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TANAKA Katsushi
Graduate School of Engineering / Department of Mechanical Engineering
Professor

Researcher basic information

■ Research Keyword
  • Physical properties of Materials
■ Research Areas
  • Nanotechnology/Materials / Structural and functional materials
  • Nanotechnology/Materials / Metallic materials

Research activity information

■ Award
  • Sep. 2010 International Metallographic Society, 2010 International Metallographic Contest Third Place
    田中 克志

  • Mar. 2010 日本金属学会, 金属写真優秀賞
    田中 克志

  • Mar. 2009 日本金属学会, 功績賞
    田中 克志

  • May 2006 日本顕微鏡学会, 日本顕微鏡学会和文誌賞
    田中 克志

  • Dec. 1999 日本MRS, 奨励賞
    田中 克志

  • Nov. 1996 伸銅技術研究会, 技術論文賞
    田中 克志

■ Paper
  • Kiichi Nakano, Daijiro Takeuchi, Takeshi Teramoto, Katsushi Tanaka
    Japan Institute of Metals, Sep. 2024, MATERIALS TRANSACTIONS, 65(9) (9), 1001 - 1007, English
    [Refereed]
    Scientific journal

  • Takeshi Teramoto, Kentaro Kitasumi, Ryota Shimohara, Yusuke Ito, Ryouga Shimizu, Katsushi Tanaka, Rintaro Ueji
    Elsevier BV, Apr. 2023, Journal of Alloys and Compounds, 941, 169016 - 169016, English
    [Refereed]
    Scientific journal

  • Takeshi Teramoto, Daisuke Noguchi, Mohamad Qayyum, Katsushi Tanaka
    Last, Elsevier {BV}, May 2022, Materialia, 22, 101420 - 101420, English
    [Refereed]
    Scientific journal

  • Takeshi Teramoto, Momoko Narasaki, Katsushi Tanaka
    To elucidate the complex mechanism of solid-solution strengthening in high-entropy alloys (HEAs), it is necessary to determine the effective atomic radii of the constituent elements that are the sources of lattice strain. In the present study, the effective atomic radii of the constituent elements in CrMnFeCoNi HEA that are the basis of the atomic displacements, are evaluated from lattice parameters experimentally determined via theta-2 theta X-ray diffraction measurements. The order of the evaluated atomic radii in the present study is different from that of the atomic radii determined via ab-initio calculations in previous studies. The results of the ab-initio calculations indicate a correlation between the yield stress of and the average atomic displacement in the HEA. However, no definite correlation is confirmed by the experimental results in the present study.
    Last, TAYLOR & FRANCIS LTD, Jan. 2022, PHILOSOPHICAL MAGAZINE LETTERS, 102(3) (3), 100 - 110, English
    [Refereed]
    Scientific journal
    Link to Kobe Univ. Repository (Kernel)

  • Mikio Oomae, Takeshi Teramoto, Katsushi Tanaka
    Variations in the positive temperature dependence of yield stress for L12 intermetallic compounds in pseudobinary alloys with the composition of Co3(Al, W)-Co3Ti have been investigated. Polycrystalline L12 compounds in the pseudo-binary system with a Co3(Al, W) to Co3Ti composition ratio of approximately 1:3 and 1:9 were prepared. The temperature dependence of the yield stress ranging from 293 to 1273 K was determined. The onset temperature for the positive temperature dependence of yield stress for each compound is located between that of Co3(Al, W) and Co3Ti. The activation energies for the positive temperature dependence of these compounds are evaluated to be 47.0 and 43.6 kJmol-1, respectively. The activation energies are also intermediate values between those of Co3(Al, W) and Co3Ti. The composition dependence of the positive temperature dependence of yield stress is estimated from the physical properties of Co3(Al, W) and Co3Ti. Although the activation energies estimated for the present compounds are slightly different from the experimentally determined values, the temperature dependences of the experimentally determined yield stress are almost represented from the estimated parameters. The composition dependence of the positive temperature dependence of the yield stress can be predicted from the physical properties of the base compounds.
    Last, Elsevier {BV}, Sep. 2021, Intermetallics, 136, 107250 - 107250, English
    [Refereed]
    Scientific journal

  • Dengshan Zhou, Zhenghao Chen, Kazuki Ehara, Kodai Nitsu, Katsushi Tanaka, Haruyuki Inui
    Elsevier {BV}, Jan. 2021, Scripta Materialia, 191, 173 - 178
    [Refereed]
    Scientific journal

  • T. Teramoto, K. Nagahira, K. Tanaka
    Elsevier {BV}, Dec. 2020, Acta Materialia, 201, 94 - 101, English
    [Refereed]
    Scientific journal
    Link to Kobe Univ. Repository (Kernel)

  • M. Fèvre, J.-M. Sanchez, J. R. Stewart, J.-S. Mérot, F. Fossard, Y. Le Bouar, K. Tanaka, H. Numakura, G. Schmerber, V. Pierron-Bohnes
    Oct. 2020, Physical Review B
    [Refereed]
    Scientific journal

  • TERAMOTO Takeshi, TAKAI Yu, HASHIGUCHI Hiroki, OKUNISHI Eiji, TANAKA Katsushi
    The alloying effect of ZrO2 on the microstructure of the thermoelectric material, TinO2n-1, which is a partially reduced rutile phase called the Magneli phase, is investigated. The microstructure of TinO2n-1 is characterized by periodically induced planar defects, called shear planes, in the rutile matrix. The configuration of the O atoms around a Ti atom in a shear plane is different from that in the rutile matrix but similar to that in Ti2O3. It is speculated that the alloying of ZrO2, which has an equivalent structure to that of rutile, causes preferential Zr addition in the rutile matrix. From the microstructural observation of the alloying specimen (Ti10O19+6 mol%ZrO2), it is revealed that the added Zr is distributed homogeneously in the entire microstructure because the valence of the Ti atoms in the matrix rutile and shear plane is similar.
    JAPAN INST METALS & MATERIALS, Oct. 2019, Materials Transactions, 60(10) (10), 2199 - 2203, English
    [Refereed]
    Scientific journal
    Link to Kobe Univ. Repository (Kernel)

