TEM-EELS analysis reveals the W-atom mediated radiation-induced amorphization in M23C6
Sho Kano, Huilong Yang, Masami Ando, Dai Hamaguchi, Takashi Nozawa, Hiroyasu Tanigawa, Kenta Yoshida, Tamaki Shibayama, Hiroaki Abe
Journal of Nuclear Materials, 603, 2025年01月
研究論文（学術雑誌）, To gain a mechanistic understanding of the phase stability of M23C6 upon irradiation, the bulk W-doped M23C6 (Cr-W-C system) in the range of 0–12 at.% W concentration was prepared and subjected to helium beam irradiation, following with a thorough electron energy loss spectroscopy (EELS) analysis. Radiation-induced amorphization (RIA) was observed only at the 4 W sample with a W concentration of ∼12 at.%. Analysis of the low-loss spectrum showed that the inelastic mean free path (λ) could be applied an effective indicator of the presence of an amorphous phase. The white line ratio of the carbon K-edge spectrum showed that the chemical bonding state in the crystalline state is mainly 2p3/2 bonding, and it changes to dominantly 2p1/2 bonding accompanying with the crystal-to-amorphous (c-a) transition. Discussion on the relationship between the change in λ (Δλ) and the lattice parameter (Δa) due to irradiation reveals that Δa is not dependent on Δλ, indicating that Δλ is mainly caused by the volume expansion due to the c-a transition. In addition, a crystalline state is remained even after a lattice parameter change of ∼1.5 % in 0 W and 1W-samples, whereas, a lattice expansion of ∼0.2 % would trigger the occurrence of crystal-to-amorphous transition in the 4W-sample. The detailed EELS analysis demonstrated that the constitutional W atoms play an important role in facilitating the occurrence of RIA in M23C6, that is, the phase instability accompanying the lattice expansion due to irradiation was emphasized by the addition of W in M23C6. The insights obtained here suggest that a higher W concentration in M23C6 is more susceptible to RIA, and therefore the resistance to amorphization is achievable by decreasing the W concentration in the steels.

Ultraviolet Light-Induced Surface Changes of Tungsten Oxide in Air: Combined Scanning Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy Analysis
Yuki Nakagawa, Yasuhiro Shiratsuchi, Tamaki Shibayama, Masaki Takeguchi
Nanomaterials, 14, 1486, 2024年09月13日, ［査読有り］
研究論文（学術雑誌）

W-concentration dependent radiation-induced amorphization in M23C6 via atomic-scale analysis by Voronoi tessellation
Sho Kano, Huilong Yang, Masami Ando, Dai Hamaguchi, Takashi Nozawa, Hiroyasu Tanigawa, Tamaki Shibayama, Hiroaki Abe
Materialia, 36, 2024年08月
研究論文（学術雑誌）, Voronoi tessellation was innovatively applied to interpret the high-resolution atomic-scale micrographs of the Cr-W-C ternary M23C6 with and without irradiation to provide mechanistic insight into the phase stability under irradiation. A W concentration-dependent radiation-induced amorphization behavior was observed and the amorphization was confirmed in the 4 W sample (∼12 at.%W). Analysis of the local crystal structure using Voronoi diagrams shows that the average size of each Voronoi cell and its standard deviation are affected by irradiation and W concentration. In addition, the standard deviation of the Voronoi cell size, which is considered an indicator of the uncertainty of the atomic column positions, is also plotted as a function of the lattice parameter change. This mathematical analysis indicates that a higher W concentration tends to cause a more severe disordering of the atomic distribution upon irradiation, which is directly correlated with the occurrence of amorphization.

Transmission electron microscopy study of the radiation-induced amorphization in the Cr-W-C ternary M23C6
Sho Kano, Huilong Yang, Masami Ando, Dai Hamaguchi, Takashi Nozawa, Hiroyasu Tanigawa, Tamaki Shibayama, Hiroaki Abe
Journal of Nuclear Materials, 594, 2024年06月
研究論文（学術雑誌）, To provide mechanistic insight into the phase stability of M23C6 under irradiation, bulk M23C6 (Cr-W-C system) specimens with a W concentration range of 0–12 at.% were first subjected to helium ion irradiation and then investigated by systematic TEM/STEM observation. The atomic resolution electron microscopy analysis revealed that the preferential occupation site of the W atom is the 8c site, and the 48 h site is also occupied when the W concentration is >7 at.%. The atomic arrangement of the M23C6 particle in F82H steel is similar to that of the specimen of 1 W (3 at.% W), and the chemical formula of the M23C6 particle in F82H steel is described as Cr13Fe9W1C6. Radiation-induced amorphization was strongly related to the W concentration in the bulk M23C6, and amorphization was observed only at W concentrations of ∼12 at.% under the present irradiation condition. Line analysis of HAADF and its FFT images confirmed the chemical disordering associated with W atoms, which appears to increase with increasing W concentration. Based on these results, the mechanism of radiation-induced amorphization appears to be different between bulk M23C6 and the M23C6 particles. Specifically, the amorphization of bulk M23C6 is mainly influenced by the addition of a high concentration of W, while the synergistic effects of elements including Cr, Fe, and W are attributed to RIA in fine M23C6 particles. Moreover, the energetic change associated with the W/Fe atom exchange in the M23C6 system is estimated to explain the occurrence of chemical disordering and its resultant amorphization behavior, which provides a new viewpoint to achieve a deeper understanding of the mechanisms behind radiation-induced amorphization. Secondary abstract: The chemical composition of M23C6 particles in F82H steel and the hypothesis of its radiation-induced amorphization mechanism was proposed by HREM observation of He-irradiated M23C6 ingots.

Antioxidation effect of coatings prepared by helium-ion implantation of copper surfaces
Subing Yang, Yuki Nakagawa, Tamaki Shibayama
Vacuum, 220, 112864, 2024年02月, ［査読有り］
研究論文（学術雑誌）

Catalytic ammonia synthesis on HY-zeolite-supported angstrom-size molybdenum cluster
Satoshi Kamiguchi, Kiyotaka Asakura, Tamaki Shibayama, Tomoko Yokaichiya, Tatsushi Ikeda, Akira Nakayama, Ken-ichi Shimizu, Zhaomin Hou
Chemical Science, Royal Society of Chemistry (RSC), 2024年
研究論文（学術雑誌）, A molybdenum halide cluster complex is converted to an angstrom-size metal cluster on HY zeolite. The cluster efficiently catalyzes ammonia synthesis owing to high N₂ activation ability brought by cooperation of the multiple molybdenum sites.

Chemical and topological disordering in M23C6 due to irradiation: An atomic-scale observation
Sho Kano, Huilong Yang, Masami Ando, Dai Hamaguchi, Takashi Nozawa, Hiroyasu Tanigawa, Tamaki Shibayama, Hiroaki Abe
Journal of Nuclear Materials, 587, 2023年12月15日
研究論文（学術雑誌）, To clarify the stability of M23C6 precipitate in steels under irradiation, the chemical and topological disordering behaviors in M23C6 subjected to ion irradiation at elevated temperatures were investigated with the combined application of high-resolution electron microscopy (HREM) and electron energy-loss spectroscopy (EELS). Results show that the duplex structured M23C6 which is the core-crystalline and shell-amorphous was observed in the specimen irradiated at 623 K, nevertheless, no amorphous phase was observed in the specimen irradiated at 673 K. HREM observation confirmed the occurrence of the chemical disordering in irradiated M23C6, and the disordering of W atoms in the M23C6 unit cell was clarified by the peak intensity profile of the atomic column from the HREM image. EELS analyses indicate that no obvious chemical shift was observed by the core-loss spectrum, however, the change in the electron mean free path (λ) due to irradiation was confirmed by the low-loss spectrum, which is related to the formation of both irradiation defects and amorphous phase. It is proposed that the decreased material density upon irradiation is ascribed to the formation of W-vacancy-dominated defect clusters. An obvious change in interatomic distance was not observed in the irradiated M23C6 based on the radical distribution function analysis by extended energy-loss fine structure spectrum. However, the peak intensity decreased by irradiation, confirming the occurrence of chemical and topological disordering, regardless of the carbide being crystalline or amorphous.

Radiation-induced amorphization behavior of thermally-aged M₂₃C₆ in F82H-BA12 steel
Sho Kano, Huilong Yang, Reuben Holmes, Masami Ando, Dai Hamaguchi, Takashi Nozawa, Tamaki Shibayama, Hiroaki Abe
JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY, 60, 10, 1244, 1257, TAYLOR & FRANCIS LTD, 2023年10月, ［査読有り］
英語, 研究論文（学術雑誌）, To improve the understanding of the microstructural stability of F82H under fusion reactor environments, the synergistic effects of irradiation and thermal aging on the instability of M23C6 particle was investigated utilizing ion accelerator irradiation. Results show that the W-rich Laves phase growing along the grain boundaries was observed in the specimen after thermal aging at 773 K up to 10,000 hr. A bilayer contrast of the M23C6 particles consisting of an amorphous-rim and inner crystalline core was observed in the specimen irradiated by 10.5 MeV-Fe3+ at 623 K, but not in the specimen irradiated at 673 K, demonstrating that the critical temperature of the radiation-induced amorphization (RIA) in thermally aged M23C6 particles falls in the range of 623-673 K. These results show that thermal aging seems to play an insignificant role in the RIA behavior of M23C6 particles. Regarding the radial distribution function analysis, a relatively poor crystallinity was observed in the unirradiated thermally aged M23C6 particles, while the crystallinity was improved in the specimen irradiated at 673 K, which is ascribed to enhanced diffusion at elevated temperatures. Results indicate that the temperature-dependent point defect generation and recovery is the key factor related to the occurrence of RIA in M23C6 particles.

Enhanced Li-ion conductivity in LiBH₄–ZrO₂ nanocomposites and nanoscale Li imaging by energy-filtered transmission electron microscopy
Yuki Nakagawa, Tsubasa Sendo, Tamaki Shibayama
Chemical Communications, 59, 73, 10912, 10915, Royal Society of Chemistry (RSC), 2023年, ［査読有り］, ［最終著者］
研究論文（学術雑誌）, The nanostructure of LiBH₄–ZrO₂ composites has been studied by the complementary analysis of Li-ion dynamics, chemical bonding states, and distribution on the nanoscale.

Effects of gas phase ion irradiation and vacuum annealing on the visible light photocatalytic properties of WO3
Yuki Nakagawa, Yuya Hayashi, Subing Yang, Tamaki Shibayama
Vacuum, 206, 111519, 2022年09月, ［査読有り］, ［最終著者］
研究論文（学術雑誌）

Highly flexible, mechanically strengthened metallic glass-based composite electrode with enhanced capacitance and cyclic stability
Yi Xu, Pak Man Yiu, Yu-Kun Wang, Xiao-Meng Qin, Tamaki Shibayama, Seiichi Watanabe, Masato Ohnuma, Da-Zhu Chen, Hua Cheng, Chan-Hung Shek, Zhou-Guang Lu, Chen Liu
Rare Metals, Springer Science and Business Media LLC, 2022年08月16日, ［査読有り］, ［国際共著］, ［国際誌］
研究論文（学術雑誌）

Tailored copper oxidation in alkaline aqueous solution after helium cation implantation
Subing Yang, Yuki Nakagawa, Tamaki Shibayama
Applied Surface Science, 591, 153087, 153087, Elsevier BV, 2022年07月, ［査読有り］, ［最終著者, 責任著者］
研究論文（学術雑誌）

An investigation of surface contamination introduced during He+ implantation and subsequent effects on the thermal oxidation of Cu
Subing Yang, Yuki Nakagawa, Tamaki Shibayama
Applied Surface Science, 579, 152163, 152163, Elsevier BV, 2022年03月, ［査読有り］, ［最終著者, 責任著者］
研究論文（学術雑誌）

Photo- & radio-chromic iron-doped tungstic acids fabricated via submerged photosynthesis
Shuntaro Murakami, Lihua Zhang, Melbert Jeem, Kazumasa Okamoto, Yuki Nakagawa, Tamaki Shibayama, Masato Ohnuma, Seiichi Watanabe
Optical Materials, 124, 111966, 111966, Elsevier BV, 2022年02月, ［査読有り］
研究論文（学術雑誌）

Room-Temperature Hydrogen Absorption of Ti with Robust Surface Coated by Hexagonal Boron Nitride
Keita Shinzato, Yuki Nakagawa, Subing Yang, Shigehito Isobe, Tamaki Shibayama, Hiroki Miyaoka, Takayuki Ichikawa
ACS Applied Energy Materials, 5, 1, 951, 957, American Chemical Society (ACS), 2022年01月24日, ［査読有り］
研究論文（学術雑誌）

Radiation-induced amorphization of M23C6 in F82H steel: An atomic-scale observation
Sho Kano, Huilong Yang, John McGrady, Yoshiyuki Watanabe, Masami Ando, Dai Hamaguchi, Takashi Nozawa, Hiroyasu Tanigawa, Kenta Yoshida, Tamaki Shibayama, Hiroaki Abe
Journal of Nuclear Materials, 558, 2022年01月, ［査読有り］
研究論文（学術雑誌）, The purpose of the present study is to clarify the instability behavior of M23C6 under irradiation, specifically the occurrence of radiation-induced amorphization (RIA). Ion irradiation of 10.5 MeV-Fe3+ at elevated temperatures from 573 to 623 K was conducted into the reduced activation ferritic/martensitic steels (F82H) and its model alloy (Fe-8Cr-0.1C). A bilayer contrast of the particle consisting of an amorphous-rim phase and inner crystalline core of M23C6 was observed in the irradiated F82H specimen, but not in the model alloy. From the high-resolution electron microscope observation, the preferential occupation site of W into M23C6 lattice was identified as 8c-site prior to irradiation in F82H specimen, which shifted to other sites due to chemical disordering upon irradiation. Evaluation of the intensity ratio between 8c and another site of M23C6, 8c/4a, then revealed that the extent of chemical disordering of W was mitigated at the amorphous-crystal interface region in comparison with the central of the particle. The hypothesis for the formation mechanism of an amorphous-rim in M23C6 was presumed as the deviation from the stoichiometric composition at the local interface due to the irradiation-enhanced diffusion and/or ballistic mixing under the current circumstances, although the efforts from experimental and/or simulation studies are still necessary to achieve a further understanding of the RIA behavior in M23C6.

Effect of mechanical milling on lithium-ion conductivity of LiAlH4
Yuki Nakagawa, Tomoharu Kimura, Takao Ohki, Shigehito Isobe, Tamaki Shibayama
SOLID STATE IONICS, 365, ELSEVIER, 2021年07月, ［査読有り］, ［最終著者］, ［国際誌］
英語, 研究論文（学術雑誌）, The effect of mechanical milling on the lithium-ion conductivity of lithium alanate (LiAlH4) is investigated. Although pristine LiAlH4 is a poor ion conductor in its highly crystalline state, short-time mechanical milling for 0.1-2 h is shown to significantly improve the conductivity. Hand-milling treatment in an argon-filled glove box is also shown to improve the conductivity. The activation energy (E-a) for ion conduction of milled LiAlH4 is similar to 0.70 eV, which is attributed to Li-ion site vacancy-mediated conduction. However, the Ea of pristine LiAlH4 shows a large value of 0.84 eV. The Li-7, Li-6, Al-27 nuclear magnetic resonance and infrared spectra suggest that surface Li hydroxide species would exhibit Li-ion conduction in pristine LiAlH4. Thus, the milling treatment can eliminate the effect of surface hydroxide species and increase the vacancy concentration at the Li-ion site of inner LiAlH4 grains, which results in the enhancement of the conductivity.

Anisotropic defect distribution in He+-irradiated 4H-SiC: Effect of stress on defect distribution
Subing Yang, Yuki Nakagawa, Minako Kondo, Tamaki Shibayama
ACTA MATERIALIA, 211, PERGAMON-ELSEVIER SCIENCE LTD, 2021年06月, ［査読有り］, ［最終著者, 責任著者］, ［国際誌］
英語, 研究論文（学術雑誌）, Irradiation-induced anisotropic swelling in hexagonal alpha-SiC is known to degrade the mechanical properties of SiC; however, the associated physical mechanism and microstructural process remain insufficiently understood. In this study, an anisotropic swelling condition where the surface normal direction was allowed to freely expand with constraint in the lateral direction was introduced in 4H-SiC using selected-area He+ irradiation, and the internal defect distribution was investigated using transmission electron microscopy (TEM) and advanced scanning TEM. The defect distribution was compared to that in non-selected-area He+-irradiated 4H-SiC and electron-irradiated TEM-foil 4H-SiC. An anisotropic defect distribution was observed in the selected-area He+-ion-irradiated 4H-SiC, with interstitial defects preferentially redistributed in the surface normal direction ([0 004]) and negative volume defects (such as vacancies and/or carbon antisite defects) dominantly located in the lateral directions ([11 (2) over bar0] and [10 (1) over bar0]). This anisotropy of the defect distribution was substantially lower in the non-selected-area He+-irradiated and electron-irradiated samples. The stress condition in the three samples was also measured and analyzed. In the selected-area He+-irradiated 4H-SiC, compressive stress was introduced in the lateral directions (([10 (1) over bar0] and [11 (2) over bar0])), with little stress introduced in the surface normal direction ([0 004]); this stress condition was introduced at the beginning of ion irradiation. The compressive stress likely inhibits the formation of interstitial defects in the lateral directions, enhancing the anisotropy of the defect distribution in SiC. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Surface modification effects of graphite for selective hydrogen absorption by titanium at room temperature
Keita Shinzato, Yuki Nakagawa, So Hamamoto, Yuya Hayashi, Hiroki Miyaoka, Shigehito Isobe, Tamaki Shibayama, Norio Ogita, Takayuki Ichikawa
Chemical Communications, 56, 53, 7237, 7240, Royal Society of Chemistry (RSC), 2020年05月, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）,

Surface modification effects of graphite and organic solvents on Ti were investigated by thermogravimetry (TG), Raman spectroscopy, and transmission electron microscopy (TEM) observations to improve its hydrogen absorption properties.

Effects of Defective Boron Nitride Additives on Lithium-Ion Conductivity and Hydrogen-Desorption Properties of LiAlH4
Yuki Nakagawa, Tomoharu Kimura, Shigehito Isobe, Tamaki Shibayama
The Journal of Physical Chemistry C, 124, 19, 10398, 10407, American Chemical Society ({ACS}), 2020年05月, ［査読有り］, ［最終著者］, ［国際誌］
英語, 研究論文（学術雑誌）

Electron energy-loss spectroscopic evaluation of depth-dependent swelling of He+ ion-irradiated 4H-SiC correlated with defect type
Subing Yang, Yuki Nakagawa, Minako Kondo, Tamaki Shibayama
Journal of Applied Physics, 127, 175106, 2020年05月, ［査読有り］, ［責任著者］, ［国際誌］
英語, 研究論文（学術雑誌）

Development of Laser-HVEM and Its Application on In-situ Observation on Lattice Defects Behavior
Yang Zhan-Bing, Yang Su-Bing, Qu Xiao-Jian, Tamaki Shibayama, Seiichi Watanabe
CHINESE JOURNAL OF STRUCTURAL CHEMISTRY, 39, 4, 623, 629, CHINESE JOURNAL STRUCTURAL CHEMISTRY, 2020年04月, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）, A nanosecond pulse laser source head (Nd:YAG laser, Inlite II-20, Continuum) was equipped to a high-voltage electron microscope (HVEM, Hitachi, H-1300) to develop a laser-HVEM system at Hokkaido University. Using the laser-HVEM, new methods for in-situ observation on the formation process of laser-induced lattice point defects at the internal of crystalline solid are achieved; some striking phenomena and potential mechanisms are explored. In the present paper, we review our progresses on in-situ experiments of lattice defects behavior in metal using the laser-HVEM. These progresses are expected to provide insight for a broader application of laser-HVEM in scientific research.

Non-destructive evaluation of the strain distribution in selected-area He+ ion irradiated 4H-SiC
Yang Subing, Tokunaga Sakiko, Kondo Minako, Nakagawa Yuki, Shibayama Tamaki
APPLIED SURFACE SCIENCE, 500, 2020年01月15日, ［査読有り］, ［最終著者, 責任著者］, ［国際誌］

先進ナノ構造・状態解析共用拠点（北海道大学）　　　　　　　　　　　　　　　
柴山 環樹, 松尾 保孝, Agus Subagyo, 坂口 紀史, 渡辺 精一
まてりあ, 58, 12, 758, 762, 2019年12月, ［査読有り］, ［招待有り］, ［筆頭著者, 責任著者］, ［国内誌］
日本語, 研究論文（学術雑誌）

In vitro and in vivo anti-herpes simplex virus activity of monogalactosyl diacylglyceride from Coccomyxa sp. KJ (IPOD FERM BP-22254), a green microalga
Hayashi Kyoko, Lee Jung-Bum, Atsumi Kinya, Kanazashi Mana, Shibayama Tamaki, Okamoto Kazumasa, Kawahara Toshio, Hayashi Toshimitsu
PLOS ONE, 14, 7, 2019年07月16日, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）, © 2019 Hayashi et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. A monogalactosyl diacylglyceride (MGDG) was isolated as an antiviral component from Coccomyxa sp. KJ (IPOD FERM BP-22254) via bioassay-guided fractionation. α-Linolenic acid (C18:3) and 7,10,13-hexadecatrienoic acid (C16:3) accounted for approximately 72% and 23%, respectively, of the MGDG total fatty acids of the MGDG. The MGDG showed virucidal activity against herpes simplex virus type 2 (HSV-2), a pathogen that causes genital herpes. Physical changes in HSV-2 shape were observed after treatment with MGDG, including a decrease in particle size, and possible damage to the viral envelope, as assessed using electron microscopy. In accordance with the morphological findings, virus particles lost their ability to bind to host cells. HSV-2 treated with high concentrations of MGDG resulted in no pathogenicity in an animal model, indicating that MGDG exhibits irreversible virucidal activity against HSV-2 particles. In the animal model of HSV-2-induced genital herpes, intravaginally administered MGDG exerted a prophylactic effect by suppressing viral yields in the genital cavity and formation of herpetic lesions, resulting in a higher survival rate in treated mice than control mice administered solvent. Thus, MGDG offers a novel prophylactic option against HSV infections.

Effects of Helium Implantation and Subsequent Electron Irradiation on Microstructures of Fe-11 wt.% Cr Model Alloy
Bing-Sheng Li, Zhi-Guang Wang, Tie-Long Shen, Kong-Fang Wei, Yan-Bin Sheng, Tamakai Shibayama, Xi-Rui Lu, An-Li Xiong
Chinese Physics Letters, 36, 4, 046104, 046104, IOP Publishing, 2019年04月, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）

In-situ visualizing atomic structural evolution during crystallization in ternary Zr-Cu-Al bulk metallic glasses
Wei Xiaoya, Lan Si, Wu Zhenduo, Ohnuma Masato, Shibayama Tamaki, Watanabe Seiichi, Zhou Jie, Lu Zhaoping, Ren Yang, Wang Xun-Li
INTERMETALLICS, 105, 173, 178, ELSEVIER SCI LTD, 2019年02月, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）, A well-designed experimental method has been presented to in-situ visualize the amorphous-to-crystalline phase transformation of two glass formers at the atomic length scale in the supercooled liquid region using a high voltage electron microscopy (HVEM). Analysis of the HVEM high-resolution images, supported by the in situ synchrotron diffraction, further confirms previous observations of distinctively different crystallization pathways in the two Zr-Cu-Al alloys. Moreover, the HVEM results illustrate that isolated distributed nanocrystals with mutual orientation easily grew up from the Zr56Cu36Al8, an average glass former, which follows a classical crystallization pathway; while density population poorly ordered atomic clusters with large misorientation suspended the growth in the Zr46Cu46Al8, a good glass former, which might follow an unusual crystallization pathway. In addition, in-situ synchrotron diffraction measurements confirm that the Zr56Cu36Al8 alloy finally crystallized into an extended structure, in contrast, the final crystalline product of Zr46Cu46Al8 alloy possesses a damped structure. Our study provides a detailed microscopic understanding of the crystallization behaviors in the supercooled liquids, showing that the density population nucleation site with large misorientation and the confined final crystalline structure contribute to the stability of Zr-Cu-Al supercooled liquids.

中性子増倍材料としてのベリリウム及びその合金　　　　　　　　　　　　　　　
Masaru Nakamichi, Jae-HwanKim, Makoto M Nakamura, SHIBAYAMA Tamaki, Christopher K Dorn, Chakin Vladimir, Dmitry V Bachurin, Christopher Stihl, Pavel V Vladimirov
Comprehensive Nuclear Materials 2nd edition, Elsevier, 1, 48, 2019年, ［査読有り］, ［招待有り］, ［国際共著］, ［国際誌］
英語, 論文集(書籍)内論文

Special issue on new trends for structural and chemical analyses by transmission electron microscopy
Manabu Ishimaru, Tomasz Goryczka, Hiroki Kurata, Kenji Matsuda, Syo Matsumura, Yasukazu Murakami, Katsuhiko Nishimura, Norihito Sakaguchi, Tamaki Shibayama
Materials Transactions, 60, 5, 674, 2019年, ［査読有り］, ［国際共著］, ［国際誌］
研究論文（学術雑誌）

Japanese activities of the R&D on silicon carbide composites in the broader approach period and beyond
Takashi Nozawa, Kazumi Ozawa, Chang Ho Park, Joon Soo Park, Akira Kohyama, Akira Hasegawa, Shuhei Nogami, Tatsuya Hinoki, Sosuke Kondo, Toyohiko Yano, Tamaki Shibayama, Bun Tsuchiya, Tatsuo Shikama, Shinji Nagata, Teruya Tanaka, Hirotomo Iwakiri, Yasushi Yamamoto, Satoshi Konishi, Ryuta Kasada, Masatoshi Kondo, Tomoaki Kunugi, Takehiko Yokomine, Yoshitaka Ueki, Nariaki Okubo, Tomitsugu Taguchi, Hiroyasu Tanigawa
Journal of Nuclear Materials, 511, 582, 590, 2018年12月01日, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）, © 2018 Elsevier B.V. The R&D on SiC/SiC composites under the broader approach (BA) activities between Japan and the EU for fusion DEMO developed a fundamental database of mechanical (Task-1) and physical/chemical (Task-2) properties, with a primary target of the application of SiC/SiC composites as functional structure to be used in the dual coolant breeding blanket concept. This paper aims to summarize previous 10-years activities of the R&D of Japan and to provide the key deliverables toward the DEMO design. In Task-1, good creep and fatigue durability were first demonstrated. Besides, in-plane and inter-laminar strength anisotropy maps at elevated temperatures were comprehensively identified. In parallel, the irradiation effects of SiC materials were specifically determined as input parameters of the analytical model to provide for the irradiation-induced residual stresses. In Task-2, the apparent dose-dependence of the radiation-induced electrical conductivity and the indicative radiation-induced electrical degradation was identified by various irradiation sources. In addition, good gas confinement was identified. Furthermore, no accelerated corrosion for duration of 3000 h at below 1173 K was first demonstrated. With these achievements, it is suggested that the in-vessel component technology, e.g., material corrosion database development, activated corrosion product evaluation code development, compact module tests for validation of the key functions of the components, technology integration assessment for fusion nuclear tests, etc., should be further developed toward DEMO in near-term.

Fabrication of tungsten and carbon clad plates by sinter bonding methods for divertor system characterization
Kishimoto Hirotatsu, Asakura Yuuki, Matano Minoru, Nakazato Naofumi, Park Joon-Soo, Shibayama Tamaki, Fukumoto Masakatsu
FUSION ENGINEERING AND DESIGN, 136, 116, 119, ELSEVIER SCIENCE SA, 2018年11月, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）, Full tungsten divertor is employed for ITER, and the tungsten will be the most potential candidate for the surface material of plasma facing components in fusion reactor after DEMO. Under a Broader Approach (BA) activity, a satellite tokamak device JT-60SA is expected to contribute the investigation of many factors and issues related to the fusion plasma and components. JT-60SA has a future plan to transfer the surface of plasma facing components from carbon fiber reinforced carbon composite (CFC) to tungsten, and investigate the interaction of plasma and tungsten. For this plan, joining and coating technologies of tungsten on CFC is an important issue. Present research developed a fabrication method of the W/CFC clad plates and investigated the mechanical, micro structural and thermal properties of them.

