Structure of silicon oxycarbide glasses derived from poly(methylsiloxane) and poly[methyl(phenyl)siloxane] precursors

The preparation of silicon oxycarbide glasses and structure changes of polysiloxane precursors during heat-treatment in oxidative and nitrogen atmosphere are studied by C-13 and Si-29 magic angle spinning (MAS) NMR, Fourier-transform infrared (FTIR) spectroscopy and thermogravimetry analysis (TG). The reaction mechanisms in inert and oxidation conditions are discussed with respect to the chemical composition of the used precursors. We focused on the formation of new silicon oxycarbide units as well as a highly condensed aromatic carbon phase, the structure of which is discussed. A correlation of thermo-oxidative properties with chemical structure of prepared materials as well as with conditions of their preparation is given. (C) 2001 Elsevier Science B.V. All rights reserved.