Silicon oxycarbide glasses from silicone networks

Rubbers resulting from the hydrosilylation reaction between poly(methylsilo xane), and 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcycletetrasiloxane, have b een pyrolyzed to silicon oxycarbide ceramics, with ceramic yield varying as a function of the mixture composition. The rubber-ceramic conversion proce ss was investigated by C-13 and Si-29 nuclear magnetic resonance and infrar ed 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 structu re 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 compos ites were prepared by infiltration of the siloxane mixture into the bidirec tionally reinforced carbon plate. The composites obtained after pyrolysis s howed an improved resistance to oxidation in relation to untreated carbon p lates. (C) 1999 Elsevier Science B.V. All rights reserved.