基本情報

所属

• 工学研究院　附属エネルギー・マテリアル融合領域研究センター　光・熱エネルギー変換材料分野

職名

• 教授

学位

• 理学博士（Ph.D.）（State University of New York at Buffalo）
• 修士（北海道大学）

ホームページURL

https://www.eng.hokudai.ac.jp/labo/carem/lhtm/
https://www.eng.hokudai.ac.jp/labo/carem/lhtm/en/

科研費研究者番号

• 60241353

ORCID ID

•  https://orcid.org/0000-0002-4843-7493

Researcher ID

• E-2622-2012

J-Global ID

• 200901080369659555

研究キーワード

• ナノテクノロジー   光化学   光物性   材料物性   量子ビーム科学   照射効果   ナノ材料   非平衡材料   Nonequilibrium Physics and Chemistry   Materials Science   

研究分野

• ナノテク・材料 / エネルギー化学 / グリーンエネルギー
• ナノテク・材料 / 光工学、光量子科学 / 光物性
• ナノテク・材料 / 基礎物理化学 / 光化学
• ナノテク・材料 / グリーンサステイナブルケミストリー、環境化学 / 結晶光合成
• ナノテク・材料 / 金属材料物性
• ナノテク・材料 / ナノ構造物理
• ナノテク・材料 / ナノ構造化学

担当教育組織

•  学士課程　工学部
•  修士課程　工学院
•  博士課程　工学院

職歴

• 2019年04月 - 現在 北海道大学 大学院 工学研究院 エネルギー・マテリアル融合領域研究センター センター長
• 2012年 - 現在 北海道大学 電子科学研究所 グリーンナノテクノロジー研究ｾﾝﾀｰ 教授（兼務）
• 2010年 - 現在 北海道大学 大学院 工学研究院 エネルギー・マテリアル融合領域研究センター 教授
• 2013年 九州大学 工学部 非常勤講師
• 2005年 - 2010年 北海道大学 エネルギー変換マテリアル研究センター 教授
• 2005年 - 2006年 東北大学 学際科学国際高等研究センター 客員教授
• 1997年 - 2005年 北海道大学大学院工学研究科 助教授 助教授
• 1997年 - 2005年 Hokkaido University Faculty of Engineering Associate Professor
• 1994年 - 1997年 北海道大学エネルギー先端工学研究センター 助手
• 1994年 - 1997年 Research Associate,CARET, Hokkaido University
• 1992年 - 1994年 北海道大学工学部 助手
• 1992年 - 1994年 Research Associate,1992 - 1994 Research Associate, Metals Research Institute, Hokkaido University

学歴

•         - 1993年   ニューヨーク州立大学バッファロー校   大学院博士課程(Ph.D)修了   物理
•         - 1993年   State Unversity of New York at Buffalo
•         - 1987年   北海道大学   工学研究科   修士課程金属工学専攻
•         - 1985年   北海道大学   工学部   金属工学科

所属学協会

• 光化学協会   応用物理学会   日本鉄鋼協会   日本金属学会   日本顕微鏡学会   米国物理学会(APS)   米国材料学会(MRS)   Atomic Energy Society of Japan   Physical Society of Japan   Materials Research Society   Japanese Society of Microscopy   Japan Institute of Metals   American Physical Society   

研究活動情報

論文

• Submerged photosynthesis of TiO2-CuO hetero-nanoparticles and their multiple applications for water issues under solar light

  Zhehan Yu, Shilei Zhu, Lihua Zhang, Seiichi Watanabe

  Journal of Alloys and Compounds 992 174624 - 174624 2024年07月
• Fabrication of ZnO/CuO nanoforests and their applicability to microbial photoelectrochemical cells

  Ryosuke Matsuo, Yuki Takahashi, Seiichi Watanabe, Satoshi Okabe

  Applied Catalysis B: Environmental 339 123097 - 123097 2023年12月 [査読有り]
  
• Quantitative Evaluation of the Diffusion Coefficients of Aqua Ions in Hydrogels via Iron Corrosion

  Satoshi Takai, Shuntaro Murakami, Lihua Zhang, Kenichi Ohsasa, Seiichi Watanabe

  ACS Applied Engineering Materials 1 1 80 - 86 2023年09月13日 [査読有り]
  
• Defect Driven Opto‐Critical Phases Tuned for All‐Solar Utilization

  Melbert Jeem, Ayaka Hayano, Hiroto Miyashita, Mahiro Nishimura, Kohei Fukuroi, Hsueh‐I Lin, Lihua Zhang, Seiichi Watanabe

  Advanced Materials 2023年07月29日 [査読有り]
  
• Submerged Photosynthesis of Molybdenum–Tungsten Nanostructures for Supercapacitor Application

  Hsueh-I Lin, Melbert Jeem, Lihua Zhang, Seiichi Watanabe

  ACS Applied Nano Materials 2023年05月11日
• Facile modification of TiO2 nanoparticles with H2O2 + NH4F for enhanced visible light photodegradation of rhodamine B and methylene blue

  Zhehan Yu, Lihua Zhang, Seiichi Watanabe

  Materials Today Communications 33 104213 - 104213 2022年12月 [査読有り]
  
• 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 2022年08月16日 [査読有り]
  
• Mesoporous single crystal titanium oxide microparticles for enhanced visible light photodegradation

  Zhehan Yu, Shilei Zhu, Lihua Zhang, Seiichi Watanabe

  Optical Materials 127 112297 - 112297 2022年05月 [査読有り]
  
• The origin of opto-functional enhancement in ZnO/CuO nanoforest structure fabricated by submerged photosynthesis

  Yuki Takahashi, Melbert Jeem, Lihua Zhang, Seiichi Watanabe

  Applied Materials Today 26 101359 - 101359 2022年03月 [査読有り]
  
• Fabrication of color-toned micro/nanopattern surface by submerged photosynthesis method

  Jumpei Tsukamura, Yuki Takahashi, Lihua Zhang, Melbert Jeem, Kazumasa Okamoto, Seiichi Watanabe

  Microelectronic Engineering 256 111727 - 111727 2022年02月03日 [査読有り]
  
• 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 2022年02月 [査読有り]
  
• Selective fabrication of tungsten nano-oxides via submerged photosynthesis with hydrogen peroxide for chromic device application

  Souta Fujii, Shuntaro Murakami, Lihua Zhang, Seiichi Watanabe

  Materials Letters 302 130344 - 130344 2021年11月 

  Tungsten nano-oxides of WO3 and H2WO4 have been studied as promising candidates for photocatalytic and chromic materials. To date, WO3 and H2WO4 nanoparticles are generally prepared by hydrothermal synthesis, which requires high temperature environment and pH adjustment. In this paper, we report on fabricating WO3 nanoparticles via photosynthesis by UV irradiation of the solution made from dissolving tungsten in hydrogen peroxide. Similarly, we have succeeded in fabricating H2WO4 nanoparticles by changing the concentration of hydrogen peroxide solution. Furthermore, an electrochromic device was fabricated by coating the WO3 nanoparticles on an ITO substrate, and the chromic properties are then confirmed.
• Molten salt-assisted shape modification of CaFe2O4 nanorods for highly efficient photocatalytic degradation of methylene blue

  Longfei Guo, Noriyuki Okinaka, Lihua Zhang, Seiichi Watanabe

  Optical Materials 119 111295 - 111295 2021年09月
• Solution Plasma-Synthesized Black TiO2 Nanoparticles for Solar–Thermal Water Evaporation

  Shilei Zhu, Zhehan Yu, Lihua Zhang, Seiichi Watanabe

  ACS Applied Nano Materials 4 4 3940 - 3948 2021年04月23日 [査読有り]
  
• Facile synthesis of ZnFe2O4/SnO2 composites for efficient photocatalytic degradation of methylene blue

  Longfei Guo, Noriyuki Okinaka, Lihua Zhang, Seiichi Watanabe

  Materials Chemistry and Physics 262 124273 - 124273 2021年04月 [査読有り]
  
• Synthesis of yellow persistent phosphor garnet by mixed fuel solution combustion synthesis and its characteristic

  Tomoya Gotoh, Melbert Jeem, Lihua Zhang, Noriyuki Okinaka, Seiichi Watanabe

  Journal of Physics and Chemistry of Solids 142 109436 - 109436 2020年07月 [査読有り]
  
• 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 2020年04月 

  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.
• Light and Shadow Effects in the Submerged Photolytic Synthesis of Micropatterned CuO Nanoflowers and ZnO Nanorods as Optoelectronic Surfaces

  Junichi Mizuno, Melbert Jeem, Yuki Takahashi, Masaya Kawamoto, Kiyotaka Asakura, Seiichi Watanabe

  ACS Applied Nano Materials 3 2 1783 - 1791 2020年02月28日 [査読有り]
  
• Visualization of aquaionic splitting via iron corrosion

  Murakami, S., Zhang, L., Watanabe, S.

  Scientific Reports 10 1 2020年02月03日 [査読有り]
   

  We report a water decomposition mode called ‘Aquaionic Splitting (AiS)’ by means of iron corrosion in aqueous solution. In this paper, we investigated the phenomenon by controlling the reaction between iron and water. A pseudo-sacrificial protection method with oil paint was employed to select the anode and cathode formation locations that govern iron corrosion. Then, the AiS reaction was visualized by using BTB solution, whose colour corresponds to pH, to produce colour patterning that corresponds to the aquaion distribution. It has become clear that water can be selectively separated into protons and hydroxide ions by corrosion control treatment. In this vein, the diffusion coefficient of protons was estimated by using the colour patterning of BTB solution that accompanies iron corrosion, and aquaion distribution was then computer simulated by solving the diffusion equation.
• Microstructure modification of additively manufactured cocrfeniti-based multi-principal element alloy

  Kosuke Kuwabara, Yuzo Daigo, Kazuya Shinagawa, Seiichi Watanabe, Tadashi Fujieda

  NACE - International Corrosion Conference Series 2020-June 2020年 

  Microstructure modification of CoCrFeNiTi-based multi-principal element alloy (MPEA) manufactured by selective laser melting (SLM) is conducted to obtain high-strength and corrosion resistant alloys for harsh environments. Mechanical properties are improved by the microstructure control of ' nano-precipitates and -plate precipitates by a set of heat treatment process including solution heat treatment and aging heat treatment. The alloy after aging heat treatment exhibited the tensile strength of 1,548 MPa with the elongation of 23 % and Charpy impact value of 29 J/cm2. The developed SLM products showed the corrosion resistance in H2SO4 and HCl comparable to those of the precipitation-hardened nickel alloys. The relationship between morphologies of precipitates and the alloys' mechanical properties and corrosion behaviors will be discussed.
• 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]
  
• Galvanic-submerged photosynthesis of crystallites: Fabrication of ZnO nanorods@ Cu-surface

  Yuki Takahashi, Kento Hiraiwa, Melbert Jeem, Lihua Zhang, Seiichi Watanabe

  Applied surface science 489 313 - 320 2019年06月 [査読有り][通常論文]
  
• Luminescence properties of ZnO-M heterostructures fabricated by galvanic-submerged photosynthesis of crystallites

  Kento Hiraiwa, Yuki Takahashi, Junichi Mizuno, Melbert Jeem, Seiichi Watanabe

  Applied Surface Science 489 269 - 277 2019年06月 [査読有り][通常論文]
  
• Fabrication of Iron Oxide Nanoparticles via Submerged Photosynthesis and the Morphologies under Different Light Sources

  Lihua Zhang, Melbert Jeem, Kazumasa Okamoto, Seiichi Watanabe

  ISIJ INTERNATIONAL 59 12 2352 - 2358 2019年 [査読有り][通常論文]
   

  Recently, metal oxide nanocrystallites have been synthesized through a new pathway, i.e., the submerged photosynthesis of crystallites (SPSC), and flower-like ZnO and CuO nanostructures have been successfully fabricated via this method. In this work, the SPSC process was applied for the fabrication of iron oxide and hydroxide nanoparticles. The experiments were conducted under visible light, ultraviolet light, and gamma-ray irradiation conditions and the morphologies of the obtained nanoparticles were observed and compared with that obtained without illumination. Then, the mechanism of the SPSC process for the fabrication of iron oxide nanoparticles was discussed. The results show that various kinds of morphologies of nanocrystallites were obtained on the Fe plate surface and the main morphologies are different under different conditions. For example, most FeOOH with the morphologies of nanorod and nanofiber exist by visible light irradiation; most faceted crystals of FeOOH and Fe2O3 with the morphologies of nanograular and nanorod exist by ultraviolet irradiation. In the SPSC process, light irradiation generates center dot OH at the crystal tips and promote the crystallization in apical growth of FeOOH.
• Mechanical and corrosion properties of CoCrFeNiTi-based high-entropy alloy additive manufactured using selective laser melting

  Tadashi Fujieda, Meichuan Chen, Hiroshi Shiratori, Kosuke Kuwabara, Kenta Yamanaka, Yuichiro Koizumi, Akihiko Chiba, Seiichi Watanabe

  Additive Manufacturing 25 25 412 - 420 2019年01月 [査読有り][通常論文]
   

  © 2018 Elsevier B.V. The effectiveness of applying selective laser melting (SLM) to a CoCrFeNiTi-based high-entropy alloy was compared with that of using electron beam melting (EBM). The higher solidification rate during SLM promoted a fine uniform microstructure with no visible segregation, which led to superior tensile properties (yield strength: 773.0 ± 4.2 MPa, ultimate tensile strength: 1178.0 MPa, elongation: 25.8 ± 0.6%) and a higher pitting potential (0.88 ± 0.03 V versus Ag/AgCl in a 3.5% NaCl solution at 353 K) in comparison to the EBM specimens (743.4 ± 11.6, 932.2 ± 4.8 MPa, 4.0 ± 0.2%, and 0.50 ± 0.04 V versus Ag/AgCl, respectively). The effect of a solution treatment on the tensile properties and pitting-corrosion resistance of the SLM specimens was then examined. The effect of the solution treatment on these properties depended on the cooling method used during the treatment. In particular, the tensile properties and pitting-corrosion resistance improved as a result of water quenching. On the other hand, the properties of the solution-treated specimens depended on the size and volume fraction of very fine-ordered particles, with diameters of tens of nanometers that contained Ni and Ti. The as-built and solution-treated SLM specimens exhibited excellent tensile strength and exceptional pitting-corrosion resistance; they had higher tensile strength and pitting-corrosion resistance than the conventional high-corrosion-resistant alloys.
• In-situ visualizing atomic structural evolution during crystallization in ternary Zr-Cu-Al bulk metallic glasses

  Xiaoya Wei, Si Lan, Zhenduo Wu, Masato Ohnuma, Tamaki Shibayama, Seiichi Watanabe, Jie Zhou, Zhaoping Lu, Yang Ren, X. -L.Wang

  Intermetallics 105 105 173 - 178 2019年01月 [査読有り][通常論文]
   

  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.
• Photochemistry and the role of light during the submerged photosynthesis of zinc oxide nanorods

  Lihua Zhang, Melbert Jeem, Kazumasa Okamoto, Seiichi Watanabe

  Scientific Reports 8 1 177  2018年12月01日 [査読有り][通常論文]
   

  Recently, metal oxide nanocrystallites have been synthesized through a new pathway, i.e., the submerged photosynthesis of crystallites (SPSC), and flower-like ZnO nanostructures have been successfully fabricated via this method. However, the photochemical reactions involved in the SPSC process and especially the role of light are still unclear. In the present work, we discuss the reaction mechanism for SPSC-fabricated ZnO nanostructures in detail and clarify the role of light in SPSC. The results show that both photoinduced reactions and hydrothermal reactions are involved in the SPSC process. The former produces OH radicals, which is the main source of OH - at the ZnO crystal tips, whereas the latter generates ZnO. Although ZnO nanocrystals can be obtained under both UV irradiation and dark conditions with the addition of thermal energy, light promotes ZnO growth and lowers the water pH to neutral, whereas thermal energy promotes ZnO corrosion and increases the water pH under dark conditions. The study concludes that the role of light in the submerged photosynthesis of crystallites process is to enhance ZnO apical growth at relatively lower temperature by preventing the pH of water from increasing, revealing the environmentally benign characteristics of the present process.
• Evolution of 3D nanoporosity and morphology in selectively dealloying ternary Au₅₅Cu₂₅Si₂₀ metallic glass ribbon with enhanced alcohol electro-oxidation performance.

  Xu Y, Cheng J, Yiu PM, Shan G, Shibayama T, Watanabe S, Ohnuma M, Shek CH

  Nanoscale 10 39 18846 - 18856 2018年10月 [査読有り][通常論文]
   

  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'.
• Atmospherically sintered copper-base alloy application film with self-assembled barrier layer on silicon substrate for silicon photovoltaics

  Shuichiro Adachi, Takeshi Nojiri, Takahiko Kato, Seiichi Watanabe, Masato Yoshida

  Journal of Alloys and Compounds 757 757 333 - 339 2018年08月15日 [査読有り][通常論文]
   

  In this paper, we show the first production of Cu-based electrode materials including self-assembled barrier layers which can prevent Cu-Si inter-diffusion during sintering and are expected to be applicable to crystalline Si photovoltaics. The characteristics of electrodes produced by mixed Cu-P/Sn pastes at various compositions were evaluated. Electrodes sintered in an atmospheric environment showed electrical resistivity of below 1 × 10−4 Ω・cm. In addition, the formation of compounds such as Cu3Si at the Si surface was prevented with a Sn particle ratio ranging between 20 and 60 wt%. The structural analysis revealed that the electrode included not only a Cu-Sn IMCs network but also a self-assembled Sn-P-O glass phase between the Cu-Sn IMCs network and the Si substrate, capable of forming a barrier layer to prevent Cu-Si inter-diffusion. These results may enable the widespread use of atmospherically sintered Cu-based electrode for the mass production of next-generation crystalline Si solar cells. Subsequently, the manner in which the Sn-P-O glasses were formed was discussed using a thermos-dynamical approach.
• Design of a patterned nanostructure array using a nanosecond pulsed laser

  Yutaka Yoshida, Ko Ohnishi, Yasutaka Matsuo, Seiichi Watanabe

  AIP Advances 8 4 045122  2018年04月01日 [査読有り][通常論文]
   

  For design the patterned nanostructure array (PNSA) on material surface using a nanosecond pulsed laser, we investigated the influence of phase shift between scattered lights on silicon (Si) substrate using 30-nm-wide gold lines (GLs) spacings. At a spacing of 5,871 nm, ten nanodot (ND) arrays were formed at intervals of 533 nm by nanosecond pulsed laser. The results show that the formation of the PNSA was affected by the resonance of scattered light. We conclude that ND arrays were formed with a spacing of Λ = nλ. And we have designed PNSA comprising two ND arrays on the substrate. The PNSA with dimensions of 1,600 nm × 1,600 nm was prepared using GLs.
• Formation of stainless steel nanoballs via submerged glow-discharge plasma and their microstructural analysis with evaluation of photocatalytic activity

  Rafiq Mirza BIN JULAIHI Muhammad, Peter Nai Yuh Yek, Shigeo Yatsu, Seiichi Watanabe

  ISIJ International 58 6 1162 - 1167 2018年 [査読有り][通常論文]
   

  Stainless steel has shown potential as a catalytic material in bulk form. However, it only becomes active in an aqueous acidic environment and elevated temperatures. This study aims to produce stainless steel nanoparticles that have high photocatalytic activity in a neutral medium and at room temperature and to elucidate the photocatalytic activity mechanism of the nanoparticles. Spherical, photocatalytic nanoparticles called “nanoballs” were synthesized by the submerged glow-discharge method. Stainless steel SUS316L grade wire was used as the cathode, platinum mesh was used as the anode while the electrolyte was potassium carbonate. The nanoballs were obtained after centrifuging and washing with water. The physical characteristics of the photocatalytic nanoballs were analysed by scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction. The nanoballs were mixed with methylene blue and irradiated with ultraviolet light for the evaluation of photocatalytic reaction. The photodecomposition samples were determined using UV-vis spectrometry. The by-products of the photodecomposition were evaluated using mass spectrometry. The results show that stainless steel nanoballs have photocatalytic activity when irridiated with ultraviolet light at room temperature. Submerged glow-discharge plasma method can synthesize nanoparticles rapidly using only metal wires as the electrode.
• 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 2018年 [査読有り][通常論文]
   

  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.
• Transformation in iron–platinum thin film via nanosecond pulsed laser irradiation

  Yutaka Yoshida, Shigeo Yatsu, Seiichi Watanabe, Akira Yamauchi, Jun-ichi Shibano

  Journal of Physics and Chemistry of Solids 109 46 - 49 2017年10月 [査読有り][通常論文]
   

  The composite consists of disordered and ordered iron platinum (FePt) alloys was induced by nanosecond pulsed laser (NPL) irradiation. The process was investigated by laser high-voltage electron microscopy (laser-HVEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) analyses. The structural transformation upon NPL irradiation was monitored by laser-HVEM imaging, with the structure being modified in a short second after the one pulse. XRD analyses revealed expanded and contracted lattice distances before and after NPL irradiation, respectively. According to the XRD and TEM results, the surface of FePt alloys was transformed from fct to fcc structure with structural strain by NPL irradiation.
• 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 2017年08月 [査読有り][招待有り]
   

  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 2017年07月 [査読有り][通常論文]
   

  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.
• 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 2017年05月 [査読有り][通常論文]
   

  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.
• Formation of CuO nano-flowered surfaces via submerged photo-synthesis of crystallites and their antimicrobial activity

  Fumika Nishino, Melbert Jeem, Lihua Zhang, Kazumasa Okamoto, Satoshi Okabe, Seiichi Watanabe

  SCIENTIFIC REPORTS 7 1 1063  2017年04月 [査読有り][通常論文]
   

  We report the fabrication of flower-like CuO nanostructured surfaces via submerged photo-synthesis of crystallites (SPSC), which requires only UV illumination in neutral water. In this paper, we discuss the reaction mechanism of the photochemical formation of the SPSC-fabricated CuO nanostructures in detail based on surface microstructural analyses and a radiation-chemical consideration with additional gamma-ray irradiation. Since the SPSC method for surface nanostructural fabrication can work at low temperatures at atmospheric pressure without using harmful substances, it is a potential fabrication method for green nanotechnology applications. In this vein, the antibacterial activity of the nano-flowered CuO surfaces was tested against Gram-positive (Staphylococcus aureus) bacteria and Gram-negative (Escherichia coli K12) bacteria, and the results demonstrate that the nano-flowered CuO nanostructures act as an effective antimicrobial agent.
• 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  2017年03月 [査読有り][通常論文]
   

  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).
• 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  2017年03月 [査読有り][通常論文]
   

  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.
• 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 2017年03月 [査読有り][通常論文]
   

  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.
• CoCrFeNiTi-based high-entropy alloy with superior tensile strength and corrosion resistance achieved by a combination of additive manufacturing using selective electron beam melting and solution treatment

  Tadashi Fujieda, Hiroshi Shiratori, Kosuke Kuwabara, Mamoru Hirota, Takahiko Kato, Kenta Yamanaka, Yuichiro Koizumi, Akihiko Chiba, Seiichi Watanabe

  MATERIALS LETTERS 189 148 - 151 2017年02月 [査読有り][通常論文]
   

  We succeeded in fabricating a Co1.5CrFeNi1.5Ti0.5Mo0.1 high entropy alloy with superior tensile strength and corrosion resistance by a combination of additive manufacturing using selective electron beam melting (SEBM) and solution treatment (ST). The SEEM specimens exhibited superior tensile properties to those of the corresponding casting specimen. Furthermore, the tensile properties and corrosion properties of the SEEM specimens markedly improved by ST. These notable improvements are ascribed to homogeneous precipitation of very fine particulate ordering-phase particles whose diameters are several tens of nanometers with Ni and Ti concentrations. The solution-treated SEBM specimens also exhibited both high strength and high pitting potential, which in combination are superior to the conventional alloys used in severe corrosion environments.
• A reaction mechanism of atmospheric sintering for Copper–Phosphorus alloy electrode

  Shuichiro Adachi, Yutaka Yoshida, Takeshi Nojiri, Takahiko Kato, Seiichi Watanabe, Masato Yoshida

  Journal of Alloys and Compounds 695 3353 - 3359 2017年02月 [査読有り][通常論文]
   

