T. Nozawa et al. Journal of Nuclear Materials 307-311(2002)1173-1177 possible that PlP derived Sic matrix with low crystalline Acknowledgements structure showed little radiation effects. In short. com- bination of both polymer-derived fiber and matrix might The authors would like to express their have minimized the influence of irradiation-induced preciation to Dr Snead at Oak Ridge National Labo- volume change. In addition to these facts, it can also be ratory, Dr Suyama at Toshiba Co Ltd, and Dr Sato at concluded that compositionally degraded Sic-C inter- Ube Industries for material supplies and Professor phase(Fig. 1) might be effective for radiation-resistant Narui at Tohoku Ur composites, for the explanation of the good resistance of was performed as a part of collaboration at Japan-US PIP SiC/Sic st neutron irradiation. However, Program for Irradiation Test of Fusion Materials (JU slight increase in flexural modulus occurred likely due to PITER) and Core Research for Evolutional Science and the partial crystallization of polymer-derived amor- Technology(CREST) program hous Sic matrix and fibers. Otherwise, significant matrix defects like pre-existing pores and cracks might have masked irradiation-induced changes. References [R H. Jones, LL. Snead, A Kohyama, P Fenici, Fus. Eng 4. Conclusions Des.41(1998)15 2L. L. Snead, R H. Jones, A. Kohyama, P. Fenici, J. Nucl Radiation effects on flexural properties of F-CVI, RS Mater.233-237(1996)23 and PIP SiC/SiC were investigated. This experiment was BY. Katoh, M. Kotani, H. Kishimoto, w. Yang, A characteristic in neutron irradiation at low doses up to Kohyama, J Nucl. Mater. 289(2001)42 0.4 dpa at high-temperature, 1073 K. Main conclusions 4L. L. Snead, Y. Katoh, A. Kohyama, J. L. Bailey, N L. were summarized as follows Vaughn, R.A. Lowden, J. Nucl. Mater. 283-287(2000) There were few influences of fibers and matrices on flexural properties of Sic/Sic against the neutron irra- [AJ Frias Robelo, H.W. Scholz, H. Kolbe, G.P. Tartaga- diation up to 0.4 dpa at 1073 K. Fiber and matrix lia, P. Fenici, J. Nucl. Mater. 263(1998)1582 6L. L. Snead, M.C. Osborne, R.A. Lowden, J. Strizak, RJ themselves did not degrade significantly by neutron ir Shinavski, K.L. More, W.S.Eatherly, J. Bailey, A M radiation at such low fluences. On the contrary, F/M Williams, J Nucl. Mater. 253(1998)20 interface was significantly damaged by irradiation up to [7G.w. Hollenberg. C H. Henager Jr, G.E. Youngblood, 0. 4 dpa which resulted in the decrease of the composite D.J. Trimble, S.A. Simonson, G.A. Newsome, E. Lewis, J strength, especially of the modulus of elasticity Nucl. Mater. 219(1995)70 8 M.C. Osborne, C.R. Hubbard, L L. Snead, D. Steiner, J F-CVI SiC/SiC showed a slight decrease in the elastic Nud. Mater.253(1998)67 modulus due to enlarged deflection by the degrada [9]GE. Youngblood, R.H. Jones, A Kohyama, LL. Snead, tion of Pyc interphase. However the composite J.Nucl. Mater.258-263(1998)1551 strength was still stable due to the dimensional and [10]LL. Snead, S.J. Zinkle, J.C. Hay, M.C. Osborne, Nucl. and Meth. B 141(1998)123. mechanical stability of fiber and matrix against neu- cawa. K. Bansaku N. Watanabe. Y. Nomura. M tron irradiation s.Sci. Technol. 58(1998)51 2. Composite strength and stiffness of rs SiC/SiC were [12] C1341 Flexural Properties of Continuous Fiber-Reinforced degraded by radiation damages of the bn interphase Advanced Ceramic Composites, in: Annual Book of 3. PiP SiC/Sic was stable against neutron irradiation ASTM Standards, ASTM, Conshohocken, PA, 1998, P. up to 0. 4 dpa because no significant degradation of [13]RJ. Price, J Nucl. Mater. 33(1969)17 after irradiation. Amorphous SiC fiber and matrix [14R.. Price, G.R. Hopkins, J Nucl. Mater. 108&109(1982) 732. did not degrade their flexural properties after neutron irradiation up to 0.4 dpa. Also compositionally de [15 M.C. Osborne, J C. Hay, LL. Snead, D. Steiner, J.Am. Ceram.Soc.82(1999)2490. graded Sic-C interface might be very effective for [16JHW. Simmons, Radiation Damage in Graphite, Inter- neutron irradiation and it is considered to be a pror national Series of Monographs in Nuclear Energy, vol. ising interface option for SiC/SiC composites 102. 