A modified polymethylsilane as the precursor for ceramic matrix composites

A novel SiC precursor, A-PMS, was synthesized through a reaction of polymethylsilane (PMS) with SbCl₃, where the Si-H in PMS reacts with Sb-Cl to form Si-Sb bond with HCl evaporated. A-PMS was used as a precursor to prepare C_f/SiC ceramic matrix composites (CMCs) via polymer infiltration and pyrolysis (PIP) process. It is evident that SbCl₃ plays a very important role in promoting chain crosslinking, transforming of the Si-Si into Si-C bonds and stabilizing PMS from very high oxidation trend of the active Si-H bonds. A-PMS keeps liquid at room temperature that is suitable for the infiltration in the absence of any solvent. A-PMS can be cured into a fully crosslinked structure at 320 °C that leads to a very high ceramic yield up to 91% and an Si/C ratio near 1.12 after pyrolysis. The resulted CMCs samples reached a density of 1.76 g cm⁻³ and a flexural strength of 381 MPa after only four infiltration-pyrolysis cycles.     

Synthesis and pyrolysis of oligo(methylsilylene)-ethynylene polymer to near-stoichiometric SiC ceramic

<正>Oligo(methylsilylene)-ethynylene polymer with crosslinkable ethynyl unit in the main chain was synthesized by condensation ofα,ω-dicholorooligo(methylsilane) with dilithioacetylene.The as-synthesized polymer was characterized by GPC,FT-IR and NMR.The results showed ethynyl group was successfully introduced to the polymer main chain.The ceramic yield was dramatically increased by the cross-polymerization of ethynyl group,and the excess silicon of PMS was compensated.Nearstoichiometric (C/Si=1.17) and partial crystallizationβ-SiC monoliths were obtained by pressureless pyrolysing PSPA at 1200℃in a high yield(73.6 wt%).     

三甲基硅基取代聚硅烷的合成与性能研究

利用聚甲基硅烷(PMS)的高分子反应合成三甲基硅基取代聚硅烷(SPS),研究其分子组成与结构,热分解性能和导电性能等.FT-IR、1H-NMR、29Si-NMR、UV和GPC分析表明,SPS具有Si—Si相连的主链结构,侧链的部分取代基中含有三甲基硅侧基.SPS可溶于一般常见的有机溶剂,其热分解特性表明,陶瓷产率为44%,可用作SiC陶瓷先驱体.通过热交联反应可以有效提高其分子量,将其与碘掺杂,电导率为10-6S/cm量级,在半导体范围.     

聚甲基硅烷的合成与封端

利用Wurtz反应合成聚甲基硅烷 ,研究两类溶剂对其组成、分子结构和分子量的影响 .FT IR和1 H NMR及2 9Si NMR分析表明 ,以甲苯为溶剂 ,可以避免在溶剂化过程中Kumada重排的发生 ;而以THF 正己烷 (1∶6 ,V V)为溶剂 ,聚甲基硅烷容易支化和形成Si—CH2 —Si结构 .研究发现 ,聚甲基硅烷具有复杂的端基结构 ,封端剂的加入量影响着最终合成聚甲基硅烷的质量 .