研究者データベース

研究者情報

マスター

アカウント(マスター)

  • 氏名

    柴山 環樹(シバヤマ タマキ), シバヤマ タマキ

所属(マスター)

  • 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 量子エネルギー変換材料分野

所属(マスター)

  • 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 量子エネルギー変換材料分野

独自項目

syllabus

  • 2020, 大学院共通授業科目(一般科目):自然科学・応用科学, Inter-Graduate School Classes(General Subject):Natural and Applied Sciences, 修士課程, 大学院共通科目, small angle X-ray scattering, neutron scattering, high voltage electron microscope, metals, amorphous, ceramics, composites, defects
  • 2020, 量子ビーム材料物性特論, Advanced Quantum Beam Materials, 修士課程, 工学院, 量子ビーム 材料物性 エネルギー材料 材料構造解析
  • 2020, 量子ビーム材料物性特論, Advanced Quantum Beam Materials, 博士後期課程, 工学院, 量子ビーム 材料物性 エネルギー材料 材料構造解析
  • 2020, 機械知能工学入門, Introduction to Mechanical and Intelligent System Engineering, 学士課程, 工学部, 機械知能工学科の学問体系、機械知能工学科の研究応用例、基礎科目群、専門科目群
  • 2020, 工業英語演習, Exercise on Technical English, 学士課程, 工学部, 工業英語、英文読解、英作文、英会話、プレゼンテーション、討論
  • 2020, ラボラトリーセミナー, Laboratory Seminar, 学士課程, 工学部, 実習・実験、観察方法、計測技術、材料、流体、制御、バイオ、熱、放射線、物理化学
  • 2020, 材料科学, Material Science, 学士課程, 工学部, 原子構造、結晶構造、エネルギーバンド、欠陥、拡散、状態図、材料環境
  • 2020, 一般教育演習(フレッシュマンセミナー), Freshman Seminar, 学士課程, 全学教育, 量子ビーム、プラズマ、触媒、ナノ材料

timetable

  • 修士課程, 工学院, 2020, Advanced Quantum Beam Materials(量子ビーム材料物性E)
  • 博士後期課程, 工学院, 2020, Advanced Quantum Beam Materials(量子ビーム材料物性E)

researchmap

プロフィール情報

学位

  • 博士(工学)(北海道大学)

プロフィール情報

  • 柴山, シバヤマ
  • 環樹, タマキ
  • ID各種

    200901022455393479

対象リソース

業績リスト

研究キーワード

  • 半導体ナノ粒子   イオン照射効果   ナノ粒子   オペランド観察   量子ビーム分析   液体電子顕微鏡法   イオン液体   カソードルミネッセンス   ラマン分光   表面プラズモン   ナノ構造材料   微細構造解析   先進電子顕微鏡法   低放射化原子力材料   微細構造と機械特性相関   SiC/SiC複合材料   

研究分野

  • ナノテク・材料 / 構造材料、機能材料
  • ナノテク・材料 / 無機材料、物性
  • ものづくり技術(機械・電気電子・化学工学) / 計測工学
  • エネルギー / 原子力工学
  • ナノテク・材料 / 金属材料物性
  • エネルギー / 核融合学
  • ナノテク・材料 / 複合材料、界面

経歴

  • 2015年04月 - 現在 北海道大学 大学院工学研究院 教授
  • 2007年04月 - 2015年03月 北海道大学 大学院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 准教授
  • 2004年04月 - 2007年03月 北海道大学 エネルギー変換マテリアル工学研究センター 准教授
  • 2002年10月 - 2004年03月 北海道大学 大学院工学研究科量子エネルギー工学専攻瞬間強力パルス状放射線発生装置研究室 助教授
  • 2002年 - 2004年 Associate Professor
  • 1998年01月 - 2002年09月 北海道大学 エネルギー先端工学研究センター極限材料工学部門 助手
  • 1998年 - 2002年 Research Associate
  • 1992年04月 - 1997年12月 東北大学 金属材料研究所材料照射工学研究部門 助手
  • 1992年 - 1997年 Research Associate

委員歴

  • 2019年06月 - 2021年05月   日本顕微鏡学会   北海道支部長
  • 2020年04月 - 2021年03月   日本原子力学会   材料部会長
  • 2018年06月 - 2019年05月   日本原子力学会   北海道支部長
  • 2006年 - 2009年   日本電子顕微鏡学会   北海道支部役員   日本電子顕微鏡学会
  • 2006年 - 2008年   日本金属学会   分科会委員   日本金属学会

論文

  • Yuki Nakagawa, Tomoharu Kimura, Takao Ohki, Shigehito Isobe, Tamaki Shibayama
    SOLID STATE IONICS 365 2021年07月 [査読有り][通常論文]
     
    The effect of mechanical milling on the lithium-ion conductivity of lithium alanate (LiAlH4) is investigated. Although pristine LiAlH4 is a poor ion conductor in its highly crystalline state, short-time mechanical milling for 0.1-2 h is shown to significantly improve the conductivity. Hand-milling treatment in an argon-filled glove box is also shown to improve the conductivity. The activation energy (E-a) for ion conduction of milled LiAlH4 is similar to 0.70 eV, which is attributed to Li-ion site vacancy-mediated conduction. However, the Ea of pristine LiAlH4 shows a large value of 0.84 eV. The Li-7, Li-6, Al-27 nuclear magnetic resonance and infrared spectra suggest that surface Li hydroxide species would exhibit Li-ion conduction in pristine LiAlH4. Thus, the milling treatment can eliminate the effect of surface hydroxide species and increase the vacancy concentration at the Li-ion site of inner LiAlH4 grains, which results in the enhancement of the conductivity.
  • Subing Yang, Yuki Nakagawa, Minako Kondo, Tamaki Shibayama
    ACTA MATERIALIA 211 2021年06月 [査読有り][通常論文]
     
    Irradiation-induced anisotropic swelling in hexagonal alpha-SiC is known to degrade the mechanical properties of SiC; however, the associated physical mechanism and microstructural process remain insufficiently understood. In this study, an anisotropic swelling condition where the surface normal direction was allowed to freely expand with constraint in the lateral direction was introduced in 4H-SiC using selected-area He+ irradiation, and the internal defect distribution was investigated using transmission electron microscopy (TEM) and advanced scanning TEM. The defect distribution was compared to that in non-selected-area He+-irradiated 4H-SiC and electron-irradiated TEM-foil 4H-SiC. An anisotropic defect distribution was observed in the selected-area He+-ion-irradiated 4H-SiC, with interstitial defects preferentially redistributed in the surface normal direction ([0 004]) and negative volume defects (such as vacancies and/or carbon antisite defects) dominantly located in the lateral directions ([11 (2) over bar0] and [10 (1) over bar0]). This anisotropy of the defect distribution was substantially lower in the non-selected-area He+-irradiated and electron-irradiated samples. The stress condition in the three samples was also measured and analyzed. In the selected-area He+-irradiated 4H-SiC, compressive stress was introduced in the lateral directions (([10 (1) over bar0] and [11 (2) over bar0])), with little stress introduced in the surface normal direction ([0 004]); this stress condition was introduced at the beginning of ion irradiation. The compressive stress likely inhibits the formation of interstitial defects in the lateral directions, enhancing the anisotropy of the defect distribution in SiC. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
  • Keita Shinzato, Yuki Nakagawa, So Hamamoto, Yuya Hayashi, Hiroki Miyaoka, Shigehito Isobe, Tamaki Shibayama, Norio Ogita, Takayuki Ichikawa
    Chemical Communications 56 53 7237 - 7240 2020年05月 [査読有り][通常論文]
     

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

  • Yuki Nakagawa, Tomoharu Kimura, Shigehito Isobe, Tamaki Shibayama
    The Journal of Physical Chemistry C 124 19 10398 - 10407 2020年05月 [査読有り][通常論文]
  • Subing Yang, Yuki Nakagawa, Minako Kondo, Tamaki Shibayama
    Journal of Applied Physics 127 175106  2020年05月 [査読有り][通常論文]
  • 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 [査読有り][通常論文]
     
    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.
  • Yang Subing, Tokunaga Sakiko, Kondo Minako, Nakagawa Yuki, Shibayama Tamaki
    APPLIED SURFACE SCIENCE 500 2020年01月15日 [査読有り][通常論文]
  • 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]
  • Hayashi Kyoko, Lee Jung-Bum, Atsumi Kinya, Kanazashi Mana, Shibayama Tamaki, Okamoto Kazumasa, Kawahara Toshio, Hayashi Toshimitsu
    PLOS ONE 14 7 2019年07月16日 [査読有り][通常論文]
  • Bing-Sheng Li, Zhi-Guang Wang, Tie-Long Shen, Kong-Fang Wei, Yan-Bin Sheng, Tamakai Shibayama, Xi-Rui Lu, An-Li Xiong
    Chinese Physics Letters 36 4 046104 - 046104 2019年04月 [査読有り][通常論文]
  • Wei Xiaoya, Lan Si, Wu Zhenduo, Ohnuma Masato, Shibayama Tamaki, Watanabe Seiichi, Zhou Jie, Lu Zhaoping, Ren Yang, Wang Xun-Li
    INTERMETALLICS 105 173 - 178 2019年02月 [査読有り][通常論文]
  • 中性子増倍材料としてのベリリウム及びその合金
    Masaru Nakamichi, Jae-HwanKim, Makoto M Nakamura, SHIBAYAMA Tamaki, Christopher K Dorn, Chakin Vladimir, Dmitry V Bachurin, Christopher Stihl, Pavel V Vladimirov
    Comprehensive Nuclear Materials 2nd edition, Elsevier 1 - 48 2019年 [査読有り][招待有り]
  • Manabu Ishimaru, Tomasz Goryczka, Hiroki Kurata, Kenji Matsuda, Syo Matsumura, Yasukazu Murakami, Katsuhiko Nishimura, Norihito Sakaguchi, Tamaki Shibayama
    Materials Transactions 60 5 674  2019年 [査読有り][通常論文]
  • Takashi Nozawa, Kazumi Ozawa, Chang Ho Park, Joon Soo Park, Akira Kohyama, Akira Hasegawa, Shuhei Nogami, Tatsuya Hinoki, Sosuke Kondo, Toyohiko Yano, Tamaki Shibayama, Bun Tsuchiya, Tatsuo Shikama, Shinji Nagata, Teruya Tanaka, Hirotomo Iwakiri, Yasushi Yamamoto, Satoshi Konishi, Ryuta Kasada, Masatoshi Kondo, Tomoaki Kunugi, Takehiko Yokomine, Yoshitaka Ueki, Nariaki Okubo, Tomitsugu Taguchi, Hiroyasu Tanigawa
    Journal of Nuclear Materials 511 582 - 590 2018年12月01日 [査読有り][通常論文]
     
