A MODEL FOR THE FORMATION OF NANOSIZED SIC POWDERS BY LASER-INDUCED GAS-PHASE REACTION

Powder refinement is one approach to reducing the frequency of microst ructural inhomogeneities in ceramic parts. Laser-induced pyrolysis of gaseous precursors is a reproducible and reliable process to fabricate nanosized particles. In the thermal decomposition of SiH4 and C2H2 by a continuous wave CO2 laser, the size of the silicon carbide particle s is adjusted according to their residence time in the reaction zone. The collision and coalescence model provides a satisfactory agreement with experimental results, whereas the nucleation theory is inappropri ate, due to the small dimensions of the critical nuclei.