Evolution of 3D nanoporosity and morphology in selectively dealloying ternary Au55Cu25Si20 metallic glass ribbon with enhanced alcohol electro-oxidation performance
Xu Yi, Cheng Junye, Yiu Pak Man, Shan Guangcun, Shibayama Tamaki, Watanabe Seiichi, Ohnuma Masato, Shek Chan-Hung
NANOSCALE, 10, 39, 18846, 18856, ROYAL SOC CHEMISTRY, 2018年10月21日, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）, Current fabrication methods of nanoporous gold (NPG) mainly rely on dealloying Ag-Au binary crystalline precursors, typically Ag65Au35, with the "dealloying threshold" or "parting limit" above 55 at%. Here we report a simple chemical dealloying process, through selective dissolution of one element from a Au55Cu25Si20 metallic glass ribbon with low 'parting limit', and a novel peculiar three-dimensional 'cone shaped protrusion' nanoporous structure which has never been reported before. In this structure, a metastable gold silicide formed in the initial dealloying stage was decomposed into gold nanoparticles and amorphous SiOx in the later coarsening stage. Our finding provides insights into the underlying relationship between 'parting limit' and atomic level structure of metallic glass. Comprehensive discussions on the porosity evolution stages as well as the correlation between the porous 'cone shaped protrusion' development and potential energy landscape are made in this report. The fabricated 3D NPG also exhibited excellent electro-oxidation catalytic ability attributed to the high density of low-coordinated atomic sites provided by the gold particle inside of 'cone shaped protrusion'.

Mechanism of formation, structural characteristics and photocatalytic activities of hierarchical-structured bismuth-tungstate particles
H. Hori, M. Takase, M. Takashima, F. Amano, T. Shibayama, B. Ohtani
CATALYSIS TODAY, 300, 99, 111, ELSEVIER SCIENCE BV, 2018年02月, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）, The mechanism of the formation of flake ball-shaped (FB) bismuth-tungstate (BWO) particles was studied with samples prepared by hydrothermal reactions under standard conditions (tungsten/bismuth ratio of 0.55 in feed; 433 K; 20 h) and other modified conditions, and the structural characteristics of the samples were analyzed by powder X-ray diffraction (composition and crystal structure), field emission-type scanning electron microscopy (FE-SEM) (morphology), focused ion-beam etching followed by FE-SEM (inner void structure), ultrahigh-voltage transmission electron microscopy (inner void structure) and low-voltage scanning electron microscopy with energy-dispersive X-ray spectroscopic analysis (morphology and elemental distribution). Based on the results, a novel two-step mechanism of (1) formation of aqueous bismuth-oxyhydroxide droplets covered by tungstic acid (BOx@HWO) with fluidity and (2) reaction of inner bismuth and outer tungsten components at the BOx@HWO surface to yield BWO flakes is proposed as a one of the most plausible pathways that are consistent with the hollow structure of FB BWO and observations of the products prepared with shorter hydrothermal reaction. Photocatalytic activities of FB BWO samples in relation to their structure were studied.

3D Nanoporous Gold with Very Low Parting Limit Derived from Au-Based Metallic Glass and Enhanced Methanol Electro-oxidation Catalytic Performance Induced by Metal Migration
Yi Xu, Pak Man Yiu, Guangcun Shan, Tamaki Shibayama, Seiichi Watanabe, Masato Ohnuma, Wei Huang, Chan-Hung Shek
ChemNanoMat, 4, 1, 88, 97, Wiley-VCH Verlag, 2018年, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）, Nanoporous gold (NPG) with bi-continuous ligaments and pores structure has promising potential in functional applications, among which one prominent example is fuel cell electrocatalysts. However, current application of NPG is mostly limited to methanol electro-oxidation (MOR) due to its weak catalytic performance. Here we report a simple chemical dealloying process for generating peculiar three-dimensional (3D) free-standing NPG with ‘parting limit’ as low as 25 % (lower than theoretical ‘paring limit’ 55 %) and high specific surface area (maximum ≈31 m2 g−1) associated with a novel porous ‘cone shaped protrusion’ morphology. This NPG structure possesses the highest specific activity of MOR catalytic performance reported NPG catalysts so far. In addition, taking advantage of this excellent structural feature of the NPG, a nanoporous Pd catalyst (NPG@Pd) thin film was fabricated on the NPG substrate. The NPG@Pd catalyst exhibited greatly enhanced MOR performance (maximum MOR specific activity 2.14 mA cm−2). We attribute the enhancement of MOR activity to the increase of active sites as well as the modification of surface composition and electronic structure due to migration of Au to the Pd thin film layer.

Thermal property and microstructural characterization of W/SiC clad plates
Yuuki Asakura, Hirotatsu Kishimoto, Joon-Soo Park, Naofumi Nakazato, Tamaki Shibayama, Akira Kohyama
Fusion Engineering and Design, 125, 484, 489, Elsevier Ltd, 2017年12月01日, ［査読有り］
英語, 研究論文（学術雑誌）, A SiC/SiC composite is a candidate for the structural material of fusion reactors after Demonstration Power Plant (DEMO). Tungsten will be employed as an armor of SiC/SiC constructed divertor, the developments of fabrication method and optimization of thermal property of them are the important issues. Present research produced W and SiC/SiC clad plates using a diffusion bonding method and tried to investigate the thermal characters of the interphase between W and SiC/SiC composites. The thermal conductivities of W/SiC clad, SiC/SiC and tungsten plates were characterized by a laser flash method at temperatures up to 773 K. The thermal data was approximated by functions and applied as material data to an analysis by finite element method (FEM). The simple FEM model of the divertor suggested that the existence of the interfacial phase with low apparent thermal conductivity of the divertor system under the heat flux exposure of 5 MW/m2 may cause fracture of the system due to thermal stress. The results show the importance of the improvement of the interphase to enhance the thermal properties and the reactor design to reduce thermal flux for the divertor surface.

Ion beam surface nanostructuring of noble metal films with localized surface plasmon excitation
Xuan Meng, Tamaki Shibayama, Ruixuan Yu, Junya Ishioka, Seiichi Watanabe
CURRENT OPINION IN SOLID STATE & MATERIALS SCIENCE, 21, 4, 177, 188, PERGAMON-ELSEVIER SCIENCE LTD, 2017年08月, ［査読有り］, ［招待有り］
英語, 研究論文（学術雑誌）, Noble metal nanoparticles strongly adhered to dielectric matrices have been extensively studied because of their potential applications in plasmonic devices based on tunable localized surface plasmon (LSP) excitation. Compared with conventional synthesis methods, the noble metal nanoparticles formed by ion-beam irradiation draw significant interest in recent years because a single layer dispersion of nanoparticles strongly bonded on the dielectric substrate can be obtained. In this paper, important phenomena related to ion-beam surface nanostructuring including ion-induced reshaping of metal nanoparticles, ion-induced core-satellite structure formation, and ion-induced burrowing of these nanoparticles are discussed, with their individual effects on LSP excitation. Consequently, ion-induced surface nanostructuring of Ag-Au bimetallic films on amorphous silica glass and sapphire with tunable LSP excitation are presented. In addition, theoretical studies of far-field and near-field optical properties of these nanoparticles under ion irradiation are introduced, and the enhanced localized electric field (hot spot) is interpreted. Finally, the futures and challenges of the emerging plasmonic applications based on tunable LSP excitations in bio-sensing and surface enhanced Raman spectroscopy (SERS) are presented. (C) 2017 Elsevier Ltd. All rights reserved.

Plasmonic surface nanostructuring of Au-dots@SiO2 via laser-irradiation induced dewetting
Ruixuan Yu, Tamaki Shibayama, Junya Ishioka, Xuan Meng, Yanhua Lei, Seiichi Watanabe
Nanotechnology, 28, 27, 275701, 275701-11, Institute of Physics Publishing, 2017年06月09日, ［査読有り］, ［責任著者］
英語, 研究論文（学術雑誌）, The in situ observation of Au dot formation and the self-assembly dynamics of Au nanoparticles (NPs) was successfully demonstrated via dewetting of Au thin films on SiO2 glass substrates under nano-second pulsed laser irradiation using a multi-quantum beam high-voltage electron microscope. Moreover, using electron energy-loss spectroscopy (EELS) performed in a scanning transmission electron microscope (STEM), the plasmonic properties of the formed Au/SiO2 nanostructure were analyzed to demonstrate its validity in advanced optical devices. The uniformly distributed Au NPs evolved into a dot alignment through movement and coalescence processes was demonstrated in this in situ observation. We carried out the plasmon-loss images of the plan view and the cross-section of the Au/SiO2 nanostructures were obtained at the plasmon-loss peak energy for investigate the three-dimensional distribution of surface plasmon. Furthermore, discrete-dipole approximation (DDA) calculations were used to simulate the plasmonic properties, such as the surface plasmon resonance and the surface plasmon field distribution, of isolated single Au/SiO2 nanostructures. This STEM-EELS-acquired surface plasmon map of the cross-sectional sample is in excellent agreement with the DDA calculations. This results demonstrated the influence of the contact condition between Au NP and SiO2 glass on the plasmonic properties, and may improve the technology for developing advanced optical devices.

Toward hybrid Au nanorods @ M (Au, Ag, Pd and Pt) core-shell heterostructures for ultrasensitive SERS probes
Xiaobin Xie, Guanhui Gao, Shendong Kang, Yanhua Lei, Zhengyin Pan, Tamaki Shibayama, Lintao Cai
NANOTECHNOLOGY, 28, 24, IOP PUBLISHING LTD, 2017年06月, ［査読有り］
英語, 研究論文（学術雑誌）, Being able to. precisely control the morphologies of noble metallic nanostructures is of essential significance for promoting the surface-enhanced Raman scattering (SERS) effect. Herein, we ;demonstrate an overgrowth strategy for synthesizing. Au @ M( M = Au, Ag, Pd, Pt) core-shell heterogeneous nanocrystals with an orientated structural evolution and highly improved properties by using. Au nanorods as seeds. With the same reaction condition system applied, we obtain four well-designed heterostructures with diverse shapes, including Au concave nanocuboids (Au CNs), Au @ Ag crystalizing face central cube nanopeanuts, Au @ Pd porous nanocuboids and Au @ Pt nanotrepangs. Subsequently, the exact overgrowth mechanism of the above heterostructural building blocks is further analysed via the systematic. optimiziation of a series of fabrications. Remarkably, the well-defined Au CNs and Au @ Ag nanopeanuts both exhibit highly promoted SERS activity. We expect to be able to supply a facile strategy for the fabrication of multimetallic heterogeneous nanostructures, exploring the high SERS effect and catalytic activities.

Effect of laser and/or electron beam irradiation on void swelling in SUS316L austenitic stainless steel
Subing Yang, Zhanbing Yang, Hui Wang, Seiichi Watanabe, Tamaki Shibayama
JOURNAL OF NUCLEAR MATERIALS, 488, 215, 221, ELSEVIER SCIENCE BV, 2017年05月, ［査読有り］
英語, 研究論文（学術雑誌）, Large amounts of void swelling still limit the application of austenitic stainless steels in nuclear reactors due to radiation-induced lattice point defects. In this study, laser and/or beam irradiation was conducted in a temperature range of 573-773 K to explore the suppression of void swelling. The results show that during sequential laser-electron beam irradiation, the void nucleation is enhanced because of the vacancy clusters and void nuclei formed under pre-laser irradiation, causing greater void swelling than single electron beam irradiation. However, simultaneous laser-electron dual-beam irradiation exhibits an obvious suppression effect on void swelling due to the enhanced recombination between interstitials and vacancies in the temperature range of 573-773 K; especially at 723 K, the swelling under simultaneous dual-beam irradiation is 0.031% which is only 22% of the swelling under electron beam irradiation (0.137%). These results provide new insight into the suppression of void swelling during irradiation. (C) 2017 Elsevier B.V. All rights reserved.

Tuning Optoelectrical Properties of ZnO Nanorods with Excitonic Defects via Submerged Illumination
Melbert Jeem, Lihua Zhang, Junya Ishioka, Tamaki Shibayama, Tomio Iwasaki, Takahiko Kato, Seiichi Watanabe
NANO LETTERS, 17, 3, 2088, 2093, AMER CHEMICAL SOC, 2017年03月, ［査読有り］
英語, 研究論文（学術雑誌）, When applied in optoelectronic devices, a ZnO semiconductor dominantly absorbs or emits ultraviolet light because of its direct electron transition through a wide energy bandgap. On the contrary, crystal defects and nanostructure morphology are the chief key factors for indirect, interband transitions of ZnO optoelectronic devices in the visible light range. By ultraviolet illumination in ultrapure water, we demonstrate here a conceptually unique approach to tune the shape of ZnO nanorods from tapered to capped end via apical surface morphology control. We show that oxygen vacancy point defects activated by excitonic effects near the tip-edge of a nanorod serve as an optoelectrical hotspot for the light-driven formation and tunability of the optoelectrical properties. A double increase of electron energy absorption on near band edge energy of ZnO was observed near the tip-edge of the tapered nanorod. The optoelectrical hotspot explanation rivals that of conventional electrostatics, impurity control, and alkaline pH control-associated mechanisms. Thus, it highlights a new perspective to understanding light-driven nanorod formation in pure neutral water.

Hidden amorphous phase and reentrant supercooled liquid in Pd-Ni-P metallic glasses
S. Lan, Y. Ren, X. Y. Wei, B. Wang, E. P. Gilbert, T. Shibayama, S. Watanabe, M. Ohnuma, X. -L. Wang
NATURE COMMUNICATIONS, 8, 14679, NATURE PUBLISHING GROUP, 2017年03月, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）, An anomaly in differential scanning calorimetry has been reported in a number of metallic glass materials in which a broad exothermal peak was observed between the glass and crystallization temperatures. The mystery surrounding this calorimetric anomaly is epitomized by four decades long studies of Pd-Ni-P metallic glasses, arguably the best glass-forming alloys. Here we show, using a suite of in situ experimental techniques, that Pd-Ni-P alloys have a hidden amorphous phase in the supercooled liquid region. The anomalous exothermal peak is the consequence of a polyamorphous phase transition between two supercooled liquids, involving a change in the packing of atomic clusters over medium-range length scales as large as 18 angstrom. With further temperature increase, the alloy reenters the supercooled liquid phase, which forms the room-temperature glass phase on quenching. The outcome of this study raises a possibility to manipulate the structure and hence the stability of metallic glasses through heat treatment.

In situ direct observation of photocorrosion in ZnO crystals in ionic liquid using a laser-equipped high-voltage electron microscope
J. Ishioka, K. Kogure, K. Ofuji, K. Kawaguchi, M. Jeem, T. Kato, T. Shibayama, S. Watanabe
AIP ADVANCES, 7, 3, 035220, AMER INST PHYSICS, 2017年03月, ［査読有り］
英語, 研究論文（学術雑誌）, ZnO photocatalysts in water react with environmental water molecules and corrode under illumination. ZnO nanorods in water can also grow because of water splitting induced by UV irradiation. To investigate their morphological behavior caused by crystal growth and corrosion, here we developed a new laser-equipped high-voltage electron microscope and observed crystal ZnO nanorods immersed in ionic liquid. Exposing the specimen holder to a laser with a wavelength of 325 nm, we observed the photo-corrosion in situ at the atomic scale for the first time. This experiment revealed that Zn and O atoms near the interface between the ZnO nanorods and the ionic liquid tended to dissolve into the liquid. The polarity and facet of the nanorods were strongly related to photocorrosion and crystal growth. (C) 2017 Author(s).

Controlling Shape Anisotropy of ZnS-AgInS2 Solid Solution Nanoparticles for Improving Photocatalytic Activity
Tsukasa Torimoto, Yutaro Kamiya, Tatsuya Kameyama, Hiroyasu Nishi, Taro Uematsu, Susumu Kuwabata, Tamaki Shibayama
ACS APPLIED MATERIALS & INTERFACES, 8, 40, 27151, 27161, AMER CHEMICAL SOC, 2016年10月, ［査読有り］
英語, 研究論文（学術雑誌）, Independently controlling the shape anisotropy and chemical composition of multinary semiconductor particles is important for preparing highly efficient photo catalysts. In this study, we prepared ZnS-AgInS2 solid solution ((AgIn)(x)Zn2(i1-)S2, ZAIS) nanoparticles with well-controlled anisotropic shapes, rod, and rice shapes, by reacting corresponding metal acetates with a mixture of sulfur compounds with different reactivities, elemental sulfur, and 1,3-dibutylthiourea, via a two-step heating-up process. The chemical composition predominantly determined the energy gap of ZAIS particles: the fraction of Zn2+ in rod-shaped particles was tuned by the ratio of metal precursors used in the nanocrystal formation, while postpreparative Zn2+ doping was necessary to increase the Zn2+ fraction in the rice-shaped particles. The photocatalytic H-2 evolution rate with irradiation to ZAIS particles dispersed in an aqueous solution was significantly dependent on the chemical composition in the case of using photocatalyst particles with a constant morphology. In contrast, photocatalytic activity at the optimum ZAIS composition, x of 0.35-0.45, increased with particle morphology in the order of rice (size: ca. 9 X ca. 16 nm) < sphere (diameter: ca. 5.5 run) < rod (size: 4.6 X 27 nm). The highest apparent quantum yield for photocatalytic H-2 evolution was 5.9% for rod-shaped ZAIS particles, being about two times larger than that obtained with spherical particles.

In-situ observation of self-assembly of quasi-two-dimensional Au nano-submicron particles on β-SiC substrates via nanosecond-pulsed laser irradiation-induced dewetting of thin Au films
Y. H. Lei, R. X. Yu, T. Shibayama, J. Ishioka, S. Watanabe
Materials Letters, 164, 1, 202, 205, ELSEVIER SCIENCE BV, 2016年02月, ［査読有り］
英語, 研究論文（学術雑誌）, Herein is reported the dots alignment of Au nano-submicron particles (Au-NPs) on a chemical vapor-deposited beta-SiC substrate through nanosecond-pulsed laser irradiation-induced dewetting of an Au thin film, which was successfully observed by in-situ high-voltage electron microscopy. The initial stages of the Au-NPs array arrangement were also successfully observed, and long-range quasi-two-dimensional Au-NPs arrangements were found after laser irradiation. Moreover, the effect of Rayleigh instability to form multiple Au-NPs in each line of the network structure after the hole growth in the Au thin film was confirmed. (C) 2015 Elsevier B.V. All rights reserved.

Synthesis of surfactant-free Cu-Pt dendritic heterostructures with highly electrocatalytic performance for methanol oxidation reaction
Shendong Kang, Guanhui Gao, Xiaobin Xie, Tamaki Shibayama, Yanhua Lei, Yan Wang, Lintao Cai
MATERIALS RESEARCH LETTERS, 4, 4, 212, 218, TAYLOR & FRANCIS INC, 2016年, ［査読有り］
英語, 研究論文（学術雑誌）, A facile and free surfactant strategy is explored to synthesize Cu-Pt bimetallic nano-heterostructures with dendritic exterior. For comparison, the Cu-Pt coral-like nanoparticles are fabricated by using CTAC as a surfactant. The well-designed Cu-Pt dendritic spherical heterostructures exhibit superior enhanced electrocatalytic activity and stability toward methanol oxidation reaction in alkaline media, compared to the Cu-Pt coral-like nanoparticles and the commercial Pt/C, respectively. The advanced technique for fabricating Cu-Pt dendritic spherical heterostructures could pave a way to pursue low-cost Pt-based catalysts, maintaining highly promoted electrocatalytic performance and durability.
[GRAPICS]
IMPACT STATEMENT
The well-designed Cu-Pt dendritic spherical heterostructures are synthesized without any surfactant, which demonstrate highly promoted electrocatalytic performance and durability toward methanol oxidation reaction.

Photophysical properties of luminescent silicon nanoparticles surface-modified with organic molecules via hydrosilylation
Mari Miyano, Yuichi Kitagawa, Satoshi Wada, Akira Kawashima, Ayako Nakajima, Takayuki Nakanishi, Junya Ishioka, Tamaki Shibayama, Seiichi Watanabe, Yasuchika Hasegawa
PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES, 15, 1, 99, 104, ROYAL SOC CHEMISTRY, 2016年, ［査読有り］
英語, 研究論文（学術雑誌）, Luminescent silicon nanoparticles have attracted considerable attention for their potential uses in various applications. Many approaches have been reported to protect the surface of silicon nanoparticles and prevent their easy oxidation. Various air-stable luminescent silicon nanoparticles have been successfully prepared. However, the effect of interactions of the pi-electron system with the silicon surface on the excited state properties of silicon nanoparticles is unclear. In this study, we have successfully prepared silicon nanoparticles protected with three organic compounds (styrene, 1-decene, and 1-vinyl naphthalene) and have examined their photophysical properties. The ligand pi-electron systems on the silicon surface promoted the light harvesting ability for the luminescence through a charge transfer transition between the protective molecules and silicon nanoparticles and also enhanced the radiative rate of the silicon nanoparticles.

Site‐Selective Trimetallic Heterogeneous Nanostructures for Enhanced Electrocatalytic Perf
X. Xie, G. Gao, S. Kang, T. Shibayama, Y. Lei, D. Gao, L. Cai
Advanced Materials, 27, 37, 5573, 5577, WILEY-V C H VERLAG GMBH, 2015年10月, ［査読有り］
英語, 研究論文（学術雑誌）, Trimetallic Au/Ag/Pt hetero-nanostructures (AAPHNs) with distinctive, designed morphology are synthesized by galvanic replacement reaction and a site-selective strategy. The three metals present on the surface are shown to act synergistically to enhance the electro-catalytic performance and durability for methanol oxidation. The described structural modification of the nanocomposites increases the range of potential applications to include both the oxygen reduction reaction in fuel cells and photocatalysis of the hydrogen evolution reaction.

In situ transmission electron microscopy for electronics
M. Arita, K. Hamada, Y. Takahashi, K. Sueoka, T. Shibayama
The Transmission Electron Microscope - Theory and Applications, 33, 68, 2015年09月02日, ［査読有り］
英語, 研究論文（学術雑誌）

In-Situ TEM Observation of Dynamic Nehavior of Metal-Based Nanoparticles in Ionic Liquid　　　　　　　　　　　　　　　
K. Kogure, J. Ishioka, K. Ofuji, R. Mirza, S. Yatsu, T. Shibayama, S. Watanabe
Extended abstract of 2015 international Conference on Solid State Devices and Materials, 2015年09月, ［査読有り］
英語, 研究論文（国際会議プロシーディングス）

A pathway of nanocrystallite fabrication by photo-assisted growth in pure water
Melbert Jeem, Muhammad Rafiq Mirza bin Julaihi, Junya Ishioka, Shigeo Yatsu, Kazumasa Okamoto, Tamaki Shibayama, Tomio Iwasaki, Takahiko Kato, Seiichi Watanabe
SCIENTIFIC REPORTS, 5, 11429, NATURE PUBLISHING GROUP, 2015年06月, ［査読有り］
英語, 研究論文（学術雑誌）, We report a new production pathway for a variety of metal oxide nanocrystallites via submerged illumination in water: submerged photosynthesis of crystallites (SPSC). Similar to the growth of green plants by photosynthesis, nanocrystallites shaped as nanoflowers and nanorods are hereby shown to grow at the protruded surfaces via illumination in pure, neutral water. The process is photocatalytic, accompanied with hydroxyl radical generation via water splitting; hydrogen gas is generated in some cases, which indicates potential for application in green technologies. Together with the aid of ab initio calculation, it turns out that the nanobumped surface, as well as aqueous ambience and illumination are essential for the SPSC method. Therefore, SPSC is a surfactant-free, low-temperature technique for metal oxide nanocrystallites fabrication.

Anisotropic surroundings effects on photo absorption of partially embedded Au nanospheroids in silica glass substrate
Xuan Meng, Tamaki Shibayama, Ruixuan Yu, Junya Ishioka, Seiichi Watanabe
AIP ADVANCES, 5, 2, 027112, AMER INST PHYSICS, 2015年02月, ［査読有り］
英語, 研究論文（学術雑誌）, The influence of a directly adjacent or an anisotropic surrounding medium alters the plasmonic properties of a nanoparticle because it provides a mechanism for symmetry breaking of the scattering. Given the success of ion irradiation induced embedment of rigid metallic nanospheroids into amorphous substrate, it is possible to examine the effect of the silica glass substrate on the plasmonic properties of these embedded nanospheroids. In this work presented here, discrete dipole approximation (DDA) calculations for the Au nanospheroids' optical properties were performed based on 3-dimensional (3D) configuration extracted from planar SEM micrographs and cross-sectional TEM micrographs of the Au nanospheroids partially embedded in the silica glass, and the well-matched simulations with respect to the experimental measurements could demonstrate the dielectric constant at the near surface of silica glass decreased after Ar-ion irradiation. (C) 2015 Author(s).

Ultrathin oxide shell coating of metal nanoparticles using ionic liquid/metal sputtering
Tsukasa Torimoto, Yasuhiro Ohta, Kazuki Enokida, Daisuke Sugioka, Tatsuya Kameyama, Takahisa Yamamoto, Tamaki Shibayama, Kazuki Yoshii, Tetsuya Tsuda, Susumu Kuwabata
JOURNAL OF MATERIALS CHEMISTRY A, 3, 11, 6177, 6186, ROYAL SOC CHEMISTRY, 2015年, ［査読有り］
英語, 研究論文（学術雑誌）, The surface coating of metal nanoparticles resulting into core-shell structures is expected to improve the physicochemical properties of the nanoparticle cores without changing their size and shape. Here, we developed a novel strategy to coat Au, AuPd or Pt catalyst cores having average sizes smaller than 2.5 nm, which were pre-synthesized in ionic liquids by corresponding metal sputtering, with an extremely thin In2O3 layer (ca. <1.5 nm) by sputter deposition of indium in a room-temperature ionic liquid. The metal cores of Au or AuPd in core-shell particles exhibited superior stability against heat treatments or during electrocatalytic reactions compared to the corresponding bare metal particles. The In2O3 shell coating considerably enhanced the durability of electrocatalytically active Pt particles (1.2 nm). This sequential metal sputter deposition of different metals in ionic liquids will considerably contribute to the exploitation of key nanostructured components for next-generation energy-conversion systems.

異種原子注入 講座・電子顕微鏡による材料研究
柴山 環樹, 渡辺 精一
軽金属, 64, 12, 659, 662, 軽金属学会, 2014年12月, ［査読有り］, ［招待有り］
日本語, 研究論文（学術雑誌）

Recent activities in the field of nuclear materials and nuclear fuels
Ikuo Ioka, Tamaki Shibayama
JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY, 51, 5, 735, 736, TAYLOR & FRANCIS LTD, 2014年05月, ［査読有り］, ［招待有り］
英語, 研究論文（その他学術会議資料等）

Effects of ion and nanosecond-pulsed laser co-irradiation on the surface nanostructure of Au thin films on SiO2 glass substrates
Ruixuan Yu, Tamaki Shibayama, Xuan Meng, Shinya Takayanagi, Shigeo Yatsu, Junya Ishioka, Seiichi Watanabe
JOURNAL OF APPLIED PHYSICS, 115, 14, 143104, AMER INST PHYSICS, 2014年04月, ［査読有り］
英語, 研究論文（学術雑誌）, Ion irradiation and short-pulsed laser irradiation can be used to form nanostructures on the surfaces of substrates. This work investigates the synergistic effects of ion and nanosecond-pulsed laser co-irradiation on surface nanostructuring of Au thin films deposited under vacuum on SiO2 glass substrates. Gold nanoparticles are randomly formed on the surface of the substrate after nanosecond-pulsed laser irradiation under vacuum at a wavelength of 532 nm with a repetition rate of 10 Hz and laser energy density of 0.124 kJ/m(2). Gold nanoparticles are also randomly formed on the substrate after 100-keV Ar+ ion irradiation at doses of up to 3.8 x 10(15) ions/cm(2), and nearly all of these nanoparticles are fully embedded in the substrate. With increasing ion irradiation dose (number of incident laser pulses), the mean diameter of the Au nanoparticles decreases (increases). However, Au nanoparticles are only formed in a periodic surface arrangement after co-irradiation with 6000 laser pulses and 3.8 x 10(15) ions/cm(2). The periodic distance is similar to 540 nm, which is close to the wavelength of the nanosecond-pulsed laser, and the mean diameter of the Au nanoparticles remains at similar to 20 nm with a relatively narrow distribution. The photoabsorption peaks of the ion-or nanosecond-pulsed laser-irradiated samples clearly correspond to the mean diameter of Au nanoparticles. Conversely, the photoabsorption peaks for the co-irradiated samples do not depend on the mean nanoparticle diameter. This lack of dependence is likely caused by the periodic nanostructure formed on the surface by the synergistic effects of co-irradiation. (C) 2014 AIP Publishing LLC.

