Gel Precursor to Silicon Oxycarbide Glasses with Ultrahigh Ceramic Yield

This paper reports on the synthesis and the pyrolysis transformation of a sol–gel precursor to an oxycarbide glass with an extremely high ceramic yield (up to 97 wt%). This unusually high ceramic yield is achieved by adding a small amount of boron alkoxide to a precursor gel containing Si—H and Si—CH 3 functionalities. The role of boron in the pyrolysis process is investigated using various spectroscopic techniques and by analyzing the pyrolysis gases with a mass spectrometer. The experimental results suggest a catalytic effect of the boron atom in promoting a partial oxidation of the Si—H bonds to Si—O bonds, with a corresponding reduction of the weight losses that are associated with the evolution of silanes during pyrolysis. Chemical analysis and XRD investigation indicate that the presence of boron does not modify the formation of the expected oxycarbide network.