1965. Pergamonpossible that PIP derived SiC matrix with low crystalline structure showed little radiation effects. In short, com￾bination of both polymer-derived fiber and matrix might have minimized the influence of irradiation-induced volume change. In addition to these facts, it can also be concluded that compositionally degraded SiC–C inter￾phase (Fig. 1) might be effective for radiation-resistant composites, for the explanation of the good resistance of PIP SiC/SiC against neutron irradiation. However, slight increase in flexural modulus occurred likely due to the partial crystallization of polymer-derived amor￾phous SiC matrix and fibers. Otherwise, significant matrix defects like pre-existing pores and cracks might have masked irradiation-induced changes. 4. Conclusions Radiation effects on flexural properties of F-CVI, RS and PIP SiC/SiC were investigated. This experiment was characteristic in neutron irradiation at low doses up to 0.4 dpa at high-temperature, 1073 K. Main conclusions were summarized as follows. There were few influences of fibers and matrices on flexural properties of SiC/SiC against the neutron irra￾diation up to 0.4 dpa at 1073 K. Fiber and matrix themselves did not degrade significantly by neutron ir￾radiation at such low fluences. On the contrary, F/M interface was significantly damaged by irradiation up to 0.4 dpa which resulted in the decrease of the composite strength, especially of the modulus of elasticity. 1. F-CVI SiC/SiC showed a slight decrease in the elastic modulus due to enlarged deflection by the degrada￾tion of PyC interphase. However the composite strength was still stable due to the dimensional and mechanical stability of fiber and matrix against neu￾tron irradiation. 2. Composite strength and stiffness of RS SiC/SiC were degraded by radiation damages of the BN interphase. 3. PIP SiC/SiC was stable against neutron irradiation up to 0.4 dpa because no significant degradation of fiber, matrix and F/M interface occurred before and after irradiation. Amorphous SiC fiber and matrix did not degrade their flexural properties after neutron irradiation up to 0.4 dpa. Also compositionally de￾graded SiC–C interface might be very effective for neutron irradiation and it is considered to be a prom￾ising interface option for SiC/SiC composites. Acknowledgements The authors would like to express their sincere ap￾preciation to Dr Snead at OakRidge National Labo￾ratory, Dr Suyama at Toshiba Co. Ltd., and Dr Sato at Ube Industries for material supplies and Professor Narui at Tohoku University for irradiation. This work was performed as a part of collaboration at Japan–US Program for Irradiation Test of Fusion Materials (JU￾PITER) and Core Research for Evolutional Science and Technology (CREST) program. References [1] R.H. Jones, L.L. Snead, A. Kohyama, P. Fenici, Fus. Eng. Des. 41 (1998) 15. [2] L.L. Snead, R.H. Jones, A. Kohyama, P. Fenici, J. Nucl. Mater. 233–237 (1996) 23. [3] Y. Katoh, M. Kotani, H. Kishimoto, W. Yang, A. Kohyama, J. Nucl. Mater. 289 (2001) 42. [4] L.L. Snead, Y. Katoh, A. Kohyama, J.L. Bailey, N.L. Vaughm, R.A. Lowden, J. Nucl. Mater. 283–287 (2000) 551. [5] A.J. Frias Robelo, H.W. Scholz, H. Kolbe, G.P. Tartaga￾lia, P. Fenici, J. Nucl. Mater. 263 (1998) 1582. [6] L.L. Snead, M.C. Osborne, R.A. Lowden, J. Strizak, R.J. Shinavski, K.L. More, W.S. Eatherly, J. Bailey, A.M. Williams, J. Nucl. Mater. 253 (1998) 20. [7] G.W. Hollenberg, C.H. Henager Jr., G.E. Youngblood, D.J. Trimble, S.A. Simonson, G.A. Newsome, E. Lewis, J. Nucl. Mater. 219 (1995) 70. [8] M.C. Osborne, C.R. Hubbard, L.L. Snead, D. Steiner, J. Nucl. Mater. 253 (1998) 67. [9] G.E. Youngblood, R.H. Jones, A. Kohyama, L.L. Snead, J. Nucl. Mater. 258–263 (1998) 1551. [10] L.L. Snead, S.J. Zinkle, J.C. Hay, M.C. Osborne, Nucl. Instrum. and Meth. B 141 (1998) 123. [11] T. Ishikawa, K. Bansaku, N. Watanabe, Y. Nomura, M. Shibuya, T. Hirokawa, Compos. Sci. Technol. 58 (1998) 51. [12] C1341 Flexural Properties of Continuous Fiber-Reinforced Advanced Ceramic Composites, in: Annual Bookof ASTM Standards, ASTM, Conshohocken, PA, 1998, p. 581. [13] R.J. Price, J. Nucl. Mater. 33 (1969) 17. [14] R.J. Price, G.R. Hopkins, J. Nucl. Mater. 108&109 (1982) 732. [15] M.C. Osborne, J.C. Hay, L.L. Snead, D. Steiner, J. Am. Ceram. Soc. 82 (1999) 2490. [16] J.H.W. Simmons, Radiation Damage in Graphite, Inter￾national Series of Monographs in Nuclear Energy, vol. 102, 1965, Pergamon. T. 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