Effects of nanosecond-pulsed laser irradiation on nanostructure formation on the surface of thin Au films on Si02 glass substrates
Ruixuan Yu, Tamaki Shibayama, Xuan Meng, Shinya Takayanagi, Yutaka Yoshida, Shigeo Yatsu, Seiichi Watanabe
APPLIED SURFACE SCIENCE, 289, 274, 280, ELSEVIER SCIENCE BV, 2014年01月, ［査読有り］
英語, 研究論文（学術雑誌）, In this study, we investigated nanostructure formations on the surface of Au thin films deposited on SiO2 glass substrates after nanosecond-pulsed laser irradiation, also the correlation between the nanostructures parameters and the photoabsorption peak. Spherical Au nanoparticle/SiO2 glass nanocomposites were formed on the surface of the Au thin films deposited on the SiO2 glass substrates after nanosecondpulsed laser irradiation in air with a wavelength of 532 nm at a repetition rate of 2 Hz and a laser energy density of 0.7 kJ/m(2). Au nanoparticles were periodically arranged on the substrates under laser irradiation perpendicular to the direction of the electrical field vector of the laser light, the average diameter of Au nanoparticles was increased from 59.3 to 67.4 nm and the average distance of the laser induced periodical structure was decreased from 1.3 to 1.0 mu m as the number of laser pulses increased from 1000 to 1500. After 2000 pulses irradiation, an additional laser irradiation induced periodical structure was formed in the direction parallel to the electrical field vector of the laser. The average periodicity of this nanostructure perpendicular to the initial nanostructure was 560 nm, which is close to the wavelength of the nanosecond-pulsed laser used in this study. The average diameter of these Au nanoparticles is 41.9 nm which is smaller than that of the Au nanoparticles formed after 1000 pulses irradiation. Au nanoparticles were generally dispersed on the surface while some were embedded in the substrate. After 1500 pulses irradiation, the diameter of the Au nanoparticles on the Au(30 nm)/SiO2(0.8 mm) is relatively larger than that of the Au nanoparticles on the Au(20 nm)/SiO2(0.1 mm). Each of laser irradiated sample showed an own photoabsorption peak clearly in this study. Furthermore, effects of the average diameter of the Au nanoparticles on the photoabsorption peak are discussed. (C) 2013 Elsevier B.V. All rights reserved.

SiC/SiC fuel cladding by nite process for innovative lwr-concept and process development of fuel pin assembly technologies
Hirotatsu Kishimoto, Tamaki Shibayama, Yuuki Asakura, Daisuke Hayasaka, Yutaka Kohno, Akira Kohyama
Ceramic Transactions, 246, 93, 98, American Ceramic Society, 2014年
英語, 研究論文（国際会議プロシーディングス）, SiC/SiC fuel cladding is a challenge to achieve a superior safety for light water reactors. A project aiming to produce just SiC/SiC cladding tube without zircaloy has been launched at Muroran Institute of Technology in Japan. The project named SCARLET is based on the NITE SiC/SiC technology. The NITE method has the potential to produce the cladding tube and the fuel pin assembly, but many technological issues, especially, relating to the mass production technologies need to be solved. The present paper will introduce the project SCARLET, the concepts of advances NITE SIC/SiC fabrication techniques, including new intermediate materials and SiC/SiC preform fabrication techniques. This paper also reports assembly techniques of SiC/SiC fuel pins.

ニッケル合金PE16への粒界工学の適用
鴇田 駿, 粉川 博之, 佐藤 裕, 藤井 啓道, 坂口 紀史, 柴山 環, 渡辺 精一
溶接学会全国大会講演概要, 2014, 226, 227, 一般社団法人 溶接学会, 2014年
日本語, ニッケル合金PE16への粒界工学の適用可能性を調査するために、ニッケル合金PE16にひずみ焼き鈍し法による粒界工学制御を行い、熱時効処理後の耐粒界腐食性の評価を行った。その結果、粒界工学の適用によりニッケル合金PE16の熱時効処理による耐粒界腐食性の低下を大幅に抑制することが示唆された。

Current status of beryllium materials for fusion blanket applications
Pavel Vladimirov, Dmitry Bachurin, Vladimir Borodin, Vladimir Chakin, Maria Ganchenkova, Alexander Fedorov, Michael Klimenkov, Igor Kupriyanov, Anton Moeslang, Masaru Nakamichi, Tamaki Shibayama, Sander Van Til, Milan Zmitko
Fusion Science and Technology, 66, 1, 28, 37, American Nuclear Society, 2014年, ［査読有り］
英語, 研究論文（学術雑誌）, Beryllium is a promising functional material for several breeder system concepts to be tested within the experimental fusion reactor ITER and, later, implemented in the first commercial demonstration fusion power plant DEMO. For these applications its resistance to neutron irradiation and the detrimental effects of radiogenic gases (helium and tritium) is crucial for fusion reactor safety, subsequent waste management and material recycling. A reliable prediction of beryllium behavior under fusion irradiation conditions requires both dedicated experiments and advanced modeling. Characterization of the reference and alternative beryllium pebble grades was performed in terms of their microstructure and tritium release properties. The results are discussed with respect to their application in fusion blanket systems. The outcomes from the HIDOBE-01 post irradiation experiment (PIE) are discussed to highlight several interesting features manifested by beryllium irradiation at fusion relevant temperatures. Titanium beryllide is presently developed as a possible substitute for beryllium pebbles as it shows better oxidation resistance, higher melting temperature and tritium release efficiency. Pebbles consisting predominantly of Be12Ti phase were successfully fabricated at Rokkasho, Japan. Recent advances in modeling provide new insights on the production of point defects and the behavior of helium and hydrogen impurities in beryllium, improving understanding of the mechanisms of primary damage production, hydrogen's effect on the size and the shape of gas bubbles, and tritium removal from the pebbles. The relevance of the experimental and modeling results on irradiated beryllium for the design of a fusion demonstration reactor is evaluated, and recommendations for future R&
D programs are proposed.

Shift of localized surface plasmon resonance by Ar-ion irradiation of Ag-Au bimetallic films deposited on Al2O3 single crystals
Xuan Meng, Tamaki Shibayama, Ruixuan Yu, Shinya Takayanagi, Seiichi Watanabe
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 314, 112, 116, ELSEVIER SCIENCE BV, 2013年11月, ［査読有り］
英語, 研究論文（学術雑誌）, Effects of Ar-ion induced surface nanostructuring were studied using 100 key Ar-ion irradiation of 30 nm Ag-Au bimetallic films deposited on Al2O3 single crystals, under irradiation fluences ranging from 5.0 x 10(15) cm(-2) to 6.3 x 10(16) cm(-2). Scanning electron microscope was used to study the ion-beam-induced surface nanostructuring. As the irradiation fluence increased, dewetting of the bimetallic films on the Al2O3 substrate was observed, and formation of isolated Ag-Au nanostructures sustained on the substrate were obtained. Next, thermal annealing was performed under high vacuum at 1073 K for 2 h; a layer of photosensitive Ag-Au alloy nanoballs partially embedded in the Al2O3 substrate was obtained when higher fluence irradiation (>3.8 x 10(16) cm(-2)) was used. The microstructures of the nanoballs were investigated using a transmission electron microscope, and the nanoballs were found to be single crystals with a FCC structure. In addition, photoabsorption spectra were measured, and localized surface plasmon resonance peaks were observed. With increase in the irradiation fluence, the size of the Ag-Au nanoballs on the substrate decreased, and a blue-shift of the LSPR peaks was observed. Further control of the LSPR frequency over a wide range was achieved by modifying the chemical components, and a red-shift of the LSPR peaks was observed as the Au concentration increased. In summary, ion irradiation is an effective approach toward surface nanostructuring, and the nanocomposites obtained have potential applications in optical devices. (C) 2013 Elsevier B.V. All rights reserved.

Enhanced Magneto-optical Properties of Semiconductor EuS Nanocrystals Assisted by Surface Plasmon Resonance of Gold Nanoparticles
Akira Kawashima, Takayuki Nakanishi, Tamaki Shibayama, Seiichi Watanabe, Koji Fujita, Katsuhisa Tanaka, Hitoshi Koizumi, Koji Fushimi, Yasuchika Hasegawa
CHEMISTRY-A EUROPEAN JOURNAL, 19, 43, 14438, 14445, WILEY-V C H VERLAG GMBH, 2013年10月, ［査読有り］
英語, 研究論文（学術雑誌）, Remarkable magneto-optical properties of a new isolator material, that is, europium sulfide nanocrystals with gold (EuS-Au nanosystem), has been demonstrated for a future photo-information technology. Attachment of gold particles that exhibit surface plasmon resonance leads to amplification of the magneto-optical properties of the EuS nanocrystals. To construct the EuS-Au nanosystems, cubic EuS and spherical Au nanocrystals have been joined by a variety of organic linkers, that is, 1,2-ethanedithiol (EDT), 1,6-hexanedithiol (HDT), 1,10-decanedithiol (DDT), 1,4-bisethanethionaphthalene (NpEDT), or 1,4-bisdecanethionaphthalene (NpDDT). Formation of these systems was observed by XRD, TEM, and absorption spectra measurements. The magneto-optical properties of the EuS-Au nanosystem have been characterized by using Faraday rotation spectroscopy. The Faraday rotation angle of the EuS-Au nanosystem is dependent on the Au particle size and interparticle distance between EuS and Au nanocrystals. Enhancement of the Faraday rotation of EuS-Au nanosystems was observed. The spin configuration in the excited state of the EuS-Au nanosystem was also investigated using photo-assisted electron paramagnetic resonance.

Enhanced Magneto-optical Properties of Semiconductor EuS Nanocrystals Assisted by Surface Plasmon Resonance of Gold Nanoparticles
Akira Kawashima, Takayuki Nakanishi, Tamaki Shibayama, Seiichi Watanabe, Koji Fujita, Katsuhisa Tanaka, Hitoshi Koizumi, Koji Fushimi, Yasuchika Hasegawa
CHEMISTRY-A EUROPEAN JOURNAL, 19, 43, 14438, 14445, WILEY-V C H VERLAG GMBH, 2013年10月, ［査読有り］
英語, 研究論文（学術雑誌）, Remarkable magneto-optical properties of a new isolator material, that is, europium sulfide nanocrystals with gold (EuS-Au nanosystem), has been demonstrated for a future photo-information technology. Attachment of gold particles that exhibit surface plasmon resonance leads to amplification of the magneto-optical properties of the EuS nanocrystals. To construct the EuS-Au nanosystems, cubic EuS and spherical Au nanocrystals have been joined by a variety of organic linkers, that is, 1,2-ethanedithiol (EDT), 1,6-hexanedithiol (HDT), 1,10-decanedithiol (DDT), 1,4-bisethanethionaphthalene (NpEDT), or 1,4-bisdecanethionaphthalene (NpDDT). Formation of these systems was observed by XRD, TEM, and absorption spectra measurements. The magneto-optical properties of the EuS-Au nanosystem have been characterized by using Faraday rotation spectroscopy. The Faraday rotation angle of the EuS-Au nanosystem is dependent on the Au particle size and interparticle distance between EuS and Au nanocrystals. Enhancement of the Faraday rotation of EuS-Au nanosystems was observed. The spin configuration in the excited state of the EuS-Au nanosystem was also investigated using photo-assisted electron paramagnetic resonance.

Ion irradiation synthesis of Ag–Au bimetallic nanospheroids in SiO2 glass substrate with tunable surface plasmon resonance frequency
メン シュアン, 柴山 環樹, ウ, エイケン, 高柳 伸也, 渡辺 精一
Journal of Applied Physics, 114, 5, 054308, AMER INST PHYSICS, 2013年08月, ［査読有り］
英語, 研究論文（学術雑誌）, Ag-Au bimetallic nanospheroids with tunable localized surface plasmon resonance (LSPR) were synthesized by 100 keV Ar-ion irradiation of 30 nm Ag-Au bimetallic films deposited on SiO2 glass substrates. A shift of the LSPR peaks toward shorter wavelengths was observed up to an irradiation fluence of 1.0 x 10(17) cm(-2), and then shifted toward the longer wavelength because of the increase of fragment volume under ion irradiation. Further control of LSPR frequency over a wider range was realized by modifying the chemical components. The resulting LSPR frequencies lie between that of the pure components, and an approximate linear shift of the LSPR toward the longer wavelength with the Au concentration was achieved, which is in good agreement with the theoretical calculations based on Gans theory. In addition, the surface morphology and compositions were examined with a scanning electron microscope equipped with an energy dispersive spectrometer, and microstructural characterizations were performed using a transmission electron microscope. The formation of isolated photosensitive Ag-Au nanospheroids with a FCC structure partially embedded in the SiO2 substrate was confirmed, which has a potential application in solid-state devices. (C) 2013 AIP Publishing LLC.

Microstructure analysis of ion beam-induced surface nanostructuring of thin Au film deposited on SiO2 glass
Xuan Meng, Tamaki Shibayama, Ruixuan Yu, Shinya Takayanagi, Seiichi Watanabe
JOURNAL OF MATERIALS SCIENCE, 48, 2, 920, 928, SPRINGER, 2013年01月, ［査読有り］
英語, 研究論文（学術雑誌）, Effects of the irradiation dose on surface nanostructuring accompanied with the dewetting process of Au films deposited on SiO2 glass were examined using an atomic force microscope and a scanning electron microscope. In addition, the microstructural evolution and the chemical concentration of Au films were investigated using a transmission electron microscope equipped with an energy-dispersive spectrometer. As increasing the Ar ion irradiation dose, the lattice expansion of Au nanoscale islands sustained on the SiO2 glass was observed and irradiation-induced lattice defects together with irradiation-induced interface ion mixing were accounted for this lattice expansion. Finally a layer of photosensitive Au nanoballs with highly spherical shape embedded in a SiO2 substrate was obtained after Ar ion irradiation to 10.0 x 10(16)/cm(2) and some of Au nanoballs were found to be single crystals. As the irradiation energy of the Ar ions increased from 100 to 150 keV, the average diameter of the Au nanoballs in the substrate increased and the red shift of the SPR peak was observed. This tendency of the experimental SPR peaks corresponded with that of the theoretically calculated SPR peaks using Mie solution.

Surface cracking on Sigma 3, Sigma 9 CSL and random grain boundaries in helium implanted 316L austenitic stainless steel
N. Sakaguchi, Y. Ohguchi, T. Shibayama, S. Watanabe, H. Kinoshita
JOURNAL OF NUCLEAR MATERIALS, 432, 1-3, 23, 27, ELSEVIER SCIENCE BV, 2013年01月, ［査読有り］
英語, 研究論文（学術雑誌）, The relationship between surface cracking at grain boundaries and the grain boundary nature in helium implanted 316L austenitic stainless steel was investigated by in situ annealing in a high-voltage electron microscope, and by SEM and TEM observations. The nucleation and growth of helium bubbles at a random grain boundary was observed during annealing up to 973 K. After annealing, surface cracking was observed at the random grain boundaries and some coincidence site lattice (CSL) boundaries because of the formation and rupture of the helium bubbles at these grain boundaries. At the faceted CSL boundaries, surface cracking occurred only on one boundary facet plane. This indicates that the twin boundary and pure tilt Sigma 9 CSL boundary show the highest resistance to cracking because of their low boundary energies. (c) 2012 Elsevier B.V. All rights reserved.

Preliminary characterization of plasma-sintered beryllides as advanced neutron multipliers
M. Nakamichi, J. H. Kim, K. Munakata, T. Shibayama, M. Miyamoto
Journal of Nuclear Materials, 442, 1-3 SUPPL.1, S465, S471, 2013年, ［査読有り］
英語, 研究論文（学術雑誌）, Advanced neutron multipliers with low swelling and high stability at high temperatures are desired for pebble bed blankets of demonstration fusion power (DEMO) reactors. Beryllium intermetallic compounds (beryllides) are the most promising advanced neutron multipliers. The plasma sintering method has been selected as a new synthesis method for beryllides because this method is very simple and easy to control. Plasma sintering is a non-conventional consolidation process. The plasma sintering results in starting-powder particle surface activation that enhances sinterability and reduces high temperature exposure. The sintering properties of beryllides were evaluated. Results show that intermetallic beryllide compounds such as Be12Ti, Be 17Ti2 and Be2Ti can be directly synthesized by the plasma sintering method from mixed elemental powders of Be and Ti at a temperature below the melting point. The preliminary characterization of plasma-sintered Be-Ti beryllide was carried out including examination of oxidation with water vapor, microstructure analysis, irradiation effects, and deuterium retention compared with beryllium (Be) metal. The preliminary characterization revealed that the plasma-sintered Be-Ti beryllide sample performs well as a neutron multiplier. This beryllide sample has better oxidation resistance, higher radiation resistance and lower deuterium retention than Be metal. © 2013 Elsevier B.V. All rights reserved.

Oxide formation and precipitation behaviors on interface of F82H steel joints during HIPing and hot pressing
Kishimoto, H., Ono, T., Sakasegawa, H., Tanigawa, H., Ando, M., Shibayama, T., Kohno, Y., Kohyama, A.
Journal of Nuclear Materials, 442, 1-3 SUPPL.1, S546, S551, 2013年, ［査読有り］
英語, 研究論文（学術雑誌）

Solution-phase Synthesis of Stannite-type Ag2ZnSnS4 Nanoparticles for Application to Photoelectrode Materials
Tetsuya Sasamura, Takaaki Osaki, Tatsuya Kameyama, Tamaki Shibayama, Akihiko Kudo, Susumu Kuwabata, Tsukasa Torimoto
CHEMISTRY LETTERS, 41, 9, 1009, 1011, CHEMICAL SOC JAPAN, 2012年09月, ［査読有り］
英語, 研究論文（学術雑誌）, Ag2ZnSnS4 (AZTS) nanoparticles were successfully synthesized at relatively low temperature via thermal reaction of corresponding metal acetates and a sulfur source in a hot oleylamine solution, the purity of the particles being dependent on the amount of metal acetates and the reaction temperature. The obtained pure AZTS particles with size of ca. 15 nm exhibited photoresponse with visible light irradiation similar to that of n-type semiconductors.

Study of the damage produced in 6H-SiC by He irradiation
B. S. Li, C. H. Zhang, H. H. Zhang, T. Shibayama, Y. T. Yang
VACUUM, 86, 4, 452, 456, PERGAMON-ELSEVIER SCIENCE LTD, 2011年11月, ［査読有り］
英語, 研究論文（学術雑誌）, Lattice damage and evolution in 6H-SiC under He ion irradiation have been investigated by the combination of Rutherford backscattering in channeling geometry (RBS/C), Raman spectroscopy, UV visible spectroscopy and transmission electron microscopy (TEM). 6H-SiC wafers were irradiated with He ions at a fluence of 3 x 10(16) He(+)cm(-2) at 600 K. Post-irradiation, the samples were annealed in vacuum at different temperatures from 873 K to 1473 K for isochronal annealing (30 min). Thermally annealed He irradiated 6H-SiC exhibited an increase in damage or reverse annealing behavior in the damage peak region. The reverse annealing effect was found due to the nucleation and growth of He bubbles. This finding was consistent with the TEM observation. The thermal annealing brought some recovery of lattice defects and therefore the intensities of Raman peaks increased and the absorption coefficient decreased with increasing annealing temperature. The intensity of Raman peak at 789 cm(-1) as a function of annealing temperature was fitted in terms of a thermally activated process which yielded activation energy of 0.172 +/- 0.003 eV. (C) 2011 Elsevier Ltd. All rights reserved.

Deuterium retention in F82H after low energy hydrogen ion irradiation
T. Ito, Y. Yamauchi, T. Hino, T. Shibayama, Y. Nobuta, K. Ezato, S. Suzuki, M. Akiba
JOURNAL OF NUCLEAR MATERIALS, 417, 1-3, 1147, 1149, ELSEVIER SCIENCE BV, 2011年10月, ［査読有り］
英語, 研究論文（学術雑誌）, The influence of 50 eV hydrogen ion irradiation on the deuterium retention and desorption behavior in the reduced activation ferritic-martensitic steel F82H was investigated by thermal desorption spectroscopy. The amount of retained deuterium in the hydrogen irradiated F82H was up to 10 times larger than without the hydrogen irradiation. In the F82H irradiated by the low energy hydrogen ions at 300 and 523 K. the desorption peak of deuterium was shifted to lower temperatures than for samples unirradiated or irradiated at 773 K. In the F82H irradiated by hydrogen at 773 K, the amount of retained deuterium decreased compared to materials irradiated at 300 or 523 K. (C) 2011 Elsevier B.V. All rights reserved.

Micro-chemical analysis of diffusion bonded W-SiC joint
Genichiro Matsuo, Tamaki Shibayama, Hirotatsu Kishimoto, Kouichi Hamada, Seiichi Watanabe
JOURNAL OF NUCLEAR MATERIALS, 417, 1-3, 391, 394, ELSEVIER SCIENCE BV, 2011年10月, ［査読有り］
英語, 研究論文（学術雑誌）, W and SiC joining has an attractive feature for high-temperature energy conversion systems. However, it is unclear and that is necessary to study the microstructure of the reaction phase between W and SIC by using the thermal diffusion bonding method. This work demonstrates the strengthening mechanism of W and SiC joining through a microstructure analysis of the reaction phase by FE-TEM/EDS and the observation of the interface in W and SiC after the crack propagation in HVEM. The reaction phase was amorphous, with a gap from 500 to 600 nm between W and SiC. Fine precipitates with a diameter of several tens nanometer were formed in the reaction phase. The reaction phase and precipitates did not match the chemical composition of the equilibrium compound. It is conceivable that the reaction phase and precipitates exist as a non-equilibrium condition before they reach equilibrium condition. (C) 2011 Elsevier B.V. All rights reserved.

Microstructural and mechanical characterization of W/SiC bonding for structural material in fusion
H. Kishimoto, T. Shibayama, K. Shimoda, T. Kobayashi, A. Kohyama
JOURNAL OF NUCLEAR MATERIALS, 417, 1-3, 387, 390, ELSEVIER SCIENCE BV, 2011年10月, ［査読有り］
英語, 研究論文（学術雑誌）, The SiC/SiC composites are expected to be employed as structural materials in fusion reactors after DEMO. Tungsten may be used as armor material of divertor to protect from the high temperature heat flux. An advanced SiC/SiC composite, NITE SiC/SiC, has excellent resistance to high stress and temperature, and diffusion and sinter bonding methods using high temperature are able to join SiC/SiC composites. This work evaluates the microstructure of interphases when tungsten is joined to SiC to screen potential bonding techniques. The W/SiC joints were produced by diffusion bonding, sinter bonding and liquid phase sinter bonding methods using the hot-pressing methods. Evaluation by SEM, EPMA, TEM and shear test showed the promise of these bonding methods. (C) 2010 Elsevier B.V. All rights reserved.

Helium retention and surface morphology of oxidized vanadium alloy
Y. Yamauchi, D. Oku, T. Hino, T. Shibayama, Y. Nobuta, T. Nagasaka, T. Muroga
JOURNAL OF NUCLEAR MATERIALS, 417, 1-3, 327, 329, ELSEVIER SCIENCE BV, 2011年10月, ［査読有り］
英語, 研究論文（学術雑誌）, The effects of the surface oxidation on the helium desorption and retention behaviors of vanadium alloy were investigated. V-4Cr-4Ti alloy, which was thermally oxidized at 873 K for 15 min with 0.05 Pa, was irradiated by helium ions with energy of 5 key at room temperature. Then, the helium desorption and retention behaviors were evaluated using a technique of thermal desorption spectroscopy. The changes in surface structures by the irradiation were also evaluated. Helium desorption behavior in low temperature region were significantly changed by the oxidation. Helium desorption around 700 K became large for the oxidized sample. The amount of retained helium and the blister size in the oxidized sample were smaller than of those in the non-oxidized one. These results indicate that the surface oxidation significantly affects the helium retention and desorption behaviors of the vanadium alloy. (C) 2010 Elsevier B.V. All rights reserved.

In situ observation, of damage structure in ODS austenitic steel during electron irradiation
H. Oka, M. Watanabe, H. Kinoshita, T. Shibayama, N. Hashimoto, S. Ohnuki, S. Yamashita, S. Ohtsuka
JOURNAL OF NUCLEAR MATERIALS, 417, 1-3, 279, 282, ELSEVIER SCIENCE BV, 2011年10月, ［査読有り］
英語, 研究論文（学術雑誌）, The oxide dispersion strengthening method was applied to an austenitic stainless steel based on SUS316 by mechanical alloying with additions of minor alloying elements. This ODS austenitic stainless steel was electron-irradiated to investigate the damage structure. Microstructural observation revealed that ODS austenitic stainless steel has a fine distribution of complex oxides. The in situ observation during electron irradiation showed that both dislocation loops and small cavities nucleated at the interface between oxide particles and matrix. In the case of helium implantation, defect clusters also nucleated at the interface. These results suggest that the oxide interface is an effective sink for irradiation-induced point defects and helium atoms. (C) 2010 Elsevier B.V. All rights reserved.

In-situ Observation of Fracture Behavior on Nano Structure in NITE SiC/SiC Composite by HVEM
Tamaki Shibayama, Genichiro Matsuo, Kouichi Hamada, Seiichi Watanabe, Hirotatsu Kishimoto
3RD INTERNATIONAL CONGRESS ON CERAMICS (ICC3): CERAMICS AND COMPOSITES FOR ADVANCED NUCLEAR ENERGY AND HAZARDOUS WASTE TREATMENT APPLICATIONS, 18, IOP PUBLISHING LTD, 2011年, ［査読有り］
英語, 研究論文（国際会議プロシーディングス）, We have been successfully done in situ observation on the sequence of fracture event at the interface of NITE SiC/SiC composite examined by using miniaturized double notched shear specimen for TEM prepared by Focused Ion Beam method. In this study, we used nano-mechanics TEM experimental apparatus to investigate not only microstructure evolution and but also load and displacement curve at once in High Voltage Electron Microscope. Our results summarize as follows. Cracks were initiated at the interface between carbon coating layer on the SiC fiber and SiC matrices, and propagated along the interface. Load drop in the load and displacement curve during in-situ TEM was clearly observed at the crack initiation. The shear strength by using the miniaturized specimen is about ten times higher than that obtained by the standard testing.

Diffusion Bonding Technology of Tungsten and SiC/SiC Composites for Nuclear Applications
Hirotatsu Kishimoto, Tamaki Shibayama, Takahiro Abe, Kazuya Shimoda, Satoshi Kawamura, Akira Kohyama
3RD INTERNATIONAL CONGRESS ON CERAMICS (ICC3): CERAMICS AND COMPOSITES FOR ADVANCED NUCLEAR ENERGY AND HAZARDOUS WASTE TREATMENT APPLICATIONS, 18, IOP PUBLISHING LTD, 2011年, ［査読有り］
英語, 研究論文（国際会議プロシーディングス）, Silicon carbide (SiC) is a candidate for the structural material in the next generation nuclear plants. Use of SiC/SiC composites is expected to increase the operation temperature of system over 1000 degrees C. For the high temperature system, refractory metals are planned to be used for several components. Tungsten is a candidate of armor on the divertor component in fusion, and is planned to be used for an upper-end plug of SiC/SiC fuel pin in a Gas cooled Fast Reactor (GFR). Joining technique of the SiC/SiC composites and tungsten is an important issue for nuclear systems in future. Nano-Infiltration and Transient Eutectoid (NITE) method is able to provide dense stable and high strength SiC/SiC composites having high resistance against pressure at elevated temperature, a diffusion bonding technique is usable to join the materials. Present research produces a NITE-SiC/SiC composite and tungsten as the similar dimension as a projected cladding tube of fuel pin for GFR using diffusion bonding, and investigated microstructure and mechanical properties.

