2021/10/27 更新

写真a

イトウ ケイジ
伊藤 恵司
ITOH Keiji
所属
教育学域 教授
職名
教授
外部リンク

学位

  • 博士(理学) ( 新潟大学 )

研究キーワード

  • Neutron Scattering

  • 中性子散乱

研究分野

  • エネルギー / 量子ビーム科学

学歴

  • 新潟大学    

    - 1999年

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    国名: 日本国

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  • 新潟大学   Graduate School, Division of National Science and Technology  

    - 1999年

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  • 山形大学   Faculty of Science  

    - 1994年

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  • 山形大学   理学部   化学

    - 1994年

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    国名: 日本国

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所属学協会

 

論文

  • Atomic-level characterization of free volume in the structure of Cu67Zr33 amorphous alloy 査読

    K Itoh, R Yamada, J Saida, K Ikeda, T Otomo

    Journal of Physics: Condensed Matter   33 ( 27 )   274001 - 274001   2021年7月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP Publishing  

    DOI: 10.1088/1361-648x/abfc12

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    その他リンク: https://iopscience.iop.org/article/10.1088/1361-648X/abfc12/pdf

  • High-pressure annealing driven nanocrystal formation in Zr50Cu40Al10 metallic glass and strength increase 査読

    Yuki Shibazaki, Rui Yamada, Junji Saida, Yoshio Kono, Masato Wakeda, Keiji Itoh, Masahiko Nishijima, Koji Kimoto

    Communications Materials   1 ( 1 )   2020年12月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:Springer Science and Business Media LLC  

    <title>Abstract</title>Pressure-induced structural changes in metallic glasses have been of great interest as they are expected to open new ways to synthesize novel materials with unexpected properties. Here, we investigated the effect of simultaneous high-pressure and high-temperature treatment on the structure and properties of a Zr<sub>50</sub>Cu<sub>40</sub>Al<sub>10</sub> metallic glass by in situ X-ray structure measurement and property analysis of the final material. We found the unusual formation of Cu-rich nanocrystals at high pressure and temperature, accompanied by significant strength and hardness enhancement. Based on reverse Monte Carlo modeling and molecular dynamics simulations, the structure of the metallic glass changed to a densely packed, chemically uniform configuration with high short-range and medium-range ordering at high pressure and temperature. These results show that high-pressure annealing processes provide a new way to improve and control properties without changing their composition.

    DOI: 10.1038/s43246-020-00057-3

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    その他リンク: http://www.nature.com/articles/s43246-020-00057-3

  • Structural study of Ni67Zr33 amorphous alloy: Interatomic space analysis approach 査読

    K. Itoh, J. Saida, T. Otomo

    Materials Chemistry and Physics   240   122214   2020年

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.matchemphys.2019.122214

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  • Free volume distribution and structural inhomogeneity in Ni50V50 amorphous alloy 査読

    K. Itoh, Y. Yoshioka, E.R. Barney, A.C. Hannon

    Journal of Alloys and Compounds   770   350 - 355   2019年1月

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    担当区分:筆頭著者   掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier BV  

    DOI: 10.1016/j.jallcom.2018.08.148

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  • Mechanochemical synthesis of binary phosphorus telluride: Short range structure and thermal properties 査読

    K. Itoh, Y. Mizuhara, T. Otomo

    Journal of Solid State Chemistry   267   119 - 123   2018年11月

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    担当区分:筆頭著者   掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier BV  

    DOI: 10.1016/j.jssc.2018.08.018

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  • Inhomogeneity of local packing density and atomic bonding of Ni67Zr33 amorphous alloy 査読

    K. Itoh, J. Saida, T. Otomo

    JOURNAL OF ALLOYS AND COMPOUNDS   732   585 - 592   2018年1月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    Pulsed neutron diffraction and synchrotron X-ray diffraction measurements were performed on a melt-quenching Ni67Zr33 amorphous alloy sample. The Ni-Ni, Ni-Zr and Zr-Zr nearest neighbour distributions were obtained from differences in the scattering intensities between the two probes in conjunction with the Gaussian fitting. The results demonstrate that the Ni-Zr and Zr-Zr nearest neighbour distributions are respectively represented by single Gaussian peaks but the Ni-Ni one is an asymmetric shape. Three-dimensional structure models were constructed by using reverse Monte Carlo (RMC) modelling method with fitting to the neutron and X-ray diffraction data sets. The Voronoi-Delaunay method was used on the RMC configurations to investigate the local packing properties of each coordination cluster. With reference to the macroscopic packing fraction, inhomogeneous structural feature arising from dense and loose packing domains is observed in the structure of Ni67Zr33 amorphous alloy. (C) 2017 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jallcom.2017.10.188

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  • Structural study of GeS 2 glass: Reverse Monte Carlo modelling for edge-sharing tetrahedral network 査読

    Keiji Itoh

    Journal of Physics and Chemistry of Solids   103   109 - 115   2017年4月

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    担当区分:筆頭著者   掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier BV  

    DOI: 10.1016/j.jpcs.2016.12.016

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  • Structure of Se-Te glasses studied using neutron, X-ray diffraction and reverse Monte Carlo modelling 査読

    Keiji Itoh

    JOURNAL OF SOLID STATE CHEMISTRY   246   372 - 378   2017年2月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ACADEMIC PRESS INC ELSEVIER SCIENCE  

    Pulsed neutron diffraction and synchrotron X-ray diffraction measurements were performed on Se100-xTex bulk glasses with x=10, 20, 30 and 40. The coordination numbers obtained from the diffraction results demonstrate that Se and Te atoms are twofold coordinated and the glass structure is formed by the chain network. The threedimensional structure model for Se60Te40 glass obtained by using reverse Monte Carlo modelling shows that the alternating arrangements of Se and Te atoms compose the major part of the chain clusters but several other fragments such as Se-n chains and Te-Te dimers are also present in large numbers. The chain clusters have geometrically disordered forms and the interchain atomic order is different from those in the crystal structures of trigonal Se and trigonal Te.

    DOI: 10.1016/j.jssc.2016.12.012

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  • Short- and medium-range order in Sb–Se glasses 査読

    Keiji Itoh

    Journal of Solid State Chemistry   233   368 - 373   2016年1月

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    担当区分:筆頭著者   掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier BV  

    DOI: 10.1016/j.jssc.2015.11.018

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  • Mössbauer study of the SmFe 2 hydride through 149Sm and 57Fe 査読

    Ryo Masuda, Takaya Mitsui, Keiji Itoh, Yasuhiro Kobayashi, Shinji Kitao, Makoto Seto

    Journal of the Physical Society of Japan   81 ( 3 )   2012年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We have applied the nuclear resonant forward scattering of synchrotron radiation by 149Sm and 57Fe Mössbauer spectroscopy to SmFe 2 and c-SmFe 2H x (x ≳ 3), to study the effect of hydrogen absorption on local electronic states. The averages of the parameters of the hyperfine structure of SmFe 2 and c-SmFe 2H x at 20K are as follows: the electric quadrupole splitting parameters of 149Sm are -10.3 ± 0.3 and -8.3 ± 0.3 mm/s, the magnetic hyperfine fields of 149Sm are 299 ± 8 and 326 ± 8 T, the isomer shifts of 57Fe are 0.07 ± 0.03 and 0.41 ± 0.03 mm/s, the electric quadrupole splitting parameters of 57Fe are 0 and 0.15 ± 0.03 mm/s, and the magnetic hyperfine fields of 57Fe are 20.4 ± 0.1 and 19.3 ± 0.1 T, respectively. The differences in these parameters between SmFe 2 and c-SmFe 2H x are discussed in connection with the modulation of local electronic states induced by lattice expansion and chemical effect of hydrogenation. The differences also imply the screening of interactions between Sm and Fe by inserted hydrogen atoms. © 2012 The Physical Society of Japan.

