SYNTHESIS OF SILICON-CARBIDE THROUGH THE SOL-GEL PROCESS FROM DIFFERENT PRECURSORS

Silicon carbide (SIC) was synthesised from silicon alkoxides and various carbon sources. Tetraethoxysilane (TEOS), methyltriethoxysilane (MTES) and a mixture of TEOS and MTES were hydrolysed in the presence of phenolic resin, ethylcellulose, polyacrylonitrile (PAN) and starch to incorporate the gel into the carbon source in the silica network. The gel thus obtained was carbonized at 800 degrees C in an argon atmosphere to obtain the mixture of silica and carbon which when heated to 1550 degrees C in argon yielded silicon carbide. The characterization of the product by X-ray, FTIR and SEM showed it to be beta SiC with different crystallite and grain sizes. The difference in the crystallite and grain sizes is attributed to the nature of the carbon source. The density of the SiC obtained by the sol-gel process was found to be lower than the values reported for SiC and this is ascribed to the porous nature of the products generally obtained by this process.