Fabrication of Transition Metal Oxide Nanoparticles Highly Dispersed in Ionic Liquids by Sputter Deposition
Toshimasa Suzuki, Shushi Suzuki, Yousuke Tomita, Ken-ichi Okazaki, Tamaki Shibayama, Susumu Kuwabata, Tsukasa Torimoto
CHEMISTRY LETTERS, 39, 10, 1072, 1074, CHEMICAL SOC JAPAN, 2010年10月, ［査読有り］
英語, 研究論文（学術雑誌）, Sputter deposition of transition metals W, Mo, Nb, and Ti into ionic liquids (ILs) produced corresponding metal oxide nanoparticles (NPs) smaller than 6 nm The NPs were obtained in a highly dispersed manner without any additional stabilizing agent in ILs

Nanosize-Controlled Syntheses of Indium Metal Particles and Hollow Indium Oxide Particles via the Sputter Deposition Technique in Ionic Liquids
Toshimasa Suzuki, Ken-ichi Okazaki, Shushi Suzuki, Tamaki Shibayama, Susumu Kuwabata, Tsukasa Torimoto
CHEMISTRY OF MATERIALS, 22, 18, 5209, 5215, AMER CHEMICAL SOC, 2010年09月, ［査読有り］
英語, 研究論文（学術雑誌）, Sputter deposition of indium (In) in ionic liquids (ILs) could produce stable In metal nanoparticles whose surface was covered by an amorphous In2O3 layer to form In/In2O3 core/shell particles. The size of the In core was tunable from ca. 8 to 20 nm by selecting the kind of IL, whereas the shell thickness of In2O3 was almost constant at ca. 1.9 nm. Heat treatment of the thus-obtained particles at 523 K in air oxidized In metal of the core, resulting in the formation of spherical hollow particles made of crystalline In2O3. The size of the hollow particles was slightly larger than that of the In/In2O3 core/shell particles used as a starting material, whereas the void space formed inside hollow particles was smaller than the corresponding In metal cores. These facts indicated that in addition to the predominant outward diffusion of In ions, an inward transport of oxygen ions occurred, and thus an In2O3 crystal could be grown on both the inner concave and outer convex surfaces of the oxide shell layer.

Highly Active Titania Photocatalyst Particles of Controlled Crystal Phase, Size, and Polyhedral Shapes
Fumiaki Amano, Taikei Yasumoto, Orlando Omar Prieto Mahaney, Satoshi Uchida, Tamaki Shibayama, Yoshihiro Terada, Bunsho Ohtani
TOPICS IN CATALYSIS, 53, 7-10, 455, 461, SPRINGER/PLENUM PUBLISHERS, 2010年06月, ［査読有り］
英語, 研究論文（学術雑誌）, Mesoscopic crystalline anatase particles of titanium(IV) oxide (titania) with decahedral morphology and with octahedral morphology were synthesized by gas-phase reaction of titanium(IV) chloride with oxygen and hydrothermal reaction of titanate nanowires in an alkaline medium, respectively, and their photocatalytic activities in relation with their crystal morphology were investigated.

Mechanical properties and microstructural stability of 11Cr-ferritic/martensitic steel cladding under irradiation
Yasuhide Yano, Shinichiro Yamashita, Satoshi Ohtsuka, Takeji Kaito, Naoaki Akasaka, Tamaki Shibayama, Seiichi Watanabe, Heishichiro Takahashi
JOURNAL OF NUCLEAR MATERIALS, 398, 1-3, 59, 63, ELSEVIER SCIENCE BV, 2010年03月, ［査読有り］
英語, 研究論文（学術雑誌）, The in-reactor creep rupture tests of 11Cr-0.5Mo-2W, V. Nb F/M steel were carried out in the temperature range from 823 to 943 K using materials open test assembly in the fast flux test facility and tensile and temperature-transient-to-burst specimens were irradiated in the experimental fast reactor JOYO at temperatures between 693 and 1013 K to fast neutron doses ranging from 11 to 102 dpa. The results of post-irradiation mechanical tests showed that there was no significant degradation in tensile and transient burst strengths even after neutron irradiation below 873 K, but that there was significant degradation in both strengths at neutron irradiation above 903 K. On the other hand, the in-reactor creep rupture times were equal or greater than those of out-reactor creep even after neutron irradiation at all temperatures. This creep rupture behavior was different from that of tensile and transient burst specimens. (C) 2009 Elsevier B.V. All rights reserved.

Preparation and photoelectrochemical properties of densely immobilized Cu2ZnSnS4 nanoparticle films
Tatsuya Kameyama, Takaaki Osaki, Ken-ichi Okazaki, Tamaki Shibayama, Akihiko Kudo, Susumu Kuwabata, Tsukasa Torimoto
JOURNAL OF MATERIALS CHEMISTRY, 20, 25, 5319, 5324, ROYAL SOC CHEMISTRY, 2010年, ［査読有り］
英語, 研究論文（学術雑誌）, Colloidal Cu2ZnSnS4 (CZTS) nanoparticles with sizes of 5-6 nm that contain no highly toxic elements were successfully synthesized through thermal reactions of metal acetate and sulfur in high-temperature oleylamine solution. The reaction temperature was a key factor for the synthesis of CZTS nanoparticles: synthesis at temperatures higher than 240 degrees C gave a pure CZTS crystal phase, whereas a secondary phase of CuS was formed at reaction temperatures lower than 180 degrees C. Nanoparticles were successfully accumulated on ITO-coated or quartz glass substrates via layer-bylayer deposition using 1,2-ethanedithiol as a cross-linking agent. The resulting CZTS particle films exhibited a photoresponse similar to that of p-type semiconductor photoelectrodes in an aqueous solution containing Eu(NO3)(3) as an electron scavenger. Potentials of the valence band edge and conduction band edge were determined from the onset potential of the cathodic photocurrent to be +0.3 and -1.2 V vs. Ag/AgCl, respectively.

Remarkable photoluminescence enhancement of ZnS-AgInS2 solid solution nanoparticles by post-synthesis treatment
Tsukasa Torimoto, Shoji Ogawa, Tomohiro Adachi, Tatsuya Kameyama, Ken-ichi Okazaki, Tamaki Shibayama, Akihiko Kudo, Susumu Kuwabata
CHEMICAL COMMUNICATIONS, 46, 12, 2082, 2084, ROYAL SOC CHEMISTRY, 2010年, ［査読有り］
英語, 研究論文（学術雑誌）, The photoluminescence intensity of ZnS-AgInS2 solid solution nanoparticles was remarkably enhanced by increasing the heating temperature to 180 degrees C, above which the emission was simply diminished, while ZnS coating of the particles resulted in further enhancement of PL intensity, giving the highest quantum yield of ca. 80%.

Highly Active Titania Photocatalyst Particles of Controlled Crystal Phase, Size, and Polyhedral Shapes
B. Ohtani, F. Amano, T. Yasumoto, O. O. Prieto-Mahaney, S. Uchida, T. Shibayama, Y. Terada
PROCEEDINGS OF THE 6TH EUROPEAN MEETING ON SOLAR CHEMISTRY & PHOTOCATALYSIS: ENVIRONMENTAL APPLICATIONS, 49, 50, ICT PRESS, 2010年, ［査読有り］
英語, 研究論文（国際会議プロシーディングス）

Decahedral Single-Crystalline Particles of Anatase Titanium(IV) Oxide with High Photocatalytic Activity
Fumiaki Amano, Orlando-Omar Prieto-Mahaney, Yoshihiro Terada, Taikei Yasumoto, Tamaki Shibayama, Bunsho Ohtani
CHEMISTRY OF MATERIALS, 21, 13, 2601, 2603, AMER CHEMICAL SOC, 2009年07月, ［査読有り］
英語, 研究論文（学術雑誌）

Nanowire-structured titanate with anatase titania: Characterization and photocatalytic activity
Fumiaki Amano, Taikei Yasumoto, Tamaki Shibayama, Satoshi Uchida, Bunsho Ohtani
APPLIED CATALYSIS B-ENVIRONMENTAL, 89, 3-4, 583, 589, ELSEVIER SCIENCE BV, 2009年07月, ［査読有り］
英語, 研究論文（学術雑誌）, Nanowire-structured titanate with titanium(IV) oxide (titania) was obtained by calcination of potassium ion-containing titanate nanowires prepared through alkali treatment of titania nanoparticles. The presence of potassium ions in the as-synthesized titanate nanowires was required for maintenance of the nanowire structure under the conditions of post-heat treatment. The crystallite structure, composition, morphology, specific surface area, pore volume distribution, and optical properties were found to be dependent on the temperature at which titanate nanowires were calcined. Photocatalytic activity was examined using three probe reactions: oxidative decomposition of acetic acid in an aqueous solution, oxygen liberation from an aqueous silver sulfate solution, and hydrogen liberation from an aqueous methanol solution in the presence of hexachloroplatinic acid as a precursor of photodeposition of platinum particles. Detailed characterization and results of photocatalytic activity tests revealed that titanate crystallites greatly contributed to the photocatalytic activities of the calcined nanowires except for photocatalytic hydrogen liberation. It was found that platinum was preferentially photodeposited on anatase crystallites rather than on titanate crystallites for hydrogen liberation. (C) 2009 Elsevier B.V. All rights reserved.

Photocatalytic activity of octahedral single-crystalline mesoparticles of anatase titanium(IV) oxide
Fumiaki Amano, Taikei Yasumoto, Orlando-Omar Prieto-Mahaney, Satoshi Uchida, Tamaki Shibayama, Bunsho Ohtani
CHEMICAL COMMUNICATIONS, 17, 2311, 2313, ROYAL SOC CHEMISTRY, 2009年, ［査読有り］
英語, 研究論文（学術雑誌）, Octahedral titanium(IV) oxide (TiO(2)) crystallites with exposed anatase {101} facets exhibited relatively high photocatalytic activity for oxidative decomposition of organic compounds and low activity for hydrogen evolution in the absence of molecular oxygen, probably due to the characteristics of the anatase {101} surface.

Photochemical Shape Control of Cadmium Sulfide Nanorods Coated with an Amorphous Silica Thin Layer
Tsukasa Torimoto, Masayuki Hashitani, Takahito Konishi, Ken-ichi Okazaki, Tamaki Shibayama, Bunsho Ohtani
JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 9, 1, 506, 513, AMER SCIENTIFIC PUBLISHERS, 2009年01月, ［査読有り］
英語, 研究論文（学術雑誌）, The surface of cadmium sulfide nanorods was modified by 3-mercaptopropyltrimethoxysilane, followed by the hydrolysis of trimethoxysilyl groups to form a silica shell structure (SiO2/CdS[rod]). Size-selective photoetching was applied to SiO2/CdS[rod] to modify the size of the CdS rod core. The absorption spectra were blue-shifted by irradiation of monochromatic light, and finally absorption onset agreed with the wavelength of irradiation light. These facts indicated that CdS rod particles were photoetched to smaller ones until the irradiated photons were no longer absorbed by the photoetched particles and that the SiO2 shell layer surrounding the CdS rod core prevented coalescence between photoetched particles. Changes in the wavelength of irradiation light from 488 to 436 nm caused a decrease in rod width from 3.5 to 2.3 nm along with remarkable decrease in the length of rod from 14 to 4.2 nm, suggesting that the photoetching rate was dependent on the kind of crystal faces and that the photocorrosion reactions at the tips of the CdS rod, that is, on (001) and/or (00 (1) over bar) faces, were faster than those on other faces that appeared on the sides of the rod. This technique enabled control of CdS rod shape by selecting the wavelength of irradiation light.

SUS301鋼におけるイオン注入によるマルテンサイト核形成
木下博嗣, 高橋平七郎, Dwi Gustiono, 坂口紀史, 柴山環樹, 渡辺精一
日本金属学会誌, 72, 8, 631, 636, 2008年08月, ［査読有り］
日本語, 研究論文（学術雑誌）, Phase transformation behaviors of the austenitic 301 stainless steel was studied under Fe+, Ti+ and Ar+ ions implantation at room temperature with 100, 200 and 300 keV up to fluence of 1 × 1021 ions/m2 and the microstructures were observed by means of transmission electron microscopy (TEM). The plane and cross-sectional observations of the implanted specimen showed that the induced-phases due to implantation from the γ matrix phase were identified as α′ martensite phases with the orientation relationship of (11̄0)α//(111̄)γ and [111] α//[011]γ close to the Kurdjumov-Sachs (K-S). The ion implantation induced phases nucleated near the surface region and the depth position of the nucleation changed depending on the ion accelerating energy and ion species. It was also found that the induced marten sites phases nucleate under the influence of the stress distribution, which is introduced due to the concentration of implanted ions, especially due to the stress gradient caused by the corresponding concentration gradient. © 2008 The Japan Institute of Metals.

ナノ粒子分散強化オーステナイト鋼の創成の基礎研究:照射欠陥クラスター形成に及ぼすナノ粒子分散の効果
山下 真一郎, 大塚 智史, 渡部 雅, 内多 陽介, 須田 孝徳, 橋本 直幸, 大貫 惣明, 柴山 環樹
日本原子力学会 年会・大会予稿集, 2008, 0, 428, 428, 一般社団法人 日本原子力学会, 2008年
日本語, 我々のグループでは、耐照射性、耐熱性に優れる改良型オーステナイト系ステンレス鋼に対して、酸化物分散強化型フェライト鋼の製造で用いられる機械的合金法と熱処理を適用し、熱力学的に安定なナノサイズ粒子を母相中に分散させた先進オーステナイト鋼の試作を行っている。ナノサイズ粒子の効果としては、中性子照射下における点欠陥の消滅サイト、あるいは転位運動に対するオブスタクルとしての作用を期待している。本研究では、アトライター式ボールミルを用いて改良型オーステナイト系ステンレス（PNC316）鋼金属粉末と酸化物粒子を機械的に合金化した材料に対し、高速実験炉「常陽」で中性子照射し、照射特性を評価した結果について報告する。本研究では、特に照射欠陥クラスター形成に及ぼすナノサイズ粒子の効果について着目する。

Facile synthesis of ZnS-AgInS2 solid solution nanoparticles for a color-adjustable luminophore
Tsukasa Torimoto, Tomohiro Adachi, Ken-ichi Okazaki, Miwa Sakuraoka, Tamaki Shibayama, Bunsho Ohtani, Akihiko Kudo, Susumu Kuwabata
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 129, 41, 12388, +, AMER CHEMICAL SOC, 2007年10月, ［査読有り］
英語, 研究論文（学術雑誌）, Nanoparticles of ZnS-AgInS2 solid solution (ZAIS) were synthesized by the thermal decomposition of (AgIn)(x) Zn2(1-x)(S2CN(C2H5)(2)) 4 precursors in a hot oleylamine solution. X-ray powder diffraction analyses revealed that the resulting nanoparticle powders were not a mixture of ZnS and AgInS2 but a ZnS-AgInS2 Solid solution in which the fraction of ZnS was enlarged with a decrease in the value of x, that is, an increase in the content of Zn2+ in the precursors used. The energy gap of ZAIS nanoparticles could be controlled by the composition of solid solution. Intense emission was observed at room temperature, regardless of the kind of the particles, the peak wavelength of PL being blue-shifted from 720 to 540 nm with a decrease in the value of x. The highest quantum yield of ca. 24% was obtained for nanoparticles prepared with x = 0.86, which was much higher than the quantum yields reported for I-III-VI2-based semiconductor nanoparticles, such as CuInS2 and ZnS-CuInS2 solid solution.

Recent results on beryllium and beryllides in Japan
Y. Mishima, N. Yoshida, H. Kawamura, K. Ishida, Y. Hatano, T. Shibayama, K. Munakata, Y. Sato, M. Uchida, K. Tsuchiya, S. Tanaka
JOURNAL OF NUCLEAR MATERIALS, 367, B, 1382, 1386, ELSEVIER SCIENCE BV, 2007年08月, ［査読有り］, ［招待有り］
英語, 研究論文（学術雑誌）, Recently, several research and development (R&D) programs of beryllium and its alloys for fusion reactor application have been conducted in Japan and the community of beryllium research has grown. In the R&D area of beryllium technology for a solid breeding blanket, a major subject is applications of beryllides, for which lifetime evaluation as neutron multiplier, impurity effect on irradiation behavior and recycling of irradiated materials are under investigation. As for neutron multiplier materials, recent R&D has focused on Be-Ti alloys based on Be12Ti as an advanced option, because of their superior properties compared with beryllium metal in such respects as compatibility with structural materials and oxidation resistance at higher temperatures. In this paper, recent results on beryllide R&D in Japan are described. (C) 2007 Elsevier B.V. All rights reserved.

Combustion synthesis of TiO2 nanoparticles as photocatalyst
Yasuaki Kitamura, Noriyuki Okinaka, Tamaki Shibayama, Orlando Omar Prieto Mahaney, Daisuke Kusano, Bunsho Ohtani, Tomohiro Akiyama
POWDER TECHNOLOGY, 176, 2-3, 93, 98, ELSEVIER SCIENCE SA, 2007年07月, ［査読有り］
英語, 研究論文（学術雑誌）, This paper describes a new type of combustion synthesis of metal oxide nanoparticles, in which the adiabatic flame temperature of the solid phase reaction is beyond the boiling point of the product, and its implementation for the synthesis of titanium dioxide as photocatalyst. In this study, raw materials comprising titanium particles of different sizes and sodium perchlorate were intensively mixed and ignited by an electrical heating foil to produce titanium dioxide through the following reaction: Ti+NaClO4 -> TiO2+NaCl. The shape and crystal structure of the titanium dioxide product significantly depended on the particle size of the titanium used as raw material. That is, the smaller titanium particles (average size (AS) of 10 mu m) resulted in rutile with an irregular shape, whereas the larger particles (AS of 25 gm) resulted in spheres of anatase. The photocatalytic activities of these samples were evaluated using the photocatalytic reactions of aqueous titanium dioxide suspensions containing methanol and acetic acid by irradiation at 298 K in argon atmosphere or in air. The activity of the rutile-rich sample was significantly larger than that of the anatase-rich one in both photocatalytic reactions. (c) 2007 Elsevier B.V. All rights reserved.

Controlled formation of metallic nanoballs during plasma electrolysis
Yu Toriyabe, Seiichi Watanabe, Shigeo Yatsu, Tamaki Shibayama, Tadahiko Mizuno
APPLIED PHYSICS LETTERS, 91, 4, 041501-1, 041501-3, AMER INST PHYSICS, 2007年07月, ［査読有り］
英語, 研究論文（学術雑誌）, Formation of spherical nanoparticles (hereafter "nanoballs") in a gas/liquid mixed dual phase system during plasma electrolysis is reported. A gas/vapor sheath is formed at the electrode/electrolyte interface when the applied voltage is high enough to induce discharge plasma. Through this nonequilibrium process, the authors have produced Ni, Ti, Ag, and Au metallic nanoballs from the cathode mother materials with a certain size controllability. The electrode surface is partially melted by the local current concentration induced by electrothermal instability followed by an immediate cooldown, yielding nanoballs without contamination from electrolyte.

Ion implantation induced martensite nucleation in SUS301 steel
Hiroshi Kinoshita, Heishichiro Takahashi, Dwi Gustiono, Norihito Sakaguchi, Tamaki Shibayama, Seiichi Watanabe
MATERIALS TRANSACTIONS, 48, 5, 924, 930, JAPAN INST METALS, 2007年05月, ［査読有り］
英語, 研究論文（学術雑誌）, Phase transformation behaviors of the austenitic 301 stainless steel was studied under Fe+, Ti+ and Ar+ ions implantation at room temperature with 100, 200 and 300 keV up to fluence of 1 x 10(21) ions/m(2) and the microstructures were observed by means of transmission electron microscopy (TEM). The plane and cross-sectional observations of the implanted specimen showed that the induced-phases due to implantation from the gamma matrix phase were identified as alpha' martensite phases with the orientation relationship of (1 (1) over bar0)(alpha) //(11 (1) over bar)gamma and [111](alpha) // [011](gamma) close to the Kurdjumov-Sachs (K-S). The ion implantation induced phases nucleated near the surface region and the depth position of the nucleation changed depending on the ion accelerating energy and ion species. It was also found that the induced marten sites phases nucleate under the influence of the stress distribution, which is introduced due to the concentration of implanted ions, especially due to the stress gradient caused by the corresponding concentration gradient.

Microstructural evolution in silicon implanted with chlorine ions
C. H. Zhang, T. Shibayama, Y. F. Jin, Y. T. Yang, L. H. Zhou, Y. Song
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 256, 1, 272, 275, ELSEVIER SCIENCE BV, 2007年03月, ［査読有り］
英語, 研究論文（学術雑誌）, In the present work p-type Si specimens were implanted with Cl ions of 100 keV to successively increasing fluences of 1 x 10(15), 5 x 10(15), 1 x 10(16) and 5 x 10(16) ions cm(-2) and subsequently annealed at 1073 K for 30 min.
The microstructure was investigated with the transmission electron microscopy (TEM) in both the plane-view and the cross-sectional view. The implanted layer was amorphized after chlorine implantation even at the lowest ion fluence, while re-crystallization of the implanted layer occurs on subsequent annealing at 1073 K. In the annealed specimens implanted above the lowest fluence three layers along depth with different microstructures were found, which include a shallow polycrystalline porous layer, a deeper single-crystalline layer containing high density of gas bubbles, a well separated deeper layer composed of dislocation loops in low density. With increasing ion fluence the thickness of the porous polycrystalline layer increases. It is indicated that chlorine can suppress the epitaxial re-crystallization of implanted silicon, when the implant fluence of Cl ions exceeds a certain level. (c) 2006 Elsevier B.V. All rights reserved.

Defect production in silicon carbide irradiated with Ne and Xe ions with energy of 2.3 MeV/amu
C. H. Zhang, Y. M. Sun, Y. Song, T. Shibayama, Y. F. Jin, L. H. Zhou
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 256, 1, 243, 247, ELSEVIER SCIENCE BV, 2007年03月, ［査読有り］
英語, 研究論文（学術雑誌）, In the present work specimens of mono-crystalline silicon carbide (4H polytype) were irradiated to three successively increasing ion fluences ranging from 7.2 x 10(14) to 6.0 x 10(16) ions/cm(2) (corresponding to the peak displacement damage of 1, 4 and 13 dpa) with Ne and Xe ions respectively with the energy of 2.3 MeV/amu. The irradiated specimens were subsequently annealed at temperatures of 1173 and 1273 K. Defect structure was investigated with transmission electron microscopy (TEM) using a cross-sectional specimen preparation technique.
The typical microstructures of the annealed specimens irradiated with Ne or Xe ions to high fluences are characterized by small gas bubbles in high concentration in the peak damage region and black dots and dislocation loops (located in the basal plane) in a shallower and broader depth region. Larger dislocation loops were observed in the Xe-ion irradiated specimen than in the Ne-ion irradiated specimen at the same peak damage level. The enhanced formation of dislocation loops in the case of Xe-ion irradiation is understandable by assuming stronger inclination of heavier inert-gas atoms to occupy substitute site in the peak damage region. (c) 2006 Elsevier B.V. All rights reserved.

Morphological investigations of disaccharide molecules for growth inhibition of ice crystals
Tsutomu Uchida, Masafumi Nagayama, Tamaki Shibayama, Kazutoshi Gohara
JOURNAL OF CRYSTAL GROWTH, 299, 1, 125, 135, ELSEVIER SCIENCE BV, 2007年02月, ［査読有り］
英語, 研究論文（学術雑誌）, Freezing of solutions including disaccharides (trehalose, sucrose, and maltose) has been investigated by microscopic observations of freeze-fractured replicas using FE-TEM. Three typical features were observed: the smooth surface considered as the ice crystal, fine particles as the precipitated disaccharide molecules, and remaining part as the glass state of the solution. The expanded observations of fine particle and its distribution investigations suggested that it was larger than 10 nm in size and averaged approximately 20-30 nm in diameter. The smallest particle was estimated to include several hundred disaccharide molecules. Based on systematic observations of trehalose solutions regarding concentrations and freezing rates, we concluded that ice crystal growth was inhibited by trehalose molecules. Since the ice crystal size reduced exponentially with increase in trehalose concentration, we could control ice crystal size formed in the frozen material. The growth inhibition of ice crystals with trehalose resulted both from a reduction in the free water in the solution due to a significant hydration effect and from an enhancement of nucleation of the ice crystals. It was confirmed that trehalose was more effective than the other disaccharide solutions examined for inhibiting the growth of ice crystals. (c) 2006 Elsevier B.V. All rights reserved.

Tip artifact in atomic force microscopy observations of InAs quantum dots grown in Stranski–Krastanow mode
K. Shiramine, S. Muto, T. Shibayama, N. Sakaguchi, H. Ichinose, T. Kozaki, S. Sato
Journal of Applied Physics, 101, 3, 033527, AMER INST PHYSICS, 2007年02月, ［査読有り］
英語, 研究論文（学術雑誌）, The tip artifact in atomic force microscopy (AFM) observations of InAs islands was evaluated quantitatively. The islands were grown in the Stranski-Krastanow mode of molecular beam epitaxy. The width and height of the islands were determined using transmission electron microscopy (TEM) and AFM. The average [ (1) over bar 10] in-plane width and height determined using TEM excluding native oxide were 22 and 7 nm, respectively; those determined using AFM including the oxide were 35 and 8 nm, respectively. The difference in width was due to the oxide and the tip artifact. The sizes including the oxide were deduced from TEM observations to be a width of 27 nm and a height of 6 nm with correction for the thickness of the oxide. The residual difference of 8 nm between the width determined using AFM and that determined using TEM including the oxide was ascribed to the tip artifact. The results enable us to determine the actual size of the islands from their AFM images. (c) 2007 American Institute of Physics.

Present status of beryllides for fusion and industrial applications in Japan
Yoshinao Mishima, Naoaki Yoshida, Heishichiro Takahashi, Kiyohito Ishida, Hiroshi Kawamura, Takaharu Iwadachi, Tamaki Shibayama, Ikuo Ohnuma, Yoshiyuki Sato, Kenzo Munakata, Hirotomo Iwakiri, Munenori Uchida
FUSION ENGINEERING AND DESIGN, 82, 1, 91, 97, ELSEVIER SCIENCE SA, 2007年01月, ［査読有り］
英語, 研究論文（学術雑誌）, Beryllides have remarkable characteristics besides their low density, such as high radiation resistance, high chemical stability, low hydrogen isotope retention and good high temperature mechanical strength especially for fusion applications. In order to have a practical usage for industrial applications, it is important to compile a set of quantitative data on such properties. It is also important to develop fabrication and processing paths to assure the processing of inherently brittle beryllides. The characterization and manufacturing technologies development have been carried out mainly on the Be12Ti interemetallic compounds at the Be-rich side of the Be-Ti binary system. In the present paper, up-dated results on several properties are described for the compound fabricated by hot isostatic pressing (HIP) and ingot metallurgy. Mechanical properties of the compounds having a duplex microstructure with neighboring phases are evaluated by compressive tests from room temperature to 1273 K. Radiation damage of the compound is preliminary studied by charged particle irradiation. Oxidation in air and the interaction with water vapor are evaluated. Thermal desorption of the deuterium is examined by using transmission electron microscopy (TEM) and thermal desorption spectrometry (TDS). Through these evaluations it seems that Be12Ti is superior as neutron multiplier with respect to pure Be metal. (c) 2006 Published by Elsevier B.V.

Heterodimeric particle assemblies: Preparation of anisotropically connected spherical silica particles via surface-bound gold nanoparticles
Akira Ohnuma, Ryu Abe, Tamaki Shibayama, Bunsho Ohtani
CHEMICAL COMMUNICATIONS, 33, 3491, 3493, ROYAL SOC CHEMISTRY, 2007年, ［査読有り］
英語, 研究論文（学術雑誌）, Assemblies of heterodimeric particles were prepared through selective coupling of two kinds of spherical silica particles of different sizes by connection with gold nanoparticles attached anisotropically to the particles.

Interface properties of copper/aluminum/stainless steel clad materials
Dong-Su Bae, Soon-Kook Kim, Sang-Pill Lee, Tamaki Shibayama, Dong-Hyun Bae
MECHANICAL BEHAVIOR OF MATERIALS X, PTS 1AND 2, 345-346, 1497, +, TRANS TECH PUBLICATIONS LTD, 2007年, ［査読有り］
英語, 研究論文（国際会議プロシーディングス）, Copper/aluminum/stainless steel (Cu/Al/STS) clad materials were made by rolling and heat treatment process. These specimens were evaluated the formability and bonding strength of Cu/Al/STS clad materials. Thin disc specimens for TEM observation were prepared from the interfaces of Cu/Al and Al/STS by using the Focused Ion Beam (FIB) utility. Brittle oxide film formed on copper surface during heat treatment at 673K similar to 773K. Diffusion bonding was observed at the interface of Cu/Al. Reacted region was formed in the interface of Al/STS with width about 10nm, while in the case of Cu/Al was formed about 1,600nm width. It was also observed nano-sized crevice in reacted region of Al/STS interfaces.

