Structural characterization of polysiloxane-derived phases produced during heat treatment

Silicon carbide (SiC) a wide-gap semiconductor, with extreme hardness is expected to offer some technological advantages, such as high chemical and mechanical stabilities. SiC with amorphous, nanocrystalline or crystalline microstructure is obtained when preceramic polymers are pyrolysed in an inert atmosphere. Properties of these materials depend on the amount and kind of elements present in residue product, amount of carbon directly bonded to silicon and free carbon or silica behaving as neutral part of the material. This article deals with thermal treatment of the cured polymethylphenylsiloxane and its transformation into silicon oxycarbides and into SiC. Morphology, microstructure and structure of the ceramic phases were characterized by X-ray diffraction (XRD), scanning electron microscopy, FTIR method and Raman scattering. The study indicated that the ceramic materials derived from heat-treated polysiloxane resin at 1700 8C consist of crystalline and amorphous SiC, turbostratic carbon and free silica. Raman and FTIR spectroscopies are useful tools to study new materials consisting of nano- or/and amorphous-phases and give more precise information as compared to XRD. q 2004 Elsevier B.V. All rights reserved.