Ultrafine Microstructure Composites Prepared by Chemical Vapor Deposition
Abstract
This year we succeeded in preparing dispersed phase composite coatings which consist of a Boron nitride matrix containing Aluminum nitride. Chemical vapor deposition (CVD) offers an alternate avenue of preparing ceramic composites by simultaneous deposition of multiple phases (i.e., codeposition). The major advantage of preparing dispersed phase ceramic composites by CVD is that mechanical as well as chemical, electrical, optical, and thermal properties of the composites can be favorably tailored by controlling the composite composition and microstructure. Dispersed phase composites containing BN+ALN were deposited by CVD. The phases were either amorphous or crystalline depending on the deposition temperature and reagent concentration. One type of deposit which consisted of a turbostratic BN matrix containing oriented single crystal whiskers of ALN was very hard. A qualitative model based on statistical-mechanical nucleation theory and a hypothesized competition between growth of BN and ALN phases was successful in describing the relationship between operating conditions and the resulting microstructure of dispersed phase ceramic (BN+ALN) composites prepared by CVD. The present study has provided a fundamental basis for developing more quantitative models, which will integrate the underlying principles of thermodynamics, kinetics, transport phenomena, nucleation and crystal growth theory.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1988
- Accession Number
- ADA206061
Entities
People
- Andrew J. Green
- Douglas J. Twait
- Garth B. Freeman
- Geoving J. Gerard
- John A. Hanigofsky
- John R. Thompson
- Thomas S. Moss Iii
- W. J. Lackey
Organizations
- Georgia Tech Research Corporation