M. Takeda et al./ Composites Science and Technology 59(1999)813-819 ceramic fiber, HPZ, also decomposed with extra- References ordinary weight loss and crystallization. By contrast, Hi-NicalonTM, the SiC fiber with low oxygen contents [1] Yajima S, Hayashi J, Omori M, Okamura K. Development of prepared by irradiation-curing showed less change in SiC fibre with high tensile strength. Nature 1976: 261: 683-5 properties, showing much better thermal stability 2 Prewo KM. Brennan JJ, Layden GK. Fiber-reinforced glasses and glass-ceramics for high-performance applications. Am Ceram oc Bull986:65(2)305-14 33. Oxidation resistance 3 Strife JR, Brennan JJ, Prewo KM. Status of continuous fiber. reinforced ceramic processing techI The tensile strength of SiC fibers after exposure for 10 Ceram Eng Sci Proc 1990; 11(7-8): 8 h in humid air is shown in Fig. ll. All fibers tested 4 Clark TJ, Arons RM, Stamatoff JB, Rabe J. Thermal degrada- decreased their strength as compared with as-received on of Nicalon M SiC fibers. Ceram Eng Sci Proc 1985: 6(7- s,and showed lower strengths after exposure 5 Coustumer PL, Monthioux M, Oberlin A. Thermal degradatic higher temperatures. The strength of Hi-NicalonTM is mechanisms of a Nicalon M fiber as deduced from TEM obse roughly the same as that of Nicalon in the range of rations. Int Symp Carbon 1, Tsukuba, Japan 1990: 182-5 1273-1473K. much higher in 1573 and 1673 K. both [6 Delverdier O, Monthioux M, Oberlin A, Mocaer, D. Thermal evo- fibers became too weak to measure their strength after lutions of a cured (fibered) and uncured PCS-based ceramic micr 1773 K exposure for 10 h in humid air. The thickness of textural aspect. Int Symp Carbon 1, Tsukuba, Japan 1990. 190-3 Pysher DJ, Goretta KC, Hodder Jr. RS, Tressler RE Strengths the oxidation layers on the fibers after the test is shown of ceramic fibers at elevated temperatures. J Am Ceram Soc in Fig. 12. The oxide layer thickness on two kinds of the 1989;72(2):2848 fibers is almost the same. XRD patterns of as-fabricated 18] Simon G, Bunsell AR The creep of silicon carbide fibresJMat and oxidized fibers are shown in Fig. 13. Cristobalite formed in both SiC fibers after 1673 K exposure. Fur 9 Simon G, Bunsell AR. Mechanical and structural characteriza on of the Nicalon M silicon carbide fibre. J Mat Sci thermore, Sic crystal growth bserved in Nica 19849:3649-57 lonM by narrowing the XRD peak of B-SiCll1 [10] DiCarlo JA. Creep-related limitations of current ceramic fibers (0=35%)as shown in Fig. 13. Nicalon fiber is not only oxidized but also thermally degraded, as previously [1 Okamura K, Sato M Seguchi T Kawanishi S High-temperature strength improvement of SiC-O fiber by the reduction of oxygen atmosphere. Hi-NicalonTM fiber shows better oxidation content. Proceedings of the Ist Japanese International SAMPE resistance than Nicalon M in the range of 1573-1673K Symposium 1989: 929-34 on a strength basis [12] Takeda M, Imai Y, Ichikawa H, Ishikawa T, Seguchi T, Oka- mura K. Properties of the low oxygen content SiC fiber on high temperature heat treatment. Ceram Eng Sci Proc 1991; 12(7- 8):1007-18 4. Conclusions [13 Takeda M, Imai Y, Ichikawa H, Ishikawa T, Kasai N, Seguchi T, The properties of the low-oxygen SiC fiber, Hi-Nica fibers derived from polycarbosilane. Ceram Eng Sci Proc 1992:13(7-8):209-17 lonTM,prepared by the irradiation-curing method were (14) Lipowitz J, Rabe JA, Zangvil A, Xu Y Structure and properties investigated. This low-oxygen SiC fiber has excellent mechanical properties, which have a high tensile metric B-SiC composition. Ceram Eng Sci Proc I 17 strength of 2.8 GPa and a high tensile modulus of 270 GPa. Hi-NicalonTM retains high strength and modulus [5] Ishikawa T, Kohtoku y, kumagawa K, Yamamura T, Naga after exposure at 1873 K for 10 h in argon. It exhibits Lox-M. and HPz. as for oxidation in air. the oxide Ceram Eng Sci Proc 1996: 17(4):35-42. layer thickness of Nicalon TM and Hi-Nicalon M is [7 Lipowitz J. Polymer-derived ceramic fibers. Cer Bull almost the same. However. Hi-Nicalon TM fiber retained 1991:70(12):1888-94 higher strength than Nicalon in the range of 1573- [19] Honjo K, Shindo A Crystallinity of Sic coating on carbon fiber 1673K. Yogyo-kyokal-shi 1986: 94(1): 172-88ceramic ®ber, HPZ, also decomposed with extra￾ordinary weight loss and crystallization. By contrast, Hi-NicalonTM, the SiC ®ber with low oxygen contents prepared by irradiation-curing showed less change in properties, showing much better thermal stability. 