    DOI: 10.1143/JPSJ.81.034714

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  • An in situ Mössbauer study using synchrotron radiation 査読

    Ryo Masuda, Takaya Mitsui, Keiji Itoh, Kouji Sakaki, Hirotoshi Enoki, Yumiko Nakamura, Makoto Seto

    Hyperfine Interactions   204 ( 1-3 )   139 - 142   2012年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We have been developing a system for in situ Mössbauer studies using synchrotron radiation (SR) to elucidate the mechanism of hydrogenation processes. In the system, samples reacts in a pressure-temperature chamber and SR-based Mössbauer spectra using variable-frequency nuclear monochromator and energy spectra of inelastic nuclear resonant scattering (NRS) of SR are measured. As a feasibility study, the temperature dependence of the Mössbauer and inelastic NRS spectra of 57Fe in c-GdFe 2H 3 under vacuum were measured. In both spectra, clear differences were observed between 373 K and 573 K. These differences can be interpreted by the change of microscopic environment around Fe at the dehydrogenation. Thus, it is confirmed that this system works well enough to perform the in-situ Mössbauer study on the dehydrogenation of c-GdFe 2H 3. © 2011 Springer Science+Business Media B.V.

    DOI: 10.1007/s10751-011-0470-x

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  • Atomic structure of nanoscale quasicrystal-forming Zr-noble metal binary metallic glasses 査読

    J. Saida, K. Itoh, T. Sanada, S. Sato, M. Imafuku, M. Ohnuma, A. Inoue

    Journal of Alloys and Compounds   509 ( 1 )   S27 - S33   2011年7月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    We report the results of the local structural evaluation and mechanism of QC formation in the Zr70Pd30 and Zr80Pt 20 glassy alloys. Voronoi analysis indicates the difference of local environment between two alloys. The perfect icosahedron frequently exists around Zr atom and major polyhedra have prism-like structure around Pd in Zr 70Pd30. In contrast, icosahedral-like distorted polyhedra formation is favorable around Pt as well as Zr in Zr80Pt 20. It is therefore, concluded that the quasicrystallization originates from the medium-range order based on the Zr-centered perfect icosahedron and the Pd-centered prism-like ones remain during the QC phase formation in Zr70Pd30. Icosahedral-like local structure around Zr and Pt might contribute together to the nucleation of QC phase in Zr80Pt20. This feature with a different mechanism of QC formation in the two alloys may correlate to the difference of solute concentration and the structure of stable crystalline phase after the decomposition of QC phase. © 2010 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jallcom.2010.12.076

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  • Anomalous aggregation state of deuterium molecules in the nanoscale pores of a metal organic framework 査読

    Izuru Kanoya, Terumi Furuta, Ryogo Sakamoto, Mitsuya Hosoe, Masao Ichikawa, Keiji Itoh, Toshiharu Fukunaga

    Journal of Applied Physics   108 ( 7 )   2010年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The behavior of hydrogen molecules adsorbed onto the nanospace of porous materials is of great interest but is poorly understood. Here we show direct visualization of deuterium molecules adsorbed on isoreticular metal organic frameworks (IRMOF-1) at 77 K using reverse Monte Carlo simulation based on first principle molecular dynamics simulation and neutron diffraction. Results show that the two types of adsorption sites around a ZnO4 cluster are almost fully occupied by the deuterium molecules but that other sites are not fully occupied. Moreover an interesting information about the aggregation state of deuterium molecules was directly obtained from the deuterium-deuterium partial pair distribution function. Namely, the average distance of deuterium molecules adsorbed onto IRMOF-1 is slightly longer than that in a solid state but much shorter than that in the corresponding gas state. © 2010 American Institute of Physics.

    DOI: 10.1063/1.3490625

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  • Crystal Structure of Li7P3S11 Studied by Neutron and Synchrotron X-ray Powder Diffraction 査読

    Onodera Yohei, Mori Kazuhiro, Otomo Toshiya, Hannon Alex C, Kohara Shinji, Itoh Keiji, Sugiyama Masaaki, Fukunaga Toshiharu

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   79   2010年1月

  • Ionic conductivity and structural properties of lithium lanthanum titanate quenched into liquid nitrogen studied by neutron powder diffraction 査読

    Kazuhiro Mori, Kenji Iwase, Masao Yonemura, Joan Siewenie, Thomas Proffen, Yohei Onodera, Keiji Itoh, Masaaki Sugiyama, Takashi Kamiyama, Toshiharu Fukunaga

    Journal of the Physical Society of Japan   79   84 - 86   2010年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:Physical Society of Japan  

    For 7Li-enriched La2/3-x 7Li 3xTiO3 samples quenched into liquid nitrogen and cooled in the furnace, impedance measurements and time-of-flight neutron powder diffraction (TOF-NPD) experiments were carried out in order to study the effect of the quenched-into-liquid-nitrogen treatment for the ionic conduction and the structural properties. It was found that the quenched-into-liquid-nitrogen treatment enhances the lithium ionic conductivity in the 7Li-content range between 3x ∼ 0.25 and 0.45. Furthermore, the local structure within 6 Å did not change, according to the atomic pair density function (PDF) analysis. © 2010 The Physical Society of Japan.

    DOI: 10.1143/JPSJS.79SA.84

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  • Microstructure of hydrogenated Mg2Ni studied by SANS 査読

    K. Mori, M. Sugiyama, K. Iwase, S. Kawabe, Y. Onodera, K. Itoh, T. Otomo, T. Fukunaga

    Journal of Physics: Conference Series   247   2010年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:Institute of Physics Publishing  

    X-ray powder diffraction (XRD) and small-angle neutron scattering (SANS) experiments were carried out for the hydrogenated and duterated Mg 2Ni, respectively. According to the results of XRD experiments, both of them coexisted with unhydrogenated (or undeuterated) Mg2Ni in the hydrogen absorbing cycle. Furthermore, in the SANS experiments, a slope of SANS curve, I(Q), was roughly evaluated by using the following power law: I(Q) Q -m, where Q is the magnitude of the scattering vector, and m can be equated with a fractal dimensionality, DS (= 6 - m). In conclusion, the hydrogenated and duterated Mg2Ni showed DS∼ 3 and ∼ 2, respectively. The significant difference between DS's can be understood by considering the scattering length densities, ρ, of Mg 2Ni, Mg2NiH4, and Mg2NiD 4. © 2010 IOP Publishing Ltd.

    DOI: 10.1088/1742-6596/247/1/012036

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  • SAXS and SANS observations of abnormal aggregation of human •-crystallin 査読

    Masaaki Sugiyama, Norihiko Fujii, Yukio Morimoto, Keiji Itoh, Kazuhiro Mori, Toshiharu Fukunaga, Noriko Fujii

    Chemistry and Biodiversity   7 ( 6 )   1380 - 1388   2010年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Wiley-VCH Verlag  

    Aggregation states of human α-crystallins are observed complementarily using small-angle X-ray and small-angle neutron scatterings (SAXS and SANS). Infant α-crystallin is almost a monodispersed system of the aggregates with gyration radius of ca. 60 Å, which is a normal aggregate. On the other hand, the aged and cataract α-crystallins have not only the normal but also the larger aggregates. In the aged alpha
    -crystallin, the normal aggregate is a major component, but in the cataract α-crystallin the larger ones are dominant. Both αA- and alpha
    B-crystallins, which are subunits of α-crystallin, also form an aggregate with the size close to the normal aggregate. Under UV irradiation, only aggregates of αB-crystallin undergo further aggregation. Therefore, considering increase of ratio of αB-crystallin in the aggregate of alpha
    -crystallin as aging, the abnormal aggregation (formation of the huge aggregates) mainly results in the further aggregation of alpha
    B-crystallin caused by external stresses. © 2010 Verlag Helvetica Chimica Acta AG.

