N P Bansal Journal of the European Ceramic Society 29(2009)525-535 MC+ HC(trace) Powder scrapped 广HC 20, deg Fig 15. X-ray diffraction spectra from surfaces of Hi-Nicalon/BN/SiC/BSAS composites:(a) as-fabricated and(b) annealed at 1200 C for 100h in air. in SiOz but poorer in Bao and Al2O3 than celsian. The XRD 5. Conclusions patterns taken from the as-fabricated CMC and that for 100h in air at 1200C are given in Fig. 15. Onl Celsian matrix composites reinforced with BN/SiC-coated phase is detected in the as-fabricated sample wherea Hi-Nicalon fibers are stable in air up to 1100C. However, their ind some amorphous phase are present in the 1200C-annealed mechanical properties are severely degraded at higher tempera CMC. Formation of a low-melting glass phase has also been tures due to oxidation er during the study of BsAs environmental ba rier coating(EBC)on Si-based ceramic substrates such as CV Acknowledgments SiC and SiCr/SiC composite. On heat treatment, the plasma sprayed BSAS coating reacted with the silica layer, formed from Thanks are due to John Setlock, Ron Phillips, Terry Kacik, oxidation of the Si-based ceramic substrate, resulting in low- and Ralph Garlick for their technical assistance during compos melting ternary glass phase which was found to be richer in ite processing and characterization. Don Wheeler assisted with SiOz but poorer in BaO and Al2O3 than celsian. Formation of the scanning Auger analysis and Jeff Eldridge with fiber push-in amorphous silica, due to the oxidation of SiC whiskers, has also testing. This research was supported by NASAs Ultra Efficient been reported during oxidation study of Sic whisker reinforced Engine Technology (UEET) Project and Hypersonic Project of mullite/zirconia composites at 1000-1350C. At 1200.c the Fundamental Aeronautics Progran or higher temperatures, formation of zircon was observed from the reaction between ZrO2 and Sio2. Secondary mul- References lite were also formed through a solution-reprecipita mechanism I. Bansal, N. P, ed, Handbook of Ceramic Composites. Kluwer Academic 2. Boccaccini, A. R, Continuous fiber reinforced glass and glass-ceramic matrix composites. In Handbook of Ceramic Composites, ed. N. P. Ban Kluwer Academic Publishers, Boston(MA), 2005, Pp. 461-484 <. Room temperature mechanical properties of BN/SiC-coated 3. Bansal, N.P., Ceramic fiber-reinforced glass-ceramic matrix composite. US Hi-Nicalon fiber-reinforced celsian matrix composites remained Patent 5,214004,May25,1993 unaffected after thermal aging for 100 h in air at various tem- 4. Bansal, N P, Method of producing a ceramic fiber-reinforced glass-ceramic peratures up to 1100oC. A thin white layer had formed on matrix composite. US Patent 5, 281, 559, January 25, 1994 the surface of the 1100C annealed sample and its density 5. Bansal. N. P. CVD SiC fiber-reinforced barium aluminosilicate glass-ceramic matrix composites. Mater Sci. Eng. A, 1996. 220(1-2), decreased from 3.09 to 2.90g/cm. However, the specimen 129-139. annealed at 1200C gained 0.43% weight, deformed in shape 6. Bansal, N.P., McCluskey, P, Linsey, G, Murphy, Dand Levan,G, Nicalon and size, and was covered with a thick shiny white porous layer fiber-reinforced celsian glass-ceramic matrix composites In Proceedin that could be easily peeled off. From X-ray diffraction analy f Annual HITEMP Review, Vol. Ill, 1995, NASA CP 10178, P. 41 sis, this surface layer was found to consist of amorphous and monoclinic celsian phases. The fibers in this surface layer had 7. Bansal, N. P, SiC fiber-reinforced celsian composites. In Handbook of Ceramic Composites, ed N. P. Bansal. Kluwer Academic Publishers, Boston broken into small pieces. The fiber-matrix interface in the inte- (MA),2005,pp.227-249 rior of the coupons was characterized through fiber push-in 8. Bansal, N P and Drummond Ill,CH,Kinetics of hexacelsian-to-celsian hnique. Values of debond stress, od, and frictional sliding phase transformation in SrAl2Si2O8. J. Am. Ceram. Soc., 1993, 76(5), stress, tf, for the as-fabricated CMC were 0.31+0.14 GPa and 9. Bansal. N. P. Mechanical behavior of silicon carbide fiber-reinforced stron- 0.4+3.1 MPa, respectively, compared with 0.53+0.47 GPa and 8. 33+ 1.72 MPa for the fibers in the interior of the 1200oC annealed sample indicating hardly any change in fiber-matrix 10. Bansal, N P and k J. A, Fabrication of fiber-reinforced celsian matrix interface Microstructures of the annealed specimens were inves- omposites. Composites: Part A, 2001, 32, 1021-1029 tigated using SEM. Only the surface ply of the 1200 C annealed 11.Bansal, N. P, Strong and tough Hi-Nicalon fiber-reinforced celsian matrix omposites. J. Am. Ceram. Soc., 1997, 80(9), 2407-2409. specimens had degraded from oxidation whereas the bulk inte- 12. Gyekenyesi, J.Z. and Bansal, N P. High temperature mechanical properties rior part of the CMC was unaffected of Hi-Nicalon fiber-reinforced celsian composites In Advances in Ceramic534 N.P. Bansal / Journal of the European Ceramic Society 29 (2009) 525–535 Fig. 15. X-ray diffraction spectra from surfaces of