    © 2018 Elsevier B.V. The R&D on SiC/SiC composites under the broader approach (BA) activities between Japan and the EU for fusion DEMO developed a fundamental database of mechanical (Task-1) and physical/chemical (Task-2) properties, with a primary target of the application of SiC/SiC composites as functional structure to be used in the dual coolant breeding blanket concept. This paper aims to summarize previous 10-years activities of the R&D of Japan and to provide the key deliverables toward the DEMO design. In Task-1, good creep and fatigue durability were first demonstrated. Besides, in-plane and inter-laminar strength anisotropy maps at elevated temperatures were comprehensively identified. In parallel, the irradiation effects of SiC materials were specifically determined as input parameters of the analytical model to provide for the irradiation-induced residual stresses. In Task-2, the apparent dose-dependence of the radiation-induced electrical conductivity and the indicative radiation-induced electrical degradation was identified by various irradiation sources. In addition, good gas confinement was identified. Furthermore, no accelerated corrosion for duration of 3000 h at below 1173 K was first demonstrated. With these achievements, it is suggested that the in-vessel component technology, e.g., material corrosion database development, activated corrosion product evaluation code development, compact module tests for validation of the key functions of the components, technology integration assessment for fusion nuclear tests, etc., should be further developed toward DEMO in near-term.
  • Kishimoto Hirotatsu, Asakura Yuuki, Matano Minoru, Nakazato Naofumi, Park Joon-Soo, Shibayama Tamaki, Fukumoto Masakatsu
    FUSION ENGINEERING AND DESIGN 136 116 - 119 2018年11月 [査読有り][通常論文]
  • Xu Yi, Cheng Junye, Yiu Pak Man, Shan Guangcun, Shibayama Tamaki, Watanabe Seiichi, Ohnuma Masato, Shek Chan-Hung
    NANOSCALE 10 39 18846 - 18856 2018年10月21日 [査読有り][通常論文]
  • H. Hori, M. Takase, M. Takashima, F. Amano, T. Shibayama, B. Ohtani
    CATALYSIS TODAY 300 99 - 111 2018年02月 [査読有り][通常論文]
     
    The mechanism of the formation of flake ball-shaped (FB) bismuth-tungstate (BWO) particles was studied with samples prepared by hydrothermal reactions under standard conditions (tungsten/bismuth ratio of 0.55 in feed; 433 K; 20 h) and other modified conditions, and the structural characteristics of the samples were analyzed by powder X-ray diffraction (composition and crystal structure), field emission-type scanning electron microscopy (FE-SEM) (morphology), focused ion-beam etching followed by FE-SEM (inner void structure), ultrahigh-voltage transmission electron microscopy (inner void structure) and low-voltage scanning electron microscopy with energy-dispersive X-ray spectroscopic analysis (morphology and elemental distribution). Based on the results, a novel two-step mechanism of (1) formation of aqueous bismuth-oxyhydroxide droplets covered by tungstic acid (BOx@HWO) with fluidity and (2) reaction of inner bismuth and outer tungsten components at the BOx@HWO surface to yield BWO flakes is proposed as a one of the most plausible pathways that are consistent with the hollow structure of FB BWO and observations of the products prepared with shorter hydrothermal reaction. Photocatalytic activities of FB BWO samples in relation to their structure were studied.
  • 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.
  • Yuuki Asakura, Hirotatsu Kishimoto, Joon-Soo Park, Naofumi Nakazato, Tamaki Shibayama, Akira Kohyama
    Fusion Engineering and Design 125 484 - 489 2017年12月01日 [査読有り][通常論文]
     
    A SiC/SiC composite is a candidate for the structural material of fusion reactors after Demonstration Power Plant (DEMO). Tungsten will be employed as an armor of SiC/SiC constructed divertor, the developments of fabrication method and optimization of thermal property of them are the important issues. Present research produced W and SiC/SiC clad plates using a diffusion bonding method and tried to investigate the thermal characters of the interphase between W and SiC/SiC composites. The thermal conductivities of W/SiC clad, SiC/SiC and tungsten plates were characterized by a laser flash method at temperatures up to 773 K. The thermal data was approximated by functions and applied as material data to an analysis by finite element method (FEM). The simple FEM model of the divertor suggested that the existence of the interfacial phase with low apparent thermal conductivity of the divertor system under the heat flux exposure of 5 MW/m2 may cause fracture of the system due to thermal stress. The results show the importance of the improvement of the interphase to enhance the thermal properties and the reactor design to reduce thermal flux for the divertor surface.
  • 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.
  • Ruixuan Yu, Tamaki Shibayama, Junya Ishioka, Xuan Meng, Yanhua Lei, Seiichi Watanabe
    Nanotechnology 28 27 275701 - 275701-11 2017年06月09日 [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.
  • Xiaobin Xie, Guanhui Gao, Shendong Kang, Yanhua Lei, Zhengyin Pan, Tamaki Shibayama, Lintao Cai
    NANOTECHNOLOGY 28 24 2017年06月 [査読有り][通常論文]
     
    Being able to. precisely control the morphologies of noble metallic nanostructures is of essential significance for promoting the surface-enhanced Raman scattering (SERS) effect. Herein, we ;demonstrate an overgrowth strategy for synthesizing. Au @ M( M = Au, Ag, Pd, Pt) core-shell heterogeneous nanocrystals with an orientated structural evolution and highly improved properties by using. Au nanorods as seeds. With the same reaction condition system applied, we obtain four well-designed heterostructures with diverse shapes, including Au concave nanocuboids (Au CNs), Au @ Ag crystalizing face central cube nanopeanuts, Au @ Pd porous nanocuboids and Au @ Pt nanotrepangs. Subsequently, the exact overgrowth mechanism of the above heterostructural building blocks is further analysed via the systematic. optimiziation of a series of fabrications. Remarkably, the well-defined Au CNs and Au @ Ag nanopeanuts both exhibit highly promoted SERS activity. We expect to be able to supply a facile strategy for the fabrication of multimetallic heterogeneous nanostructures, exploring the high SERS effect and catalytic activities.
  • 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.
  • 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.
  • 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.
  • 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 035220  2017年03月 [査読有り][通常論文]
  • Tsukasa Torimoto, Yutaro Kamiya, Tatsuya Kameyama, Hiroyasu Nishi, Taro Uematsu, Susumu Kuwabata, Tamaki Shibayama
    ACS APPLIED MATERIALS & INTERFACES 8 40 27151 - 27161 2016年10月 [査読有り][通常論文]
     
    Independently controlling the shape anisotropy and chemical composition of multinary semiconductor particles is important for preparing highly efficient photo catalysts. In this study, we prepared ZnS-AgInS2 solid solution ((AgIn)(x)Zn2(i1-)S2, ZAIS) nanoparticles with well-controlled anisotropic shapes, rod, and rice shapes, by reacting corresponding metal acetates with a mixture of sulfur compounds with different reactivities, elemental sulfur, and 1,3-dibutylthiourea, via a two-step heating-up process. The chemical composition predominantly determined the energy gap of ZAIS particles: the fraction of Zn2+ in rod-shaped particles was tuned by the ratio of metal precursors used in the nanocrystal formation, while postpreparative Zn2+ doping was necessary to increase the Zn2+ fraction in the rice-shaped particles. The photocatalytic H-2 evolution rate with irradiation to ZAIS particles dispersed in an aqueous solution was significantly dependent on the chemical composition in the case of using photocatalyst particles with a constant morphology. In contrast, photocatalytic activity at the optimum ZAIS composition, x of 0.35-0.45, increased with particle morphology in the order of rice (size: ca. 9 X ca. 16 nm) < sphere (diameter: ca. 5.5 run) < rod (size: 4.6 X 27 nm). The highest apparent quantum yield for photocatalytic H-2 evolution was 5.9% for rod-shaped ZAIS particles, being about two times larger than that obtained with spherical particles.
  • Y. H. Lei, R. X. Yu, T. Shibayama, J. Ishioka, S. Watanabe
    Materials Letters 164 1 202 - 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.
  • Shendong Kang, Guanhui Gao, Xiaobin Xie, Tamaki Shibayama, Yanhua Lei, Yan Wang, Lintao Cai
    MATERIALS RESEARCH LETTERS 4 4 212 - 218 2016年 [査読有り][通常論文]
     