    DOI: 10.1002/cbdv.200900332

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  • Newly designed neutron diffraction cell for fluids at high temperatures and high pressures 査読

    Hiroki Iwase, Nobuyuki Matubayasi, Yasuo Kameda, Keiji Itoh, Toshiya Otomo, Masaru Nakahara

    Japanese Journal of Applied Physics   49 ( 1 )   2010年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A high-pressure and high-temperature cell for neutron diffraction experiments on fluids is developed. The new cell is made of Ti-Zr null-alloy (34% titanium and 66% zirconium) so that the average scattering length for neutrons can be made to be zero. Experimental variables as high pressure and high temperature can be finely controlled for fluids using a known equation of state by setting the cell in a standard IR image furnace. The simple system requires no high pressure-generating and -controlling units. © The Japan Society of Applied Physics.

    DOI: 10.1143/JJAP.49.016602

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  • SANS investigation of assembly state of proteasome activator 28 and the 20S proteasome 査読

    Masaaki Sugiyama, Eiji Kurimoto, Hiroki Sahashi, Eri Sakata, Yukio Morimoto, Keiji Itoh, Kazuhiro Mori, Toshiharu Fukunaga, Yasufumi Minami, Koichi Kato

    Journal of Physics: Conference Series   247   2010年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:Institute of Physics Publishing  

    The state of proteasome activator 28 (PA28) and the formation of the proteasomal complex in an aqueous solution are investigated with small-angle neutron scattering (SANS). The most appropriate state of PA28, which well reproduces the observed SANS profile, is the dissociation equilibrium between dimer and monomer with dissociation degree of 0.5. In addition, it is revealed that the packing of PA28 in the dimer is same as that in a crystal. It is also revealed that the proteasomal complex in which two PA28s connects to both basal planes of the 20S proteasome is spontaneously formed in the mixture solution of PA28 and the 20S proteasome. © 2010 IOP Publishing Ltd.

    DOI: 10.1088/1742-6596/247/1/012020

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  • Heating rate dependence of Tg and Tx in Zr-based BMGs with characteristic structures 査読

    E. Matsubara, T. Ichitsubo, K. Itoh, T. Fukunaga, J. Saida, N. Nishiyama, H. Kato, A. Inoue

    Journal of Alloys and Compounds   483 ( 1-2 )   8 - 13   2009年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Heating rate dependence of glass transition and crystallization temperatures is applicable for evaluation of glass structural stability and also for discussion on the apparent activation energies for glass transition and crystallization. The glass-structure stabilities of the Zr-based BMGs (Zr50Cu40Al10, Zr70Cu20Al10 and Zr70Ni20Al10) and the conventional amorphous alloys (Zr70Cu30 and Zr70Ni30) are assessed by the densely packed glass structure as well as the complicated crystallization process. By the reverse Monte Carlo (RMC) simulation with X-ray and neutron diffraction data, it is shown that the densely packed structure is built by icosahedron-like clusters. In Zr65Al7.5Ni10Pd17.5 and Zr65Al7.5Ni10Cu17.5, the effect of Pd atoms on the glass structure is also described. © 2008 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jallcom.2008.07.225

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  • Structural study on Zr0.39Ni0.61 and (Zr0.39Ni0.61)D0.59 amorphous alloys by neutron and X-ray diffraction 査読

    K. Itoh, T. Watanabe, T. Otomo, M. Sugiyama, K. Mori, T. Fukunaga

    Journal of Alloys and Compounds   483 ( 1-2 )   213 - 216   2009年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Neutron and X-ray diffraction and reverse Monte Carlo (RMC) simulation were performed on Zr0.39Ni0.61 and (Zr0.39Ni0.61)D0.59 amorphous alloys to investigate the rearrangement of metal atoms due to the deuterium absorption. The RMC models showed that the Zr-Zr distances slightly increase but the Zr-Ni and Ni-Ni distances remain virtually unchanged after the deuterium absorption. Additionally, the Voronoi polyhedral analysis of the RMC configurations showed that there is not much difference in the local structure around Zr and Ni between Zr0.39Ni0.61 and (Zr0.39Ni0.61)D0.59 amorphous alloys. © 2008 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jallcom.2008.07.150

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  • Structural investigation on supercritical carbon dioxide and its mixture with alcohol 査読

    Takashi Sato, Masaaki Sugiyama, Masakatsu Misawa, Kei Hamada, Keiji Itoh, Kazuhiro Mori, Toshiharu Fukunaga

    Journal of Molecular Liquids   147 ( 1-2 )   102 - 106   2009年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Small-angle neutron scattering (SANS) experiments were carried out for three different systems, pure CO2, CO2 + methanol (1 mol%) and CO2 + ethanol (1 mol%), along the isotherm of 311.15 K in their supercritical states. All the SANS profiles were well analyzed with Ornstein-Zernike equation. With addition of the alcohols, the maximum values of the correlation length, ξ, and the scattering intensity at Q = 0, I(0), became larger, and the pressure at which ξ and I(0) became maxima was shifted to be lower. These changes can be explained qualitatively with van der Waals equation of state by regarding CO2 + alcohol mixture as a system consisting of a single kind of virtual molecules. From this analysis, both the molecular attractive interaction and volume are suggested to be increased in the mixture. These changes were considered to be strongly connected with the increase of solubility and selectivity on entrainer effect. © 2008 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.molliq.2008.06.017

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  • Crystal structure of Fe-doped lanthanum gallate for oxygen partial pressures studied by neutron powder diffraction 査読

    Kazuhiro Mori, Ryoji Kiyanagi, James W. Richardson Jr., Joe Fieramosca, Yohei Onodera, Keiji Itoh, Masaaki Sugiyama, Takashi Kamiyama, Toshiharu Fukunaga

    Solid State Ionics   180 ( 6-8 )   541 - 545   2009年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Neutron powder diffraction experiments were carried out to investigate a change in a crystal structure of La0.8Sr0.2Ga0.65Fe0.35O3 for oxygen partial pressures, PO2, at 800 °C. The crystal structure was refined on the basis of the R3̄c symmetry for the PO2 range from 10- 1 to 10- 20 atm, by the Rietveld analysis. It was found that lattice parameters, a and c, monotonically expand with decreasing PO2, and then both expansions are rapidly suppressed below 10- 4 atm. In the meantime, lM-O and lO-O(2) also discontinuously increased with decreasing PO2, while lO-O(1) did not change at all PO2, where lM-O, lO-O(1) and lO-O(2) are the bond lengths within a MO6 octahedron (M = Ga0.65Fe0.35). This result indicates that the lM-O and the lO-O(2) are more important than the lO-O(1) for such a complicated lattice expansion for PO2. © 2008 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.ssi.2008.07.001

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  • Structure of Na2S-GeS2 glasses studied by using neutron and X-ray diffraction and reverse Monte Carlo modeling 査読

