K.L. More et al. /Composites: Part A 30(1999)463-470 milar degradation, but to a lesser extent, at 600C. [4] Filipuzzi L, Camus G, Naslain R, Thebault J Oxidation mechanisms Even at elevated temperatures, very little oxygen from and kinetics of lD-SiC/C/SiC composite materials: I. An experimen the environment actually makes its way to the interior tal approach. J Am Ceramic Soc 1994: 77: 459-466. of the composite via the BN; most of the degradation at 5 Lowden RA, Schwarz OJ, More KL. Ceramic Eng Sci Proc 1993;14(7-8)375-384 the interfaces is caused by the oxygen already incorpo [6 Naslain R, Dugne O, Guette A. Boron nitride interphase in ceramic- rated in the Bn lattice during processing. The interfaces matrix composites. J Am Ceramic Soc 1991: 74(1): 2482-2488. in the low-O BN were not degraded as much as those in [7] Matsuda T Stability to moisture for chemically vapour deposited BN the high-O BN, although some formation of silica was Mater sci198924:2353-2358 observed after 400 h at 950C in the low-O BN. Clearly [8 Baskaran $, Halloran Jw. Fibrous monolithic ceramics: Ill, mechan- ical properties and oxidation behavior of the SiC/BN system. J Am he main conclusion to be drawn from this work is that Ceramic Soc199477(5):1249-1255 relatively protective BN interface coatings can be [9 Morscher GN. Tensile stress rupture of SiC/SiCm Minicomposites achieved when the oxygen content is very low carbon and Bn interphases at elevated temperatures in air. J Am Ceramic Soc 1997: 80(8): 2029-2042 [10 Lowden RA, More KL, Schwarz OJ BN interface coatings for Nica- Acknowledgements lon/SiC composites(in preparation [11 Besmann TM, Lowden RA, Stinton DP, Starr TL. A method for the Research sponsored by the US Department of Energy id chemical vapor infiltration of ceramic composites. J Phy 9895(50( Colloque C5):229-239 Assistant Secretary for Energy Efficiency and Renewable [12] Allard LF, Ailey KS, Datye AK, Bigelow WC. An ex-situ reactor with Energy, the Office of Transportation Technologies, as pa anaerobic specimen transfer capabilities for TEM studies of reactive of the High Temperature Materials Laboratory Fellowship pecimens. Microscopy Microanalysis 1997: 3(2):595-5 program, and the Office of Industrial Technologies, Indus- [3] Thomas ), Weston NE, Connor TE. Turbostratic boron nitride, ther- trial Energy Efficiency Division, as part of the Continuous Fiber Ceramic Composites Program, both managed by Soc1963;84(24):4619-4622. 14 Sun EY, Nutt SR, Brennan JJ. Interfacial microstructure and chem- ockheed Martin Energy Research Corp. under contract try of Sic/Bn dual-coated nicalon-fiber-reinforced glass-ceramic Imber DE-ACo5-96OR22464 matrix composites. J Am Ceramic Soc 1994, 77(6): 1329-1339 15 Prouhet S, Camus G, Labrugere C, Guette A Mechanical character ization of Sic(O) fiber/SiC(CVI)matrix composites with a BN-inter References ase. J Am Ceramic Soc 1994: 77(3): 649-656 16 Sheldon BW, Sun EY, Nutt SR, Brennan JJ. Oxidation of BN-coated [1 Mah T, Mendiratta MG, Katz AP, Mazdiyasni Ks. Ceramic Bull SiC fibers in ceramic matrix composites. J Am Ceramic Soc 1987;66:304-308 996;792):539-543 [2] Lehman RL. In: Wachtman JB, editors. Treatise on materials science 17 Rocket TJ, Foster WR. J Am Ceramic Soc 1965: 48(2): 78 and technology. Structural ceramics, vol. 29. New York: Academic [18] Brozek V, Hubacek M. A contribution to the crystallochemistry of ss1989 BN. J Solid State Chem 1992: 100: 120-129 [3]Lowden RA Fiber coatings and the mechanical properties of a fiber- [19] Guimon C, Gonbeau D, Pfister-Guillouzo G, Dugne O, Guette A einforced ceramic composite. In: Sacks MD, editor. Ceramic trans- Naslain R, Lahaye M. XPS study of BN thin films deposited by ctions-advanced composite materials, vol. 19. Westerville, OH: CVD on Sic plane substrates. Surf Interface Analysis 1990; 16 The American Ceramic Society, 1991: 619-630 440-445similar degradation, but to a lesser extent, at 6008C. Even at elevated