Phase composition and morphology of TaC coating on carbon fibers by chemical vapor infiltration

Abstract Chemical vapor infiltration was applied to deposit TaC thin film on carbon fibers using TaCl 5 –Ar–C 3 H 6 –H 2 source. The influence of temperature, pressure and addition of H 2 on phase composition and morphology of the coating had been studied. The results showed that the composition of the coating changes with temperature. The films are mainly composed of TaC and C when deposited at 800–900 °C and C phase disappears at 950 °C and 1000 °C. TaC grains are very small at 800 °C and get bigger at 900 °C; while at 1000 °C, a dense coating has developed. The influence of pressure on coating composition is much weaker when deposited at 850 °C and the films are consisted of TaC and C phases at 0.6–8.0 kPa; TaC grains formed at 0.6 kPa are smaller and more homogeneous than those obtained at 8.0 kPa. With 100 ml/min H 2 flow, the coating composition changes and turns into a mixture of TaC and Ta 2 C with fine and homogeneous grains at 850 °C and coarse grains at 950 °C.