Effect of pyrolysis atmosphere on the microstructure of polymer-derived SiOC monolithic ceramics

Different pyrolysis atmospheres can influence the evaporative species removal and thus pyrolyzed ceramic compositions and microstructures. In this study, the polymer-to-ceramic conversion of a SiOC precursor under Ar and water vapor pre-pyrolysis as well as further Ar and vacuum pyrolysis was investigated. The pyrolysis behaviors were characterized by TGA/DTG measurements coupled with in-situ evolved gas analysis, SEM/EDS, and BET. The results demonstrate that pre-pyrolysis with water vapor plus pyrolysis with vacuum results in more mass loss and formation of pores. The accompanying mechanisms of carbon oxidation and gas evolution are discussed in detail. This work provides a fundamental understanding of SiOC pyrolysis behaviors under different environmental conditions.