Hi-Nicalon/BN/SiC/BSAS composites: (a) as-fabricated and (b) annealed at 1200 ◦C for 100 h in air. in SiO2 but poorer in BaO and Al2O3 than celsian. The XRD patterns taken from the as-fabricated CMC and that annealed for 100 h in air at 1200 ◦C are given in Fig. 15. Only celsian phase is detected in the as-fabricated sample whereas celsian and some amorphous phase are present in the 1200 ◦C-annealed CMC. Formation of a low-melting glass phase has also been reported31 earlier during the study of BSAS environmental bar￾rier coating (EBC) on Si-based ceramic substrates such as CVD SiC and SiCf/SiC composite. On heat treatment, the plasma sprayed BSAS coating reacted with the silica layer, formed from oxidation of the Si-based ceramic substrate, resulting in low￾melting ternary glass phase which was found to be richer in SiO2 but poorer in BaO and Al2O3 than celsian. Formation of amorphous silica, due to the oxidation of SiC whiskers, has also been reported during oxidation study of SiC whisker reinforced mullite/zirconia composites32 at 1000–1350 ◦C. At 1200 ◦C or higher temperatures, formation of zircon was observed from the reaction between ZrO2 and SiO2. Secondary mul￾lite grains were also formed through a solution-reprecipitation mechanism. 4. Summary Room temperature mechanical properties of BN/SiC-coated Hi-Nicalon fiber-reinforced celsian matrix composites remained unaffected after thermal aging for 100 h in air at various tem￾peratures up to 1100 ◦C. A thin white layer had formed on the surface of the 1100 ◦C annealed sample and its density decreased from 3.09 to 2.90 g/cm3. However, the specimen annealed at 1200 ◦C gained 0.43% weight, deformed in shape and size, and was covered with a thick shiny white porous layer that could be easily peeled off. From X-ray diffraction analy￾sis, this surface layer was found to consist of amorphous and monoclinic celsian phases. The fibers in this surface layer had broken into small pieces. The fiber–matrix interface in the inte￾rior of the coupons was characterized through fiber push-in technique. Values of debond stress, σd, and frictional sliding stress, τf, for the as-fabricated CMC were 0.31 ± 0.14 GPa and 10.4 ± 3.1 MPa, respectively, compared with 0.53 ± 0.47 GPa and 8.33 ± 1.72 MPa for the fibers in the interior of the 1200 ◦C annealed sample indicating hardly any change in fiber–matrix interface. Microstructures of the annealed specimens were inves￾tigated using SEM. Only the surface ply of the 1200 ◦C annealed specimens had degraded from oxidation whereas the bulk inte￾rior part of the CMC was unaffected. 5. Conclusions Celsian matrix composites reinforced with BN/SiC-coated Hi-Nicalon fibers are stable in air up to 1100 ◦C. However, their mechanical properties are severely degraded at higher tempera￾tures due to oxidation. Acknowledgments Thanks are due to John Setlock, Ron Phillips, Terry Kacik, and Ralph Garlick for their technical assistance during compos￾ite processing and characterization. Don Wheeler assisted with the scanning Auger analysis and Jeff Eldridge with fiber push-in testing. This research was supported by NASA’s Ultra Efficient Engine Technology (UEET) Project and Hypersonic Project of the Fundamental Aeronautics Program. References 1. Bansal, N. P., ed., Handbook of Ceramic Composites. Kluwer Academic Publishers, Boston (MA), 2005. 2. Boccaccini, A. R., Continuous fiber reinforced glass and glass–ceramic matrix composites. In Handbook of Ceramic Composites, ed. N. P. Bansal. Kluwer Academic Publishers, Boston (MA), 2005, pp. 461–484. 3. Bansal, N. P., Ceramic fiber-reinforced glass–ceramic matrix composite. US Patent 5,214,004, May 25, 1993. 4. Bansal, N. P., Method of producing a ceramic fiber-reinforced glass–ceramic matrix composite. US Patent 5,281,559, January 25, 1994. 5. Bansal, N. P., CVD SiC fiber-reinforced barium aluminosilicate glass–ceramic matrix composites. Mater. Sci. Eng. A, 1996, 220(1–2), 129–139. 6. Bansal, N. P., McCluskey, P., Linsey, G., Murphy, D. and Levan, G., Nicalon fiber-reinforced celsian glass–ceramic matrix composites. In Proceedings of Annual HITEMP Review, Vol. III, 1995, NASA CP 10178, p. 41-1– 14. 7. Bansal, N. P., SiC fiber-reinforced celsian composites. In Handbook of Ceramic Composites, ed. N. P. Bansal. Kluwer Academic Publishers, Boston (MA), 2005, pp. 227–249. 8. Bansal, N. P. and Drummond III, C. H., Kinetics of hexacelsian-to-celsian phase transformation in SrAl2Si2O8. J. Am. Ceram. Soc., 1993, 76(5), 1321–1324. 9. Bansal, N. P., Mechanical behavior of silicon carbide fiber-reinforced stron￾tium aluminosilicate glass–ceramic composites. Mater. Sci. Eng. A, 1997, 231(1–2), 117–127. 10. Bansal, N. P. and Setlock, J. A., Fabrication of fiber-reinforced celsian matrix composites. Composites: Part A, 2001, 32, 1021–1029. 11. Bansal, N. P., Strong and tough Hi-Nicalon fiber-reinforced celsian matrix composites. J. Am. Ceram. Soc., 1997, 80(9), 2407–2409. 12. Gyekenyesi, J. Z. and Bansal, N. P. High temperature mechanical properties of Hi-Nicalon fiber-reinforced celsian composites. In Advances in Ceramic