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Characterization of Boron Nitride Coated Silicon Carbide Fibers and Composites

Published online by Cambridge University Press:  02 July 2020

Mani Gopal*
Affiliation:
Department of Materials Science and Mineral Engineering, University of California at Berkeley, and Center for Advanced Materials, Lawrence Berkeley National Laboratory, Berkeley, CA94720
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Extract

Silicon carbide (SiC) composites are receiving much attention for structural use at high temperatures. One class of composites are those reinforced with SiC fibers. The SiC fibers are coated with boron nitride (BN) which is weakly bonded to the fiber. During fracture, the coating deflects cracks causing pull-out of the fibers (Fig. 1). This process of fiber pull-out consumes energy and increases the toughness of the composite. Although much work has been done on characterizing these materials by SEM, not much has been done using TEM due to difficulties in specimen preparation. The purpose of this study is to characterize these fibers and composites using conventional and analytical TEM.

In this study, TEM specimens were prepared by dimpling and ion milling. Careful control of the preparation was needed to ensure the integrity of the SiC-BN interface. Figure 2a is a TEM image of the fiber showing delamination at the SiC-BN interface.

Type
Ceramics and Ceramic Composites
Copyright
Copyright © Microscopy Society of America 1997

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References

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The author thanks Prof. Gareth Thomas for his valuable suggestions. The author thanks T. Kameda of Toshiba Corp. for supplying the materials, C. Hetherington and C. Nelson of NCEM for help with EELS imaging on the Philips CM200, and DOE/LBL for funding (DE-AC-03-76SF0OO98).Google Scholar