溶胶凝胶法制备碳化硅陶瓷及其影响因素

The Preparation of SiC by Sol-Gel and its Influencing Factors

采用溶胶凝胶法 ,以正硅酸乙酯和酚醛树脂为原料 ,在草酸的催化作用下 ,制备出了不含硫和氯等有害杂质的均相碳化硅先驱体 ,并在特定条件下 ,对所得先驱体进行烧结 ,使之转化为陶瓷 .结果表明 ,预水解温度控制在4 0℃左右 ,时间为 2 4h时 ,凝胶制备效果最佳 ;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 ;溶胶凝胶法制得的先驱体呈黄色透明的玻璃态 ,其微观组成为几十纳米的微粒 ,树脂与SiO2 可能通过氢键相互作用 ,有利于树脂在先驱体中均匀分布而形成均相先驱体 ;另外硝酸镍的加入对先驱体烧结过程中 β SiC的生成起到促进作用 .

A sol gel process catalyzed by oxalic acid was adopted to prepare silicon carbide precursor which has no impurity of sulfur and chlorine from the raw materials of tetrathoxysilane (TEOS) and phenolic resin. Sintered with certain heating program, the obtained precursor is converted to SiC. At the same time, the effect of the temperature on the hydrolysis and the influences of catalyzer and nickel nitrate on the gel time were studied. One found that the sol gel process reached the best at 40 ℃ and 24 h . While the molar ratio of oxalic acid and TEOS is 0.01, the gel time reached the shortest. SEM spectrum shows that the precursor is composed of homogeneous vitreous and fine nano particles. Phenolic resin silca and phenolic resin might interact through hydrogen bonding, which is propitious to synthesize homogeneous precursor. Further studying indicated that crystal of β SiC is converted when the catalyzer of the nickel nitrate is mixed in.