《复合材料 Composites》课程教学资源（学习资料）第五章 陶瓷基复合材料_SiC-SiC

Availableonlineatwww.sciencedirect.com journal吖 ScienceDirect nuclear ELSEVIER Journal of Nuclear Materials 367-370(2007)719-724 materials www.elsevier.com/locateljnucmat Efforts on large scale production of NITE-SiC/SiC composites Joon-Soo Park D,, Akira Kohyama, Tatsuya Hinoki a Kazuya Shimoda, Yi-Hyun Park Institute of Adranced Energy, Kyoto University, Gokasho to 611-0011, Japan b Institute of Energy Science and Technology Co, Ltd. Tokyo, Japan Graduate School of Energy Science, Kyoto Universit Kyoto, Japan Abstract To indicate the feasibility of utilizing newly developed NITE-SiC/SiC composite materials in a fusio on reactor the nite process with near-net shape forming has been carried out. In order to establish the large scale production of NITE-SiC/SiC, pilot grade NITE-SiC/SiC was fabricated and the baseline properties were evaluated. As the key elements, nano-powder fabrication and Tyranno-SA, SAK fabrication are extensively being developed. NITE-SiC/SiC composites of a cylindrical shape were also fabricated by a near-net shape process called pseudo-HlP, which was a new type HIP using a carbon powder as the pressure transmitter. The microstructure of NITE-SiC/SiC composites, such as fiber volume frac tion, porosity and type of pores, can be controlled precisely. This makes it possible to produce test blanket modules TBMs)or other components with proper thermal conductivity in response to the requirements of fusion reactor design C 2007 Elsevier B V. All rights reserved 1. Introduction shown no degradation of mechanical properties after irradiation to a dose of cl0 dpa [5]. These a key element of the worldwide fusion program encouraging results might enable the introduction is the development of breeding blankets for com- of SiC composites in low-risk applications in ITER mercial fusion power stations. ITER will provide TBMs. But SiC/SiC composites have not been three equatorial ports for various types of TBMs well developed commercially and require consider for the testing of tritium breeding modules. Each able additional research to investigate engineering port can accommodate two types of TBMs. Silicon feasibility [1-5]. carbide composites offer the greatest potential for Based on the improvements in reinforcing SiC very high temperature operation among the candi- fibers and other raw materials, the well-known date reduced activation fusion structural materials. liquid phase sintering(LPS) process was drastically Recent third-generation SiC/SiC composites have improved to obtain a new process called the nano infiltration and transient eutectic phase (NITE) Process. Laboratory scale NITE-SiC/SiC compos Energy,Kyoto University, Gokasho, Uji, Kyoto 611-0011. Ites demonstrated excellent mechanical properties ddress: Institute of Japan.Tel:+81774383460;fax:+81774383467 thermal conductivity, hermeticity and microstruc- E-imail address: spark(@iae. kyoto-u ac jp(J -S. Park). tural stability which made them attractive not only 0022-3115/S- see front matter 2007 Elsevier B v. All rights reserved doi:10.1016 i-jnucmat2007.03.05

Efforts on large scale production of NITE-SiC/SiC composites Joon-Soo Park a,b,*, Akira Kohyama a , Tatsuya Hinoki a , Kazuya Shimoda c , Yi-Hyun Park c a Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan b Institute of Energy Science and Technology Co., Ltd., Kanda, Tokyo, Japan c Graduate School of Energy Science, Kyoto University, Uji, Kyoto, Japan Abstract To indicate the feasibility of utilizing newly developed NITE-SiC/SiC composite materials in a fusion reactor, R&D on the NITE process with near-net shape forming has been carried out. In order to establish the large scale production of NITE-SiC/SiC, pilot grade NITE-SiC/SiC was fabricated and the baseline properties were evaluated. As the key elements, nano-powder fabrication and Tyranno-SA, SAK fabrication are extensively being developed. NITE-SiC/SiC composites of a cylindrical shape were also fabricated by a near-net shape process called pseudo-HIP, which was a new type HIP using a carbon powder as the pressure transmitter. The microstructure of NITE-SiC/SiC composites, such as fiber volume frac￾tion, porosity and type of pores, can be controlled precisely. This makes it possible to produce test blanket modules (TBMs) or other components with proper thermal conductivity in response to the requirements of fusion reactor design. 