  In this study, we propose a reaction mechanism for atmospherically sintered copper-phosphorus (CueP) alloy electrodes which are expected to replace silver (Ag) electrodes. Structural analysis using transmission electron microscopy (TEM) has revealed that not only copper phosphide (Cu3P) but also copper phosphates of Cu2P2O7, Cu-3(PO4)(2) and Cu2PO4 distributed mainly at the P-concentrated region of the metallic part, where Cu3P distributed before sintering. In addition, the ordered superstructures which have a period based on the specific lattice spacing of Cu3P {002} were newly discovered. From structural analysis, we estimated the mechanisms comprised of the decomposition of Cu3P accompanied by a lack of Cu and P, then formation of metastable phases involving structural vacancies, and eventual transition to the copper phosphates. We also discussed another manner of forming the copper phosphates by the thermo-dynamical approach. Our results may provide a way to reduce the electrical resistivity of Cu-P alloy electrodes by controlling the structures including the deoxidized Cu. (C) 2016 Elsevier B.V. All rights reserved.
• In-situ observation of self-assembly of quasi-two-dimensional Au nano-submicron particles on beta-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 164 164 202 - 205 2016年02月 [査読有り][通常論文]
   

  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.
• 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 2016年 [査読有り][通常論文]
   

  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.
• 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][通常論文]
  
• Effect of Glass Frits Amount on Atmospheric Sintering Behavior and Characteristics of Electrode Produced by Copper–Phosphorus Alloy

  Shuichiro Adachi, Yutaka Yoshida, Takeshi Nojiri, Yasushi Kurata, Takahiko Kato, Seiichi Watanabe, Masato Yoshida

  IEEE Journal of Photovoltaics 5 5 1325 - 1334 2015年09月 [査読無し][通常論文]
   

  In this study, we evaluate the atmospheric sintering behavior and characteristics of electrodes produced by copper-phosphorus (Cu-P) alloy paste containing various amounts of B2O3-Bi2O3-SiO2 glass frits. We demonstrate the need for a certain extent of glass frits to expand the applicable temperature for use of Cu-P alloy paste shifted to the higher temperature side, where commercial pastes for crystalline silicon (Si) photovoltaics are sintered, although the minimum electrical resistivity of the Cu-P alloy electrode increased by increasing the amount of glass frits. Based on the characteristics of the Cu-P alloy electrode, the need to expand the Cu crystal network and prevent the oxidization of generated Cu has emerged to reduce electrical resistivity. A crystalline BiPO4 was formed in the sintered Cu-P alloy electrode, which suggests a reaction between partially crystallized glass frits and P2O5 generated from Cu-P-O glass derived from the Cu-P alloy that has occurred. Subsequently, the sintering behavior of Cu-P alloy paste, including the glass frits, was discussed based on the results of X-ray diffraction, transmission electron microscopy, scanning transmission electron microscopy energy-dispersive X-ray spectroscopy, and electron energy loss spectroscopy.
• Synthesis of stainless steel nanoballs via submerged glow-discharge plasma and its photocatalytic performance in methylene blue decomposition

  Muhammad Rafiq Mirza bin Julaihi, Shigeo Yatsu, Melbert Jeem, Seiichi Watanabe

  JOURNAL OF EXPERIMENTAL NANOSCIENCE 10 12 965 - 982 2015年08月 [査読有り][通常論文]
   

  Stainless steel nanoparticles or 'nanoballs' have been synthesised using submerged glow-discharge plasma. Transmission electron microscopy showed that the nanoballs are uniformly spherical and size distribution estimation showed that their diameters are below 200nm. The decomposition of methylene blue solution under ultraviolet light with the wavelength of 354nm was observed in the presence of stainless steel nanoballs. A mixture of stainless steel nanoballs and 0.1% methylene blue dye was irradiated with ultraviolet light. The concentration of methylene blue was reduced to baseline level in 72hours. This shows that the stainless steel nanoballs have photocatalytic ability. In stainless steel nanoballs, methylene blue showed two different decomposition pathways; showing fast and slow reactions. Also, methylene blue was oxidised into sulphoxide before reducing into lighter by-products. X-ray diffraction analysis has shown that the nanoballs consist of Fe2O3 and Cr2O3, which are photocatalytically active species.
• Synthesis of stainless steel nanoballs via submerged glow-discharge plasma and its photocatalytic performance in methylene blue decomposition

  Muhammad Rafiq Mirza bin Julaihi, Shigeo Yatsu, Melbert Jeem, Seiichi Watanabe

  JOURNAL OF EXPERIMENTAL NANOSCIENCE 10 12 965 - 982 2015年08月 [査読有り][通常論文]
   

  Stainless steel nanoparticles or 'nanoballs' have been synthesised using submerged glow-discharge plasma. Transmission electron microscopy showed that the nanoballs are uniformly spherical and size distribution estimation showed that their diameters are below 200nm. The decomposition of methylene blue solution under ultraviolet light with the wavelength of 354nm was observed in the presence of stainless steel nanoballs. A mixture of stainless steel nanoballs and 0.1% methylene blue dye was irradiated with ultraviolet light. The concentration of methylene blue was reduced to baseline level in 72hours. This shows that the stainless steel nanoballs have photocatalytic ability. In stainless steel nanoballs, methylene blue showed two different decomposition pathways; showing fast and slow reactions. Also, methylene blue was oxidised into sulphoxide before reducing into lighter by-products. X-ray diffraction analysis has shown that the nanoballs consist of Fe2O3 and Cr2O3, which are photocatalytically active species.
• 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  2015年06月 [査読有り][通常論文]
   

  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  2015年02月 [査読有り][通常論文]
   

  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).
• Wavelength-dependent magnetic transitions of self-organized iron-aluminum stripes induced by pulsed laser irradiation

  Yutaka Yoshida, Seiichi Watanabe, Hideo Kaiju, Junji Nishii, Kyosuke Yoshimi

  JOURNAL OF APPLIED PHYSICS 117 4 045305-045305-5  2015年01月 [査読無し][通常論文]
   

  We investigate the laser wavelength dependence of structural and magnetic transitions on the surface of an iron-aluminum (FeAl) alloy induced by nanosecond pulsed laser irradiation. The formation of self-organized FeAl stripes with a wavelength-dependent period is observed in a local area on the (111)-oriented plane. Focused magneto-optical Kerr effect measurements reveal that the coercivity reaches up to 1.2 kOe with increasing the magnetic field rotation angle, which is estimated from the stripe direction, in FeAl stripes irradiated at 355 nm, and its magnetization reversal can be explained by the domain-wall motion model. On the other hand, the magnetization reversal agrees with the Stoner-Wohlfarth model in FeAl stripes irradiated at 1064 nm. This magnetic transition originates from the B2-to-A2 phase transition in stripe structures and bulk regions. These results indicate that the magnetic transition from the incoherent to coherent mode as well as the structural transformation of stripe patterns can be controlled by the incident laser wavelength. (C) 2015 AIP Publishing LLC.
• 電子顕微鏡による材料研究 13 異種原子注入

  柴山環樹, 渡辺精一

  軽金属 64 12 654 - 662 軽金属学会 2014年12月30日 [査読無し][通常論文]
  
• Magnetic Properties on FeAl Stripes and Dots Induced by Nanosecond Pulsed Laser Irradiation

  H. Kaiju, Y. Yoshida, S. Watanabe, K. Kondo, A. Ishibashi, K. Yoshimi

  Journal of The Magnetics Society of Japan 38 4 157 - 161 The Magnetics Society of Japan 2014年08月 [査読有り][通常論文]
   

  We investigate magnetic properties of FeAl stripes and dots formed on the surface of Fe₅₂Al₄₈ induced by nanosecond pulsed laser irradiation. According to the in-plane magneto-optical Kerr effect (MOKE) measurements, the magnetization reversal in FeAl stripes can be explained by the domain-wall (DW) motion model, indicating that the magnetization rotates incoherently. In contrast, the in-plane and polar MOKE measurements reveal that the magnetic easy axis of the FeAl dots exists along the out-of-plane direction and the coercive force H_c shows as large as 1 kOe. These results indicate that the nanosecond pulsed laser irradiation can be expected to serve as a useful tool for obtaining magnetic nanostructures and creating high-H_c materials.
• Nanosecond pulsed laser induced self-organized nano-dots patterns on GaSb surface

  Yutaka Yoshida, Kazuya Oosawa, Jyunya Wajima, Seiichi Watanabe, Yasutaka Matsuo, Takahiko Kato

  APPLIED SURFACE SCIENCE 307 24 - 27 2014年07月 [査読無し][通常論文]
   

  We report a technique for formation of two-dimensional (2D) nanodot (ND) patterns on gaillium antimoide (GaSb) using a nanosecond pulsed laser irradiation with 532 nm wavelength. The patterns have formed because of the interference and the self-organization under energy deposition of the laser irradiation, which induced the growth of NDs on the local area. The NDs are grown and shrunken in the pattern by energy depositions. In the laser irradiation with average laser energy density of 35 mJ cm(-2), large and small NDs are formed on GaSb surface. The large NDs have grown average diameter from 160 to 200 nm with increase of laser pulses, and the small NDs have shrunken average diameter from 75 to 30 nm. The critical dot size is required about 107 nm for growth of the NDs in the patterns. Nanosecond pulsed laser irradiation can control the self-organized ND size on GaSb in air as a function of the laser pulses. (c) 2014 Elsevier B.V. All rights reserved.
• Magnetic properties on the surface of FeAl stripes induced by nanosecond pulsed laser irradiation

  H. Kaiju, Y. Yoshida, S. Watanabe, K. Kondo, A. Ishibashi, K. Yoshimi

  JOURNAL OF APPLIED PHYSICS 115 17 17B901  2014年05月 [査読有り][通常論文]
   

  We demonstrate the formation of magnetic nanostripes on the surface of Fe52Al48 induced by nanosecond pulsed laser irradiation and investigate their magnetic properties. The magnetic stripe consists of a disordered A2 phase of Fe-Al alloys with Al-oxide along the [110] direction on the (111)-oriented plane. According to the focused magneto-optical Kerr effect measurement, the coercive force of the magnetic stripe obeys the 1/cos theta law, where theta is the field rotation angle estimated from the stripe direction. Also, the jump field can be observed in the magnetic hysteresis loop. These results indicate that the magnetization reversal in the magnetic stripe originates from the domain pinning, showing that the magnetization rotates incoherently. (C) 2014 AIP Publishing LLC.
• 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 143104-143104-8  2014年04月 [査読無し][通常論文]
   

  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 2014年01月 [査読無し][通常論文]
   

  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.
• 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 

  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。
• 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 2013年11月 [査読無し][通常論文]
   

  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 2013年10月 [査読有り][通常論文]
   

  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

  Xuan Meng, Tamaki Shibayama, Ruixuan Yu, Shinya Takayanagi, Seiichi Watanabe

  JOURNAL OF APPLIED PHYSICS 114 5 054308-054308-9  2013年08月 [査読無し][通常論文]
   

  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.
• Nanopatterns induced by pulsed laser irradiation on the surface of an Fe-Al alloy and their magnetic properties

  Yutaka Yoshida, Kazuya Oosawa, Seiichi Watanabe, Hideo Kaiju, Kenji Kondo, Akira Ishibashi, Kyosuke Yoshimi

  APPLIED PHYSICS LETTERS 102 18 183109-1 - 183109 -4 2013年05月 [査読有り][通常論文]
   

  We have studied nanopatterns induced by nanosecond pulsed laser irradiation on (111) plane surfaces of a polycrystalline iron-aluminum alloy and evaluated their magnetic properties. Multiple nanosecond pulsed laser irradiation induces a wavelength-dependent surface transformation of the lattice structure from a B2-type to a supersaturated body centered cubic lattice. The selective formation of surface nanopatterns consisting of holes, stripes, polygonal networks, and dot-like nanoprotrusions can be observed. Furthermore, focused magneto-optical Kerr effect measurements reveal that the magnetic properties of the resultant nanostructured region changes from a paramagnetic to a ferromagnetic phase in accordance with the number of laser pulses. (C) 2013 AIP Publishing LLC.
• Dislocation loop formation under various irradiations of laser and/or electron beams

  Zhanbing Yang, Seiichi Watanabe

  ACTA MATERIALIA 61 8 2966 - 2972 2013年05月 [査読有り][通常論文]
   

  A high-voltage electron microscope (HVEM) equipped with a laser head (laser-HVEM) was developed at Hokkaido University and is used to investigate the surface modification of semiconductors and the behaviour of lattice point defects in metals under various irradiations of laser (photon) and/or electron beams. In the present study, the annealing effect of pulsed laser irradiation on a face-centred-cubic metal was experimentally investigated and theoretically calculated. The systematic assessment of dislocation loop evolution under laser-electron sequential irradiation and laser-electron dual-beam irradiation was performed. Our results show that the rapid heating and quenching that occurred during pulsed laser irradiation caused vacancies to be introduced at the surface of the specimen and to diffuse to the interior, which led to the formation and growth of vacancy-type (V-type) dislocation loops. These loops gradually shrank and finally disappeared during the subsequent electron irradiation of the sample. During laser-electron simultaneous dual-beam irradiation, the type of loop formed, interstitial-type (I-type) or V-type loops, is determined by the relative intensities of the laser beam and electron beam, which indicates that the loop type can be controlled by changing the relative intensities of the beams. Accordingly, models of dislocation loop formation during various irradiations were proposed. The newly developed laser-HVEM instrument is expected to be employed in the exploration of mechanisms in material science, as well as in other scientific fields. (c) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
• Radiation-induced segregation and corrosion behavior on Σ3 coincidence site lattice and random grain boundaries in proton-irradiated type-316L austenitic stainless steel

  N. Sakaguchi, M. Endo, S. Watanabe, H. Kinoshita, S.Yamashita, H.Kokawa

  J. Nuclear Materials 434 1-3 65 - 71 2013年03月 [査読有り][通常論文]
   

  The behavior of radiation-induced segregation (RIS) and intergranular corrosion at random grain boundaries and Sigma 3 coincidence site lattice (CSL) boundaries in proton-irradiated 316L stainless steel was examined. The frequency of the CSL boundaries was enhanced up to 86.6% by grain boundary engineering treatment prior to irradiation. Significant nickel enrichment and chromium depletion were induced at the random grain boundary owing to the RIS. At faceted Sigma 3 CSL boundaries, chromium depletion occurred at the asymmetrical boundary facet plane whereas no RIS was observed at the coherent twin boundary. After the electrochemical etching test, an intergranular corrosion groove was found along the random grain boundaries because of the low chromium concentration (similar to 12%) at the boundaries. At the faceted Sigma 3 CSL boundaries, the discontinuous groove along the asymmetric facet plane was completely disrupted by the non-corrosive coherent twin boundary. (C) 2012 Elsevier B.V. All rights reserved.
• The Irradiation Effect of a Simultaneous Laser and Electron Dual-beam on Void Formation

  Zhanbing Yang, Seiichi Watanabe, Takahiko Kato

  SCIENTIFIC REPORTS 3 01201  2013年02月 [査読有り][通常論文]
   

  Randomly distributed lattice point defects such as supersaturated vacancies (SVs) and Frenkel-pairs (FPs, an interstitial and a vacancy) can be simultaneously introduced into the crystal by energetic beam irradiation in outer space and/or nuclear reactors, but their behavior has not been fully understood. Using a high-voltage electron microscope equipped with a laser (laser-HVEM), we show the striking effects of simultaneous laser-electron (photon-electron) dual-beam irradiation on void formation. Our results reveal that during laser-electron sequential irradiation, pre-laser irradiation enhanced void nucleation and subsequent electron irradiation enhanced void growth. However, the laser-electron dual-beam irradiation was analyzed to depress void swelling remarkably because the recombination of SVs and interstitials was enhanced. The results provide insight into the mechanism underlying the dual-beam radiation-induced depression of void swelling in solids.
• 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 2013年01月 [査読有り][通常論文]
   

  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 3,  9 CSL and Random Grain Boundaries in Helium Implanted 316L Austenitic Stainless Steel

  N. Sakaguchi, Y. Ohguchi, T. Shibayama, S. Watanabe, H. Kinoshita

  J. Nuclear Materials 432 1-3 23 - 27 2013年01月 [査読有り][通常論文]
   

  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.
• Effect of hydrogen on irradiation stability of dispersed oxide particles (Y2O3) in 12Cr-ODS steel

  Guo, L.-N., Hu, B.-F., Jia, C.-C., Takahashi, H., Kinoshita, H., Watanabe, S.

  Hedongli Gongcheng/Nuclear Power Engineering 34 3 2013年
• FABRICATION OF NANOPARTICLES BY ELECTRIC DISCHARGE PLASMA IN LIQUID

  S. Yatsu, H. Takahashi, H. Sasaki, N. Sakaguchi, K. Ohkubo, T. Muramoto, S. Watanabe

  ARCHIVES OF METALLURGY AND MATERIALS 58 2 425 - 429 2013年 [査読有り][通常論文]
   

  The electric plasma discharge method involves the application of a voltage between a cathode and anode in a conductive electrolytic solution to create a discharge plasma at the cathode. When certain material is used as the cathode, small droplets are emitted with the plasma discharge, and the melted droplets are rapidly cooled in the solution to form nanoscale particles of the material. In this work, nanoparticles of Al, Au, Si, and various alloys of between 100 nm and less than 10 nm in size were produced and characterized. Characterization of Si nanoparticles is especially important because their use in lithium batteries greatly influences battery performance. It was found by high resolution electron microscopy and microstructural surface analysis that oxidation layers of a few nm in thickness were formed on the surface of the Si nanoparticles.
• Corrosion–erosion test of SS316L grain boundary engineering material (GBEM) in lead bismuth flowing loop

  Shigeru Saito, Kenji Kikuchi, Dai Hamaguchi, Masao Tezuka, Masanori Miyagi, Hiroyuki Kokawa, Seiichi Watanabe

  J. Nuclear Materials 431 1-3 91 - 96 2012年12月 [査読有り][通常論文]
   

  To evaluate the lifetime of structural materials utilized in a spallation neutron source, corrosion tests in lead-bismuth eutectic (LBE) have been done at JAEA. Austenitic steels are preferable as the structural material for ADS. However, previous studies have revealed that austenitic steel SS316 shows severe corrosion-erosion in LBE because of LBE penetration through grain boundaries and separation of grains. So it was considered that GBE (grain-boundary engineered) materials may be effective to improve the corrosion resistance of austenitic steels in LBE. In this study, the results of corrosion tests on austenitic steel SS316L-BM (base metal) and SS316L-GBEM (grain-boundary-engineered material) under flowing LBE conditions will be reported. The corrosion test was performed using the JAEA lead-bismuth material corrosion loop (JLBL-1). The experimental conditions were as follows: The high and low temperature parts of the loop were 450 degrees C and 350 degrees C, respectively. The flow velocity at the test specimens was about 0.7 m/s. The oxygen concentration in LBE was not controlled and was estimated to have been very low. After the 3600 h of operation, macroscopic, SEM, and SIM observations and EDX analysis were carried out. The results showed that the corrosion depth and LBE penetration through the grain boundaries of the 316SS-GBEM were smaller than those of the 316S5-BM. (C) 2011 Elsevier B.V. All rights reserved.
• Development of advanced materials for spallation neutron sources and radiation damage simulation based on multi-scale models

  Masayoshi Kawai, Hiroaki Kurishita, Hiroyuki Kokawa, Seiichi Watanabe, Norihito Sakaguchi, Kenji Kikuchi, Shigeru Saito, Toshimasa Yoshiie, Hiroshi Iwase, Takahiro Ito, Satoshi Hashimoto, Yoshihisa Kaneko, Masatoshi Futakawa, Shiori Ishino

  JOURNAL OF NUCLEAR MATERIALS 431 1-3 16 - 25 2012年12月 [査読無し][通常論文]
   

  This report describes the status review of the JSPS Grant Team to develop advanced materials for the spallation neutron sources and modeling of radiation damage. One of the advanced materials is a toughness enhanced, fine-grained tungsten material (W-TiC) having four-times larger fracture toughness than ordinary tungsten and appreciable RT ductility in the recrystallized state. The other is an intergranular crack (IGC)-resistant austenitic stainless steel which was processed by the grain-boundary engineering (GBE). The experimental results are devoted to corrosion in a lead-bismuth eutectic, arrest of corrosion of weld-decay, radiation damage and creep rupture as well as new technique of GEE using a laser and annealing procedure. New technique seems to be applicable to large or complicated-shaped components. A series of the multi-scale models is built up from nuclear reaction between incident particles and medium nuclei to material property change due to radiation damage. Sample calculation is made on 3 mm-thick nickel bombarded by 3 GeV protons. (C) 2011 Elsevier B.V. All rights reserved.
• Dislocation Loop Formation and Growth under In Situ Laser and/or Electron Irradiation

  Zhanbing Yang, Norihito Sakaguchi, Seiichi Watanabe, Masayoshi Kawai

  SCIENTIFIC REPORTS 1 190 DOI:10.1038/srep00190  2011年12月 [査読無し][通常論文]
   

  Vacancies and interstitial atoms are primary lattice (point) defects that cause observable microstructural changes, such as the formation of dislocation loops and voids in crystalline solids. These defects' diffusion properties determine the phase stability and environmental resistibility of macroscopic materials under ambient conditions. Although in situ methods have been proposed for measuring the diffusion energy of point defects, direct measurement has been limited. In this study, we propose an alternative in situ method to measure the activation energy for vacancy migration under laser irradiation using a pulsed laser beam from a laser-equipped high-voltage electron microscope (laser-HVEM). We made in situ observations that revealed the formation and growth of vacancy dislocation loops in an austenitic stainless steel during laser irradiation. These loops continued to grow when thermal annealing was performed after laser irradiation at the same temperature. We anticipate that laser-HVEM will provide a new method for investigating lattice defects.
• Micro-chemical analysis of diffusion bonded W–SiC joint”， J. Nuclear Materials

  Genichiro Matsuoa, Tamaki Shibayamab, Hirotatsu Kishimotoc, Kouichi Hamadab, Seiichi Watanabe

  J. Nuclear Materials 417 1-3 391 - 394 2011年10月 [査読無し][通常論文]
   

  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.
• Fabrication of a Au/Si nanocomposite structure by nanosecond pulsed laser irradiation

  Yutaka Yoshida, Seiichi Watanabe, Yoshiaki Nishijima, Kosei Ueno, Hiroaki Misawa, Takahiko Kato

  NANOTECHNOLOGY 22 37 375607-1-375607-7  2011年09月 [査読無し][通常論文]
   

  A gold/silicon nanocomposite structure (NCS) was formed on a Si(100) surface by nanosecond pulsed laser irradiation. The Au/Si NCS contained both Au nanoparticles (NPs) and Au-Si alloy layers. We report that the use of laser irradiation to form Au NPs comprises two competing processes: a top-down effect involving decomposition into smaller NPs and a bottom-up effect involving self-assembly or self-organization into larger NPs. The formation of the periodic structure involved self-organization, i.e., the bottom-up effect, and was observed in situ using a pulsed-laser-equipped high-voltage electron microscope. The NCS formed by laser irradiation can be controlled by adjusting the laser energy density and the number of laser pulses.
• Grain boundary engineering of austenitic steel PNC316 for use in nuclear reactors

  M. Sekine, N. Sakaguchi, M. Endo, H. Kinoshita, S. Watanabe, H. Kokawa, S. Yamashita, Y. Yano, M. Kawai

  JOURNAL OF NUCLEAR MATERIALS 414 2 232 - 236 2011年07月 [査読無し][通常論文]
   

  Austenitic stainless steel PNC316 was subjected to grain boundary engineering (GBE). It was found that the grain boundary engineered PNC316 (PNC316-GBEM) had a coincidence site lattice (CSL) fraction of 86% and that the network of random grain boundaries was perfectly divided by the CSL boundaries. The thermal stability and the void swelling behavior of PNC316-GBEM were investigated by means of SEM and TEM analyses. After thermal aging at 973 K for 100 h, structural changes were observed neither in the grain boundary networks of PNC316-GBEM nor in another sample of PNC316-GBEM subjected to 20% additional cold rolling, PNC316-GBEM20%CW. PNC316-GBEM showed a higher void swelling rate than as-received PNC316 (PNC316-AS). However, with additional 20% cold rolling after GBE, the void swelling rate decreased to as low as that of PNC316-AS. (C) 2011 Elsevier B.V. All rights reserved.
• Formation of sphalerite and wurtzite ZnO in Pd–Zn alloy after internal oxidation at elevated temperatures

  WATANABE Kei, SAKAGUCHI Norihito, WATANABE Seiichi

  Journal of Materials Science 46 13 4568 - 4573 2011年07月 [査読無し][通常論文]
   

