2024/02/01 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

所属学協会

 

論文

  • Deuterium occupation of interatomic hole sites in Ni 67Zr33 amorphous alloy 査読 国際共著

    Journal of Alloys and Compounds   961   171094   2023年10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)  

    DOI: 10.1016/j.jallcom.2023.171094

  • Deuterium occupation of interatomic hole sites in Ni67Zr33 amorphous alloy

    K. Itoh, J. Saida, E.R. Barney, A.C. Hannon

    Journal of Alloys and Compounds   961   171094 - 171094   2023年10月

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    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.2023.171094

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  • Structural study of Li2S-GeS2 glasses: Ge S network and local environment of Li 査読

    Keiji Itoh

    Solid State Ionics   383   115986 - 115986   2022年10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 BV  

    DOI: 10.1016/j.ssi.2022.115986

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  • 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  

    The structure of Cu67Zr33 amorphous alloy was investigated in terms of packing density and free volume by using neutron, x-ray diffraction and reverse Monte Carlo (RMC) modelling. The RMC model was analysed by a method of decomposing the three-dimensional atomic configuration into fundamental polyhedral units (termed as 'holes' referencing the Bernal's works) of which faces are all triangles consisting of chemical bonds. Not only tetrahedral and octahedral holes but also other larger holes were identified. Moreover, the atomic packing fractions and free volumes in the respective polyhedral holes were evaluated with reference to those for the corresponding crystal structures. The results show that the distribution of free volumes for the larger holes can be described by the exponential function assuming that there are no energetic interactions between each other. On the other hand, the local structural fluctuations due to densely and loosely packed tetrahedral holes were observed, leading to the negative free volume spaces.

    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 Zr50Cu40Al10 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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  • Neutron Diffraction Study of Isotope Enriched Glassy Sm4Ti9O24 査読

    JPS Conference Proceedings   8   031007   2015年

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    記述言語:英語   掲載種別:研究論文(研究会,シンポジウム資料等)  

    DOI: 10.7566/JPSCP.8.031007

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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   87 - 89   2010年1月

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    記述言語:英語   出版者・発行元:Physical Society of Japan  

    Time-of-flight neutron powder diffraction (TOF-NPD) and synchrotron X-ray powder diffraction (SXPD) experiments were carried out to study the crystal structure of 7Li isotope enriched 7Li7P3S11glass ceramics, which is a lithium superionic conductor. Combined X-ray/neutron Rietveld refinement informed us precise atomic coordinates, especially lithium. Furthermore, a network of neighboring Li+cations was visualized in the crystal structure of Li7P3S11with the triclinic system (space group: <italic>P</italic><overline>1</overline>) in order to predict the diffusion pathway of Li+cations.

    DOI: 10.1143/JPSJS.79SA.87

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  • 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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  • 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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  • 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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  • Assembly State of Proteasome Activator 28 in an Aqueous Solution as Studied by Small-Angle Neutron Scattering

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

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   78 ( 12 )   2009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:PHYSICAL SOC JAPAN  

    The characterization of quaternary structures of proteins in solution remains challenging, especially for those undergoing dynamic changes. Small-angle neutron scattering (SANS) is a potentially powerful method for addressing this issue with little perturbation resulting from irradiation damage. However, it is usually difficult to determine the three-dimensional (3D) structure of protein complexes at the atomic level on the basis of only SANS data. To cope with this difficulty, we developed a novel approach combining 3D homology modeling with SANS profile simulation, in which whole simulated SANS profiles were examined together with experimental SANS data. We herein demonstrate the feasibilty of our strategy using proteasome activator 28 (PA28) as a model system. PA28 is a hetero-oligomeric protein composed of homologous alpha- and beta-subunits. Although the crystal structure of the homoheptameric ring of alpha-subunits (PA28 alpha(7)) has been reported, the physiologically relevant hetero-oligomeric structure remains to be elucidated. On the basis of the PA28 alpha(7) structure, we performed homology modeling to build hypothetical quaternary structures of the PA28 hetero-oligomer. By analyzing the SANS data of a PA28 mutant lacking a mobile loop in its alpha-subunit, we successfully revealed that alpha- and beta-subunits form heteroheptameric rings, about half of which are stacked back to back to form a double-ring structure. Thus, our SANS approach provides in-depth information on the assembly states of protein subunits in aqueous solutions.

    DOI: 10.1143/JPSJ.78.124802

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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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  • Comprehensive structural study of glassy and metastable crystalline BaTi<inf>2</inf>O<inf>5</inf>

    Jianding Yu, Shinji Kohara, Keiji Itoh, Shunsuke Nozawa, Satoru Miyoshi, Yasutomo Arai, Atsunobu Masuno, Hiraki Taniguchi, Mitsuru Itoh, Masaki Takata, Toshiharu Fukunaga, Shin Ya Koshihara, Yoshihiro Kuroiwa, Shinichi Yoda

    Chemistry of Materials   21 ( 2 )   259 - 263   2009年1月

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    掲載種別:研究論文(学術雑誌)  

    The structures of glassy and metastable crystalline BaTi2O5 fabricated by the containerless method were comprehensively investigated by combined X-ray and neutron diffractions, XANES analyses, and computer simulations. The three-dimensional atomic structure of glassy BaTi 2O5 (g-BaTi2O5), simulated by Reverse Monte Carlo (RMC) modeling on diffraction data, shows that extremely distorted TiO5polyhedra interconnected with both corner- and edge-shared oxygen formed a higher packing density structure than that of conventional silicate glass linked with only corner-sharing of SiO4 polyhedra. In addition, XANES measurement revealed that five-coordinated TiO5 polyhedra were formable in the crystallized metastable α- and β-BaTi2O5 phases. The structure of metastable β-BaTi2O5 was solved by ab initio calculation, and refined by Rietveld refinement as group Pnma with unit lattices a = 10.23784(4) A, b = 3.92715(1) A, c = 10.92757(4) A. Our results show that the glass-forming ability enhanced by containerless processing, not by "strong glass former", fabricated new bulk oxide glasses with novel structures and properties. © 2009 American Chemical Society.

    DOI: 10.1021/cm802483w

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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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  • 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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  • 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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  • 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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  • 回折実験とモデルからみた金属ガラスの構造

    福永俊晴, 伊藤恵司, 大友季哉

    まてりあ   47   17 - 22   2008年

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    記述言語:日本語  

    DOI: 10.2320/materia.47.17

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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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  • Structure of amorphous CeFe2D3.9 observed by X-ray and neutron diffraction 査読

    Keiji Itoh, Kiyoshi Aoki, Masaaki Sugiyama, Kazuhiro Mori, Toshiharu Fukunaga

    JOURNAL OF ALLOYS AND COMPOUNDS   446   19 - 22   2007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)   出版者・発行元:ELSEVIER SCIENCE SA  

    X-ray and neutron diffraction measurements have been performed on amorphous (a-)CeFe2D3.9 prepared by deuterium absorption of the C15 Laves phase compound CeFe2. Comparison of previous results for amorphous (a-)TbFe2D3.9 indicates differences in the location of deuterium atoms. A three-dimensional structural model is proposed for a-CeFe2D3.9 on the basis of reverse Monte Carlo (RMC) simulation with X-ray and neutron data. Marked differences in the location of deuterium atoms were found between a-TbFe2D3.9 and a-CeFe2D3.9. (C) 2006 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jallcom.2006.12.010