  • TERAMOTO TAKESHI, YAMADA KAZUKI, ITO RYO, TANAKA KATSUSHI
    The temperature dependences of monocrystalline elastic constants of Cr-Mn-Fe-Co-Ni high entropy alloy with the face-centered cubic (fcc) structure have been experimentally determined using resonance ultrasound spectroscopy from liquid helium temperature to 1173 K. The values of three independent monocrystalline and estimated polycrystalline elastic constants are fitted using the Varshni equation so that one can obtain the values at any temperatures. The elastic anisotropy of the alloy is characterized by a relatively large value of anisotropy factor of shear modulus, which is closely related to a small value of stacking fault energy of this alloy. The monocrystalline elastic constants also indicate that a relatively strong directional interatomic bonding exists in the present high-entropy alloy. (C) 2018 Elsevier B.V. All rights reserved.
    ELSEVIER SCIENCE SA, Feb. 2019, Journal of Alloys and Compounds, 777, 1313 - 1318, English
    [Refereed]
    Scientific journal

  • Co3(Al,W)-Co3Ti擬二元L12型化合物における強度の逆温度依存性
    OOMAE MIKIO, TERAMOTO TAKESHI, TANAKA KATSUSHI
    日本学術振興会, Jul. 2018, 耐熱金属材料123委員会研究報告, 59(2) (2), 297 - 303, Japanese
    Scientific journal

  • Kabir Arora, Kyosuke Kishida, Katsushi Tanaka, Haruyuki Inui
    The deformation behaviors of rectangular-parallelepiped micropillars fabricated from [0011-oriented Nibased superalloys with negative and positive lattice misfits, respectively, were investigated with respect to the specimen size. The yield stresses of the larger specimens (side length L > -2 mu m) of both considered alloy types were found to be nearly independent of the size, while the smaller specimens (L <-2 mu m) exhibited "smaller is stronger" and "smaller is (slightly) weaker" trends for negative and positive lattice misfits, respectively. The internal stresses calculated based on the micro-elasticity theory revealed that the internal shear stress fields of the micropillars varied with their sizes. The size dependence of the calculated internal shear stress distribution agreed fairly well with the experimentally determined size dependence of the yield stress, indicating that the distribution of the internal misfit stress significantly contributed to the size-dependent yield stress of the smaller micropillars. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
    PERGAMON-ELSEVIER SCIENCE LTD, Oct. 2017, ACTA MATERIALIA, 138, 119 - 130, English
    [Refereed]
    Scientific journal

  • Tanaka, Katsushi, Teramoto, Takeshi, Ito, Ryo
    Mono-crystalline elastic constants of equiatomic quinary Cr-Mn-Fe-Co-Ni high entropy alloy with the fcc structure have experimentally been determined by a resonance ultrasound spectroscopy at room temperature. The values of the bulk modulus of the high entropy alloy experimentally determined are similar to other conventional fcc metals when the values are normalized by the melting points. This indicates that the entropy change at melting is similar to that of conventional metals. The values of Pough's index and the Cauchy pressure are determined as 1.79 and-11.6 GPa, respectively. When the ductility of the alloy is judged from the indices, the ductility of the high entropy alloy is limited. In order to explain the negative Cauchy pressure of the high entropy alloy, it is required to assume that relatively strong directional interatomic bondings like intermetallic compounds exist in the alloy though the crystal is disordered solid solution.
    Materials Research Society, 2017, Mrs Advances, 2(27) (27), 1429 - 1434, English
    [Refereed]
    Scientific journal

  • Norihiko L. Okamoto, Koretaka Yuge, Katsushi Tanaka, Haruyuki Inui, Easo P. George
    Although metals strengthened by alloying have been used for millennia, models to quantify solid solution strengthening (SSS) were first proposed scarcely seventy years ago. Early models could predict the strengths of only simple alloys such as dilute binaries and not those of compositionally complex alloys because of the difficulty of calculating dislocation-solute interaction energies. Recently, models and theories of SSS have been proposed to tackle complex high-entropy alloys (HEAs). Here we show that the strength at 0 K of a prototypical HEA, CrMnFeCoNi, can be scaled and predicted using the root-mean-square atomic displacement, which can be deduced from X-ray diffraction and first-principles calculations as the isotropic atomic displacement parameter, that is, the average displacements of the constituent atoms from regular lattice positions. We show that our approach can be applied successfully to rationalize SSS in FeCoNi, MnFeCoNi, MnCoNi, MnFeNi, CrCoNi, CrFeCoNi, and CrMnCoNi, which are all medium-entropy subsets of the CrMnFeCoNi HEA. (C) 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
    AMER INST PHYSICS, Dec. 2016, AIP ADVANCES, 6(12) (12), 125008, English
    [Refereed]
    Scientific journal

  • Co基二相超合金における格子定数ミスフィットの予測式の構築
    TANAKA KATSUSHI, IWANAKA TAKUMU, TANAKA KEN
    日本学術振興会, Nov. 2016, 耐熱金属材料123委員会研究報告, 57(3) (3), 250 - 255, Japanese
    Scientific journal

