Synthesis of Si-C-O bulk ceramics with various chemical compositions from polycarbosilane

Si-C-O bulk ceramics with various atomic ratios were produced by pyrolysis and high-temperature treatment (HTT) of a polycarbosilane (PCS) precursor with a given amount of oxygen. The oxygen introduction within the PCS molecular structure makes the compact infusible during the pyrolysis step, and supports sintering, The derived chemical compositions are mapped on a Si-C-O constitution diagram, with their transition behaviors due to HTT described. Upon heating between 1500 degrees and 1700 degrees C, the chemical compositions of the as-pyrolyzed specimens were as follows: PCS-6 (SiC1.36O0.26), PCS-8 (SiC1.25O0.45), and PCS-10 (SiC1.02O0.68), moving toward C/Si = 1.2, 1.0, and 0.8 with a reduction of the oxygen content, respectively. It is also shown that there are influences of the initial oxygen content on the resulting microstructure of both as-pyrolyzed and heat-treated specimens.