    Keiji Itoh, Toshiharu Fukunaga

    Solid State Ionics   180 ( 4-5 )   351 - 355   2009年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Neutron and X-ray diffraction measurements were performed to investigate the structure of Na2S-GeS2 glasses synthesized by mechanical alloying. The Ge-S coordination numbers calculated from the total correlation functions show that GeS4 tetrahedra form the basic framework structure of Na2S-GeS2 glasses. In addition, a three-dimensional structural model of the (Na2S)50(GeS2)50 glass was obtained by using reverse Monte Carlo (RMC) simulation on neutron and X-ray diffraction data, and it was compared with the RMC model previously obtained for a (Li2S)50(GeS2)50 glass. The results show that the Ge-S framework structures in the two glasses are almost the same in the short and intermediate ranges
    that is, the Ge-S framework structures are formed mainly by the connection of corner-sharing GeS4 tetrahedra. Many of the Na ions are coordinated by four S atoms, which are non-bridging S atoms and/or bridging S atoms. © 2009 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.ssi.2009.01.008

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  • Structural study of amorphous LaNi5Dx: In situ neutron and X-ray diffraction experiments in deuterium gas 査読

    K. Itoh, T. Shoumura, M. Sugiyama, K. Mori, T. Fukunaga

    Journal of Alloys and Compounds   474 ( 1-2 )   4 - 8   2009年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    In situ neutron and X-ray diffraction measurements at various D2 pressures up to 2.28 MPa were performed on amorphous LaNi5Dx prepared by mechanical alloying in D2 gas. Reverse Monte Carlo (RMC) simulation based on the neutron and X-ray diffraction data was performed to construct a three-dimensional atomic model of these amorphous alloys. The RMC models show that more than 90% of the deuterium atoms occupy tetrahedral sites consisting of La and/or Ni atoms. Moreover, most occupy the 2Ni + 2La and 3Ni + La tetrahedral sites. © 2008 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jallcom.2008.06.044

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  • SANS simulation of aggregated protein in aqueous solution 査読

    Masaaki Sugiyama, Kei Hamada, Koichi Kato, Eiji Kurimoto, Kenta Okamoto, Yukio Morimoto, Susumu Ikeda, Sachio Naito, Michihiko Furusaka, Keiji Itoh, Kazuhiro Mori, Toshiharu Fukunaga

    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment   600 ( 1 )   272 - 274   2009年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Small-angle neutron scattering (SANS) of aggregated protein in an aqueous solution is simulated based on the crystallographic data of the protein. After obtaining the crystallographic data of the target protein, hydrogen atoms are added to the data and then some hydrogen atoms are replaced with deuterium atoms. The structure models are made with this data and then their gyration radii and SANS intensities are calculated. Compared the calculated SANS data with the experimental one, the most probable structure is determined. With this analysis method, the aggregate structure of proteasome α7-subunit (PRSα) in an aqueous solution was investigated. Three structural models, a simple monomer and two types of dimers, were supposed as the aggregated structure of PRSα. The analysis showed that the best compromised structure was the dimer, which was consistent with electron microscopy observation. © 2008 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.nima.2008.11.121

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  • Structural and electrochemical properties of La0.8Sr0.2Ga1-xFexO3 査読

    Kazuhiro Mori, Yohei Onodera, Ryoji Kiyanagi, James W. Richardson Jr., Keiji Itoh, Masaaki Sugiyama, Takashi Kamiyama, Toshiharu Fukunaga

    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment   600 ( 1 )   328 - 331   2009年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Mixed ionic-electronic conductor of Fe doped lanthanum gallate, La0.8Sr0.2Ga1-xFexO3, has been studied by the dc four-probe method and the neutron powder diffraction. In the electrical conductivity measurement at RT, insulator-metal transition-like phenomenon was observed at around x∼0.35
    this suggests an existence of the percolation limit for the electronic conductivity. Simultaneously, a bond length between O atoms, lO-O, in a MO6 octahedron (M{double bond, long}Ga1-xFex) drastically expands over x∼0.4, according to the result of crystal structure refinement based on the hexagonal phase. Such a drastic expansion in the lO-O would induce the decrease in the oxygen ionic conductivity. © 2008 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.nima.2008.11.084

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  • Chemically oxidized γ-MnO2 for lithium secondary batteries: Structure and intercalation/deintercalation properties 査読

    Won Il Jung, Miki Nagao, Cédric Pitteloud, Keiji Itoh, Atsuo Yamada, Ryoji Kanno

    Journal of Materials Chemistry   19 ( 6 )   800 - 806   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Structural changes of chemically lithiated γ-MnO2 during chemical oxidation were characterized by X-ray diffraction combined with a stacking fault analysis and neutron total scattering with a local structure analysis. Lithium ions intercalate into the crystallographic sites around "Ruetschi" protons prior to those around "Coleman" protons for the chemically lithiated γ-MnO2. The "Ruetschi" and "Coleman" protons have O-H bond lengths of 1.2 A° and 1.9 A°, respectively, which decreased after the chemical oxidation. The chemically intercalated lithium ions are placed at the center of oxygen octahedra with an O-Li length of 1.9 A°. © The Royal Society of Chemistry 2009.

    DOI: 10.1039/b812683f

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  • Evaluation of the local environment for nanoscale quasicrystal formation in Zr80Pt20 glassy alloy using Voronoi analysis 査読

    Junji Saida, Keiji Itoh, Shigeo Sato, Muneyuki Imafuku, Takashi Sanada, Akihisa Inoue

    Journal of Physics Condensed Matter   21 ( 37 )   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The local atomic structure of nano-quasicrystal-forming Zr 80Pt20 binary glassy alloy was investigated by reverse Monte Carlo modeling based on the results of x-ray diffraction. A prepeak at Q∼17nm-1 originating from the unique bonding between the Pt-Pt pair is observed in the structure factor. Voronoi analysis indicates that an icosahedral-like polyhedron is formed around Pt. It is also found that icosahedral-like polyhedra exist around Zr
    however, the fraction of perfect icosahedra is considerably lower than that in the nano-quasicrystalforming Zr70Pd30 glassy alloy. A difference in the local environment between the two binary quasicrystal-forming glassy alloys is suggested. © 2009 IOP Publishing Ltd.

    DOI: 10.1088/0953-8984/21/37/375104

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  • Pulsed neutron diffraction study of NaNO2 and KNO2 pure melts 査読

    Yasuhiko Iwadate, Takumi Harada, Takahiro Ohkubo, Kazuko Fukushima, Masakatsu Misawa, Toshiharu Fukunaga, Keiji Itoh

    Electrochemistry   77 ( 8 )   741 - 744   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Electrochemical Society of Japan  

    The short-range structural parameters for NaNO2 and KNO 2 pure melts were determined by the time-of-flight neu-tron diffraction. The precise analyses of structural parameters obtained such as coordination number, interatomic distance, and temperature factor allowed us to conclude that (1) there exist stable NO2- anions in the melts, (2) NO2- anions behave like NO3- anions due to the existence of lone pairs of electrons, (3) the short-range structure of KNO2 pure melt is similar to that of NaNO2 pure melt but the cation site relative to anion is a little different from each other in terms of the cation size effect.

    DOI: 10.5796/electrochemistry.77.741

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  • Structure of Mg50Ni50 amorphous alloy studied by using X-ray diffraction and reverse Monte Carlo modelling 査読

    K. Itoh, T. Otomo, M. Sugiyama, K. Mori, T. Fukunaga

    Journal of Physics: Conference Series   144   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Institute of Physics Publishing  

    X-ray diffraction measurement was performed on an Mg50Ni 50 amorphous alloy prepared by mechanical alloying under an Ar atmosphere. Reverse Monte Carlo (RMC) simulation based on the X-ray diffraction data was used to construct a three-dimensional atomic arrangement of the amorphous alloy. In addition, the local environments around the Mg and Ni atoms were investigated by using Voronoi polyhedral analysis on the RMC configuration. The results show that isosahedral structures are predominant around the Mg and Ni atoms in Mg50Ni50, although prismatic local structures are present around some of the Ni atoms. © 2009 IOP Publishing Ltd.

