Preparation of pyrocarbon coatings on SiC_F

Pyrocarbons were deposited on SiC fibers from the gaseous mixture of C₃H₆ and N₂ at temperatures range from 800°C to 1200°C. The variations of deposition rate and surface morphology along with the changes of temperature, total pressure and P_N2/P_C3H6 have been studied. The results show that pyrocarbons could hardly be obtained under the condition where the temperature and total pressure were below 800°C and 1 kPa, respectively. Deposition rate increases and the morphology of pyrocarbons alters from uniform depositions to uneven ones with the increasing of the temperature and total pressure. Low ratio of P_N2/P_C3H6 leads to pyrocarbon granulation products. Compact as well as even pyrocarbons were obtained when deposition temperature was 1000°C, total pressure 10 kPa and P_N2/P_C3H6 2:1 approximately. The changes of processing parameters could result in the changes of reaction thermodynamics and kinetics, which in turn is the main reason for the changes of the surface morphology.