Chapter 14. Fugitive Interface Coating in Oxide-Oxide Composites: A Viability Study
- John B. Wachtman Jr
Published Online: 26 MAR 2008
Copyright © 1991 The American Ceramic Society, Inc.
Proceedings of the 15th Annual Conference on Composites and Advanced Ceramic Materials, Part 2 of 2: Ceramic Engineering and Science Proceedings, Volume 12, Issue 9/10
How to Cite
Mah, T., Keller, K., Parthasarathy, T. A. and Guth, J. (1991) Fugitive Interface Coating in Oxide-Oxide Composites: A Viability Study, in Proceedings of the 15th Annual Conference on Composites and Advanced Ceramic Materials, Part 2 of 2: Ceramic Engineering and Science Proceedings, Volume 12, Issue 9/10 (ed J. B. Wachtman), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470313848.ch14
- Published Online: 26 MAR 2008
- Published Print: 1 JAN 1991
Print ISBN: 9780470375105
Online ISBN: 9780470313848
Sapphire filament/alkoxy-derived YAG matrix composites with fugitive carbon interface layers (via CVD coating) were fabricated by hot pressing. It was reasoned that following oxidation of the carbon layer, sufficient mechanical interlocking would remain for load transfer, and the resulting void layer would maintain sufficiently weak interfaces for toughening. Filament push-out tests were performed to assess the interfacical shear strengths for various composite conditions (with and without carbon layer, oxidized, and long-term heat-treated). The average shear strength varied from 2.1 to 84.7 MPa for the as-hot pressed composite with a carbon interface coating. The filaments in the composite without carbon coating could not be pushed out and, based on the maximum load applied, the average shear strength was calculated to be more than 200 MPa. After the oxidation of the carbon coating layer in the composite, the measured average shear strengths were 10.4 and 13 MPa. The same composite was heat treated at 1500°C for 60 h in air and the average shear strength varied from 1.8 to 27.6 MPa. The microstructure of the heat-treated composite did not change from the as-processed condition, and this result implies the morphological stability of the sapphire/YAG composite at high temperatures.