    A facile and free surfactant strategy is explored to synthesize Cu-Pt bimetallic nano-heterostructures with dendritic exterior. For comparison, the Cu-Pt coral-like nanoparticles are fabricated by using CTAC as a surfactant. The well-designed Cu-Pt dendritic spherical heterostructures exhibit superior enhanced electrocatalytic activity and stability toward methanol oxidation reaction in alkaline media, compared to the Cu-Pt coral-like nanoparticles and the commercial Pt/C, respectively. The advanced technique for fabricating Cu-Pt dendritic spherical heterostructures could pave a way to pursue low-cost Pt-based catalysts, maintaining highly promoted electrocatalytic performance and durability. [GRAPICS] IMPACT STATEMENT The well-designed Cu-Pt dendritic spherical heterostructures are synthesized without any surfactant, which demonstrate highly promoted electrocatalytic performance and durability toward methanol oxidation reaction.
  • 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.
  • X. Xie, G. Gao, S. Kang, T. Shibayama, Y. Lei, D. Gao, L. Cai
    Advanced Materials 27 37 5573 - 5577 2015年10月 [査読有り][通常論文]
     
    Trimetallic Au/Ag/Pt hetero-nanostructures (AAPHNs) with distinctive, designed morphology are synthesized by galvanic replacement reaction and a site-selective strategy. The three metals present on the surface are shown to act synergistically to enhance the electro-catalytic performance and durability for methanol oxidation. The described structural modification of the nanocomposites increases the range of potential applications to include both the oxygen reduction reaction in fuel cells and photocatalysis of the hydrogen evolution reaction.
  • In-Situ 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]
  • 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.
  • 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).
  • Tsukasa Torimoto, Yasuhiro Ohta, Kazuki Enokida, Daisuke Sugioka, Tatsuya Kameyama, Takahisa Yamamoto, Tamaki Shibayama, Kazuki Yoshii, Tetsuya Tsuda, Susumu Kuwabata
    JOURNAL OF MATERIALS CHEMISTRY A 3 11 6177 - 6186 2015年 [査読有り][通常論文]
     
    The surface coating of metal nanoparticles resulting into core-shell structures is expected to improve the physicochemical properties of the nanoparticle cores without changing their size and shape. Here, we developed a novel strategy to coat Au, AuPd or Pt catalyst cores having average sizes smaller than 2.5 nm, which were pre-synthesized in ionic liquids by corresponding metal sputtering, with an extremely thin In2O3 layer (ca. <1.5 nm) by sputter deposition of indium in a room-temperature ionic liquid. The metal cores of Au or AuPd in core-shell particles exhibited superior stability against heat treatments or during electrocatalytic reactions compared to the corresponding bare metal particles. The In2O3 shell coating considerably enhanced the durability of electrocatalytically active Pt particles (1.2 nm). This sequential metal sputter deposition of different metals in ionic liquids will considerably contribute to the exploitation of key nanostructured components for next-generation energy-conversion systems.
  • 異種原子注入 講座・電子顕微鏡による材料研究
    柴山 環樹, 渡辺 精一
    軽金属 64 12 659 - 662 2014年12月 [査読有り][招待有り]
  • Ikuo Ioka, Tamaki Shibayama
    JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY 51 5 735 - 736 2014年05月 [査読有り][招待有り]
  • Ruixuan Yu, Tamaki Shibayama, Xuan Meng, Shinya Takayanagi, Shigeo Yatsu, Junya Ishioka, Seiichi Watanabe
    JOURNAL OF APPLIED PHYSICS 115 14 143104  2014年04月 [査読有り][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.
  • Ruixuan Yu, Tamaki Shibayama, Xuan Meng, Shinya Takayanagi, Yutaka Yoshida, Shigeo Yatsu, Seiichi Watanabe
    APPLIED SURFACE SCIENCE 289 274 - 280 2014年01月 [査読有り][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.
  • 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 [査読有り][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.
  • 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.
  • 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.
  • メン シュアン, 柴山 環樹, ウ, エイケン, 高柳 伸也, 渡辺 精一
    Journal of Applied Physics 114 5 054308  2013年08月 [査読有り][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.
  • 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.
  • N. Sakaguchi, Y. Ohguchi, T. Shibayama, S. Watanabe, H. Kinoshita
    JOURNAL OF 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.
  • M. Nakamichi, J. H. Kim, K. Munakata, T. Shibayama, M. Miyamoto
    Journal of Nuclear Materials 442 1-3 SUPPL.1 S465 - S471 2013年 [査読有り][通常論文]
     
    Advanced neutron multipliers with low swelling and high stability at high temperatures are desired for pebble bed blankets of demonstration fusion power (DEMO) reactors. Beryllium intermetallic compounds (beryllides) are the most promising advanced neutron multipliers. The plasma sintering method has been selected as a new synthesis method for beryllides because this method is very simple and easy to control. Plasma sintering is a non-conventional consolidation process. The plasma sintering results in starting-powder particle surface activation that enhances sinterability and reduces high temperature exposure. The sintering properties of beryllides were evaluated. Results show that intermetallic beryllide compounds such as Be12Ti, Be 17Ti2 and Be2Ti can be directly synthesized by the plasma sintering method from mixed elemental powders of Be and Ti at a temperature below the melting point. The preliminary characterization of plasma-sintered Be-Ti beryllide was carried out including examination of oxidation with water vapor, microstructure analysis, irradiation effects, and deuterium retention compared with beryllium (Be) metal. The preliminary characterization revealed that the plasma-sintered Be-Ti beryllide sample performs well as a neutron multiplier. This beryllide sample has better oxidation resistance, higher radiation resistance and lower deuterium retention than Be metal. © 2013 Elsevier B.V. All rights reserved.
  • Kishimoto, H., Ono, T., Sakasegawa, H., Tanigawa, H., Ando, M., Shibayama, T., Kohno, Y., Kohyama, A.
    Journal of Nuclear Materials 442 1-3 SUPPL.1 S546 - S551 2013年 [査読有り][通常論文]
  • Tetsuya Sasamura, Takaaki Osaki, Tatsuya Kameyama, Tamaki Shibayama, Akihiko Kudo, Susumu Kuwabata, Tsukasa Torimoto
    CHEMISTRY LETTERS 41 9 1009 - 1011 2012年09月 [査読有り][通常論文]
     
    Ag2ZnSnS4 (AZTS) nanoparticles were successfully synthesized at relatively low temperature via thermal reaction of corresponding metal acetates and a sulfur source in a hot oleylamine solution, the purity of the particles being dependent on the amount of metal acetates and the reaction temperature. The obtained pure AZTS particles with size of ca. 15 nm exhibited photoresponse with visible light irradiation similar to that of n-type semiconductors.
  • B. S. Li, C. H. Zhang, H. H. Zhang, T. Shibayama, Y. T. Yang
    VACUUM 86 4 452 - 456 2011年11月 [査読有り][通常論文]
     
    Lattice damage and evolution in 6H-SiC under He ion irradiation have been investigated by the combination of Rutherford backscattering in channeling geometry (RBS/C), Raman spectroscopy, UV visible spectroscopy and transmission electron microscopy (TEM). 6H-SiC wafers were irradiated with He ions at a fluence of 3 x 10(16) He(+)cm(-2) at 600 K. Post-irradiation, the samples were annealed in vacuum at different temperatures from 873 K to 1473 K for isochronal annealing (30 min). Thermally annealed He irradiated 6H-SiC exhibited an increase in damage or reverse annealing behavior in the damage peak region. The reverse annealing effect was found due to the nucleation and growth of He bubbles. This finding was consistent with the TEM observation. The thermal annealing brought some recovery of lattice defects and therefore the intensities of Raman peaks increased and the absorption coefficient decreased with increasing annealing temperature. The intensity of Raman peak at 789 cm(-1) as a function of annealing temperature was fitted in terms of a thermally activated process which yielded activation energy of 0.172 +/- 0.003 eV. (C) 2011 Elsevier Ltd. All rights reserved.
  • T. Ito, Y. Yamauchi, T. Hino, T. Shibayama, Y. Nobuta, K. Ezato, S. Suzuki, M. Akiba
    JOURNAL OF NUCLEAR MATERIALS 417 1-3 1147 - 1149 2011年10月 [査読有り][通常論文]
     
    The influence of 50 eV hydrogen ion irradiation on the deuterium retention and desorption behavior in the reduced activation ferritic-martensitic steel F82H was investigated by thermal desorption spectroscopy. The amount of retained deuterium in the hydrogen irradiated F82H was up to 10 times larger than without the hydrogen irradiation. In the F82H irradiated by the low energy hydrogen ions at 300 and 523 K. the desorption peak of deuterium was shifted to lower temperatures than for samples unirradiated or irradiated at 773 K. In the F82H irradiated by hydrogen at 773 K, the amount of retained deuterium decreased compared to materials irradiated at 300 or 523 K. (C) 2011 Elsevier B.V. All rights reserved.
  • Genichiro Matsuo, Tamaki Shibayama, Hirotatsu Kishimoto, Kouichi Hamada, Seiichi Watanabe
    JOURNAL OF NUCLEAR MATERIALS 417 1-3 391 - 394 2011年10月 [査読有り][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.
  • H. Kishimoto, T. Shibayama, K. Shimoda, T. Kobayashi, A. Kohyama
    JOURNAL OF NUCLEAR MATERIALS 417 1-3 387 - 390 2011年10月 [査読有り][通常論文]
     