2007 Elsevier B.V. All rights reserved. 1. Introduction A key element of the worldwide fusion program is the development of breeding blankets for com￾mercial fusion power stations. ITER will provide three equatorial ports for various types of TBMs for the testing of tritium breeding modules. Each port can accommodate two types of TBMs. Silicon carbide composites offer the greatest potential for very high temperature operation among the candi￾date reduced activation fusion structural materials. Recent third-generation SiC/SiC composites have shown no degradation of mechanical properties after irradiation to a dose of 10 dpa [5]. These encouraging results might enable the introduction of SiC composites in low-risk applications in ITER TBMs. But SiC/SiC composites have not been as well developed commercially and require consider￾able additional research to investigate engineering feasibility [1–5]. Based on the improvements in reinforcing SiC fibers and other raw materials, the well-known liquid phase sintering (LPS) process was drastically improved to obtain a new process called the nano infiltration and transient eutectic phase (NITE) Process. Laboratory scale NITE-SiC/SiC compos￾ites demonstrated excellent mechanical properties, thermal conductivity, hermeticity and microstruc￾tural stability which made them attractive not only 0022-3115/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jnucmat.2007.03.053 * Corresponding author. Address: Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan. Tel.: +81 774 38 3460; fax: +81 774 38 3467. E-mail address: jspark@iae.kyoto-u.ac.jp (J.-S. Park). Journal of Nuclear Materials 367–370 (2007) 719–724 www.elsevier.com/locate/jnucmat

J-S. Park et al. /Journal of Nuclear Materials 367-370(2007)719-724 for nuclear application but also for many industrial under pressures ranging from 15 to 20 MPa. The applications [6-8 NITE-SiC/SiC matrix is composed of polycrystal c The pilot grade fabrication of the NITE SiC/Sic line SiC and a small amount of isolated oxides omposite has been conducted with various shape The details of the NITE process were introduce and sizes to adjust process conditions to meet large elsewhere [6-8] productions in quantity. To indicate the feasibility of blanket mod- ules for fusion reactors by utilizing newly developed 3. Eforts on large scale production NITE-SiC/SiC composite materials, R&D on the NITE process with near-net shape forming has been 3. 1. Continuous UD prepreg sheet forming line carried out. This paper provides results and presents the status of pilot grade NITE-SiC/SiC composites For the stable supply of high performance SiC fibers, a large scale production line for SiC fibers Moreover, newly initiated efforts for the production is being built under the strong cooperation between of porous SiC materials based on the NITE process Kyoto University and other Japanese companies, are introduced brief such as the Institute of Energy Science and Techno- logy, Co, Ltd. Ube Industries, Ltd and the Japan 2. NITE Process Ultra-high Temperature Materials Research Institute The NITE process was developed making In spite of the growing demand for pi e so-called liquid phase sintering for silicide which is a kind of fabric consisting of carbon ceramics with small amounts of oxide additives reinforcing fibers including raw materials which is one of the common production processe formation of SiC matrixes, only a limited amount for monolithic SiC. Liquid phase sintering has beer of prepregs can be supplied due to their manual applied to Sic many times in the past and has been production system and short supply of carbon found inappropriate for high performance Sic/sic coated SiC fiber. To raise the production efficiency processing. One of the reasons was the high process the establishment of the continuous unidirectional temperature required to make a dense matrix with a (UD)prepreg forming facilities including CVD fur- small amount