L.U.J.T. Ogbuji/ Journal of the European Ceramic Society 23(2003)613-617 from sizing residue in the case of Sylramic fibers. The 5. Ogbuji, L U.J. T, A pervasive mode of oxidative degradatic carbon caused degradation by providing an easy route a Sic-SiC composite. J. Am. Ceram. Soc., 1998. 81(11). 2777- for deep penetration of the composite by ambient oxi- dants. The samples that were free of elemental carbon 6. Morscher. G. N, Tensile stress-rupture of SiC/Sic mini- proved to be resistant to pest degradation composite with carbon and boron nitride interphases at elevated mperatures in air. J. Am. Cram. Soc., 1997, 80(8), 2029-2042. Therefore, the severest form of pest degradation in 7. Jacobson, N.S., Morscher, G.N. Bryant, D. R. and Tressler. Sic/BN SIC composites can be suppressed by ensuring R. E. High-temperature oxidation of boron nitride: II BN layers that they are free of elemental carbon and its precursors in composites. J. Am. Ceram. Soc.. 1999, 82(6). 1473-1482. 8. Morscher, G. N, Bryant, D. R. and Tressler, R. E, Environ- in the interphase region mental durability of BN-based interphases(for SiC/SiC com tes) mperatures Ceramic Engineering Science Proceedings, 1997 Acknowledgements 8(3),525-533. 9. Evans, A. G. Zok, F. W, McMeeking. R. M. and Du. Z.Z. This work was done at NASa grc under contract Models of high-temperature, environmentally assisted embrittle. ment in ceramic-matrix composites. J. Am. Ceram. Soc., 1996 NAS3-98008. The author acknowledges the assistand 79(9),2345-2352 of M. Cuy(APBR), T. McCue(S-4700 SEM), D 10. Heredia, F. E, McNulty, J. C, Zok, F. w. and Evans, A. G Wheeler(AES); with sample exposure and examination; Oxidation embrittlement probe for ceramic-matrix composites. helpful discussions with G. Morscher on pesting modes J.Am. Ceran.Soc,1995,78(8),2097-2100. are highly appreciated 11. Morscher. G.N. Hurst. J. and Brewer. D. Intermediate-tem. perature stress rupture of a woven Hi-Nicalon, BN-interphase Sic-matrix composite in air. J. Am. Ceram. Soc., 2000. 83(6) References 12. Ogbuji, L. U. J. T, Identification of carbon sublayer in a Hi- Nicalon/BN/SIC composite. J. Mat. Sci. Lett., 1999, 18, 18 1. DiCarlo, J, Yun, H.M., Morscher, G.N., and Ogbuji, L. U.J.T. 13. Ogbuji, L.U.J. T, Silicon-based ceramic matrix composites for ings of Materials Week 2001, Munich Giemang. D. and Jones, In Proc. PAR- SONS 2000: Advanced Materials for 2lst Century Turbines and R. H. Oxidation of the carbon interface in Nica Power Plants, ed. A. Strang et al. The University Press, Cam- orced SiC composite. J. Am. Ceram. idge. 20 3. Heredia, F. E, McNulty, J C, Zok, F.w. and Evans, A G 14. Brewer, D, HSR/EPM combustor materials development pro- Oxidation embrittlement probe for ceramic-matrix composites gram.MatSci.and Eng,1999,A261,284-291 J.Am. Ceran.Soc.,l995,78(8),2097-210 15. Rebillat F. Gallet. SL. Bourrat.X. and Naslain R. Oxidation 4. Sheldon. B. W. Sun. E. Y. Nutt. S. R. and Brennan. J J. Oxi- sistance of BN coatings with different textures (poster). Mate- dation of BN-coated SiC fibers in ceramic-matrix composites rials Week 2001. Munich J.Am. Ceran.Soc,1996,79(2),539-543 16. Yun, H, and DiCarlo, J, unpublished workfrom sizing residue in the case of Sylramic fibers. The carbon caused degradation by providing an easy route for deep penetration of the composite by ambient oxi￾dants. The samples that were free