Growth of Diamond Film By CVD on Near Net Shape Fabricated β-SiC/TiC Composites Synthesized Using SHS

Abstract

ABSTRACTβ-SiC/TiC composites were synthesized using the process of self propagating-high temperature combustion synthesis (SHS). The heat released during the exothermic reaction between Si and C powders (with a δH of -14kcal/mole) and that Ti and C powders (with a δH of -44.1 kcal/mole) is sufficient to cause the melting of the powders into which the carbon diffuses and from which β-SiC and TiC precipitate out of the supersaturated solution. The composite was characterized using X-ray diffraction techniques, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy. An attempt was made to understand the mechanism of formation of the composite. We have proposed a mechanism to understand the formation of the SHS compounds based on dissolution, diffusion and precipitation from the supersaturated solution. There is no evidence for the presence of TiSi2 and an attempt was made to explain this observation based on free energy considerations. Diamond film was then grown on the pellet by hot filament CVD technique using methane and hydrogen gas as the reactants. The deposition was conducted for a period of four hours. A continuous film of diamond was found to grow on β-SiC/TiC composite using this technique. The diamond film was characterized by using Raman spectroscopy and SEM. The diamond film showed both (001) and (11) facets with average grain size of 5 μm.