  The crystalline structures of zinc oxide (ZnO) formed by the internal oxidation of a Pd-Zn alloy were examined at elevated temperatures. Metastable sphalerite ZnO with a tetrahedral shape preferentially nucleated in the Pd matrix, while plate-like precipitates consisting of a wurtzite ZnO phase preferentially grew at a high temperature. Unique ZnO precipitates with trapezoidal cross-section and consisting of inter-layered sequences with sphalerite ZnO and wurtzite ZnO were also examined at an intermediate temperature. It is inferred that the formation of stacking faults in the sphalerite ZnO is strongly related to the nucleation of the wurtzite-type ZnO sequence.
• Self-Organized Two-Dimensional Vidro-Nanodot Array on Laser-Irradiated Si Surface

  Yutaka Yoshida, Norihito Sakaguchi, Seiichi Watanabe, Takahiko Kato

  APPLIED PHYSICS EXPRESS 4 5 055202-1-055202-3  2011年05月 [査読無し][通常論文]
   

  We report a periodic two-dimensional (2D) array of uniquely shaped dotlike nanoprotrusions (NPs), which simultaneously self-organize on a Si surface under pulsed laser irradiation. The shape of the dotlike NPs can be controlled by adjusting the number of laser pulses. The flask-shaped dotlike NP array is named a vidro-nanodot (VND) array. We present a detailed analysis of the internal structure of VND using high-resolution electron microscopy. (C) 2011 The Japan Society of Applied Physics
• EELS and Ab-Initio Study of Faceted CSL Boundary in Silicon

  Norihito Sakaguchi, Makito Miyake, Seiichi Watanabe, Heishichiro Takahashi

  MATERIALS TRANSACTIONS 52 3 276 - 279 2011年03月 [査読無し][通常論文]
   

  Faceted Sigma 3 CSL grain boundaries in silicon were investigated by high-resolution transmission electron microscopy (HRTEM), electron energy-loss spectroscopy (EELS) and ab-initio calculation. A {112} Sigma 3 CSL boundary consisted of two segments which differed in atomic structure. The segment near the connected corner to {111} Sigma 3 CSL boundary showed symmetric structure and the other long segment, being distant region from the corner, showed asymmetric structure. In the symmetric segment a 5-fold coordinated atom presented, which produced a deep state in the band gap. A pronounced shoulder, which could be attributed to the defect state above Fermi level, was detected only in Si-L-23 energy-loss near-edge spectra (ELNES) acquired from the symmetric segment of the {112} Sigma 3 CSL boundary near the CSL junction. [doi:10.2320/matertrans.MB201018]
• In situ transmission electron microscopy observation of the decomposition of MgH2 nanofiber

  Chunyu Zhu, Norihito Sakaguchi, Sou Hosokai, Seiichi Watanabe, Tomohiro Akiyama

  INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 36 5 3600 - 3605 2011年03月 [査読無し][通常論文]
   

  In this paper, we presented an investigation of the phase transformation of MgH2 to Mg, in which a sample of a single-crystal MgH2 nanofiber was prepared by hydriding chemical vapor deposition (HCVD) and observed by in situ (high-resolution) transmission electron microscopy (TEM). The results indicated that the orientation relationship between MgH2 and Mg during the phase change was: one of the zone axis of MgH2 < 110 > parallel to Mg [0001] zone axis, or one of the plane {110} of MgH2 parallel to the basal plane of Mg (0001). On the basis of the obtained results, we proposed a structural model for the phase change of MgH2 to Mg. Copyright (C) 2010, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
• レーザー敷設型超高圧電子顕微鏡の開発とその可能性

  渡辺精一, 谷津茂男, 大久保賢二

  顕微鏡 46 151 - 155 2011年 [査読無し][通常論文]
  
• Irradiation damage behavior of oxide dispersion strengthened phase in 12Cr-ODS ferritic steel

  Hu, B.-F., Guo, L.-N., Yang, Z.-B., Takahashi, H., Kinoshita, H., Watanabe, S.

  Yuanzineng Kexue Jishu/Atomic Energy Science and Technology 45 3 2011年
• Effect of he on 12Cr-ODS ferritic steel structural damage during (He⁺+e^-) dual-beam irradiation

  Hu, B.-F., Guo, L.-N., Jia, C.-C., Yang, Z.-B., Rinoshita, H., Takahashi, H., Watanabe, S.

  Hedongli Gongcheng/Nuclear Power Engineering 32 3 2011年
• 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 2011年 [査読有り][通常論文]
   

  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.
• In situ observation of self-organizing nanodot formation under nanosecond-pulsed laser irradiation on Si surface

  S. Watanabe, Y. Yoshida, S. Kayashima, S. Yatsu, M. Kawai, T. Kato

  JOURNAL OF APPLIED PHYSICS 108 10 103510-1-103510-5  2010年11月 [査読有り][通常論文]
   

  An in situ observation of the formation of a laser-irradiation-induced nanodot array on a Si surface was performed using a pulsed-laser-equipped high-voltage electron microscope (laser-HVEM). Under multiple nanosecond (ns) pulsed laser irradiation shots, atomic clusters were first formed and distributed on the surface in order to grow them epitaxially into protruded dots with diameters of ten nanometers or less. This is followed by their diffusion induced by successive laser shots to cannibalize and merge them into a ripple line with aligned, larger dots. We conclude that the present subwavelength two-dimensionally-ordered nanodot array is formed by self-organization under pulsed laser irradiation. (C) 2010 American Institute of Physics. [doi:10.1063/1.3512888]
• Size-Controlled Ni Nanoparticles Formation by Solution Glow Discharge

  Genki Saito, Sou Hosokai, Tomohiro Akiyama, Souki Yoshida, Shigeo Yatsu, Seiichi Watanabe

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 79 8 083501-1-083501-3  2010年08月 [査読有り][通常論文]
   

  We report the size control of Ni nanoparticles generated via solution glow discharge and focus on the effect of electrolyte concentration on Ni nanoparticles. In our experiments, voltage was applied to generate a plasma in NaOH electrolytes with concentrations ranging from 1.0 to 0.001 kmol m(-3). The applied voltage strongly depended on the electrolyte concentration, and interestingly, product size decreased with electrolyte concentration; for example, (mean diameter, applied voltage, electrolyte concentration) = (148 nm, 90 V, 0.5 kmol m(-3)), and (70 nm, 590 V, 0.001 kmol m(-3)). These results suggested the possibility of using plasma electrolysis for synthesizing size-controlled nanoparticles by changing only electrolyte concentration.
• 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 2010年03月 [査読無し][通常論文]
   

  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.
• Self-Organized Dots Formation on Si Substrate by Nd: YAG Laser Irradiation

  Y. Yoshida, S. Yatsu, S. Watanabe, M. Kawai, T. Kato

  Proceedings of ICEP (International Conference on Electronics Packaging), Sapporo, May 12, 2010 (JIEP, Tokyo, Japan) 800 - 803 2010年 [査読有り][通常論文]
  
• Effect of hydrogen/electron dual-beam irradiation on stability of dispersed oxide particles of 12Cr-ODS steel

  Hu, B.-F., Guo, L.-N., Jia, C.-C., Yang, Z.-B., Kinoshita, H., Takahashi, H., Watanabe, S.

  Hedongli Gongcheng/Nuclear Power Engineering 30 6 2009年
• Effect of hydrogen/electron dual-beam irradiation on microstructure damage of 12Cr-ODS ferrite steel

  Hu, B.-F., Guo, L.-N., Jia, C.-C., Yang, Z.-B., Kinoshita, H., Takahashi, H., Watanabe, S.

  Yuanzineng Kexue Jishu/Atomic Energy Science and Technology 43 12 2009年
• A HRTEM and EELS study of Pd/ZnO polar interfaces

  N. Sakaguchi, Y. Suzuki, K. Watanabe, S. Iwama, S. Watanabe, H. Ichinose

  PHILOSOPHICAL MAGAZINE 88 10 1493 - 1509 2008年04月 [査読有り][通常論文]
   

  Atomic and electronic structures of interfaces in an internally oxidized Pd/ZnO system were Studied by high-resolution transmission electron microscopy (HRTEM) and electron energy-loss spectroscopy (EELS). {0001}(ZnO) polar planes tend to be parallel to the interface. A ZnO precipitate was terminated by an oxygen (0001) surface at one end of the precipitate and by a zinc (0001) surface at the other end of the precipitate. A pre-edge peak was detected only in O-K energy-loss near-edge spectra (ELNES) acquired from the oxygen-terminated interface. Ab initio, calculations indicated that the origin of the pre-edge peak could be attributed to the strong chemical bonding and hybridization of Pd-d and O-p orbitals at the oxygen-terminated polar interface.
• Study of Nano-Microstructures on SCC in 316L Stainless Steel

  H. Takahashi, R. Ishibashi, T. Kato, N. Sakaguchi, S. Watanabe

  Proceedings of 7th Polish-Japanese Joint Seminar on Micro and Nano Analysis, Warsaw, Poland, September 7-10, 2008 (The Institute of Electron Technology, Warsaw, Poland) Paper No. B2. 2  2008年 [査読有り][通常論文]
  
• Ion implantation induced martensite nucleation in SUS301 steel

  Hiroshi Kinoshita, Heishichiro Takahashi, Dwi Gustiono, Norihito Sakaguchi, Tamaki Shibayarna, Seiichi Watanabe

  MATERIALS TRANSACTIONS 48 5 924 - 930 2007年05月 [査読有り][通常論文]
   

  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.
• Multi-Lorentzian model and 1/f noise spectra

  S Watanabe

  JOURNAL OF THE KOREAN PHYSICAL SOCIETY 46 3 646 - 650 2005年03月 [査読有り][通常論文]
   

  The autocorrelation function of the multi-Lorentzian spectra is shown to be in accord with a 1/f- type noise having a multi-relaxation time distribution, r(-alpha), and yields scaling relation forms when 0 < alpha < 2 (alpha not equal 1). The dependences of alpha on temporal autocorrelation functions in the entire range of 0 <= alpha <= 2, the corresponding power spectra of f(-2+alpha) noise and, the time reversal symmetry on the power number alpha are discussed based on the multi-Lorentzian model. The present results should be applicable to fluctuating phenomena, such as flicker noise effects and self-organized critical phenomena.
• A new model for radiation-induced grain boundary segregation with grain boundary movement in concentrated alloy system

  N Sakaguchi, S Watanabe, H Takahashi

  JOURNAL OF MATERIALS SCIENCE 40 4 889 - 893 2005年02月 [査読有り][通常論文]
   

  We have developed a new model for radiation-induced grain boundary migration (RIGM) and radiation-induced segregation (RIS) for austenitic iron-chromium-nickel alloy system. It was assumed that the RIS was induced by diffusional and annihilation processes of excess point defects at the grain boundary, and the RIGM occurred due to rearrangement process of atoms on one of the interfacial planes by annihilation of point defects. The calculated results indicated that the region of RIS was enlarged by the RIGM and asymmetrical concentration profiles were observed around the migrated grain boundary. The present model could explain the RIS behavior with or without grain boundary migration as comparing with our previous experimental results. (C) 2005 Springer Science + Business Media, Inc.
• 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][通常論文]
  
• Synergistic effect of helium and hydrogen for defect evolution under multi-ion irradiation of Fe-Cr ferritic alloys

  T Tanaka, K Oka, S Ohnuki, S Yamashita, T Suda, S Watanabe, E Wakai

  JOURNAL OF NUCLEAR MATERIALS 329 294 - 298 2004年08月 [査読有り][通常論文]
   

  The purpose of this study is to evaluate the synergistic effect of helium and hydrogen on Fe-Cr ferritic model alloys, to provide basic understanding concerning development of fusion reactor components. Single, dual and triple ion-beams consisting of Fe3+, He+ and H+ were used for irradiation, at temperatures 470-600 degreesC and dose to 50 dpa at 1 mum. The dual beam irradiation with He enhanced cavity nucleation extensively to swelling of about 0.4%, whereas the dual beam irradiation with H did not significantly affect the microstructure. In the case of triple ion irradiation, the synergistic effect of He and H was confirmed clearly; relative large void formation and enhanced swelling to almost 5%. The synergistic effect suggests that the role of H is important for void growth and dislocation bias. (C) 2004 Elsevier B.V. All rights reserved.
• Dynamic and static hydrogen effects on mechanical properties in pure vanadium

  Y Wang, M Kanedome, T Yasuda, T Suda, S Watanabe, S Ohnuki, T Nagasaka, T Muroga

  JOURNAL OF NUCLEAR MATERIALS 329 477 - 480 2004年08月 [査読有り][通常論文]
   

  To clarify hydrogen effects on mechanical properties of pure vanadium, two kinds of tensile tests were performed using hydrogen charged miniature specimens at room temperature. One is with hydrogen charging prior to testing, and the other is with hydrogen charging during testing with continuous or intermittent methods. The cathodic hydrogen charging was carried out electrolytically in various concentrations of H2SO4 with different current densities. The hydrogen charged specimens were tested to obtain stress-strain curves. The fractography was performed by SEM, and hydride formation and microstructural change were examined by TEM. Hydrogen-induced softening and hardening in vanadium resulted from hydrogen charging. The variations in mechanical property of specimens depended on the amount of dissolved hydrogen, that was determined by hydrogen diffusion and hydrogen desorption. Dislocation motion also plays a role in the variation of flow stress. (C) 2004 Elsevier B.V. All rights reserved.
• Effect of alloying elements and neutron-irradiation on hydrogen behavior in V alloys

  S Ohnuki, T Yasuda, T Suda, S Watanabe, BM Oliver

  JOURNAL OF NUCLEAR MATERIALS 329 481 - 485 2004年08月 [査読有り][通常論文]
   

  To understand hydrogen behavior in V and V based alloys, static and dynamic hydrogen chargings were carried out for unirradiated and irradiated V and V-4Cr-4Ti. Hydrogen can be trapped by lattice defects, dislocations, vacancies and voids, which are effective up to 500degreesC. Unexpected softening occurred at low levels of hydrogen, and hardening occurred at high levels. Alloying elements intensified the hardening, which are seen as general phenomena in V and V based alloys. A significant effect was seen for dynamic charging, which was attributed to fast diffusion and interactions with mobile dislocations. (C) 2004 Elsevier B.V. All rights reserved.
• A multi-scale approach to radiation-induced segregation at various grain boundaries

  N Sakaguchi, S Watanabe, H Takahashi, RG Faulkner

  JOURNAL OF NUCLEAR MATERIALS 329 1166 - 1169 2004年08月 [査読有り][通常論文]
   

  We investigated the dependence of radiation-induced segregation (RIS) in austenitic stainless steels on grain boundary orientation by numerical calculations. A new rate equation model for RIS that incorporates the grain boundary sink strength for point defects was developed. The sink strength was determined as functions of misorientation angle and Sigma values using interaction energies of vacancy near grain boundaries as determined by molecular dynamics (MD) and statics (MS). It was shown that the calculated results can reproduce the experimental data obtained by electron and proton irradiation experiments. The good agreement supports the validity of the present model. (C) 2004 Elsevier B.V. All rights reserved.
• Nanostructural fluctuation in radiation-amorphized alloys

  S Watanabe, H Takahashi, NQ Lam

  RADIATION EFFECTS AND ION-BEAM PROCESSING OF MATERIALS 792 159 - 170 2004年 [査読有り][通常論文]
   

  Spatio-temporal nanostructural fluctuations brought about by transient, metastable atom-cluster formation and the manifold nature of inherent atomic ordering in electron-irradiation-amorphized NiTi were investigated by using a combination of in situ observations inside a high-resolution high-voltage electron microscope (HR-HVEM) and image analyses of molecular-dynamics-simulated atom configurations. Nanometer-sized clusters were found to appear and disappear in the irradiated region. The random formation and annihilation of such nanoclusters are believed to be responsible for nanostructural fluctuations which appear to be related to transitions among manifold inherent structural states, involving multirelaxation processes. Temporal fluctuations in the amorphized structure were manifested through the dose-dependent local amorphization parameter, potential energy, volume, and inherent cluster bonding. The observed fluctuations obey a universal power law. Within the framework of the multi-Lorentzian picture, the resultant power law describes the distribution of multirelaxation times or cluster lifetimes. In addition, a unified relation for the temporal autocorrelation function for such fluctuation phenomena has been determined.
• Precipitation and amorphization in boron carbide irradiated by high energy helium ions

  T Maruyama, M Iwanami, S Ohnuki, T Suda, S Watanabe, K Ikezawa

  Effects of Radiation on Materials: 21st International Symposium 1447 670 - 679 2004年 [査読有り][通常論文]
   

  Two kinds of hot-pressed B4C specimens were irradiated with 15MeV He+ from 4.3 x 10(14) to 1.13x 10(16) ion/cm(2) at 400-760 T, and with 100keV He+ from 1.0x10(13) to 2.0x10(17)ion/cm(2) at room temperature. After ion irradiation, the microstructure of specimens was analyzed by transmission electron microscopy (TEM). The ion-irradiation by 15MeV helium ions produced a radiation-enhanced precipitation with Fe-rich composition and the radiation-induced amorphization in the B4C matrix, but the irradiation by 100keV helium did not make amorphization. This result suggests that the inelastic scattering (electron excitation), rather than elastic scattering, plays an important role in amorphization of B4C. The annealing of ion irradiated B4C above 1000 degrees C indicated incineration of precipitated crystals and a formation of a small numbers of helium bubbles.
• Metastable defect cluster formation during radiation-induced amorphization in NiTi

  S Watanabe, T Koike, T Suda, S Ohnuki, H Takahashi, NQ Lam

  MATERIALS TRANSACTIONS 45 1 24 - 28 2004年01月 [査読有り][通常論文]
   

  Chemical and topological disorderings in the NiTi intermetallic compound during electron irradiation were studied using a combination of in situ irradiation inside a high-resolution high-voltage electron microscope and image analyses of molecular-dynamics-simulated atom configurations. It was found that metastable defect clusters formed during the chemical-disordering phase prior to topological disordering leading to amorphization. These planar defect clusters contributed to the characteristic diffuse scattering were also observed in selected-area diffraction patterns.
• Temporal fluctuation and its power law in the crystalline-to-glass transition during electron irradiation

  S. Watanabe, M. Hoshino, T. Koike, T. Suda, S. Ohnuki, H. Takahashi, N. Q. Lam

  Philosophical Magazine 83 22 2599 - 2619 2003年08月01日 [査読有り][通常論文]
   

  Temporal nanostructural fluctuations brought about by transient metastable atom-cluster formation during radiation-induced amorphizing transformation in the intermetallic compound NiTi, observed using a combination of high-resolution high-voltage electron microscopy and molecular dynamics simulation, were characterized in terms of power-law responses of non-equilibrium energy-dissipative systems. Within the framework of the multi-Lorentzian picture, the resultant power law also describes the multirelaxation time (i.e. cluster lifetime) distribution. In addition, a unified relation for the autocorrelation functions for such fluctuation phenomena is discussed.
• Temporal fluctuation and its power law in the crystalline-to-glass transition during electron irradiation

  S Watanabe, M Hoshino, T Koike, T Suda, S Ohnuki, H Takahashi, NQ Lam

  PHILOSOPHICAL MAGAZINE 83 22 2599 - 2619 2003年08月 [査読有り][通常論文]
   

  Temporal nanostructural fluctuations brought about by transient metastable atom-cluster formation during radiation-induced amorphizing transformation in the intermetallic compound NiTi, observed using a combination of high-resolution high-voltage electron microscopy and molecular dynamics simulation, were characterized in terms of power-law responses of non-equilibrium energy-dissipative systems. Within the framework of the multi-Lorentzian picture, the resultant power law also describes the multirelaxation time (i.e. cluster lifetime) distribution. In addition, a unified relation for the autocorrelation functions for such fluctuation phenomena is discussed.
• Non-equilibrium local phase formation by high-speed deformation in NiTi

  S Watanabe, K Kawata, T Kokie, T Suda, S Ohnuki, H Takahashi, Y Matsukawa, M Kiritani

  MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING 350 1-2 145 - 149 2003年06月 [査読有り][通常論文]
   

  Materials responses under non-equilibrium conditions, especially in the state far-from-equilibrium, have been attracting great interest. Although of limited use, there are some tools available for investigating the phenomena, e.g. theoretical approaches such as non-equilibrium thermodynamics or atomistic computer simulation. The present study centers on high-resolution TEM of ordered NiTi specimens subjected to ultra-high-speed plastic deformation at Hiroshima Institute of Technology. Various local nonequilibrium nano-phases were observed to form due to high-speed deformation. Image analysis using high-resolution electron microscopy (HREM) simulation and the FFT technique revealed that those meta-stable phases in the Ni-Ti system were R-phases (Ni4Ti3), O-phases (Ni3Ti2) and amorphous phases. The current study also elaborates on the formation and nature of deformation-induced lattice invariant shear bands. Our results suggest that ultra-high-speed deformation is a promising tool to study the material responses in far-from-equilibrium states. (C) 2002 Elsevier Science B.V. All rights reserved.
• Atomistic observation and simulation analysis of spatio-temporal fluctuations during radiation-induced amorphization

  S Watanabe, M Hoshino, T Koike, T Suda, S Ohnuki, H Takahashi, NQ Lam

  JOURNAL OF ELECTRON MICROSCOPY 52 1 33 - 40 2003年 [査読有り][通常論文]
   

  We performed a dynamic-atomistic study of radiation-induced amorphization in the NiTi intermetallic compound using in situ high-resolution high-voltage electron microscopy and molecular dynamics simulations in connection with image simulation. Spatio-temporal fluctuations as non-equilibrium fluctuations in an energy-dissipative system, due to transient atom-cluster formation during amorphization, were revealed by the present spatial autocorrelation analysis.
• Hydride formation and fracture of vanadium alloys

  P Torres, K Aoyagi, T Suda, S Watanabe, S Ohnuki

  JOURNAL OF NUCLEAR MATERIALS 307 625 - 629 2002年12月 [査読有り][通常論文]
   

  The effects of hydrogen in vanadium, V-5Cr and V-5Ti have been evaluated by the change in surface and in microstructure and by the aspect of fractured surfaces. Hydrogen accumulation promotes local concentration of hydrides and assists the generation of stacking faults. Under increased stress, crack propagation occurs by the successive formation of crack fronts. (C) 2002 Elsevier Science B.V. All rights reserved.
• Effect of surface modification by ion implantation on hydrogenation property of TiFe alloy

  T Suda, M Ohkawa, S Sawada, S Watanabe, S Ohnuki, S Nagata

  MATERIALS TRANSACTIONS 43 11 2703 - 2705 2002年11月 [査読有り][通常論文]
   

  In order to improve initial activation properties of TiFe alloy, simple ion implantation and ion mixing with the deposition of LaNi5 were carried out at room temperature. The results show that argon-ion mixing caused extensive improvement of initial activation, wherein hydrogenation was easily effected at 373 K and 1 MPa. Those results are related to several irradiation effects; the re-crystallization of amorphous film of LaNi5 and the local segregation of composed elements. Both of these irradiation effects greatly improve the initial hydrogenation process of TiFe alloy.
• Dynamical study of spatio-temporal structural fluctuations in the intermetallic compound nickel-titanium during radiation-induced crystalline-to-amorphous transformation

  T Koike, S Watanabe, M Hoshino, T Suda, S Ohnuki, H Takahashi, NQ Lam

  MATERIALS TRANSACTIONS 43 7 1716 - 1718 2002年07月 [査読有り][通常論文]
   

  We have studied nanostructural fluctuations during electron irradiation in the ordered intermetallic compound NiTi by performing irradiation experiments with a high-resolution high-voltage electron microscope (HVEM) and molecular dynamics (MD) simulations. It was observed that atom clusters formed and disappeared repeatedly during irradiation, which results in the structural fluctuation. Comparing the experimental results with the MD simulations, we conclude that such spatio-temporal structural fluctuations under irradiation can be accounted for the evolution of metastable nanoclusters. The present study demonstrates the usefulness of high-resolution HVEM for in situ studies of dynamic, nanoscale fluctuation phenomena.
• Boundary structure of Mo/Si multilayers for soft X-ray mirrors

  M Ishino, O Yoda, Y Haishi, F Arimoto, M Takeda, S Watanabe, S Ohnuki, H Abe

  JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 41 5A 3052 - 3056 2002年05月 [査読有り][通常論文]
   