    DOI: 10.1088/1742-6596/144/1/012107

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  • Structural difference between liquidlike and gaslike phases in supercritical fluid 査読

    Takashi Sato, Masaaki Sugiyama, Keiji Itoh, Kazuhiro Mori, Toshiharu Fukunaga, Masakatsu Misawa, Toshiya Otomo, Shinichi Takata

    Physical Review E - Statistical, Nonlinear, and Soft Matter Physics   78 ( 5 )   2008年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Density fluctuation structures of supercritical carbon dioxide along the isothermal and isochoric lines were observed with small-angle neutron scattering (SANS). All the scattering intensities in the low- Q range were well described with the Ornstein-Zernike (OZ) equation. It was confirmed that there exists a locus where the OZ correlation length and scattering intensity at Q=0 exhibit extrema on the isothermal lines: this locus, named the ridge, was interpreted as the boundary by which the supercritical state is divided into liquidlike and gaslike phases. In order to clarify the difference of the fluctuation structure between the liquidlike and the gaslike phases, a real-space molecular distribution was obtained with a reverse Monte Carlo (RMC) method. Number density distributions of C O2 molecules at all measured states were calculated with the real-space molecular distributions obtained. In addition, the statistical parameters of the number density distributions, the standard deviations, and the skewnesses, were examined. The standard deviations of the number density distributions almost coincide with the results of the OZ analysis. On the other hand, the skewnesses, which describe the asymmetric nature of the number density distribution, clearly showed a difference between the two phases: the skewness became negative in the liquidlike phase, positive in the gaslike phase, and almost zero at the nearest state to the ridge in all isotherms. It was proved with simple equations of statistical mechanics that the skewness is described as the first differential of the magnitude of the density fluctuation with respect to the pressure. We conclude that the skewness, obtained with a RMC analysis for SANS data, is an important structural parameter distinguishing between the liquidlike and gaslike phases. © 2008 The American Physical Society.

    DOI: 10.1103/PhysRevE.78.051503

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  • Partial pair correlation functions of low-density supercritical water determined by neutron diffraction with the H/D isotopic substitution method 査読

    Toshiya Otomo, Hiroki Iwase, Yasuo Kameda, Nobuyuki Matubayasi, Keiji Itoh, Susumu Ikeda, Masaru Nakahara

    Journal of Physical Chemistry B   112 ( 15 )   4687 - 4693   2008年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Chemical Society  

    Neutron diffraction measurements were carried out on H/ D isotopically substituted water in the low-density supercritical condition (T = 673 K, P = 26.3 MPa, and ρ = 0.0068 molecules-Å-3) in order to obtain direct information on the intermolecular partial structure functions, gHH inter(r), gOHinter(r), and gOOinter(r). In correspondence to the high-density supercritical water previously reported, the intermolecular nearest neighbor peaks in gHHinter(r), gOH inter(r), and gOOinter(r) are diffuse compared with the ambient ones. The nearest neighbor O⋯O distance (3.3 Å) and its coordination number (2.6) were determined from the observed gOO inter(r). These results indicate that the orientational correlation between neighboring water molecules is considerably lost in low-density supercritical water. Small clusters involving a few water molecules are preferentially formed in low-density supercritical water, which is consistent with results obtained by previous IR and NMR studies. © 2008 American Chemical Society.

    DOI: 10.1021/jp711434n

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  • A new analysing approach for the structure of density fluctuation of supercritical fluid 査読

    T. Sato, M. Sugiyama, M. Misawa, S. Takata, T. Otomo, K. Itoh, K. Mori, T. Fukunaga

    Journal of Physics Condensed Matter   20 ( 10 )   2008年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Large scale structural evolution of supercritical carbon dioxide along the isotherm at 32 °C was investigated with small-angle neutron scattering. The maximum of the density fluctuation, the so-called 'ridge', was confirmed with Ornstein-Zernike analysis. To investigate the structural change in more detail, the molecular distribution over a large domain was determined with a newly developed reverse Monte Carlo method. From the molecular distribution obtained, the pair distribution function and cluster-size distribution can be calculated. With increasing density of carbon dioxide, the cluster size increases monotonically, whereas the pair distribution function for the range of sizes shorter than 10shows a monotonic decrease. From this result, itis suggested that the structural change along the isotherm is caused by the change of balance between growth of clusters and increase of the average density. © IOP Publishing Ltd.

    DOI: 10.1088/0953-8984/20/10/104203

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  • The structure of manganese dioxide and position of proton studied by neutron diffraction with isotopic substitution 査読

    Cédric Pitteloud, Miki Nagao, Keiji Itoh, Ryoji Kanno

    Journal of Solid State Chemistry   181 ( 3 )   467 - 472   2008年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The position of proton inside manganese dioxide, γ-MnO2, was studied by the total neutron-scattering technique using H/D isotopic substitution. The first-order difference was obtained by subtracting the results for the two different isotopic compositions and obtaining the weighted sum of partial structure factors and radial distribution functions related to the structure around hydrogens. The deuterium-substituted γ-MnO2 was prepared by de-intercalation of the proton via an oxidative treatment prior to re-intercalation with deuterium. The proton occupied two different positions with the H-O length of 1.0 and 1.9 Å, which corresponds to the 'Ruetschi' and 'Coleman' protons, respectively. The former protons situated in the Mn4+ vacant site and the latter in the tunnel centered in an oxygen octahedron. The isotopic substitution technique and the structure around protons are discussed in details. © 2007 Elsevier Inc. All rights reserved.

    DOI: 10.1016/j.jssc.2007.11.030

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  • Structural evolution of human recombinant αB-crystallin under UV irradiation 査読

    Masaaki Sugiyama, Noriko Fujii, Yukio Morimoto, Sakie Kurabayashi, Martin E. Vigild, Tatsuo Nakagawa, Takashi Sato, Keiji Itoh, Kazuhiro Mori, Toshiharu Fukunaga

    Biomacromolecules   9 ( 2 )   431 - 434   2008年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    External stresses cause certain proteins to lose their regular structure and aggregate. In order to clarify this abnormal aggregation process, a structural evolution of human recombinant αB-crystalhn under UV irradiation was observed with in situ small-angle neutron scattering. The abnormal aggregation process was identified to fall in three time zones: incubation, aggregation, and saturation. During the incubation time, the size of aggregates was almost unchanged but a deformation in the local structure was developing. After the incubation time, abnormal aggregation proceed. When the volume of the aggregates reached around twice the size as that of the initial aggregates, the aggregation rate slowed down, which marked the onset of saturation. © 2008 American Chemical Society.