    The SiC/SiC composites are expected to be employed as structural materials in fusion reactors after DEMO. Tungsten may be used as armor material of divertor to protect from the high temperature heat flux. An advanced SiC/SiC composite, NITE SiC/SiC, has excellent resistance to high stress and temperature, and diffusion and sinter bonding methods using high temperature are able to join SiC/SiC composites. This work evaluates the microstructure of interphases when tungsten is joined to SiC to screen potential bonding techniques. The W/SiC joints were produced by diffusion bonding, sinter bonding and liquid phase sinter bonding methods using the hot-pressing methods. Evaluation by SEM, EPMA, TEM and shear test showed the promise of these bonding methods. (C) 2010 Elsevier B.V. All rights reserved.
  • Y. Yamauchi, D. Oku, T. Hino, T. Shibayama, Y. Nobuta, T. Nagasaka, T. Muroga
    JOURNAL OF NUCLEAR MATERIALS 417 1-3 327 - 329 2011年10月 [査読有り][通常論文]
     
    The effects of the surface oxidation on the helium desorption and retention behaviors of vanadium alloy were investigated. V-4Cr-4Ti alloy, which was thermally oxidized at 873 K for 15 min with 0.05 Pa, was irradiated by helium ions with energy of 5 key at room temperature. Then, the helium desorption and retention behaviors were evaluated using a technique of thermal desorption spectroscopy. The changes in surface structures by the irradiation were also evaluated. Helium desorption behavior in low temperature region were significantly changed by the oxidation. Helium desorption around 700 K became large for the oxidized sample. The amount of retained helium and the blister size in the oxidized sample were smaller than of those in the non-oxidized one. These results indicate that the surface oxidation significantly affects the helium retention and desorption behaviors of the vanadium alloy. (C) 2010 Elsevier B.V. All rights reserved.
  • H. Oka, M. Watanabe, H. Kinoshita, T. Shibayama, N. Hashimoto, S. Ohnuki, S. Yamashita, S. Ohtsuka
    JOURNAL OF NUCLEAR MATERIALS 417 1-3 279 - 282 2011年10月 [査読有り][通常論文]
     
    The oxide dispersion strengthening method was applied to an austenitic stainless steel based on SUS316 by mechanical alloying with additions of minor alloying elements. This ODS austenitic stainless steel was electron-irradiated to investigate the damage structure. Microstructural observation revealed that ODS austenitic stainless steel has a fine distribution of complex oxides. The in situ observation during electron irradiation showed that both dislocation loops and small cavities nucleated at the interface between oxide particles and matrix. In the case of helium implantation, defect clusters also nucleated at the interface. These results suggest that the oxide interface is an effective sink for irradiation-induced point defects and helium atoms. (C) 2010 Elsevier B.V. All rights reserved.
  • Toshimasa Suzuki, Shushi Suzuki, Yousuke Tomita, Ken-ichi Okazaki, Tamaki Shibayama, Susumu Kuwabata, Tsukasa Torimoto
    CHEMISTRY LETTERS 39 10 1072 - 1074 2010年10月 [査読有り][通常論文]
     
    Sputter deposition of transition metals W, Mo, Nb, and Ti into ionic liquids (ILs) produced corresponding metal oxide nanoparticles (NPs) smaller than 6 nm The NPs were obtained in a highly dispersed manner without any additional stabilizing agent in ILs
  • Toshimasa Suzuki, Ken-ichi Okazaki, Shushi Suzuki, Tamaki Shibayama, Susumu Kuwabata, Tsukasa Torimoto
    CHEMISTRY OF MATERIALS 22 18 5209 - 5215 2010年09月 [査読有り][通常論文]
     
    Sputter deposition of indium (In) in ionic liquids (ILs) could produce stable In metal nanoparticles whose surface was covered by an amorphous In2O3 layer to form In/In2O3 core/shell particles. The size of the In core was tunable from ca. 8 to 20 nm by selecting the kind of IL, whereas the shell thickness of In2O3 was almost constant at ca. 1.9 nm. Heat treatment of the thus-obtained particles at 523 K in air oxidized In metal of the core, resulting in the formation of spherical hollow particles made of crystalline In2O3. The size of the hollow particles was slightly larger than that of the In/In2O3 core/shell particles used as a starting material, whereas the void space formed inside hollow particles was smaller than the corresponding In metal cores. These facts indicated that in addition to the predominant outward diffusion of In ions, an inward transport of oxygen ions occurred, and thus an In2O3 crystal could be grown on both the inner concave and outer convex surfaces of the oxide shell layer.
  • Fumiaki Amano, Taikei Yasumoto, Orlando Omar Prieto Mahaney, Satoshi Uchida, Tamaki Shibayama, Yoshihiro Terada, Bunsho Ohtani
    TOPICS IN CATALYSIS 53 7-10 455 - 461 2010年06月 [査読有り][通常論文]
     
    Mesoscopic crystalline anatase particles of titanium(IV) oxide (titania) with decahedral morphology and with octahedral morphology were synthesized by gas-phase reaction of titanium(IV) chloride with oxygen and hydrothermal reaction of titanate nanowires in an alkaline medium, respectively, and their photocatalytic activities in relation with their crystal morphology were investigated.
  • 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 [査読有り][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.
  • Tatsuya Kameyama, Takaaki Osaki, Ken-ichi Okazaki, Tamaki Shibayama, Akihiko Kudo, Susumu Kuwabata, Tsukasa Torimoto
    JOURNAL OF MATERIALS CHEMISTRY 20 25 5319 - 5324 2010年 [査読有り][通常論文]
     
    Colloidal Cu2ZnSnS4 (CZTS) nanoparticles with sizes of 5-6 nm that contain no highly toxic elements were successfully synthesized through thermal reactions of metal acetate and sulfur in high-temperature oleylamine solution. The reaction temperature was a key factor for the synthesis of CZTS nanoparticles: synthesis at temperatures higher than 240 degrees C gave a pure CZTS crystal phase, whereas a secondary phase of CuS was formed at reaction temperatures lower than 180 degrees C. Nanoparticles were successfully accumulated on ITO-coated or quartz glass substrates via layer-bylayer deposition using 1,2-ethanedithiol as a cross-linking agent. The resulting CZTS particle films exhibited a photoresponse similar to that of p-type semiconductor photoelectrodes in an aqueous solution containing Eu(NO3)(3) as an electron scavenger. Potentials of the valence band edge and conduction band edge were determined from the onset potential of the cathodic photocurrent to be +0.3 and -1.2 V vs. Ag/AgCl, respectively.
  • Tsukasa Torimoto, Shoji Ogawa, Tomohiro Adachi, Tatsuya Kameyama, Ken-ichi Okazaki, Tamaki Shibayama, Akihiko Kudo, Susumu Kuwabata
    CHEMICAL COMMUNICATIONS 46 12 2082 - 2084 2010年 [査読有り][通常論文]
     
    The photoluminescence intensity of ZnS-AgInS2 solid solution nanoparticles was remarkably enhanced by increasing the heating temperature to 180 degrees C, above which the emission was simply diminished, while ZnS coating of the particles resulted in further enhancement of PL intensity, giving the highest quantum yield of ca. 80%.
  • Fumiaki Amano, Orlando-Omar Prieto-Mahaney, Yoshihiro Terada, Taikei Yasumoto, Tamaki Shibayama, Bunsho Ohtani
    CHEMISTRY OF MATERIALS 21 13 2601 - 2603 2009年07月 [査読有り][通常論文]
  • Fumiaki Amano, Taikei Yasumoto, Tamaki Shibayama, Satoshi Uchida, Bunsho Ohtani
    APPLIED CATALYSIS B-ENVIRONMENTAL 89 3-4 583 - 589 2009年07月 [査読有り][通常論文]
     
    Nanowire-structured titanate with titanium(IV) oxide (titania) was obtained by calcination of potassium ion-containing titanate nanowires prepared through alkali treatment of titania nanoparticles. The presence of potassium ions in the as-synthesized titanate nanowires was required for maintenance of the nanowire structure under the conditions of post-heat treatment. The crystallite structure, composition, morphology, specific surface area, pore volume distribution, and optical properties were found to be dependent on the temperature at which titanate nanowires were calcined. Photocatalytic activity was examined using three probe reactions: oxidative decomposition of acetic acid in an aqueous solution, oxygen liberation from an aqueous silver sulfate solution, and hydrogen liberation from an aqueous methanol solution in the presence of hexachloroplatinic acid as a precursor of photodeposition of platinum particles. Detailed characterization and results of photocatalytic activity tests revealed that titanate crystallites greatly contributed to the photocatalytic activities of the calcined nanowires except for photocatalytic hydrogen liberation. It was found that platinum was preferentially photodeposited on anatase crystallites rather than on titanate crystallites for hydrogen liberation. (C) 2009 Elsevier B.V. All rights reserved.
  • Fumiaki Amano, Taikei Yasumoto, Orlando-Omar Prieto-Mahaney, Satoshi Uchida, Tamaki Shibayama, Bunsho Ohtani
    CHEMICAL COMMUNICATIONS 17 2311 - 2313 2009年 [査読有り][通常論文]
     
