超支化聚碳硅烷的掺硼改性与陶瓷化研究

Modification of a hyperbranched polycarbosilane with boron and its polymer-to-ceramic conversion

通过二甲基胺硼烷(DMAB)与烯丙基超支化聚碳硅烷(AHPCS)反应合成含硼聚碳硅烷先驱体,后经170℃热交联及高温裂解制备出碳化硅陶瓷。采用傅立叶红外光谱、热重分析、X射线衍射分析及扫描电子显微镜对上述过程进行研究。结果表明,DMAB中的B—H键可分别与AHPCS中的CC键及Si—H键发生硼氢化反应和脱氢偶合反应,从而促进AHPCS的热交联,并显著提高陶瓷产率。此外,硼的引入还可有效抑制β-SiC在高温下的结晶。

A boron-modified AHPCS was prepared by chemical reactions between allylhydridopolycarbosilane （AHPCS） with dimethylamine borane （DMAB）, and then cross-linking at 170 ℃, followed by pyrolyzing at high temperatures to afford SiC-based ceramics. The cross-linking and polymer-to-ceramic conversion of the bo- ron-modified AHPCS were characterized by FT-IR, TGA, XRD and SEM. The results indicate that the cross- linking of AHPCS was improved, involving hydroboration reaction between vinyl groups of AHPCS and B H groups of DMAB, and dehydrocoupling reaction between Si H groups of AHPCS and B--H groups of DMAB. As a result, the ceramic yield of the B-modified AHPCS was significantly enhanced. Moreover, the introduction of boron inhibits the crystallization of β-SiC at high temperatures obviously.