    DOI: 10.1021/bm7004802

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  • Structural study of (Li2S)(50)(GeS2)(50) glass by X-ray and neutron diffraction 査読

    Keiji Itoh, Masashi Sonobe, Masaaki Sugiyama, Kazuhiro Mori, Toshiharu Fukunaga

    JOURNAL OF NON-CRYSTALLINE SOLIDS   354 ( 2-9 )   150 - 154   2008年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    (Li2S)(50)(GeS2)(50) glass was characterized by high-energy X-ray diffraction. The results were compared with previous neutron diffraction data. Moreover, Reverse Monte Carlo (RMC) modeling was performed using the X-ray and neutron data in order to obtain a three-dimensional structural model. The RMC model showed that the Ge-S framework structure was formed mainly by the connection of corner-sharing GeS4 tetrahedra. Furthermore, many lithium ions were coordinated by three non-bridging sulfurs and one bridging sulfur. (C) 2007 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jnoncrysol.2007.07.033

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  • Characterization of hydrogen absorption/desorption states on lithium-carbon-hydrogen system by neutron diffraction 査読

    Hiroki Miyaoka, Keiji Itoh, Toshiharu Fukunaga, Takayuki Ichikawa, Yoshitsugu Kojima, Hironobu Fuji

    Journal of Applied Physics   104 ( 5 )   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The nanostructural hydrogenated graphite (Cnano Hx) was synthesized from graphite by ball milling under hydrogen (H2) atmosphere. In this product, characteristic hydrogenated states in the form of polarized hydrocarbon groups (_CH,_C H2, and_C H3) are realized in the nanoscale. By synthesizing the composite of Cnano Hx and lithium hydride (LiH), known as the Li_C_H system, hydrogen was desorbed at 350 °C, which is a lower temperature compared to the decomposition temperature of each component. It is considered that this hydrogen desorption would be induced by destabilization of each hydrogen absorbed state due to an interaction between the polarized C_H groups in Cnano Hx and LiH. Therefore, in order to understand the hydrogen absorption/desorption mechanism of the Li_C_H system, it is an important issue to investigate the change in the C_H groups during hydrogen absorption/desorption reactions in the composite. The correlations among atoms contained in this composite are examined by neutron diffraction measurements, where the protium/deuterium (H/D) isotopic substitution was used to clarify the location of hydrogen atoms in this composite. Some C_D and Li_D correlations are found from the radial distribution function [RDF (r)] obtained by the neutron diffraction for the Cnano Dx and LiD composite. After dehydrogenation, C_C triple bond and Li_C bond, ascribed to lithium carbide (Li2 C2), are observed. Furthermore, the RDF (r) corresponding to rehydrogenated composite indicates the presence of not only the Li_D correlation but also the C_D one. © 2008 American Institute of Physics.

    DOI: 10.1063/1.2956504

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  • Refractive index calculation using the structural properties of La 4Ti9O24 glass 査読

    Yasutomo Arai, Keiji Itoh, Shinji Kohara, Jianding Yu

    Journal of Applied Physics   103 ( 9 )   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A high refractive index of 2.231±0.001 at 1313 nm is achieved in a colorless, transparent spherical La4 Ti9 O24 glass that was prepared by using an aerodynamic levitation furnace. We also investigate the origin of the high refractive index based on the Lines theory. The physical parameters necessary for the theoretical calculations are the averaged nearest-neighbor Ti-O and La-O distances that are deduced by neutron and synchrotron x-ray diffraction measurement and the partial molar volumes of TiO2 and LaO1.5 in the glass. The sum of the calculated TiO2 and LaO1.5 susceptibilities provides a La4 Ti9 O24 glass refractive index of 2.244. This is very close to the experimental refractive index of the glass. In addition, the theoretical calculation results suggest that the oxygen fivefold Ti (TiO5) cluster produces greater susceptibilities than the sixfold Ti (TiO6) cluster in the glass. © 2008 American Institute of Physics.

    DOI: 10.1063/1.2903544

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  • Phonon dispersion of metallic glass CuZr2 査読

    S. Nakashima, Y. Kawakita, T. Otomo, R. Suenaga, R. Baron, S. Tsutsui, S. Kohara, S. Takeda, K. Itoh, H. Kato, T. Fukunaga, M. Hasegawa

    Journal of Physics: Conference Series   92 ( 1 )   2007年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Institute of Physics Publishing  

    Collective dynamics of metallic glass CuZr2 has been studied in the first pseudo Brillouin zone using high-resolution inelastic X-ray scattering. Acoustic-like longitudinal propagating excitations were observed and the dispersion relation was determined. In addition of longitudinal mode, transverse mode with half excitation energy contributes to medium energy-transfer region. © 2007 IOP Publishing Ltd.

    DOI: 10.1088/1742-6596/92/1/012136

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  • Reverse Monte Carlo modeling of atomic configuration for amorphous materials 査読

    Toshiharu Fukunaga, Keiji Itoh, Kazuhiro Mori, Masaaki Sugiyama

    Solid State Phenomena   127   51 - 56   2007年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:Trans Tech Publications Ltd  

    Reverse Monte Carlo (RMC) modeling, based on diffraction data, was applied to various kinds of amorphous materials to visualizing the three-dimensional atomic arrangement and to elucidate topological characteristics. For an as-grown amorphous carbon nanocoil, it could be clarified that graphene sheets are winding and the regular ABAB... stacking is lost and the configuration gradually changes to the hexagonal network with great regularity through heat treatment. Voronoi analysis of the RMC model could characterize the atomic configurations for NiZr2 and CuZr2 metallic glasses. The Zr environments are very similar in the two systems, but there are marked differences between the polyhedra around Ni and Cu atoms. The polyhedra around Ni atoms are dominated by prismatic-like polyhedra. In contrast, icosahedron-like polyhedra are preferred for Cu.

    DOI: 10.4028/3-908451-33-7.51

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  • Investigation of stability of the Zr-Ni-Al bulk amorphous phase from local atomic arrangements of the relevant crystals

    Sakura Nakano, Tsunehiro Takeuchi, Kazuo Soda, Masashi Hasegawa, Uichiro Mizutani, Hirokazu Sato, Keiji Itoh, Toshiharu Fukunaga

    Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy   53 ( 1 )   100 - 106   2006年1月

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    掲載種別:研究論文(学術雑誌)  

    Stability of the Zr-Ni- Al bulk metallic glass (BMG) was investigated by making full use of its relevant crystals. The local atomic arrangements (characteristic atomic clusters) commonly existing in the BMG and its relevant crystals were identified by the experimentally determined radial distribution functions. We found that the local atomic arrangements of the BMG were characterized by the prism clusters with a transition element, Zr or Ni, in their center and the Kasper polyhedrons about an Al atom. Internal energy of these clusters was investigated by combinational use of the DVXα cluster calculation and the high-resolution photoemission spectroscopy. The prism clusters about the transition metal elements were confirmed to possess a low internal energy. We propose, as a consequence of present analyses, that the Zr-Ni-Al BMG is stabilized by the low internal-energy of the clusters and the large entropy caused by the freedom in the bond-direction between the clusters.

    DOI: 10.2497/jjspm.53.100

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  • The design of the neutron total scattering spectrometer for hydrogenous materials at J-PARC-JSNS 査読

    Kentaro Suzuya, Yasuo Kameda, Toshiya Otomo, Koji Yoshida, Keiji Itoh, Toshiharu Fukunaga, Masakatsu Misawa

    Journal of Neutron Research   13 ( 1-3 )   123 - 128   2005年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The design, performance, philosophy, lessons learned and advantages of the neutron total scattering spectrometer for hydrogenous materials, FAST, under consideration for the J-PARC-JSNS, are described. In particular, novel instrumentation concept such as the small fractional scattered neutron flight path, γ = L2/(L1 + L2)
    where L1 is the incident flight path, moderator to sample, L2 is the scattered neutron flight path from sample to detector, is presented and their expected performance at the JSNS is considered. © 2005 Taylor &amp
    Francis Ltd.