  • Norihiko L. Okamoto, Shu Fujimoto, Yuki Kambara, Marino Kawamura, Zhenghao M. T. Chen, Hirotaka Matsunoshita, Katsushi Tanaka, Haruyuki Inui, Easo P. George
    High-entropy alloys (HEAs) comprise a novel class of scientifically and technologically interesting materials. Among these, equatomic CrMnFeCoNi with the face-centered cubic (FCC) structure is noteworthy because its ductility and strength increase with decreasing temperature while maintaining outstanding fracture toughness at cryogenic temperatures. Here we report for the first time by single-crystal micropillar compression that its bulk room temperature critical resolved shear stress (CRSS) is similar to 33-43 MPa, similar to 10 times higher than that of pure nickel. CRSS depends on pillar size with an inverse power-law scaling exponent of -0.63 independent of orientation. Planar (1/2) < 110 > {111} dislocations dissociate into Shockley partials whose separations range from similar to 3.5-4.5 nm near the screw orientation to similar to 5-8 nm near the edge, yielding a stacking fault energy of 30 +/- 5 mJ/m(2). Dislocations are smoothly curved without any preferred line orientation indicating no significant anisotropy in mobilities of edge and screw segments. The shear-modulus-normalized CRSS of the HEA is not exceptionally high compared to those of certain concentrated binary FCC solid solutions. Its rough magnitude calculated using the Fleischer/Labusch models corresponds to that of a hypothetical binary with the elastic constants of our HEA, solute concentrations of 20-50 at.%, and atomic size misfit of similar to 4%.
    NATURE PUBLISHING GROUP, Oct. 2016, SCIENTIFIC REPORTS, 6, 35863, English
    [Refereed]
    Scientific journal

  • Katsushi Tanaka, Norihiko L. Okamoto, Satoshi Fujio, Hiroki Sakamoto, Haruyuki Inui
    A convergent-beam electron diffraction (CBED) method is proposed for polarity determination, in which polarity is determined from the intensity asymmetry of any of the hkl-(hkl) over bar Friedel pairs appearing in a zone-axis CBED pattern with a symmetric arrangement of Bijvoet pairs of reflections. The intensity asymmetry occurs as a result of multiple scattering among Bijvoet pairs of reflections in the CBED pattern. The appropriate zone-axis orientations for polarity determination are deduced for 19 of the 25 polar point groups from symmetry considerations so as to observe Bijvoet pairs of reflections symmetrically in a single CBED pattern. These appropriate zone-axis orientations deduced for the 19 polar point groups coincide with nonpolar directions. This is because the nonpolar directions for these point groups are perpendicular to an even-fold rotation axis, which guarantees the symmetric arrangement of Bijvoet pairs of reflections with respect to the symmetry (m-m') line in a CBED pattern taken along any of the appropriate zone-axis orientations. The m-m' line in the CBED pattern is proved to be perpendicular to the trace of the even-fold rotation axis. On the other hand, if the nonpolar direction is either perpendicular to a mirror plane or parallel to a roto-inversion axis as in the four point groups m, 3m1, 31m, (6) over bar, the nonpolar direction cannot be used as the appropriate zone-axis orientation for polarity determination because the Bijvoet pairs of reflections are not arranged symmetrically in the CBED pattern. The validity of the CBED method is confirmed both by experiment and by calculation of CBED patterns.
    INT UNION CRYSTALLOGRAPHY, Jun. 2015, JOURNAL OF APPLIED CRYSTALLOGRAPHY, 48, 736 - 746, English
    [Refereed]
    Scientific journal

  • Co基二相超合金のCr添加による高温耐酸化性の変化
    TANAKA KATSUSHI, ITO TAKAHIKO, IKEDA SHOGO
    Co基二相超合金の耐酸化性に対するCr添加の効果を検討するため，酸化実験を行い次の結論を得た。
    (1)900℃において実用的な耐酸化性を得るためには10at%以上のCrの添加が必要である。
    (2)Crの添加はγ/γ'間の格子定数ミスフィットを低下させる。
    (3)表面近傍ではAlの内部酸化によりγ'相が分解しCo3Wの析出相が生成するため，これを抑えるような合金設計が必要である。
    Mar. 2015, 耐熱金属材料123委員会研究報告, 56(1) (1), 81 - 86, Japanese
    Symposium

  • Takahiko Ito, Shogo Ikeda, Katsushi Tanaka
    Oxidation tests of Cr containing Co-based superalloys with compositions of Co-20at.%Ni-9at.%Al-9at.%W-x at.%Cr (x = 2, 4, 6, 8 and 10) have been carried out at 1173 and 1273 K in air. Oxidation resistance is improved upon alloying with Cr not only at 1173 K but also at 1273 K. The weight gain of the 10at.%Cr alloy oxidized at 1173 K is similar to that of the 5th generation Ni-based superalloy of TMS-173. Alloying with Cr is efficient to improve oxidation resistance, however, the shape of yγ' precipitates is rounded and the alignment of the precipitates along the < 100> direction becomes less pronounced upon alloying with Cr.
    Materials Research Society, 2015, Materials Research Society Symposium Proceedings, 1760, 222 - 227, English
    [Refereed]
    International conference proceedings

  • Norihiko L. Okamoto, Akira Yasuhara, Katsushi Tanaka, Haruyuki Inui
    © 2015 Materials Research Society. The crystal structure of the δ1P phase in the Fe-Zn system has been refined by singlecrystal synchrotron X-ray diffraction combined with ultra-high resolution scanning transmission electron microscopy. The crystal structure can be described to build up with Fe-centered Zn12 icosahedra. The deformation properties obtained by single-crystal micropillar compression tests of the δ1P phase is discussed in terms of the arrangement of the Fe-centered Zn12 icosahedra in contrast with the ζ phase in the Fe-Zn system.
    2015, Materials Research Society Symposium Proceedings, 1760, 13 - 18, English
    [Refereed]
    International conference proceedings

