Silicon oxycarbide glasses from silicone networks

Rubbers resulting from the hydrosilylation reaction between poly(methylsiloxane), and 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcycletetrasiloxane, have been pyrolyzed to silicon oxycarbide ceramics, with ceramic yield varying as a function of the mixture composition. The rubber-ceramic conversion process was investigated by C-13 and Si-29 nuclear magnetic resonance and infrared spectroscopies, thermogravimetric analysis and density measurements. The composition of the ceramic products was determined by elemental and X-ray fluorescence analyses and their structural characterization was done by Si-29 solid-state magic angle spinning nuclear magnetic resonance. The structure of the ceramic products is, actually, a mixture of SiO4, SiCO3, SiC2O2, SiC3O, SiC4 sites randomly distributed in the bulk. The C-C/SiCxO4-x composites were prepared by infiltration of the siloxane mixture into the bidirectionally reinforced carbon plate. The composites obtained after pyrolysis showed an improved resistance to oxidation in relation to untreated carbon plates. (C) 1999 Elsevier Science B.V. All rights reserved.