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  • Voronoi analysis of the structure of Ni-Zr-Al ternary metallic glass 査読

    T. Fukunaga, K. Itoh, T. Otomo, K. Mori, A. Sugiyama, H. Kato, A. Hasegawa, A. Hirata, Y. Hirotsu, A. C. Hannon

    MATERIALS TRANSACTIONS   48 ( 7 )   1698 - 1702   2007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)   出版者・発行元:JAPAN INST METALS  

    Ni-Zr metallic glasses have been recognized to be unstable in comparison with Cu-Zr metallic glasses. An analysis of Voronoi polyhedra in the RMC simulations based on the diffraction data could characterize the atomic configurations around Ni and Cu atoms. The polyhedra around Ni atoms are dominated by trigonal prisni-like, Archimedian antiprism-like, and similar polyhedra. In contrast. icosahedron-like polyhedra are preferred for Cu. The Ni-Zr glasses have been reported to stabilize by adding Al. Therefore, in this work, the analysis of Voronoi polyhedra around Ni, Zr and Al atoms for Ni25Zr60Al15 ternary metallic glass was carried out in order to clarify the difference between the atomic structures for the binary and ternary metallic glasses. Trigonal prism-like, Archimedian antiprism-like and similar polyhedra, which are dominated in the Ni-Zr metallic glasses, decreased in number by adding Al to the Ni-Zr system. On the contrary, the number of icosaliedron-like polyhedra was found to increase. The results apparently indicate that the addition of Al into Ni-Zr binary system promote the formation of icosahedron-like polyhedra in the structure. Therefore, from these results. we can easily recognize that icosahedron-like polyhedra play an important role to stabilize the structure of metallic glasses.

    DOI: 10.2320/matertrans.MJ200750

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  • Structural analysis of polyelectrolyte film absorbing metal ion by SAXS utilizing with X-ray anomalous dispersion effect 査読

    Masaaki Sugiyama, Takao Mitsui, Takashi Sato, Yoshinori Akai, Yuji Soejima, Hiroshi Orihara, Yang-Ho Na, Keiji Itoh, Kazuhiro Mori, Toshiharu Fukunaga

    JOURNAL OF PHYSICAL CHEMISTRY B   111 ( 29 )   8663 - 8667   2007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)   出版者・発行元:AMER CHEMICAL SOC  

    A distribution of Cu ions in polyelectrolyte film (Nafion) is directly observed with a small-angle X-ray scattering (SAXS) method utilizing an X-ray anomalous dispersion effect. A partial structure factor of the Cu ions, G(AA)(q), can be derived from the SAXS profiles obtained by scanning the incident X-ray energy around the Cu K absorption edge. G(AA)(q) has two peaks, indicating that the Cu ions hierarchically distribute in Nafion film. In addition, a standard SAXS also shows that Nafion film has a hierarchical structure. These results mean that the Cu ions locate in the domain where the hydrophilic bases aggregate.

    DOI: 10.1021/jp0716076

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  • Short-range structure of beta-V2D: Pair distribution function analysis of x-ray and neutron diffraction

    Itoh K, Fukunaga T

    JOURNAL OF APPLIED PHYSICS   101 ( 12 )   2007年6月

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    記述言語:英語   出版者・発行元:AMER INST PHYSICS  

    DOI: 10.1063/1.2748349

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  • Structure of amorphous LaNi5D3.3 studied by neutron and X-ray diffraction 査読

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

    JOURNAL OF NON-CRYSTALLINE SOLIDS   353 ( 18-21 )   1975 - 1978   2007年6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  

    In situ neutron and X-ray diffraction measurements in a D-2 gas atmosphere at a constant pressure of 1 MPa were performed on amorphous LaNi5D3.3, which was prepared by mechanical alloying in a D-2 gas atmosphere. Reverse Monte Carlo (RMC) simulation based on the neutron and X-ray diffraction data was applied to construct a three-dimensional atomic arrangement of this amorphous alloy. The RMC model shows that more than 90% of the deuterium atoms occupy tetrahedral sites consisting of La and/or Ni atoms. Furthermore, the local environments around the Ni and La atoms were investigated by Voronoi polyhedral analysis of the RMC configuration of the metal atoms. The results show the presence of a number of prismatic-like polyhedra around a Ni atom. (c) 2007 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jnoncrysol.2007.02.023

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  • Atomic configuration of metal atoms in (Ti0.676Zr0.324)D-0.31 metallic glass studied by X-ray, neutron diffraction and reverse Monte Carlo modeling 査読

    K. Itoh, K. Hashi, K. Aoki, K. Mori, M. Sugiyama, T. Fukunaga

    JOURNAL OF ALLOYS AND COMPOUNDS   434   180 - 182   2007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)   出版者・発行元:ELSEVIER SCIENCE SA  

    We have obtained a three-dimensional atomic configuration in (Ti0.676Zr0.324)D-0.31 glass using the reverse Monte Carlo (RMC) modeling method with neutron and X-ray diffraction data. Voronoi polyhedral analysis for the RMC configuration of metal atoms revealed the presence of a lot of icosahedral-like clusters. (C) 2006 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jallcom.2006.08.194

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  • Shape of α-crystallin analyzed by small-angle neutron scattering 査読

    M. Sugiyama, N. Fujii, Y. Morimoto, T. Otomo, S. Takata, M. Misawa, M. Annaka, K. Itoh, K. Mori, T. Sato, S. Kurabayashi, T. Fukunaga

    Journal of Applied Crystallography   40   S200 - S204   2007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)  

    DOI: 10.1107/S0021889807006838

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  • Mixed magnetic phase in 6H-type BaFeO3-delta 査読

    Kazuhiro Mori, Takashi Kamiyama, Hisao Kobayashi, Toshiya Otomo, Kusuo Nishiyama, Masaaki Sugiyama, Keiji Itoh, Toshiharu Fukunaga, Susumu Ikeda

    JOURNAL OF APPLIED CRYSTALLOGRAPHY   40 ( SUPPL. 1 )   S501 - S505   2007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:BLACKWELL PUBLISHING  

    The magnetic state in 6H-type BaFeO3-delta at low temperature was studied using small-angle neutron scattering, positive-muon spin relaxation and magnetization measurements. These experiments demonstrate the appearance of two different types of magnetic states: an antiferromagnetic ordering with a long-range correlation and magnetic domains with a short-range correlation. The antiferromagnetic Fe spin arrangement occurs below 130 K. In contrast, the magnetic domains are formed below 170 K and the average size of the magnetic domains was estimated as similar to 124 angstrom. These results explain the discrepancy of the Neel temperatures between three measurement techniques: magnetization, neutron powder diffraction and Mossbauer measurements. Furthermore, it was found that the magnetic domains coexist with the long-range antiferromagnetic ordering below 130 K.