Photochemical fine-tuning of luminescent color of cadmium selenide nanoparticles: Fabricating a single-source multicolor luminophore
Tsukasa Torimoto, Shin-ya Murakami, Miwa Sakuraoka, Kentaro Iwasaki, Ken-ichi Okazaki, Tamaki Shibayama, Bunsho Ohtani
JOURNAL OF PHYSICAL CHEMISTRY B, 110, 27, 13314, 13318, AMER CHEMICAL SOC, 2006年07月, ［査読有り］
英語, 研究論文（学術雑誌）, Size-selective photoetching was applied to silica-coated cadmium selenide (SiO2/CdSe) nanoparticles to precisely control their photoluminescence properties. The absorption spectra of CdSe was blue-shifted by irradiation of monochromatic light, and finally, the absorption onset agreed with the wavelength of irradiation light, indicating that CdSe particles were photoetched to smaller ones until the irradiated photons were not absorbed by the photoetched particles and that the SiO2 shell layer surrounding the CdSe core prevented coalescence between the photoetched particles. Although as-prepared SiO2/CdSe did not exhibit photoluminescence, the application of size-selective photoetching to SiO2/CdSe resulted in the development of the band gap emission, with the degree being enhanced with progress of the photoetching. The peak wavelength of photoluminescence decreased with a decrease in the wavelength used for the photoetching, so that the luminescence color could be tuned between red and blue. Partial photoetching of SiO2/CdSe nanoparticle films produced intense band gap emission of CdSe at the photoetched area, while the remainder of the SiO2/CdSe films did not exhibit detectable photoluminescence, resulting in the formation of a clear photoluminescence image under UV irradiation. This technique makes it possible to produce a multicolored photoluminescence image by irradiation with monochromatic lights having various wavelengths using a single source material.

Fabrication of jingle-bell-shaped core-shell nanoparticulate films and molecular-size-responsive photoluminescence quenching of cadmium sulfide cores
Kentaro Iwasaki, Tsukasa Torimoto, Tamaki Shibayama, Tomohiro Nishikawa, Bunsho Ohtani
SMALL, 2, 7, 854, 858, WILEY-V C H VERLAG GMBH, 2006年07月, ［査読有り］
英語, 研究論文（学術雑誌）

Growth structure and growth defects in pulsed laser deposited Cr-CrNx-CrCxN1-x multilayer coatings
JM Lackner, W Waldhauser, B Major, J Morgiel, L Major, H Takahashi, T Shibayama
SURFACE & COATINGS TECHNOLOGY, 200, 11, 3644, 3649, ELSEVIER SCIENCE SA, 2006年03月, ［査読有り］
英語, 研究論文（学術雑誌）, Chromium carbonitride (CrCxN1-x) coatings are becoming more and more interesting for wear protection applications due to their increased hardness and improved wear performance compared to chromium nitride (CrNx) hard coatings. Further improvements seem to be possible by using multilayer coatings of these two materials. In the current work such multilayer structures were deposited by the Pulsed Laser Deposition (PLD) technique at room temperature using an industrially designed 4-beam multi-spot PLD evaporator. The coatings were investigated by means of transmission electron microscopy (TEM) in order to solve their growth mechanisms and microstructure development. Due to the very high hardness and brittleness of the coatings, the TEM sample preparation has to be based on gallium focused ion beam cutting. Although the chemical analyses revealed a significant Ga atom contamination of the samples originating from the sample preparation, the face-centered cubic CrN-based phases and their textures, found in electron micro-diffraction analyses as well as in X-ray diffraction measurements, were scarcely influenced by the incorporated atoms. Great influences on the phase formation result from oxygen atom trapping from the rest gas atmosphere prior deposition. A very fine grained (2-5 nm) structure was found for the pure chromium adhesive interface layers, which are necessary for high adhesion of the hard coating layers. These hard ceramic layers-CrNx and CrCxN1-x-possess much coarser (8-15-nm grain size), micro-columnar structures. Furthermore, influences on the film growth are caused by defects on the substrate surface like cracks and contaminating dust particles. (c) 2005 Elsevier B.V. All rights reserved.

Effect of electron irradiation on microstructural damage in the welded portion of a SUS304 weldment
DS Bae, SK Kim, SP Lee, H Kinoshita, T Shibayama, H Takahashi
FUSION ENGINEERING AND DESIGN, 81, 8-14, 969, 974, ELSEVIER SCIENCE SA, 2006年02月, ［査読有り］
英語, 研究論文（学術雑誌）, The matrix and heat affected zone (HAZ) of welded SUS304 steel has been irradiated in an 1250 kV high voltage electron microscope at 673 K to 5.4 dpa (displacements per atom) to study the effect of electron irradiation on microstructure. In situ observation shows the voids formed by electron-beam irradiation coalescence which grew to larger sizes with irradiation dose. Values of void size, void number density and void swelling in HAZ were larger than those of the matrix, and these increased and saturated gradually with irradiation dose. Non-equilibrium segregation phenomenon involving Cr depletion and Ni enrichment at grain boundaries were also observed in both the HAZ and matrix of welded SUS304 steel. (c) 2005 Elsevier B.V. All rights reserved.

β-Ni(Al,Cr)合金に形成されるAl2O3 酸化皮膜の耐剥離性に及ぼすZr 添加の影響
東本英哲, 山内啓, 柴山環樹, 渡辺精一, 黒川一哉, 成田敏夫
プラズマ応用科, 14, 87, 93, プラズマ応用科学会, 2006年, ［査読有り］
日本語, 研究論文（学術雑誌）

Microstructures of SiO(2) scales formed on MoSi(2)
Kazuya Kurokawa, Daichi Goto, Jyunichi Kuchino, Akira Yamauchi, Tamaki Shibayama, Heishichiro Takahashi
HIGH-TEMPERATURE OXIDATION AND CORROSION 2005, 522-523, 595, 601, TRANS TECH PUBLICATIONS LTD, 2006年, ［査読有り］
英語, 研究論文（学術雑誌）, The microstructures of oxide scales formed on MOSi(2) at medium-high temperatures in air were observed by TEM. Based on the observation, relationships between oxidation temperature and formation of MoO(3) and crystallization of amorphous SiO(2) scales were investigated. At 1273 K and 1373 K, the oxide scales had a structure consisting of amorphous SiO(2) with small amounts of fine MoO(3) particles. The oxide scales at 1573 K and 1773 K had a structure consisting of amorphous and crystalline SiO(2). Growth rate of the oxide scale formed at 1773 K appreciably increased due to crystallization of amorphous SiO(2). It was thought that the increase in the oxidation rate at 1773 K was caused by a change in the diffusion mechanism from O(2) diffusion to lattice diffusion of O(2-) through SiO(2). In addition, the diffusion coefficient of oxygen was estimated from the growth rate Of SiO(2) scale.

凍結抑制物質の氷表面上における形態観測(2)
内田 努, 永山 昌史, 柴山 環樹, 郷原 一寿
日本雪氷学会全国大会講演予稿集, 2006, 61, 61, 公益社団法人 日本雪氷学会, 2006年
日本語

Photocatalytic preparation of encapsulated gold nanoparticles by jingle-bell-shaped cadmium sulfide-silica nanoparticles
B Pal, T Torimoto, S Ikeda, T Shibayama, K Sugawara, H Takahashi, B Ohtani
TOPICS IN CATALYSIS, 35, 3-4, 321, 325, SPRINGER/PLENUM PUBLISHERS, 2005年07月, ［査読有り］
英語, 研究論文（学術雑誌）, Gold (Au) nanoparticles were deposited inside silica: (SiO2) shells containing cadmium sulfide (CdS) nanoparticles through photocatalytic reduction of potassium dicyanogold(I) by CdS. Photocatalytic Au deposition occurred only when core-shell nanoparticles having a void space between the core and shell, i.e., a jingle-bell-shaped structure, were used. These core-shell nanoparticles were prepared by size-selective photoetching of SiO2 -covered CdS nanoparticles. The size of Au nanoparticles could be controlled by adjustment of the void space in SiO2-covered CdS. Dissolution of CdS by acid treatment from the Au-deposited jingle-bell nanoparticles did not have any effect on the surface-plasmon absorption by Au. These facts indicate that Au nanoparticles of adjustable size can be prepared in an SiO2 shell that prevents mutual coalescence of Au nanoparticles but allows permeation of molecules and ions.

Synthesis of metal-cadmium sulfide nanocomposites using jingle-bell-shaped core-shell photocatalyst particles
B Pal, T Torimoto, K Iwasaki, T Shibayama, H Takahashi, B Ohtani
JOURNAL OF APPLIED ELECTROCHEMISTRY, 35, 7-8, 751, 756, SPRINGER, 2005年07月, ［査読有り］
英語, 研究論文（学術雑誌）, Photocatalytic deposition of gold (Au) and silver (Ag) nanoparticles was investigated using jingle-bell-shaped silica (SiO(2))-coated cadmium sulfide (CdS) nanoparticles (SiO(2)/CdS), which each had a void space between the CdS core and SiO(2) shell, as a photocatalyst. A size-selective photoetching technique was used to prepare the jingle bell nanostructure of SiO(2)/CdS. Nanoparticles of Au and Ag were deposited by irradiation of the photoetched SiO(2)/CdS in the presence of the corresponding metal complexes under deaerated conditions. Chemical etching of Au-deposited particles enabled the selective removal of CdS without any influence on the surface-plasmon absorption of Au. TEM analyses of the resulting particles suggested that some particles were encapsulated in hollow SiO(2) particles, while other Au particles were deposited on the outer surface of the SiO(2) shell. Emission spectra of the photoetched SiO(2)/CdS showed that the metal deposition developed a broad emission with a peak around 650 nm originating from surface defect sites, the degree being dependent on the kind of metal nanoparticles and their amount of deposition. This fact can be explained by the formation of metal-CdS binary nanoparticles having defect sites at the interface between metal and CdS.

Electron microscopy of La0.7Ca0.3MnO3
M Arita, K Hamada, A Okada, H Asano, M Matsui, T Shibayama
JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS, 44, 1A, 304, 308, JAPAN SOC APPLIED PHYSICS, 2005年01月, ［査読有り］
英語, 研究論文（学術雑誌）, The appearance of forbidden reflections in the electron diffraction patterns of L0.7Ca0.3MnO3 was studied, which violates the Prima symmetry reported so far in X-ray and. neutron diffractometry studies. The forbidden reflections originate through the multiple diffraction process of a crystal slightly inclined from its zone axis. Under this diffraction condition, the corresponding superlattice contrasts in high resolution transmission electron microscopy images were reproduced in image simulations made without the assumption of symmetry reduction in the crystal.

3P147 糖水溶液の形態観測による凍結抑制に関する研究(水・水和/電解質))
内田 努, 永山 昌史, 柴山 環樹, 郷原 一寿
生物物理, 45, supplement, S240, 一般社団法人 日本生物物理学会, 2005年
日本語

Damage behavior of electron/helium dual-beam irradiation on Fe-Cr-Mn(W, V) alloy
BF Hu, H Kinoshita, T Shibayama, H Takahashi
PRICM 5: THE FIFTH PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING, PTS 1-5, 475-479, 1463, 1466, TRANS TECH PUBLICATIONS LTD, 2005年, ［査読有り］
英語, 研究論文（学術雑誌）, The effect of helium on irradiation damage behavior in Fe-Cr-Mn(W,V) steel was investigated by electron/helium ion dual-beam irradiation. The results indicate that helium can promote the increase of dislocation density and enhance the void nucleation and void swelling of Fe-Cr-Mn(W, V) alloy. The segregation of solute elements near grain boundary was suppressed by existence of helium. Also the interface of carbide-matrix migration and the change of solute concentration near the interface were observed during dual-beam irradiation.

Microstructure of SCC in a Surface-worked 316L Stainless Steel in High Temperature Water　　　　　　　　　　　　　　　
H. Takahashi, R. Ishibashi, T. Kato, T. Horiuchi, T. Shibayama, N. Sakaguchi, S. Watanabe
Proceedings of International Workshop on Influence of Atomic Displacement Rate, Neutron Spectrum and Irradiation Temperature on Radiation Induced Ageing of Power Reactor Components: Experiment and Modeling, Dimitrovgrad, Russia, October 5, 2005 (The Resea, 1, 12, 2005年, ［査読有り］
英語, 研究論文（国際会議プロシーディングス）

Effect of electron-beam irradiation temperature on irradiation damage of high Mn-Cr steel
DS Bae, SH Nahm, HM Lee, H Kinoshita, T Shibayama, H Takahashi
JOURNAL OF NUCLEAR MATERIALS, 329, 1038, 1042, ELSEVIER SCIENCE BV, 2004年08月, ［査読有り］
英語, 研究論文（学術雑誌）, The effect of electron-beam irradiation temperature on irradiation damage of a high Mn-Cr austenitic steel for structure material of nuclear and/or fusion reactors from the point of view of the reduced radio-activation was investigated by using the 1250 kV HVEM and an energy dispersed X-ray analyzer (EDX) in a 200 kV FE-TEM with beam diameter of about 0.5 nm. Void formation was not observed even at the elevated irradiation temperature. Dislocation loop growth was observed and the density and size of dislocation loop increased with irradiation dose. Irradiation-induced segregation of Cr and Mn at grain boundaries were observed by electron-beam irradiation condition. The amount of Mn segregation increased with irradiation temperature, however, the case of Cr was suppressed. (C) 2004 Elsevier B.V. All rights reserved.

A study of the formation of nanometer-scale cavities in helium-implanted 4H-SiC
C. H. Zhang, S. E. Donnelly, V. M. Vishnyakov, J. H. Evans, T. Shibayama, Y. M. Sun
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, 218, 1-4, 53, 60, 2004年06月, ［査読有り］
英語, 研究論文（国際会議プロシーディングス）, In this work, the annealing behavior of microstructures in 4H-SiC helium-implanted at about 500 K to moderate doses (2.5-5)×1016 ionscm-2 is studied by combining transmission electron microscopy (TEM) and Rutherford backscattering spectrometry (RBS). It is found that a low concentration of planar clusters of helium bubbles in ring structures was formed in a narrow range of dose in a well-defined depth region of the specimens on annealing above 973 K. The formation of the bubble layer is associated with remarkable distortion and deformation in the matrix. A simple model based on the frozen matrix assumption was developed to study the production of defects in SiC below the temperature of vacancy mobility. We found that the main features of the depth distribution of the bubble layer can be understood using this model if assuming the planar clusters of bubbles evolve from vacancy clusters larger than a critical size through an intermediate stage of helium platelets. © 2004 Elsevier B.V. All rights reserved.

Effect of microstructure on oxidation resistance of MoSi2 fabricated by spark plasma sintering
J Kuchino, K Kurokawa, T Shibayama, H Takahashi
VACUUM, 73, 3-4, 623, 628, PERGAMON-ELSEVIER SCIENCE LTD, 2004年04月, ［査読有り］
英語, 研究論文（学術雑誌）, In order to clarify the effect of microstructure on oxidation resistance of MoSi2, structure and oxidation resistance of sintered MoSi2 were studied. Sintered MoSi2 was fabricated by a spark plasma sintering method from the two kinds of starting material, MoSi2 powder and mixed powders of elemental Mo and Si. Dense MoSi2 containing few SiO2 inclusions was fabricated by applying in situ synthesis using mixed powders of Mo and Si. Oxidation behavior in the accelerated oxidation temperature region of MoSi2 showed that accelerated oxidation was remarkably suppressed. (C) 2004 Elsevier Ltd. All rights reserved.

凍結抑制物質の氷表面上における形態観測
内田 努, 永山 昌史, 柴山 環樹, 郷原 一寿
日本雪氷学会全国大会講演予稿集, 2004, 82, 82, 公益社団法人 日本雪氷学会, 2004年

Effect of He-injection on irradiation damage in heat affected zone of welded SUS304 steel
DS Bae, H Kinoshita, T Shibayama, H Takahashi
MATERIALS TRANSACTIONS, 45, 1, 59, 64, JAPAN INST METALS, 2004年01月, ［査読有り］
英語, 研究論文（学術雑誌）, The heat affected zone (HAZ) of welded SUS304 steel has been irradiated using three irradiation modes of electron single irradiation, electron irradiation after He-injection and electron /He ion dual-beam irradiation by 1250kV high voltage electron microscope (HVEM) connected with an ion accelerator. Void size in the specimen with pre-injected helium increased considerably and the void size distribution was a bi-modal. Void swelling is the highest in the case of electron irradiation after He-injection. The segregation of solutes of Ni and Cr near grain boundary was suppressed in the cases of electron/He+ -ion dual-beam and electron irradiation after He-injection comparing with electron single irradiation.

Size and Structure-dependent Photocatalytic Activity of Jingle-Bell-Shaped Silica-coated Cadmium Sulfide Nanoparticles for Methanol Dehydrogenation
PAL B, TORIMOTO T, IWASAKI K, SHIBAYAMA T, TAKAHASHI H, OHTANI B
J. Phys. Chem. B, 108, 48, 18670, 18674, 2004年

Preparation and Characterization of Water-soluble Jingle Bell-shaped Silica-coated Cadmium Sulfide Nanoarticles
IWASAKI K, TORIMOTO T, SHIBAYAMA T, TAKAHASHI H, OHTANI B
J. Phys. Chem. B, 108, 32, 11946, 11952, 2004年

Plane and cross-sectional TEM observation to clarify the effect of damage region by ion implantation on induced phase transformation in austenitic 301 stainless steel
D. Gustiono, N. Sakaguchi, T. Shibayama, H. Kinoshita, H. Takahashi
Materials Transactions, 45, 1, 65, 68, 2004年, ［査読有り］
英語, 研究論文（学術雑誌）

Size, density, and shape of InAs quantum dots in closely stacked multilayers grown by the Stranski-Krastanow mode
Shiramine Ken-ichi, Muto Shunichi, Shibayama Tamaki, Takahashi Heishichiro, Kozaki Tamotsu, Sato Seichi, Nakata Yoshiaki, Yokoyama Naoki
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 21, 5, 2054, 2059, American Vacuum Society, 2003年09月
英語, Closely stacked multilayer structures of InAs islands with intermediate-layer thicknesses d of 3, 6, 10, and 20 nm were grown by the Stranski-Krastanow mode of molecular beam epitaxy and were observed using transmission electron microscopy (TEM) and atomic force microscopy (AFM). The multilayers consisted of five InAs layers each of a thickness of 1.8 monolayers and four GaAs layers each of a thickness d. Columns of coherent islands were observed by cross-sectional TEM. Changes in the size and density of the islands with d, determined by AFM, could be explained in terms of (i) change in the...

Creep deformation of grain boundary in a highly crystalline SiC fibre
T Shibayama, Y Yoshida, Y Yano, H Takahashi
JOURNAL OF ELECTRON MICROSCOPY, 52, 1, 75, 78, OXFORD UNIV PRESS, 2003年, ［査読有り］
英語, 研究論文（学術雑誌）, Silicon carbide (SiC) matrix composites reinforced by SiC fibres (SiC/SiC composites) are currently being considered as alternative materials in high Ni alloys for high-temperature applications, such as aerospace components, gas-turbine energy-conversion systems and nuclear fusion reactors, because of their high specific strength and fracture toughness at elevated temperatures compared with monolithic SiC ceramics. It is important to evaluate the creep properties of SiC fibres under tensile loading in order to determine their usefulness as structural components. However, it would be hard to evaluate creep properties by monoaxial tensile properties when we have little knowledge on the microstructure of crept specimens, especially at the grain boundary. Recently, a simple fibre bend stress relaxation (BSR) test was introduced by Morscher and DiCarlo to address this problem. Interpretation of the fracture mechanism at the grain boundary is also essential to allow improvement of the mechanical properties. in this paper, effects of stress applied by BSR test on microstructural evolution in advanced SiC fibres, such as Tyranno-SA including small amounts of Al, are described and discussed along with the results of microstructure analysis on an atomic scale by using advanced microscopy.

Nano-scale phase transformation in Ti-implanted austenitic 301 stainless steel
D Gustiono, N Sakaguchi, T Shibayama, H Kinoshita, H Takahashi
JOURNAL OF ELECTRON MICROSCOPY, 52, 5, 449, 453, OXFORD UNIV PRESS, 2003年, ［査読有り］
英語, 研究論文（学術雑誌）, Phase-transformation behaviours were investigated for austenitic 301 stainless steel during implantation at room temperature with 300 keV Ti ions to fluences of 8 X 10(19)similar to3 X 10(21) ions m(-2) by means of transmission electron microscopy. The cross-sectional specimen was prepared using a focused ion beam. Plan observation of the implanted specimen showed that phase transformation from gamma-phase to alpha-phase was induced by implantation to a fluence of 3 X 10(20) Ti ions m(-2). The nucleation of the irradiation (implantation)-induced phase increased with the increase of the dose. The orientation relationship between the gamma matrix and the induced alpha martensitic phase was identified as (011)alpha//(111)gamma and [11-1]alpha//[10-1], close to the Kurdjumov-Sachs relationship. Cross-sectional observation after implantation to a fluence of 5 X 10(20) ions m(-2) showed that phase transformation mostly nucleated near the surface and occurred in the higher the concentration gradient of the implanted ion, i.e. a higher stress concentration takes place and this stress introduced by the implanted ions acts as a driving force for the transformation.

Preparation of novel silica-cadmium sulfide composite nanoparticles having adjustable void space by size-selective photoetching
T Torimoto, JP Reyes, K Iwasaki, B Pal, T Shibayama, K Sugawara, H Takahashi, B Ohtani
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 125, 2, 316, 317, AMER CHEMICAL SOC, 2003年01月, ［査読有り］
英語, 研究論文（学術雑誌）

Radiation-induced segregation and precipitation behaviours around cascade clusters under electron irradiation
Y Sueishi, N Sakaguchi, T Shibayama, H Kinoshita, H Takahashi
JOURNAL OF ELECTRON MICROSCOPY, 52, 1, 63, 68, OXFORD UNIV PRESS, 2003年, ［査読有り］
英語, 研究論文（学術雑誌）, We have investigated the formation of cascade clusters and structural changes in them by means of electron irradiation following ion irradiation in an austenitic stainless steel. Almost all of the cascade clusters, which were introduced by the ion irradiation, grew to form interstitial-type dislocation loops or vacancy-type stacking fault tetrahedra after electron irradiation at 623 K, whereas a few of the dot-type clusters remained in the matrix. It was possible to recognize the concentration of Ni and Si by radiation-induced segregation around the dot-type clusters. After electron irradiation at 773 K, we found that some cascade clusters became precipitates (delta-Ni2Si) due to radiation-induced precipitation. This suggests that the cascade clusters could directly become precipitation sites during irradiation.

Behaviors of cascade damage structure under electron irradiation and annealing
H Takahashi, Y Sueishi, N Sakaguchi, T Shibayama, H Kinoshita, C Namba
MATERIALS FOR ADVANCED ENERGY SYSTEMS AND FISSION AND FUSION ENGINEERING, PROCEEDINGS, 252, 258, WORLD SCIENTIFIC PUBL CO PTE LTD, 2003年, ［査読有り］
英語, 研究論文（国際会議プロシーディングス）, When the crystalline materials are neutron irradiated under fission and fusion conditions, a large number of point defects and cascade damage are introduced. These defects behaviors affect the microsturctural evolution and mechanical and chemical properties. Especially the initial damage structures influence on the micro-structural development during further irradiation but it is impossible to observe the initial stage of the irradiation damage under neutron irradiation conditions. For these study transmission electron microscopy and ion-accelerator are useful because of the possibility of direct observation under irradiation by connecting high voltage electron microscope (HVEM) with ion accelerator to simulate the neutron irradiation. Namely it is possible to study due to in-situ experiment the behaviors of cascade damage and point defects. It has been already studied on the cascade damage behaviors under ion-irradiation, and it has been pointed out that cascade collapse affect the microsturctural evolution under the irradiation. According to several researches vacancy loops were formed and also were nucleated from cascade depleted zones. However the more detailed behaviors of cascade damage have been not clarified yet. Especially the role of cascade on the segregation or nucleation of precipitate induced by irradiation, and dislocation evolution during further irradiation.
In the present study, direct TEM observation and chemical compositional change have been carried out after introducing cascade by means of ion accelerator and electron-irradiation by HVEM.

Effects of applied stress on microstructural evolution in highly crystalline SiC fiber
T Shibayama, Y Yoshida, Y Yano, K Sugawara, H Takahashi, C Namba
MATERIALS FOR ADVANCED ENERGY SYSTEMS AND FISSION AND FUSION ENGINEERING, PROCEEDINGS, 302, 307, WORLD SCIENTIFIC PUBL CO PTE LTD, 2003年, ［査読有り］
英語, 研究論文（国際会議プロシーディングス）, Silicon carbide matrix composites reinforced by continuous SiC fibers are currently being considered for high temperature applications such as aerospace components, gas turbine energy conversion systems and nuclear reactors, because of high specific strength at elevated temperatures, fracture toughness compared with monolithic ceramics. It is important to evaluate creep properties under tensile loading to a SiC fiber to apply a structural component. However, we have little knowledge on microstructure of that, especially grain boundary. Recently, a simple fiber bend stress relaxation (BSR) test was introduced by J. A. DiCarlo.
Interpretation of the fracture mechanism at the grain boundary is also essential to improve mechanical properties. In this paper, effects of applied stress by BSR test on microstructural evolution in advanced SiC fibers are described and discussed with our results of microstructure analysis in an atomic scale by using advanced microscopy.

High-Temperature Oxidation of Ti Containing Stainless Steel in O2-N2 Atmosphere　　　　　　　　　　　　　　　
Hidenori Onishi, Isao Saeki, Ryusaburo Furuichi・Toru Okayama, Kenko Hanamatsu, Tamaki Shibayama, Heishichiro Takahashi, Shinichi Kikkawa
Corrosion Science and Technology, 5, 217, 224, 2003年, ［査読有り］
英語

Damaging process of alpha-SiC under electron irradiation studied with electron microscopy and spectroscopy
S Muto, T Tanabe, T Shibayama, H Takahashi
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 191, 519, 523, ELSEVIER SCIENCE BV, 2002年05月, ［査読有り］
英語, 研究論文（学術雑誌）, We have revisited damaging process of 6H-SiC by electron- and neutron-irradiation, applying electron energy-loss spectroscopy in a transmission electron microscope. Results obtained for low temperature irradiation are reported here. A considerable volume swelling occurred by amorphization. During the structural disordering, Si-Si direct bonding is more easily formed than C-C bonding in the matrix, which can be qualitatively understood by simple molecular orbital calculations. The present results and previous report for room temperature irradiation seem to support the amorphization mechanism that accumulation of interstitial atoms gives rise to structural disordering rather than local lattice distortions by anti-sites defects, as suggested by recent molecular dynamics simulations. (C) 2002 Elsevier Science B.V. All rights reserved.

Effects of helium on radiation behavior in low activation Fe-Cr-Mn alloys
H Benfu, H Kinoshita, T Shibayama, H Takahashi
MATERIALS TRANSACTIONS, 43, 4, 622, 626, JAPAN INST METALS, 2002年04月, ［査読有り］
英語, 研究論文（学術雑誌）, In order to investigate the effects of helium on the microstructural evolution in Fe-Cr-Mn (W, V) alloy during three irradiation modes of electron beam, electron/He+-ion dual-beam and electron irradiation after helium pre-injection, in situ observations were carried out using a high voltage electron microscope connected with an ion accelerator. The interstitial-type dislocation loops and small voids were formed in the early stage of irradiation. The average void size was smaller and void number density was higher under irradiation condition by electrons after helium pre-injection and by dual-beam in comparison with the case of electron irradiation. Irradiation-induced grain boundary segregation of Cr and Mn was suppressed due to existence of helium. From these results it is suggested that helium strongly influences dislocation structural development and void nucleation during irradiation. The effect of interactions between helium and point defects is discussed.

