研究者詳細 - 伊藤　恵司

論文 - 伊藤　恵司

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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

Network structure and cation environment in Ag2S-GeS2 glasses 査読

Keiji Itoh

Next Research 1 ( 2 ) 100049 - 100049 2024年12月

Deuterium occupation of interatomic hole sites in Ni67Zr33 amorphous alloy 査読

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Neutron Diffraction Study of Isotope Enriched Glassy Sm4Ti9O24 査読

JPS Conference Proceedings 8 031007 2015年

Pulsed Neutron Diffraction Study of Molten CsCl-NaCl-YCl₃: Approaches from Fundamentals to Pyrochemical Reprocessing 査読

Y. Iwadate, T. Ohkubo, T. Michii, H. Matsuura, A. Kajinami, K. Takase, N. Ohtori, N. Umesaki, R. Fujita, K. Mizuguchi, H. Kofuji, M. Myochin, M. Misawa, K. Itoh, T. Fukunaga

Molten Salts Chemistry and Technology 449 - 458 2014年5月

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

K. Mori, K. Iwase, M. Yonemura, J. Siewenie, T. Proffen, Y. Onodera, K. Itoh, M. Sugiyama, T. Kamiyama, T. Fukunaga

Journal of the Physical Society of Japan 79 ( SUPPL. A ) 84 - 86 2010年

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

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

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

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

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

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

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

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

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

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

Structure-property relationships of fast copper ion conductor cubic CuI 査読

D. S. Adipranoto, F. Shikanai, M. Yonemura, K. Mori, J. G. Park, K. Itoh, T. Kamiyama

SOLID STATE IONICS 180 ( 6-8 ) 492 - 496 2009年5月

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

Structure-property relationships of fast copper ion conductor cubic gamma-CuI (300 K) and alpha-CuI (773 K) has been investigated using the time-of-flight (TOF) neutro powder diffraction over the Q-range up to 30 angstrom(-1). Crystal structure of the both gamma- and alpha-phases were refined using the conventional Rietveld methods combined with the maximum-entropy-method (MEM), whilst the local structures were analyzed by means of the pair distribution function (PDF) combined with the reverse Monte Carlo (RMC) simulation. The crystal structure analysis revealed temperature dependence of large thermal displacement of copper ions along < 111 > directions, with average copper ions density mostly distributed at the 8c center of tetrahedrally-coordinated by 1 ions. The PDF analysis estimated the new peak position of Cu-Cu pairs shifted from 4.27 A in the gamma-phase to 2.49 A in the alpha-phase and estimation of coordination number decreases from 12.1 to 5.8, respectively. The local structure analysis found the new split peaks of g(Cu-Cu)(r) at r about 2.47 angstrom and 2.72 angstrom in the alpha-phase that roughly correspond to the Cu-Cu diagonally distance between nearest neighboring tetrahedral corner 32f-32f sites and between tetrahedral center 8c-32f sites such as represented by the splitting Cu site model of Fm-3m. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2008.09.025

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

その他リンク： http://orcid.org/0000-0002-7210-8374

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

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

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

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

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

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

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

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

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

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

その他リンク： http://orcid.org/0000-0002-7210-8374

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

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

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

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

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

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

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

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

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

その他リンク： http://orcid.org/0000-0002-7210-8374

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

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'> 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

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

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

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

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

その他リンク： http://orcid.org/0000-0002-7210-8374

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

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

その他リンク： https://jlc.jst.go.jp/DN/JALC/00276397279?from=CiNii

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

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

その他リンク： https://jlc.jst.go.jp/DN/JALC/00273248192?from=CiNii

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

掲載種別：研究論文（学術雑誌）

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

DOI： 10.2497/jjspm.53.100

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

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.

Fe-doping effects on lanthanum gallate: La_0.8Sr _0.2Ga_1-xFe_xO₃ 査読

Mori, K., Richardson Jr., J., Maxey, E., Onodera, Y., Kiyanagi, R., Itoh, K., Sugiyama, M., Fukunaga, T.

KURRI Progress Report 212 - 212 2006年

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

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.

DOI： 10.1063/1.2204511

その他リンク： http://orcid.org/0000-0002-7210-8374

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

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.

DOI： 10.1149/1.2184908

その他リンク： http://orcid.org/0000-0002-7210-8374

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

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.