  Characterizations of Mo/Si multilayers for soft X-ray mirrors have been carried out by high-resolution transmission electron microscopy (TEM) and X-ray scatterings. The crystallite size of oriented Mo in the direction normal to the (110) plane has been found to be approximately equal to the designed thickness of the Mo layer below 8 nm. However, when the Mo layer thickness becomes greater than 8 nm, the crystallite size deviates from the designed thickness and saturates at about 10 nm. The Si layer thickness is smaller than the expected one, which is calculated from the periodic length and the Mo layer thickness, indicating that the mixed layer at the inter-face is formed in the Si layer. The thickness and density of the mixed layer at the Mo-on-Si inter-face are larger than those at the Si-on-Mo interface. The sum of the thicknesses of the mixed layer is about 1.4 nm, irrespective of the Mo/Si composition. Moreover, the density of the mixed layer at the Mo-on-Si interface becomes larger with the increase of the Mo content.
• Improvement of corrosion resistance and structural change in 304 stainless steel by means of ion-mixing

  Y Masumoto, M Takeda, T Suda, S Watanabe, S Ohnuki, T Ohtsuka, K Ikezawa

  MATERIALS TRANSACTIONS 43 4 638 - 640 2002年04月 [査読有り][通常論文]
   

  High-energy ion-beam mixing technique was applied for the surface modification of austenitic stainless steel. followed by electrochemical characterization and microstructural obeservation, The co-mixing of silicon and chromium resisted the passivation current to 1/1000 relative to the un-modified condition. The corrosion resistance improved remarkably. Microstructural observation revealed that the enhanced diffusion and induced amorphous structure introduced by the co-mixing of silicon and chromium, which played a very important role in the improvement of electrochemical behavior at surface.
• Electron-irradiation-induced amorphization in Mo/Si nano-multilayer material

  E Shioya, T Suda, S Watanabe, S Ohnuki, M Ishino, O Yoda, H Abe, F Phillips

  MATERIALS TRANSACTIONS 43 4 650 - 653 2002年04月 [査読有り][通常論文]
   

  In the Mo-Si system, there are three typical intermetallic compounds, In order to get insight into the phase stability under irradiation, interface structure and non-equilibrium phase formation in multilayer materials with several nanometers scale were investigated by means of high-voltage electron microscope. The initial structure was composed of crystalline Mo and amorphous Si layers. and transition layer existed at the interfaces. The thickness of transition layers is thicker at the Mo-on-Si than at the Si-on-Mo interface, While those structures were basically stable after thermal annealing up to 773 K, two types of amorphous layers developed during electron irradiation at room temperature: one is an amorphous-Si layer and the other is a Mo-Si mixing layer. And the radiation-induced amorphization was accompanied by anomalous shrinkage in the thickness of layers. It is suggested that those phenomena are related to non-equilibrium phase formation and biased diffusion process during irradiation.
• Atomistic analysis of stress-induced local amorphization in NiTi alloy

  S Watanabe, Y Haishi, T Suda, S Ohnuki, H Takahashi, M Kiritani

  RADIATION EFFECTS AND DEFECTS IN SOLIDS 157 1-2 101 - 108 2002年01月 [査読有り][通常論文]
   

  In situ tensile straining experiments have been carried out on thin films of the ordered intermetallic compound NiTi (B2 structure) in a high-voltage electron microscope. Real-time observations of stress-induced local amorphization of moving crack tips were followed by high-resolution transmission electron microscopy examination of nanocrystalline regions formed near the crack tip and in the region between the amorphous and crystalline regions. We have also independently confirmed the occurrence of local amorphization by ultra-high speed deformation at an atomistic level in bulk samples of the same NiTi sample. A fast Fourier transformation (FFT) image analysis technique was used to determine the root mean square displacement (RMSD) parameter within the nanocrystalline regions. The RMSD parameter increases to a critical fraction of the nearest neighbor distance of 0.12 +/- 0.01 as the amorphous region is approached, and this finding agrees with the generalized Lindemann melting criterion for amorphization proposed by Okamoto and Lam [1,2]. The present study shows that FFT-real-space analysis technique can provide local measurements of the RMSD parameter in an inhomogeneous system.
• Atomistic study of structural fluctuations during radiation-induced amorphization in the ordered intermetallic compound NiTi

  S Watanabe, T Koike, T Suda, S Ohnuki, H Takahashi, NQ Lam

  PHILOSOPHICAL MAGAZINE LETTERS 81 11 789 - 794 2001年11月 [査読有り][通常論文]
   

  We have carried out an atomistic study of electron-induced amorphization of an ordered intermetallic compound NiTi by means of in-situ high-resolution high-voltage electron microscopy observations and molecular dynamics simulations. Both theoretical and experimental results show that metastable nanometre-size atomic clusters form and disappear during irradiation, so that a spatiotemporal fluctuation under amorphization is induced. Mean-lifetime measurements of these clusters demonstrate that high-energy particle irradiation provides a useful tool to study dynamic fluctuations of the local atomic structure in the non-equilibrium open systems.
• Heterogeneous dislocation formation and solute redistribution near grain boundaries in austenitic stainless steel under electron irradiation

  N Sakaguchi, S Watanabe, H Takahashi

  ACTA MATERIALIA 49 7 1129 - 1137 2001年04月 [査読有り][通常論文]
   

  We investigated the radiation-induced segregation (RIS) near grain boundaries in austenitic stainless steel under electron irradiation, taking into account the simultaneous evolution of faulted dislocation loops and network dislocations. The formation of a dislocation-free zone (DLFZ) in the vicinity of the grain boundary due to in situ irradiation was observed using a high-voltage electron microscope (HVEM). Predicted temperature and dose dependencies of DLFZ formation agreed with the experimental results. The relationship between RIS and DLFZ formation near a grain boundary has been substantially clarified. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.
• Electron-irradiation-induced amorphization in Mo/Si nano-multilayer material

  E Shioya, T Suda, S Watanabe, S Ohnuki, M Ishino, O Yoda, H Abe, F Phillip

  PRICM 4: FORTH PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING, VOLS I AND II 1351 - 1353 2001年 [査読有り][通常論文]
   

  Interface structure and non-equilibrium phase formation in multilayer materials with several nanometers scale were investigated by means of high-voltage electron microscopy. The initial structure was composed of crystalline Mo and amorphous Si layers, and transition layer existed at the interfaces. Those structures were basically stable after thermal annealing up to 773 K. Whereas, two types of amorphous layers developed during electron-irradiation at room temperature, and the radiation-induced amorphization was accompanied by anomalous shrinkage in the thickness of layers. It is suggested that those phenomena are related to non-equilibrium phase formation and biased diffusion process during irradiation.
• Effect of surface modification by ion-implantation on hydrogenation property in TiFe alloy

  M Ohkawa, S Sawada, T Suda, S Watanabe, S Ohnuki, S Nagata

  PRICM 4: FORTH PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING, VOLS I AND II 481 - 484 2001年 [査読有り][通常論文]
   

  For the improvement of initial activation properties in TiFe alloy, simple ion-implantation and ion-mixing with the deposition of LaNi5 were carried out at room temperature. As the result, extensive improvement of the initial activation was achieved by Argon ion-mixing, where the hydrogenation took place easily at 373 K and 1 MPa. Those results are related to several irradiation effects; the re-crystallization of amorphous film of LaNi5, the local segregation of composed elements and large amount of lattice defects. All of those factors may affect on the hydrogen dissolution on the surface and the diffusion in sub-surfaces area.
• Preferential amorphization and crystallization in polycrystalline silicon under ion-irradiation

  M Takeda, T Suda, S Watanabe, S Ohnuki, H Abe

  PRICM 4: FORTH PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING, VOLS I AND II 2539 - 2542 2001年 [査読有り][通常論文]
   

  Silicon thin film that was 200 nm in thickness was produced on the silicon oxide (SiO2) by Low Pressure Chemical Vapor Deposition (LPCVD). Heat treatment was given at 1223 K for 4 h under Ar atmosphere. Grain size of polycrystalline silicon (poly-Si) film was about 230 am in diameter. Transmission Electron Microscopy (TEM) specimen was prepared by supporting poly-Si film by Mo grid. In-situ TEM observation was performed under ion-irradiation with 100similar to300 keV C+, N+ and Ar+ at temperature range from 104 K to 773 K. Ion flux was 3.5+/-0.5x10(17) m(2)s(-1). Poly-Si irradiated at 343 K with 100 keV C+ was amorphization in the neighborhood of grain boundaries (GB). This preferential amorphization was recognized in the other irradiation condition. The amorphous phase was grown by the crystal-amorphous interface (C-A interface) migration. On the other hands, at above preferential amorphization temperature, the C-A interface migration in preferential amorphous phase was enhanced crystallization. The migration rate was depended on the mass and the energy of the incident ion. The obtained results are discussed in relation to damage energy from the incident ion.
• Inter-diffusion and amorphization during ion-irradiation in Mo/Si nano-multi-layer materials

  S Ohnuki, F Arimoto, S Watanabe, PR Okamoto, NQ Lam, H Abe

  PRICM 4: FORTH PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING, VOLS I AND II 1331 - 1333 2001年 [査読有り][通常論文]
   

  We focused on the non-equilibrium phase formation and diffusion in multi-layers in several nanometers scale by using "in-situ" observation of ion irradiation. In the samples deposited on Si substrate, the initial structure is composed of crystalline Mo and amorphous Si layers. The mixing layers with amorphous structure were formed immediately after the ion-irradiation at room temperature. Diffusion-assisted tiny voids (<1 nm) developed at the interface and then line up at the center of the a-Si layer. This is a result of a Kikrendall effect, suggesting an intensive diffusion of Si toward c-Mo at room temperature. These phenomena are discussed from non-equilibrium phase formation and biased diffusion process, which can be induced irradiation.
• Dynamical study of radiation-induced amorphization in NiTi by high resolution - High voltage electron mcroscopy

  T Koike, S Watanabe, T Suda, S Ohnuki, H Takahashi

  PRICM 4: FORTH PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING, VOLS I AND II 1347 - 1349 2001年 [査読有り][通常論文]
   

  The irradiation of energetic particles often induces chemical disordering, and subsequent amorphization of a variety of ordered intermetallic compounds. An implicit assumption of current theories of the phenomenon is that a critical degree of chemical disorder is necessary to initiate the crystal-to-amorphous transition and that once formed the amorphous phase grows monotonously with irradiation time. The development of high resolution-high-voltage electron microscopy (HR-HVEM) has made it possible to carry out in situ real-dine studies of radiation-induced structural changes on the atomic-scale. MM X structure) samples were irradiated with 1.25 MeV electrons (dose rate 1.0x10(24) e m(-2)sec(-1)) at 300, 323,373 and 523 K in HR-HVEM (JEM-ARM1300). In situ atomistic observations of electron-induced amorphization show that metastable nanometer-size atomic dusters form and disappear during irradiation. This clustering behavior induces a fluctuation in radiation-induced amorphization process. Molecular dynamics simulations also support to observe this phenomenon.
• In-situ observation of initial hydiride formation in zirconium alloys modified by ion-implantation and ion-mixing

  T Suda, R Kobayashi, S Watanabe, S Ohnuki

  PRICM 4: FORTH PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING, VOLS I AND II 489 - 492 2001年 [査読有り][通常論文]
   

  The hydride formation on the surface of ZrCo and ZrNi under hydrogen exposure was investigated at 423-473 K by means of Hot-Stage Microscope. In the case of ZrCo, hydrides formed with and without ion-implanted area, the ion-mixing of Co and Ni enhanced the growth rate of hydrides by 2-3 times. The activation energy for the growth was 40 kJ/mol for the non-treated sample, and it was 32 kJ/mol for the Co ion-mixing sample. In the case of ZrNi, after implantation was 28-40 kJ/mol and depended on the ion dose. The process of the hydrogenation was different in the nucleation, growth and cracking of both alloys, Those results indicate the ion-implantation drastically activate initial stage of hydrogenation.
• Spatio-temporal structural fluctuations in the intermetallic compound NiTi during radiation-induced crystalline-to-amorphous transformation

  S Watanabe, T Koike, M Hoshino, T Suda, S Ohnuki, H Takahashi, NQ Lam

  PRICM 4: FORTH PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING, VOLS I AND II 1339 - 1341 2001年 [査読有り][通常論文]
   

  We studied nanostructural fluctuations during electron irradiation of the ordered intermetallic compound NiII by means of molecular dynamics (MD) simulations and irradiation experiments with a high resolution high-voltage electron microscope (HVEM). It was observed that metastable, nanosized atom clusters formed and disappeared during irradiation. Comparing the experimental results with the MD simulations, we interpret the spatio-temporal fluctuations of the irradiated structure in terms of evolution of these nanoclusters. The present study demonstrates that the dynamic; atomic-scale structural fluctuation phenomenon can be studied in situ using irradiation inside a high resolution HVEM.
• Sink effect of grain boundary on radiation-induced segregation in austenitic stainless steel

  S Watanabe, Y Takamatsu, N Sakaguchi, H Takahashi

  JOURNAL OF NUCLEAR MATERIALS 283 152 - 156 2000年12月 [査読有り][通常論文]
   

  We have investigated the orientation dependence of grain boundaries in radiation-induced segregation (RIS) in an austenitic stainless steel under irradiation using a high-voltage electron microscope (HVEM) at the Hokkaido University HVEM facility and a new rate equation model for RIS, which incorporates the grain boundary sink strength for point defects. The [110] tilt grain boundaries were chosen for the present study. It was observed that, after electron irradiation at a dose rate of 2.0 x 10(-3) dpa s(-1) to 10 dpa at temperatures of either 623 or 723 K, RIS was enhanced as the tilt angle increased but was suppressed at coincidence grain boundaries (Sigma9 and Sigma3). The present result indicates that one needs to explicitly consider the grain boundary sink strength as an important factor affecting radiation-induced grain boundary phenomena (RIGBPH). This work can be thought as a study of the radiation-induced grain boundary phenomena associated with grain boundary engineering related to non-equilibrium phenomena. (C) 2000 Elsevier Science B.V. All rights reserved.
• Effect of mechanical alloying parameters on irradiation damage in oxide dispersion strengthened ferritic steels

  S Yamashita, S Watanabe, S Ohnuki, H Takahashi, N Akasaka, S Ukai

  JOURNAL OF NUCLEAR MATERIALS 283 647 - 651 2000年12月 [査読有り][通常論文]
   

  Issues for developing oxide dispersion strengthened (ODS) steel are anisotropic mechanical properties due to the bamboo-like structure, impurity pick up during the mechanical alloying (MA) process, stability of oxide particles, heat-treatment condition and chemical composition. Several ODS steels were fabricated with a changing gas environment during MA, heat-treatment condition and chemical composition, and were electron-irradiated to 12 dpa at 673-748 K in a high-voltage electron microscope. An ODS martensitic steel (M-Ar) with high dislocation density showed very good swelling resistance. Swelling levels of ODS ferritic steels depended on the gas environment during MA and the recrystallization condition. These indicated that a helium gas environment during MA was more effective to suppress swelling than an argon gas environment and that cold working after recrystallization reduced void formation and swelling. The effect of MA parameters, such as the gas environment, heat-treat condition and cold working on the swelling behavior was evaluated. (C) 2000 Elsevier Science B.V. All rights reserved.
• Misorientation dependence of grain boundary segregation under electron irradiation in an austenitic stainless steel

  S Watanabe, Y Takamatsu, N Sakaguchi, H Takahashi

  JOURNAL DE PHYSIQUE IV 10 P6 173 - 178 2000年04月 [査読有り][通常論文]
   

  The effect of grain boundary misorientation on intergranular Radiation-Induced Segregation (RIS) in an Fe-15Cr-20Ni alloy was studied using a high voltage electron microscope (HVEM) at Hokkaido University HVEM facility and a rate equation model for RIS which incorporated grain boundary sink strength. The < 110 > tilt grain boundaries were chosen for the present study. It was observed that after electron irradiation with 3x10(-3) dpa/s to 3 dpa at both temperatures of 623 K and 723 K, RIS was enhanced as the tilt angle increases but was suppressed at coincidence grain boundaries (Sigma 9 and Sigma 3). The present result indicates that one needs explicitly to consider the grain boundary sink strength for point defects as an important factor affecting radiation induced grain boundary phenomena.
• Effect of ion-irradiation on phase transformation in TiNi shape memory alloys

  Y Matsukawa, Y Sumita, S Ohnuki, S Watanabe, C Namba, H Takahashi

  EFFECTS OF RADIATION ON MATERIALS: 19TH INTERNATIONAL SYMPOSIUM 1366 1147 - 1158 2000年 [査読有り][通常論文]
   

  Ion-irradiation induced amorphization and crystallization processes in TiNi shape memory alloys have been investigated. The primary concern is to clarify the relationship between the critical temperature for irradiation-induced amorphization and the thermal crystallization temperature. The critical temperature for irradiation-induced amorphization was 673K, however, the edge of the foil specimen crystallized during the irradiation at a lower temperature. The crystallization temperature of the specimen edge during irradiation decreased with increasing of incident ion energy. Thermal annealing experiments revealed that the thermal crystallization preferentially occurred at the specimen edge and the crystalline-amorphous (C-A) interface; The crystallization temperature of the preferential sites were 573K and 623K, respectively. These preferential nucleation indicate that the nucleation barrier dominates the thermal crystallization temperature; the critical temperature for amorphization is higher than the thermal crystallization temperature with no nucleation barrier.
• A composite model for segregation and microstructural evolution under electron irradiation

  S Watanabe, N Sakaguchi, H Takahashi, S Ohnuki

  EFFECTS OF RADIATION ON MATERIALS: 19TH INTERNATIONAL SYMPOSIUM 1366 919 - 931 2000年 [査読有り][通常論文]
   

  We have investigated radiation-induced segregation (RIS) near a grain boundary in an austenitic stainless steel under electron irradiation taking into account the simultaneous evolution of faulted dislocation loops and network dislocations by a composite model. It has been found that dislocation free zones (DLFZ) formed in the vicinity of the grain boundary by the irradiation, and we carried out direct observation of the DLFZ formation by in-situ irradiation in a high-voltage electron microscope (HVEM). Prediction of temperature and dose dependence of DLFZ formation agreed with experimental results. The inter-relationship between RIS and DLFZ formation near a grain boundary has been substantially clarified. RIS and DLFZ were understood considering point defect and solute flow associated with the excess defect to the grain boundary.
• Effect of additional minor element on radiation-induced grain boundary segregation in austenitic stainless steel under electron irradiation

  N Sakaguchi, S Watanabe, H Takahashi

  NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 153 1-4 142 - 146 1999年06月 [査読有り][通常論文]
   

  Radiation-induced segregation (RIS) influences the chemical and mechanical properties of structural materials of fission and fusion reactors. In the present study, we investigated the effect of minor alloying elements on RIS in austenitic stainless steel on the basis of the rate theory at or near grain boundaries. It was assumed that the additional minor elements interacted with vacancies and formed additive-vacancy complexes. The effects of additional element concentration and the binding energy between additives and vacancies on solute segregation at the grain boundary were clarified by the present calculations, and the results were compared with recent electron irradiation experiments using a high-voltage electron microscope (HVEM). (C) 1999 Published by Elsevier Science B.V. All rights reserved.
• 水素吸蔵合金の微粉化に及ぼす材料因子

  須田 孝徳, 小林 良一, 渡辺 精一, 大貫 惣明, 高橋 平七郎, 荒島 裕信, 兜森 俊樹

  日本金屬學會誌 63 5 601 - 604 公益社団法人 日本金属学会 1999年05月 [査読有り][通常論文]
   

  Most of hydrogen storage alloys show decrepitation during hydriding-dehydriding cycles. The decrepitation assists initial activity and reaction rate. However, it causes lowering of thermal conductivity, difficulties of handling, degradation and others. In this work, the decrepitation process was examined with regard to mechanical properties and microstructure.
  Four types of alloys; LaNi₅, TiMn_1.5, TiFe_0.8C_0.1 and ZrNi are used for this work. Compression test, Vickers hardness measurement and high-resolution electron microscopy observation were carried out before and after hydrogenation. Ductile alloys did not show remarkable decrepitation. Brittle alloys showed typical decrepitation, in which the nano crystal grains were observed by use of high-resolution microscopy. These results emphasize that the decrepitation process is different each other’s, depending on the ductility or brittleness of the alloys.
• Formation and stability of metallic silicides during ion-beam-mixing in the systems of Mo Si and Ti Si

  F Arimoto, M Takeda, T Suda, S Watanabe, S Ohnuki, H Takahashi, H Abe, H Naramoto

  MATERIALS TRANSACTIONS JIM 40 5 408 - 411 1999年05月 [査読有り][通常論文]
   

  In order to form the silicide at relatively low temperature, ion-beam-mixing was applied to Mo/Si and Ti/Si systems in a temperature range from room temperature to 473 K. After the irradiation of 1 MeV Si+, the cross-sectional specimens were examined by transmission electron microscopy and X-ray microanalysis. Crystalline silicide formation was achieved only in Mo/Si system irradiated to high dose at each temperature. The evaluation of interdiffusion coefficient indicated that the diffusion is predominant in the ion-beam-mixing process. The nucleation process of silicide and the phase stability are discussed.
• Defect-flow-induced heterogeneous dislocation formation and solute redistribution near a grain boundary in austenitic stainless steel under electron irradiation

  S Watanabe, N Sakaguchi, S Mochizuki, H Takahashi

  JOURNAL OF NUCLEAR MATERIALS 271 184 - 188 1999年05月 [査読有り][通常論文]
   

  The authors investigated radiation-induced segregation (RIS) at a grain boundary in an Fe-Cr-Ni alloy under irradiation taking account of the evolution of faulted dislocation loops and network dislocations. Electron irradiation with a high voltage electron microscope (1000 kV) at Hokkaido University, Japan, was performed to study radiation-induced solute segregation and point defect flow in a typical austenitic Fe-Cr-Ni alloy. The theoretical analysis was conducted by solving the coupled rate equations for solute and defect concentrations near a grain boundary sink. The experimental solute redistribution profiles predicted by the theory were explained qualitatively. The formation of dislocation free zone (DLFZ) in the vicinity of a grain boundary was also observed during in situ observation under electron irradiation. The temperature dependence of the segregation width and that of DLFZ zone width show similar trends. It is thus suggested that RIS and DLFZ formation should be explained by the defect-flow-induced phenomenon under irradiation. The inter-relationship between RIS and such heterogeneous defect clustering near a grain boundary was also clarified substantially. (C) 1999 Elsevier Science Inc. All rights reserved.
• Effect of stress and impurities on preferential amorphization on grain boundaries in polycrystalline silicon

  M Takeda, S Ohnuki, S Watanabe, H Abe, H Naramoto, PR Okamoto, NQ Lam

  MICROSTRUCTURAL PROCESSES IN IRRADIATED MATERIALS 540 37 - 42 1999年 [査読有り][通常論文]
   

  Clarifying the local amorphization on the grain boundaries, the in-situ observation during ion-irradiation was carried out for poly-crystalline Si film. The critical dose of amorphous formation increased exponentially with increasing temperature, where the local amorphization was developed at middle temperature. The critical dose was affected by the doped impurity and the grain size. The preferential amorphization on and near grain boundaries had two processes; first stage with rapid growth rate and second stage with almost constant growth rate. The importance of stress was demonstrated from the acceleration due to the stress on the first stage of amorphization.
• Behavior of Fe-Cr-Ni-xP-yTi alloys under electron/He ion dual beam irradiation

  H Takahashi, H Tsuchida, Y Hidaka, H Kinoshita, S Watanabe

  EFFECTS OF RADIATION ON MATERIALS: 18TH INTERNATIONAL SYMPOSIUM 1325 701 - 709 1999年 [査読有り][通常論文]
   

  The effect of helium on microstructural development during dual beam irradiation with electrons/He+ ions was examined for Fe-16wt%Cr-14wt%Ni-xwt%P-ywt%Ti (x=0, 0.1, y=0, 0.1) model alloys. Irradiation was carried out using a high voltage electron microscope (1000kv) connecting with 300 keV ion accelerator. The simultaneous ion injection rate was 20 at.ppm He/dpa at 70KeV and irradiation temperatures were 723 X and 773K. In the phosphorus containing alloy, vacancy type dislocation loops were nucleated in the early irradiation stage with electrons beam irradiation, Voids were nucleated from lower dose during electrons/He+ ions dual beam irradiations. In the titanium contained alloy, under electrons/He+ ions dual irradiation, void nucleation was lower comparing to phosphorus containing alloy under electron beam. Furthermore, structural development in alloy containing both titanium and phosphorous was similar to that of alloy with phosphorus and dislocation density was very high. From these results it was clarified that helium strongly influences void nucleation in each alloy as a result of interaction between phosphorus and interstitials.
• Modeling of segregation and microstructural evolution near grain boundary in Fe-Cr-Ni alloy under irradiation

  N Sakaguchi, S Watanabe, H Takahashi

  MULTISCALE MODELLING OF MATERIALS 538 169 - 178 1999年 [査読有り][通常論文]
   

  We have investigated the solute segregation and simultaneous evolution of extended defects in an Fe-Cr-Ni alloy during irradiation by computer simulation. It sheds a light on the accomplishment of performing "the combined total calculation" or "the muliscale modeling" which deals with both radiation-induced segregation and various kinds of internal sink evolution. The formation of dislocation-free zone (DLFZ) was predicted in the vicinity of a grain boundary. It indicated that DLFZ formation is controlled by solute diffusional process via point defects diffusion near the grain boundary and the activation energy obtained by the width of DLFZ corresponds to the half of the value of the radiation-enhanced solute diffusivity.
• Nano-crystalline formation during stress-induced amorphization at crack tips in TiNi

  K Tozawa, Y Haishi, Y Matsukawa, S Watanabe, S Ohnuki, H Takahashi

  JOURNAL OF ELECTRON MICROSCOPY 48 5 613 - 616 1999年 [査読有り][通常論文]
   

  Although the local stress intensification in the immediate vicinity of a crack is known to be the primary driving force for material fracture, the mechanism of crack propagation is not well understood. In the present study in-situ microscopic observations have been carried out on thin films of NiTi intermetallic compounds under tensile loading conditions in a high-voltage electron microscope, followed by high-resolution TEM (HREM) observation. In addition to HREM, observation of the specimen fractured outside HVEM at room temperature was also carried out. Local stress-induced amorphization at moving crack tips has been observed. The HREM observation with a 200 kV FE-TEM revealed nano-crystalline formation in the intermediate region between the amorphous region and the crystalline region.
• On the mechanism of radiation-induced segregation

  S Watanabe, N Sakaguchi, K Kurome, M Nakamura, H Takahashi

  JOURNAL OF NUCLEAR MATERIALS 240 3 251 - 253 1997年02月 [査読有り][通常論文]
  
• Composition and microstructural changes near grain boundaries in an austenitic stainless steel under electron irradiation

  Sakaguchi, N., Watanabe, S., Takahashi, H.