  • TANAKA KATSUSHI, INUI HARUYUKI
    The changes in the γ’ solvus temperature and the volume fraction of Co-Al-W based alloys with fcc / L12 two-phase microstructures upon alloying with quaternary elements have been investigated. All investigated quaternary elements, except for Fe and Re, increase the γ’ solvus temperatures of Co-Al-W based alloys with varying efficiencies depending on quaternary element. On the o
    Jun. 2014, Materials Science Forum, 783/786(Pt.2) (Pt.2), 1195 - 1200, English
    [Refereed]
    Scientific journal

  • Norihiko L. Okamoto, Katsushi Tanaka, Akira Yasuhara, Haruyuki Inui
    The structure of the delta(1p) phase in the iron-zinc system has been refined by single-crystal synchrotron X-ray diffraction combined with scanning transmission electron microscopy. The large hexagonal unit cell of the delta(1p) phase with the space group of P6(3)/mmc comprises more or less regular (normal) Zn-12 icosahedra, disordered Zn-12 icosahedra, Zn-16 icosioctahedra and dangling Zn atoms that do not constitute any polyhedra. The unit cell contains 52 Fe and 504 Zn atoms so that the compound is expressed with the chemical formula of Fe13Zn126. All Fe atoms exclusively occupy the centre of normal and disordered icosahedra. Iron-centred normal icosahedra are linked to one another by face-and vertex-sharing forming two types of basal slabs, which are bridged with each other by face-sharing with icosioctahedra, whereas disordered icosahedra with positional disorder at their vertex sites are isolated from other polyhedra. The bonding features in the delta(1p) phase are discussed in comparison with those in the Gamma and zeta phases in the iron-zinc system.
    WILEY-BLACKWELL, Apr. 2014, ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE CRYSTAL ENGINEERING AND MATERIALS, 70, 275 - 282, English
    [Refereed]
    Scientific journal

  • Norihiko L. Okamoto, Katsushi Tanaka, Akira Yasuhara, Haruyuki Inui
    The structure of the δ1p phase in the iron-zinc system has been refined by single-crystal synchrotron X-ray diffraction combined with scanning transmission electron microscopy. The large hexagonal unit cell of the δ1p phase with the space group of P63/mmc comprises more or less regular (normal) Zn12 icosahedra, disordered Zn12 icosahedra, Zn16 icosioctahedra and dangling Zn atoms that do not constitute any polyhedra. The unit cell contains 52 Fe and 504 Zn atoms so that the compound is expressed with the chemical formula of Fe13Zn126. All Fe atoms exclusively occupy the centre of normal and disordered icosahedra. Iron-centred normal icosahedra are linked to one another by face- and vertex-sharing forming two types of basal slabs, which are bridged with each other by face-sharing with icosioctahedra, whereas disordered icosahedra with positional disorder at their vertex sites are isolated from other polyhedra. The bonding features in the δ1p phase are discussed in comparison with those in the Γ and ζ phases in the iron-zinc system. © 2014.
    Apr. 2014, Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials, 70(2) (2), 275 - 282, English
    [Refereed]
    Scientific journal

  • Katsushi Tanaka, Haruyuki Inui
    Microstructural change of recently discovered Co-Al-W-based γ/γ′ two phase alloys by creep with a tensile stress of 137 MPa at 1000°C were examined. Before and after creep testing, the microstructures were investigated by scanning electron microscope (SEM). Before creep, the microstructure of the alloys is so called cuboidal structure consisting of the solid-solution based on Co with the fee structure and the L12-ordered intermetallic compound based on Co3(Al,W). The γ′ precipitates were directionally coarsened during creep forming so called parallel raft structure as expected by the sign of the lattice misfit. The γ′ phase is not only elongated along the stress direction but also elongated in one of the 〈100〉 directions perpendicular to the stress direction. As a result, the shape of the γ′ phase is not a rod but a plate. The formation of parallel raft structure in the present alloys is well explained by considering internal stresses caused by a positive lattice misfit between γ and γ′ phases.
    John Wiley and Sons Inc., 2013, 8th Pacific Rim International Congress on Advanced Materials and Processing 2013, PRICM 8, 1, 409 - 414, English
    International conference proceedings

  • Takahiro Sumitani, Katsushi Tanaka, Haruyuki Inui
    Creep tests of monocrystalline Co-Al-W-based alloys with a tensile stress of 137 MPa at 1000°C were carried out. The microstructures of the crept specimens were investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM). The γ′ phase in the specimens was not only elongated along the stress direction as expected by the sign of the lattice misfit but also elongated in one of the 〈100〉 directions perpendicular to the stress direction. As a result, the shape of the γ′ phase is not a rod but a plate. In the TEM images, it was observed that many SISFs are induced in the γ′ phase by creep. A similar microstructure is also observed in Ni-based superalloys, but the microstructure was formed under relatively lower temperatures and higher applied stresses. The observation of numerous stacking faults in the γ′ phase is a clear indication that the γ′ phase precipitated in the present alloy is weaker than that in many modern Ni-based superalloys. © 2012 Materials Research Society.
    2013, Materials Research Society Symposium Proceedings, 1516, 221 - 226, English
    [Refereed]
    International conference proceedings