    DOI: 10.1107/S0021889807001653

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  • Local atomic arrangements and electronic structure of Zr-Ni-Al bulk metallic glass. -Analysis by use of the relevant crystals-

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

    Materials Science and Engineering A   448-451   599 - 604   2007年3月

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    掲載種別:研究論文(学術雑誌)  

    Internal energy of a bulk metallic glass (BMG) was investigated by making full use of its relevant crystals. The local atomic arrangements commonly existing both in the BMG and the relevant crystals were identified using experimentally determined radial distribution functions. The electronic structure of the relevant crystals was investigated by discrete variational X alpha (DVXα) cluster calculations and high-resolution photoemission spectroscopy. The present analysis on the electronic structure revealed that the simultaneous formations of characteristic cluster levels and a pseudogap at the Fermi level effectively reduce the internal energy to stabilize BMGs. © 2006 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.msea.2006.02.392

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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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  • Observation of microstructure of hydrated Ca3SiO5 査読

    K. Mori, T. Sato, T. Fukunaga, K. Oishi, K. Kimura, K. Iwase, M. Sugiyama, K. Itoh, F. Shikanai, T. Wuernisha, M. Yonemura, D. Sulistyanintyas, I. Tsukushi, S. Takata, T. Otomo, T. Kamiyma, M. Kawai

    Physica B: Condensed Matter   385   517 - 519   2006年11月

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    記述言語:英語  

    DOI: 10.1016/j.physb.2006.05.260

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  • Charge states of Ca atoms in beta-dicalcium silicate 査読

    Kazuhiro Mori, Ryoji Kiyanagi, Masao Yonemura, Kenji Iwase, Takashi Sato, Keiji Itoh, Masaaki Sugiyama, Takashi Kamiyama, Toshiharu Fukunaga

    JOURNAL OF SOLID STATE CHEMISTRY   179 ( 11 )   3286 - 3294   2006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)   出版者・発行元:ACADEMIC PRESS INC ELSEVIER SCIENCE  

    In order to study the crystal structure of beta-Ca2SiO4, time-of-flight neutron powder diffraction experiments were carried out at temperatures between room temperature (RT) and 600 degrees C. Rietveld refinement at RT has shown that beta-Ca2SiO4 is monoclinic based on P2(1)/n symmetry and two different types of Ca sites, Ca(1) and Ca(2). All interatomic distances within 3 angstrom were calculated, with the valences of Ca(1) with seven Ca-O bonds and Ca(2) with eight were estimated to be 1.87+ and 2+ by the Zachariasen-Brown-Altermatt formula (bond valence sum). Applying charge neutrality the two charge states of Ca in beta-Ca2SiO4 are [Ca(1)SiO4](2-) and Ca(2)(2+), respectively. Furthermore, the [Ca(1)SiO4](2-) unit has the shortest Ca-O distance, and its length kept constant at 2.23 angstrom at all temperatures. In the short-range structure analysis at RT, the shortest Ca-O bond was also observed in a radial distribution function. These results imply that the [Ca(1)SiO4](2-) unit has covalency on the shortest Ca-O in addition to Si-O. (c) 2006 Elsevier Inc. All rights reserved.

    DOI: 10.1016/j.jssc.2006.06.018

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  • Topological characterization of metallic glasses by neutron diffraction and RMC modeling 査読

    Toshiharu Fukunaga, Keiji Itoh, Toshiya Otomo, Kazuhiro Mori, Masaaki Sugiyama, Hidemi Kato, Masashi Hasegawa, Akihiko Hirata, Yoshihiko Hirotsu, Kiyoshi Aoki

    PHYSICA B-CONDENSED MATTER   385   259 - 262   2006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)   出版者・発行元:ELSEVIER SCIENCE BV  

    TbFe2D3.8, TbNi2D2.4, CuZr2 and NiZr2 metallic glasses have been studied to elucidate the structural characteristics by taking advantage of neutron and X-ray diffraction and using the reverse Monte Carlo (RMC) modeling based on the diffraction data. Topologically, about 98% of D atoms occupy tetrahedral sites formed by metal atoms for TbFe2D3.8 and TbNi2D2.4 metallic glasses. The Volonoi analysis of the structure of CuZr2 and NiZr2 metallic glasses was carried out to elucidate the relationship between the stability of glassy state and the atomic configuration. The prismatic-like polyhedra dominate in NiZr2 metallic glass. In contrast, the icosahedron-like polyhedra faces are preferred for constructing the structure of CuZr2 metallic glass. (c) 2006 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physb.2006.05.061

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  • Anisotropic frequency response of critical density fluctuation of NIPA gel under oscillation shear 査読

    Masaaki Sugiyama, Martin E. Vigild, Toshiharu Fukunaga, Keiji Itoh, Kazuhiro Mori, Takashi Sato, Masahiko Annaka

    PHYSICA B-CONDENSED MATTER   385   804 - 806   2006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)   出版者・発行元:ELSEVIER SCIENCE BV  

    A relation between rheology and structure of high density NIPA gel around a critical point on volume phase transition was studied by a simultaneous rheology and small-angle neutron scattering measurement. Just below the critical temperature, the NIPA gel showed softening: G' and G '' get closer (G'&gt; C'). At this temperature, the density fluctuation enhanced along the shear direction corresponding to the shear frequency but not to the shear strength. It means that this anisotropy is different from that observed in a statically stretched gel. (c) 2006 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physb.2006.06.094

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  • Structural observation of Li2S-GeS2 superionic glasses 査読

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

    PHYSICA B-CONDENSED MATTER   385   520 - 522   2006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)   出版者・発行元:ELSEVIER SCIENCE BV  

    Time-of-flight neutron diffraction measurements have been performed to investigate the structure of Li2S-GeS2 superionic glasses synthesized by mechanical alloying. The total correlation functions have the positive and the negative peaks, which correspond to Ge-S and Li-S nearest-neighbour correlations, respectively. The coordination number of S atoms around a Ge atom indicates that Ge atom is tetrahedrally coordinated by S atoms and GeS4 tetrahedra consist of not only bridging S but also non-bridging S. The coordination number of S atoms around a Li atom indicates that mobile Li ions are coordinated by three non-bridging S. (c) 2006 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physb.2006.05.261

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  • Voronoi analysis of the structure of Cu-Zr and Ni-Zr metallic glasses 査読

    T. Fukunaga, K. Itoh, T. Otomo, K. Mori, M. Sugiyama, H. Kato, M. Hasegawa, A. Hirata, Y. Hirotsu, A. C. Hannon

    INTERMETALLICS   14 ( 8-9 )   893 - 897   2006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)   出版者・発行元:ELSEVIER SCI LTD  

    The structures of Cu-Zr and Ni-Zr metallic glasses have been studied by neutron diffraction and Reverse Monte Carlo (RMC) modeling. A pre-peak at Q similar to 17 nm(-1) was observed in the structure factor, S(Q), of Ni-Zr metallic glasses, and this is associated with the Ni-Ni partial structure factor was well reproduced by the RMC modeling. An analysis of Voronoi polyhedra in the RMC simulations was used to characterise the different atomic configurations around Zr, Ni and Cu atoms. 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 trigonal prismatic-like, Archimedian antiprismatic-like, and similar polyhedra, with smaller total coordination numbers less than 10. In contrast, icosahedron-like polyhedra with total coordination numbers in excess of 1 I are preferred for Cu. (c) 2006 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.intermet.2006.01.006

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  • 中性子回折によるアモルファス合金の構造観察

    福永 俊晴, 伊藤 恵司

    日本結晶学会誌   48 ( 1 )   70 - 75   2006年2月

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    記述言語:日本語   出版者・発行元:The Crystallographic Society of Japan  

    Neutron diffraction is a powerful tool to elucidate the atomic arrangement of amorphous alloys because of characteristic scattering lengths of constituent elements. For hydrogen absorption amorphous alloys HID isotopic substitution was employed to observe the location of deuterium atoms because the neutron coherent scattering length of deuterium is large enough to observe in comparison with those of the constituent atoms. Moreover, Reverse Monte Carlo (RMC) modeling has been recognized to be an excellent method for visualizing the threedimensional atomic arrangement of amorphous alloys, based on the results of neutron and X-ray diffraction experiments. Therefore, the combination of neutron, X-ray diffraction experiments and the RMC modeling was used to clarify the topological characteristics of the structure of amorphous alloys.