Microstructure evolution in highly crystalline SiC fiber under applied stress environments
T Shibayama, Y Yoshida, Y Yano, H Takahashi
ADVANCED SIC/SIC CERAMIC COMPOSITES: DEVELOPMENTS AND APPLICATIONS IN ENERGY SYSTEMS, 144, 301, 307, AMER CERAMIC SOC, 2002年, ［査読有り］
英語, 研究論文（国際会議プロシーディングス）, Because they exist high specific strength, fracture and toughness at elevated temperatures compared with monolithic ceramics, silicon carbide matrix composites reinforced by continuous SiC fibers are currently being considered for high temperature applications such as aerospace components, gas turbine energy conversion systems and nuclear reactors. It is important to evaluate the creep properties under tensile loading of a SiC fiber to determine their usefulness for structural components. However, we have little knowledge on microstructure of crept specimens, especially at the grain boundary.
Recently, a simple fiber bend stress relaxation (BSR) test was introduced by Morscher and DiCarlo. Interpretation of the fracture mechanism at the grain boundary is also essential to improve mechanical properties.
In this paper, effects of applied stress by BSR test on microstructural evolution in advanced SiC fibers are described and discussed with our results of microstructure analysis on an atomic scale by using advanced microscopy.

Atomistic dynamical observation of grain boundary structural changes under electron irradiation
N. Sakaguchi, T. Shibayama, H. Kinoshita, H. Takahashi
Journal of Nuclear Materials, 307-311, 1003, 1006, 2002年, ［査読有り］
英語, 研究論文（学術雑誌）

Development of V-Ti-Cr-Si Type Low-Activation Vanadium Alloys for Fusion　　　　　　　　　　　　　　　
M. Satou, K. Abe, A.Hasegawa, H. Kayano, T. Shibayama, H. Matsui
Fusion Energy 1998(CD-ROM), 2001年12月, ［査読有り］
英語, 研究論文（学術雑誌）

Sol-gel synthesis of monazite-type cerous phosphate for fiber coating
L. Bo, S. Liya, L. Xiaozhen, Z. Shuihe, Z. Yumei, W. Tianmin, Y. Sasaki, K. Ishii, Y. Kashiwaya, H. Takahashi, T. Shibayama
Journal of Materials Science Letters, 20, 11, 1071, 1075, 2001年06月01日, ［査読有り］
英語, 研究論文（学術雑誌）, Various advantages of sol-gel processing are studied for the fabrication of CePO4 sols by reaction of alkoxide precursors. The potential application of the CePO4 sols as a fiber coating precursor is also discussed. The amorphous CePO4 phase obtained by alkoxide method transformed directly to monazite structure during heating is also analyzed. The results show that the presence of water is necessary to stabilize the hexagonal structure of CePO4.

Improvement of mechanical properties of SiC/SiC composites by various surface treatments of fibers
T. Hinoki, W. Yang, T. Nozawa, T. Shibayama, Y. Katoh, A. Kohyama
Journal of Nuclear Materials, 289, 1-2, 23, 29, 2001年, ［査読有り］
英語, 研究論文（学術雑誌）, In order to make an interfacial shear strength control layer (ISSCL), such as pyrolytic C layer, effective and improve SiC/SiC composites' mechanical properties, heat treatment at 1500 °C under Ar flow in quite low O2 partial pressure or a CVI SiC coating were applied to Hi-NicalonTM SiC fibers. Interfacial microstructures between fiber and matrix were examined by SEM and TEM. Interfacial shear properties were evaluated by single-fiber push-out tests and compared with the results of three-point bend tests and tensile tests. Fracture surfaces after mechanical tests were examined by SEM with EDS and optical interferometric profilometry. Active oxidation of the fibers decreased fiber mechanical properties and made the composites brittle, although it was successful in making the ISSCL rough. SiC fiber coating induced strong bonding between fiber and ISSCL and turned the crack path from between the fiber and the ISSCL to the inside of the ISSCL. Interfacial frictional stress was increased and the mechanical properties of tensile tests were improved.

Formation of non-equilibrium phase in Cu by high-energy Ti-implantation at room temperature
T Shibayama, M Fujikawa, H Kinoshita, H Takahashi
PRICM 4: FORTH PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING, VOLS I AND II, 1493, 1496, JAPAN INST METALS, 2001年, ［査読有り］
英語, 研究論文（国際会議プロシーディングス）, The technique of ion implantation is being considered for the surface modification of materials and the formation of non-equilibrium phase at lower temperatures and it might be effective for corrosion resistance, high electro conductivity and thermal conductivity. In this study, Ti ions were implanted up to 2 x 10(18) ions/cm(2) at 300 keV at room temperature in polycrystalline Cu. After Ti implantation, the specimens were annealed in the vacuum chamber under a vacuum of 1x10(-5) Pa. The annealing temperature range is from 300degreesC to 500degreesC. The maximum annealing time is 8 hours. Cross-sectional TEM specimens were prepared by focused ion beam (FIB) micro sampling method. The phase and structure of implanted layer were examined by field emission electron microscope (FE-TEM) equipped with X-ray energy dispersion analyzer (EDS). The calculated depth profile of the implanted Ti in Cu by TRIM-98 is in good agreement with the experimental concentration profile by EDS. TEM observation indicated the formation of Ti supersaturated solid solution phase in Ti implanted layer. The preliminary results are introduced. The formation mechanism of non-equilibrium phase in Ti implanted layer following annealing and effects of annealing temperature and time on phase transformation in Ti implanted layer will be discussed.

Damaged structure in SUS316L stainless steel irradiated by triple beams of electron and dual ions
S Oyagi, H Kinoshita, T Shibayama, H Takahashi
PRICM 4: FORTH PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING, VOLS I AND II, 1469, 1472, JAPAN INST METALS, 2001年, ［査読有り］
英語, 研究論文（国際会議プロシーディングス）, The first wall materials of fusion reactors are exposed to long-term high flux irradiation of 14MeV neutrons while transmutants of helium and solid elements will be produced in the matrix. Void swelling and mechanical properties will be strongly influenced by these transmutants. It is not clear that the effect of these transmutants and irradiation damage on damage structure development such as phase stability, void swelling, precipitate formation and so on in 316L stainless steel. 316L stainless steel was investigated to clarify the effect of gas and solid metal transmutants defect clustering process under triple beams irradiation using by High Voltage Electron Microscope (JEM-ARM1300) and two ion accelerators to implant simultaneously helium and solid ions.

Effects of small additional elements on nano-structural evolution in crept SiC fibers
Y Yano, Y Yoshida, T Shibayama, H Takahashi
PRICM 4: FORTH PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING, VOLS I AND II, 753, 756, JAPAN INST METALS, 2001年, ［査読有り］
英語, 研究論文（国際会議プロシーディングス）, Silicon carbide matrix composites reinforced by continuous SiC fibers are currently being considered for high-temperature applications such as aerospace components, gas turbine energy conversion systems and nuclear reactors, because of their high specific strengths at elevated temperatures, fracture toughness compared with that of monolithic ceramics, superior oxidation resistance, and low level of induced radioactivity in nuclear environments. Since the SiC fibers would experience thermo mechanical stress at elevated temperatures, it is important to evaluate long-term phase stability and creep properties. Elucidation of the fracture mechanism at the grain boundary is also essential to improve mechanical properties. However, it is difficult to measure creep properties under the condition of tensile loading to a SiC fiber. Thus, a simple fiber bend stress relaxation (BSR) test has been developed by J. A. DiCarlo. In the present study, the BSR test was applied to Tyranno-SA SiC fibers to evaluate stress relaxation as functions of time, temperature and environment. TEM specimens of SiC fibers before and after the BSR test were prepared by the Focused Ion Beam method. HR-TEM analysis was carried out by means of JEOL 201OFE with GIF200.
In this paper, the effects of stress applied by the BSR test on nano-structural evolution in advanced SiC fibers are described and discussed together with our results of microstructure analysis on an atomic scale by using advanced microscopy.

Microstructural stability of SiC/SiC composites under dual-beam ion irradiation
Y Katoh, H Kishimoto, M Ando, A Kohyama, T Shibayama, H Takahashi
EFFECTS OF RADIATION ON MATERIALS: 20TH INTERNATIONAL SYMPOSIUM, 1045, 786, 798, AMER SOCIETY TESTING AND MATERIALS, 2001年, ［査読有り］
英語, 研究論文（国際会議プロシーディングス）, Microstructural evolution of silicon carbide fiber-reinforced silicon carbide matrix composites (SiC/SiC composites) during dual-beam ion irradiation was studied. The composites had been fabricated by means of chemical vapor infiltration (CVI) and polymer impregnation and pyrolysis (PEP) methods using advanced fibers, i.e., Hi-Nicalon (TM) Type-S and Tyranno (TM) -SA, as well as conventional fibers. Dual-beam ion irradiation was performed to 10 dpa at 873K and 60appmHe/dpa. Composites with advanced low-oxygen near-stoichiometric SiC fiber with high crystallinity and beta-SiC matrix exhibited superior irradiation resistance, in contrast to that amorphous Si-C-O based fibers and conventional polymer-derived matrix exhibited microstructural instability in association with irradiation-induced crystallization. Pyrolytic carbon deposited as the fiber-matrix (F-M) interphase exhibited irradiation-induced amorphization and the helium co-implantation enhanced it. Post-irradiation heat treatment caused significant microstructural changes across the F-M interphases at temperatures as low as the composites are supposed to retain their mechanical strength.

High-Temperature Oxidation of Ti Containing Stainless Steel in O2-N2 Atmosphere　　　　　　　　　　　　　　　
Hidenori Onishi, Isao Saeki, Ryusaburo Furuichi・Toru Okayama, Kenko Hanamatsu, Tamaki Shibayama, Heishichiro Takahashi, Shinichi Kikkawa
Proceedings of 12th Asian Pacific Corrosion Control Conference, 820, 829, 2001年, ［査読有り］
英語

Atomistic observation of radiation-induced grain boundary movement in Fe-Cr-Ni alloy under electron irradiation
N. Sakaguchi, T. Shibayama, H. Kinoshita, H. Takahashi
Philosophical Magazine Letters, 81, 10, 691, 696, 2001年, ［査読有り］
英語, 研究論文（学術雑誌）

Direct observation of a Ti/Cu interface with atomic displacement under electron irradiation
S. Ohta, N. Sakaguchi, T. Shibayama, H. Talahashi
Journal of Electron Microscopy, 203, 1, 34, 39, 2001年, ［査読有り］
英語, 研究論文（学術雑誌）

Joining of silicon carbide composites for fusion energy applications
CA Lewinsohn, M Singh, T Shibayama, T Hinoki, M Ando, Y Katoh, A Kohyama
JOURNAL OF NUCLEAR MATERIALS, 283, 1258, 1261, ELSEVIER SCIENCE BV, 2000年12月, ［査読有り］
英語, 研究論文（学術雑誌）, Joining of silicon carbide based materials has been recognized as one of the enabling technologies for the successful utilization of ceramic components in fusion energy systems. Sintered silicon carbide (Hexoloy SA) and silicon carbide (Hi-Nicalon(TM)) fiber reinforced silicon carbide matrix composites have been joined using reaction forming/bonding based joining technologies. The room- and high-temperature mechanical properties and fractography of ceramic joints have been reported. (C) 2000 Elsevier Science B.V. All rights reserved.

The current status of SiC/SiC composites and their future prospects
T Shibayama, H Takahashi
JOURNAL OF THE JAPAN INSTITUTE OF METALS, 64, 11, 985, 991, JAPAN INST METALS, 2000年11月, ［査読有り］
日本語, 研究論文（学術雑誌）, SiC fiber-reinforced SiC matrix composites (SiC/SiC composites) are attractive structural materials for next-generation high-temperature applications, because the density of such a composite is only one third of the conventional heat-resistance one, and it has superior oxidation resistance due to the formation of SiO2 on the surface in the air at elevated temperatures. A research and development activity to realize high efficiency gas turbine materials and aerospace materials replaced CIC composites has been initiated. Continuous fiber-reinforced ceramic composites (CFCC), including SiC/SiC composites, should be showed to prevent crack propagation due to deflection and scattering of micro cracks initiated in the matrix around the interphase. As the crack-opening displacement (COD) is increased, the reinforced fibers should bridge the matrix and they will break after pull out. The apparent fracture resistance can be increased. As a result of this sequence of phenomena, the CFCC shows the better mechanical properties than that of the monolithic ceramics. Therefore, interpretation of the fracture mechanism at the interface between the fibers and the matrix is essential to improve mechanical properties. Currently, many efforts are being made to develop the advanced SiC/SiC composites from "state-of-the-art" materials by a number of research organizations, including universities, national institutes and industries in the world. In this paper, the current status of research and development of SiC/SiC composites is described together with our results of microstructure analysis using advanced microscopy, and future prospects are also discussed.

Microstructural evolution of Hi-Nicalon (TM) SiC fibers annealed and crept in various oxygen partial pressure atmospheres
GW He, T Shibayama, H Takahashi
JOURNAL OF MATERIALS SCIENCE, 35, 5, 1153, 1164, KLUWER ACADEMIC PUBL, 2000年03月, ［査読有り］
英語, 研究論文（学術雑誌）, It is expected that in the future SiC fiber-reinforced ceramic-matrix composites (CMCs) will be used in high temperature and hostile environments. In this study, Hi-Nicalon(TM) SiC fibers were annealed and crept at 1500 degrees C for 1 hour in air, an argon flow and an ultra high-purity argon flow in order to investigate the effects of atmospheres and load conditions on the decomposition behavior and microstructural evolution of the fibers. After the fibers were annealed and crept in air, a silica layer with cracks was formed on the fiber surface. Under the creep load, the silica layer became thicker and porous due to the oxidation mechanism change from diffusion of ionic oxygen to transportation of oxygen molecules. An oxygen-enriched amorphous layer was formed at the fiber surface in the case of annealing in an argon flow, whereas SiC crystals were produced by the gas-phase reaction on the fiber surface when the fiber was crept in an argon flow. In an ultra high-purity argon flow, SiC crystals grew on the surface of both annealed and crept fibers. Growth of beta-SiC grain was enhanced under low oxygen partial pressure atmospheres and creep load. (C) 2000 Kluwer Academic Publishers.

Microstructural stability of SiC/SiC composites under dual-beam ion irradiation　　　　　　　　　　　　　　　
Yutai Katoh, Hirotatsu Kishimoto, Masami Ando, Akira Kohyama, Tamaki Shibayama, Heishichiro Takahashi
Institution of Chemical Engineers Symposium Series, 148, 786, 798, 2000年
英語, 研究論文（国際会議プロシーディングス）, Microstructural evolution of silicon carbide fiber-reinforced silicon carbide matrix composites (SiC/SiC composites) during dual-beam ion irradiation was studied. The composites had been fabricated by means of chemical vapor infiltration (CVI) and polymer impregnation and pyrolysis (PIP) methods using advanced fibers, i.e., Hi-Nicalon™ Type-S and Tyranno™-SA, as well as conventional fibers. Dual-beam ion irradiation was performed to 10 dpa at 873 K and 60 appmHe/dpa. Composites with advanced low-oxygen near-stoichiometric SiC fiber with high crystallinity and beta-SiC matrix exhibited superior irradiation resistance, in contrast to that amorphous Si-C-O based fibers and conventional polymer-derived matrix exhibited microstructural instability in association with irradiation-induced crystallization. Pyrolytic carbon deposited as the fiber-matrix (F-M) interphase exhibited irradiation-induced amorphization and the helium co-implantation enhanced it. Post-irradiation heat treatment caused significant microstructural changes across the F-M interphases at temperatures as low as the composites are supposed to retain their mechanical strength.

Structure and morphology transition of CePO4 coatings on alumina fibers
Li Bo, Shen Liya, Liu Xiaozhen, Wang Tianmin, K. Ishii, Y. Sasaki, Y. Kashiwaya, H. Takahashi, T. Shibayama
Journal of Materials Science Letters, 19, 4, 343, 347, Kluwer Academic Publishers, 2000年, ［査読有り］
英語, 研究論文（学術雑誌）, Cerium phosphate sols were synthesized and CePO4 coatings on alumina fibers were fabricated by an electrostatic attraction method. The morphology and structure change of CePO4 coatings during calcining were characterized by various techniques and their effects on the coating process were determined. The structure transition of CePO4 from hexagonal to monoclinic, accompanied with a morphology change, decreases the coverage of the coatings. This can be overcome by repetitive coating and a calcining process.

Fabrication of V-Cr-Ti-Y-Al-Si alloys by levitation melting
Toshinori Chuto, Takuya Nagasaka, Takeo Muroga, Manabu Satou, Katsunori Abe, Tamaki Shibayama, Shigeki Tomiyama, Masafumi Sakata
Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals, 64, 9, 743, 746, Japan Inst of Metals, 2000年, ［査読有り］
日本語, 研究論文（学術雑誌）, Three alloys of V-4Cr-4Ti type containing Si, Al and Y were fabricated by 2.5 kg scale levitation melting in this study. Workability and recrystallization behavior of the alloys were studied in order to establish the fabrication method of high-purity large ingot of V-Cr-Ti-Si-Al-Y type alloys, especially reducing interstitial impurity levels. Oxygen contents decreased with increasing yttrium contents and were kept below 180 mass ppm over wide region in the ingots. Nitrogen contents in the V-Cr-Ti-Y-Si-Al type alloys were only 100 mass ppm, which were as low as that in the starting materials. Only the V-4Cr-4Ti-0.1Y, Si, Al alloy could be cold-rolled at as-melted condition. Because large yttrium inclusions were observed in the alloys containing 0.5 mass%Y, it is necessary to optimize yttrium contents to avoid large inclusions and to obtain good workability.

Mechanical properties and damage behavior of non-magnetic high manganese austenitic steels
H Takahashi, Y Shindo, H Kinoshita, T Shibayama, S Ishiyama, K Fukaya, M Eto, M Kusuhashi, T Hatakeyama, Sato, I
JOURNAL OF NUCLEAR MATERIALS, 258, 1644, 1650, ELSEVIER SCIENCE BV, 1998年10月, ［査読有り］
英語, 研究論文（学術雑誌）, Fe-Cr-Mn steels have been considered as materials of structural components for fusion reactor because of their low induced-radio-activity compared with SUS316 stainless steels. It has been expected to develop a non-magnetic steel with a high stability of the austenitic phase and a strong resistance to irradiation environments. For these objectives, a series of the Fe-Cr-Mn steels have been examined by tensile tests and simulation irradiation by electrons. The main alloying compositions of the steels developed are; C:0.02-0.2 wt%, Mn:15 wt%, Cr:15-16 wt%, N:0.2 wt%. These steels were heat-treated at 1323 K for 1 h. The structure of the steels after the heat-treatment was austenite single phase. The yield stress of the steels was 350-450 MPa and the elongation were 55-60%. When the steels of high C and N was electron-irradiated at below 673 K, no voids were nucleated and only small dislocation loops were formed with high density. The austenite phase was also stable during irradiation below 673 K. Thus, newly developed high manganese steels have excellent mechanical proprieties and high irradiation resistance at relatively low temperature. (C) 1998 Elsevier Science B.V. All rights reserved.

Effect of purity on helium bubble formation in 9Cr martensitic steel during post-implantation annealing at 1105 K
T Nagasaka, T Shibayama, H Kayano, A Hasegawa, M Satou, K Abe
JOURNAL OF NUCLEAR MATERIALS, 258, 1193, 1198, ELSEVIER SCIENCE BV, 1998年10月, ［査読有り］
英語, 研究論文（学術雑誌）, Purification is essential to development of low-activation ferritic-martensitic steels for fusion reactor materials, not only from the practical Viewpoint of reducing highly radioactive elements but also from the fundamental viewpoint of irradiation effects in ferritic steels and Fe-Cr alloys. A high-purity 9Cr-0.1C martensitic steel was prepared from an ultra-high-purity iron and high-purity alloying elements. In order to study the effect of large amount of helium on microstructure in the high-purity martensitic steel, 1000 appm of helium ions were implanted into the steel, and then TEM observation was performed after post-implantation annealing. It was observed that small cavities were distributed more densely in the high-purity steel than In commercial-grade ones. Moreover, the denuded zone near grain boundaries in the high-purity steel was much thinner than that in commercial-grade ones. The difference in cavity formation between the high-purity and commercial-grade steels is discussed. (C) 1998 Published by Elsevier Science B.V. All rights reserved.

Effect of small additional elements on DBTT of V-4Cr-4Ti irradiated at low temperatures
Tamaki Shibayama, Ichiro Yamagata, Hideo Kayano, Chusei Namba
Journal of Nuclear Materials, 258-263, 1361, 1368, Elsevier, 1998年, ［査読有り］
英語, 研究論文（学術雑誌）, As a part of a program to screen several V-4Cr-4Ti containing Si, Al and Y alloys and optimize the amounts of Si, Al and Y, the Charpy impact test of five kinds of V-4Cr-4Ti-Si-Al-Y alloys by an instrumented Charpy impact testing machine using miniaturized specimens (1.5 mm × 1.5 mm × 20 mm) have been conducted before and after neutron irradiation. Charpy impact specimens were encapsulated in an aluminum vial filled with high purity He and irradiated up to 1.06 × 1019 n/cm2 (E >
1 MeV, 156 h) at low temperatures (about 150°C) in Japan Materials Testing Reactor (JMTR). The ductile brittle transition temperature (DBTT) of each alloy was determined by various methods on absorbed energy, brittle fracture ratio and lateral expansion from a quantitative analysis of fractography for broken specimens after the Charpy impact test. Almost all specimens were embrittled after low temperature irradiation. Decomposition of primary precipitates could result in migration of interstitial elements to irradiation defects and many precipitates are formed under irradiation. Radiation hardening then caused the substantial degradation of its fracture toughness. © 1998 Elsevier Science B.V. All rights reserved.

Effect of Purity on Microstructural Evolution in 9Cr Martensitic Steels Implanted with Helium
T. Nagasaka, T.Shibayama, H. Kayano, A.Hasegawa, M.Satou, K.Abe
Journal of Nuclear Materials, 258-263, 1193, 1198, 1998年, ［査読有り］
英語, 研究論文（学術雑誌）

Effects of Several Impurity Additions on Microstructural Evolution in High-Purity Fe-9Cr Ferritic Alloys after Helium Implantation
T. NAGASAKA, T. SHIBAYAMA, H. KAYANO, A. HASEGAWA, K. ABE
phys.stat.sol.(a), 167, 335, 346, 1998年, ［査読有り］
英語, 研究論文（学術雑誌）

Microstructures of High-Purity Ferritic Steels after Helium Implantation　　　　　　　　　　　　　　　
T.Nagasaka, T.Shibayama, H.Kayano, A.Hasegawa, K.Abe
Sci. Rep. RITU, 45, 1, 121, 126, 1997年03月, ［査読有り］
英語, 研究論文（学術雑誌）

Development of oxide dispersion strengthened vanadium alloy and its properties
T. Shibayama, I. Yamagata, H. Kurishita, H. Kayano
Journal of Nuclear Materials, 239, 1-3, 162, 169, 1996年12月, ［査読有り］
英語, 研究論文（学術雑誌）, Two kinds of oxide dispersion strengthened (ODS) vanadium alloys have been successfully fabricated by powder metallurgy. The detailed characteristics of the dispersion particles in a V-0.25Y2O3 and a V-4Cr-4Ti-0.5Si-0.5Al-0.5Y-0.25Y2O3 were examined by transmission electron microscopy (TEM) and Vickers micro hardness test. The density and size distribution of the dispersion particles were measured as fabricated and annealed at 2073 K by using TEM. In both alloys as fabricated, the mean Y2O3 size is 0.04 μm and precipitates which mainly consists of the solute atoms were observed in the V-4Cr-4Ti-0.5Si-0.5Al-0.5Y-Q.25Y2O3. The density of dispersion particles in V-0.25Y2O3 and V-4Cr-4Ti-0.5Si-0.5A1-0.5Y-0.25Y2O3 is 6.6 × 1018/m3 and 2.3 × 1018/m3 respectively. The annealing at 2073 K caused recrystallization in both alloys and a decrease the density of particles in only the V-4Cr-4Ti-0.5Si-0.5Al-0.5Y-0.25Y2O3 alloy due to disappearance of the precipitates.

Radiation damage process of vanadium and its alloys during electron irradiation
T Nishizawa, H Sasaki, S Ohnuki, H Takahashi, T Shibayama, H Kayano
JOURNAL OF NUCLEAR MATERIALS, 239, 1-3, 132, 138, ELSEVIER SCIENCE BV, 1996年12月, ［査読有り］
英語, 研究論文（学術雑誌）, Microstructural change and the migration energies of point defects in V, V-4Ti-4Cr and oxide dispersion strengthened vanadium were examined by high voltage electron microscopy. II-radiation was performed up to 7.2 dpa at room temperature to 773 K. To protect the specimens from surface contamination, some specimens were coated with Ti and Cr by the evaporation process. During irradiation of low dose, interstitial-type dislocation loops were initially nucleated and grown. Micro-voids were observed in oxide dispersion strengthened vanadium at 773 K. The migration energies of interstitials and vacancies were estimated from the number density and the growth rate of the loops, as a function of temperature. The microstructure change is explained by the effect of the interaction between impurities and solute atoms.

Development of Mo alloys with improved resistance to embrittlement by recrystallization and irradiation
Hiroaki Kurishita, Yuji Kitsunai, Tamaki Shibayama, Hideo Kayano, Yutaka Hiraoka
Journal of Nuclear Materials, 233-237, 1, 557, 564, 1996年10月01日, ［査読有り］
英語, 研究論文（学術雑誌）, In order to overcome the recrystallization embrittlement and irradiation embrittlement in Mo and W, which are major problems for their fusion applications, the basic idea of alloy design and microstructure control was presented. By applying the idea to Mo, ultra-fine grained Mo alloys with very fine TiC particles mostly existing at grain boundaries were developed for TiC additions of 0.1 to 1.0 wt%. Impact three-point bending tests showed that before and after recrystallization and fast-neutron irradiations to 0.08 dpa the developed alloys exhibit much lower ductile-brittle transition temperature (DBTT) and higher strength than TZM. The developed alloys also showed much higher resistance to recrystallization and grain growth. Both resistance increased with increasing TiC content
in the irradiated state the 1.0 wt% TiC-added alloy showed a DBTT lower by more than 200 K than TZM. The cause of the observed improvement was discussed.

Precipitation behavior of irradiated reduced-activation ferritic steels
Tamaki Shibayama, Akihiko Kimura, Hideo Kayano
Journal of Nuclear Science and Technology, 33, 9, 721, 727, 1996年, ［査読有り］
英語, 研究論文（学術雑誌）, In order to study the effects of small additional elements on precipitation behavior in reduced-activation ferritic steels under neutron irradiation, analytical transmission electron microscopy was used to examine the microstructure and the precipitation of the extraction replica of several reduced activation ferritic/martensitic steels which have different contents of small additional elements after 60 displacements per atom (dpa) irradiation at 693, 698 and 733K in the Fast Flux Test Facility (FFTF)/Materials Open Test Assembly (MOTA). All of reduced-activation ferritic/martensitic steels were found to have a good phase stability after irradiation. Micro-voids were observed in both materials of Fe-9Cr-2W with or without boron, the density of micro-voids in the steel with boron is larger than that without boron, and the mean size of micro-voids is smaller than that without boron. However void swelling was less than 1%. Most of the precipitates in the irradiated specimens were found to be M23C6 which consists of mainly Cr. The remainder of the precipitates were found to be Ta-rich M6C. Laves phase was observed only at 733K. Several precipitates which were Ti-rich including Si and W were also observed at grain boundary in Ti addition steels at 733K irradiation. Several Y2O3 particles were observed in an yttrium containing alloy. No precipitation including Al was observed in an Al containing alloy. Ti addition decreased precipitation of Ta-rich M6C in 9Cr and 12Cr steels in this irradiation condition. © 1996 Taylor and Francis Group, LTD.