  • Katsushi Tanaka, Satoshi Tsutsui, Norihiko L. Okamoto, Haruyuki Inui, Alfred Q.R. Baron
    CrB2 possess the hexagonal AlB2 structure which belongs to the spacegroup of P6/mmm. The compound exhibits para- to antiferro-magnetic transition at about 88 K. By using a macroscopic measurement technique, that is, a conventional resonant ultrasound spectroscopy (RUS) with a millimeter size mono-crystal, significant elastic anomalies have been observed just above the magnetic transition temperature. On the other hand, elastic constants determined by a microscopic measurement technique, that is, an inelastic X-ray scattering method (BL35XU of SPring-8, Japan) do not show any elastic anomalies at around the transition temperature. In order to explain the discrepancy, we have introduced a kind of so called ΔE effect resulting from a multidomain structure. If crystal lattice is slightly deformed by a spontaneous magnetostriction in the antiferromagnetic state, the symmetry of crystal lattice is lowered from hexagonal to monoclinic when the symmetry of magnetic structure is taken into account. By the lowering of the symmetry, the crystal consists of six magnetic domains in the antiferro magnetic state. If magnetic domain boundaries move in response to externally applied stresses, the mechanical deformation is absorbed by nonelastic deformations induced by the movement of magnetic domain boundaries. This multidomain model well explains the experimental results obtained by both microscopic (X-ray) and macroscopic (ultrasound) measurements. The microscopic measurement technique is useful to obtain the true elastic properties of crystal lattice without effects coming from a multidomain structure. © 2013 Materials Research Society.
    2013, Materials Research Society Symposium Proceedings, 1528, 77 - 82, English
    [Refereed][Invited]
    International conference proceedings

  • Co基超合金におけるクリープ変形と縦ラフトの形成
    TANAKA KATSUSHI, INUI HARUYUKI
    日本学術振興会, Nov. 2012, 耐熱金属材料123委員会研究報告, 53(3) (3), 249 - 254, Japanese
    Scientific journal

  • Anisotropy of Lattice Thermal Conduction in TiO2-x with High Density of Planar Defects by Atomistic Simulations
    MIYAUCHI YOHEI, TADA MASAHIRO, YOSHIYA MASATO, HARADA SHUNTA, TANAKA KATSUSHI, YASUDA HIDEYUKI, INUI HARUYUKI
    Apr. 2012, AMTC Lett., 3, 242 - 243, English
    [Refereed]
    Scientific journal

  • Shunta Harada, Katsushi Tanaka, Kyosuke Kishida, Norihiko L. Okamoto, Noriaki Endo, Eiji Okunishi, Haruyuki Inui
    The crystal structure of rhenium silicide with an anomalous ordered arrangement of vacancies has been investigated by utilizing spherical-aberration (C-s)-corrected scanning transmission electron microscopy (STEM). Using C-s-corrected STEM imaging, we directly observe for the first time ordered silicon vacancies in thermoelectric rhenium silicide accompanied by anomalously large local thermal vibration ("rattling" motion) of silicon atoms in their adjacent sites. (C) 2012 The Japan Society of Applied Physics
    JAPAN SOC APPLIED PHYSICS, Mar. 2012, APPLIED PHYSICS EXPRESS, 5(3) (3), 1 - 35203, English
    [Refereed]
    Scientific journal

  • Takayuki Nakamoto, Nobuhiko Shirakawa, Kyosuke Kishida, Katsushi Tanaka, Haruyuki Inui
    There has been a growing interest and practical importance in producing implants such as artificial joints, bone fixators and spinal fixators with titanium. In order to achieve good bone/implant fixation while avoiding the problem of bone absorption, it is mandatory to reduce the Young's modulus of titanium while keeping the high strength so as to achieve the compatibility in these mechanical properties with human cortical bone. We have tried to fabricate porous titanium with directional pores by the use of the method based on Selective Laser Melting (SLM), in which complex three-dimensional parts even containing designed shapes of pores can be produced by sintering successive thin layers of metal powder with a laser beam. Here we show that porous titanium with directional pores aligned in the longitudinal direction of the ingot is successfully produced through the use of the SLM process and that high strength and low modulus comparable to those of human bone are simultaneously achieved when these properties are measured in the longitudinal direction of the ingot.
    Fuji Technology Press, 2012, International Journal of Automation Technology, 6(5) (5), 597 - 603, English
    [Refereed]
    Scientific journal

  • Katsushi Tanaka, Masahiro Ooshima, Nobuyasu Tsuno, Akihiro Sato, Haruyuki Inui
    The creep deformation behaviour of single crystals of Co-Al-W-based alloys with gamma + gamma' two-phase microstructures has been investigated in tension under a constant stress of 137MPa in air at 1000 degrees C as a function of the gamma' solvus temperature and the volume fraction of the gamma' phase. When described by the creep strain rate versus time curve, the creep deformation of Co-Al-W-based alloys consists of transition and accelerating regions without a steady-state region, as observed in many modern nickel-based alloys. However, the creep strength of the present Co-Al-W-based alloys is comparable with nickel-based superalloys of the first generation but is much weaker than those of the second and higher generations. Unlike in nickel-based superalloys, the so-called p (parallel)-type raft structure, in which the gamma' phase is elongated along the tensile axis direction, is formed during creep in Co-Al-W-based alloys, being consistent with what is expected from the positive values of lattice misfit between the gamma and gamma' phases. As a result, of the alloys investigated, the best creep properties are obtained with the alloy possessing the highest volume fraction (85%) of the gamma' phase, which is far larger than usual for nickel-based superalloys (55-60%).
    TAYLOR & FRANCIS LTD, 2012, PHILOSOPHICAL MAGAZINE, 92(32) (32), 4011 - 4027, English
    [Refereed]
    Scientific journal

