Nano-SiC implantation into the structure of carbon/graphite materials made by pyrolysis (carbonization) of the precursor system coal tar pitch/poly(dimethylsiloxane)

Conversion of the air-cured poly(dimethylsiloxane) {-O-Si(CH3)(2)-}(n) to SiC during co-pyrolysis with a coal tar pitch is studied with reference to the related SiO2/pitch system. Each binary mixture is first homogenized at 160 degreesC followed by carbonization at 500 degreesC under argon to afford initial carbonizates. In both cases, one part of the initial carbonizate is further pyrolyzed at 1300 degreesC and another part at 1650 degreesC under an argon flow resulting in composite products. All products are studied with FT-IR, XRD, and XPS spectroscopic methods supplemented with SEM and 'wet' Si-analyses, when applicable. Carbothermally assisted conversion of both silicon precursors to nanocrystalline SiC embedded in the evolving C-matrix, i.e. nano-SiC/C composites, is evident only after the 1650 degreesC carbonization stage. (C) 2003 Elsevier Ltd. All rights reserved.