    DOI: 10.5940/jcrsj.48.70

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  • 金属ガラスの構造と基礎物性(A02班)

    弘津 禎彦, 松原 英一郎, 市坪 哲, 石丸 学, 平田 秋彦, 福永 俊晴, 伊藤 恵司, 大友 季哉, 水谷 宇一郎, 竹内 恒博, 長谷川 正, 曽田 一雄, 佐藤 洋一, 森 博太郎, 李 正九, 武田 信一, 川北 至信, 小原 真司, 水野 章敏, 渡辺 匡人, 高田 昌樹, 松浦 真, 今野 一弥, 浅田 格, 櫻井 雅樹, 張 偉, 井上 明久, 垂水 竜一, 荻 博次, 平尾 雅彦, 才田 淳二, 加藤 秀実, 花田 貴, 八木 伸也, 喬 山, 山崎 仁丈

    粉体および粉末冶金   53 ( 1 )   90 - 99   2006年1月

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    記述言語:日本語   出版者・発行元:Japan Society of Powder and Powder Metallurgy  

    Investigations of atomic and electronic structures in amorphous solid and liquid states of metallic glasses are important to understand the reason for the stability of metallic glasses. For this purpose, a research division A02 was organized in the program of Grant-in-Aid for Scientific Research on Priority Areas "Materials Science of Bulk Metallic Glasses". This research division consists of four sub-groups to investigate (1) as-formed and annealed structures, (2) liquid and super-cooled liquid atomic structures, (3) liquid-solid phase transformation and (4) electronic structures and physical properties of metallic glasses. Researches of our division achieved in these three years are summarized in the following.

    DOI: 10.2497/jjspm.53.90

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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.

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  • Hydration kinetics of tricalcium silicate studied by neutron scattering 査読

    Kazuhiro Mori, Yuuya Shiraishi, Takashi Sato, Kenji Iwase, Masaaki Sugiyama, Shinichi Takata, Toshiya Otomo, Keiji Itoh, Masao Yonemura, Fumihito Shikanai, Tuerxun Wuernisha, Dyah Sulistyanintyas, Koji Oishi, Masayoshi Kawai, Takashi Kamiyama, Toshiharu Fukunaga

    TRANSACTIONS OF THE MATERIALS RESEARCH SOCIETY OF JAPAN, VOL 31, NO 3   31 ( 3 )   763 - 766   2006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:ELSEVIER SCIENCE BV  

    The hydration kinetics of tricalcium silicate (Ca3SiO5) has been studied by time-of-flight neutron powder diffraction (TOF-NPD) and time-of-flight small-angle neutron scattering (TOF-SANS). During the hydration process, the hydrated Ca3SiO5 was quantified using the additional standard method with Si, and then we could obtain the time dependence of the hydration degree of Ca3SiO5. It was validated that the hydration of Ca3SiO5 proceeds in three different stages: induction period, nucleation and growth period and diffusion-limited period. In the SANS experiments, the drastic variation in the SANS curve was observed over induction time (t(i)similar to 6 h). From these results, we point out that the hydration rate is strongly associated with the surface roughness of Ca3SiO5 arising from the creation of hydration products. Furthermore, the four-parameter equation based on the Avrami model was applied to describe the hydration kinetics of Ca3SiO5. The n-value that characterizes the hydration process was estimated as similar to 2.6.

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  • Relation between high ionic conductivity and boson peak in superionic glass 査読

    M. Arai, H. Iwase, M. Nakamura, T. Otomo, E. Kartini, K. Itoh, S. J. Levett, S. M. Bennington

    FLOW DYNAMICS   832   299 - +   2006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:AMER INST PHYSICS  

    The inelastic neutron scattering measurements of superionic glass system (AgI)(x)(Ag2S)(x)(AgPO3)(1-2x), reveal that an excess intensity around 3 meV, the so-called boson peak, increases with the dopant salt concentration x. The composition dependence of boson peak intensity has a systematic relation with ionic dc conductivity. These correlated features are discussed from the viewpoint of free spaces involved with the expansion of network structure by salt doping. Cooperative dynamical properties concerned with free spaces contribute to the enhancement of hopping probability of Ag+ ions. Successive hopping is promoted in order to keep electric neutrality, where the hopping events of charged ion microscopically violates the electric neutrality. These processes should result in the high ionic conductivity of superionic glasses.

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  • Structure characterization and lithiation mechanism of nongraphitized carbon for lithium secondary batteries 査読

    M Nagao, C Pitteloud, T Kamiyama, T Otomo, K Itoh, T Fukunaga, K Tatsumi, R Kanno

    JOURNAL OF THE ELECTROCHEMICAL SOCIETY   153 ( 5 )   A914 - A919   2006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 SOC INC  

    Structure and lithiation mechanism of the nongraphitizable carbon (hard carbon) fiber were determined by X-ray and neutron diffraction-pattern simulation, neutron small-angle scattering, and neutron total scattering techniques. The structure of the hard carbon is formed by two-dimensional graphene sheets, which are spaced by narrow interlayer space and slightly larger interlayer space, corresponding to the periodically layered region and the interlayer voids, respectively. The shape of these voids on the nanosize was characterized by a combination of ellipsoid and random branching form. The lithiation proceeded by two steps. At a shallow lithiation region, lithium intercalated into the periodically layered region and the interlayer spacing of this region expanded. At the deep lithiation stage, lithium was inserted into the interlayer nanovoid and the void size increased. The coordination numbers of the constituent ions indicated a two-dimensional graphene sheet in the whole structure; this supports the "wave" model for the hard carbon structure. Based on our X-ray and neutron scattering experiments, a new structure model and a lithiation mechanism are proposed. (c) 2006 The Electrochemical Society.

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  • Structure of nano-crystalline FeTiDx by neutron and X-ray diffraction 査読

    K Itoh, H Sasaki, HT Takeshita, K Mori, T Fukunaga

    JOURNAL OF ALLOYS AND COMPOUNDS   404   95 - 98   2005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:ELSEVIER SCIENCE SA  

    Complementary studies by neutron and X-ray diffraction were performed to elucidate the location of deuterium atoms in nano-crystalline FeTiDx. Remarkable rearrangement of the metal atoms due to the deuterium absorption was observed in the pair distribution functions, g(r), obtained by X-ray diffraction. The result indicates that disordered grain boundary is developed through the deuterium absorption. The g(r) function obtained by neutron diffraction indicates the occurrence of two types of deuterium sites located inside the grains and in the grain boundaries, respectively. The deuterium atoms in the grain boundaries occupy tetrahedral sites consisting mainly of Ti atoms. (c) 2005 Elsevier B.V. All rights reserved.