  • Md Moniruzzaman, Hiroaki Fukaya, Yoshinori Murata, Katsushi Tanaka, Haruyuki Inui
    Diffusion of Ti, V, Nb, Mo and Ta in Ni3Al phase was investigated at different temperatures using Ni-Al-X (X = Ti, V, Nb, Mo, Ta) pseudo-binary diffusion couples. The magnitude of the interdiffusion coefficients was in the descending order of V, Mo, Ti, Nb and Ta at all experimental temperatures ranging from 1423 to 1573 K. Diffusion data obtained in this study was compared with those of Re and Ru available in the literature as Re and Ru are recently being added in modern Ni-based superalloys. Diffusion retardation occurred for Ti, V, Nb, Mo and Ta as compared to Ru, and this can be explained by the anti-site diffusion mechanism. The high activation energy for anti-site formation is required for beta-site (Al-site) elements, such as Ti, V, Nb, Mo and Ta. However, as Ru can diffuse either by alpha- (Ni-site) or beta-site preferences without creating local disorder, Ru diffusion is not retarded by the anti-site diffusion mechanism.
    JAPAN INST METALS, 2012, MATERIALS TRANSACTIONS, 53(12) (12), 2111 - 2118, English
    [Refereed]
    Scientific journal

  • Yoshiya Masato, Miyauchi Yohei, Tada Masahiro, Harada Shunta, Tanaka Katsushi, Yasuda Hideyuki, Inui Haruyuki
    熱電材料としても注目される、ナノメートルオーダーの面間隔のシア構造を内包するTiO2-xの熱伝導機構の解析を摂動分子動力学法により行った。得られた熱伝導度は大きな方位依存性を示し、シア面垂直方向についてはシア面間隔の減少と共に熱伝導度減少が見られたが、面間隔が数Åの範囲では、シア面平行方向の熱伝導度の面間隔依存性は非常に小さなものでありほぼ一定であった。また直感に反して、シア面に垂直方向の熱伝導度がシア面平行方向の熱伝導度よりも低いことがわかった。これはシア面に沿った原子の配位環境の乱れに起因するものであると考えられる。
    The Ceramic Society of Japan, 2011, Preprints of Annual Meeting of The Ceramic Society of Japan
    Preprints of Fall Meeting of The Ceramic Society of Japan, 2011(0) (0), 759 - 759
    Scientific journal

  • A Micromechanical Analysis of Creep Deformation Induced Microstructural Evolutions in Nickel Base Superalloys
    Tanaka Katsushi, Hashimoto Wataro, Inui Haruyuki
    Jan. 2011, Macro to Nano-scale Inelastic Deformation and Failure of Materials & Multi-scale Modeling, 289, English
    International conference proceedings

  • Katsushi Tanaka, Masahiro Ooshima, Norihiko L. Okamoto, Kyosuke Kishida, Haruyuki Inui
    Changes in the morphology of γ′ precipitates in a γ/γ′ two-phase microstructure in Co-based superalloys, which occur through higher-order alloying, have been investigated. The shape of γ′ precipitates changes from a cuboid to an irregularly rounded shape when the Ta content increases to 4 at.%. The irregular shape of the γ′ precipitates changes to cuboid again upon further alloying with 2 at.% Mo. Changes in the morphology of γ′ precipitates are closely related to variations in the lattice misfit between γ and γ′ phases upon alloying. A lattice misfit increases with an increase in Ta content, which makes γ/γ′ interfaces incoherent when the lattice misfit exceeds a critical value. On the contrary, the lattice misfit decreases upon alloying with Mo. Changes in the lattice misfit upon alloying are well explained through the partition behavior of alloying elements and their atomic volume. © 2011 Materials Research Society.
    2011, Materials Research Society Symposium Proceedings, 1295, 423 - 428, English
    [Refereed]
    International conference proceedings

  • Yuji Ochiai, Kyosuke Kishida, Katsushi Tanaka, Haruyuki Inui
    Elastic properties, thermal expansion and deformation behavior of Cr 5Si3 with the D8m structure were investigated using single crystals. From the values of Cauchy pressures as well as the ratio of the polycrystalline bulk modulus (B) to shear moduls (G) estimated from single-crystal elastic constants (cij), deformation behavior of Cr5Si3 is expected to be relatively brittle compared to Mo5Si3 with the same crystal structure. However, plastic deformation of Cr5Si3 is confirmed above 900-1100°C depending on the loading axis orientations. © 2011 Materials Research Society.
    2011, Materials Research Society Symposium Proceedings, 1295, 213 - 218, English
    [Refereed]
    International conference proceedings

  • Shunta Harada', Katsushi Tanaka, Kyosuke Kishida, Norihiko L. Okamoto', Noriaki Endo, Eiji Okunishi, Haruyuki Inui
    The crystal structure of thermoelectric rhenium silicide with an ordered arrangement of vacancies is investigated by utilizing spherical aberration (Cs) corrected scanning transmission electron microscopy (STEM) combined with synchrotron X-ray diffraction and conventional transmission electron microscopy. By STEM Cs corrected imaging, we can clearly observe Si vacancies in rhenium silicide, which is impossible without Cs correction. In addition, significantly reduced contrast levels are noted in STEM images for particular Si sites near vacancies. From the STEM image simulation, the reduced contrast levels are concluded to be due to anomalously large local thermal vibration of these Si atoms. The crystal structure of rhenium silicide can be successfully refined by the synchrotron X-ray diffraction starting with the deduced structure model from the STEM images and the occurrence of large local thermal vibration can be qualitatively confirmed. Furthermore, we confirm the validity of the refined crystal structure of rhenium silicide by comparing experimental images with simulated image generating with the refined crystal structure parameters. © 2011 Materials Research Society.
    2011, Materials Research Society Symposium Proceedings, 1295, 397 - 402, English
    [Refereed]
    International conference proceedings