    Octahedral titanium(IV) oxide (TiO(2)) crystallites with exposed anatase {101} facets exhibited relatively high photocatalytic activity for oxidative decomposition of organic compounds and low activity for hydrogen evolution in the absence of molecular oxygen, probably due to the characteristics of the anatase {101} surface.
  • Tsukasa Torimoto, Masayuki Hashitani, Takahito Konishi, Ken-ichi Okazaki, Tamaki Shibayama, Bunsho Ohtani
    JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 9 1 506 - 513 2009年01月 [査読有り][通常論文]
     
    The surface of cadmium sulfide nanorods was modified by 3-mercaptopropyltrimethoxysilane, followed by the hydrolysis of trimethoxysilyl groups to form a silica shell structure (SiO2/CdS[rod]). Size-selective photoetching was applied to SiO2/CdS[rod] to modify the size of the CdS rod core. The absorption spectra were blue-shifted by irradiation of monochromatic light, and finally absorption onset agreed with the wavelength of irradiation light. These facts indicated that CdS rod particles were photoetched to smaller ones until the irradiated photons were no longer absorbed by the photoetched particles and that the SiO2 shell layer surrounding the CdS rod core prevented coalescence between photoetched particles. Changes in the wavelength of irradiation light from 488 to 436 nm caused a decrease in rod width from 3.5 to 2.3 nm along with remarkable decrease in the length of rod from 14 to 4.2 nm, suggesting that the photoetching rate was dependent on the kind of crystal faces and that the photocorrosion reactions at the tips of the CdS rod, that is, on (001) and/or (00 (1) over bar) faces, were faster than those on other faces that appeared on the sides of the rod. This technique enabled control of CdS rod shape by selecting the wavelength of irradiation light.
  • 木下博嗣, 高橋平七郎, Dwi Gustiono, 坂口紀史, 柴山環樹, 渡辺精一
    日本金属学会誌 72 8 631 - 636 2008年08月 [査読有り][通常論文]
  • Tsukasa Torimoto, Tomohiro Adachi, Ken-ichi Okazaki, Miwa Sakuraoka, Tamaki Shibayama, Bunsho Ohtani, Akihiko Kudo, Susumu Kuwabata
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 129 41 12388 - + 2007年10月 [査読有り][通常論文]
     
    Nanoparticles of ZnS-AgInS2 solid solution (ZAIS) were synthesized by the thermal decomposition of (AgIn)(x) Zn2(1-x)(S2CN(C2H5)(2)) 4 precursors in a hot oleylamine solution. X-ray powder diffraction analyses revealed that the resulting nanoparticle powders were not a mixture of ZnS and AgInS2 but a ZnS-AgInS2 Solid solution in which the fraction of ZnS was enlarged with a decrease in the value of x, that is, an increase in the content of Zn2+ in the precursors used. The energy gap of ZAIS nanoparticles could be controlled by the composition of solid solution. Intense emission was observed at room temperature, regardless of the kind of the particles, the peak wavelength of PL being blue-shifted from 720 to 540 nm with a decrease in the value of x. The highest quantum yield of ca. 24% was obtained for nanoparticles prepared with x = 0.86, which was much higher than the quantum yields reported for I-III-VI2-based semiconductor nanoparticles, such as CuInS2 and ZnS-CuInS2 solid solution.
  • Y. Mishima, N. Yoshida, H. Kawamura, K. Ishida, Y. Hatano, T. Shibayama, K. Munakata, Y. Sato, M. Uchida, K. Tsuchiya, S. Tanaka
    JOURNAL OF NUCLEAR MATERIALS 367 B 1382 - 1386 2007年08月 [査読有り][招待有り]
     
    Recently, several research and development (R&D) programs of beryllium and its alloys for fusion reactor application have been conducted in Japan and the community of beryllium research has grown. In the R&D area of beryllium technology for a solid breeding blanket, a major subject is applications of beryllides, for which lifetime evaluation as neutron multiplier, impurity effect on irradiation behavior and recycling of irradiated materials are under investigation. As for neutron multiplier materials, recent R&D has focused on Be-Ti alloys based on Be12Ti as an advanced option, because of their superior properties compared with beryllium metal in such respects as compatibility with structural materials and oxidation resistance at higher temperatures. In this paper, recent results on beryllide R&D in Japan are described. (C) 2007 Elsevier B.V. All rights reserved.
  • Yasuaki Kitamura, Noriyuki Okinaka, Tamaki Shibayama, Orlando Omar Prieto Mahaney, Daisuke Kusano, Bunsho Ohtani, Tomohiro Akiyama
    POWDER TECHNOLOGY 176 2-3 93 - 98 2007年07月 [査読有り][通常論文]
     
    This paper describes a new type of combustion synthesis of metal oxide nanoparticles, in which the adiabatic flame temperature of the solid phase reaction is beyond the boiling point of the product, and its implementation for the synthesis of titanium dioxide as photocatalyst. In this study, raw materials comprising titanium particles of different sizes and sodium perchlorate were intensively mixed and ignited by an electrical heating foil to produce titanium dioxide through the following reaction: Ti+NaClO4 -> TiO2+NaCl. The shape and crystal structure of the titanium dioxide product significantly depended on the particle size of the titanium used as raw material. That is, the smaller titanium particles (average size (AS) of 10 mu m) resulted in rutile with an irregular shape, whereas the larger particles (AS of 25 gm) resulted in spheres of anatase. The photocatalytic activities of these samples were evaluated using the photocatalytic reactions of aqueous titanium dioxide suspensions containing methanol and acetic acid by irradiation at 298 K in argon atmosphere or in air. The activity of the rutile-rich sample was significantly larger than that of the anatase-rich one in both photocatalytic reactions. (c) 2007 Elsevier B.V. All rights reserved.
  • Yu Toriyabe, Seiichi Watanabe, Shigeo Yatsu, Tamaki Shibayama, Tadahiko Mizuno
    APPLIED PHYSICS LETTERS 91 4 041501-1 - 041501-3 2007年07月 [査読有り][通常論文]
     
    Formation of spherical nanoparticles (hereafter "nanoballs") in a gas/liquid mixed dual phase system during plasma electrolysis is reported. A gas/vapor sheath is formed at the electrode/electrolyte interface when the applied voltage is high enough to induce discharge plasma. Through this nonequilibrium process, the authors have produced Ni, Ti, Ag, and Au metallic nanoballs from the cathode mother materials with a certain size controllability. The electrode surface is partially melted by the local current concentration induced by electrothermal instability followed by an immediate cooldown, yielding nanoballs without contamination from electrolyte.
  • Hiroshi Kinoshita, Heishichiro Takahashi, Dwi Gustiono, Norihito Sakaguchi, Tamaki Shibayama, 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.
  • C. H. Zhang, T. Shibayama, Y. F. Jin, Y. T. Yang, L. H. Zhou, Y. Song
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 256 1 272 - 275 2007年03月 [査読有り][通常論文]
     
    In the present work p-type Si specimens were implanted with Cl ions of 100 keV to successively increasing fluences of 1 x 10(15), 5 x 10(15), 1 x 10(16) and 5 x 10(16) ions cm(-2) and subsequently annealed at 1073 K for 30 min. The microstructure was investigated with the transmission electron microscopy (TEM) in both the plane-view and the cross-sectional view. The implanted layer was amorphized after chlorine implantation even at the lowest ion fluence, while re-crystallization of the implanted layer occurs on subsequent annealing at 1073 K. In the annealed specimens implanted above the lowest fluence three layers along depth with different microstructures were found, which include a shallow polycrystalline porous layer, a deeper single-crystalline layer containing high density of gas bubbles, a well separated deeper layer composed of dislocation loops in low density. With increasing ion fluence the thickness of the porous polycrystalline layer increases. It is indicated that chlorine can suppress the epitaxial re-crystallization of implanted silicon, when the implant fluence of Cl ions exceeds a certain level. (c) 2006 Elsevier B.V. All rights reserved.
  • C. H. Zhang, Y. M. Sun, Y. Song, T. Shibayama, Y. F. Jin, L. H. Zhou
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 256 1 243 - 247 2007年03月 [査読有り][通常論文]
     
    In the present work specimens of mono-crystalline silicon carbide (4H polytype) were irradiated to three successively increasing ion fluences ranging from 7.2 x 10(14) to 6.0 x 10(16) ions/cm(2) (corresponding to the peak displacement damage of 1, 4 and 13 dpa) with Ne and Xe ions respectively with the energy of 2.3 MeV/amu. The irradiated specimens were subsequently annealed at temperatures of 1173 and 1273 K. Defect structure was investigated with transmission electron microscopy (TEM) using a cross-sectional specimen preparation technique. The typical microstructures of the annealed specimens irradiated with Ne or Xe ions to high fluences are characterized by small gas bubbles in high concentration in the peak damage region and black dots and dislocation loops (located in the basal plane) in a shallower and broader depth region. Larger dislocation loops were observed in the Xe-ion irradiated specimen than in the Ne-ion irradiated specimen at the same peak damage level. The enhanced formation of dislocation loops in the case of Xe-ion irradiation is understandable by assuming stronger inclination of heavier inert-gas atoms to occupy substitute site in the peak damage region. (c) 2006 Elsevier B.V. All rights reserved.
  • Tsutomu Uchida, Masafumi Nagayama, Tamaki Shibayama, Kazutoshi Gohara
    JOURNAL OF CRYSTAL GROWTH 299 1 125 - 135 2007年02月 [査読有り][通常論文]
     
