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The Stability of BN Interfacial Coatings in CFCC Systems During Oxidation and Exposure to Moisture

Published online by Cambridge University Press:  02 July 2020

K.S. Ailey ,
K.L. More  and
R.A. Lowden
K.S. Ailey
Affiliation:
Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC27695
K.L. More
Affiliation:
Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, TN37831
R.A. Lowden
Affiliation:
Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, TN37831
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Extract

The mechanical reliability of ceramic matrix composites (CMCs) at elevated temperatures in oxidative environments is primarily dependent upon the chemical and structural stability of the fiber/matrix interface. Graphitic carbon coatings have traditionally been used to control the interfacial properties in CMCs, however, their use is limited in high temperature oxidative environments due to the loss of carbon and subsequent oxidation of the fiber and matrix. Thus, BN is being investigated as an alternative interfacial coating since it has comparable room temperature properties to carbon with improved oxidation resistance. The stability of BN interfaces in SiC/SiC composites is being investigated at elevated temperatures in either flowing oxygen or environments containing water vapor. The effect of several factors on BN stability, including crystallographic structure, extent of BN crystallization, and impurity content, are being evaluated.

Nicalon™ fiber preforms were coated with ≈ 0.4 μm of BN by CVD using BCl3, NH3, and H2 at 1373 K. The coated preforms were densified using a forced-flow chemical vapor infiltration (FCVI) technique developed at ORNL.

Type
Ceramics and Ceramic Composites
Information
Microscopy and Microanalysis , Volume 3 , Issue S2: Proceedings: Microscopy & Microanalysis '97, Microscopy Society of America 55th Annual Meeting, Microbeam Analysis Society 31st Annual Meeting, Histochemical Society 48th Annual Meeting, Cleveland, Ohio, August 10-14, 1997 , August 1997 , pp. 729 - 730
Copyright
Copyright © Microscopy Society of America 1997

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References

1. Stinton, D.P.et al., Amer. Cer. Soc. Bull. 65(2)(1986)347-50.Google Scholar

2. Research sponsored by Office of Industrial Tech, Improved Energy Prod. Div. and Advanced Industrial Concepts Div., and the Assist. Sec. for Energy Efficiency and Renewable Energy, Office of Trans. Tech., as a part of the HTML Fellowship Program, both sponsored by the U.S. DOE, under contract DE-AC05- 96OR22464 managed by Lockheed Martin Energy Research, CorpGoogle Scholar