Influence of Deposition Temperature and Heat Treatment on Silicon Nitride Coat ing Deposited by LPCVD

Silicon nitride coatings on carbon fiber cloth were prepared by Low Pressure Chemical Vapor Deposition (LPCVD) from gas mixtures of SiCl 4 -NH 3 -H 2 at temperatures ranging from 750 to 1250 . The effects of deposition temperature on the growth kinetics, morphologies, chemical composition and bonding state of the coatings were investigated. The results showed that deposition rate increased monotonously with temperature up to 1050 , then it reversely decreased. In the whole temperature range, the coating surface morphology became gradually coarse with cauliflower-like grains as the deposition temperature increased. The optimal deposition temperature for infiltration was in the range between 750 and 950 . Chemical composition analysis demonstrated that the nitrogen content of the coating firstly decreased and then increased with temperature increase, while the silicon content continuously increased and the oxygen content gradually decreased in the whole temperature range.