    Freezing of solutions including disaccharides (trehalose, sucrose, and maltose) has been investigated by microscopic observations of freeze-fractured replicas using FE-TEM. Three typical features were observed: the smooth surface considered as the ice crystal, fine particles as the precipitated disaccharide molecules, and remaining part as the glass state of the solution. The expanded observations of fine particle and its distribution investigations suggested that it was larger than 10 nm in size and averaged approximately 20-30 nm in diameter. The smallest particle was estimated to include several hundred disaccharide molecules. Based on systematic observations of trehalose solutions regarding concentrations and freezing rates, we concluded that ice crystal growth was inhibited by trehalose molecules. Since the ice crystal size reduced exponentially with increase in trehalose concentration, we could control ice crystal size formed in the frozen material. The growth inhibition of ice crystals with trehalose resulted both from a reduction in the free water in the solution due to a significant hydration effect and from an enhancement of nucleation of the ice crystals. It was confirmed that trehalose was more effective than the other disaccharide solutions examined for inhibiting the growth of ice crystals. (c) 2006 Elsevier B.V. All rights reserved.
  • K. Shiramine, S. Muto, T. Shibayama, N. Sakaguchi, H. Ichinose, T. Kozaki, S. Sato
    Journal of Applied Physics 101 3 033527  2007年02月 [査読有り][通常論文]
     
    The tip artifact in atomic force microscopy (AFM) observations of InAs islands was evaluated quantitatively. The islands were grown in the Stranski-Krastanow mode of molecular beam epitaxy. The width and height of the islands were determined using transmission electron microscopy (TEM) and AFM. The average [(1) over bar 10] in-plane width and height determined using TEM excluding native oxide were 22 and 7 nm, respectively; those determined using AFM including the oxide were 35 and 8 nm, respectively. The difference in width was due to the oxide and the tip artifact. The sizes including the oxide were deduced from TEM observations to be a width of 27 nm and a height of 6 nm with correction for the thickness of the oxide. The residual difference of 8 nm between the width determined using AFM and that determined using TEM including the oxide was ascribed to the tip artifact. The results enable us to determine the actual size of the islands from their AFM images. (c) 2007 American Institute of Physics.
  • Yoshinao Mishima, Naoaki Yoshida, Heishichiro Takahashi, Kiyohito Ishida, Hiroshi Kawamura, Takaharu Iwadachi, Tamaki Shibayama, Ikuo Ohnuma, Yoshiyuki Sato, Kenzo Munakata, Hirotomo Iwakiri, Munenori Uchida
    FUSION ENGINEERING AND DESIGN 82 1 91 - 97 2007年01月 [査読有り][通常論文]
     
    Beryllides have remarkable characteristics besides their low density, such as high radiation resistance, high chemical stability, low hydrogen isotope retention and good high temperature mechanical strength especially for fusion applications. In order to have a practical usage for industrial applications, it is important to compile a set of quantitative data on such properties. It is also important to develop fabrication and processing paths to assure the processing of inherently brittle beryllides. The characterization and manufacturing technologies development have been carried out mainly on the Be12Ti interemetallic compounds at the Be-rich side of the Be-Ti binary system. In the present paper, up-dated results on several properties are described for the compound fabricated by hot isostatic pressing (HIP) and ingot metallurgy. Mechanical properties of the compounds having a duplex microstructure with neighboring phases are evaluated by compressive tests from room temperature to 1273 K. Radiation damage of the compound is preliminary studied by charged particle irradiation. Oxidation in air and the interaction with water vapor are evaluated. Thermal desorption of the deuterium is examined by using transmission electron microscopy (TEM) and thermal desorption spectrometry (TDS). Through these evaluations it seems that Be12Ti is superior as neutron multiplier with respect to pure Be metal. (c) 2006 Published by Elsevier B.V.
  • Akira Ohnuma, Ryu Abe, Tamaki Shibayama, Bunsho Ohtani
    CHEMICAL COMMUNICATIONS 33 3491 - 3493 2007年 [査読有り][通常論文]
     
    Assemblies of heterodimeric particles were prepared through selective coupling of two kinds of spherical silica particles of different sizes by connection with gold nanoparticles attached anisotropically to the particles.
  • Interface properties of Copper/Aluminum/Stainless steel clad materials
    Bae, D. S, Kim, S. K, Lee, S. P, Shibayama, T, Bae, D. H
    Key Engineering Materials 345-346 1497 - 1500 2007年 [査読有り][通常論文]
  • Tsukasa Torimoto, Shin-ya Murakami, Miwa Sakuraoka, Kentaro Iwasaki, Ken-ichi Okazaki, Tamaki Shibayama, Bunsho Ohtani
    JOURNAL OF PHYSICAL CHEMISTRY B 110 27 13314 - 13318 2006年07月 [査読有り][通常論文]
     
    Size-selective photoetching was applied to silica-coated cadmium selenide (SiO2/CdSe) nanoparticles to precisely control their photoluminescence properties. The absorption spectra of CdSe was blue-shifted by irradiation of monochromatic light, and finally, the absorption onset agreed with the wavelength of irradiation light, indicating that CdSe particles were photoetched to smaller ones until the irradiated photons were not absorbed by the photoetched particles and that the SiO2 shell layer surrounding the CdSe core prevented coalescence between the photoetched particles. Although as-prepared SiO2/CdSe did not exhibit photoluminescence, the application of size-selective photoetching to SiO2/CdSe resulted in the development of the band gap emission, with the degree being enhanced with progress of the photoetching. The peak wavelength of photoluminescence decreased with a decrease in the wavelength used for the photoetching, so that the luminescence color could be tuned between red and blue. Partial photoetching of SiO2/CdSe nanoparticle films produced intense band gap emission of CdSe at the photoetched area, while the remainder of the SiO2/CdSe films did not exhibit detectable photoluminescence, resulting in the formation of a clear photoluminescence image under UV irradiation. This technique makes it possible to produce a multicolored photoluminescence image by irradiation with monochromatic lights having various wavelengths using a single source material.
  • Kentaro Iwasaki, Tsukasa Torimoto, Tamaki Shibayama, Tomohiro Nishikawa, Bunsho Ohtani
    SMALL 2 7 854 - 858 2006年07月 [査読有り][通常論文]
  • JM Lackner, W Waldhauser, B Major, J Morgiel, L Major, H Takahashi, T Shibayama
    SURFACE & COATINGS TECHNOLOGY 200 11 3644 - 3649 2006年03月 [査読有り][通常論文]
     
    Chromium carbonitride (CrCxN1-x) coatings are becoming more and more interesting for wear protection applications due to their increased hardness and improved wear performance compared to chromium nitride (CrNx) hard coatings. Further improvements seem to be possible by using multilayer coatings of these two materials. In the current work such multilayer structures were deposited by the Pulsed Laser Deposition (PLD) technique at room temperature using an industrially designed 4-beam multi-spot PLD evaporator. The coatings were investigated by means of transmission electron microscopy (TEM) in order to solve their growth mechanisms and microstructure development. Due to the very high hardness and brittleness of the coatings, the TEM sample preparation has to be based on gallium focused ion beam cutting. Although the chemical analyses revealed a significant Ga atom contamination of the samples originating from the sample preparation, the face-centered cubic CrN-based phases and their textures, found in electron micro-diffraction analyses as well as in X-ray diffraction measurements, were scarcely influenced by the incorporated atoms. Great influences on the phase formation result from oxygen atom trapping from the rest gas atmosphere prior deposition. A very fine grained (2-5 nm) structure was found for the pure chromium adhesive interface layers, which are necessary for high adhesion of the hard coating layers. These hard ceramic layers-CrNx and CrCxN1-x-possess much coarser (8-15-nm grain size), micro-columnar structures. Furthermore, influences on the film growth are caused by defects on the substrate surface like cracks and contaminating dust particles. (c) 2005 Elsevier B.V. All rights reserved.
  • DS Bae, SK Kim, SP Lee, H Kinoshita, T Shibayama, H Takahashi
    FUSION ENGINEERING AND DESIGN 81 8-14 969 - 974 2006年02月 [査読有り][通常論文]
     
    The matrix and heat affected zone (HAZ) of welded SUS304 steel has been irradiated in an 1250 kV high voltage electron microscope at 673 K to 5.4 dpa (displacements per atom) to study the effect of electron irradiation on microstructure. In situ observation shows the voids formed by electron-beam irradiation coalescence which grew to larger sizes with irradiation dose. Values of void size, void number density and void swelling in HAZ were larger than those of the matrix, and these increased and saturated gradually with irradiation dose. Non-equilibrium segregation phenomenon involving Cr depletion and Ni enrichment at grain boundaries were also observed in both the HAZ and matrix of welded SUS304 steel. (c) 2005 Elsevier B.V. All rights reserved.
  • β-Ni(Al,Cr)合金に形成されるAl2O3 酸化皮膜の耐剥離性に及ぼすZr 添加の影響
    東本英哲, 山内啓, 柴山環樹, 渡辺精一, 黒川一哉, 成田敏夫
    プラズマ応用科 14 87 - 93 2006年 [査読有り][通常論文]
  • Microstructures of SiO2 scale formed on MoSi2
    Kurokawa, K, Goto, D, Kuchino, J, Yamauchi, A, Shibayama, T
    Materials Science Forum 522-523 595 - 602 2006年 [査読有り][通常論文]
  • B Pal, T Torimoto, S Ikeda, T Shibayama, K Sugawara, H Takahashi, B Ohtani
    TOPICS IN CATALYSIS 35 3-4 321 - 325 2005年07月 [査読有り][通常論文]
     
