研究者詳細 - 伊藤　恵司

論文 - 伊藤　恵司

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Pulsed neutron diffraction study of NaNO2 and KNO2 pure melts 査読

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

Electrochemistry 77 ( 8 ) 741 - 744 2009年

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

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