研究者詳細 - 伊藤　恵司

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

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

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

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

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

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