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  • Free-energy analysis of the Zr-Ni-Al bulk metallic glass from the local atomic arrangements of the relevant crystals

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

    Materials Transactions   46 ( 12 )   2791 - 2798   2005年12月

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    掲載種別:研究論文(学術雑誌)  

    Free-energy of Zr-Ni-Al bulk metallic glass (BMG) was estimated by making full use of coordination clusters in the relevant crystals. The clusters in the BMG were determined by using the BMG's experimentally determined radial distribution functions, and the electronic structure of the identified clusters was calculated by the DVXα cluster calculation. The local atomic arrangements in the Zr-Ni-Al BMG are found to be characterized by the prism clusters with Zr or Ni atom in their center and the Kasper polyhedrons about Al atoms. It was conclude, as a consequence of the present analysis, that the Zr-Ni-Al BMG are stabilized by the low internal-energy of the constituent local atomic clusters assisted by the large entropy caused by the freedom in the bond-direction between the prism clusters and the Kasper polyhedrons. © 2005 The Japan Institute of Metals.

    DOI: 10.2320/matertrans.46.2791

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  • Local structure of lead halide melts analysed by pulsed neutron diffraction 査読

    Y Iwadate, Y Seki, K Fukushima, M Misawa, T Fukunaga, K Itoh, T Nakazawa, Y Okamoto, H Matsuura, A Kajinami, N Ohtori, N Umesaki

    JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS   66 ( 2-4 )   433 - 438   2005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)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    According to the radial distribution analysis of PbCl2 melt through pulsed neutron diffraction (PND), the Cl-coordination numbers around Pb were found to be about 4, corresponding to the peak at r = 2.84 angstrom in the correlation function G(r), and to be about 2 at r = 3.40 angstrom, respectively. These two peaks were thought to form the first coordination shell. On the contrary, the Br-coordination number around Pb was estimated at about 4. Although PbCl2 and PbBr2 have the same crystal structure, the short-range structure of the melts was quite different from each other. (c) 2004 Elsevier Ltd. All rights reserved.

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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 observation and RMC Modeling for Nl-Zr and Cu-Zr metallic glasses 査読

    T Fukunaga, D Touya, K Itoh, T Otomo, K Mori, H Kato, M Hasegawa

    METASTABLE, MECHANICALLY ALLOYED AND NANOCRYSTALLINE MATERIALS   24-25   217 - 220   2005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  

    Ni-Zr and Cu-Zr metallic glasses were employed to elucidate characteristics of short and medium-range structure by neutron diffraction. The pre-peak characteristic of the medium-range order was clearly observed at Q similar to 17 nm(-1) in the structure factor, S(Q), for the Ni33.3Zr66.7, metallic glass. The reverse Monte Carlo (RMC) modeling was also carried out for elucidating the characteristics of the structure for the Ni33.3Zr66.7 and Cu33.3Zr66.7 metallic glasses. The characteristic Ni-Ni partial structure factor obtained experimentally was definitely reproduced by the RMC modeling. Moreover, it was found that the first neighbor distributions of the Ni-Ni and Ni-Zr pairs for the Ni33.3Zr66.7 metallic glass were much sharper than those of the Cu-Cu and Cu-Zr pairs for the Cu33.3Zr66.7 metallic glass. The evidence is strongly correlated with the short- and medium-range order of the structure for metallic glasses.

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  • Further understanding of reaction processes in electrolytic manganese dioxide electrodes for lithium cells 査読

    M Nagao, C Pitteloud, T Kamiyama, T Otomo, K Itoh, T Fukunaga, R Kanno

    JOURNAL OF THE ELECTROCHEMICAL SOCIETY   152 ( 7 )   E230 - E237   2005年

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    Lithium insertion in interstitial space was investigated for electrolytic manganese dioxide (EMD), gamma-MnO2, as a new cathode reaction in lithium battery. Its structure and proton dehydration mechanism were characterized by X-ray and neutron diffraction-pattern simulation. The heat-treatment process activated the EMD as insertion electrodes and caused dehydration with structural changes, which were described by modifications in stacking sequence of the ramsdellite (+R) to pyrolusite (+P), and their twinning types (-R and -P). By the heat-treatment of EMD, the -R ratio decreased and the -P increased with increasing temperature, and finally the structure transformed to +P above 400 degrees C. The void size was determined by small-angle neutron scattering and decreased with the treatment temperature. The total neutron diffraction indicated two types of protons with H-O length of 1.0 and 1.9 angstrom, which corresponds to the "Ruetschi" and "Coleman" protons, respectively. The former proton situated in the Mn4+ vacant site and the latter in the center of the tunnel. Lithium insertion properties depended on both the structures and the amount of proton. Dehydration of the Ruetschi proton without destroying interstitial space improved the lithium insertion capacities as reversible cathodes. (c) 2005 The Electrochemical Society. All rights reserved.

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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

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  • 中性子散乱によるナノ・アモルファス水素吸蔵材料中の水素の観察

    福永 俊晴, 伊藤 恵司

    まてりあ : 日本金属学会会報   43 ( 3 )   225 - 231   2004年3月

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    記述言語:日本語   出版者・発行元:The Japan Institute of Metals and Materials  

    DOI: 10.2320/materia.43.225

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  • The local structure of hydrogen storage nanocrystalline graphite by neutron scattering 査読

    Keiji Itoh, Yusuke Miyahara, Shin-Ichi Orimo, Hironobu Fujii, Takashi Kamiyama, Toshiharu Fukunaga

    Journal of Alloys and Compounds   356-357   608 - 611   2003年8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)  

    The total and inelastic neutron scattering measurements were employed in order to get more information on the local structure of nanocrystalline graphite prepared by mechanical milling under D2 gas atmosphere. In the RDF(r) for the sample after 50 h of milling, newly grown peak around 0.154 nm was found at the larger r side of the first nearest peak corresponding to the C-C correlation. The distance 0.154 nm of the C-C correlation is attributed to 4-fold bonding. Moreover, the inelastic neutron scattering peak observed in the 160-190 meV region for the samples after 20 h of milling indicates new emergence of sp3 bonding. The results apparently indicate that terminating D atoms at the edges of the nano-lattice plane of graphite create the new sp3 bonding of C atoms during the milling process under D2 gas atmosphere. © 2002 Elsevier B.V. All rights reserved.

    DOI: 10.1016/S0925-8388(02)01284-7

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  • Local structure of BaFeO3-delta studied by neutron scattering 査読

    K Mori, T Kamiyama, H Kobayashi, K Itoh, T Otomo, S Ikeda

    PHYSICA B-CONDENSED MATTER   329 ( II )   807 - 808   2003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)   出版者・発行元:ELSEVIER SCIENCE BV  

    In order to clarify local structure of 6H-type BaFeO3-delta, an atomic pair distribution function (PDF) was determined by neutron scattering experiments. Though Fe4+ concentration in BaFeO3-delta decreases below 170 K, the PDF pattern does not change at all temperatures. It indicates that the local structure around Fe ion dose not change in the decrease of Fe4+ concentration. (C) 2003 Elsevier Science B.V. All rights reserved.