of sintering additives, which degrades nace for carbon coating as fiber/matrix interphase fiber strength. The successful development of nIte was strongly required as well as the stable supply owes to fundamental research on surface micro- of highly qualified raw materials. Fig. I shows the chemistry of nano-sized B-SiC powder, the rheolog rough concept of continuous UD prepreg sheet ical properties of mixed slurry, optimization of forming line for large scale production. This form- ing line consists of bobbin mount, fiber desizing and emergence of the advanced SiC fibers such as furnaces, CVD furnace for carbon coating, slurry Tyranno-sA infiltration, dryer, and collecting spool. In the laboratory scale production, carbon coated Tyranno-Sa preforms were infiltrated with 3. 2. Characterization of Sic nano powder nano-sized B-Sic powder and a small amount of sin- tering aids(Al, O3, Y2O3 and Sio2)and followed by For the reduction of porosity and good sinter hot pressing at high temperatures(1750-1800C) ability in the nIte process, the handling of Sic Bobbin Mount Fumace CvD Furnace Fig. 1. Continuous UD prepreg sheet forming line for the large scale production of NITE- SiC/SiC

for nuclear application but also for many industrial applications [6–8]. The pilot grade fabrication of the NITE SiC/SiC composite has been conducted with various shapes and sizes to adjust process conditions to meet large scale productions in geometry, size, quality and quantity. To indicate the feasibility of blanket mod￾ules for fusion reactors by utilizing newly developed NITE-SiC/SiC composite materials, R&D on the NITE process with near-net shape forming has been carried out. This paper provides results and presents the status of pilot grade NITE-SiC/SiC composites. Moreover, newly initiated efforts for the production of porous SiC materials based on the NITE process are introduced briefly. 2. NITE Process The NITE process was developed making use of the so-called liquid phase sintering for silicide ceramics with small amounts of oxide additives, which is one of the common production processes for monolithic SiC. Liquid phase sintering has been applied to SiC many times in the past and has been found inappropriate for high performance SiC/SiC processing. One of the reasons was the high process temperature required to make a dense matrix with a small amount of sintering additives, which degrades fiber strength. The successful development of NITE owes to fundamental research on surface micro￾chemistry of nano-sized b-SiC powder, the rheolog￾ical properties of mixed slurry, optimization of sintering conditions, appropriate fiber protection, and emergence of the advanced SiC fibers such as Tyranno-SA. In the laboratory scale production, carbon coated Tyranno-SA preforms were infiltrated with nano-sized b-SiC powder and a small amount of sin￾tering aids (Al2O3, Y2O3 and SiO2) and followed by hot pressing at high temperatures (1750–1800 C) under pressures ranging from 15 to 20 MPa. The NITE-SiC/SiC matrix is composed of polycrystal￾line SiC and a small amount of isolated oxides. The details of the NITE process were introduced elsewhere [6–8]. 3. Efforts on large scale production 3.1. Continuous UD prepreg sheet forming line For the stable supply of high performance SiC fibers, a large scale production line for SiC fibers is being built under the strong cooperation between Kyoto University and other Japanese companies, such as the Institute of Energy Science and Techno￾logy, Co., Ltd. Ube Industries, Ltd. and the Japan Ultra-high Temperature Materials Research Institute. In spite of the growing demand for prepregs, which is a kind of fabric consisting of carbon coated reinforcing fibers including raw materials for the formation of SiC matrixes, only a limited amount of prepregs can be supplied due to their manual production system and short supply of carbon coated SiC fiber. To raise the production efficiency, the establishment of the continuous unidirectional (UD) prepreg forming facilities including CVD fur￾nace for carbon coating as fiber/matrix interphase was strongly required as well as the stable supply of highly qualified raw materials. Fig. 1 shows the rough concept of continuous UD prepreg sheet forming line for large scale production. This form￾ing line consists of bobbin mount, fiber desizing furnaces, CVD furnace for carbon coating, slurry infiltration, dryer, and collecting spool. 3.2. Characterization of SiC nano powder For the reduction of porosity and good sinter￾ability in the NITE process, the handling of SiC Fig. 1. Continuous UD prepreg sheet forming line for the large scale production of NITE-SiC/SiC. 720 J.-S. Park et al. / Journal of Nuclear Materials 367–370 (2007) 719–724