temperatures, very little oxygen from the environment actually makes its way to the interior of the composite via the BN; most of the degradation at the interfaces is caused by the oxygen already incorpo￾rated in the BN lattice during processing. The interfaces in the low-O BN were not degraded as much as those in the high-O BN, although some formation of silica was observed after 400 h at 9508C in the low-O BN. Clearly, the main conclusion to be drawn from this work is that relatively protective BN interface coatings can be achieved when the oxygen content is very low. Acknowledgements Research sponsored by the US Department of Energy, Assistant Secretary for Energy Efficiency and Renewable Energy, the Office of Transportation Technologies, as part of the High Temperature Materials Laboratory Fellowship program, and the Office of Industrial Technologies, Indus￾trial Energy Efficiency Division, as part of the Continuous Fiber Ceramic Composites Program, both managed by Lockheed Martin Energy Research Corp. under contract number DE-AC05-96OR22464. References [1] Mah T, Mendiratta MG, Katz AP, Mazdiyasni KS. Ceramic Bull 1987;66:304–308. [2] Lehman RL. In: Wachtman JB, editors. Treatise on materials science and technology. Structural ceramics, vol. 29. New York: Academic Press, 1989. [3] Lowden RA. Fiber coatings and the mechanical properties of a fiber￾reinforced ceramic composite. In: Sacks MD, editor. Ceramic trans￾actions—advanced composite materials, vol. 19. Westerville, OH: The American Ceramic Society, 1991:619–630. [4] Filipuzzi L, Camus G, Naslain R, Thebault J. Oxidation mechanisms and kinetics of 1D-SiC/C/SiC composite materials: I. An experimen￾tal approach. J Am Ceramic Soc 1994;77:459–466. [5] Lowden RA, Schwarz OJ, More KL. Ceramic Eng Sci Proc 1993;14(7–8):375–384. [6] Naslain R, Dugne O, Guette A. Boron nitride interphase in ceramic– matrix composites. J Am Ceramic Soc 1991;74(1):2482–2488. [7] Matsuda T. Stability to moisture for chemically vapour deposited BN. J Mater Sci 1989;24:2353–2358. [8] Baskaran S, Halloran JW. Fibrous monolithic ceramics: III, mechan￾ical properties and oxidation behavior of the SiC/BN system. J Am Ceramic Soc 1994;77(5):1249–1255. [9] Morscher GN. Tensile stress rupture of SiCf/SiCm Minicomposites with carbon and BN interphases at elevated temperatures in air. J Am Ceramic Soc 1997;80(8):2029–2042. [10] Lowden RA, More KL, Schwarz OJ. BN interface coatings for Nica￾lon/SiC composites (in preparation). [11] Besmann TM, Lowden RA, Stinton DP, Starr TL. A method for the rapid chemical vapor infiltration of ceramic composites. J Phys 1989;5(50 (Colloque C5)):229–239. [12] Allard LF, Ailey KS, Datye AK, Bigelow WC. An ex-situ reactor with anaerobic specimen transfer capabilities for TEM studies of reactive specimens. Microscopy Microanalysis 1997;3(2):595–596. [13] Thomas J, Weston NE, Connor TE. Turbostratic boron nitride, ther￾mal transformation to ordered-layer-lattice boron nitride. J Am Chem Soc 1963;84(24):4619–4622. [14] Sun EY, Nutt SR, Brennan JJ. Interfacial microstructure and chem￾istry of SiC/BN dual-coated nicalon–fiber-reinforced glass–ceramic matrix composites. J Am Ceramic Soc 1994;77(6):1329–1339. [15] Prouhet S, Camus G, Labrugere C, Guette A. Mechanical character￾ization of SiC(O) fiber/SiC (CVI) matrix composites with a BN-inter￾phase. J Am Ceramic Soc 1994;77(3):649–656. [16] Sheldon BW, Sun EY, Nutt SR, Brennan JJ. Oxidation of BN-coated SiC fibers in ceramic matrix composites. J Am Ceramic Soc 1996;79(2):539–543. [17] Rocket TJ, Foster WR. J Am Ceramic Soc 1965;48(2):78. [18] Brozek V, Hubacek M. A contribution to the crystallochemistry of BN. J Solid State Chem 1992;100:120–129. [19] Guimon C, Gonbeau D, Pfister-Guillouzo G, Dugne O, Guette A, Naslain R, Lahaye M. XPS study of BN thin films deposited by CVD on SiC plane substrates. Surf Interface Analysis 1990;16: 440–445. 470 K.L. More et al. / Composites: Part A 30 (1999) 463–470