研究者詳細 - 伊藤　恵司

論文 - 伊藤　恵司

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Reverse Monte Carlo modeling of atomic configuration for amorphous materials 査読

Toshiharu Fukunaga, Keiji Itoh, Kazuhiro Mori, Masaaki Sugiyama

Solid State Phenomena 127 51 - 56 2007年

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

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