J.S. Park et al. /Journal of Nuclear Materials 367-370(2007)719-724 700600500400300200100 nano powders and process aids are emphasized as fabrics of Tyranno-Sa without fiber coating, a fully key techniques. The stable supply of Sic nano pow- dense composite without any detectable crack ders with precise characterization and strict quality under optical and SEM observation was success- control is also an important issue. It was well fully produced. known that the surface of Sic powder is covered To improve the workability for fabrication at the by silicon oxide, silicon oxycarbide or free carbon, Ube process line, the amount of process additive nd strongly affected by fabrication/preservation was increased for pilot grade#2. Furthermore, in the case of the pilot grade #3 fabrication a new X-ray photoelectron spectroscopy is one of the Tyranno fiber was applied. The tentative name of nost powerful methods for the investigation of the fiber is Tyranno-SAK(the new version of SA powder surface chemistry. Fig. 2 shows the XPs for Kyoto University) where 800 fibers make or petra of Sic nano powders which were examined fiber bundle for improving inter-bundle matrix for the production of laboratory scale NITE-SiC/ formation and improving weavability for textile SiC composites. As an example, N3 SiC powder fabrication. Although a fiber /matrix interphase, has the highest OIs peak compared to that of other CVD-carbon is mainly necessary to protect the rein- Sic powders. This means that a large amount of forcing fiber during sintering and it increases the oxygen exists on the surface of N3 Sic powder in toughness of composites, fiber filaments stick the form of Sioz or Sio, Cy. Although, SiO2 assists together and a tangle of fiber filaments can be an the formation of a liquid phase at lower tempera- obstacle to intra-bundle matrix formation In addi- tures, it is well known as the main vitrifying tion, PyC coating thickness and the rheological component [9]. Sic nano powder with appropriate characteristics of mixed slurry were also adjusted properties for nITE process was selected through to promote the permeability of mixed slurry into a close inspections by XPS, FT-IR and XRD fiber bundle. As a result, density and the deforma tion of fibers during processing and mechanical 3.3. Pilot grade products, characteristics and properties have been improved. Fig 3 summarizes specific features of products comparing laboratory grade, pilot grades #l to #3 The first trial to make pilot grade Nite was As shown in Fig 3, pilot grade #l was insuffi- done in 2002 based on the optimized condition for cient in density, tensile strength and elastic modulus laboratory scale fabrication. For the case of ud The only exception was for the case of the no fiber reinforcement with a PyC interface, it was difficult coating product where density was near full-dense to make the inter-bundle matrix and the result was and elastic modulus was quite high. From pilot not satisfactory from a density and mechanical grades #2 to #3, all characteristics were improved property point of view. For the case of plain woven and the results for UD NITE-SiC/SiC utilizing