DOI： 10.1016/j.jallcom.2005.01.122

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

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

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

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.

DOI： 10.1016/j.jpcs.2004.06.056

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

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

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

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

Structural studies of hydrated tricalcium silicate by neutron powder diffraction

K. Mori, K. Yatsuyanagi, K. Oishi, T. Fukunaga, T. Kamiyama, T. Ishigaki, A. Hoshikawa, S. Harjo, K. Iwase, K. Itoh, M. Kawai

Journal of Neutron Research 13 ( 1-3 ) 163 - 167 2005年

記述言語：英語掲載種別：研究論文（学術雑誌）

Structure refinements have been carried out on the pure tricalcium silicate (C S) and the hydrated C S with the D O-C S mass ratio, which is 0.5, using neutron powder diffraction (NPD). The multi-phase Rietveld analysis of the hydrated C S revealed the coexistence with the Ca(OD) (trigonal phase) and the unhydrated C S (triclinic one). The Ca(OD) phase was hardly observed on the NPD patterns in the first ∼6 h of hydration, while the several Bragg reflections of Ca(OD) appeared drastically from ∼6 to ∼24 h, and then the hydration reaction rate was gradually suppressed. We could apply the Avrami-model to the initial hydration reaction process of C S. © 2005 Taylor & Francis Ltd. 3 3 2 3 3 2 3 2 2 3

DOI： 10.1080/10238160412331299519

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

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.

DOI： 10.4028/www.scientific.net/JMNM.24-25.217

その他リンク： http://orcid.org/0000-0002-7210-8374

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

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

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.

DOI： 10.1149/1.1926667

その他リンク： http://orcid.org/0000-0002-7210-8374

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

掲載種別：研究論文（学術雑誌）

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

DOI： 10.1016/j.physb.2004.07.004

The structure of binary zinc phosphate glasses 査読

K Suzuya, K Itoh, A Kajinami, CK Loong

JOURNAL OF NON-CRYSTALLINE SOLIDS 345 80 - 87 2004年10月

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

The structures of (ZnO)(x)(P2O5)(100-x) glasses, with x = 49.1-69.7, have been studied by spallation neutron diffraction and high-energy X-ray diffraction methods. For all glasses the average Zn-O coordination number NZn-O is around five (4.5-4.9) as distorted (4 + 1) environment. Although no abrupt change in NZn-O between the nearly meta- and orthophosphate compositions is observed, the mean value and distribution of Zn-O distances slightly increases with an increase in the ZnO content. The distorted five-coordinations of Zn-O may be regarded as the mixture of ZnO4 tetrahedra and ZnO5 polyhedra. The Zn cation plays a typical role as a network-modifier in the process of the depolymerization PO4 tetrahedral network on the one hand, and may act as a network-former for linking the ZnO4 and PO4 tetrahedra on the other hand. The presence of the two kinds of intermediate-range ordering corresponding to PO4 PO4 linkage and ZnO4-PO4 connections is revealed by application of the reverse Monte Carlo modeling of the neutron and X-ray diffraction data. The enhancement of density fluctuation about the size of a few nanometers in small-angle neutron scattering region (Q similar to 0.2 Angstrom(-1)) arisen at near 60 mol% ZnO suggests that there are diverse stages in the intermediate-range structure composed of PO4 and ZnO4 tetrahedra and ZnO5 polyhedra depending on the compositions. These results demonstrated that the phosphate glass anomaly and the peculiar property for zinc phosphate glasses such as a behavior of glass transition temperature T, should be understood in terms of not only the depolymerization of network composed Of PO4 tetrahedra but also the stability of the chemical ordering Of PO4 tetrahedra and ZnO, polyhedra. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnoncrysol.2004.07.047

Crystal Structure of Fe-doped LaGaO3-δ 査読

K. Mori, K. Shibata, H. Sagehashi, T. Ishigaki, A. Hoshikawa, S. Harjo, T. Kamiyama, K. Itoh, T. Fukunaga

Physica B 350 ( 1-3 ) E1031 - E1034 2004年7月

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

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

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

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

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.

DOI： 10.1016/S0921-4526(02)02571-1

その他リンク： http://orcid.org/0000-0002-7210-8374

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

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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