Ultrafine Microstructure Composites Prepared by Chemical Vapor Deposition

It is our goal to develop an analytical model which predicts the experimental conditions which permit the preparation of ultrafine microstructure ceramic composites by chemical vapor deposition (CVD). The model is to be based on classical thermodynamics, mass transport, kinetic, nucleation, and growth theory. The model will be validated for two dispersed phase composite systems. One system will be boron nitride plus aluminum nitride. The other will be hafnium diboride plus silicon carbide. The BN + AlN system is of interest for radomes, windows, and tribological applications while HfB2 + SiC offers potential as a high temperature oxidation resistant material including oxidation protective coatings for carbon-carbon composites. Thermodynamic analyses of the BN + AlN and the HfB2 + SiC systems have been completed. These computerized studies indicate that both composite systems can be prepared by codeposition using commercially available, conventional reagents.