nano powders and process aids are emphasized as key techniques. The stable supply of SiC nano pow￾ders with precise characterization and strict quality control is also an important issue. It was well known that the surface of SiC powder is covered by silicon oxide, silicon oxycarbide or free carbon, and strongly affected by fabrication/preservation condition. X-ray photoelectron spectroscopy is one of the most powerful methods for the investigation of powder surface chemistry. Fig. 2 shows the XPS spectra of SiC nano powders which were examined for the production of laboratory scale NITE-SiC/ SiC composites. As an example, N3 SiC powder has the highest O1s peak compared to that of other SiC powders. This means that a large amount of oxygen exists on the surface of N3 SiC powder in the form of SiO2 or SiOxCy. Although, SiO2 assists the formation of a liquid phase at lower tempera￾tures, it is well known as the main vitrifying component [9]. SiC nano powder with appropriate properties for NITE process was selected through close inspections by XPS, FT-IR and XRD. 3.3. Pilot grade products, characteristics and performance The first trial to make pilot grade NITE was done in 2002 based on the optimized condition for laboratory scale fabrication. For the case of UD reinforcement with a PyC interface, it was difficult to make the inter-bundle matrix and the result was not satisfactory from a density and mechanical property point of view. For the case of plain woven fabrics of Tyranno-SA without fiber coating, a fully dense composite without any detectable cracks under optical and SEM observation was success￾fully produced. To improve the workability for fabrication at the Ube process line, the amount of process additive was increased for pilot grade #2. Furthermore, in the case of the pilot grade #3 fabrication a new Tyranno fiber was applied. The tentative name of the fiber is Tyranno-SAK (the new version of SA for Kyoto University) where 800 fibers make one fiber bundle for improving inter-bundle matrix formation and improving weavability for textile fabrication. Although a fiber/matrix interphase, CVD-carbon is mainly necessary to protect the rein￾forcing fiber during sintering and it increases the toughness of composites, fiber filaments stick together and a tangle of fiber filaments can be an obstacle to intra-bundle matrix formation. In addi￾tion, PyC coating thickness and the rheological characteristics of mixed slurry were also adjusted to promote the permeability of mixed slurry into a fiber bundle. As a result, density and the deforma￾tion of fibers during processing and mechanical properties have been improved. Fig. 3 summarizes specific features of products comparing laboratory grade, pilot grades #1 to #3. As shown in Fig. 3, pilot grade #1 was insuffi- cient in density, tensile strength and elastic modulus. The only exception was for the case of the no fiber coating product where density was near full-dense and elastic modulus was quite high. From pilot grades #2 to #3, all characteristics were improved and the results for UD NITE-SiC/SiC utilizing Fig. 2. XPS spectra of SiC nano powders. J.-S. Park et al. / Journal of Nuclear Materials 367–370 (2007) 719–724 721

J-S. Park et al. /Journal of Nuclear Materials 367-370(2007)719-724 500 Elastic modulus· Relative density100 Scale b三 TEnsile strength 这 245 Tensile strai Lab. PG#I PG#1 PG#1 PG#2 PG#3 70 PC. toting Fig. 3. Characteristics of NITE-SiC/SiC composites. Tyranno-SAK with PyC interface became very sim- out. These results indicate the insufficient interfac ilar to the laboratory grade material. But the stress- formation for the case of pilot grade #3 strain curves on the left side graph in Fig. 3 indicate a big difference in those two materials. The labora 3.4. Near-net shaping tory scale product shows a large elongation(fibe pull out) after reaching the proportional limit stress, The fabrication process for cylindrical whereas the pilot grade #3 sample(denoted as NITE-SiC/Sic composites is schematically PG#3PCUD) showed a relatively small fiber pull in Fig 4. The cut UD prepreg sheets were C mold essure transmitter Carbon powder C/C mold Stacked UD b C/C mold Mold Stacked UD prepreg sheets Fig. 4. Fabrication process of cylindrically shaped NITE-SiC/SiC composites (a)010 mm x 50 mm pipe (b)0200 mm x 80 mm tube