  • Kazuki Fujimura, Kyosuke Kishida, Katsushi Tanaka, Haruyuki Inui
    Square-shaped micropillar of nearly stoichiometric TiAl single crystals with various loading axis orientations were prepared from TiAl PST crystals by focused ion beam (FIB) technique and deformed in compression using a micro hardness testing machine equipped with a flat diamond tip in order to investigate the values of CRSS for the three types of operative deformation modes, namely {111}1/2〈110〉 ordinary slip, {111}〈101〉 superlattice slip and {111}〈112〉 twinning. The selective activation of the three types of deformation modes was confirmed to be achieved by compression tests of [211]-, [110]- and [112]-oriented single crystalline micropillars, respectively. The average CRSS values for ordinary slip, superlattice slip and deformation twinning obtained for micropillars with an initial side length between 3.8 and 7.9μm were estimated to be about 145, 284 and 113 MPa, respectively. © 2011 Materials Research Society.
    2011, Materials Research Society Symposium Proceedings, 1295, 201 - 206, English
    [Refereed]
    International conference proceedings

  • Inui, H., Oohashi, T., Okamoto, N. L., Kishida, K., Tanaka, K.
    The physical and mechanical properties of Co-3(Al,W) with the L1(2) structure have been investigated both in single and polycrystalline forms. The values of all the three independent single-crystal elastic constants and polycrystalline elastic constants of Co-3(Al,W) experimentally determined by resonance ultrasound spectroscopy at liquid helium temperature are 15 similar to 25% larger than those of Ni-3(Al,Ta) but are considerably smaller than those previously calculated. When judged from the values of Poisson's ratio, Cauchy pressure and G(h) (shear modulus)/B-h (bulk modulus), the ductility of Co-3(Al,W) is expected to be sufficiently high. Indeed, the value of tensile elongation obtained in air is as large as 28 %, which is far larger than that obtained in Ni3Al polycrystals under similar conditions.
    TRANS TECH PUBLICATIONS LTD, 2011, Materials Structure & Micromechanics of Fracture, 465, 9 - 14, English
    [Refereed]
    International conference proceedings

  • Inui, H., Oohashi, T., Okamoto, N. L., Kishida, K., Tanaka, K.
    The mechanical properties of Co-3(Al,W) with the Ll(2) structure have been investigated both in single and polycrystalline forms. The values of all the three independent single-crystal elastic constants and polycrystalline elastic constants of Co-3(Al,W) experimentally determined by resonance ultrasound spectroscopy at liquid helium temperature are 15 similar to 25% larger than those of Ni-3(Al,Ta) but are considerably smaller than those previously calculated. When judged from the values of Poisson's ratio, Cauchy pressure and ratio of shear modulus to bulk modulus (G(h)/B-h), the ductility of Co-3(Al,W) is expected to be sufficiently high. In the yield stress-temperature curve, a rapid decrease and an anomalous increase in yield stress is observed in the low and intermediate (1000-1100K) temperature ranges, respectively. The former is concluded to be due to the solid-solution hardening effect while the latter is attributed to thermally activated cross-slip of APB-coupled a/2 < 110 > superpartial dislocations from octahedral to cube slip planes.
    TRANS TECH PUBLICATIONS LTD, 2011, Euro Superalloys 2010, 278, 1 - 6, English
    [Refereed]
    International conference proceedings

  • Tsuno, N., Sato, A., Tanaka, K., Inui, H.
    The evolution of the raft structure in the Ni-based single-crystal superalloy TMS-138 crept at 1100 degrees C and 137 MPa has been investigated quantitatively by the Fourier analysis of scanning electron microscope (SEM) images. This method of analysis quantifies the extent of tilting of the gamma/gamma' interface during creep deformation. The analysis is carried out on two different crystallographic planes, (100) and (110), on which SEM observations of deformation microstructures are made, to see if there is any difference in the results of analysis depending on observation planes. The tilt angle of the gamma/gamma' interface, which is deduced by the Fourier analysis, increases with the accumulation of creep strain. The rate of the increase in the tilt angle is significantly large in the tertiary creep stage. The result of analysis does not depend significantly on crystallographic planes on which SEM observations of microstructures are made.
    TRANS TECH PUBLICATIONS LTD, 2011, Euro Superalloys 2010, 278, 19 - +, English
    [Refereed]
    International conference proceedings

  • Tanaka, K., Hashimoto, W., Inoue, T., Inui, H.
    The effect of elastic driving force on the microstructural change of superalloys in the secondary creep stage is evaluated by elastic energy calculations with the concept of effective eigen strain where both lattice mismatch and creep strain are taken into account The elastic energy calculations indicates that the elastic state in the secondary creep stage is totally different to that in the initial one where the lattice misfit between gamma and gamma' phases is over accommodated along the [100] and [010] directions by creep deformation in the gamma phase. The excess creep dislocations for the over accommodation are required so as to develop an internal stress field to prevent further creep deformations. The planer raft structure with the plane normal oriented to the [001] direction is unstable in the over accommodated state. The gamma/gamma' lamellar interfaces will be inclined to make a wavy raft structure of which elastic energy is lower than the ideal 001 planer raft structure.
    TRANS TECH PUBLICATIONS LTD, 2011, Euro Superalloys 2010, 278, 126 - 131, English
    [Refereed]
    International conference proceedings

  • Shunta Harada, Hiroaki Hoshikawa, Kosuke Kuwabara, Katsushi Tanaka, Eiji Okunishi, Haruyuki Inui
    The crystal structure and microstructure of ReSi1.75 were investigated by synchrotron X-ray diffraction combined with scanning transmission electron microscopy. ReSi1.75 contains an ordered arrangement of vacancies in Si sites in the underlying tetragonal C11(b) lattice of the MoSi2-type and the crystal structure is monoclinic with the space group Cm. Atomic positions of Si atoms near vacancies are considerably displaced from the corresponding positions in the parent C11(b) structure, and they exhibit anomalously large local thermal vibration accompanied by large values of atomic displacement parameter. There are four differently-oriented domains with two of them being related to each other by the 90 degrees rotation about the c-axis of the underlying C11(b) lattice and the other two being their respective twins. The habit planes for domain boundaries observed experimentally are consistent with those predicted with ferroelastic theory.
    TAYLOR & FRANCIS LTD, 2011, PHILOSOPHICAL MAGAZINE, 91(23) (23), 3108 - 3127, English
    [Refereed]
    Scientific journal

