Preparation of Dispersed Phase Ceramic Boron Nitride and Aluminum Nitride Composite Coatings by Chemical Vapor Deposition

Dispersed phase ceramic composite coatings containing BN and AIN were prepared by chemical vapor deposition. The BN + AIN coatings were deposited on Al₂O₃ from the BCI₃–AICI₃-NH₃ reagent system in the temperature range of 700° to 1200°C. Also, single-phase BN and AIN coatings were prepared for comparison purposes. The composite coatings consisted of very small BN and AIN regions which were either crystalline or amorphous, depending on deposition temperature and reagent concentrations. For example, a composite containing AlN whiskers of less than 100-nm diameter in a matrix of turbostratic BN of 2-nm grain size was deposited at 1100°C and 20 kPa.