  Annales de Physique 22 3 SUPPL. C2-147 - C2-153 1997年 [査読有り][通常論文]
  
• Radiation-induced segregation at grain boundary in Fe-Cr-Ni alloy system: Effect of temperature variation

  S Watanabe, J Satou, N Sakaguchi, H Takahashi, C Namba

  JOURNAL OF NUCLEAR MATERIALS 239 1-3 200 - 204 1996年12月 [査読有り][通常論文]
   

  The effect of temperature variation during electron irradiation by high-voltage electron microscope (HVEM) on radiation-induced segregation (RIS) at a grain boundary in an austenitic stainless steel was investigated by means of a computer simulation. The calculation was carried out by solving the coupled rate equations for solute and defect concentrations which depend on the Kirkendall effect. The evolution of dislocation sink strength during the temperature variation was also investigated. It turned out that the effect of temperature variation on RIS was very weak and, thus, a high spatial resolution or a high sensitivity detector would be necessary to detect the phenomenon. Moreover, a retardation phenomenon in the sink strength during the temperature variation was found.
• Proceedings of the JIM '95 Fall Annual Meeting (117th) on Lattice Defects and Radiation Induced Phenomena - Honolulu, HI, USA - December 13-15, 1995 - Preface

  H Takahashi, FA Garner, A Kohyama, S Watanabe

  JOURNAL OF NUCLEAR MATERIALS 239 1-3 R7 - R7 1996年12月 [査読有り][通常論文]
  
• Effect of Ni and Cr concentration on grain boundary segregation in Fe-Cr-Ni alloys

  H Kinoshita, S Watanabe, S Mochizuki, N Sakaguchi, H Takahashi

  JOURNAL OF NUCLEAR MATERIALS 239 1-3 205 - 209 1996年12月 [査読有り][通常論文]
   

  Fe-Cr-Ni austenitic alloys were irradiated to investigate the dependence of radiation induced grain boundary segregation on the initial composition of alloying elements. Electron irradiations were performed at grain boundary by using HVEM with 00 keV accelerating voltage. The irradiation temperature was 723 K and the dose was up to 7 dpa. Measurements of grain boundary composition were made using 200 keV TEM with EDS analysis device. Typical grain boundary segregation, such as Ni enrichment and Cr depletion, was recognized in all specimens. The amounts of segregation varied with the contents of alloying elements. For constant bulk Cr (15 wt% Cr) concentration and for increasing bull; Ni concentration, from 15 to 40 wt%, the highest amount of Ni segregation was observed in the range of 25 to 30 wt% Ni specimens, and Cr concentration at grain boundaries was of almost the same level. For constant bulk Ni (20 wt% Ni) content and for increasing bulk Cr content, from 15 to 35 wt%, the amount of Cr segregation at grain boundaries increased with greater Cr bulk content and the amount of Ni segregation was almost the same over the range of 15 to 35 wt% Cr. These tendencies of segregation which depend on the alloying composition were consistent with the computer simulation results of the grain boundary segregation.
• A computational study of dislocation evolution and radiation-induced segregation at a grain boundary

  N Sakaguchi, S Watanabe, H Takahashi

  JOURNAL OF NUCLEAR MATERIALS 239 1-3 176 - 179 1996年12月 [査読有り][通常論文]
   

  Radiation-induced segregation (RIS) influences the chemical and mechanical properties of the structural materials of fusion and fission reactors. In this study, such RIS and dislocation sink strength evolution were investigated on the basis of computer simulation for solute segregation at and near a grain boundary. A new continuity equation model for RIS, based on the rate theory which includes the simultaneous evolution of faulted dislocation loops and network dislocations, has been developed. A di-interstitial was assumed to be the nucleus of a dislocation loop in the present work, and we calculated dislocation evolution due to absorption of interstitials and vacancies. The dependencies of irradiation temperature, irradiation rate and dose on the RIS at a grain boundary under electron irradiation in high-voltage electron microscope (HVEM were clarified. We also considered the effect of probe size used in TEM-EDS analysis in order to satisfy the relationship with measured compositional profiles. The present work sheds a light on the accomplishment of performing 'combined calculation' which deals with both RIS and various kinds of internal sink evolution.
• Theoretical prediction and direct observation of dislocation-free zone formation near a grain boundary in austenitic stainless steel under electron irradiation

  S Watanabe, N Sakaguchi, S Mochizuki, H Takahashi

  PHILOSOPHICAL MAGAZINE LETTERS 74 5 351 - 356 1996年11月 [査読有り][通常論文]
   

  We have investigated the radiation-induced segregation (RIS) near a grain boundary in an Fe-Cr-Ni alloy under electron irradiation taking account of the evolution of faulted dislocation loops and network dislocations. First, we predicted, on the basis of the rate theory, the formation dislocation-free zone (DLFZ) in the vicinity (about 30 nm) of a grain boundary and then carried out direct observation of the DLFZ by in-situ irradiation with high-voltage electron microscopy. The inter-relationship between RIS and heterogeneous defect clustering near a grain boundary has been substantially clarified.
• Effect of additional minor elements on void nucleation in stainless steels during simultaneous irradiation with helium ions and electrons

  S Watanabe, H Tsuchida, Y Hidaka, N Sakaguchi, S Ohnuki, H Takahashi

  JOURNAL OF NUCLEAR MATERIALS 233 177 - 182 1996年10月 [査読有り][通常論文]
   

  The synergistic effect of helium and the addition of the minor elements phosphorus and titanium on void formation in austenitic stainless steels has been studied using a HVEM connected with an ion accelerator. The specimens used were pure Fe-16Cr-14Ni and the same alloy containing either 0.1% P or 0.1% Ti. The electron-induced damage rate was 2 x 10(-3) dpa/s and the helium injection rate was 20 at.ppm/dpa at 70 keV. Dislocation loops of vacancy type were nucleated in the early stage of the electron-only irradiation in the specimen containing phosphorus, but under dual beam irradiation many voids were nucleated and the dislocation loops grew rapidly. When the specimen with titanium was electron-irradiated, void nucleation tended to be reduced but significant void formation occurred due to dual-beam irradiation. In order to explain the result, the free defect concentration has been calculated using a kinetic model based on binding between interstitial and the minor element.
• Radiation-induced segregation accompanied by grain boundary migration in austenitic stainless steel

  S Watanabe, N Sakaguchi, N Hashimoto, M Nakamura, H Takahashi, C Namba, NQ Lam

  JOURNAL OF NUCLEAR MATERIALS 232 2-3 113 - 118 1996年09月 [査読有り][通常論文]
   

  A computer simulation and an electron irradiation in a high voltage electron microscope (1000 kV) were used to study radiation-induced solute segregation and point defect flow in typical austenitic Fe-Cr-Ni alloys. The calculation was conducted by solving the coupled rate equations for solute and defect concentrations considering the Kirkendall effect at a moving grain boundary sink. The experimental solute redistribution profiles were explained qualitatively. Redistribution of nickel and chromium solutes near the grain boundaries and simultaneously grain boundary migration occurred during irradiation. The amount of nickel enrichment at a grain boundary was especially remarkable, comparing to the amount of chromium depletion. It is suggested that grain boundary migration may contribute to the flow of under-sized nickel solute toward the boundary. The influence of the probe size on EDS analysis of compositional profiles was investigated, with some experimental data.
• Theoretical and experimental studies of irradiation-induced grain boundary migration depending on orientation

  H Takahashi, N Sakaguchi, N Hashimoto, S Watanabe

  INTERGRANULAR AND INTERPHASE BOUNDARIES IN MATERIALS, PT 2 207- 561 - 564 1996年 [査読有り][通常論文]
   

  Fe-Cr-Ni,Ni-Si and Ni-Al alloys were electron-irradiated using a high voltage electronmicroscopy (1000kV),and in situ observation on structural evolution and microchemical analysis were carried out. When the Fe-Cr-Ni alloy was irradiated, there occurred the nucleation of dislocation loops followed by voids and at the same time grain boundary migration occurred. The compositional analysis after irradiation of an area including the migrated grain boundary indicated nickel enrichment and chromium depletion. Furthermore the grain boundary tended to migrate toward a coarser facing boundary plane. The same grain boundary migration and compositional change at the boundary was recognized in Ni-Si alloy. These results suggested that boundary migration and solutes redistribution are closely related to irradiation-introduced point defects flow, especially interstitial atoms and the direction of the boundary migration depends on the relationship between the two grains.
• CONCENTRATION-DEPENDENCE OF RADIATION-INDUCED SEGREGATION IN FE-CR-NI ALLOY

  S WATANABE, H KINOSHITA, N SAKAGUCHI, H TAKAHASHI

  JOURNAL OF NUCLEAR MATERIALS 226 3 330 - 331 1995年11月 [査読有り][通常論文]
  
• QUANTITATIVE STUDIES OF IRRADIATION-INDUCED SEGREGATION AND GRAIN-BOUNDARY MIGRATION IN FE-CR-NI ALLOY

  S WATANABE, N SAKAGUCHI, N HASHIMOTO, H TAKAHASHI

  JOURNAL OF NUCLEAR MATERIALS 224 2 158 - 168 1995年08月 [査読有り][通常論文]
   

  An irradiation-induced phenomenon was studied on account of solute segregation and concurrent grain boundary migration in a model Fe-Cr-Ni alloy during electron irradiation with a high voltage electron microscope (1000 kV) and also by computer simulation. The calculation was conducted by solving the coupled rate equations for solute and defect concentrations, which involve the Kirkendall effects at a grain boundary sink, so that the solute redistribution profiles experimentally obtained were quantitatively explained. We also extensively studied the effects of the probe size in the EDS analysis on composition profiles, the Gibbsian segregation in the vicinity of a grain boundary and the discriminant of segregation under irradiation, as well as other important factors that influence the phenomenon.
• Grain boundary segregation under irradiation in a HVEM

  H Takahashi, T Kato, S Watanabe, N Sakaguchi

  ANNALES DE PHYSIQUE 20 3 109 - 116 1995年06月 [査読有り][通常論文]
   

  Solute redistribution and microstructural development in the vicinity of grain boundaries in Fe-19Cr-XMn-3Al (X=5,10,15) alloys were studied under electron irradiation to about 10 dpa at 725 K in a high voltage electron microscope in order to simulate the segregation behavior during neutron irradiation. The oversized solute atoms, manganese and aluminum, were depleted at grain boundaries, whereas the concentration of chromium increased even though it is an oversized one. The segregation behavior of aluminum and manganese was related to size effect. However,with increasing manganese concentration the size factor decreased and then the amount of depletion of the solutes decreased with manganese concentration. The enrichment of chromium seemed to be related to chromium-rich precipitate formation at the boundary.
• DEFECT-FLOW-INDUCED GRAIN-BOUNDARY MIGRATION WITH SEGREGATION UNDER ELECTRON-IRRADIATION

  H TAKAHASHI, N HASHIMOTO, S WATANABE

  ULTRAMICROSCOPY 56 1-3 193 - 199 1994年11月 [査読有り][通常論文]
   

  An Fe-Cr-Ni alloy was electron-irradiated using a high voltage electron microscope (1 MV), and in situ observations on the structural evolution and microchemical analysis were carried out. The compositional analysis showed that under irradiation an area near a grain boundary was nickel-enriched and chromium-depleted, and that, simultaneously, grain boundary migration occurred. Moreover, the distance of the grain boundary migration increased almost linearly with the degree of segregation, and the migration occurred predominantly in the direction perpendicular to close-packed crystal planes. Underpinned with computer calculations, it is suggested that when the radiation-induced point defects flow into the grain boundary, boundary migration and solute redistribution occur. Furthermore, the magnitude of the effects depends on the net point defect flow, especially that of interstitial atoms.
• EFFECT OF HE ON VOID FORMATION AND RADIATION-INDUCED SEGREGATION IN DUAL-BEAM IRRADIATED FE-CR-NI

  Y HIDAKA, S OHNUKI, H TAKAHASHI, S WATANABE

  JOURNAL OF NUCLEAR MATERIALS 212 330 - 335 1994年09月 [査読有り][通常論文]
   

  To investigate the effect of helium on void formation and radiation-induced segregation, dual-beam irradiation with electrons and helium ions has been carried out for an Fe-Cr-Ni alloy by using a 1000 keV HVEM and a 300 keV ion-accelerator. From the measurement of dislocation loop growth, the vacancy migration energy was estimated at different injection rates of helium. The value increased with increasing injection rate of helium, which means strong trapping between vacancies and helium atoms. As a result the mutual recombination of point defects is retarded and the formation of secondary defects can be enhanced. Namely, on increase the densities of voids and dislocations was observed, as compared with the result without helium. With respect to the radiation-induced segregation, depletion of Ni and enrichment of Cr in the irradiated area were detected. The segregation of Ni and Cr was suppressed with increasing helium. From these results the role of helium on radiation-induced segregation is discussed on the basis of vacancy trapping and internal sinks.
• 有効質量法によるフェルミ面の解析

  渡辺 精一

  まてりあ 33 3 261 - 267 The Japan Institute of Metals and Materials 1994年
• Theoretical and Experimental Studies of Irradiation-Induced Grain Boundary Migration and Segregation

  H. Takahashi, N. Hashimoto, S. Watanabe, N.Q. Lam

  The 1994 Gordon Res. Conf. on Particle Solid Interactions 1994年 [査読有り][通常論文]
  
• DISCRIMINANT OF RIS IN MULTICOMPONENT ALLOYS

  S WATANABE, H TAKAHASHI

  JOURNAL OF NUCLEAR MATERIALS 208 1-2 191 - 194 1994年01月 [査読有り][通常論文]
  
• Mechanical Properties in B2 FeAl without Frozen-in Vacancies

  K. Yoshimi, N. Matsumoto, S. Hanada, S. Watanabe

  Proceedings of the 3rd Japan International SAMPE Symposium 2 1404 - 1409 1993年12月 [査読有り][通常論文]
  
• RELATIONSHIP BETWEEN SUPERCONDUCTIVITY AND BAND STRUCTURES OF ELECTRONS AND PHONONS

  S FUJITA, S WATANABE

  JOURNAL OF SUPERCONDUCTIVITY 6 2 75 - 79 1993年04月 [査読有り][通常論文]
   

  The relationship between superconductivity and band structures of electrons and phonons is established on the basis of a generalized Bardeen-Cooper-Schrieffer model in which the interaction strengths (V11, V12, V22) among and between ''electron'' (1) and ''hole'' (2) Cooper pairs are differentiated. Elemental superconductors must have local hyperboloidal Fermi surfaces called ''necks'' or ''inverted double caps.''
• ON THE (110) CYLINDRICAL FERMI-SURFACE AND THE ANISOTROPIC CYCLOTRON-RESONANCE PEAK IN LEAD

  S WATANABE, H TAKAHASHI, S FUJITA

  JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 54 3 325 - 329 1993年03月 [査読有り][通常論文]
   

  The angular dependence of the Azbel'-Kaner cyclotron resonance peaks in lead is analyzed. All of the anisotropies in the cyclotron resonance peaks originating from the [110] arms of the Fermi surface in the third band are shown to be characterized by a set of three effective masses with one negative, corresponding to a hyperboloidal shape of the Fermi surface. The splitting of the cyclotron resonance peaks found by Khaikin and Mina [Sov. Phys.-JETP 15, 24 (1962)] is also explained by the set of masses in terms of the approximately 3.2 degree misalignment of the (001) sample surface.
• THEORY OF SUPERCONDUCTIVITY .3. 2D-CONDUCTION BANDS FOR HIGH-TC - BOSE-EINSTEIN CONDENSATION TRANSITION OF THE 3RD ORDER

  S FUJITA, S WATANABE

  JOURNAL OF SUPERCONDUCTIVITY 5 3 219 - 237 1992年06月 [査読有り][通常論文]
   

  A general theory of superconductivity is developed, starting with a BCS Hamiltonian in which the interaction strengths (V11, V22, V12) among and between "electron" (1) and "hole" (2) Cooper pairs arc differentiated, and identifying "electrons" ("holes") with positive (negative) masses as those Bloch electrons moving on the empty (filled) side of the Fermi surface. The supercondensate is shown to be composed of equal numbers of "electron" and "hole" ground (zero-momentum) Cooper pairs with charges +/-2e and different masses. This picture of a neutral supercondensate naturally explains the London rigidity and the meta-stability of the supercurrent ring. It is proposed that for a compound conductor the supercondensate is formed between "electron" and "hole" Fermi energy sheets with the aid of optical phonons having momenta greater than the minimum distance (momentum) between the two sheets. The proposed model can account for the relatively short coherence lengths xi observed for the compound superconductors including intermetallic compound, organic, and cuprous superconductors. In particular, the model can explain why these compounds are type 11 superconductors in contrast with type I elemental superconductors whose condensate is mediated by acoustic phonons. A cuprous superconductor has 2D conduction bands due to its layered perovskite lattice structure. Excited (nonzero momentum) Cooper pairs (bound by the exchange of optical phonons) above T(c) are shown to move like free bosons with the energy-momentum relation epsilon = 1.2v(F)q. They undergo a Bose-Einstein condensation at T(c)= 0.977hv(F)k(B)-1n1/2BAR, where n is the number density of the Cooper pairs. The relatively high value of T(c) (approximately 100 K) arises from the fact that the density n is high: n1/2 approximately xi-1 approximately 10(7) cm-1. The phase transition is of the third order, and the heat capacity has a reversed lambda (lambda)-like peak at T(c).
• ON THE ANGULAR-DEPENDENCE OF THE CYCLOTRON-RESONANCE PEAKS IN LEAD

  S WATANABE, S FUJITA

  JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 52 8 985 - 989 1991年 [査読有り][通常論文]
   

  The angular dependence of the Azbel'-Kaner cyclotron resonance peaks in lead is analyzed in terms of Shockley's formula. All of the anisotropies in the cyclotron resonance peaks originating from the <110> cylindrical arms of the Fermi surface measured in the four parallel field geometries by O triple-overdot nuki et al. [J. Phys. Chem. Solids 38, 419 (1977)] are shown to be characterized by the set of the effective masses (m1, m2, m3) = (1.18, 0.244, -8.71)m along the crystal directions ([001], [110BAR], [110]) and their equivalents. This means that the cyclotronic motion in the {110} planes is electron-like and its orbits are elliptic in k-space characterized by masses (m1, m2) while the heli-axial motion is hole-like. The physical origins of this unusual behavior are discussed in direct-lattice space.
• ON THE ORIENTATION DEPENDENCE OF THE CYCLOTRON-RESONANCE PEAKS FOR HOLES IN GE AND SI

  S FUJITA, S WATANABE

  PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 158 1 K69 - K73 1990年03月 [査読有り][通常論文]
  
• THEORY OF THE ANISOTROPIES IN THE CYCLOTRON-RESONANCE PEAKS FOR ELECTRONS IN GE BASED ON HEXAGONAL ORBITALS

  S FUJITA, S WATANABE

  SOLID STATE COMMUNICATIONS 72 6 581 - 583 1989年11月 [査読有り][通常論文]
  
• ON THE CONDUCTANCE OF A LATTICE-LIKE NETWORK

  S FUJITA, A GARCIA, D OLEYAR, S WATANABE, T BURNETT

  JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 50 1 27 - 31 1989年 [査読有り][通常論文]
  
• 個体群の生長が時間遅れの制御下にある資源個体群に対する放流効果〔英文〕

  渡邊 精一

  日本水産学会誌 54 2 183 - 186 日本水産學會 1988年 

  The simple logistic model with time lag control is employed to consider the constant rate stocking effects. Stocking increases the equilibrium level of the population. The stability of the equilibrium depends on all parameters employed in the model. The equilibrium becomes unstable and the limit cycle arises under the sufficient level of stocking although the product of the increasing rate and time lag is less than π/2. Stocking produces the increase of the amplitude and the decrease of the period of the population's fluctuation. Careful stocking is desired in controlling natural populations.
• DEVELOPMENT OF 100 kgf/mm**2 GRADE HIGH TENSILE STRENGTH THICK PLAE.