    Gold (Au) nanoparticles were deposited inside silica: (SiO2) shells containing cadmium sulfide (CdS) nanoparticles through photocatalytic reduction of potassium dicyanogold(I) by CdS. Photocatalytic Au deposition occurred only when core-shell nanoparticles having a void space between the core and shell, i.e., a jingle-bell-shaped structure, were used. These core-shell nanoparticles were prepared by size-selective photoetching of SiO2 -covered CdS nanoparticles. The size of Au nanoparticles could be controlled by adjustment of the void space in SiO2-covered CdS. Dissolution of CdS by acid treatment from the Au-deposited jingle-bell nanoparticles did not have any effect on the surface-plasmon absorption by Au. These facts indicate that Au nanoparticles of adjustable size can be prepared in an SiO2 shell that prevents mutual coalescence of Au nanoparticles but allows permeation of molecules and ions.
  • B Pal, T Torimoto, K Iwasaki, T Shibayama, H Takahashi, B Ohtani
    JOURNAL OF APPLIED ELECTROCHEMISTRY 35 7-8 751 - 756 2005年07月 [査読有り][通常論文]
     
    Photocatalytic deposition of gold (Au) and silver (Ag) nanoparticles was investigated using jingle-bell-shaped silica (SiO(2))-coated cadmium sulfide (CdS) nanoparticles (SiO(2)/CdS), which each had a void space between the CdS core and SiO(2) shell, as a photocatalyst. A size-selective photoetching technique was used to prepare the jingle bell nanostructure of SiO(2)/CdS. Nanoparticles of Au and Ag were deposited by irradiation of the photoetched SiO(2)/CdS in the presence of the corresponding metal complexes under deaerated conditions. Chemical etching of Au-deposited particles enabled the selective removal of CdS without any influence on the surface-plasmon absorption of Au. TEM analyses of the resulting particles suggested that some particles were encapsulated in hollow SiO(2) particles, while other Au particles were deposited on the outer surface of the SiO(2) shell. Emission spectra of the photoetched SiO(2)/CdS showed that the metal deposition developed a broad emission with a peak around 650 nm originating from surface defect sites, the degree being dependent on the kind of metal nanoparticles and their amount of deposition. This fact can be explained by the formation of metal-CdS binary nanoparticles having defect sites at the interface between metal and CdS.
  • M Arita, K Hamada, A Okada, H Asano, M Matsui, T Shibayama
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 44 1A 304 - 308 2005年01月 [査読有り][通常論文]
     
    The appearance of forbidden reflections in the electron diffraction patterns of L0.7Ca0.3MnO3 was studied, which violates the Prima symmetry reported so far in X-ray and. neutron diffractometry studies. The forbidden reflections originate through the multiple diffraction process of a crystal slightly inclined from its zone axis. Under this diffraction condition, the corresponding superlattice contrasts in high resolution transmission electron microscopy images were reproduced in image simulations made without the assumption of symmetry reduction in the crystal.
  • T Shibayama, Y Yoshida, Y Yano, H Takahashi
    JOURNAL OF ELECTRON MICROSCOPY 52 1 75 - 78 2003年 [査読有り][通常論文]
     
    Silicon carbide (SiC) matrix composites reinforced by SiC fibres (SiC/SiC composites) are currently being considered as alternative materials in high Ni alloys for high-temperature applications, such as aerospace components, gas-turbine energy-conversion systems and nuclear fusion reactors, because of their high specific strength and fracture toughness at elevated temperatures compared with monolithic SiC ceramics. It is important to evaluate the creep properties of SiC fibres under tensile loading in order to determine their usefulness as structural components. However, it would be hard to evaluate creep properties by monoaxial tensile properties when we have little knowledge on the microstructure of crept specimens, especially at the grain boundary. Recently, a simple fibre bend stress relaxation (BSR) test was introduced by Morscher and DiCarlo to address this problem. Interpretation of the fracture mechanism at the grain boundary is also essential to allow improvement of the mechanical properties. in this paper, effects of stress applied by BSR test on microstructural evolution in advanced SiC fibres, such as Tyranno-SA including small amounts of Al, are described and discussed along with the results of microstructure analysis on an atomic scale by using advanced microscopy.
  • D Gustiono, N Sakaguchi, T Shibayama, H Kinoshita, H Takahashi
    JOURNAL OF ELECTRON MICROSCOPY 52 5 449 - 453 2003年 [査読有り][通常論文]
     
    Phase-transformation behaviours were investigated for austenitic 301 stainless steel during implantation at room temperature with 300 keV Ti ions to fluences of 8 X 10(19)similar to3 X 10(21) ions m(-2) by means of transmission electron microscopy. The cross-sectional specimen was prepared using a focused ion beam. Plan observation of the implanted specimen showed that phase transformation from gamma-phase to alpha-phase was induced by implantation to a fluence of 3 X 10(20) Ti ions m(-2). The nucleation of the irradiation (implantation)-induced phase increased with the increase of the dose. The orientation relationship between the gamma matrix and the induced alpha martensitic phase was identified as (011)alpha//(111)gamma and [11-1]alpha//[10-1], close to the Kurdjumov-Sachs relationship. Cross-sectional observation after implantation to a fluence of 5 X 10(20) ions m(-2) showed that phase transformation mostly nucleated near the surface and occurred in the higher the concentration gradient of the implanted ion, i.e. a higher stress concentration takes place and this stress introduced by the implanted ions acts as a driving force for the transformation.
  • T Torimoto, JP Reyes, K Iwasaki, B Pal, T Shibayama, K Sugawara, H Takahashi, B Ohtani
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 125 2 316 - 317 2003年01月 [査読有り][通常論文]
  • Y Sueishi, N Sakaguchi, T Shibayama, H Kinoshita, H Takahashi
    JOURNAL OF ELECTRON MICROSCOPY 52 1 63 - 68 2003年 [査読有り][通常論文]
     
    We have investigated the formation of cascade clusters and structural changes in them by means of electron irradiation following ion irradiation in an austenitic stainless steel. Almost all of the cascade clusters, which were introduced by the ion irradiation, grew to form interstitial-type dislocation loops or vacancy-type stacking fault tetrahedra after electron irradiation at 623 K, whereas a few of the dot-type clusters remained in the matrix. It was possible to recognize the concentration of Ni and Si by radiation-induced segregation around the dot-type clusters. After electron irradiation at 773 K, we found that some cascade clusters became precipitates (delta-Ni2Si) due to radiation-induced precipitation. This suggests that the cascade clusters could directly become precipitation sites during irradiation.

MISC

  • 武田陽佑, 近藤創介, 近藤創介, 檜木達也, 中川祐貴, 柴山環樹 日本金属学会講演概要(CD-ROM) 163rd ROMBUNNO.P170 2018年09月05日 [査読無し][通常論文]
  • 関口亮, 柴山環樹, 近藤創介, 檜木達也 日本金属学会講演概要(CD-ROM) 159th ROMBUNNO.P82 2016年09月07日 [査読無し][通常論文]
  • 島田敏宏, 川人愛子, 田村貴大, XIE W, 石岡準也, 柴山環樹, 渡辺精一, 柳瀬隆, 長浜太郎 セラミックス基礎科学討論会講演要旨集 53rd 204 2015年01月08日 [査読無し][通常論文]
  • 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]
  • 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]
  • S. Suzuki, T. Suzuki, Y. Tomita, M. Hirano, K. Okazaki, T. Shibayama, S. Kuwabata, T. Torimoto CrystEngComm. 14 4922-4926 2012年06月01日 [査読無し][通常論文]
  • 柴山環樹, 渡辺精一, 谷津茂男, 富岡智, 西山修輔, 伊藤芳浩 日本金属学会講演概要(CD-ROM) 150th ROMBUNNO.249 2012年03月15日 [査読無し][通常論文]
  • 核融合炉ブランケット研究におけるベリリウム化合物の取り扱い
    柴山環樹, 中道勝, 宮本光貴, 久我典義 プラズマ・核融合学会誌 77 888 -892 2011年 [査読無し][通常論文]
  • 山内有二, 伊藤達哉, 日野友明, 信太祐二, 柴山環樹, 江里幸一郎, 鈴木哲, 秋場真人 核融合エネルギー連合講演会予稿集 8th (CD-ROM) ROMBUNNO.10A63P 2010年 [査読無し][通常論文]
  • プロジェクトレビュー 日米科学技術協力事業JUPITER-IIプロジェクト
    長谷川晃, 檜木達也, 清水昭比古, 柴山環樹, 横峯健彦, 野上修平 プラズマ・核融合学会誌 85 (5) 267 -275 2009年05月25日 [査読無し][通常論文]
  • 伊藤達哉, 信太祐二, 山内有二, 日野友明, 柴山環樹, 江里幸一朗, 鈴木哲, 秋場真人 日本原子力学会北海道支部研究発表会講演要旨集 27th 26 -27 2009年 [査読無し][通常論文]
  • まてりあ 48 (12) 617 -617 2009年 [査読無し][通常論文]
  • Research and development on in-situ TEM method for nanomechanics analysis to nanostructured composites
    Materia 48 (12) 617 -617 2009年 [査読無し][通常論文]
  • 柴山環樹, 岸本弘立, 香山 晃, 矢野康英 まてりあ 47 (12) 628 2008年12月 [査読有り][招待有り]
  • 核融合炉環境に耐える機能材料の開発 3.ブランケット機能材料
    小西哲之, 星野毅, 柴山環樹, 中道勝, 檜木達也, 鈴木晶大 84 (10) 646 -658 2008年10月 [査読有り][招待有り]
  • まてりあ 47 (12) 628 -628 2008年 [査読無し][通常論文]
  • 核融合炉環境に耐える機能材料の開発 3.ブランケット機能材料
    プラズマ・核融合学会誌 84 (10) 646 -658 2008年 [査読無し][通常論文]
  • Development on Nanomechanics Based Joining Analysis Method and SiC and W Joining for Gas Cooled Fast Reactor
    Materia 47 (12) 628 -628 2008年 [査読無し][通常論文]
  • Development of Functional Materials for Fusion Reactor Application 3. Functional Materials for Blankets
    Journal of Plasma Fusion Research 84 (10) 646 -658 2008年 [査読無し][通常論文]
  • Microstructural characterization and in-situ experiment of advanced SiC/SiC composites and joining for Fusion applications
    SHIBAYAMA Tamaki Introduction to the advanced nuclear technology in fusion, fuels and materials 2 187 -194 2007年07月 [査読有り][招待有り]
  • 核融合ブランケットの先進中性子増倍材料としてのベリリウム金属間化合物の開発
    土谷邦彦, 河村弘, 三島良直, 吉田直亮, 田中知, 内田宗範, 石田清仁, 柴山環樹, 宗像健三, 佐藤芳幸, 岩切宏友, 大沼郁雄 プラズマ・核融合学会誌 (3) 207 -214 2007年03月 [査読有り][招待有り]
  • 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]
  • <プロフェッショナル英和辞典 SPED TERRA/物質・工学編小学館プロフェッショナル英和、平成16年7月(ISBN:4-09-506711-X)>
    2004年 [査読無し][通常論文]
  • Analysis of Stress-Induced Burgers Vector Anisotropy in Pressurized Tube Specimens of Irradiated Ferritic-Martensitic Steels: JFMS and JLF-1
    Gelles, D. S, Kimura, A, Shibayama, T ASTM-STP 1366 2000年 [査読有り][通常論文]
     