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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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▼全件表示

MISC

  • 30aRE-7 高強度中性子全散乱装置(NOVA)の建設(30aRE X線・粒子線(中性子),領域10(誘電体,格子欠陥,X線・粒子線,フォノン物性))

    大友 季哉, 三沢 正勝, 鈴谷 賢太郎, 金子 直勝, 大下 英敏, 福永 俊晴, 伊藤 恵司, 森 一広, 杉山 正明, 亀田 恭男, 山口 敏男, 吉田 亨次, 川北 至信, 丸山 健二, 社本 真一, 高田 慎一, 佐藤 節夫, 武藤 豪, 鈴木 純一, 安 芳次, 仲吉 一男, 宇野 彰二, 田中 真伸

    日本物理学会講演概要集   64 ( 1 )   973 - 973   2009年3月

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

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  • 26aTH-11 CuZr_2金属ガラスのフォノン・ダイナミクス3(液体金属,領域6,金属,超低温,超伝導・密度波)

    中島 慎治, 川北 至信, 大友 季哉, 末永 亮介, BARON Alfred.Q.R., 筒井 智嗣, 武田 信一, 伊藤 恵司, 加藤 秀実, 福永 俊晴, 長谷川 正

    日本物理学会講演概要集   63 ( 1 )   783 - 783   2008年2月

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

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  • 22aTR-8 Li_2S-P_2S_5系超イオン伝導体の構造観察(超イオン導電体・イオン伝導体,領域5,光物性)

    小野寺 陽平, 伊藤 恵司, 森 一広, 杉山 正明, 大友 季哉, 福永 俊晴

    日本物理学会講演概要集   62 ( 2 )   747 - 747   2007年8月

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

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  • 関連結晶相の局所構造解析を利用したZr-Ni-Alバルクアモルファス相の安定性の解明

    中野さくら, 竹内恒博, 曽田一雄, 長谷川正, 水谷宇一郎, 佐藤洋一, 伊藤恵司, 福永俊晴

    粉体および粉末冶金   53 ( 1 )   2006年

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  • Evolution of local structure in Ag2O-TeO2 glasses with addition of Ag2O analyzed by pulsed neutron diffraction and Raman spectroscopy

    Y Iwadate, M Suzuki, T Hattori, K Fukushima, S Nishiyama, M Misawa, T Fukunaga, K Itoh

    JOURNAL OF ALLOYS AND COMPOUNDS   389 ( 1-2 )   229 - 233   2005年3月

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

    The local structure of Ag2O-TeO2 glasses was studied by time-of-flight pulsed neutron diffraction (TOF-PND) and Raman spectroscopy. The results of Raman spectroscopy indicated that TeO4 trigonal bipyramidal units (tbp) were converted to TeO3 trigonal pyramidal units (tp) by addition of Ag2O to TeO2. Furthermore in PND, the structural parameters for each atomic pair were optimized in the Q-space, and the distances of the near neighbor Te-O correlations forming tbp units and tp units in the network were estimated with some accuracy. (C) 2004 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jallcom.2004.06.093

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  • 28pWE-10 超イオン伝導性ガラスAgI-Ag_2S-AgPO_3の低エネルギー励起(過冷却液体等)(領域12)

    岩瀬 裕希, 新井 正敏, 大友 季哉, Kartini E., 伊藤 恵司, Levett S., Bennington S. M.

    日本物理学会講演概要集   59 ( 1 )   368 - 368   2004年3月

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

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  • 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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  • 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 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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  • 25aTF-10 アモルファスSe-Te合金の局所構造

    伊藤 恵司, 三沢 正勝, 福永 俊晴

    日本物理学会講演概要集   55 ( 2 )   684 - 684   2000年9月

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  • 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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  • 30p-G-5 液体Sn-Se系の中性子回折

    伊藤 恵司, 丸山 健二, 三沢 正勝, 田巻 繁

    日本物理学会講演概要集   54 ( 1 )   515 - 515   1999年3月

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    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

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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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  • 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

    Itoh Keiji, Usuki Takesi, Tamaki Shigeru

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

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    記述言語:英語   出版者・発行元:一般社団法人日本物理学会  

    Electronic and ionic conductivities and thermoelectric power of liquid In1-x–Sex system have been measured as a function of concentration and temperature. The electronic conductivity in the system shows a deep minimum near the Se composition x=0.58 and the ionic conductivity has a broad maximum at this composition, where the thermoelectric power shows a large negative maximum. The electronic conductivity and thermoelectric power were analyzed in terms of the Fermi-Dirac integrals. It is found that the shape of the density of state, N(E), changes gradually with concentration.

    DOI: 10.1143/JPSJ.67.2415

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  • Ionic Conduction and Electronic Properties in Liquid In–Se System

    Itoh Keiji, Usuki Takesi, Tamaki Shigeru

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

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    記述言語:英語   出版者・発行元:一般社団法人日本物理学会  

    Electronic and ionic conductivities and thermoelectric power of liquid In1-x–Sex system have been measured as a function of concentration and temperature. The electronic conductivity in the system shows a deep minimum near the Se composition x=0.58 and the ionic conductivity has a broad maximum at this composition, where the thermoelectric power shows a large negative maximum. The electronic conductivity and thermoelectric power were analyzed in terms of the Fermi-Dirac integrals. It is found that the shape of the density of state, N(E), changes gradually with concentration.

    DOI: 10.1143/JPSJ.67.2415

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  • Electronic and Ionic Conductions in Liquid Cu–Se System

    Itoh Keiji, Usuki Takeshi, Tamaki Shigeru

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

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    記述言語:英語   出版者・発行元:一般社団法人日本物理学会  

    Electronic and ionic conductivities of liquid Cu–Se system have been measured as a function of concentration and temperature. The electronic conductivity, σe, in the system shows a broad minimum near the composition Cu2Se and the ionic conductivity, σi, has a maximum around this composition. In Se-rich region, a change from negative to positive temperature dependence of σe and a discontinuous jump in σi have been observed at a certain temperature. The relation between the electronic and ionic conductivities have quantitatively been discussed.

    DOI: 10.1143/JPSJ.67.3512

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  • 28p-X-1 砒素-カルコゲン系液体合金の局所構造

    臼杵 毅, 伊藤 恵司, 植村 治, 亀田 恭男

    日本物理学会講演概要集   52 ( 1 )   531 - 531   1997年3月

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  • 溶融(In_<1/2>Pb_<1/2>)-Te系の構造と電子的性質

    伊藤 恵司, 臼杵 毅, 植村 治, 亀田 恭男

    日本物理学会講演概要集. 秋の分科会   1995 ( 3 )   288 - 288   1995年9月

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  • 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(Tl1/2Pb1/2)-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

  • 3p-YC-1 液体(Tl_<1/2>Pb_<1/2>)-Se系の金属-非金属転移

    臼杵 毅, 植村 治, 伊藤 恵司, 亀田 恭男

    日本物理学会講演概要集. 秋の分科会   1994 ( 3 )   196 - 196   1994年8月

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▼全件表示

共同研究・競争的資金等の研究

  • 中性子およびX線回折による水素吸蔵結晶合金の局所構造観察の研究

    研究課題/領域番号:18760494  2006年 - 2007年

    日本学術振興会  科学研究費助成事業  若手研究(B)

    伊藤 恵司

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    配分額:3400000円 ( 直接経費:3400000円 )

