Oxidation process of white Si–O–C(–H) ceramics with various hydrogen contents

Si–O–C(–H) ceramics with various carbon-to-hydrogen ratios were prepared by pyrolyzing a polysiloxane precursor in hydrogen at 800–1100 °C. The chemical compositions were SiO1.68C0.48H1.66 (800 °C), SiO1.54C0.26H0.25 (900 °C), SiO1.54C0.26H0.18 (1000 °C) and SiO1.54C0.26H0.12 (1100 °C). The oxidation process of individual Si–O–C(–H) was investigated by thermogravimetric/mass spectrometry. Ceramics with high H/C ratios exhibited sudden weight gains at 400–600 °C, which were accompanied by CO2–H2O evolution. Ceramics with low H/C ratios, oxidation and CO2 evolution proceeded moderately beyond 800 °C.