Effect of gas flow rate on ultrafine SiC powders synthesized through chemical vapor deposition in the SiH 4-C 2H 4-H 2 system

Abstract

The renewed interest in the study of nanometer-scale materials has triggered intensive research on the synthesis of powders with improved properties. The characteristics of the starting powder are of paramount importance in the control of sintered microstructure and the resultant physical properties of the bulk body. Powders suitable for subsequent forming and consolidation should possess the following features: small size with a narrow size distribution, equiaxed morphology, highly pure chemical composition, single phase and nonagglomerated state. SiC ceramic is an important structural as well as functional material because of its strength, hardness, resistance to chemical corrosion, high thermal conductivity and good electrical insulation. SiC powders with desired particle size and composition can be synthesized by a direct gas phase reaction process which offers many technological advantages over other formation methods in terms of small particle size, narrow size distribution, relatively pure chemical composition as well as good reproducibility. Though the roles of other parameters have been well documented and widely accepted by many investigators, the effect of gas flow rate still remains to be clarified. In his work, Yang concluded that the size of powders changes as a parabolic function of gas flow rate, while the morphology and composition ofmore » the powders are almost unaffected. However, present results indicate that both the size and morphology of the SiC powders obtained can be altered by modifying the gas flow rate, for which the underlying mechanisms have been explored.« less