On the pyrolysis of a methyl‐silsesquioxane in reactive CO <sub>2</sub> atmosphere: A TG/MS and FT‐IR study
R. Campostrini, Andrea Zambotti, Mattia Biesuz, Gian Domenico Sorarù
Abstract
Abstract Polymer‐derived SiOC‐C composites are typically obtained through pyrolysis of a polysiloxane precursor in inert atmosphere. Recent studies have shown that novel SiOC microstructures and compositions can be obtained when the pyrolysis is carried out in a reactive environment, as CO 2 , which leads to a selective oxidation of the Si─C bonds leaving a microstructure constituted by a nano‐dispersed sp 2 carbon phase within an SiO 2 matrix. However, little is known about the reaction mechanisms between CO 2 and the preceramic polymer to date. In this work, we investigated the pyrolysis of a methyl‐silsesquioxane in reactive (CO 2 ) and inert (Ar or He) atmosphere by combining TG/MS and FT‐IR analysis. The results showed that CO 2 starts to react with the preceramic polymer from ≈750°C when the Si─CH 3 groups start to form Si─CH x ‐Si units. The reaction breaks the Si─C bond increasing the amount of the free carbon phase and releasing water vapor, detected by MS, even at temperatures exceeding 900°C. At higher temperatures (≈950°C), CO 2 reacts with the free carbon phase leading to a weight loss and the formation of CO.