Tyranno-SAK with PyC interface became very sim￾ilar to the laboratory grade material. But the stress– strain curves on the left side graph in Fig. 3 indicate a big difference in those two materials. The labora￾tory scale product shows a large elongation (fiber pull out) after reaching the proportional limit stress, whereas the pilot grade #3 sample (denoted as PG#3PCUD) showed a relatively small fiber pull out. These results indicate the insufficient interface formation for the case of pilot grade #3. 3.4. Near-net shaping The fabrication process for cylindrical shaped NITE-SiC/SiC composites is schematically shown in Fig. 4. The cut UD prepreg sheets were stacked 0 0.1 0.2 0.3 0.4 Tensile strain [%] 0 100 200 300 400 Tensile stress [MPa] 0 100 200 300 400 500 70 80 90 100 Tensile strength [MPa] Relative density [%] PG#1NCPW PG#1PCUX-1 PG#1PCUX-2 PG#2PCUD Lab. Scale PG#3PCUD Lab. Scale PG#1 NCPW PG#1 PCUX -1 PG#1 PCUX -2 PG#2 PCUD PG#3 PCUD NOTICE: NC-without coating PC - Pyro carbon UD-Unidirectional UX-Cross ply (0º/90º) PW-Plain woven Elastic modulus Tensile strength a b Relative density Fig. 3. Characteristics of NITE-SiC/SiC composites. Fig. 4. Fabrication process of cylindrically shaped NITE-SiC/SiC composites. (a) B10 mm · 50 mm pipe. (b) B200 mm · 80 mm tube. 722 J.-S. Park et al. / Journal of Nuclear Materials 367–370 (2007) 719–724

J.S. Park et al. Journal of Nuclear Materials 367-370(2007)719-724 Through hickness channe thickness chand OM Image Heterogeneous region 1mm Size of pores or through-thickness channel Fig. 5. Porous SiC materials with various types and sizes of pores manufactured by the NITE Process. on the graphite mold. Then the preform was densi- by the selection of precursors with appropriate sizes fied by the pseudo-HIP process, which was a new and shapes. The slight problem of heterogeneous type HIP using a carbon powder as the pressure microstructure around through-thickness channels transmitter and a carbon mold with a near-net remains. Further r&d is ongoing to obtain a more shape cavity. In this process, pressure was applied robust and sound NITe matrix to the upper graphite die the same as hot pressing however, the pressure was transmitted through the 4. Conclusions carbon powder filled in the mold. For the smal diameter cylindrical shape, pressure was designed Pilot grade production of NITE-SiC/SiC com- to be transmitted from the outside to the inside as osites has been extensively conducted in recent shown in Fig 4(a). For the large diameter cylindri- years and much progress towards industrialization cal shape, pressure was designed to be transmitted and commercialization has been accomplished from the inside to the outside as shown in Fig. 4(b). Although many crucial needs remain for the appli cation to advanced energy systems, the results up 3.5 Porous Sic materials to now are quite encouraging and the efforts to tiate mass production of SiC nano powders and Porous SiC materials and SiC/SiC composites Tyranno SAK fibers for NITE are rapidly maturing are considered as the partition and perforated con- Development of porous SiC materials based on the NitE process is also ongoing with high potential material for the coated particle fuel compartment and attractiveness for a horizontal flow cooling concept with direct cooling system for the gas cooled fast reactor Acknowledgment GFR). SiC and SiC/SiC with through thickness channels should maintain a high thermal conducti and high helium leakage rate This work is supported by the Innovative Nucle ar Energy Technology Program under the Ministry Based on the NITE process, new trial efforts for of Education, Sports, Culture, Science and Techno- the production of Sic ceramic materials with open logy(MEXT), japan pores and through thickness channels have been ini tiated. Due to the high degree of freedom in the References NITE process, various types and sizes of pore can be formed in a robust SiC matrix as shown in Fig. 5. [U Vladimir Barabash, J Nucl. Mater. 329-333(2004)156 These NITE-SiC matrices with various sizes of [2]SJ. Zinkle, M.Victoria,K.Abe,JNucl. Mater.307-311 pores were achieved in different ways, like simple(2002)31 hot pressing with different contents of precursors, 3]T. Muroga, M. Gasparotto, S.J. Zinkle, Fusion Eng. Des. and the decarburization of precursors in a SiC [4 R.H. Jones, L. Giancarli, A. Hasegawa, Y. Katoh, A matrix. This means that the sizes and shapes of Kohyama, B. Riccardi, LL. Snead, w.J. Weber, J. Nucl. pores or channels in Sic matrix can be controlled