3.3. Oxidation resistance The tensile strength of SiC ®bers after exposure for 10 h in humid air is shown in Fig. 11. All ®bers tested decreased their strength as compared with as-received ®bers, and showed lower strengths after exposure at higher temperatures. The strength of Hi-NicalonTM is roughly the same as that of NicalonTM in the range of 1273±1473 K, much higher in 1573 and 1673 K. Both ®bers became too weak to measure their strength after 1773 K exposure for 10 h in humid air. The thickness of the oxidation layers on the ®bers after the test is shown in Fig. 12. The oxide layer thickness on two kinds of the ®bers is almost the same. XRD patterns of as-fabricated and oxidized ®bers are shown in Fig. 13. Cristobalite formed in both SiC ®bers after 1673 K exposure. Fur￾thermore, SiC crystal growth was observed in Nica￾lonTM by narrowing the XRD peak of -SiC111 ( ˆ 35) as shown in Fig. 13. NicalonTM ®ber is not only oxidized but also thermally degraded, as previously discussed, during thermal exposure tests in an argon atmosphere. Hi-NicalonTM ®ber shows better oxidation resistance than NicalonTM in the range of 1573±1673 K on a strength basis. 4. Conclusions The properties of the low-oxygen SiC ®ber, Hi-Nica￾lonTM, prepared by the irradiation-curing method were investigated. This low-oxygen SiC ®ber has excellent mechanical properties, which have a high tensile strength of 2.8 GPa and a high tensile modulus of 270 GPa. Hi-NicalonTM retains high strength and modulus after exposure at 1873 K for 10 h in argon. It exhibits outstanding thermal stability compared with other polymer-derived ceramic ®bers, NicalonTM, TyrannoTM Lox-M, and HPZ. As for oxidation in air, the oxide layer thickness of NicalonTM and Hi-NicalonTM is almost the same. However, Hi-NicalonTM ®ber retained a higher strength than NicalonTM in the range of 1573± 1673 K. References [1] Yajima S, Hayashi J, Omori M, Okamura K. Development of a SiC ®bre with high tensile strength. Nature 1976;261:683±5. [2] Prewo KM, Brennan JJ, Layden GK. Fiber-reinforced glasses and glass-ceramics for high-performance applications. Am Ceram Soc Bull 1986;65(2):305±14. [3] Strife JR, Brennan JJ, Prewo KM. Status of continuous ®ber￾reinforced ceramic matrix composite processing technology. Ceram Eng Sci Proc 1990;11(7±8):871±919. [4] Clark TJ, Arons RM, Stamato€ JB, Rabe J. Thermal degrada￾tion of NicalonTM SiC ®bers. Ceram Eng Sci Proc 1985;6(7± 8):576±88. [5] Coustumer PL, Monthioux M, Oberlin A. Thermal degradation mechanisms of a NicalonTM ®ber as deduced from TEM obser￾vations. Int Symp Carbon 1, Tsukuba, Japan 1990: 182±5. [6] Delverdier O, Monthioux M, Oberlin A, Mocaer, D. Thermal evo￾lutions of a cured (®bered) and uncured PCS-based ceramic micro￾textural aspect. Int Symp Carbon 1, Tsukuba, Japan 1990: 190±3. [7] Pysher DJ, Goretta KC, Hodder Jr. RS, Tressler RE. Strengths of ceramic ®bers at elevated temperatures. J Am Ceram Soc 1989;72(2):284±8. [8] Simon G, Bunsell AR. The creep of silicon carbide ®bres. J Mat Sci Lett 1983;2:80±2. [9] Simon G, Bunsell AR. Mechanical and structural characteriza￾tion of the NicalonTM silicon carbide ®bre. J Mat Sci 1984;19:3649±57. [10] DiCarlo JA. Creep-related limitations of current ceramic ®bers. Proceedings of the International Workshop Adv. Inorg. Fiber Technology, Melbourne, Australia, 1992. p. 67. [11] Okamura K, Sato M, Seguchi T, Kawanishi S. High-temperature strength improvement of Si±C±O ®ber by the reduction of oxygen content. Proceedings of the 1st Japanese International SAMPE Symposium 1989: 929±34. [12] Takeda M, Imai Y, Ichikawa H, Ishikawa T, Seguchi T, Oka￾mura K. Properties of the low oxygen content SiC ®ber on high temperature heat treatment. Ceram Eng Sci Proc 1991;12(7± 8):1007±18. [13] Takeda M, Imai Y, Ichikawa H, Ishikawa T, Kasai N, Seguchi T, Okamura K. Thermal stability of the low oxygen silicon carbide ®bers derived from polycarbosilane. Ceram Eng Sci Proc 1992;13(7±8):209±17. [14] Lipowitz J, Rabe JA, Zangvil A, Xu Y. Structure and properties of SylramicTM silicon carbide ®berÐa polycrystalline, stoichio￾metric -SiC composition. Ceram Eng Sci Proc 1997;18(3):147± 57. [15] Ishikawa T, Kohtoku Y, Kumagawa K, Yamamura T, Naga￾sawa T. High-strength alkali-resistant sintered SiC ®bre stable to 2200C. Nature 1998;391:773±4. [16] Takeda M, Sakamoto J, Saeki A, Ichikawa H. Mechanical and structural analysis of silicon carbide ®ber Hi-NicalonTM Type S. Ceram Eng Sci Proc 1996;17(4):35±42. [17] Lipowitz J. Polymer-derived ceramic ®bers. Cer Bull 1991;70(12):1888±94. [18] TyrannoTM ®ber Technical Data Sheet, Ube Industries. [19] Honjo K, Shindo A. Crystallinity of SiC coating on carbon ®ber. Yogyo-kyokai-shi 1986;94(1):172±88. M. Takeda et al. / Composites Science and Technology 59 (1999) 813±819 819