  Matsuoka, Takashi, Watanabe, Seiichi, Bessyo, Kiyoshi, Iida, Yutaka, Kawai, Kiyokaze, Watanabe, Nozomu

  Sumitomo Metals 38 2 1986年

書籍

• Statistical and Condensed Matter Physics: Over the Horizon

  藤田 重次, 小幡 常啓, 鈴木 公 
  NOVA publishers 2007年 (ISBN: 9781600217586)
• 超伝導の量子統計理論―初歩から学ぶ超伝導

  岡村 好庸, 鈴木 彰, 小幡 常啓, 渡辺 精一 (担当:共訳)
  藤田 重次, サルバドール ゴドイ シュプリンガー・フェアラーク東京 2001年07月 (ISBN: 4431709290) 362

  

講演・口頭発表等

• 無機-生物ハイブリッド人工光合成システムによる酢酸合成

  松尾稜介, 高橋優樹, 百瀬皓太, 渡辺精一, 岡部聡

  日本水環境学会年会講演集 2020年
• 鉄の腐食に伴う水のイオン分離現象

  村上俊太郎, 張麗華, 渡辺精一

  日本鉄鋼協会日本金属学会両支部合同冬季講演大会概要集 2020年
• ガルバニック水中結晶光合成法の基礎と機能表面作製

  高橋優樹, 平岩健聖, 水野潤一, JEEM Melbert, ZHANG Lihua, 渡辺精一

  日本鉄鋼協会日本金属学会両支部合同冬季講演大会概要集 2020年
• 次世代光触媒材料としてのタンタル酸カリウムの作製と応用

  森山拓哉, 沖中憲之, 張麗華, 渡辺精一

  日本鉄鋼協会日本金属学会両支部合同冬季講演大会概要集 2020年
• A‐USC用ボイラ伝熱管へのNi添加SiAlON溶射時の成膜過程と被膜厚さ  [通常講演]

  沖中憲之, 橋本燎, 張麗華, 渡辺精一, 黒川一哉

  日本鉄鋼協会日本金属学会両支部合同冬季講演大会概要集 2019年01月
• 水中結晶光合成法を用いた表面パターニングと光・電子特性評価

  水野潤一, 平岩健聖, JEEM Melbert, 高橋優樹, 渡辺精一, 渡辺精一

  日本顕微鏡学会北海道支部学術講演会講演要旨集 2019年
• ガルバニック効果を用いた水中結晶光合成による発光性ZnO‐金属ヘテロ構造体の作製  [通常講演]

  平岩健聖, 水野潤一, 高橋優樹, JEEM Melbert, 渡辺精一

  日本顕微鏡学会北海道支部学術講演会講演要旨集 2018年11月
• 鉄の腐食による水イオン分離パターニング形成  [通常講演]

  村上俊太郎, 張麗華, 渡辺精一

  日本金属学会講演概要(CD-ROM) 2018年09月
• ガルバニック水中結晶光合成法による光機能デバイス作製  [通常講演]

  高橋優樹, 平岩健聖, JEEM Melbert, 張麗華, 渡辺精一

  日本金属学会講演概要(CD-ROM) 2018年09月
• 水中結晶光合成における光の役割と表面パターニング応用  [通常講演]

  水野潤一, JEEM Melbert, 高橋優樹, 渡辺精一

  日本金属学会講演概要(CD-ROM) 2018年09月
• イオン照射によるCu基板上の水中光結晶成長制御  [通常講演]

  浅野佑弥, 柴山環樹, 中川祐貴, 渡辺精一

  日本金属学会講演概要(CD-ROM) 2018年09月
• 液相燃焼合成による青色光励起黄色蓄光体の作製  [通常講演]

  後藤智哉, 沖中憲之, 渡辺精一, 張麗華

  日本鉄鋼協会日本金属学会両支部合同サマーセッション概要集 2018年07月
• ガルバニック効果を用いた水中結晶光合成による発光性ZnO‐金属ヘテロ構造体の作製  [通常講演]

  平岩健聖, 高橋優樹, JEEM Melbert, 渡辺精一

  日本鉄鋼協会日本金属学会両支部合同サマーセッション概要集 2018年07月
• 複合量子ビーム照射によるナノ材料創成  [通常講演]

  柴山環樹, 渡辺精一

  日本表面科学会東北・北海道支部講演会講演予稿集 2018年03月
• ナノ秒パルスレーザー照射によるシリコン表面の複合ナノ構造  [通常講演]

  吉田裕, 大西広, 松尾保孝, 渡辺精一

  応用物理学会春季学術講演会講演予稿集(CD-ROM) 2018年03月
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  日本金属学会講演概要(CD-ROM) 2018年03月
• 液相燃焼合成法によって合成されたBi‐SrTiO₃光触媒の可視光活性評価  [通常講演]

  田名瀬佑, 張麗華, 沖中憲之, 渡辺精一

  日本鉄鋼協会日本金属学会両支部合同冬季講演大会概要集 2018年01月
• Photochemistry of Submerged Photosynthesis of Crystallites for Oxide Nanorods Fabrication on Zinc Surface  [通常講演]

  ZHANG Lihua, JEEM Melbert, OKAMOTO Kazumasa, WATANABE Seiichi

  日本金属学会講演概要(CD-ROM) 2017年08月
• グリーン応用のための水中結晶光合成によるナノ鉄水酸化物の創製  [通常講演]

  高井大, 張麗華, 岡本一将, 沖中憲之, 渡辺精一

  材料とプロセス(CD-ROM) 2017年08月
• Photocatalytic metal oxide nanoparticles for total decomposition of water soluble dyes.  [通常講演]

  BIN JULAIHI Muhammad, Rafiq Mirza, SHIBAYAMA Tamaki, WATANABE Seiichi

  Program/Abstracts of ISSS (CD-ROM) 2017年
• 水中結晶光合成法による鉄酸化物・水酸化物のナノ結晶作製  [通常講演]

  高井大, 西野史香, メルバート ジーム, 張麗華, 岡本一将, 沖中憲之, 渡辺精一

  日本金属学会講演概要(CD-ROM) 2016年09月
• 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  [通常講演]

  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) 2016年09月
• 電子ビーム積層造形法の特徴を生かした高強度・高耐食合金の開発  [通常講演]

  藤枝正, 白鳥浩史, 桑原孝介, 広田守, 加藤隆彦, 山中謙太, 小泉雄一郎, 千葉晶彦, 渡辺精一

  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) 2016年08月
• 水中結晶光合成法による酸化銅ナノ表面構造体の創製  [通常講演]

  西野史香, JEEM Melbert, ZHANG Lihua, 岡本一将, 渡辺精一

  表面技術協会講演大会講演要旨集 2016年08月
• SrAl₂O₄蓄光体の組成が蓄光性能に与える影響  [通常講演]

  武井翔一, 張麗華, 沖中憲之, 渡辺精一

  日本鉄鋼協会日本金属学会両支部合同サマーセッション概要集 2016年07月
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  西野史香, JEEM Melbert, 西山賢, 張麗華, 岡本一将, 渡辺精一

  日本金属学会講演概要(CD-ROM) 2016年03月
• 水中結晶光合成法による酸化銅表面ナノ構造化  [通常講演]

  西野史香, JEEM Melbert, 張麗華, 岡本一将, 渡辺精一

  日本鉄鋼協会日本金属学会両支部合同冬季講演大会概要集 2015年12月
• 次世代石炭火力発電用ボイラ伝熱管に向けたSiAlON溶射ステンレス材の微細組織  [通常講演]

  川浪明日翔, 張麗華, 沖中憲之, 大久保賢二, 渡辺精一, 黒川一哉

  日本鉄鋼協会日本金属学会両支部合同冬季講演大会概要集 2015年12月
• 水溶媒中光誘起ナノ結晶合成における不純物効果  [通常講演]

  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) 2015年09月
• パルスレーザー・電子ビーム複合照射によるステンレス鋼の微細組織変化と照射誘起偏析  [通常講演]

  中島啓介, 柴山環樹, 石岡準也, 谷津茂男, 大久保賢二, 谷岡隆志, 渡辺精一

  日本金属学会講演概要(CD-ROM) 2015年09月
• Cu‐P合金電極の大気中焼成挙動と微細組織解析  [通常講演]

  足立修一郎, 加藤隆彦, 渡辺精一

  日本金属学会講演概要(CD-ROM) 2015年09月
• 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  [通常講演]

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  応用物理学会秋季学術講演会講演予稿集(CD-ROM) 2015年08月
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  日本金属学会講演概要(CD-ROM) 2014年09月
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  応用物理学会秋季学術講演会講演予稿集(CD-ROM) 2014年09月
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  応用物理学会秋季学術講演会講演予稿集(CD-ROM) 2014年09月
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  応用物理学会秋季学術講演会講演予稿集(CD-ROM) 2014年09月
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  応用物理学会秋季学術講演会講演予稿集(CD-ROM) 2014年09月
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  応用物理学会秋季学術講演会講演予稿集(CD-ROM) 2014年09月
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  YU Ruixuan, 柴山環樹, 谷津茂男, 石岡準也, 渡辺精一

  応用物理学会秋季学術講演会講演予稿集(CD-ROM) 2014年09月
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  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) 2014年08月
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  日本磁気学会学術講演概要集 2014年08月
• ニッケル合金PE16への粒界工学の適用  [通常講演]

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  溶接学会全国大会講演概要 2014年08月
• PE16合金の小角粒界におけるHe割れに対する許容ずれ角の検討  [通常講演]

  小井戸智, 豊川龍一, 坂口紀史, 柴山環樹, 渡辺精一, 黒川一哉

  日本鉄鋼協会日本金属学会両支部合同冬季講演大会概要集 2014年
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  渡辺精一, 柴山環樹

  日本中性子科学会年会講演概要集 2014年
• 耐熱合金PE16に対する粒界制御効果のブラッグエッジ解析による研究  [通常講演]

  加美山隆, 入山直也, 柴山環, 佐藤博隆, 渡辺精一, 大沼正人, 鬼柳善明

  日本中性子科学会年会講演概要集 2014年
• ナノ秒パルスレーザー照射したFe₅₂Al₄₈表面の磁気特性  [通常講演]

  海住英生, 吉田裕, 大澤和也, 渡辺精一, 近藤憲治, 石橋晃, 吉見享祐

  日本磁気学会学術講演概要集 2013年09月
• 粒界制御フェライト系耐熱鋼SUS410の鉛ビスマス液体金属腐食試験  [通常講演]

  多久島睦子, 吉井陽之輔, 連川貞弘, 森園靖浩, 渡辺精一, 柴山環樹

  日本金属学会講演概要(CD-ROM) 2013年09月
• 粒界制御技術を適用したニッケル基合金PE16の高温引張強度特性評価  [通常講演]

  関尾佳弘, 山下真一郎, 坂口紀史, 柴山環樹, 渡辺精一, 鴇田駿, 藤井啓道, 佐藤裕, 粉川博之

  日本原子力学会秋の大会予稿集(CD-ROM) 2013年08月
• 光ビームによる物質格子制御とグリーン・ナノテクノロジー  [通常講演]

  渡辺精一

  日本金属学会講演概要(CD-ROM) 2013年03月
• ナノ秒パルスレーザー照射によるFeAl表面ナノパターンとその磁気特性  [通常講演]

  吉田裕, 大澤和也, 大澤和也, 渡辺精一, 海住英生, 海住英生, 近藤憲治, 石橋晃, 吉見亨祐

  日本金属学会講演概要(CD-ROM) 2013年03月
• オーステナイト系ステンレス鋼における粒界He割れの粒界性格依存性  [通常講演]

  坂口紀史, 大口裕平, 大口裕平, 柴山環樹, 渡辺精一, 木下博嗣

  日本金属学会講演概要(CD-ROM) 2013年03月
• ナノ秒パルスレーザー照射によるGaSb表面上の酸化ガリウムナノドット成長の臨界サイズ  [通常講演]

  吉田裕, 渡辺精一, 加藤隆彦

  日本鉄鋼協会日本金属学会両支部合同冬季講演大会概要集 2013年01月
• パルス中性子透過分光法によるニッケル基合金のブラッグエッジ解析  [通常講演]

  入山直也, 加美山隆, 柴山環樹, 渡辺精一, 佐藤博隆, 大沼正人, 鬼柳善明

  日本中性子科学会年会講演概要集 2013年
• イオンおよびレーザー同時照射によるAu/SiO₂表面のナノ構造化とその光学特性  [通常講演]

  于睿かん, 柴山環樹, 蒙萱, 吉田裕, 石岡準也, 谷津茂男, 渡辺精一

  日本顕微鏡学会北海道支部学術講演会講演要旨集 2013年
• 先進中性子増倍材料(ベリリウム金属間化合物)の照射硬化  [通常講演]

  柴山環樹, 谷津茂男, 渡辺精一, 岸本弘立, 佐藤学, 木下博嗣, 長坂琢也, XU Q, 徳永和俊, 岩切宏友, 中道勝, 安堂正巳, KIM Jae‐Hwan, 米原和男

  KURRI KR (CD) (CD-ROM) 2013年
• ナノ秒パルスレーザー照射したAu/SiO₂の表面ナノ構造解析と光学特性  [通常講演]

  于睿けん, 于睿けん, 蒙萱, 蒙萱, 柴山環樹, 谷津茂男, 渡辺精一

  日本金属学会講演概要(CD-ROM) 2012年09月

その他活動・業績

• スーパーキャパシタ用Mo-Wナノ酸化物複合材料水中光合成

  林學毅, JEEM Melbert, 張麗華, 渡辺精一 日本金属学会講演大会(Web) 172nd 2023年
• 水中光照射下におけるドーピング誘起光学的相転移

  早野彩夏, JEEM Melbert, 林學毅, 張麗華, 渡辺精一 日本金属学会講演大会(Web) 171st 2022年
• 機能性モリブデン-タングステンナノ酸化物複合材料の水中光合成

  林學毅, JEEM Melbert, 張麗華, 渡辺精一 日本顕微鏡学会北海道支部学術講演会講演要旨集 2022 (CD-ROM) 2022年
• G-SPSCを用いた欠陥制御による色調表面パターニング

  塚村順平, 高橋優樹, 張麗華, ジェーム メルバート, 岡本一将, 渡辺精一 日本金属学会講演大会(Web) 169th 2021年
• 異種金属接触水中光合成法による機能性ヘテロナノ構造体の作製

  高橋優樹, ジェーム メルバート, 渡辺精一 日本金属学会講演大会(Web) 167th 2020年
• 金属酸化物ナノ粒子の水中光合成時の光化学と光の役割

  ZHANG Lihua, JEEM Melbert, WATANABE Seiichi プラズマ応用と複合機能材料 29 2020年
• 次世代光触媒材料としてのタンタル酸カリウムの作製と応用

  森山拓哉, 沖中憲之, 張麗華, 渡辺精一 日本鉄鋼協会日本金属学会両支部合同冬季講演大会概要集 2019 2020年
• ガルバニック水中結晶光合成法の基礎と機能表面作製

  高橋優樹, 平岩健聖, 水野潤一, JEEM Melbert, ZHANG Lihua, 渡辺精一 日本鉄鋼協会日本金属学会両支部合同冬季講演大会概要集 2019 2020年
• 鉄の腐食に伴う水のイオン分離現象

  村上俊太郎, 張麗華, 渡辺精一 日本鉄鋼協会日本金属学会両支部合同冬季講演大会概要集 2019 2020年
• 無機-生物ハイブリッド人工光合成システムによる酢酸合成

  松尾稜介, 高橋優樹, 百瀬皓太, 渡辺精一, 岡部聡 日本水環境学会年会講演集 54th 2020年
• 水中光合成による酸化鉄ナノ粒子の作製と異なる光源下での形態

  ZHANG Lihua, 沖中憲之, 渡辺精一, 岡本一将 材料とプロセス(CD-ROM) 32 (2) 2019年
• 水中結晶光合成法における光の効果と表面パターニング応用

  水野潤一, JEEM Melbert, 高橋優樹, 渡辺精一 日本金属学会講演概要(CD-ROM) 164th 2019年
• PEEMを用いたZnOナノロッドの電界放出特性評価

  河本雅弥, 工藤雅嗣, 水野潤一, JEEM Melbert, 渡辺精一, 朝倉清高 応用物理学会秋季学術講演会講演予稿集(CD-ROM) 80th 2019年
• 水中結晶光合成によるZnOナノロッドの作製と光・電子特性の評価

  JEEM Melbert, FUJIOKA Masaya, WATANABE Seiichi, NISHII Junji 応用物理学会秋季学術講演会講演予稿集(CD-ROM) 80th 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
• 水中結晶光合成法を用いた表面パターニングと光・電子特性評価

  水野潤一, 平岩健聖, JEEM Melbert, 高橋優樹, 渡辺精一, 渡辺精一 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
• 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
• ガルバニック効果を用いた水中結晶光合成による発光性ZnO-金属ヘテロ構造体の作製

  平岩健聖, 高橋優樹, JEEM Melbert, 渡辺精一 日本鉄鋼協会日本金属学会両支部合同サマーセッション概要集 2018 2018年
• ガルバニック効果を用いた水中結晶光合成による発光性ZnO-金属ヘテロ構造体の作製

  平岩健聖, 水野潤一, 高橋優樹, JEEM Melbert, 渡辺精一 日本顕微鏡学会北海道支部学術講演会講演要旨集 2018 2018年
• ZnOナノロッドの光電特性の制御およびSTEM-VEELSによるそれらの評価

  JEEM Melbert, WATANABE Seiichi 日本顕微鏡学会北海道支部学術講演会講演要旨集 2018 2018年
• 水中結晶光合成における光の役割と表面パターニング応用

  水野潤一, JEEM Melbert, 高橋優樹, 渡辺精一 日本金属学会講演概要(CD-ROM) 163rd 2018年
• ガルバニック水中結晶光合成法による光機能デバイス作製

  高橋優樹, 平岩健聖, JEEM Melbert, 張麗華, 渡辺精一 日本金属学会講演概要(CD-ROM) 163rd 2018年
• グリーン応用のための水中結晶光合成によるナノ鉄水酸化物の創製

  高井大, 張麗華, 岡本一将, 沖中憲之, 渡辺精一 材料とプロセス(CD-ROM) 30 (2) 2017年
• ZnOナノロッド光電気特性の調整及びSTEM-VEELSによるその評価

  JEEM Melbert, WATANABE Seiichi 日本顕微鏡学会北海道支部学術講演会講演要旨集 2017 2017年
• 亜鉛表面における酸化物ナノロッド微結晶作製のための水中光合成の光化学

  ZHANG Lihua, JEEM Melbert, OKAMOTO Kazumasa, WATANABE Seiichi 日本金属学会講演概要(CD-ROM) 161st 2017年
• 水中結晶光合成法による鉄酸化物・水酸化物のナノ結晶作製

  高井大, 西野史香, メルバート ジーム, 張麗華, 岡本一将, 沖中憲之, 渡辺精一 日本金属学会講演概要(CD-ROM) 159th 2016年
• レーザー照射によるFePt規則合金薄膜表面の不規則化

  吉田裕, 谷津茂男, 渡辺精一, 山内啓, 柴野純一 X線材料強度に関するシンポジウム講演論文集 50th 2016年
• 水中結晶光合成法による酸化銅ナノ表面構造体の創製

  西野史香, JEEM Melbert, ZHANG Lihua, 岡本一将, 渡辺精一 表面技術協会講演大会講演要旨集 134th 2016年
• 水中結晶光合成法による酸化銅表面ナノ構造の形成機構

  西野史香, JEEM Melbert, 西山賢, 張麗華, 岡本一将, 渡辺精一 日本金属学会講演概要(CD-ROM) 158th 2016年
• 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
• 水中結晶光合成法による酸化銅表面ナノ構造化

  西野史香, JEEM Melbert, 張麗華, 岡本一将, 渡辺精一 日本鉄鋼協会日本金属学会両支部合同冬季講演大会概要集 2015 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 [査読無し][通常論文]
  
• 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 [査読無し][通常論文]
  
• 特集「顕微鏡法による材料開発のための微細構造研究最前線(8)-照射効果の解明と耐照射材料および新素材開発をめざして-」の企画にあたって

  阿部 弘亨, 荒河 一渡, 佐藤 学, 佐藤 裕樹, 谷脇 雅文, 外山 健, 永井 康介, 武藤 俊介, 安田 和弘, 保田 英洋, 義家 敏正, 若井 栄一, 渡辺 精一, 渡辺 英雄 まてりあ : 日本金属学会会報 47 (12) 597 -597 2008年12月01日
• イオン注入を利用した対応粒界原子構造制御

  坂口 紀史, 渡辺 精一, 木下 博嗣, 市野瀬 英喜 まてりあ : 日本金属学会会報 47 (12) 638 -638 2008年12月01日
• 'Innovative Nanoscale Approach to Dynamic Studies of Materials' 会議報告

  新井 正敏, 渡辺 精一, 西口 規彦 應用物理 75 (4) 477 -477 2006年04月10日
• 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][通常論文]
  
• 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][通常論文]
  
• 超高圧電子顕微鏡による照射場格子揺らぎ解析

  渡辺 精一 顕微鏡 40 (1) 59 -62 2005年03月31日
• 特集「電子顕微鏡法による材料開発のための微細構造研究最前線 (5)-若手研究者特集-」企画にあたって

  大貫 惣明, 渡辺 精一, 進藤 大輔, 古屋 一夫, 宝野 和博, 幾原 雄一, 黒田 光太郎, 武藤 俊介, 平山 司, 乾 晴行, 森 博太郎, 弘津 禎彦, 仲井 清眞, 友清 芳二, 松村 晶, 桑野 範之 まてりあ 44 (12) 957 -957 2005年 [査読無し][通常論文]
  
• Mo/Siナノ多層膜の電子線照射誘起非晶質化

  大貫 惣明, 佐久間 大祐, 渡辺 精一, 石野 雅彦 まてりあ : 日本金属学会会報 42 (12) 904 -904 2003年12月20日 [査読無し][通常論文]
  
• イオン照射したFe-Cr系合金の欠陥形成に及ぼすHeとHの複合効果

  田中典幸, 岡桂一朗, 山下真一郎, 須田孝徳, 渡辺精一, 大貫惣明, 若井栄一 日本金属学会講演概要 132nd 2003年
• He照射したフェライト鋼の衝撃特性変化

  岡桂一朗, 田中典幸, 須田孝徳, 渡辺精一, 大貫惣明, 若井栄一 日本金属学会講演概要 132nd 2003年
• トリプルイオン照射によるFe-Cr合金とODSフェライト鋼の欠陥形成

  田中典幸, 岡桂一朗, 山下真一郎, 須田孝徳, 渡辺精一, 大貫惣明, 若井栄一 日本金属学会講演概要 133rd 2003年
• HVEMおよびFEG-TEMによる照射誘起粒界偏析の評価

  坂口紀史, 渡辺精一, 高橋平七郎 電子顕微鏡法の実践と応用写真集，日本金属学会 124 2003年 [査読有り][通常論文]
  
• New model on radiation-induced segregation at various grain boundaries including low sigma coincidence boundaries

  N. Sakaguchi, S. Watanabe, H. Takahashi Proceedings of 2003 Symposium on Advanced Research of Energy Technology 279 -284 2003年 [査読無し][通常論文]
  
• 非平衡開放系の材料科学--ゆらぎとパターン化利用によるナノ材料創製にむけて (<特集>第3回21世紀の境界領域研究を考えるシンポジウム)

  渡辺 精一 バウンダリ- 17 (8) 5 -9 2001年08月
• Formation process and stability of radiation-induced non-equilibrium phase in silicon

  M. Takeda, T. Suda, S. Watanabe, S. Ohnuki, H. Abe JAERI-Review 2001-39 (2001) TIARA Annual Report 2000 2001年 [査読無し][通常論文]
  
• Dynamics of grain boundary movement by in-situ irradiation using atomic-resolution HVEM

  N Sakaguchi, S Watanabe, T Shibayama, H Kinoshita, H Takahashi PRICM 4: FORTH PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING, VOLS I AND II 1485 -1487 2001年 [査読無し][通常論文]
   

  We investigated the irradiation-induced grain boundary migration (RIGM) in an austenitic Fe-Cr-Ni alloy during electron irradiation using by atomic-resolution HVEM (AR-HVEM). It was observed that the shape of a grain boundary had changed to facet-like structure from the straight grain boundary due to the boundary movement during the irradiation, and remarkable solute redistribution was induced near the migrated boundary interface. The dynamical behavior of the RIGM was also observed by in-situ irradiation using AR-HVEM.
• イオンビーム照射による異相界面構造と局部的濃度の変化

  大貫 惣明, 有元 史子, 武田 光博, 渡辺 精一, 高橋 平七郎 電子顕微鏡 35 103 -103 2000年05月01日 [査読無し][通常論文]
  
• TiNiにおける応力誘起微細構造変化

  葉石 靖之, 渡辺 精一, 須田 孝徳, 小池 拓人, 大貫 惣明, 高橋 平七郎, 桐谷 道雄 電子顕微鏡 35 104 -104 2000年05月01日 [査読無し][通常論文]
  
• 29pA23P HYDRGEN ABSORPTION AND ITS EFFECTS ON MICROSTRUCTURE AND TENSILE PROPERTY OF V-Cr-Ti ALLOYS :

  Torres P., 青柳 克明, 須田 孝徳, 渡辺 精一, 大貫 惣明 プラズマ・核融合学会年会予稿集 (17) 171 -171 2000年 [査読無し][通常論文]
  
• FE-TEMによる照射誘起偏析の測定

  渡辺 精一, 高橋 平七郎 まてりあ : 日本金属学会会報 37 (5) 378 -378 1998年05月20日
• NiTiのクラック先端での応力誘起非晶質化

  大貫 惣明, 戸澤 孝平, 松川 義孝, 渡辺 精一, 高橋 平七郎 まてりあ : 日本金属学会会報 37 (5) 372 -372 1998年05月20日 [査読無し][通常論文]
  
• Composition changes and dislocation evolution near grain boundary under HVEM electron irradiation

  N. Sakaguchi, S. Watanabe, H. Takahashi New Direction in Transmission Electron Microscopy and Nano-Characterization of Materials 289 -294 1998年 [査読無し][通常論文]
  
• Effect of additional minor element on radiation-induced segregation in austenitic stainless steel

  N. Sakaguchi, S. Watanabe, H. Takahashi Proceedings of the 1998 International Symposium on Advanced Energy Technology 639 -642 1998年 [査読無し][通常論文]
  
• Excess Defect Diffusion during Annealing in Ion-Implanted Semiconductor

  M. Nakamura, S. Watanabe, N. Sakaguchi, M. Kimura, H. Takahashi Proceedings of the 1997 International Symposium on Advanced Energy Technology 287 -290 1997年 [査読無し][通常論文]
  
