is discussed in terms of diffusion through a SiC product layer and methane pyrolysis. The rate-controlling step is believed to depend on the reaction conditions such as temperature and gas stoichiometry.