    【研究内容】本研究では,従来のブラッグピークに基づく結晶構造解析法ではなく、液体やアモルファスなどの非晶質材料の構造解析手法である"二体分布関数解析法"をバナジウム水素化物(β-V2H)の構造解析に適用し、V格子構造の詳細解明を試みた。すなわち、放射光X線回折実験により得られたβ-V2H粉末試料の回折データについて、バックグラウンドや試料吸収などの補正を行い、1原子あたりの散乱強度に規格化された構造因子を得た。さらに、構造因子をフーリエ変換することにより二体分布関数を得た。バナジウム水素化物(β-V2H)の二体分布関数から,V-V原子間距離を直接観察することで,水素吸蔵によるバナジウム格子構造の変化についての重要な情報を得ることに成功した。すなわち、バナジウム原子が理想的な格子位置から0.01nm変位して、水素原子と安定な距離を維持していることが明らかになった。
    【研究の意義および重要性】水素吸蔵合金の高容量化が求められている中、バナジウム系合金は水素吸蔵合金の中で最も高い理論水素吸蔵容量をもつことで注目されている。バナジウム系合金の更なる高容量化や水素吸放出特性の改善のためには、バナジウム水素化物についての基礎的研究で得られる情報が不可欠である。特に,水素化にともなうホストバナジウム格子構造の詳細解明、すなわち、理想的な格子位置からのV原子の"変位"の定量は,V-H間の相互作用を直接反映し,この値を正確に見積もることはバナジウム水素化物の安定性を考える上でとりわけ重要である。

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  • 中性子散乱による融体・金属ガラスの構造ゆらぎとダイナミックス

    研究課題/領域番号:15074208  2003年 - 2007年

    日本学術振興会  科学研究費助成事業  特定領域研究

    福永 俊晴, 伊藤 恵司, 大友 季哉

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    配分額:45300000円 ( 直接経費:45300000円 )

    金属ガラスの安定性は金属ガラスを構成する短範囲構造ユニットや中距離構造と深い関係があると考える。さらに、非平衡状態では安定になるための原子の動きがあることから、原子の運動とも深く関わっていると考えられる。熱的に安定なCu-Zr金属ガラスは20面体的な構造ユニットが多く存在するが、Ni-Zr金属ガラスはNi-Zr系の安定結晶を構成している三角プリズム構造が多く存在することが明らかになった。そのNi-Zr系金属ガラスにA1などの第三元素を添加することにより熱的安定性が増すが、そのときの構造変化を調べた結果、A1添加により三角プリズム構造が減少し、20面体的な構造ユニットの増加が観察された。このことは金属ガラスの熱的安定性は構造学的に20面体的な構造ユニットが強く関わっていることを示唆している。Cu-Zr系金属ガラスに第三元素としてA1を添加したときの構造変化を調べると、20面体的な構造ユニットの構造の急激な増加は見られないが、正20面体的なユニットの増加が観察された。この変化を、中性子非弾性散乱を用いたダイナミックス観点から検討を行った結果、5meV付近に観察される低エネルギー励起(ボゾンピーク)の強度がA1を添加することによって低下することが明らかになった。この現象は金属ガラスにおける自由体積(free volume)の減少と解釈することが出来ることから、第三元素の添加による金属ガラスの熱的安定性は系の自由体積の減少による原子の動きの低下によるものと解釈することができる。すなわち、金属ガラスの熱的安定性をよくするためには、系の構成構造ユニットである正20面体を増加させ、かつ自由体積を減少させることであることが明らかになった。

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  • 中性子回折によるナノ水素吸蔵合金の構造の解明

    研究課題/領域番号:15710087  2003年 - 2004年

    日本学術振興会  科学研究費助成事業  若手研究(B)

    伊藤 恵司

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    配分額:3600000円 ( 直接経費:3600000円 )

    近年、ナノ構造化による特異な水素吸蔵特性が見出されている。本研究では、バナジウム-水素系とグラファイト-水素系の2つの系について、水素原子の存在位置及びその周囲の環境をパルス中性子および高エネルギーX線回折実験により明らかにすることを目的とした。ナノβ-VD_<0.5>とナノグラファイト-水素は、重水素ガス雰囲気下におけるメカニカルミリングにより作製された。これらのサンプルは微粉末のため酸化しやすく吸湿性が高い。したがって、不活性ガス置換したグローブボックス内でサンプルの取り扱いをおこなった。X線回折実験ではカプトンウインドウの密閉セルを用い、中性子回折実験ではTiZr合金の密閉セルを用いた。
    ナノβ-VD_<0.5>については、高エネルギーX線回折実験の結果から、V金属格子がこれまで報告されているBCT構造とは異なることが明らかになった。さらに、パルス中性子回折実験とリバースモンテカルロ計算から、水素原子は8面体の中心から4方向にずれた位置で存在確率が高いことが明らかになった。
    一方、ナノグラファイト水素系については、中性子回折実験により得られた動径分布関数において,通常のグラファイトにおけるC-C結合のほかに、C-C単結合に相当する相関ピークが観測された。更に、中性子非弾性散乱スペクトルにおいてsp^3炭素のC-H変角振動に対応するピークが観測されたことから、sp^2混成炭素の他にsp^3混成炭素が存在していることが明らかになった。

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  • 中性子回折によるTi-Zr系水素吸蔵合金の水素原子位置の解明

    研究課題/領域番号:13750611  2001年 - 2002年

    日本学術振興会  科学研究費助成事業  若手研究(B)

    伊藤 恵司

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    配分額:2300000円 ( 直接経費:2300000円 )

    本研究では、中性子零散乱合金であるTi_<0.6756>Zr_<0.3244>組成粉末を重水素雰囲気中でミリングすることにより、アモルファス及び結晶(Ti_<0.6756>Zr_<0.3244>)D_xを作製し、それらの原子構造ならびに水素原子の存在位置を中性子回折実験により調べた。
    Ti(99.99%,#100)及びZr(98%,#100)を高純度Ar(5N)で数回置換し、1.3×10^<-2>Pa以下まで真空引きした後、遊星型ボールミル(フリッチュP-5)により0.08MPa及び2MPaの重水素雰囲気中で720ksミリングし、アモルファス(Ti_<0.6756>Zr_<0.3244>)D_<0.31>及び結晶(Ti_<0.6756>Zr_<0.3244>)D_<1.54>をそれぞれ作製した。中性子回折実験は高エネルギー加速器研究機構・物質構造科学研究所に設置されているHIT-II回折装置を用いて行われた。
    Zr原子の中性子に対する干渉性核散乱振幅は正の値であるのに対し、Ti原子のそれは負の値であるので、中性子回折で得られたRDF(r)のTi-Zr相関は負のピークとして観測される。アモルファスTi_<0.6756>Zr_<0.3244>D_<0.31>のRDF(r)にはTi-Zr相関に相当する負のピークが観測された。これはミリングによりTiとZrが原子レベルで混合していることを示している。また、S(Q)のピーク位置から、アモルファス相ではTi-Zr系の高温相であるBCC構造が残っていることがわかった。一方、結晶Ti_<0.6756>Zr_<0.3244>D_<1.54>のRDF(r)には、Ti-Zr相関に相当する負のピークは観測されなかった。また、S(Q)のピーク位置がTi及びZrの水素化物のそれと一致することから、ミリングによりTiとZrの原子レベルの混合がおこなわれず、それぞれの水素化物が形成されたものと考えられる。
    更に、アモルファス(Ti_<0.6756>Zr_<0.3244>)D_<0.31>における水素原子の存在サイトに関する詳細な情報を得るため、中性子回折実験により得られたデータについてリバースモンテカルロ計算を行った。その結果、98%の水素原子が4面体サイトに存在していることが明らかになった。