    DOI: 10.1080/10238160412331299898

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  • Pulsed neutron diffraction of phosphorous acid and its aqueous solution with inactivation capability of activated oxygen 査読

    Y. Iwadate, Y. Tani, K. Fukushima, M. Misawa, T. Fukunaga, K. Itoh, T. Nakazawa

    Journal of Neutron Research   13 ( 1-3 )   139 - 144   2005年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Pulsed neutron diffraction was carried out to analyze an intramolecular structure of D3PO3 and an orientational characteristic of adjacent molecules in D3PO3-nD2O (n = 0
    1 and 20) solutions by using the high intensity total scattering spectrometer in High Energy Accelerator Research Organization (KEK) at Tsukuba, Japan. The radial distribution method and the correlation method were employed for the analysis of structural parameters such as interatomic distances, coordination numbers and temperature factors, being consulted with those by simulations. The intramolecular structure of the phosphorous acid in the liquid state did not differ much from that in the crystalline state. In the liquid phosphorous acid, two intramolecular P-O bonds were recognized, the shorter P-O bond being assigned to the P-O double bond and the longer P-O to the single bond. On addition of heavy water, the coordination numbers of the intramolecular P-O correlations, i.e. both the shorter P-O double bond and the longer P-O single bond, increased a little. © 2005 Taylor &amp
    Francis Ltd.

    DOI: 10.1080/10238160412331299582

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  • Structural properties of Fe-doped lanthanum gallate

    Kazuhiro Mori, Toshiharu Fukunaga, Koji Shibata, Kenji Iwase, Stefanus Harjo, Akinori Hoshikawa, Keiji Itoh, Takashi Kamiyama, Toru Ishigaki

    Physica B: Condensed Matter   352 ( 1-4 )   147 - 155   2004年10月

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    掲載種別:研究論文(学術雑誌)  

    Structural characteristics of Fe-doped LaGaO were studied by differential scanning calorimeter, neutron and high-temperature X-ray powder diffraction measurements. It was found that a phase transition temperature increases in proportion to an amount of Fe. The crystal structure could be described as a low-temperature orthorhombic phase (Pnma) and a high-temperature rhombohedral one (R3c), respectively. Lattice parameters and bond lengths between M (=Ga/Fe) and O are monotonically expand with increasing Fe-content on both orthorhombic and rhombohedral phases. This means that a substitution of Ga with Fe leads to an electronic configuration of t e (high-spin state, HS). © 2004 Elsevier B.V. All rights reserved. 3-δ 2g g 3+ 3+ 3 2

    DOI: 10.1016/j.physb.2004.07.004

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  • Inelasticity effect on neutron scattering intensities of the Null-H2O 査読

    Y. Kameda, M. Sasaki, T. Usuki, T. Otomo, K. Itoh, K. Suzuya, T. Fukunaga

    Journal of Neutron Research   11 ( 3 )   153 - 163   2003年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Time-of-flight (TOF) neutron scattering measurements have been carried out for liquid null-H2O, in which the average coherent scattering length of hydrogen atoms is zero. In order to determine the inelasticity effect depending on both the scattering angle and the neutron flight path ratio, γ [=ls=/ls(l0+ls
    l0 and ls denote the moderator-sample and sample-detector distances, respectively], neutron scattering measurements have been performed using three neutron spectrometers, HIT-II, RAT, and SWAN, installed at KENS, Tsukuba, Japan. The self-scattering intensity for the null-H2O was derived by subtracting the known O-O partial structure factor from the observed scattering cross-section. It has been revealed that the magnitude of the inelasticity distortion involved in the self-scattering term is still significant even at a smaller scattering angle than that expected from the first-order inelasticity correction formulas proposed in the literature. The inelasticity distortion in the self-scattering term is found to be preferably reduced by applying the small flight path ratio. An empirical but useful correction procedure for the inelasticity effect is developed using the self-scattering intensities observed for the null-H2O. The present correction procedure is applied to the scattering cross-section observed for aqueous 3mol% alanine solution which involves 20% H of exchangeable hydrogen atoms, and to the first-order difference function ΔH(Q) observed for 4 mol% lithium benzoate heavy water solutions in which H/D isotopic substitution has been applied for benzyl-hydrogen atoms within the benzoate ion. The results indicate that the present inelasticity correction procedure works satisfactorily for the scattering intensity from the aqueous solution containing H atoms. © 2003 Taylor &amp
    Francis Ltd.

    DOI: 10.1080/10238160310001657817

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MISC

  • X-Ray and neutron diffraction studies of atomic scale structures of crystalline and amorphous TbFe2Dx

    Keiji Itoh, Kazuyuki Kanda, Kiyoshi Aoki, Toshiharu Fukunaga

    Journal of Alloys and Compounds   348 ( 1-2 )   167 - 172   2003年1月

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    記述言語:英語  

    Both X-ray and neutron diffraction techniques were employed in order to elucidate short-range structures of crystalline (c-)TbFe2D3.8 and amorphous (a-)TbFe2Dx (x = 3.0, 2.0) prepared by deuterium absorption of the C15 Laves phase compound TbFe2. Interatomic distances and coordination numbers were derived from the radial distribution functions, RDF(r)s. The RDF(r)s observed by X-ray diffraction indicated that c-TbFe2D3.8 adopts a rhombohedral structure, but there is a little difference in the arrangement of metal atoms between the original C15 Laves phase c-TbFe2 and the rhombohedral c-TbFe2D3.8. In contrast, our results indicated that there is a large difference in the arrangement of metal atoms between c-TbFe2 and a-TbFe2Dx (x = 3.0, 2.0) and there are clusters of Fe and Tb atoms in a-TbFe2Dx (x = 3.0, 2.0). RDF(r)s observed by the neutron diffraction indicated that the D atoms occupy tetrahedral sites consisting of 2Tb + 2Fe in c-TbFe2D3.8, while they occupy sites consisting of 4Tb, 3Tb + 1Fe and 2Tb + 2Fe in a-TbFe2Dx (x = 3.0, 2.0). © Elsevier Science B.V. All rights reserved.

    DOI: 10.1016/S0925-8388(02)00842-3

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  • Structure of amorphous P-Se prepared by mechanical alloying

    K. Itoh, M. Misawa, T. Fukunaga

    Journal of Non-Crystalline Solids   312-314   561 - 565   2002年10月

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    記述言語:英語  

    The short- and medium-range structures of amorphous P1-xSex (x = 0.6, 0.8) synthesized by mechanical alloying (MA) have been investigated by time-of-flight neutron diffraction. The first diffraction peak, near Q = 12 nm-1 in the structure factor, S(Q), which is strongly related to the medium range order, is smaller in height and broader in width than that for amorphous P1-xSex (x = 0.6, 0.8) prepared by liquid quenching. The formation of the medium-range order is restrained when the amorphous P-Se is synthesized by MA. © 2002 Elsevier Science B.V. All rights reserved.

    DOI: 10.1016/S0022-3093(02)01772-6

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  • Short range structures of amorphous Se-Te prepared by mechanical alloying

    K Itoh, M Misawa, T Fukunaga

    JOURNAL OF NON-CRYSTALLINE SOLIDS   293   575 - 579   2001年11月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

    The time-of-flight neutron scattering measurement was employed in order to elucidate the short range structures for a series of amorphous Se100-xTex (x = 0 similar to 20) mixtures synthesized by mechanical alloying (MA). The first peak in the radial distribution functions was resolved into two Gaussian peaks, which correspond to the Se-Se and Se-Te correlations, respectively. Amorphous Se prepared by MA has a lot of dangling bonds. In contrast, for the Se100-xTex samples, Te atoms are preferentially bonded with the dangling bonds of Se atoms with increasing Te concentration and, consequently, a twofold chain structure is formed. (C) 2001 Elsevier Science B.V. All rights reserved.