• Theoretical study of radiation-induced grain boundary segregation accompanied surface segregation

  N. Sakaguchi, S. Watanabe, H. Kinoshita, H. Takahashi Proceedings of the 4th Japan/China Symposium on Materials for Advanced Energy Systems and Fission and Fusion Engineering 235 -238 1997年 [査読無し][通常論文]
  
• Effect of Crystal Orientation on Grain Boundary Migration and Radiation-Induced Segregation

  N. Hashimoto, S. Watanabe, H. Takahashi Interface Science and Materials Interconnection Proc. of JIMIS-8 383 -386 1996年 [査読有り][通常論文]
  
• Radiation-induced segregation and dislocation evolution near grain boundary in austenitic stainless steel

  S. Watanabe, N. Sakaguchi, H. Takahashi Proceedings of International Conference on Microstructures and Functions of Materials 253 -256 1996年 [査読無し][通常論文]
  

特許

• WO2020-059171:機能水の製造方法及び機能水生成器  2020年03月26日

  足立 修一郎, 北川 雅規, 渡辺 精一, 張 麗華, 村上 俊太郎, ▲高▼橋 優樹  昭和電工マテリアルズ株式会社, 国立大学法人北海道大学  202103009587190697
• WO2019-151508:ナノ結晶膜の製造方法  2019年08月08日

  足立 修一郎, 北川 雅規, 渡辺 精一, ジェーム メルバート, ▲高▼橋 優樹, 水野 潤一  昭和電工マテリアルズ株式会社, 国立大学法人北海道大学  202103014466892108
• 特開2019-134117:光電変換方法、及び光電変換デバイス  2019年08月08日

  足立 修一郎, 北川 雅規, 渡辺 精一, ジェーム メルバート, 高▼橋 優樹, 平岩 健聖  日立化成株式会社, 国立大学法人北海道大学  201903017522168770
• 特許第6493568号:合金部材、該合金部材の製造方法、および該合金部材を用いた製造物  

  藤枝 正, 広田 守, 桑原 孝介, 青田 欣也, 加藤 隆彦, 千葉 晶彦, 小泉 雄一郎, 山中 謙太, 渡辺 精一  日立金属株式会社  201903005875414725
• 特開2018-124211:水素の検知方法、及び水素検知デバイス  2018年08月09日

  足立 修一郎, 北川 雅規, 渡辺 精一, 村上 俊太郎  日立化成株式会社, 国立大学法人北海道大学  201803019053610925
• WO2018-043348:水素ガスの製造方法、及び鋼の製造方法  2018年03月08日

  足立 修一郎, 北川 雅規, 渡辺 精一, 張 麗華, 沖中 憲之, 高井 大  日立化成株式会社, 国立大学法人北海道大学  201903003592355070
• WO2018-043351:ナノ結晶の製造方法、及び鋼の製造方法  2018年03月08日

  足立 修一郎, 北川 雅規, 渡辺 精一, 張 麗華, 沖中 憲之, 高井 大  日立化成株式会社, 国立大学法人北海道大学  201903008712488038
• WO2017-138191:合金部材、該合金部材の製造方法、および該合金部材を用いた製造物  2017年08月17日

  藤枝 正, 広田 守, 桑原 孝介, 青田 欣也, 加藤 隆彦, 千葉 晶彦, 小泉 雄一郎, 山中 謙太, 渡辺 精一  日立金属株式会社  201903012224107243
• 特許第5978650号:鉄鋼材料の表面処理方法  2016年08月05日

  名越 正泰, 佐藤 馨, 渡辺 精一, 吉田 壮貴  JFEスチール株式会社  201603000510461690
• 特許第5891845号:表面処理鋼板の製造方法  2016年03月04日

  馬場 和彦, 名越 正泰, 大塚 真司, 渡辺 精一, 吉田 壮貴  JFEスチール株式会社  201603000377469039
• 特許第5874437号:亜鉛めっき鋼板の製造方法及び亜鉛めっき鋼板  2016年01月29日

  名越 正泰, 馬場 和彦, 野呂 寿人, 渡辺 精一, 吉田 壮貴  JFEスチール株式会社  201603009516097114
• 特許第5835455号:金属材料の表面処理方法  2015年11月13日

  名越 正泰, 佐藤 馨, 馬場 和彦, 野呂 寿人, 渡辺 精一, 吉田 壮貴  JFEスチール株式会社  201603006205222846
• 特許第5817907号:金属材料、金属材料の製造方法、金属材料を基材とした撥水材料の製造方法、金属材料の製造装置、および金属材料の製造方法  2015年10月09日

  名越 正泰, 佐藤 馨, 野呂 寿人, 馬場 和彦, 渡辺 精一, 吉田 壮貴  JFEスチール株式会社  201503002016756764
• 特許第5797125号:3次元表面構造を有する炭素材料  2015年08月28日

  加藤 隆彦, 吉田 誠人, 足立 修一郎, 住谷 圭二, 渡辺 精一  株式会社日立製作所  201503005928938331
• 特許第5696447号:表面処理金属材料の製造方法  2015年02月20日

  名越 正泰, 佐藤 馨, 渡辺 精一, 吉田 壮貴  JFEスチール株式会社  201503066845263543
• 特許第5674285号:レーザー誘起表面ナノ配列構造の作製方法及びそれを用いて作製したデバイス構造  2015年01月09日

  加藤 隆彦, 渡辺 精一, 谷津 茂男, 萱島 知, 西口 規彦, 三澤 弘明, 朝倉 清高  株式会社日立製作所  201503098763728849
• 特開2014-145105:ナノピラー及びその形成方法並びに当該ナノピラーを用いた接合材料、電池、炭酸ガス回収・貯留装置及び電力変換機器用モジュール  2014年08月14日

  加藤 隆彦, 渡辺 精一, 岩崎 富生, 宝蔵寺 裕之  株式会社日立製作所  201403023804776325
• 特許第5569259号:表面改質された導電性材料の製造方法  2014年07月04日

  名越 正泰, 佐藤 馨, 渡辺 精一, 吉田 壮貴  JFEスチール株式会社  201403088927634759
• 特許第5474936号:Cu−Al−Co系合金の電極・配線を具備した電子部品及びCu−Al−Co系合金の電極・配線用材料ならびにそれを用いた電極・配線用ペースト材料  2014年02月14日

  加藤 隆彦, 内藤 孝, 山本 浩貴, 青柳 拓也, 渡辺 精一, 三浦 誠司, 坂口 紀史, 青島 一貴, 大久保 賢二  株式会社日立製作所  201403043265443342
• 特開2013-173978:亜鉛めっき鋼板の製造方法及び亜鉛めっき鋼板  2013年09月05日

  名越 正泰, 馬場 和彦, 野呂 寿人, 渡辺 精一, 吉田 壮貴  JFEスチール株式会社  201303008842750635
• 特開2013-173977:金属材料の表面処理方法および金属材料  2013年09月05日

  名越 正泰, 佐藤 馨, 渡辺 精一, 吉田 壮貴  JFEスチール株式会社  201303016516320267
• 特開2013-173979:表面処理鋼板の製造方法  2013年09月05日

  馬場 和彦, 名越 正泰, 大塚 真司, 渡辺 精一, 吉田 壮貴  JFEスチール株式会社  201303067731958446
• WO2013-125658:金属材料、表面処理方法及び装置  2013年08月29日

  名越 正泰, 佐藤 馨, 野呂 寿人, 馬場 和彦, 渡辺 精一, 吉田 壮貴  JFEスチール株式会社  201503001305883980
• WO2013-125657:金属材料の表面処理方法、および金属材料  2013年08月29日

  名越 正泰, 佐藤 馨, 馬場 和彦, 野呂 寿人, 渡辺 精一, 吉田 壮貴  JFEスチール株式会社  201503001487256714
• 特開2013-159519:3次元表面構造を有する炭素材料  2013年08月19日

  加藤 隆彦, 吉田 誠人, 足立 修一郎, 住谷 圭二, 渡辺 精一  株式会社日立製作所  201303047793945013
• 特許第5254811号:導体微粒子を製造する方法  2013年04月26日

  渡辺 精一, 鳥谷部 祐, 谷津 茂男, 柴山 環樹, 水野 忠彦  環境エンジニアリング株式会社  201303009226200636
• 特許第5205577号:粒界制御型耐照射性SUS316相当鋼およびその製造方法  2013年03月01日

  山下 真一郎, 矢野 康英, 渡辺 精一, 坂口 紀史, 谷川 隆亮, 粉川 博之, 宮城 雅徳, 佐藤 信也  独立行政法人日本原子力研究開発機構, 国立大学法人北海道大学, 国立大学法人東北大学  201303001474036469
• 特開2012-111998:表面処理金属材料の製造方法  2012年06月14日

  名越 正泰, 佐藤 馨, 渡辺 精一, 吉田 壮貴  JFEスチール株式会社, 国立大学法人北海道大学  201203085475163482
• 特開2012-045672:レーザー誘起表面層を有する3次元構造体及びその製造方法  2012年03月08日

  加藤 隆彦, 渡辺 精一, 吉田 裕  株式会社日立製作所, 国立大学法人北海道大学  201203002348897008
• 特開2012-045489:表面改質された導電性材料の製造方法  2012年03月08日

  名越 正泰, 佐藤 馨, 渡辺 精一, 吉田 壮貴  JFEスチール株式会社  201203084496267605
• 特開2010-269435:レーザー誘起表面ナノ配列構造の作製方法及びそれを用いて作製したデバイス構造  2010年12月02日

  加藤 隆彦, 渡辺 精一, 谷津 茂男, 萱島 知, 西口 規彦, 三澤 弘明, 朝倉 清高  株式会社日立製作所, 国立大学法人北海道大学  201003078597366944
• 特開2010-242193:機能性ステンレスナノボール及びステンレスナノボール触媒  2010年10月28日

  渡辺 精一, 谷津 茂男, 坂口 紀史, 高橋 正志, 佐々木 仁  国立大学法人北海道大学, 合同会社札幌NBT  201003084898770872
• 特開2009-185313:粒界制御型耐照射性SUS316相当鋼およびその製造方法  2009年08月20日

  山下 真一郎, 矢野 康英, 渡辺 精一, 坂口 紀史, 谷川 隆亮, 粉川 博之, 宮城 雅徳, 佐藤 信也  独立行政法人 日本原子力研究開発機構, 渡辺 精一, 粉川 博之  200903066471976136
• 特開2007-277613:細孔を有する金多孔質体およびその製造方法  2007年10月25日

  三浦 誠司, 渡辺 精一, 須田 孝徳, 毛利 哲夫, 大久保 賢二  国立大学法人 北海道大学  200903011949560047
• EP2008710394:導体微粒子を製造する方法  

  渡辺精一, 鳥谷部裕, 谷津茂男, 柴山環樹, 水野忠彦
• US08343253:導体微粒子を製造する方法  

  渡辺精一, 鳥谷部裕, 谷津茂男, 柴山環樹, 水野忠彦
• US08790549:Ｃｕ−Ａｌ−Ｃｏ系合金の電極・配線を具備した電子部品  

  加藤隆彦, 内藤孝, 山本浩貴, 青柳拓也, 渡辺精一, 三浦誠司, 坂口紀史, 青島一貴, 大久保賢二
• WO/2010/137297:レーザー誘起表面ナノ配列構造の作製方法及びそれを用いて作製したデバイス構造  

  加藤隆彦, 渡辺精一, 谷津茂男, 萱島 知, 西口規彦, 三澤弘明, 朝倉清高
• WO/2012/026359:レーザー誘起表面層を有する３次元構造体及びその製造方法  

  加藤隆彦, 渡辺精一, 吉田 裕
• US09034148:表面改質された導電性材料の製造方法  

  名越正泰, 佐藤 馨, 渡辺精一, 吉田壮貴
• EP2011843018:表面処理金属材料の製造方法  

  名越正泰, 佐藤 馨, 渡辺精一, 吉田壮貴
• US13988848:表面処理金属材料の製造方法  

  名越正泰, 佐藤 馨, 渡辺精一, 吉田壮貴
• WO/2014/119421:ナノピラー及びその形成方法並びに当該ナノピラーを用いた接合材料、電池、炭酸ガス回収・貯留装置及び電力変換機器用モジュール  

  加藤隆彦, 渡辺精一, 岩崎富生, 宝蔵寺裕之
• WO/2018/043351:ナノ結晶の製造方法、及び鋼の製造方法  

  足立修一郎, 北川雅規, 渡辺精一, 張麗華, 沖中憲之, 高井大
• WO/2018/043348:水素ガスの製造方法、及び鋼の製造方法  

  足立修一郎, 北川雅規, 渡辺精一, 張麗華, 沖中憲之, 高井大
• WO/2017/138191:合金部材、該合金部材の製造方法、および該合金部材を用いた製造物  

  藤枝 正, 広田 守, 桑原 孝介, 青田 欣也, 加藤 隆彦, 千葉 晶彦, 小泉 雄一郎, 山中 謙太, 渡辺 精一
• WO/2018/135144:水素ガスの製造方法、及び半導体デバイスの製造方法  

  足立修一郎, 北川雅規, 渡辺精一, ジーム メルバート, 西野史香, 高橋優樹
• WO/2018/135145:水素の検知方法、及び水素検知デバイス  

  足立修一郎, 北川雅規, 渡辺精一, ジーム メルバート, 西野史香, 高橋優樹

受賞

• 2023年09月 日本金属学会 第４１回 優秀ポスター賞
   マルチ元素ナノ酸化物の⼀括⽔中結晶光合成 

  受賞者: 林 學毅、張 麗華、渡辺精一
• 2022年11月 日本顕微鏡学会 北海道支部 令和4年度日本顕微鏡学会北海道支部、北海道支部長賞（優秀ポスター賞）
   機能性モリブデン-タングステンナノ酸化物複合材料の水中光合成 

  受賞者: 林 學毅;Melbert Jeem;張 麗華;渡辺 精一
• 2022年09月 日本金属学会 日本金属学会 第39回優秀ポスター賞
   水中光照射下におけるドーピング誘起光学的相転移 

  受賞者: 早野 彩夏、Melbert Jeem 、林 學毅 、張 麗華、渡辺 精一
• 2022年07月 物質・デバイス領域共同研究拠点 第4回 物質・デバイス共同研究賞
   光・ 電子デバイ ス応用に向けたガルバニック水中結晶光合成法による表面ナノパターン作製 

  受賞者: 髙橋 優樹;塚村 順平;村上 俊太郎;渡辺 精一;張 麗華;岡本 一将
• 2021年09月 日本金属学会 日本金属学会 第３７回 優秀ポスター賞
   鉄腐食を利用したヒドロゲル中アクアイオン拡散係数定量評価 

  受賞者: 高井 智史、村上 俊太郎、張 麗華、渡辺精一
• 2021年09月 日本金属学会 日本金属学会 第３７回 優秀ポスター賞
   G-SPSCを用いた欠陥制御による色調表面パターニング 

  受賞者: 塚村 順平、高橋 優樹、張 麗華、ジェーム メルバート、岡本 一将、渡辺精一
• 2021年08月 The Water and Environment Technology Conference Online 2021 Excellent Presentation Award
   Nanostructured ZnO/CuO Composite Photocatalyst for Valuable Products Synthesis 

  受賞者: Ryosuke MATSUO;Chhunhong KAING;Yuki TAKAHASHI;Seiichi WATANABE;SatoshiOKABE
• 2020年09月 日本金属学会 (第35回)優秀ポスター賞
   異種金属接触水中光合成法による機能性ヘテロナノ構造体の作製 

  受賞者: 高橋 優樹;ジェーム メルバート;渡辺 精一
• 2019年03月 日本金属学会 第３２回 優秀ポスター賞
   水中結晶光合成法における光の効果と表面パターニング応用 

  受賞者: 水野潤一;Melbert JEEM;高橋 優樹;渡辺精一
• 2017年12月 日本顕微鏡学会北海道支部 Excellent Presentation Award
   Tuning ZnO nanorods opto-electrical properties and their evaluation by STEM-VEELS 

  受賞者: Melbert JEEM;Seiichi Watanabe
• 2016年03月 日本金属学会 第２６回 優秀ポスター賞
   水中結晶光合成法による酸化銅表面ナノ構造の形成機構 

  受賞者: 西野史香;Melbert JEEM;西山賢;張麗華;岡本一将;渡辺精一
• 2015年12月 日本顕微鏡学会北海道支部 奨励賞
   イオン液体中ZnO ナノ結晶のレーザー照射誘起光腐食のTEM 内その場観察 

  受賞者: 大藤功将;石岡準也;小暮一馬;河口楓;五十嵐直也;メルバートジェーム;谷津茂男;渡辺精一;柴山環樹
• 2013年09月 日本磁気学会学 学術奨励賞
   ナノ秒パルスレーザー照射したFe52Al48表面の磁気特性 

  受賞者: 海住 英生;吉田 裕;大澤 和也;渡辺 精一;近藤 憲治;石橋 晃;吉見 享 祐
• 2011年12月 日本顕微鏡学会北海道支部 奨励賞
   HRTEM および EELS に基づくシリコン対応粒界の原子構造・電子状態評価 

  受賞者: 三宅牧人;坂口紀史;渡辺精一
• 2010年09月 日本金属学会 第１５回 優秀ポスター賞
   HRTEM および EELS によるΣ3 対応粒界ファセットの原子構造・電子状態評価 

  受賞者: 三宅牧人;坂口紀史;渡辺精一
• 2010年09月 日本金属学会 第１５回 優秀ポスター賞-2
   シリコン表面レーザー誘起ナノドットの微細構造解析 

  受賞者: 吉田 裕;渡辺精一;谷津茂男;坂口紀史;柴山環樹;大久保賢二;高橋平七郎;加藤隆彦;川合將義
• 2010年07月 日本金属学会北海道支部 夏季サマーセッション優秀ポスター賞
   シリコンΣ3 対応粒界ファセットにおける電子状態のEELS による評価 

  受賞者: 三宅牧人;坂口紀史;渡辺精一
• 2009年09月 日本金属学会 第１３回 優秀ポスター賞
   W/SiC接合界面に形成した反応相の微細構造解析とクラック進展のその場観察 

  受賞者: 松尾元一郎;荻津健;柴山環樹;浜田弘一;渡辺精一;岸本弘立;香山晃
• 2009年09月 日本金属学会 第１３回 優秀ポスター賞-2
   液中プラズマ放電によるナノ粒子の生成 

  受賞者: 齊藤元貴;吉田壮貴;谷津茂男;渡辺精一;秋山友宏
• 2009年03月 日本金属学会 第１２回 優秀ポスター賞-2
   Pd-Zn合金中に内部酸化で析出したZnO粒子の形態と結晶構造 

  受賞者: 渡辺圭;鈴木義典;坂口紀史;渡辺精一
• 2009年03月 日本金属学会 第１２回 優秀ポスター賞
   オーステナイト系ステンレス鋼における照射効果ならびに腐食挙動に及ぼす粒界性質依存性 

  受賞者: 遠藤正樹;坂口紀史;木下博嗣;渡辺精一;粉川博之;山下真一郎;矢野康英;川合將義
• 2007年03月 日本金属学会 第８回 優秀ポスター賞
   イオン照射したシリコン多結晶粒界の高分解能電子顕微鏡解析 

  受賞者: 落合章裕;米塚健大郎;小門礼;坂口紀史;渡辺精一;市野瀬英喜
• 2007年03月 日本金属学会 第65回 功績賞 （物性部門）
   『量子エネルギービーム照射による開放系の材料研究と強非平衡性に基づく材料創製』 

  受賞者: 渡辺精一
• 2007年03月 プラズマ応用科学会 論文賞
   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 

  受賞者: 東本英哲;山内啓;柴山環樹;渡辺精一;黒川一哉;成田敏夫
• 2007年 Meritorious Award, Japan Institute of Metals
  
• 1997年03月 平成9年度風戸奨励賞
   『マルチビーム超高圧電子顕微鏡を用いた照射下微細欠陥クラスター形成挙動』 

  受賞者: 渡辺精一
• 1993年03月 日本金属学会 第3回日本金属学会奨励賞・物性部門
   『金属中の電子輸送に関する研究』 

  受賞者: 渡辺精一
• 1993年 1993 Young Scientist Award (Div. of Solid State Physics), Japan Institute of Metals1995 Monbusho Visiting Fellowship, Japan Society for the Promotion of Science (Japanese Government)
  

共同研究・競争的資金等の研究課題

• 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

  日本学術振興会：科学研究費助成事業 基盤研究(A)

  研究期間 : 2020年04月 -2023年03月 

  代表者 : 渡辺 精一
• 非生物・生物ハイブリッド人工光合成システムの構築：持続可能な酢酸生成拠点の創出

  日本学術振興会：科学研究費助成事業

  研究期間 : 2020年04月 -2022年03月 

  代表者 : 岡部 聡, 渡辺 精一, 佐藤 久

   

  本研究の目的は、CO2と水を原料とし太陽光エネルギー（可視光）と廃水をエネルギー源として、常温常圧、中性条件下で酢酸（2炭素化合物）を生産可能なバイオ‐光電気化学太陽電池（Bio-PEC)ハイブリッドシステムを構築することである。そのために必要なCuOナノワイヤー表面にZnOナノロッドを付加した3次元ナノ構造を持つZnO/CuO複合体を作成することに成功した。また、その電気化学的特性（水素生成速度や電流密度）は、既往の類似する三次元ナノ構造を有するZnO/CuOの値の約3倍であった。これにより、効率の良いBio-PECシステムの構築の可能性が示された。
• 非生物・生物ハイブリッド人工光合成システムの構築：持続可能な酢酸生成拠点の創出

  日本学術振興会：科学研究費助成事業 挑戦的研究(開拓)

  研究期間 : 2019年06月 -2022年03月 

  代表者 : 岡部 聡, 渡辺 精一, 佐藤 久
• 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

  日本学術振興会：科学研究費助成事業 基盤研究(A)

  研究期間 : 2012年04月 -2016年03月 

  代表者 : 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。
• 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

  日本学術振興会：科学研究費助成事業 基盤研究(A)

  研究期間 : 2012年04月 -2015年03月 

  代表者 : 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．
• 液中グロー放電の高時間分解その場解析によるナノ粒子・ナノ表面化機構解明

  文部科学省：科学研究費補助金(新学術領域研究(研究領域提案型))

  研究期間 : 2012年 -2013年 

  代表者 : 渡辺 精一

   

  本研究では, 液中陰極グロー放電による弱電離プラズマ中を流れる電流が陰極材料を母材とするナノ粒子を作り出すメカニズムを解明することを最終目的としている。 平成24年度は放電時の電流ノイズを高時間分解で計測でき同時に電極近傍の発光を画像記録できる実験システムを整備した上で, 先ず電流ノイズの高時間分解データを取得し, 電流ノイズの頻度分布解析・パワースペクトル解析を行った。次に電流測定と同時に液中プラズマ画像を得て画像輝度の時間変化に対するスペクトル解析を行った。さらに, 陰極上に残された放電痕の電子顕微鏡像に対し、画像解析, パワースペクトル解析を行った。 その結果，パワースペクトル密度のべき乗数αは電気分解領域ではほぼ0で, 電極表面の液相が気相に変わる遷移域では急激に減少し0から-2へと変化すること, またプラズマ領域では-2に近い値を保持することが判った。則ち, 両極間に印加する電圧の上昇と共に陰極周囲の物質相が液相から気相へ更に弱電離プラズマ相へと変わる過程を電流変動成分のスペクトル解析からべき乗数αを用いて統一的に表現可能なことを明らかにした。画像輝度と電流との同時測定からは，両者のパワースペクトル密度が周波数に対し同じべき乗依存性をもつことがわかった。 また，陰極表面に残された放電痕画像のパワースペクトル解析から放電痕分布が等方的であること,パワースペクトル密度が波数のべき乗(-2乗)分布をもつこと、および放電痕サイズ分布を対数プロットしたグラフから放電痕数がサイズのべき乗(-2乗)分布を持つことを確認した。これらの結果はナノ粒子が産み出される機構が間欠的なアバランシェ放電ないし電流集中に起因するも全体的には時空間にわたる自己相似性を有することを示唆するものであり, 今後より高範囲・高精度な測定による検証が行われる必要がある。
• 液中グロー放電法による世界最小ステンレス合金ナノボールの創製

  文部科学省：科学研究費補助金(挑戦的萌芽研究)

  研究期間 : 2011年 -2012年 

  代表者 : 渡辺 精一, 谷津 茂男

   

