N. Igawa et al. Journal of Physics and Chemistry of Solids 66(2005)551-554 SiC/C interphase is to be expected to improve the high- and Technology/Advanced Material Systems for Energy temperature mechanical properties Conversion Program sponsored by Japan Science and 4. Concl The process optimization for FCVI-SiC based tes with advanced SiC fibers such as Tyranno SA was [1]R H. Jones, L.L. Seand, A. Kohyama, P. Fenici, Recent advances in the carried out. The new SiC/SiC composites exhibited development of SiC/SiC as a fusion significant improvement in porosity reduction and th Ds.41(1998)15-24 uniform distribution of pores by decreasing the flow rate [2] A Hasegawa, A Kohyama, R.H. Jones, L.L. Snead,, P Fenici, Critical of mrs and h es at the latter part of the FCVI 6beress. The uniform interphases between advanced SiC Mater.283-287(2000)128-137 [3] R.H. Jones, L. Giancarli, A. Hasegawa, Y. Katoh, A. Kohyama and FCVI-Sic matrix could be obtained by B. Riccardi, L.L. Snead, w.J. Weber, Promise and challenges of reversing the gas-flow direction mid-way through the SiC/SiC composites for fusion energy applications. J. Nucl. Mater. coating process. The tensile strength was slightly 307-311(2002)1057-1072 increased with thickness of carbon interphase in the daA. Ur J. Sakamoto. Y. Imai. Microstructure and range of 20-250 nm. We confirmed the fabric layer oxidative degradation behavior of silicon carbide fiber Hi-Nicalon type S,J.Nucl. Mater.258-263(1998)1594-1599 orientation and multilayer Sic/C interphase were very [5 T Ishikawa, Y. Kohtoku, K Kumagawa, T Yamamura. T Nagasawa, ffective to improve the tensile strength High-strength alkali-resistant sintered SiC fibre stable to 2.200C. [6 T.M. Besmann, J.C. McLaughlin, H-T. Lin, Fabrication of ceramic Acknowledgements omposites: forced CVI, J Nucl. Mater. 219(1995)31-35 [7 N. Igawa, T. Taguchi, L L. Snead, Y. Katoh, S. Jitsukawa. A. Kohyama, J.C. McLaughlin, Optimizing the fabrication process The authors would like to thank dr t.m. besmann at Oak for superior mechanical properties in the FCVI SiC matrix/stoichio- Ridge National Laboratory for useful discussion. This study metric SiC fiber composites system, J. Nucl. Mater. 307-311(2002) has been carried out under the US-DOEJAERI Collabora- tive program on fwb structural materials in mixed- [8 onaka, Y. Katoh, A. Kohyama, T. Taguchi of chemical vapor infiltrated Spectrum Fission Reactors, Phase IV. This study was also advanced SiC fiber composites at elevated temperatures, Ceram. Trans. supported by the Core Research for Evolutional Science 144(2002)245-252SiC/C interphase is to be expected to improve the high￾temperature mechanical properties. 4. Conclusion The process optimization for FCVI-SiC based compo￾sites with advanced SiC fibers such as Tyranno SA was carried out. The new SiC/SiC composites exhibited significant improvement in porosity reduction and the uniform distribution of pores by decreasing the flow rate of MTS and H2 gases at the latter part of the FCVI process. The uniform interphases between advanced SiC fibers and FCVI-SiC matrix could be obtained by reversing the gas-flow direction mid-way through the coating process. The tensile strength was slightly increased with thickness of carbon interphase in the range of 20–250 nm. We confirmed the fabric layer orientation and multilayer SiC/C interphase were very effective to improve the tensile strength. Acknowledgements The authors would like to thank Dr T.M. Besmann at Oak Ridge National Laboratory for useful discussion. This study has been carried out under the US-DOE/JAERI Collabora￾tive Program on FWB Structural materials in Mixed￾Spectrum Fission Reactors, Phase IV. This study was also supported by the Core Research for Evolutional Science and Technology/Advanced Material Systems for Energy Conversion Program sponsored by Japan Science and Technology Corporation. References [1] R.H. Jones, L.L. Seand, A. Kohyama, P. Fenici, Recent advances in the development of SiC/SiC as a fusion structural material, Fusion Eng. Des. 41 (1998) 15–24. [2] A. Hasegawa, A. Kohyama, R.H. Jones, L.L. Snead,, P. Fenici, Critical issues and current status of SiC/SiC composites for fusion, J. Nucl. Mater. 283–287 (2000) 128–137. [3] R.H. Jones, L. Giancarli, A. Hasegawa, Y. Katoh, A. Kohyama, B. Riccardi, L.L. Snead, W.J. Weber, Promise and challenges of SiC/SiC composites for fusion energy applications, J. Nucl. Mater. 307–311 (2002) 1057–1072. [4] M. Takeda, A. Urano, J. Sakamoto, Y. Imai, Microstructure and oxidative degradation behavior of silicon carbide fiber Hi-Nicalon type S, J. Nucl. Mater. 258–263 (1998) 1594–1599. [5] T. Ishikawa, Y. Kohtoku, K. Kumagawa, T. Yamamura, T. Nagasawa, High-strength alkali-resistant sintered SiC fibre stable to 2,200 8C, Nature 391 (1998) 773–775. [6] T.M. Besmann, J.C. McLaughlin, H.-T. Lin, Fabrication of ceramic composites: forced CVI, J. Nucl. Mater. 219 (1995) 31–35. [7] N. Igawa, T. Taguchi, L.L. Snead, Y. Katoh, S. Jitsukawa, A. Kohyama, J.C. McLaughlin, Optimizing the fabrication process for superior mechanical properties in the FCVI SiC matrix/stoichio￾metric SiC fiber composites system, J. Nucl. Mater. 307–311 (2002) 1205–1209. [8] T. Nozawa, K. Hironaka, Y. Katoh, A. Kohyama, T. Taguchi, S. Jitsukawa, L.L. Snead, Tensile strength of chemical vapor infiltrated advanced SiC fiber composites at elevated temperatures, Ceram. Trans. 144 (2002) 245–252. 554 N. Igawa et al. / Journal of Physics and Chemistry of Solids 66 (2005) 551–554