Development of molybdenum alloy with high toughness at low temperatures
Hiroaki Kurishita, Yuji Kitsunai, Yutaka Hiraoka, Tamaki Shibayama, Hideo Kayano
Materials Transactions, JIM, 37, 1, 89, 97, Japan Institute of Metals (JIM), 1996年, ［査読有り］
英語, 研究論文（学術雑誌）, The irradiation embrittlement and recrystallization embrittlement of molybdenum and its alloys are major problems for their application to plasma facing components in the future fusion reactors. In order to overcome the problems, the basic idea of alloy design and microstructure control was proposed, and a TiC dispersed molybdenum alloy was developed by applying mechanical alloying and hot isostatic pressing treatments. The alloy, designated as MTC-02, contained an additive of 0.2 mass% titanium carbide. TEM observations revealed that the characteristic of microstructures of the alloy was extremely small grain size, a high density of dislocations and a fairly large number of very fine particles of Ti-oxy-carbide which exist along grain boundaries and in grain interiors. The low-temperature toughness of MTC-02 in four different states, i.e., the as-rolled, stress-relieved, recrystallized and neutron irradiated states, was examined by impact three-point bending tests using miniaturized flat specimens (1 mm × 1 mm × 20 mm). For comparison, the same examination was conducted for TZM alloy which is known to have the highest low-temperature toughness among the commercially available molybdenum alloys. It is shown that in each of the four states MTC-02 exhibits a much lower ductile-brittle transition temperature and a considerably higher strength than TZM, and the fracture of MTC-02 is completely transgranular, indicating that the grain boundaries are strengthened. It is argued that MTC-02 is unsusceptible to the detrimental effect of oxygen impurity.

アセトンとのミリングにより表面改質したチタンの水素吸蔵速度の向上と収差補正STEMによる顕微解析
中川祐貴, 新里恵多, 宮岡裕樹, 礒部繁人, 柴山環樹, 荻田典男, 市川貴之, 日本顕微鏡学会北海道支部学術講演会講演要旨集, 2021 (CD-ROM), 2021年

錯体水素化物・窒化ホウ素複合物質のリチウムイオン伝導度の評価
中川祐貴, 木村智遥, 礒部繁人, 柴山環樹, 日本原子力学会北海道支部研究発表会講演要旨集, 37th (CD-ROM), 2020年

チタンの水素吸蔵反応に及ぼす有機溶媒やグラファイトの表面改質効果
新里恵多, 中川祐貴, 濱本創, 林雄也, 宮岡裕樹, 礒部繁人, 柴山環樹, 荻田典男, 市川貴之, 日本金属学会講演大会(Web), 167th, 2020年

LiAlH₄/h-BN複合物質の水素放出機構の検討
中川祐貴, 礒部繁人, 柴山環樹, 日本金属学会講演概要(CD-ROM), 164th, 2019年

有機物とのミリングにより表面改質したチタンの水素化速度の向上と大気非曝露条件下でのTEM観察
中川祐貴, 新里恵多, 濱本創, 礒部繁人, 柴山環樹, 宮岡裕樹, 市川貴之, 日本顕微鏡学会北海道支部学術講演会講演要旨集, 2019, 2019年

電子線照射下における材料挙動 複合量子ビーム超高圧電子顕微鏡によるイオンと電子の重畳効果その場観察
柴山環樹, 渡辺精一, 顕微鏡, 54, 3, 2019年

複合量子ビーム超高圧電子顕微鏡を用いた複合照射(イオンビーム,電子線,レーザー)による無機ナノ構造の形成とその場観察
柴山環樹, 渡辺精一, 放射線化学(Web), 107, 2019年

イオン照射によるSi表面層の欠陥形成とEBSDによる残留歪み解析
武田陽佑, 近藤創介, 近藤創介, 檜木達也, 中川祐貴, 柴山環樹, 日本金属学会講演概要(CD-ROM), 163rd, ROMBUNNO.P170, 2018年09月05日
日本語

イオン照射によるSi表面層の欠陥形成とEBSDによる残留歪み解析
武田陽佑, 近藤創介, 近藤創介, 檜木達也, 中川祐貴, 柴山環樹, 日本金属学会講演概要(CD-ROM), 163rd, 2018年

EBSDを用いたイオン照射材料の硬さ試験機による微小圧痕周りの残留ひずみ分布解析
関口亮, 柴山環樹, 近藤創介, 檜木達也, 日本金属学会講演概要(CD-ROM), 159th, ROMBUNNO.P82, 2016年09月07日
日本語

水封入セルを用いた液中光照射誘起反応のTEM内その場観察
大藤功将, 五十嵐直也, 石岡準也, JEEM Melbert, 柴山環樹, 渡辺精一, 応用物理学会秋季学術講演会講演予稿集(CD-ROM), 77th, 2016年

EBSDを用いたイオン照射材料の硬さ試験機による微小圧痕周りの残留ひずみ分布解析
関口亮, 柴山環樹, 近藤創介, 檜木達也, 日本金属学会講演概要(CD-ROM), 159th, 2016年

ナノワイヤのCVD成長における酸化物基板上の核形成の影響
島田敏宏, 川人愛子, 田村貴大, XIE W, 石岡準也, 柴山環樹, 渡辺精一, 柳瀬隆, 長浜太郎, セラミックス基礎科学討論会講演要旨集, 53rd, 204, 2015年01月08日
日本語

イオン液体中のZnOナノ結晶の電子線・レーザー同時照射による光腐食のTEM内その場観察
小暮一馬, 大藤功将, 石岡準也, JEEM Melbert, MIRZA Rafiq, 河口楓, 谷津茂男, 柴山環樹, 渡辺精一, 応用物理学会秋季学術講演会講演予稿集(CD-ROM), 76th, 2015年

水溶媒中光誘起ナノ結晶合成における不純物効果
河口楓, JEEM Melbert, 谷津茂男, 柴山環樹, 渡辺精一, 日本金属学会講演概要(CD-ROM), 157th, 2015年

熱CVD法による酸化物基板上へのFeナノワイヤの作製
川人愛子, 柳瀬隆, 石岡準也, 柴山環樹, 渡辺精一, 長浜太郎, 島田敏宏, 応用物理学会秋季学術講演会講演予稿集(CD-ROM), 75th, ROMBUNNO.19P-PA4-3, 2014年09月01日
日本語

熱CVD法による酸化物基板上へのFeナノワイヤの作製
川人愛子, 柳瀬隆, 遠堂敬, 石岡準也, 柴山環樹, 渡辺精一, 長浜太郎, 島田敏宏, 日本セラミックス協会秋季シンポジウム講演予稿集(CD-ROM), 27th, ROMBUNNO.2P036, 2014年08月25日
日本語

液中プラズマ処理表面を用いた金属酸化物ナノ結晶合成
JEEM Melbert, BIN JULAIHI Muhammad Rafiq M., YATSU Shigeo, ISHIOKA Junya, SHIBAYAMA Tamaki, WATANABE Seiichi, 応用物理学会秋季学術講演会講演予稿集(CD-ROM), 75th, 2014年

Compositional and Structural Control of AuPt Nanoparticles Synthesized in Ionic Liquids by a Sputter Deposition Technique
S. Suzuki, T. Suzuki, Y. Tomita, M. Hirano, K. Okazaki, T. Shibayama, S. Kuwabata, T. Torimoto, CrystEngComm., 14, 4922-4926, 2012年06月01日
英語, 速報，短報，研究ノート等（学術雑誌）

ナノ時空間ダイナミクスのその場観察法による物質変換過程の解明
柴山環樹, 渡辺精一, 谷津茂男, 富岡智, 西山修輔, 伊藤芳浩, 日本金属学会講演概要(CD-ROM), 150th, ROMBUNNO.249, 2012年03月15日
日本語

核融合炉ブランケット研究におけるベリリウム化合物の取り扱い
柴山環樹, 中道勝, 宮本光貴, 久我典義, プラズマ･核融合学会誌, 77, 4, 888, 892, 2011年

低エネルギー水素イオン照射後の低放射化フェライト鋼の重水素保持脱離挙動
山内有二, 伊藤達哉, 日野友明, 信太祐二, 柴山環樹, 江里幸一郎, 鈴木哲, 秋場真人, 核融合エネルギー連合講演会予稿集, 8th (CD-ROM), ROMBUNNO.10A63P, 2010年
日本語, 研究発表ペーパー・要旨（全国大会，その他学術会議）

プロジェクトレビュー 日米科学技術協力事業JUPITER-IIプロジェクト
長谷川晃, 檜木達也, 清水昭比古, 柴山環樹, 横峯健彦, 野上修平, プラズマ・核融合学会誌, 85, 5, 267, 275, 2009年05月25日
プラズマ・核融合学会, 日本語, 記事・総説・解説・論説等（その他）

低エネルギー水素イオンを照射したF82H鋼の重水素保持脱離挙動
伊藤達哉, 信太祐二, 山内有二, 日野友明, 柴山環樹, 江里幸一朗, 鈴木哲, 秋場真人, 日本原子力学会北海道支部研究発表会講演要旨集, 27th, 26, 27, 2009年
日本語

複合ナノ構造のTEM内その場ナノメカニクス評価法の研究開発
柴山 環樹, 浜田 弘一, 渡辺 精一, 松尾 元一郎, 岸本 弘立, 香山 晃, まてりあ, 48, 12, 617, 617, 2009年
The Japan Institute of Metals and Materials, 日本語

Research and development on in-situ TEM method for nanomechanics analysis to nanostructured composites　　　　　　　　　　　　　　　
Materia, 48, 12, 617, 617, 2009年

ナノメカニクス接合解析技術とガス冷却高速炉用 SiC/W 接合部材の開発
柴山環樹, 岸本弘立, 香山 晃, 矢野康英, まてりあ, 47, 12, 628, 628, 2008年12月, ［査読有り］, ［招待有り］
公益社団法人 日本金属学会, 日本語, 速報，短報，研究ノート等（学術雑誌）

核融合炉環境に耐える機能材料の開発 ３．ブランケット機能材料　　　　　　　　　　　　　　　
小西哲之, 星野毅, 柴山環樹, 中道勝, 檜木達也, 鈴木晶大, 84, 10, 646, 658, 2008年10月, ［査読有り］, ［招待有り］
日本語, 記事・総説・解説・論説等（学術雑誌）

ナノメカニクス接合解析技術とガス冷却高速炉用SiC/W接合部材の開発
柴山 環樹, 岸本 弘立, 香山 晃, 矢野 康英, まてりあ, 47, 12, 628, 628, 2008年
公益社団法人 日本金属学会, 日本語

核融合炉環境に耐える機能材料の開発 ３．ブランケット機能材料　　　　　　　　　　　　　　　
プラズマ・核融合学会誌, 84, 10, 646, 658, 2008年

Development on Nanomechanics Based Joining Analysis Method and SiC and W Joining for Gas Cooled Fast Reactor　　　　　　　　　　　　　　　
Materia, 47, 12, 628, 628, 2008年

Development of Functional Materials for Fusion Reactor Application 3. Functional Materials for Blankets　　　　　　　　　　　　　　　
Journal of Plasma Fusion Research, 84, 10, 646, 658, 2008年

Microstructural characterization and in-situ experiment of advanced SiC/SiC composites and joining for Fusion applications　　　　　　　　　　　　　　　
SHIBAYAMA Tamaki, Introduction to the advanced nuclear technology in fusion, fuels and materials, 2, 187, 194, 2007年07月, ［査読有り］, ［招待有り］
英語, 記事・総説・解説・論説等（国際会議プロシーディングズ）

核融合ブランケットの先進中性子増倍材料としてのベリリウム金属間化合物の開発
土谷邦彦, 河村弘, 三島良直, 吉田直亮, 田中知, 内田宗範, 石田清仁, 柴山環樹, 宗像健三, 佐藤芳幸, 岩切宏友, 大沼郁雄, プラズマ・核融合学会誌, 83, 3, 207, 214, 2007年03月, ［査読有り］, ［招待有り］
原型炉用増殖ブランケットに必要な「高温・高照射環境に耐えうる先進中性子増倍材料」の開発について,ベリリウム金属間化合物であるBe_<12>Ti等に着目し,各種特性(機械的特性,化学的特性,照射特性等)および微小球製造技術開発を全日本規模の産学官連携のもとで実施している.この先進中性子増倍材料の開発における最近の成果について紹介する., プラズマ・核融合学会, 日本語, 記事・総説・解説・論説等（学術雑誌）

Effect of Minor Alloying Element on Dispersing Nano-particles in ODS Steel　　　　　　　　　　　　　　　
Y. Uchida, S. Ohnuki, N. Hashimoto, T. Suda, T. Nagai, T. Shibayama, K. Hamada, N. Akasaka, S. Yamashita, S. Ohstuka, T. Yoshitake, Mater. Res. Soc. Symp. Proc., 981E, JJ07, JJ09, 2007年, ［査読有り］

Japanese Activity on SiC/SiC and Related Technology R & D for Fusion　　　　　　　　　　　　　　　
A. Kohyama, T. Hinoki, J.S. Park, H. Kishimoto, A. Hasegawa, T. Shibayama, H. Tanigawa, H. Serizawa, 7th IEA International Workshop on SiC/SiC composites for Fusion and Advanced Fission Applications Plenary Meeting，Petten, the Netherlands，2006.9.18–20, 2006年, ［査読有り］
英語

30pB02P SiCの照射損傷組織発達過程の数値解析(真空・第一壁・材料)
渡辺 淑之, 近藤 創介, 森下 和功, 香山 晃, 柴山 環樹, Howard Heinisch, Fei Gao, プラズマ・核融合学会年会予稿集, 23, 2006年
プラズマ・核融合学会, 日本語

Irradiation effects of fracture behaviors on SiC/SiC composites　　　　　　　　　　　　　　　
Shibayama, T, Ogitsu, K, Watanabe, S, Proc. 2nd Japan-Korea Workshop on Fusion Materials Engineering Toward Next Generation of Fusion Devices, Ed. by T. Hino and H.K. Yoon, 210, 222, 2006年, ［査読有り］
英語, 記事・総説・解説・論説等（国際会議プロシーディングズ）

In-situ microstructural study for irradiated materials using Multi-Beam HVEM　　　　　　　　　　　　　　　
Watanabe, S, Sakaguchi, N, Shibayama, T, Proc. 2nd Japan-Korea Workshop on Fusion Materials Engineering Toward Next Generation of Fusion Devices, Ed. by T. Hino and H.K. Yoon, 74, 88, 2006年, ［査読有り］
英語, 記事・総説・解説・論説等（国際会議プロシーディングズ）

SiCの照射損傷組織発達過程の数値解析
渡辺淑之, 近藤創介, 森下和功, 柴山環樹, 香山晃, 日本金属学会講演概要, 137th, 2005年

Radiation-enhanced diffusion and grain boundary solute segregation in stainless steel　　　　　　　　　　　　　　　
N. Sakaguchi, H. Kinoshita, T. Shibayama, H. Takahashi, Proceedings of the 15th International Symposium on Transport Phenomena, 2004年
英語, 記事・総説・解説・論説等（国際会議プロシーディングズ）

Behavior of Defect Clusters by Cascade Damage during Electron Irradiation in Austenitic Stainless Steel　　　　　　　　　　　　　　　
N. Sakaguchi, Y. Sueishi, H. Kinoshita, T. Shibayama, H. Ichinose, H. Takahashi, Proceedings of 8th Asia-Pacific Conference on Electron Microscopy, 700, 2004年
英語, 研究発表ペーパー・要旨（国際会議）

<プロフェッショナル英和辞典 SPED TERRA／物質・工学編小学館プロフェッショナル英和、平成16年7月（ISBN：4-09-506711-X）>　　　　　　　　　　　　　　　
2004年

Effect of Ti implantation in martensitic phase transformation in austenitic 301 stainless steel　　　　　　　　　　　　　　　
D. Gustiono, N. Sakaguchi, T. Shibayama, H. Kinoshita, H. Takahashi, Proceedings of the 4th Pacific Rim International Conference on Advanced Materials and Processing, 1497, 1500, 2001年
英語, 記事・総説・解説・論説等（国際会議プロシーディングズ）

Dynamics of grain boundary movement by in-situ irradiation using atomic resolution HVEM　　　　　　　　　　　　　　　
N. Sakaguchi, S. Watanabe, T. Shibayama, H. Kinoshita, H. Takahashi, Proceedings of the 4th Pacific Rim International Conference on Advanced Materials and Processing, 1485, 1488, 2001年
英語, 記事・総説・解説・論説等（国際会議プロシーディングズ）

Atomistic behavior with segregation at boundary interface under high energy electron irradiation　　　　　　　　　　　　　　　
N. Sakaguchi, T. Shibayama, H. Kinoshita, H. Takahashi, Proceedings of Symposium on Advanced Research of Energy Technology 2001, 365, 370, 2001年
英語, 記事・総説・解説・論説等（国際会議プロシーディングズ）

電子線照射下におけるTi/Cu界面微細組織のその場観察
大田 繁正, 坂口 紀史, 柴山 環樹, 木下 博嗣, 高橋 平七郎, 電子顕微鏡, 35, 106, 106, 2000年05月01日
日本語

高分解能電子顕微鏡像の定量評価-半導体界面における歪緩和機構の可視化-
柴山 環樹, 菅原 敬人, 高橋 平七郎, 電子顕微鏡, 35, 305, 305, 2000年05月01日
日本語

界面への高エネルギーイルミネーション
高橋 平七郎, 坂口 紀史, 柴山 環樹, 電子顕微鏡, 35, 102, 102, 2000年05月01日
日本語

Application of HRTEM to studies of electronic structure and atomic configuration of interface in SiC/SiC composites
T Shibayama, GW He, H Takahashi, A Kohyama, JOURNAL DE PHYSIQUE IV, 10, P6, 97, 103, 2000年04月
The continuous fiber ceramic composite (CFCC), such as SiC/SiC composites have attractive features for advanced energy conversion and production systems, especially gas turbines and fusion power reactors. Because SiC is well known to exhibit a quite fast decay behavior and an excellent oxidation resistance behavior due to the formation of a passive SiO2 layer. The variety of criteria for environmental effects of microstructural evolution at interface of SiC/SiC composites is proposed. Of interest is that the degradation of the composite is observed after annealed at 1500 degrees C under ultra high purity Ar flow condition. However there are few data of nano-structure analyses at interface of SiC/SiC composites. In this work, the environmental effects of microstructural evolution in SiC/SiC composites are examined by a Field Emission type High-Resolution Electron Microscopy (FE-HRTEM) and a Parallel Electron Energy Loss Spectroscopy (PEELS). A possible mechanism for this degradation is discussed and proposed., E D P SCIENCES, 英語

Atomistic observation of irradiation-induced grain boundary migration using multibeam high-voltage electron microscope　　　　　　　　　　　　　　　
N. Sakaguchi, T. Shibayama, H. Kinoshita, H. Takahashi, Proceedings of Symposium on Advanced Research of Energy Technology 2000, 395, 400, 2000年
英語, 記事・総説・解説・論説等（国際会議プロシーディングズ）

Analysis of stress-induced Burgers vector anisotropy in pressurized tube specimens of irradiated ferritic-martensitic steels: JFMS and JLF-1
DS Gelles, A Kimura, T Shibayama, EFFECTS OF RADIATION ON MATERIALS: 19TH INTERNATIONAL SYMPOSIUM, 1366, 535, 547, 2000年, ［査読有り］
A procedure for determining the Burgers vector anisotropy in irradiated ferritic steels is described, allowing identification of all a < 100 > and all a/2 < 111 > dislocations in a region of interest. The necessary micrographs to apply the procedure have been taken of a pressurized tube specimen of JFMS, a duplex ferritic steel following irradiation in FFTF/MOTA at 407 degrees C to 7.5 x 10(22) n/cm(2) (E > 0.1 MeV) or 37.5 dpa, and a pressurized tube of JLF-1 irradiated at 430 degrees C under similar conditions to 14.3 x 10(22) n/cm(2) (E > 0.1 MeV) or 60 dpa. Analysis of micrographs indicates that large anisotropy in Burgers vector populations develop during irradiation creep., AMERICAN SOCIETY TESTING AND MATERIALS, 英語, 記事・総説・解説・論説等（国際会議プロシーディングズ）

マルチビーム超高圧電子顕微鏡による6H-SiC単結晶の動的照射効果その場観察
柴山 環樹, 木下 博嗣, 高橋 平七郎, 大崎 光明, 根本 広司, 電子顕微鏡, 34, 103, 103, 1999年05月01日
日本語

Microstructural stability of SiC/SiC composites under dual-beam ion irradiation
Yutai Katoh, Tatsuya Hinoki, Akira Kohyama, Tamaki Shibayama, Heishichiro Takahashi, Ceramic Engineering and Science Proceedings, 20, 4, 325, 332, 1999年, ［査読有り］
英語

Interface structure analysis of SiC fibres reinforced SIC matrix composites by energy filtering TEM
T Shibayama, GW He, H Takahashi, M Kawasaki, A Kohyama, JOURNAL OF ELECTRON MICROSCOPY, 48, 6, 893, 897, 1999年
Various criteria for environmental effects on microstructural evolution at interfaces of SiC fibres reinforced SiC matrix composites are proposed. Of interest is that degradation of the composite is observed after annealing at 1500 degrees C under ultra high purity Ar flow. However, there are few data of nanostructure analyses at interfaces of SiC/SiC composites. In this work, the environmental effects of microstructural evolution in SiC/SiC composites are examined by a field emission type high-resolution electron microscopy (I;E-HRTEM) and a parallel electron energy loss spectroscopy (PEELS). The elemental distribution in SiC fibres reinforced SiC matrix composites has been investigated by elemental mapping using an energy filtering TEM. A possible mechanism for this degradation is proposed and discussed., OXFORD UNIV PRESS, 英語

Formation of defect cluster under irradiation with electrons/He ions in HVEM connected with an ion accelerator
H Takahashi, Y Hidaka, T Shibayama, ELECTRON MICROSCOPY 1998, VOL 1, 1, 269, 270, 1998年
IOP PUBLISHING LTD, 英語

酸化物分散強化バナジウム合金の開発と照射効果
中島 邦久, 柴山 環樹, 茅野 秀夫, 日本原子力学会誌 = Journal of the Atomic Energy Society of Japan, 37, 4, 338, 345, 1995年04月30日
日本原子力学会, 日本語

放射線場でのマルチ型同時計測法の開発とイノベ―ション物質の創製に向けて
科学研究費助成事業
2021年04月05日 - 2025年03月31日
若井 栄一, 柴山 環樹, 岩元 洋介, 牧村 俊助, 佐藤 紘一, 豊田 晃大, 涌井 隆, 石田 卓, 鬼澤 高志
本研究では、放射線下で生じる様々な物質での照射欠陥の基礎理論の構築のため、放射線場でも物質内部の欠陥状態を電気抵抗（ER）測定、陽電子寿命（PAL）測定、及び応力負荷・計測によって同時計測できるシステム構築を目指している。ER測定系では、電流源及び電圧源の購入、ER測定システムの構築、信号線の試料への接続手法の確立、極低温におけるER測定用冷凍機の購入とシステムの評価を実施した。また、応力を負荷できるパルスレーザーを試料に照射し、金属では欠陥に伴うERが増加し、半導体では電子移動度の上昇に伴うERが低下した。PAL測定系では、陽電子線源と試料が接触しない状態で測定を行えるシステムを構築するために必要なアバランシェフォトダイオード(APD)やデジタルオシロスコープ等を購入し、APDを透過する陽電子の信号を得るための作業を進め、まだシステムの構築段階にあるが、線源と試料が接触した状態では、レーザー照射下で材料に応力負荷の環境下で同時計測を実施できた。
Fe系とW系のハイエントロピー(Fe-HEA、W-HEA）等の作製を試み、Fe-HEAは、磁性を持ち、純Wを超える硬さを持ち、その縦弾性率が鉄系材料と異なり、チタン系材料とほほ同じ値を持つことが分かった。W-HEAは、溶解法により、ほぼ均質な結晶化した合金を作製した。また、HEAをナノ粒子あるいは薄膜化し、触媒やフィルター等の新奇な機能材料として、Arガスのグロー放電による貴金属ターゲットのスパッタリングによってSi基板上のHEA薄膜作製とイオン液体を利用したHEAのナノ粒子作製法を試みた。
メカニカルアロイング(MA)法で作製したW系材料の耐照射性評価やW中に混入するガス分子の機械特性に与える影響の調査を進めた。また、高速炉構造材料の評価では、超高圧電子顕微鏡の電子線照射法により、原子空孔の移動度と粒界析出物の安定性を評価した。
日本学術振興会, 基盤研究(A), 国立研究開発法人日本原子力研究開発機構, 21H04668

ガルバニック水中結晶光合成の学理構築に基づく機能性３次元ヘテロナノ構造体創製
科学研究費助成事業
2020年04月01日 - 2023年03月31日
渡辺 精一, JEEM MELBERT, 柴山 環樹, 岡本 一将, 張 麗華
本研究は、水と光（可視光から紫外光）のみを用いる水中結晶光合成により、常温、大気圧、不純物無、さらに中性の水環境条件においても、金属原料からの酸化物ナノ構造体を一括作製可能にする手法の確立を目指し、将来の太陽光利用によるグリーンサステイナブルな材料生産を最終目的としている。原理的には水のみを用いるため、酸化物と水素しか生成しない、究極的、独創的な新グリーン材料創製手法である水中結晶光合成をさらに発展させ、ガルバニック効果を付与した水中結晶光合成（Galvanic-SPSC)の学理構築をまずは行う。さらに、それに基づく半導体ヘテロ接合機能の特徴を生かした多機能で高効率な光・電子変換機能性を有する３次元ヘテロナノ構造体創製を目指す。
これまで、マスクパターンやメッシュ等を用い所定の箇所に各種金属酸化物のナノ構造を積み上げ、光・電子デバイスや光機能デバイス作製応用を行った。異種金属を使い、光ガルバニック効果（ガルバニック効果と光照射効果）により、各種金属のSPSC最適組み合わせを調査し、疑似太陽光照射を用いながら量子効率評価を行い、光・電子デバイス創製を行なった。
具体的には、光電気化学測定を行い光照射効果による物性変化評価を行い光の波長、照射強度依存性を詳細に定量測定した。また、XPS,XRD,SEM,STEMによる材料組織解析ならびにPL,CLによる発光特性の光物性調査を行った。ヘテロナノ接合界面での特異な格子欠陥を同定するために、PLやCL測定に加えSTEM-EELS、吸光度測定、密度汎関数法に基づく第一原理計算から電子状態密度と誘電率評価を行い、光物性の発現機構を総合的に調査した。
以上の結果を都合8編の論文成果物として公開することができた。今年度は5編、うち2022年一月にプレス発表一件を行うことができた。
日本学術振興会, 基盤研究(A), 北海道大学, 20H00295

SiCセラミックスラスタに高い靱性を付与するハイパー・コンパージド技術
科学研究費助成事業
2019年04月01日 - 2023年03月31日
岸本 弘立, 柴山 環樹, 芹澤 久, 中里 直史, 中田 大将
本研究におけるスラスター製作において複数のSiC/SiCセグメントの統合を必要とする。本年度の実績の大きな項目は以下の3点である。1)形状付与したセグメントの一体化成型は無加圧で実施する必要があり、PIP法で製作した縦方向＋強化セグメントをNITE法で製作した内部セグメントに付与し、2）それらを一体化をRS法で実施する。3）熱伝導度と重量の観点から外部構造のためのC/SiCをNITE法で製作するための検討を行う。1)については2つのNITE SiC/SiC複合材料円管を使用してセグメントの一体化を模擬した技術検討を行った。円管を2つに分割し、2つをあわせた上で縦方向、および円周方向のSiC繊維を追加し、乾燥後に不融化処理を200℃,1h、焼成処理をAr雰囲気中で1200℃、1h実施することで強化セグメントを付与可能であることを示した。2)については1)の強化セグメントをるつぼ内に設置し、Siを1450℃で含侵させることで可能であった。3)はピッチ系およびPAN系の種々の炭素繊維のNITE法プロセス環境での安定性を評価したもので、NITEプロセス中にいずれの繊維も反応を生じ、断面積を減じる。一方で結晶構造により反応する厚さは異なり、全面非晶質の炭素繊維は中央部まで結晶相が成長して容易に破断しやすくなり、強化繊維としての機能を果たさなくなるのに対して、結晶性グラファイトの繊維は繊維表面近傍の結晶成長のみであり、曲げ試験および破面観察の結果からも繊維の強度特性の劣化は少ないものと推定される。一方で多くのマトリックスクラックが導入されるために、成型プロセス条件の最適化が必要であることも示されている。その他、SiC/SiCスラスターの燃焼試験装置は実験施設に設置し、冷却系の整備と水冷条件の調整を実施中である。
日本学術振興会, 基盤研究(A), 室蘭工業大学, 19H00799

