Chapter 62. Improved Fiber Coatings for Nicalon®/SiC Composites

  1. John B. Wachtman Jr.
  1. Richard A. Lowden,
  2. Otto J. Schwarz and
  3. Karren L. More

Published Online: 28 MAR 2008

DOI: 10.1002/9780470314180.ch62

Proceedings of the 17th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 14, Issue 7/8

Proceedings of the 17th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 14, Issue 7/8

How to Cite

Lowden, R. A., Schwarz, O. J. and More, K. L. (1993) Improved Fiber Coatings for Nicalon®/SiC Composites, in Proceedings of the 17th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 14, Issue 7/8 (ed J. B. Wachtman), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470314180.ch62

Author Information

  1. Oak Ridge National Laboratory, P. O. Box 2008, Oak Ridge, TN 37831-6063

Publication History

  1. Published Online: 28 MAR 2008
  2. Published Print: 1 JAN 1993

ISBN Information

Print ISBN: 9780470375266

Online ISBN: 9780470314180

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Keywords:

  • interlayers;
  • densification;
  • microstructures;
  • oxidation;
  • interaction

Summary

Boron-doped carbon and boron nitride were examined as improved interface coatings for Nicalon®/SiC composites. The interlayers were deposited on fiber preforms prior to densification by chemical vapor infiltration (CVI). Room-temperature flexure strengths of as-fabricated composites and specimens exposed for 24 h in air at 1273 K were measured to assess the effectiveness of the fiber coatings. Compositions and microstructures of the interlayers were characterized using electron microscopy. Beyond a minimum concentration, boron doping of the carbon interface enhanced the oxidation resistance of the composites. Higher levels of boron, however, produced decreased strength and toughness. Composites with BN fiber coatings exhibited improved post-exposure strength retention, but were embrittled by the treatments. The loss of toughness appeared to be a result of chemical interaction between the fiber and oxygen in the BN interlayer.