Preparation of Ultrafine SiC Powders by Pyrolysis of Tetramethyldisilane

Ultrafine silicon carbide powders of high purity have been prepared by pyrolysis of tetramethyldisilane at temperatures 700° to 1400°C. The diameter of the particles changed from 5 to 200nm depending on the pyrolysis conditions. The ultrafine particles consist of small crystallites of β-type SiC, arranged randomly in the particles. The molar ratio (C/Si) of the powders can be also controlled within the range 0.9 to 1.2 by pyrolysis conditions such as pyrolysic temperature and reactant concentration. No admixtures of carbon such as carbon soot or film on the SiC particles were observed with a high-resolution electronmicroscope even in the powders having (C/Si) ratio more than 1.0. The formation mechanism of the ultraf ine SiC powders is discussed in relation to the structure.