on the graphite mold. Then the preform was densi- fied by the pseudo-HIP process, which was a new type HIP using a carbon powder as the pressure transmitter and a carbon mold with a near-net shape cavity. In this process, pressure was applied to the upper graphite die the same as hot pressing; however, the pressure was transmitted through the carbon powder filled in the mold. For the small diameter cylindrical shape, pressure was designed to be transmitted from the outside to the inside as shown in Fig. 4(a). For the large diameter cylindri￾cal shape, pressure was designed to be transmitted from the inside to the outside as shown in Fig. 4(b). 3.5. Porous SiC materials Porous SiC materials and SiC/SiC composites are considered as the partition and perforated con￾tainment wall for a blanket module and structural material for the coated particle fuel compartment for a horizontal flow cooling concept with direct cooling system for the gas cooled fast reactor (GFR). SiC and SiC/SiC with through thickness channels should maintain a high thermal conductiv￾ity and high helium leakage rate. Based on the NITE process, new trial efforts for the production of SiC ceramic materials with open pores and through thickness channels have been ini￾tiated. Due to the high degree of freedom in the NITE process, various types and sizes of pore can be formed in a robust SiC matrix as shown in Fig. 5. These NITE-SiC matrices with various sizes of pores were achieved in different ways, like simple hot pressing with different contents of precursors, and the decarburization of precursors in a SiC matrix. This means that the sizes and shapes of pores or channels in SiC matrix can be controlled by the selection of precursors with appropriate sizes and shapes. The slight problem of heterogeneous microstructure around through-thickness channels remains. Further R&D is ongoing to obtain a more robust and sound NITE matrix. 4. Conclusions Pilot grade production of NITE-SiC/SiC com￾posites has been extensively conducted in recent years and much progress towards industrialization and commercialization has been accomplished. Although many crucial needs remain for the appli￾cation to advanced energy systems, the results up to now are quite encouraging and the efforts to ini￾tiate mass production of SiC nano powders and Tyranno SAK fibers for NITE are rapidly maturing. Development of porous SiC materials based on the NITE process is also ongoing with high potential and attractiveness. Acknowledgment This work is supported by the Innovative Nucle￾ar Energy Technology Program under the Ministry of Education, Sports, Culture, Science and Techno￾logy (MEXT), Japan. References [1] Vladimir Barabash, J. Nucl. Mater. 329–333 (2004) 156. [2] S.J. Zinkle, M. Victoria, K. Abe, J. Nucl. Mater. 307–311 (2002) 31. [3] T. Muroga, M. Gasparotto, S.J. Zinkle, Fusion Eng. Des. 61&62 (2002) 13. [4] R.H. Jones, L. Giancarli, A. Hasegawa, Y. Katoh, A. Kohyama, B. Riccardi, L.L. Snead, W.J. Weber, J. Nucl. Mater. 307–311 (2002) 1057. Fig. 5. Porous SiC materials with various types and sizes of pores manufactured by the NITE Process. J.-S. Park et al. / Journal of Nuclear Materials 367–370 (2007) 719–724 723

J-S. Park et al. /Journal of Nuclear Materials 367-370(2007)719-724 5]T. Hinoki, L L. Snead, Y. Katoh, A. Kohyama, J. Nucl [8]S. Dong, Y. Katoh, A. Kohyama, J. Eur. Ceram Soc. 2 Mater.307-311(2002)1157 (2003)1223 [6]A Kohyama, S Dong, Y Katoh, Ceram. Eng. Sci. Proc. 23 [9]P B Noakes, P.K. Pratt, in: P. Popper(Ed ) Special Ceramics (3)(2002)31l 5. British Ceramic Research Association. Stoke-on-Trent [7Y. Katoh, S.M. Dong, A Kohyama, Fusion Eng Des 61&62 972,p.299 (2002)723

[5] T. Hinoki, L.L. Snead, Y. Katoh, A. Kohyama, J. Nucl. Mater. 307–311 (2002) 1157. [6] A. Kohyama, S. Dong, Y. Katoh, Ceram. Eng. Sci. Proc. 23 (3) (2002) 311. [7] Y. Katoh, S.M. Dong, A. Kohyama, Fusion Eng. Des. 61&62 (2002) 723. [8] S. Dong, Y. Katoh, A. Kohyama, J. Eur. Ceram. Soc. 23 (2003) 1223. [9] P.B. Noakes, P.K. Pratt, in: P. Popper (Ed.), Special Ceramics 5, British Ceramic Research Association, Stoke-on-Trent, 1972, p. 299. 724 J.-S. Park et al. / Journal of Nuclear Materials 367–370 (2007) 719–724