研究者詳細 - 伊藤　恵司

論文 - 伊藤　恵司

分割表示 89 件中 1 - 20 件目／全件表示 >>

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

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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

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

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

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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

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

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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

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

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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

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

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

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

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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