Synthesis of Nonoxide Ceramic Powders By Nonthermal Microwave Plasma.

摘要

We report the synthesis of nonoxide ceramic powders of aluminum nitride, silicon carbide and silicon nitride by nonthermal microwave plasma of precursor gases under conditions of laminar flow. The precursor gases used were trimethylaluminum and nitrogen for aluminum nitride, silane and acetylene for silicon carbide, and silane and nitrogen for silicon nitride. The argon gas was used as the diluent/carrier gas in all the cases. The effect of flow rate of the gases and hence the effect of concentration and residence time of the activated species in the plasma is discussed. The microwave energy in the plasma was (50-100) Watts. The product particles were characterized by transmission electron microscopy, Auger electron spectroscopy and X-ray photoelectron spectroscopy. The synthesized material was found to be ultrafine (approximately 5nm) and crystalline. Aluminum nitride stabilized in either hexagonal or cubic phases depending on the nitrogen concentration. The silicon carbide formed was mostly cubic-3C accompanied with several hexagonal and rhombohedral polytypic modifications. The implications of the occurrence of polytypes in particles of nanometer size are discussed in terms of the existing theories. The silicon nitride was formed in the alpha phase modification.