Synthesis and Characterization of Silicon Oxycarbide Glasses

It has been found that X‐ray amorphous silica glasses containing up to 18% carbon can be synthesized using a sol/gel process. In this study, the sols were prepared using four different organometallic precursors—methyl‐, ethyl‐, propyl‐, and phenyltrimethoxysilanes. ¹H NMR,¹³C NMR, and TGA revealed that the methoxy groups are hydrolyzed in the solutions and, therefore, are absent in the gels. But the alkyl groups are retained in the dry gels. The ²⁹Si NMR data verified that the Si—C bonds associated with these alkyl groups are intact in the dry gels. Most importantly, however, Si—C bonds are found in the glasses obtained after heat‐treating the gels at high temperature in an inert atmosphere; i.e., the synthesis does, in fact, create an oxycarbide network structure. TGA showed that the dense oxycarbide glasses are stable to 1000°C in argon and in air.