量子生命科学的アプローチによる金ナノ粒子の放射線増感効果の解明と最適化への挑戦
科学研究費助成事業
2018年04月01日 - 2022年03月31日
橋本 孝之, 米澤 徹, 柴山 環樹
難治性がんの放射線治療成績向上を目的に金粒子等の体内の金属に対する放射線の影響に関する研究を行った。細胞微細構造内の金粒子を電子顕微鏡で観察する研究は胆振東部地震により超高圧電子顕微鏡が損傷し遅れが生じ、また体内投与可能な金ナノ粒子を用いた陽子線照射実験は、新型コロナウイルス感染の拡大で緊急事態宣言やまん延防止等重点措置が断続的に発出された影響で期間内に実施できなかった。体内金属と放射線との相互作用に関連して、金粒子の放射線増感効果の臨床応用の期待が大きい小児がんの陽子線治療と、ペースメーカー等の植込み型医療機器に対する陽子線と炭素線の影響を比較検討した内容についてそれぞれ論文化した。
日本学術振興会, 基盤研究(C), 北海道大学, 18K07660

格子欠陥レベルで拡散経路を壅蔽する新奇酸化抑制機構の解明　　　　　　　　　　　　　　　
挑戦的研究(萌芽)
2019年07月 - 2022年03月
柴山 環樹
日本学術振興会, 研究代表者, 競争的資金

ＴＥＭ－ＳＴＭその場計測による抵抗変化メモリの動作機構解明
科学研究費助成事業
2013年04月01日 - 2016年03月31日
有田 正志, 高橋 庸夫, 末岡 和久, 柴山 環樹, 工藤 昌輝, 大野 裕輝, 高橋 謙仁, 平田 周一郎, 村上 暢介, 越智 隼人, 米坂 瞭太, 武藤 恵, 中根 明俊, 廣井 孝弘, 勝村 玲音, 森 雄司
抵抗変化メモリ（ReRAM）がbeyond CMOSを目指して研究・開発されている．その動作原理の解明は最重要課題であり，電気化学に基づくモデルの提唱はあるが，不明な点が多い．本研究では，その場透過電子顕微鏡法により金属フィラメント型ReRAM内の微細構造を実時間観察した．その結果，高抵抗⇔低抵抗（Set，Reset）の動作時には大きな変化はなく，追加の通電により大きな構造変化の生じる事が分かった．ナノ領域での変化が抵抗スイッチに寄与している．大きな構造変化はスイッチ箇所の不安定化，金属イオンの固溶を促進し，劣化を生じた．Set，Reset時の投入電力バランスが安定動作に重要であると言える．
日本学術振興会, 基盤研究(C), 北海道大学, 25420279

粒界工学による超環境耐久性フェライト系耐熱鋼の開発－粒界工学の新たな挑戦
科学研究費助成事業
2012年04月01日 - 2016年03月31日
連川 貞弘, 渡辺 精一, 柴山 環樹, 森園 靖浩, 山室 賢輝
本研究課題では，優れた環境耐久性を有するフェライト系耐熱鋼の開発を行うことを目的として，ラスマルテンサイト組織を有する9-12Cr系耐熱鋼の粒界制御を試みた。ラスマルテンサイト鋼における特性劣化の優先的なサイトとなる旧オーステナイト粒界の対応粒界頻度を飛躍的に高めることができた。また，粒界制御熱処理によりサブブロック組織が微細化し，その後の焼戻し処理により，M23C6炭化物が微細に分散することを見出した。このような粒界制御材料に対して，高温クリープ試験，高温水蒸気酸化試験，液体金属腐食試験を行ったところ，いずれの特性も粒界制御により著しく向上することが明らかとなった。
日本学術振興会, 基盤研究(A), 熊本大学, 24246125

マルチ量子ビーム照射によるディウェッティング現象その場観察とその機構解明
科学研究費補助金(基盤研究(C))
2014年 - 2016年
柴山 環樹
本研究では、北海道大学の複合量子ビーム超高圧電子顕微鏡を利用し量子ビーム照射誘起Dewetting 現象についてその場観察し画像解析からその機構を解明することを目的とし、100keVのArイオンと波長532nm の短パルスレーザーの複合照射下及びそれぞれ単独での照射下におけるDewetting 現象のその場観察を行った。
その結果、貴金属が矩形から球形へ変化するレイリー不安定時の挙動を直接観察することに成功すると共に、貴金属薄膜厚が薄いほどDewetting後のナノ粒子の平均粒径は小さくなり、可視光の吸収波長も短波長側へブルーシフトする量子効果が発現することを確認した。
文部科学省, 基盤研究(C), 北海道大学, 研究代表者, 競争的資金, 26420661

高強度チタン合金における内部起点型微小き裂の可視化と超高サイクル疲労機構の解明
科学研究費助成事業
2012年04月01日 - 2015年03月31日
中村 孝, 柴山 環樹, 塩澤 大輝, 中井 善一, 上杉 健太朗, 小熊 博幸, 渡辺 精一
超高サイクル域における軸荷重疲労試験が行われ，放射光μCTイメージングにより材料内部に発生する微小き裂が観察された．内部き裂周囲の環境がき裂進展に及ぼす影響を明らかにするため，da/dNと応力拡大係数範囲の関係が測定され，真空中表面き裂のそれと比較された．その結果，内部き裂は1.0E-10m/cycleの極めて低速で進展するのに対し，表面に到達した後のき裂は1.0E-7m/cycle 程度の高速で進展することがわかった．内部き裂の進展速度は真空中表面き裂の進展速度に一致し，内部き裂周囲の真空に類似した環境が超高サイクル疲労における内部き裂進展過程に大きな影響を与えることが明らかとなった．
日本学術振興会, 基盤研究(A), 北海道大学, 24246024

透過電子顕微鏡その場計測システムの開発とナノエレクトロニクスへの応用
科学研究費助成事業
2009年 - 2011年
有田 正志, 高橋 庸夫, 末岡 和久, 柴山 環樹
近年,マイクロ・ナノ領域での幾何学的構造変化現象,磁気的微細構造変化現象を用いたデバイス開発が行われている.本研究では,透過電子顕微鏡(TEM)その場計測手法をこれらの研究に役立てるために,ピエゾ駆動TEMホルダー(TEM-STMホルダー),磁場印加用コイル搭載TEMホルダー(TEM-MFホルダー)およびそのシステムを開発した.これらを抵抗変化メモリー(ReRAM)および磁区パターンに応用し,その有用性を確認した.ReRAM材料においては抵抗スイッチ時の導電性フィラメントの形成・消失を,また磁性パターン膜においては磁場印加による磁壁移動を実時間計測により確認できた.
日本学術振興会, 基盤研究(C), 北海道大学, 21560681

ナノ時空間ダイナミクスのその場観察法による物質変換過程の解明
科学研究費補助金(基盤研究(A))
2009年 - 2011年
柴山 環樹, 渡辺 精一, 谷津 茂男, 伊藤 芳浩, 富岡 智, 西山 修輔, 坂口 紀史
本研究は、これまで透過電子顕微鏡で唯一の課題となっていた画像記録の高速化と長時間化についてピコ秒の現象であるレーザー核融合のターゲット計測に実績がある各種高速カメラを組み合わせたナノ時空間ダイナミクスその場観察システムの技術開発を行うことを目的として平成21年度から平成23年度まで3年計画で実施した。この新しく開発した装置を現有の透過電子顕微鏡に取り付けて、電子線やイオン照射下での接合界面における破壊の起点やマルチクラックの進展経路をこれまでは困難だったナノ時空間で記録しその場観察すると共に高速で発生し進展するマルチクラックとナノサイズ欠陥との相互作用を明らかにした。
文部科学省, 基盤研究(A), 北海道大学, 研究代表者, 競争的資金, 21241025

材料損傷機構の実験および理論による包括的研究と高エネルギー量子ビーム場用材料開発
科学研究費助成事業
2007年 - 2010年
川合 將義, 渡辺 精一, 粉川 博之, 川崎 亮, 長谷川 晃, 栗下 裕明, 菊地 賢司, 義家 敏正, 神山 崇, 原 信義, 山村 力, 二川 正敏, 深堀 智生, 斎藤 滋, 前川 克廣, 伊藤 高啓, 後藤 琢也, 佐藤 紘一, 橋本 敏, 寺澤 倫孝, 渡辺 幸信, 徐 超男, 石野 栞, 柴山 環樹, 坂口 紀史, 島川 聡司, 直江 崇, 岩瀬 宏, 兼子 佳久, 岸田 逸平, 竹中 信幸, 仲井 清眞
高エネルギー高強度陽子ビーム場の材料は、強烈な熱衝撃や放射線によって損傷を受ける。衝撃損傷過程と影響を実験的に調べ、その緩和法を導いた。また放射線損傷を理論的に評価するコードを開発した。さらに、損傷に強い材料として従来の材料に比べて強度の4倍高く室温で延性を持つタングステン材と耐食性が4倍高いステンレス鋼を開発した。衝撃実験における応力発光材を用いた定量的な方法を考案し、実用化の目処を得た。
日本学術振興会, 基盤研究(S), 大学共同利用機関法人高エネルギー加速器研究機構, 19106017

室温動作の単電子デバイス開発を指向したTEM/STMによる単電子トンネル現象研究
科学研究費助成事業
2006年 - 2008年
有田 正志, 高橋 庸夫, 末岡 和久, 柴山 環樹
省エネデバイスとして注目されている単電子デバイスの室温動作確認を念頭に,ピエゾ素子搭載型透過電子顕微鏡ホルダー(TEM/STMホルダー)およびその制御システムを開発した.先端10nm程度の先鋭電極間に数個のナノ粒子を挟み,その電気伝導特性を評価したところ低バイアス領域においてほとんど電流が流れないクーロンプロッケイド(CB(を観測できた。これは単電子トンネル現象(SET(に特徴的な現象である.数nmのナノ粒子を用いて室温動作SETデバイスの得られることを実験的に示すことができたといえる.
日本学術振興会, 基盤研究(C), 北海道大学, 18560640

超高速CCDカメラによる結晶中の格子欠陥のナノダイナミクスTEM内その場観察
科学研究費補助金(基盤研究(B))
2004年 - 2006年
柴山 環樹, 木下 博嗣, 坂口 紀史, 江藤 剛治
平成16年度から平成18年度の3ヵ年にわたって共同研究者が開発した超高速カメラを現有の超高圧電子顕微鏡及び電界放射型分析透過電子顕微鏡に接続するための光学系及び実験手法などを開発し材料科学における高速現象を明らかにするために主たる研究を行った。平成18年度は、SiC/SiC複合材料の照射欠陥やクラック進展に関して高速観察を行った。更に3ヵ年計画の最終年度としてこれまでの成果を基に総まとめを行った。総合的に評価すると当初の目標に対して実験の進捗が計画通り進まなかったこともあり達成度は70%程度と推測されるが本研究の目的は十分明らかにしたと考えられる。また、ドイツにおいてレーザーを金属固体に照射し高強度な庵子を発生させる新しい概念に基づくパルス電子光源の開発がなされた。この電子源を改良し通常の電子顕微鏡の電子銃と交換した新しい電子顕微鏡が米国にて開発され、平成18年9月に札幌にて開催された国際顕微鏡学会にて報告された。既に材料科学のいくつかのトピックスに関して研究がなされており口頭やポスターでの発表があった。本研究は、一般的な連続して電子を発生する熱電子源及び電界放出電子源を使用しており、画像情報記録媒体側を高速記録型のCCDにすることで超高速化を狙っているのに対し米国の装置は、電子源をパルス化して記録側は通常の記録装置である。つまり、ストロボ的に高速現象をコマ取りして一連の高速現象を理解するという考え方である。しかしながら、ある現象の起点を知るためにはわれわれの方式の方に利点があり今後の展開が期待される。以上、国際的に見ても本研究はこの分野において先端領域に位置づけられ今後継続してプロジェクト研究を進めるべきである。また、3ヵ年に渡る本研究を通じて新たな課題が見つかったことから次のプロジェクトに向けて準備が整ったといえる。
文部科学省, 基盤研究(B), 北海道大学, 研究代表者, 競争的資金, 16360310

生体硬組織結晶の発現機構と成長に関する三次元的超微構造の解明
科学研究費助成事業
2003年 - 2006年
脇田 稔, 山本 恒之, 土門 卓文, 高橋 茂, 柴山 環樹, 高橋 平七郎
当初目的とした凍結超ミクロトーム法は、研究最終年度に至るまで、本研究の目的に合致する機器を使用することができなかったので、メタアクリル樹脂包埋法によって観察試料の作成をおこなった。
前年までの概要報告にあるとおり、本研究では、揮発性の高い樹脂モノマーを重合するために、多くの工夫を発見した。一つは、試料ビンを密封重合容器として利用する方法である。これにより、重合前ならびに重合期間中のモノマーの揮発を最小限に押さえることができた。この時、試料が最終的に重合した樹脂ブロックの中央に来るよう、予め容器の中で最終量の半量の樹脂を重合させておき、その上に資料を載せ、残りの半量を重合させるという2段階の重合操作を行うことを工夫した。ただし、この方法によるとその後の試料作成操作において、試料が比較的大きな樹脂ブロックの中にあるので、切り出しまで時間がかかり、またアクリルブロックはノコギリ等で切り出すことは簡単であるが、切り出し作業の途中で試料の方向性を失わないよう恒に確認しつつ作業することが必要であることがわかった。この確認作業は昨年度まではブロックの方向を示す特定の形態を与え、その形を保存しながら整形咲いていたが、今年度は、この方法に整形途中でブロック側面を研磨して透明とし、何度も内部の試料の方向を確認しつつ背軽作業を行った。この方法は従来よりも煩雑で時間がかかるが、精密な試料の方向性を維持する方法としては優れていると考えた。さらに準超薄切片作成時に行う試料の方向の最終確認が短時間で済み、結果として超薄切までの時間は、一個の試料だけを考えればほぼ同じであった。
アクリル樹脂超薄切片を、脱包埋するために超薄切片をスライドグラス上に貼りつけるための適当な方法は最後まで解決できなかった。当初エポキシ樹脂を薄く塗り、その上に超薄切片を載せ、エポキシ樹脂重合完了後モノマーで超薄切片の脱包埋を行うことを試みたが、エポキシ樹脂の膨化を止める方法が見つからなかった。
全体として、当初の研究遂行に当たり、上記のような想定外の問題克服に時間がかかり過ぎ、本実験まで到達できなかった。しかしながら、今回の4年間にわたる研究の結果、上記のように本来の目的を達成することは種々の理由によりできなかったが、分担研究者は本研究を分担するとともに分担者個々の本来の研究を実施した結果、別に提出する「平成15年度科学研究補助金(基盤研究(B))研究成果報告書」に示すように多くの優れた研究成果を挙げることができた。
日本学術振興会, 基盤研究(B), 北海道大学, 15390548

超高圧電子顕微鏡を用いた生体膜の三次元超微構造に関する研究
科学研究費助成事業
2003年 - 2005年
脇田 稔, 山本 恒之, 土門 卓文, 高橋 茂, 柴山 環樹, 高橋 平七郎
本年度は、昨年に続いて、クライオミクロトームの利用がほとんど不可能なことが明らかになったので、代替手段として、化学的固定による方法を資料作成のために応用することを引き続き試みた。標本を脱樹脂により観察するという本研究の特徴を実現するために、試料は全て、メタアクリレート樹脂あるいはブチルーメチルメタアクリレート樹脂に包埋した。アクリル樹脂モノマーは揮発性が高く、通常の方法では、重合作業中に蒸発するという致命的な欠陥があるので、今回は、半重合樹脂にモノマーの浸透が終了した試料を報マイすることをこころみた。試料は従来の透過電顕用試料より大きく、特に走査電顕用試料はかなり大きいので、通常の揮発性樹脂の包埋に使われる蓋付きポリエチレンカプセルでは不便なので、脱水や樹脂浸透に用いるガラス製試料ビンに包埋する方法によって包埋した。この方法は便か一度しか使えないと言う欠点があるが、アクリレート樹脂のような揮発性の強い包埋材の場合祐子菜穂右方と考えられる。ただし、この場合、試料は重合前のモノマーの中で沈むので、前年度と同様、重合樹脂ブロックの中程に試料が来るようにするために、試料ビンに1cmほどのモノマーを入れて重合した後、樹脂浸透の終了した試料を置き、静かに触媒入りモノマーを1cm〜1.5cmそそぎ入れ、蓋をして重合した。重合完了後、ガラスビンを割って重合試料ブロックを取り出す。ただし、半重合樹脂では、空気の混入が生じることが多く、重合中に樹脂そのものが発泡するという重大な欠点があり、あらかじめ、十分に脱気する必要があることがわかった。
このブロックから試料を任意の方向から切り出すことが可能であるが、大きな切片の切り出しは極めて困難で、期間中に十分な成果を挙げることができなかった。
共同研究者の教室では、超高圧電子顕微鏡による表面触媒の解析に関する業績が得られた。
日本学術振興会, 萌芽研究, 北海道大学, 15659432

量子剥離超薄片化装置の開発
科学研究費助成事業
2000年 - 2003年
市野瀬 英喜, 柴山 環樹, 幾原 雄一, 須賀 唯知, 高橋 平七郎, 岩本 知広
ナノテクノロジーに不可欠な電子顕微鏡情報の、原子構造情報の質と信頼度を格段に向上させることにより、電子デバイスの開発、設計、製造の各過程などをめくら撃ち手探り状態から解放し、他方では、現在米国に独占されている、電子顕微鏡観察用薄片化技術市場を奪還することを狙う。高速イオンではなく波長分散の小さい、短波長の電磁波を用い、物質の結合エネルギーに同調照射させることによって、物質に損傷を与えることなく原子間結合を切断し、表面近傍の原子を順次剥離することをめざす。すでに、レーザーパワーの超精密制御系と微小領域への精密照射光学系の開発、適用物質範囲の拡大は、相当の進展を見た(レーザースキャン技術)。即ち、(1)イオンガンとレーザーガン両備量子効果原子剥離反応薄片化研究機システムを構築した。これを用いて、下の実験を通してエネルギー密度や光学パラメータのを最適化のデータを収集した。(2)λ=19ナノメートルにレーザー波長を固定して、シリコンカーバイド(2原子共有結合物質)、ダイヤモンド(単原子共有結合物質)、について薄片加速度を検証し既知のシリコンと比較検討し、最適な条件を、パルス幅、エネルギー密度、照射回数、について絞り込むことが出来た。また(3)表面から飛散する原子が一つずつ飛び出しているのか、集団で飛び出しているのか、そうだとすれば原子集団の規模はどの程度かという、表面性状に直接関わる詳細な情報の収集を始め、ある程度の指針を得た。(4)これと並行して、製品につながるプロトタイプの設計が終了した。今後は、JSTのプロジェクトに引き継ぎ具体的に商品化を図る予定である。
日本学術振興会, 基盤研究(A), 12355024

核融合炉プラズマ対向機器用タングステン合金の開発
科学研究費助成事業
1997年 - 1999年
栗下 裕明, 瀧田 朋広, 湯蓋 邦夫, 平岡 裕, 柴山 環樹
核融合炉用高熱流束機器として必要な特性を最も多く備えているWの課題は,脆さ(低温脆化,再結晶脆化,照射脆化)の改善である。これらの3つの脆さを同時に大幅に改善するには,遷移金属炭化物粒子の粒界分散および結晶粒の微細化が最も有効であると考えられる。そこで,そのような組織を得るために,遊星型ボールミルを用いたメカニカルアロイング(MA)法と熱間等方加圧(HIP)法によりW合金の試作を行った。添加した遷移金属炭化物は周期律表IVa族のTiCとHfC,およびVa族のTaCとNbCである。試作したW合金について衝撃3点曲げ試験による低温靭性の評価,真空加熱における再結晶温度の評価,照射脆化を評価するための高速中性子照射実験と照射後試験,および照射前後と真空加熱前後における微細組織の観察を行った。その結果,TiCを添加した試作合金で最も特性が改善された。例えば,0.2%TiC添加材は市販の純WやW合金に比べて,延性脆性遷移温度が著しく低く(l00℃以上),再結晶温度が600℃も上昇した。0.5%TiC添加材では再結晶温度はさらに上昇した。また,Wの脆さの中で最大の課題である照射脆化の改善については,照射硬化の抑制だけでは改善は困難であること,照射中に起こる組織変化(照射誘起析出,照射促進析出)を活用して組織の中で最も弱い個所(weakest points : 粒界等)を強化する必要があること,ただしそれ自体が脆く破壊の起点として作用するW_2Cが照射中に析出しないような合金組成を選択することが必要であることが明らかになった。以上の結果は,本研究で用いた合金設計と組織制御の方法がWの3つの脆さを同時に大幅に改善するために極めて有効であることを示している。
日本学術振興会, 基盤研究(B), 東北大学, 09558061

高エネルギー粒子線照射環境に適応した機能性鉄鋼材料開発研究
科学研究費助成事業
1997年 - 1998年
高橋 平七郎, 万 発栄, 胡 本芙, 木下 博嗣, 柴山 環樹, 渡辺 精一
1. 電子線照射によりステンレス鋼中には積層欠陥型転位ループが形成され、照射を継続すると積層欠陥転位ループ内に原子空孔型の積層欠陥四面体が形成された。電子線/Heイオン同時照射では、最初に積層欠陥四面体が形成され、その後この積層欠陥四面体はボイドの核となり、Heがボイド核を安定化されることが判明した。
2. Fe-(15-16)%Cr-16%Mn-0.2%C-0.2%N鋼の室温の降伏強度は400MPaで、伸びは60%以上の優れた機械的性質を示した。この鋼を473-673K、3dpaまで電子線照射すると、最初に転位ループが形成され、その後、473-573Kではボイドは形成されなかったが、673Kではボイドが核形成した。Mn濃度、24.5%のMn鋼を照射すると、473K-673Kの全ての照射温度範囲で高密度でボイドが核生成した。573Kではマトリックス、結晶粒界とも照射下で相が安定であった。照射温度573K以上では素地のオーステナイト相は変化しなかったが、素地中に微細な炭化物の析出が認められ,高温度では照射により析出物が促進されることが明らかになった。
3. W,Vを添加した低放射化Fe-Cr-Mn(W,V)合金を電子線/ヘリウムで二重照射した結果、転位ループやボイド等の2次欠陥が形成され、次第にその密度が増大した。特に、高温照射の場合に、ボイドは転位線上に優先的に形成された。また、この鋼ではCr、Mnの粒界シンクにおける偏析は検出されず,照射誘起偏析が抑制されることが明らかになり、W、V添加効果が偏析抑制に有効であることが示唆された。
4. Fe-Cr-Mn(W,V)合金を527-723Kで10dpaまで電子線照射した結果,(a)ボイドスエリング挙動は溶接熱影響部での耐照射特性は625K照射では優れた特性を示した。さらに高温度で照射すると微細なボイドが核形成し,ボイド抑制効果が顕著でなかった。
5. 同合金をlOdpaまで照射した後の結晶粒界におけるCr、Niの偏析はW,Vの添加しないFe-Cr-Mn合金と比較し、その偏析量は少ないがNiの濃化とCrの枯渇が認められた。
6. Fe-(13-16)Cr-(6.5-24.5)Mn-(0.02-0.2)C-0.2N-(0.3-0.5)Si合金について、熱処理及び電子線照射した結果、次のことが明らかになった。
(a) 低Mn含有のマンガン合金鋼の単一γ相はCr、C、N濃度を制御することによって得られることが明らかにされた。
(b) 本研究で開発された、15-16wt%Cr-15.5wt%Mn-(0.02-0.2)wt%C-0.2wt%N合金は、高強度で高い伸びを示す良好な機械的性質を有することが確認された。
(c) ボイド核形成はCrとCの濃度が増大すると抑制され、Fe-16wtCr-15.5wt%Mn-0.2wt%C-0,2wt%N合金鋼では照射温度473-673Kで完全にボイド核形成が抑制された。
日本学術振興会, 国際学術研究, 北海道大学, 09045042

レーザー照射による酸化物分散強化傾斜機能材料開発に関する研究
科学研究費補助金(奨励研究(A))
1994年 - 1994年
柴山 環樹
レーザー照射は、局所的に融点直下まで瞬時に加熱出来、照射を中止することにより急速冷却が可能である。その、特徴を用いて従来にない機能を発現する材料の開発が試みられている。一方、酸化物分散強化鋼は高温強化だけでなく耐照射特性に優れていることが明らかになってきた。しかしながら、強加工に起因する強度の異方性が構造材料に適用する場合、問題となっている。そこで、本研究ではレーザー照射を酸化物分散強化鋼にの表面改質に適用し強度の異方性を改善すること及び高温材料として期待されているTiALと接合し耐照射性及び高温強度にも優れた傾斜機能材料の開発に関する基礎的知見を得る事を目的とした。TiAlとの接合には、昨年度実施した奨励研究(A)において試みたTi、Al多層膜にレーザー照射を行うことによって合金化する事を適用し接合界面における組成の傾斜化を検討した。供試材として市販のMA957酸化物分散強化鋼を用いた。試料の形状は、棒鋼で30Ф×100である。レーザー照射には、3kW炭酸ガスレーザー加工機を本研究費で購入したコンピューターで制御し用いた。押し出し方向に対して平行と垂直に棒鋼をレーザー照射した。いずれの表面も、加工ガスがレーザー照射方向に吹き付けられるため急速溶解凝固した液的状の組織を呈していた。レーザ照射による熱影響を知らべるためそれぞれの切断方向に対し垂直に切断し金相観察を行った。表面から数μmの領域には、微細な空孔が観察出来た。しかし、それ以降の領域には観察出来ずほぼレーザー照射前と同様の組織を呈していた。そこで、400kV高分解能分析電子顕微鏡を用いて微細組織の同定を行ったところ、表面部分の組織は加工組織が消滅しほぼラス状のベイナイトを形成しており組織からは表面部分の組織の異方性は改質されたと考えられる。また、所々非晶質が観察されレーザー照射による非平衡相形成が認められた。
文部科学省, 奨励研究(A), 東北大学, 研究代表者, 競争的資金, 06750702

レーザー照射による金属間化合物の機械的特性向上に関する研究
科学研究費補助金(奨励研究(A))
1993年 - 1993年
柴山 環樹
レーザー照射は、従来の加熱装置に比べ急速加熱し急速冷却出来ることから従来にない機能を発現する新材料の開発手段として有効である。そこで、本研究は高温強度に優れ重量比強度が高い金属化合物の合金粉末作製にレーザー照射を適用すること、及び多層膜にレーザー照射を行い金属間化合物を作製することによって機械的特性を向上させ原子力材料としての適合性を明らかにすることを目的とした。科学研究費補助金で購入した市販のチタン板とアルミ板を積層させロータリーポンプで排気したチャンバー内に固定し、3KWの炭酸ガスレーザーを試料表面が焦点面になるようにして照射した。加工ガスには、窒素ガスを用いた。レーザー直下に設置した金型に吹き付けることによって得られた合金粉末の形状を調べるために走査電子顕微鏡で観察した結果、ほぼ球形で数mumの大きさであることがわかった。合金粉末の組成を調べるためにX線回折を行った結果、Ti_3Al及びTiAl,Al_3Tiが形成していることが判明した。その合金粉末を一軸冷間プレスを行って成形し、科学研究費補助金で購入した精密低速切断装置を用いて薄片化し電解研磨の後高分解能電子顕微鏡で微細組織観察を行った。制限視野電子回折像は、デバイシェーラー環と複数の斑点を示し組織が非常に微細で複数の相が混在していることを示唆された。タンデム型加速器を用いて3MeVのAu^<2+>イオンを540℃で約250dpaまで照射した結果、更に結晶粒は微細化しボイドは観察されなかった。今後、更に高温で照射実験を行い現在中性子照射中の試料と共に組織変化と機械的特性の変化について研究する計画である。以上、本研究においてチタンとアルミを積層させた多層膜にレーザーを照射することによってTi_3Al及びTiAl,Al_3Ti層を含む微細結晶粒の金属間化合物粉末を作製できることが明らかとなった。
文部科学省, 奨励研究(A), 東北大学, 研究代表者, 競争的資金, 05750590

ナノ構造材料の組織制御と革新的機能発現，超高速物質移動現象の可視化　　　　　　　　　　　　　　　
競争的資金

utilization of innovative properties by control of nano structure in materials, visualization of ultra high speed phenomena in solid state　　　　　　　　　　　　　　　
競争的資金

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