    DOI: 10.1016/S0022-3093(01)00780-3

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  • Neutron diffraction of amorphous Se-Te prepared by MA

    K. Itoh, M. Misawa, T. Fukunaga

    Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy   48 ( 9 )   806 - 809   2001年

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    記述言語:日本語   出版者・発行元:Funtai Funamtsu Yakin Kyokai/Japan Soc. of Powder Metallurgy  

    Amorphous Se100-xTex powders (x = 0, 5, 10, 15 and 20) have been produced by mechanical alloying (MA). The time-of-flight neutron scattering measurement was employed in order to elucidate the short range structures for these powders. Well-resolved first peak in radial distribution functions can be decomposed into two Gaussian peaks, which correspond to the Se-Se and Se-Te correlations. The coordination number teaches us that amorphous Se has a lot of dangling bonds due to broken of Se-Se bond by milling. However, the compositional changes of the coordination numbers of Se-Se and Se-Te pairs for Se-Te powders imply that Te atoms are bonded to the edge of Se chain molecules and the twofold chain structure is built up with increasing Te content.

    DOI: 10.2497/jjspm.48.806

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  • メカニカルアロイングにより作製されたアモルファスSe-Teの構造(共著)

    ITOH K, MISAWA M, FUKUNAGA T

    Journal of Non-Crystalline Solids   293/295   575 - 579   2001年

  • Neutron diffraction of liquid Sn-Se system

    K Itoh, K Maruyama, M Misawa, S Tamaki

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   69 ( 6 )   1717 - 1722   2000年6月

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    記述言語:英語   出版者・発行元:PHYSICAL SOC JAPAN  

    The time-of-flight neutron scattering measurements have been carried out for liquid Sn-Se system. A distinct change in structural properties has been observed between Sn70Se30 and Sn60Se40, composition of which corresponds to that of maximum of the miscibility gap. The atomic configuration of liquid SnSe have been compared to that of molten NaCl. It is found that the bonding nature between Sn and Se in liquid SnSe is ionic rather than covalent. A small but apparent pre-peak at Q = 1.2 Angstrom(-1) in the structure factor for liquid SnSe2 is found above the melting point. It suggests that the network structure remains after melting. The intensity of this pre-peak decreases with increasing temperature, indicating that the network structure is destroyed.

    DOI: 10.1143/JPSJ.69.1717

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  • Ionic and Electronic Conductions in Liquid Metal-Charcogen System.

    Journal of Non-Crystalline Solids   250/252 ( Pt.1 )   336 - 339   1999年

  • Magnetic susceptibility in liquid In-Se system

    K Itoh, T Usuki, S Tamaki

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   67 ( 9 )   3240 - 3243   1998年9月

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    記述言語:英語   出版者・発行元:PHYSICAL SOC JAPAN  

    The magnetic susceptibility of the liquid In1-xSex system have been measured as functions of concentration and temperature. The magnetic susceptibility of the system shows a broad diamagnetic maximum near x=0.58. This behaviour corresponds to the concentration variation of electronic conductivity reported previously and supports our previous suggestion of the valence fluctuation of In ions. By using the data of magnetic susceptibility with known electronic conductivity and thermoelectric power data, the density of state N(E) have been determined and the diamagnetic susceptibility due to ion core, chi(d), has also been obtained. The obtained value of chi(d) suggests the occurrence of monovalent In ion near the composition x=0.58.

    DOI: 10.1143/JPSJ.67.3240

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  • (6)Electronic and Ionic Conductions in Liquid Cu-Se system(共著)

    Keiji Itoh, Takeshi Usuki, Shigeru Tamaki

    Journal of the Physical Society of Japan   67 ( 10 )   3512 - 3516   1998年

  • 液体In-Se系の磁化率

    Journal of the Physical Society of Japan   67 ( 9 )   3240 - 3243   1998年

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  • 液体In-Se系のイオン伝導と電子的性質

    Journal of the Physical Society of Japan   67 ( 7 )   2415 - 2420   1998年

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  • (4)Ionic conduction and electronic properties in liquid In-Se system(共著)

    Keiji Itoh, Takesi Usuki, Shigeru Tamaki

    Journal of the Physical Society of Japan   67 ( 7 )   2415 - 2420   1998年

  • NEUTRON-DIFFRACTION STUDY OF LIQUID (TL1/2PB1/2)-X (X-TE,SE) SYSTEMS

    T USUKI, O UEMURA, K ITOH, Y KAMEDA

    PHYSICA B   213   555 - 557   1995年8月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

    Neutron diffraction measurements have been carried out on liquid (TI1/2Pb1/2)(1-y)X(y)(X:Te,Se) systems which exhibit a typical compound-forming behaviour at y = 3/7. Radial distribution analysis at y = 3/7 has indicated that the bonding nature of T1-X and Pb-X is more or less ionic, as expected from the previous result of electronic properties. In order to investigate the difference in electronic behaviour between these two liquid systems in the chalcogen rich region, we derive the X-X partial distribution function g(X-X)(r), assuming that each partial function at y &gt; 3/7 is independent of the alloy composition. g(Se-Se)(r) has a well-resolved first peak at r similar to 0.230 nm, suggesting that covalent Se-Se bonds appear in the Se rich region. On the other hand, g(Te-Te)(r) is somewhat structureless, although the first peak is included in the covalent region. The whole functional form of both g(X-X)(r) is roughly similar to that of g(r) in pure liquid Te or Se.

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  • ELECTRONIC AND STRUCTURAL-PROPERTIES OF THE LIQUID (TL1/2PB1/2)-SE SYSTEM

    T USUKI, K ITOH, S AITA, Y KAMEDA, O UEMURA

    PHYSICA STATUS SOLIDI B-BASIC RESEARCH   187 ( 1 )   157 - 168   1995年1月

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    記述言語:英語   出版者・発行元:AKADEMIE VERLAG GMBH  

    The electrical conductivity, magnetic susceptibility, and thermoelectric power in the liquid (Tl1/2Pb1/2)-Se system are measured over wide temperature and composition ranges. It is observed that the electrical conductivity in the system sharply falls near the stoichiometric composition of Tl2Pb2Se3 and the magnetic susceptibility has a diamagnetic maximum at this composition, where the thermoelectric power changes its sign. In addition, the DTA investigation shows that the liquidus temperature of the system has a maximum around this composition. These results suggest that a short-range order appears around the composition of Tl2Pb2Se3 in the liquid (Tl1/2Pb1/2)-Se system. The delocalized electron analysis using both susceptibility and conductivity data suggests that the bonding nature of liquid Tl2Pb2Se3 is rather ionic. The radial distribution study by neutron diffraction also exhibits that the first peak position of g(r) for liquid Tl2Pb2Se3 is located near the ionic bond distance of metal and chalcogen atoms. On the other hand, covalent Se-Se bonds are formed in the Se-rich composition range.

    DOI: 10.1002/pssb.2221870115

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  • 液体(Tl<sub>1/2</sub>Pb<sub>1/2</sub>)-Se系の電子的性質と構造

    USUKI T, ITOH K, AITA S, KAMEDA Y, UEMURA O

    European Conference on Physics of Magnetism 2002   187 ( 1 )   157 - 168   1995年

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共同研究・競争的資金等の研究

  • 水素吸蔵合金の中性子回析

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  • 非晶質系の中性子回析

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  • Neutron Diffraction of Hydrogen Absorbing Alloys

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  • Neutron Diffraction of Non-Crystalline System.

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