    Gelles, D. S., Kimura, A., and Shibayama, T.: "Analysis of Stress-Induced Burgers Vector Anisotropy in Pressurized Tube Specimens of Irradiated Ferritic-Martensitic Steels: JFMS and JLF-1", Effects of Radiation Materials, ASTM-STP 1366, Edited by M. L. Hamilton, A. S. kumar, S. T. Roshinski and M. L. Grossbeck, 535-547(2000)*

所属学協会

  • プラズマ・核融合学会   日本原子力学会「照射損傷評価」研究専門委員会   日本原子力学会材料部会   日本顕微鏡学会   日本金属学会   

共同研究・競争的資金等の研究課題

  • 格子欠陥レベルで拡散経路を壅蔽する新奇酸化抑制機構の解明
    日本学術振興会:挑戦的研究(萌芽)
    研究期間 : 2019年07月 -2022年03月 
    代表者 : 柴山 環樹
  • 文部科学省:科学研究費補助金(基盤研究(C))
    研究期間 : 2014年 -2016年 
    代表者 : 柴山 環樹
  • 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。
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2004年 -2006年 
    代表者 : 柴山 環樹, 木下 博嗣, 坂口 紀史, 江藤 剛治
     
    平成16年度から平成18年度の3ヵ年にわたって共同研究者が開発した超高速カメラを現有の超高圧電子顕微鏡及び電界放射型分析透過電子顕微鏡に接続するための光学系及び実験手法などを開発し材料科学における高速現象を明らかにするために主たる研究を行った。平成18年度は、SiC/SiC複合材料の照射欠陥やクラック進展に関して高速観察を行った。更に3ヵ年計画の最終年度としてこれまでの成果を基に総まとめを行った。総合的に評価すると当初の目標に対して実験の進捗が計画通り進まなかったこともあり達成度は70%程度と推測されるが本研究の目的は十分明らかにしたと考えられる。また、ドイツにおいてレーザーを金属固体に照射し高強度な庵子を発生させる新しい概念に基づくパルス電子光源の開発がなされた。この電子源を改良し通常の電子顕微鏡の電子銃と交換した新しい電子顕微鏡が米国にて開発され、平成18年9月に札幌にて開催された国際顕微鏡学会にて報告された。既に材料科学のいくつかのトピックスに関して研究がなされており口頭やポスターでの発表があった。本研究は、一般的な連続して電子を発生する熱電子源及び電界放出電子源を使用しており、画像情報記録媒体側を高速記録型のCCDにすることで超高速化を狙っているのに対し米国の装置は、電子源をパルス化して記録側は通常の記録装置である。つまり、ストロボ的に高速現象をコマ取りして一連の高速現象を理解するという考え方である。しかしながら、ある現象の起点を知るためにはわれわれの方式の方に利点があり今後の展開が期待される。以上、国際的に見ても本研究はこの分野において先端領域に位置づけられ今後継続してプロジェクト研究を進めるべきである。また、3ヵ年に渡る本研究を通じて新たな課題が見つかったことから次のプロジェクトに向けて準備が整ったといえる。
  • 文部科学省:科学研究費補助金(奨励研究(A))
    研究期間 : 1994年 -1994年 
    代表者 : 柴山 環樹
     
    レーザー照射は、局所的に融点直下まで瞬時に加熱出来、照射を中止することにより急速冷却が可能である。その、特徴を用いて従来にない機能を発現する材料の開発が試みられている。一方、酸化物分散強化鋼は高温強化だけでなく耐照射特性に優れていることが明らかになってきた。しかしながら、強加工に起因する強度の異方性が構造材料に適用する場合、問題となっている。そこで、本研究ではレーザー照射を酸化物分散強化鋼にの表面改質に適用し強度の異方性を改善すること及び高温材料として期待されているTiALと接合し耐照射性及び高温強度にも優れた傾斜機能材料の開発に関する基礎的知見を得る事を目的とした。TiAlとの接合には、昨年度実施した奨励研究(A)において試みたTi、Al多層膜にレーザー照射を行うことによって合金化する事を適用し接合界面における組成の傾斜化を検討した。供試材として市販のMA957酸化物分散強化鋼を用いた。試料の形状は、棒鋼で30Ф×100である。レーザー照射には、3kW炭酸ガスレーザー加工機を本研究費で購入したコンピューターで制御し用いた。押し出し方向に対して平行と垂直に棒鋼をレーザー照射した。いずれの表面も、加工ガスがレーザー照射方向に吹き付けられるため急速溶解凝固した液的状の組織を呈していた。レーザ照射による熱影響を知らべるためそれぞれの切断方向に対し垂直に切断し金相観察を行った。表面から数μmの領域には、微細な空孔が観察出来た。しかし、それ以降の領域には観察出来ずほぼレーザー照射前と同様の組織を呈していた。そこで、400kV高分解能分析電子顕微鏡を用いて微細組織の同定を行ったところ、表面部分の組織は加工組織が消滅しほぼラス状のベイナイトを形成しており組織からは表面部分の組織の異方性は改質されたと考えられる。また、所々非晶質が観察されレーザー照射による非平衡相形成が認められた。
  • 文部科学省:科学研究費補助金(奨励研究(A))
    研究期間 : 1993年 -1993年 
    代表者 : 柴山 環樹
     
    レーザー照射は、従来の加熱装置に比べ急速加熱し急速冷却出来ることから従来にない機能を発現する新材料の開発手段として有効である。そこで、本研究は高温強度に優れ重量比強度が高い金属化合物の合金粉末作製にレーザー照射を適用すること、及び多層膜にレーザー照射を行い金属間化合物を作製することによって機械的特性を向上させ原子力材料としての適合性を明らかにすることを目的とした。科学研究費補助金で購入した市販のチタン板とアルミ板を積層させロータリーポンプで排気したチャンバー内に固定し、3KWの炭酸ガスレーザーを試料表面が焦点面になるようにして照射した。加工ガスには、窒素ガスを用いた。レーザー直下に設置した金型に吹き付けることによって得られた合金粉末の形状を調べるために走査電子顕微鏡で観察した結果、ほぼ球形で数mumの大きさであることがわかった。合金粉末の組成を調べるためにX線回折を行った結果、Ti_3Al及びTiAl,Al_3Tiが形成していることが判明した。その合金粉末を一軸冷間プレスを行って成形し、科学研究費補助金で購入した精密低速切断装置を用いて薄片化し電解研磨の後高分解能電子顕微鏡で微細組織観察を行った。制限視野電子回折像は、デバイシェーラー環と複数の斑点を示し組織が非常に微細で複数の相が混在していることを示唆された。タンデム型加速器を用いて3MeVのAu^<2+>イオンを540℃で約250dpaまで照射した結果、更に結晶粒は微細化しボイドは観察されなかった。今後、更に高温で照射実験を行い現在中性子照射中の試料と共に組織変化と機械的特性の変化について研究する計画である。以上、本研究においてチタンとアルミを積層させた多層膜にレーザーを照射することによってTi_3Al及びTiAl,Al_3Ti層を含む微細結晶粒の金属間化合物粉末を作製できることが明らかとなった。
  • ナノ構造材料の組織制御と革新的機能発現,超高速物質移動現象の可視化
  • utilization of innovative properties by control of nano structure in materials, visualization of ultra high speed phenomena in solid state

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