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  • 超軽量水素吸蔵材料の開発

    研究課題/領域番号:12875118  2000年 - 2001年

    日本学術振興会  科学研究費助成事業  萌芽的研究

    福永 俊晴, 伊藤 恵司

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    配分額:2200000円 ( 直接経費:2200000円 )

    (A)軽量水素吸蔵材料としてグラファイトのポーラス化を試みている。
    1.ナノポーラスカーボン(カーボンエアロゲル)の水素化
    アルコールの超臨界状態を用いてゲル状のカーボンを作製し、さらにそのゲル状カーボンを乾燥させてナノポーラスカーボンを作製し、それを圧力セル中に入れベーキングした後水素を6Mpaまで導入し水素化を試みた。現在、種々の実験を試みている。
    2.カーボンマイクロコイル
    微量の硫黄を含むアセチレンをNiなどの触媒中で750-800℃で0,5-2時間熱分解させることにより得られる。As-grownのカーボンコイルはほとんどがアモルファスであるが、2500-3000℃で熱処理をするとコイル状を保持したままグラファイト化する。
    この状態の構造変化を中性子回折で観察し、どの状態が水素を吸蔵しやすいかを確認している。
    このような多種多様な方法でナノポーラスカーボンやポーラスカーボン、そしてカーボンマイクロコイル、さらにカーボンナノファィバーなどを作製し、水素吸蔵特性をチェックしながら、そのカーボン材料の構造を高分解能中性子回折によって観察し、水素の存在位置を明らかにしようとしている。
    (B)TiやMg金属を含む水素吸蔵材料
    グラファイトにTiやMg金属を混入させ、軽量でかっ、水素を多量に吸蔵させることができる材料の探索と、中性子回折による構造観察、ならびに水素原子の存在位置の観察を行っている。水素原子はグラファイトのダングリングボンドと選択的に結合していることが明らかとなった。
    (C)Ti-Zr系に水素を吸蔵させて、水素原子の存在位置を中性子回折で明らかにしている。水素原子を吸蔵するとアモルファス化することから、水素原子の存在は単にTiやZrの水素化物を形成するだけではないことが明らかとなった。

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  • ナノ構造グラファイトエネルギー材料の開発と構造学的研究

    研究課題/領域番号:12450259  2000年 - 2001年

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    福永 俊晴, 伊藤 恵司, 川口 昭夫

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    配分額:15100000円 ( 直接経費:15100000円 )

    グラファイトのミリングによってグラファイトがナノ化し、さらにそれが活性化することを明らかにしてきている。その研究成果が発端となり本研究が開始された。すなわち、グラファイトを水素雰囲気中でミリングすると、活性化したグラファイトと水素原子がある種の反応をおこし、ミリング初期から水素の吸収が始まることが明らかとなった。また、その時グラファイトの層間が広がっていくことから一部の水素は層間に入っていくことも明らかになった。これらの結論は中性子回折実験から明らかとされた。
    ミリングによってグラファイトがナノ化した状態で、水素吸収による層間距離の広がりを示す構造因子S(Q)の第1ピークの位置の変化が中性子回折実験により観察された。さらに、動径分布関数RDF(r)からC-D相関の位置が明確となった。すなわち、グラファイトの水素雰囲気でのミリングによって非架橋炭素原子が形成され、一部の水素原子はこの炭素原子と結合するが、残りの水素原子はグラファイト層間に入っていくことが分かった。さらに非弾性散乱実験結果からもこの実験事実がサポートされた。
    このグラファイト水素吸蔵材料の水素放出をTDS測定によって明らかにすることができた.ほぼ800Kと1000Kに水素放出ピークが観察され、低温のピークはグラファイト層間に存在する水素の放出、そして高温のピークは炭素原子と結合している水素の放出であろうと推測される。これらのTDSは水素ならびに重水素でも同じ結果が得られている。
    これらの結果から、ナノグラファイトは水素吸蔵材料として十分に使えることが証明されたと考えることが出来る。今後は触媒をグラファイトに混入させることにより、水素の吸収・放出が容易になると考えられる。

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  • 中性子散乱によるプロチウム吸蔵合金の構造研究

    研究課題/領域番号:12022216  2000年

    日本学術振興会  科学研究費助成事業  特定領域研究(A)

    福永 俊晴, 伊藤 恵司

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    配分額:2100000円 ( 直接経費:2100000円 )

    メカニカルアロイング(MA)法を用いてTi-Zr系ならびにTb-Fe系の結晶並びにアモルファス材料の水素吸蔵合金を作製した。
    1.Ti-Zr系水素吸蔵合金
    TiとZrの状態図は全率固溶体であり、このような系ではTiとZr原子の組成分布はランダムに配列する。それ故にTiとZrの中性子に対する干渉性散乱振幅が負と正であることを利用すれば、Ti-32.4at%Zr組成で中性子零散乱合金となる。中性子零散乱合金での中性子回折から得られた強度からBhatia-Thomtonの定義に基づいて得られた構造因子ならびに分布関数は濃度-濃度相関を表している。この場合、系全体が完全固溶体であるので、得られた濃度-濃度相関分布関数はTi-Zr相関を示す小さな負のピークを示す以外非常に揺らぎの少ないものであることが明らかにされた。さらに、Ti-32.4at%Zr中性子零散乱合金組成の粉末を水素雰囲気(中性子散乱のために重水素を使用)中でメカニカルアロイングを行い(Ti-32.4at%Zr)D_<0.12>アモルファス合金を作製した。Ti-32.4at%Zr中性子零散乱合金は水素を吸蔵することにより、その組成揺らぎが助長されることが明らかとなった。特に水素原子との親和力の違いによりD原子の周りのTiとZr原子の位置が変化していくものと考えられる。
    2.Tb-Fe系の水素吸蔵合金
    この系ではTbならびにFe粉末を1:2の割合で混合し、重水素雰囲気中でメカニカルアロイングを行った。この系では結晶性水素吸蔵合金とアモルファス水素吸蔵合金がそのミリング条件の違いにより結晶性が保持されたり、アモルファス化が促進されたりすることが明らかになった。それぞれ、水素原子の存在位置が異なっていることも明らかとなった。アモルファス化においては水素原子と親和力の大きいTb原子で構成する4面体に水素が入ることにより、結晶構造がゆがみ、アモルファス化が促進されることが明らかとなった。

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  • 水素吸蔵合金の中性子回析

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    資金種別:競争的資金

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  • 非晶質系の中性子回析

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    資金種別:競争的資金

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  • Neutron Diffraction of Hydrogen Absorbing Alloys

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    資金種別:競争的資金

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  • Neutron Diffraction of Non-Crystalline System.

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    資金種別:競争的資金

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  • PBL特論Ⅵ (2020年度) 第2学期  - その他

  • PBL特論Ⅶ (2020年度) 第3学期  - その他

  • PBL特論Ⅷ (2020年度) 第4学期  - その他

▼全件表示