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 Cf/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.

Graphical abstractThis is the 29Si MAS NMR of the cured PMS and cured A-PMS. Cured A-PMS is made of highly crosslinked structure SiC4, while cured PMS is made of Si–Si structure. This indicating that SbCl3 promoted the transformation of Si–Si to Si–C.Figure optionsDownload full-size imageDownload as PowerPoint slide