Preparation of Silicon Carbide Coatings from Liquid Carbosilanes by Chemical Vapor Deposition

Liquid carbosilanes which were synthesized from polydimethylsilane (PDMS) were analyzed by infrared spectra (IR) and H-nuclear magnetic resonance (NMR). Silicon carbide coatings were prepared by chemical vapor deposition from liquid carbosilanes onto several different substrates. The coatings were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD), and IR. The results show that liquid carbosilanes are mixtures of several oligomers which have Si-C backbone. The coatings prepared at 850 °C contain some organic segments, and those prepared at 900 °C are comparatively pure SiC which is partly crystallized. The coatings are glazed and very hard.