Deposition characteristics of titanium coating deposited on SiC fiber by cold-wall chemical vapor deposition

The deposition characteristics of titanium coating on SiC fiber using TiCl4-H2-Ar gas mixture in a cold-wall chemical vapor deposition were studied by the combination of thermodynamic analysis and experimental studies. The thermodynamic analysis of the reactions in the TiCl4-H2-Ar system indicates that TiCl4 transforms to titanium as the following paths: TiCl4 → TiCl3 → Ti, or TiCl4 → TiCl3 → TiCl2 → Ti. The experimental results show that typical deposited coating contains two distinct layers: a TiC reaction layer close to SiC fiber and titanium coating which has an atomic percentage of titanium more than 70% and that of carbon lower than 30%. The results illustrate that a carbon diffusion barrier coating needs to be deposited if pure titanium is to be prepared. The deposition rate increases with the increase of temperature, but higher temperature has a negative effect on the surface uniformity of titanium coating. In addition, appropriate argon gas flow rate has a positive effect on smoothing the surface morphology of the coating.