溶胶凝胶法制备碳化硅陶瓷的影响因素

The Effects of the Preparation of SiC by Sol-Gel

采用溶胶凝胶法 ,以正硅酸乙酯和酚醛树脂为原料 ,在草酸催化作用下 ,制备出了不含硫和氯的均相碳化硅先驱体 ,并在一定的升温制度下制备出SiC陶瓷。考察了温度对预水解过程的影响以及水用量、催化剂和镍盐用量等因素对凝胶时间的影响。结果表明 ,在预水解温度控制在 4 0℃左右 ,时间为 2 4h时效果最佳 ;而当水与正硅酸乙酯的摩尔比达到 0 2 8左右、草酸与正硅酸乙酯的摩尔比为 0 0 1左右时 ,可以使凝胶时间达到最短。进一步的研究表明 ,镍盐的加入对凝胶烧成过程中 β -SiC的生成有催化作用。

A sol gel process catalyzed by oxalic acid is adopted to prepare SiC precursors from the raw materials of tetrathoxysilane(TEOS) and phenolic resin, and this precursors is homogeneous without the impurity of sulfur and chlorine. Sintered with a certain heating program, the obtained precursor is converted into SiC. The effect of the temperature on the hydrolyze and the influences of the amount of water, catalyzer, Nickel nitrate on the gel time are studied.The result shows that the sol gel process is best at 40℃ and exactly after 24 hr. While the ratio of H 2O:TEOS(mol) is 0 28 and oxalic acid:TEOS(mol) is 0 01, the gel time is shortest. The further study indicates that β SiC is converted when the catalyzer of the nickel nitrate is mixed in.