of elemental carbon proved to be resistant to pest degradation. Therefore, the severest form of pest degradation in SiC/BN/SiC composites can be suppressedby ensuring that they are free of elemental carbon andits precursors in the interphase region. Acknowledgements This work was done at NASA GRC under contract # NAS3-98008. The author acknowledges the assistance of M. Cuy (APBR), T. McCue (S-4700 SEM), D. Wheeler (AES); with sample exposure andexamination; helpful discussions with G. Morscher on pesting modes are highly appreciated. References 1. DiCarlo, J., Yun, H.M., Morscher, G.N., andOgbuji, L.U.J.T., Progress in SiC/SiC composites for engine applications. Proceed￾ings of Materials Week 2001, Munich, Germany. 2. Windisch, C. F., Henager, C. H., Springer, G. D. and Jones, R. H., Oxidation of the carbon interface in Nicalon-fiber-rein￾forcedSiC composite. J. Am. Ceram. Soc., 1997, 80(3), 569–574. 3. Heredia, F. E., McNulty, J. C., Zok, F. W. and Evans, A. G., Oxidation embrittlement probe for ceramic-matrix composites. J. Am. Ceram. Soc., 1995, 78(8), 2097–2100. 4. Sheldon, B. W., Sun, E. Y., Nutt, S. R. and Brennan, J. J., Oxi￾dation of BN-coated SiC fibers in ceramic-matrix composites. J. Am. Ceram. Soc., 1996, 79(2), 539–543. 5. Ogbuji, L. U. J. T., A pervasive mode of oxidative degradation in a SiC-SiC composite. J. Am. Ceram. Soc., 1998, 81(11), 2777– 2784. 6. Morscher, G. N., Tensile stress-rupture of SiC/SiC mini￾composite with carbon andboron nitride interphases at elevated temperatures in air. J. Am. Cram. Soc., 1997, 80(8), 2029–2042. 7. Jacobson, N. S., Morscher, G. N., Bryant, D. R. andTressler, R. E., High-temperature oxidation of boron nitride: II BN layers in composites. J. Am. Ceram. Soc., 1999, 82(6), 1473–1482. 8. Morscher, G. N., Bryant, D. R. andTressler, R. E., Environ￾mental durability of BN-based interphases (for SiC/SiC compo￾sites) in H2O-containing atmospheres at intermediate temperatures. Ceramic Engineering & Science Proceedings, 1997, 18(3), 525–533. 9. Evans, A. G., Zok, F. W., McMeeking, R. M. andDu, Z. Z., Models of high-temperature, environmentally assisted embrittle￾ment in ceramic-matrix composites. J. Am. Ceram. Soc., 1996, 79(9), 2345–2352. 10. Heredia, F. E., McNulty, J. C., Zok, F. W. and Evans, A. G., Oxidation embrittlement probe for ceramic-matrix composites. J. Am. Ceram. Soc., 1995, 78(8), 2097–2100. 11. Morscher, G. N., Hurst, J. andBrewer, D., Intermediate-tem￾perature stress rupture of a woven Hi-Nicalon, BN-interphase, SiC-matrix composite in air. J. Am. Ceram. Soc., 2000, 83(6), 1441–1449. 12. Ogbuji, L. U. J. T., Identification of carbon sublayer in a Hi￾Nicalon/BN/SiC composite. J. Mat. Sci. Lett., 1999, 18, 1825– 1827. 13. Ogbuji, L. U. J. T., Silicon-basedceramic matrix composites for advanced turbine engines: degradation issues. In Proc. PAR￾SONS 2000: Advanced Materials for 21st Century Turbines and Power Plants, ed. A. Strang et al. The University Press, Cam￾bridge, 2000, pp. 767–778. 14. Brewer, D., HSR/EPM combustor materials development pro￾gram. Mat. Sci. and Eng., 1999, A261, 284–291. 15. Rebillat, F., Gallet, S.L., Bourrat, X., andNaslain, R., Oxidation resistance of BN coatings with different textures (poster). Mate￾rials Week 2001, Munich. 16. Yun, H., andDiCarlo, J., unpublishedwork. L.U.J.T. Ogbuji / Journal of the European Ceramic Society 23 (2003) 613–617 617