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 w ith a given amount of oxygen. The oxygen introduction within the PCS molecu lar structure makes the compact infusible during the pyrolysis step, and su pports 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 composi tions 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 al so shown that there are influences of the initial oxygen content on the res ulting microstructure of both as-pyrolyzed and heat-treated specimens.