  ステンレス合金のナノボール(ナノメートルサイズの球状粒子)に関して,申請者らが開発した液中グロー放電法を利用して極小化ナノボールを作製するための基礎技術を確立し,最小のステンレス合金ナノボールを得た。また、このステンレス合金ナノボールがデバイス化への応用面の期待ができる光触媒効果を有することを見出した。
• 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

  文部科学省：科学研究費補助金(基盤研究(A))

  研究期間 : 2009年 -2011年 

  代表者 : 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。
• 液中プラズマ放電による合金ナノボールの創製と機能性発現のための物性測定

  文部科学省：科学研究費補助金(基盤研究(A))

  研究期間 : 2008年 -2011年 

  代表者 : 渡辺 精一, 保田 英洋, 庭瀬 敬右, 西口 規彦, 大笹 憲一, 三浦 誠司, 谷津 茂男, 安住 和久, 坂口 紀史, 黒川 一哉, 秋山 友宏

   

  本研究は, 申請代表者らが開発したグロー放電による液中プラズマ利用の新規金属ナノボールの製法を活用し,各種金属と合金材料を出発原料としたナノボール創製研究と機能物性発現の物性解析評価,および作製したナノ粒子を利用した新規機能デバイス材料の開発基礎のための材料設計を行なった.
• 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

  文部科学省：科学研究費補助金(基盤研究(S))

  研究期間 : 2007年 -2010年 

  代表者 : 川合 將義, 菊地 賢司, 川崎 亮, 義家 敏正, 渡辺 精一, 栗下 裕明, 粉川 博之, 菊地 賢司, 川崎 亮, 長谷川 晃, 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。
• 超高速一方向共晶凝固と共析分解・球状化熱処理による高靭性耐熱ニオブ基合金の実現

  文部科学省：科学研究費補助金(基盤研究(A))

  研究期間 : 2007年 -2009年 

  代表者 : 三浦 誠司, 木村 好里, 毛利 哲夫, 渡辺 精一, 大笹 憲一, 三島 良直, 滝沢 聡, 木村 好里

   

  凝固速度1500mm/hで高速一方向凝固したNb-18.1Si-1.5Zr合金を熱処理したところ、所期の金属組織が得られた。Nb相の3Dイメージングより、高温材料として有利な巨大サイズNb結晶粒実現が示唆された。この試料は室温で2%の圧縮塑性変形能を示し、50kgでダイヤモンド圧子を押し込んでも、脆い強化相Nb_5Si_3の破壊は周囲の延性Nb母相が抑制する。高温変形特性を決めるNb相の高温強度を向上させるMo、W添加は、Ta添加と組み合わせると組織制御と高強度化を同時に達成できる。
• 強加工による形状記億合金の非晶質/ナノ結晶化とその相変態機構の解明

  日本学術振興会：科学研究費助成事業

  研究期間 : 2005年 -2006年 

  代表者 : 土谷 浩一, 田渕 正幸, 渡辺 精一, 戸高 義一, 梅本 実

   

  TiNi系形状記憶合金は優れた形状記憶・超弾性特性を示し,携帯電話のアンテナ等様々な分野で応用されてきた。特に最近は低侵襲性医療技術の発展に伴い,ガイドワイヤー,ステント等の医療デバイスへの応用が急速に拡大している。TiNiはまた,強加工により固相状態で非晶質化またはナノ結晶化することが知られてきた。その原因としては,転位密度の上昇による弾性エネルギーの増加が重要であると指摘されてきた。本研究では冷間圧延(CR),ショットピーニング(SP),高圧ねじり加工(HPT),冷間線引などの強加工による,非晶質化ノナノ結晶化したTiNiについて,TEMによる組織観察の結果に基づき,その非晶質化機構について考察した。 その結果,CR, HPTによる非晶質過程は類似しており,加工前の状態がマルテンサイト相(B19'相)であっても加工によりB2相に逆変態し,さらに加工を加えることにより非晶質相へと変化することが明らかになった。また非晶質化の過程で現れるラメラ構造の詳細について調べ,非晶質層をはさんで同じほぼ方位のB2構造層からできていることが明らかになった。このことはマルテンサイト変態の際に格子不変変形として導入される双晶境界が転位の蓄積場所となり優先的に非晶質化することを示唆する。また比較の為に様々な組成のZr・Cu系合金についてHPT加工による非晶質化について調べたところ,マルテンサイト変態を起こすZr_<50>Cu_<50>合金のみで非晶質化することが明らかになった。これはマルテンサイト組織特有の微細な双晶組織が転位の蓄積を促進し非晶質化を起こすことを示す。 また,非晶質・ナノ結晶TiNi合金の医療デバイスへの応用を視野に,冷間線引で強加工したTiNiについてもその組織と特性を評価した。その結果減面率70%まで線引きしたTiNiで非晶質領域が観察された。また線引き材,線引き加工後低温熱処理した線材について引張り試験により応力歪み曲線を測定したところ,条件によって約2GPaの破断強度と約5%の擬弾性回復ひずみを示すことが明らかになった。
• 衝撃と放射線に強い高機能材料の創製

  文部科学省：科学研究費補助金(基盤研究(A))

  研究期間 : 2004年 -2006年 

  代表者 : 川合 將義, 菊地 賢司, 神山 崇, 山村 力, 川崎 亮, 義家 敏正, 原 信義, 粉川 博之, 二川 正敏, 栗下 裕明, 渡辺 精一, 菊地 賢司

   

  核破砕場と宇宙を対象として、耐衝撃特性と耐放射線損傷の強い材料の開発研究を行った。主要な結果は以下の通りである。(1)核破砕中性子源の固体ターゲット材用に炭化チタン分散型の高靭性タングステンをメカニカルアロイング法により開発し、タングステン材料では世界で初めて超塑性を実現できた。(2)ターゲット等の構造材として重要なステンレス鋼について、耐放射線特性を向上させるため、加工熱処理により多数の焼鈍双晶を導入することによって低エネルギー構造粒界(対応粒界)を高頻度かつ均一分散させた粒界制御したステンレス鋼を創出した。(3)タングステンの腐食と放射化の問題を解決すべく、イオンプレーティングでのPVD法および2重ビーム法、電気化学法によってタングステン板の周囲に安定してCrNの薄膜層を形成できた。(4)水銀ターゲット容器壁やビーム窓のピッティング対策として、高速度ビデオによってバブル形成の機構を明らかにするとともに、(5)ステンレス鋼の表面改質効果を調べ、とりわけ窒化および侵炭法の複合的な表面処理によって、ピッテング損傷の進展を一桁送らせることができた。(6)宇宙材料として、アルミニウム-チタン系の高靭性複合セラミックスを開発した。(7)宇宙塵が衝突した際の亀裂伝播を防止する機能を付与したニオブ-アルミ系の合金を開発した。上記の材料について機械試験や腐食試験を行い、所定の機能を持っていることを評価した。(8)MW級の固体ターゲット用にHIP法(熱間静水圧加圧法)によって開発したタンタル被覆のタングステン薄板を高温からの急冷試験を行い、破損が生じず、冷却水の喪失事故時に対応可能なことが確認できた。(9)陽電子消滅法により、粒界制御の工程がステンレス鋼に損傷を与えない事、材料試験炉での中性子照射損傷効果を明確にした。(10)超高圧電子顕微鏡の電子線および陽子ビームを用いた照射シミューション実験にて、粒界制御材が普通材に比べて放射線損傷に強そうだというデータ、さらにニオブ-アルミ系の合金が期待した中間金属を形成し、亀裂伝播の防止機能を持っていそうだという結果を得た。(11)さらに材料の放射線損傷試験として、スイスの核破砕中性子源施設に送って放射した材料の照射後試験を行った。その結果、日本のステンレス鋼JPCAが、3dpa以上の照射でも伸び特性を持っている事、生成ガスの保持量を明らかにできた。以上で、損傷研究の基礎的な手法が得られた。今後、損傷データの一層の採取と理論的研究を通じてさらなる材料開発研究に展開したい。
• アモルファス合金中の多様体原子クラスター形成と1/f揺らぎ発現機構解明

  文部科学省：科学研究費補助金(基盤研究(C))

  研究期間 : 2003年 -2005年 

  代表者 : 渡辺 精一

   

  研究の目的本研究では、エネルギービーム照射およびアニール過程におけるアモルファス合金中の多様体クラスターの遷移挙動を明らかにし、揺らぎ特性(b:0〜2)を制御した機能性アモルファス材料の開発設計を行うために1/f^α型揺らぎ応答発現の機構解明を行うことを目的とする。研究実施事項:《非晶質(アモルファス)化過程の原子レベル構造評価》高分解能型超高圧電子顕微鏡(1.25MV:分解能0.117nm)による電子線照射誘起アモルファス化過程の原子レベルその場観察を行いデジタル録画。画像処理解析による画像解析(FFTパターンと画像マスク処理、多様体原子クラスター情報の抽出)。照射温度等を変え同様実験。アモルファス化過程における長距離秩序の消滅と短範囲秩序クラスター形成とその時間発展を詳細調査。今年度は、特に揺らぎの原因となる原子オーダーリングの構造変化について調査を行なった。《照射過程と非晶質化各段階でのアニールの分子動力学計算》分子動力学計算は、原子挿入法(EAM)をもちいて既に開発したEAMポテンシャルを用いて、フレンケル欠陥を逐次ランダムに所定照射量になるまで導入する方法を用いる。固有クラスターはボロノイ多面体解析により調査。また原子緩和を計算中に行ない、最後に体積やエネルギー等の系のプロパティーを評価する。各照射量段階での動径分布関数、原子間結合長変化と体積、トータルポテンシャルエネルギー増加評価,電子顕微鏡画像計算、FFT2次元画像処理、電子回折パターン像解析と回折強度分布定量評価。揺らぎの多変量相関性の評価を行なった。
• 時空間マルチスケール構造解析に基づく非平衡系材料科学とナノ材料創製 i)非平衡断熱系および非平衡開放系：弱非平衡から強非平衡までの材料統計科学 ii)材料中の照射効果および機能物性に関する微細構造解析研究

  研究期間 : 2004年
• イオンミキシング法による水素吸蔵合金の表層ナノ構造の改質

  日本学術振興会：科学研究費助成事業

  研究期間 : 2000年 -2000年 

  代表者 : 渡辺 精一, 兜森 俊樹, 谷脇 雅文, 須田 孝徳

   

  イオンビームを水素吸蔵合金の表面改質に利用した場合、結晶構造の変化、多量の格子欠陥、注入された水素による水素化物の核形成などが期待され、さらには種々の溶質元素をミキシングすることによって、新しい機能を持った合金開発の可能性がある。本研究ではイオン注入やイオンミキシングにより、長寿命化(耐劣化や耐被毒)および活性化の制御などを目指した表面ナノ構造の改質を行うことを目的とした。 (1)ZrCoおよびZrNi:高温顕微鏡によるその場観察(水素圧1atm、反応温度150℃に200℃)を使用し、水素物形成過程の定量化を試みた。(1)ZrCo:ZrCoでは水素イオン注入による水素化物の成長促進の効果が認められなかった。イオンミキシングの効果については、溶質元素をCoにした場合に顕著であり、成長速度は2倍から3倍に増加することができた。水素化物形成に必要な活性化エネルギーは、未処理の場合が40kJ/mol、イオンミキシングの場合が20〜30kJ/mol程度となった。(2)ZrNi:ZrNiは水素イオン注入をしなければ、水素化が起こらない。イオン注入量が1X1016H2+/cm^2の場合、成長速度が大きくまた水素化開始までの潜伏期も大幅に短くなった。 (2)TiFe:TiFeは未処理の場合、反応温度400℃、水素圧10MPaにおいても水素化が起こらない。しかし、水素イオン注入(3.6X1016H2+/cm^2)の場合7MPa、アルゴンイオン注入(5X1015Ar+/cm^2)の場合5MPa程度から水素化が開始する。また、LaNi5を溶質としたイオンミキシングを行うと、1X1015Ar+/cm^2では、水素圧1MPaで水素化が起こることがわかった。以上の結果から、イオン注入およびイオンミキジングによる初期水素化挙動に対する効果は、広範に認められることが明らかとなった。
• 電子線照射による非平衡下粒界応答反応現象の非対称性に関する研究

  文部科学省：科学研究費補助金(奨励研究(A))

  研究期間 : 1999年 -2000年 

  代表者 : 渡辺 精一

   

  オーステナイト系ステンレス鋼における照射誘起偏析の速度論による定量化・モデリング照射誘起粒界偏析および促進拡散に関し速度論によるモデル化をおこない、定量化に成功した。照射誘起の粒界応答反応、特に照射誘起による偏析が粒界性質(方位とS値)によってどの様に依存性を調べることができ、傾角粒界の場合には明確な依存性があることを確認した。また、粒界性格を境界条件として取り入れた速度論による定量化にも成功した。照射誘起粒界応答反応の粒界性質依存性の実験的確認と定量化モデリングに成功することができた。これらの研究成果をふまえ今後は、各種合金(オーステナイトステンレス鋼、フェライト鋼、ODSフェライト鋼、および結合形式の異なる化合物系合金)における非平衡粒界応答効果に関して電子線照射その場観察実験を行い原子レベルの欠陥形成初期過程から巨視的現象(本研究では数マイクロメータ程度を対象とする)に至るまでの現象の総合的解明を行う。現在まで行ってきた速度論手法はそのままでは原子レベルの実験解析には不向きであるため、離散型の計算手法を取り込みこれと速度論を結合させ、原子レベルから巨視的レベルまでの空間的・時間的マルチスケーリングモデリングによる総合的定量化支援プログラミングを行なう。原子レベルから巨視的レベルまでの空間的・時間的マルチスケーリングモデリングによる総合的定量化支援プログラミングを行なう。当該研究は従来型の照射効果の研究に対して、原子レベル動的観察、マルチスケーリングによる定量化といった新たな視点からの息吹を注入するものであり、非平衡粒界挙動を利用した材料創製に貢献するところ大であると考えられる。
• イオン注入による水素吸蔵合金の表層ナノ構造の改質

  日本学術振興会：科学研究費助成事業

  研究期間 : 1998年 -1998年 

  代表者 : 大貫 惣明, 兜森 俊樹, 谷脇 雅文, 須田 孝徳, 渡辺 精一

   

  水素吸蔵合金の水素化特性を改善する新しい試みとして,イオン注入による表層改質を実施した。吸蔵合金にイオン注入を適用した場合,(1)スパッタリングによる表層清浄化,(2)任意元素の非平衡濃度注入,(3)多量の格子欠陥による拡散促進などの効果が期待できる。本研究の目的は,水素化特性に及ぼすイオン注入の影響を調査し,表層ナノ構造との関係を明確にすることである。 今年度は,ZrNiの初期活性化について検討した。試料にイオン注入領域と未注入領域を形成し,試料表面の水素化による変化を観察した。また,表層ナノ構造はTEMにより観察した。イオン注入は,水素,ヘリウム,アルゴンイオンを100keV,室温にて行い,注入量を5X10^<15>〜1X10^<17>ions/cm^2とした。 1.水素イオン注入の影響:注入領域において多数のクラックの発生が見られ,クラックは未注入領域との境界付近で進行が止まった。すなわち,水素イオン注入は合金の初期活性化を明確に促進することが判明した。その原因は,表面近傍において非平衡に濃化した水素が水素化物を形成したため,水素の拡散が促進したものと考えている。2.アルゴンイオン注入の影響二水素イオン注入とは逆に,初期活性を明確に抑制することが判明した。TEM観察から,注入したアルゴンはバブルを形成していない。そのため,表面近傍で高濃度に分散された状態であることが推察される。すなわち,分散したアルゴンが水素の拡散パスを塞いだことが原因であると考えている。3.ヘリウムイオン注入の影響:水素及びアルゴンイオン注入のような明確な影響が現れなかった。しかし,現在の条件より注入量を増加させると,アルゴンと同様な現象が起こると推定できる。 今後は,イオンミキシングを使った合金改質に進展する予定である。
• 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

  日本学術振興会：科学研究費助成事業

  研究期間 : 1997年 -1998年 

  代表者 : 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。
• イオン注入法による接合界面の組成・構造変化と接合特性に関する研究

  日本学術振興会：科学研究費助成事業

  研究期間 : 1995年 -1996年 

  代表者 : 高橋 平七郎, 渡辺 精一, 木下 博嗣, 黒川 一哉, 大貫 惣明

   

  1.MoSi_2/Ti/グラファイト系接合:超高温材料の接合を可能にすると共に表面を改質する目的から、Ti箔を介在させMoSi_2とグラファイトを放電プラズマにより接合実験し、Ti薄膜を接合界面に介在させると界面でのSiC形成を抑制でき、曲げ特性、耐酸性共にの優れた特性の接合ができた。 2.イオン注入過程での界面組織変化・制御:セラミックス(Al_2O_3),半導体Siに室温で種々のイオンを注入し,ステンレス鋼の粒界界面及び表面構造変化を調べた。各材料においてイオン注入過程で二次欠陥が発達した。中でも、Al_2O_3では注入量の増加に伴い、粒界・界面から非晶質化した。 3.Mo/Si異種元素材料の界面制御:Mo/Si_2層物質を用いイオンミキシング実験を行い、2層界面の接合界面変化を観察すると共に、相互拡散過程を検討した。イオン照射過程で導入された点欠陥により、低温度で両元素の拡散が促進され、さらにイオンによる押し込み効果による照射促進拡散が起こりこれを利用し低温接合が可能である。 4.Si/酸化膜界面構造と欠陥組織:Bイオンを酸化膜/Siの2層界面近傍に注入後の瞬間焼鈍した場合の欠陥分布とそれに及ぼす界面効果を検討した。その結果、界面に発生する応力場が欠陥の界面への拡散流入を促進させ、2次欠陥形成が抑制されることが認められ、界面はイオン注入で導入された点欠陥の優先的なシンクサイトであり、界面接合に対し重要な役割を有することが示唆された。 以上、超高温材料の接合には耐熱金属を介在させプラズマ放電法により短時間に接合ができると共にイオン照射法により低温接合が可能である。今後、イオン注入法とプラズマ放電法を併用することにより広範囲の特殊材料の接合が可能である。
• 核融合炉用低放射化制御材料に関する基礎研究

  日本学術振興会：科学研究費助成事業

  研究期間 : 1993年 -1995年 

  代表者 : 高橋 平七郎, GELLES David, GARNER Frank, 渡部 精一, 黒川 一哉, 大貫 惣明, EDWARDS D.J., 木下 博嗣, EDWADS D.J., DAVID S.Gell, FRANK A.Garn

   

  今年度は過去3年間の結果の考察と追加実験研究を行った。その結果、低放射化材料の開発に際し検討されるべき事項として、以下のようにまとめられた。 1)Fe-Cr-Ni系鋼について、照射下で粒界におけるNiの顕著な偏析とCr濃度の低下を同定し、偏析と同時に粒界移動が起こり、これら現象は照射点欠陥の粒界への流入に支配されることを中性子照射および電子線照射実験から明らかにした。また、高速中性子照射により約50dpaで数%のスエリングが生ずることを観察した。これらのことから、改良型316ステンレス鋼は、国際熱核融合実験炉(ITER)のように短期的には照射量(30dpa程度)が少なく、放射化レベルも低い場合には低スエリングのため核融合炉構造材として使用可能である。 2)各種低放射化オーステナイトFe-Cr-Mn系鋼を200℃で中性子照射後、機械的性質と合金組成の関係を調べ、Fe-10%Cr-(20-25)%Mn-3%AlおよびFe-10%Cr-30%Mn鋼が良好な性質を示し、また、Al添加により照射下における相安定性が向上することを明らかにした。また、Fe-Cr-Mn系改良AMCR合金鋼を高速中性子で420℃、520℃及び600℃で32-36dpaまで照射後、密度測定からスエリングを評価した結果、Fe-12%Cr-11%Mn-0.5%Si-1.4%Wに0.3%Cを添加した鋼が耐スエリング特性に優れているが、相安定性に欠けることを確認し、炭素添加がある程度スエリング抑制および相安定に効果的であることが判明した。以上の結果から、Fe-Cr-Mn系高マンガン鋼の場合は、電磁場、強度等の核融合炉の環境を考慮すると魅力ある材料である。しかし、第一壁材料の様に500℃以上の高温度に曝せれる場合は、相安定性の観点から不適と判断され、核融合、炉のバックアップ材など200℃以下の低温度での構造材料としてのみ利用可能と評価された。 3)低放射化Fe-(9-12)Cr-2W鋼をFFTFで高速中性子照射後の機械的性質に及ぼすB、Y、Al添加の効果を調べ、スエリング非常に低く100dpaでも問題にならない程度であった。MoやMbに代わってWやV元素の添加により降伏強度や抗張力は十分維持できるが、DBTTが照射で上昇することが明らかにされた。従って、オーステナイト系ステンレス鋼に代わる第一壁材料あるいはブランケット構造材として低放射化フェライト鋼が実証炉等中期的には有望であるがDBTTを改善する必要する必要がある。これまでの実験から、機械的性質、耐照射特性を考慮するとFe-(9-12)%Cr-2%W鋼が最適と判断される。ただし、核変換で生成するヘリウムの靭性-脆性遷移温度(DETT)上昇が大きいためそのヘリウム効果の解決が重要であることが指摘された。 4)低放射化材料として将来最も期待されている、バナジウム及びバナジウム合金の照射化の合金組成変化として、核変換(n,r)による組成変化が中性子照射により起こることを見い出し、特にバナジウムではCrおよびTiが生成することをEDS分析からはじめて明らかにした。現在、V-4Cr-4Ti合金が耐照射特性に優れている低放射化合金として有望視されてが、長期間の使用中に核変換でCr新たに生成されるため合金成分が変化し、その結果、材料特性が大きく影響される可能性が有ることが明かになり、今後この核変換元素の効果の更なる研究が必要であることが指摘された。 5)照射現象に関する基礎的知見として、(a)Vと同様に核変換により、WがReさらにOs元素に変化する事が同定され、低放射化フェライト鋼に添加されているWがこの核変換でその性質が大きく影響されること、(b)電子線/Heイオン同時照射実験から、Heは原子空孔と強く相互作用し、空孔型積層欠陥四面体がボイド核生成サイトとなる。また、TiおよびPの微量添加によりスエリング、および粒界偏析が抑制されるが、ボイド数密度は増大すること、さらに(c)ステンレス鋼の粒界は照射中移動と濃度変化が起こり、粒界移動はエピタキシアル的に成長に起因する事を明らかにした。
• 過剰格子欠陥存在下での粒界近傍の溶質拡散ダイナミクス

  文部科学省：科学研究費補助金(奨励研究(A))

  研究期間 : 1994年 -1994年 

  代表者 : 渡辺 精一

   

  高速増殖炉、軽水炉などの核分裂型原子炉や、将来実用化が期待される核融合炉における照射損傷は、炉材料の使用にあたり主要な問題点である。特に相安定性に関わる照射誘起偏析現象は、結晶粒界の溶質の偏析を通して照射脆化に結び付き、またボイド表面での偏析、母相での溶質濃度の変化からボイド形成に影響する可能性が指摘されている。現在までいくつかの偏析モデルが提唱されてきたが、実用材料を念頭とした照射研究に応用された例は少ない。本研究では計算コードを開発し、ステンレス鋼の粒界近傍における過剰点欠陥の容質拡散として照射誘起偏析の定量的予測を行なった。具体的には、本研究室所有の超電圧電子顕微鏡による1MeV電子線照射をおこない材料中(Fe-Cr-Ni)の2次欠陥の密度測定、粒界近傍の濃度分布分析、拡散係数等必要な物性値を見積もる。i)拡散方程式による計算照射下での連立した拡散方程式をたて、これを解くことにより各場所での元素の濃度の経時変化を調べる。この時各元素とさらに点欠陥(原子空孔と格子間原子)の濃度も併せて調べる。非線形の連立微分方程式を数値計算により解く。(逆)カ-ケンドール効果を取り入れた連立速度式によりFe-Cr-Ni合金の粒界近傍での照射誘起偏析のモデル計算を行った。本計算結果は超高圧電子顕微鏡(1MeV)を用いたシュミレーション実験より得られた照射量、温度、損傷速度の変化に伴う誘起偏析の変化と、濃度分布を概ね説明している。中性子照射などの高エネルギー粒子による照射でも、照射誘起偏析によりステンレス鋼の粒子近傍(<〜10^<-1>μm)でNiの濃度とCrの枯渇が起こると考えられる。より確実な相関則を得るためには,実験等による各種パラメータの確認が必要であることを明らかにした。

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