Chapter 34. High Temperature Si-Doped BN Interphases for Woven SiC/SiC Composites

  1. Hua-Tay Lin and
  2. Mrityunjay Singh
  1. Gregory N. Morscher1,
  2. Frances Hurwitz2 and
  3. Hee Mann Yun3

Published Online: 26 MAR 2008

DOI: 10.1002/9780470294741.ch34

26th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: A: Ceramic Engineering and Science Proceedings, Volume 23, Issue 3

26th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: A: Ceramic Engineering and Science Proceedings, Volume 23, Issue 3

How to Cite

Morscher, G. N., Hurwitz, F. and Yun, H. M. (2008) High Temperature Si-Doped BN Interphases for Woven SiC/SiC Composites, in 26th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: A: Ceramic Engineering and Science Proceedings, Volume 23, Issue 3 (eds H.-T. Lin and M. Singh), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470294741.ch34

Author Information

  1. 1

    Ohio Aerospace Institute NASA Glenn Research Center Cleveland, OH 44135

  2. 2

    NASA Glenn Research Center Cleveland, OH 44135

  3. 3

    Cleveland State University NASA Glenn Research Center Cleveland, OH 44135

Publication History

  1. Published Online: 26 MAR 2008
  2. Published Print: 1 JAN 2002

ISBN Information

Print ISBN: 9780470375785

Online ISBN: 9780470294741

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Keywords:

  • chemical infiltration;
  • degradation;
  • formation;
  • crystallinity;
  • magnitude

Summary

The hydrolytic stability of high-temperature deposited Si-doped BN has been shown in the past to be superior in comparison to “pure” BN processed at similar or even higher temperatures. This type of material would be very desirable as a SiC/SiC composite interphase that is formed by chemical infiltration into multi-ply woven preform. However, due to rapid deposition on the preform outer surface at the high processing temperature, this has proven very difficult. To overcome this issue, single plies of woven fabric were infiltrated with Si-doped BN. Three composite panels of different SiC fiber types were fabricated with Si-doped BN interphases including Sylramic, Hi-Nicalon Type S and Sylramic-iBN fiber-types. The latter fiber-type possesses a thin in-situ grown BN layer on the fiber surface. High Si contents (∼ 7 to 10 a/o) and low oxygen contents (< 1 a/o) were achieved. All three composite systems demonstrated reasonable debonding and sliding properties. The coated Sylramic fabric and composites were weak due to fiber degradation apparently caused during interphase processing by the formation of TiN crystals on the fiber surface. The Hi-Nicalon Type S composites with Si-doped BN interphase were only slightly weaker than Hi-Nicalon Type S composites with conventional BN when the strength on the load-bearing fibers at failure was compared. On the other hand, the Sylramic-iBN fabric and composites with Si-doped BN showed excellent composite and intermediate temperature stress-rupture properties. Most impressive was the lack of any significant interphase oxidation on the fracture surface of stress-ruptured specimens tested well above matrix cracking at 815°C.