Effect of solvent in preparation of SiOC bulk ceramics

Silicon oxycarbide (SiOC) is an important polymer derived ceramic with many unique properties such as high temperature stability and amorphous-nanocrystalline mixed structures. It can be made using different processing routes. In this study, SiOC ceramics were investigated using a polysiloxane precursor crosslinked in the presence of 0, 100, 200, and 300 vol% of 3-pentanone as the solvent. The microstructure and the phase evolution during pyrolysis depend on the solvent concentration during crosslinking. The addition of pentanone facilitates the formation of nanocrystalline SiC at pyrolysis temperatures <= 1300 degrees C. However, the formation of SiC decreases with increasing solvent content when pyrolyzed at 1400 degrees C. Simply varying the solvent concentration during crosslinking provides a unique and tunable processing route for modifying the phase formation within SiOC ceramics.