  • M. Ooshima, K. Tanaka, N.L. Okamoto, K. Kishida, H. Inui
    Oct. 2010, Journal of Alloys and Compounds, 508(1) (1), 71 - 78, English
    [Refereed]
    Scientific journal

  • Shunta Harada, Katsushi Tanaka, Haruyuki Inui
    The thermoelectric properties of Magǹli phase titanium oxides TinO2n-1 (n=2,3,) have been investigated, paying special attention to how the thermoelectric performance can be altered by changing the microstructure. Dense polycrystalline specimens with nominal composition of TiO2-x (x=0.05, 0.10, 0.15, and 0.20) prepared by conventional hot-pressing are all identified to be one of the Magǹli phases, in which crystallographic shear planes are regularly introduced according to the oxygen deficiency. Electrical conduction is n-type for all specimens and the carrier concentration increases with the increase in the oxygen deficiency. The values of lattice thermal conductivity, on the other hand, decrease with the increase in the oxygen deficiency, which can be attributed to phonon scattering at the crystallographic shear plane. The largest value of thermoelectric figure of merit Z, 1.6× 10-4 K-1 was obtained at 773 K for the hot-pressed specimen of TiO1.90. © 2010 American Institute of Physics.
    Oct. 2010, Journal of Applied Physics, 108(8) (8), 83703, English
    [Refereed]
    Scientific journal

  • 21pGR-2 半導体クラスレートのラットリング振動とそのケージサイズ依存性(21pGR クラスレート,領域7(分子性固体・有機導体))
    久米 徹二, 大野 聡, 矢嶋 一平, 佐々木 重雄, 清水 宏晏, 岡本 範彦, 田中 克志, 乾 晴行, 岸本 堅剛, 小柳 剛, 大石 泰生
    Mar. 2010, 日本物理学会講演概要集, 65(1) (1), 885, Japanese
    [Refereed]
    International conference proceedings

  • Kyosuke Kishida, Masakazu Fujiwara, Hiroki Adachi, Katsushi Tanaka, Haruyuki Inui
    The deformation behavior of Ti5Si3 single crystals with the hexagonal D88 structure has been investigated in compression as a function of crystal orientation in a temperature range from 1200 to 1500 °C. Three different types of deformation modes - {1 over(1, ̄) 0 0}[0 0 0 1] prismatic slip, {2 over(1, ̄) over(1, ̄) 2}1/3〈2 over(1, ̄) over(1, ̄) over(3, ̄)〉 pyramidal slip and {2 over(1, ̄) over(1, ̄) 8}〈8 over(4, ̄) over(4, ̄) over(3, ̄)〉 twinning - were identified for the first time as being operative in Ti5Si3 at temperatures above 1300 °C, depending on the loading axis orientation. The critical resolved shear stresses (CRSSs) decrease steeply with increasing temperature for all deformation modes. The values of the CRSSs for {1 over(1, ̄) 0 0}[0 0 0 1] prismatic slip are considerably lower than those for {2 over(1, ̄) over(1, ̄) 2}1/3〈2 over(1, ̄) over(1, ̄) over(3, ̄)〉 pyramidal slip, but are comparable to those for {2 over(1, ̄) over(1, ̄) 8}〈8 over(4, ̄) over(4, ̄) over(3, ̄)〉 twinning. The favored deformation modes are discussed on the basis of anisotropic elasticity theory of dislocations. © 2009 Acta Materialia Inc.
    Elsevier, Feb. 2010, Acta Materialia, 58(3) (3), 846 - 857, English

  • NORIHIKO L, OKAMOTO,TATSUYA KOYAMA, KYOSUKE KISHIDA, KATSUSHI TANAKA, HARUYUKI INUI
    2010, Journal of ELECTRONIC MATERIALS, 39(9) (9), 1640 - 1644, English
    [Refereed]
    Scientific journal

  • Norihiko Okamoto, Yutaka Hashimoto, Tatsuya Koyama, Hiroki Adachi, Kyosuke Kishida, Katsushi Tanaka, Haruyuki Inui
    Jan. 2010, MRS Proceedings, 1218, 55 - 60, English
    [Refereed]
    International conference proceedings

  • H. Inui, T. Oohashi, N.L. Okamoto, K. Kishida, K. Tanaka
    2010, Materials Science Forum, 638/642(Pt.2) (Pt.2), 1342 - 1347, English
    [Refereed]
    Scientific journal

  • Tetsuji Kume, Satoshi Ohno, Shigeo Sasaki, Hiroyasu Shimizu, Yasuo Ohishi, Norihiko L. Okamoto, Kyosuke Kishida, Katsushi Tanaka, Haruyuki Inui
    The phase transition and the vibrational properties of Ba8Ga16Ge30 have been investigated at high pressures up to 40 GPa at room temperature. The combined study of the high-pressure Raman and synchrotron powder x-ray diffraction (XRD) experiments revealed the occurrence of a first-order phase transition at 33 GPa, on which a volume decrease of about 3% was found. Rietveld refinements of the XRD data demonstrated the atomic displacements precursory to the phase transition, allowing us to discuss the mechanism of the phase transition. In the Raman experimental data, anomalies were observed in the spectral feature and the guest vibration around 17 GPa. By combining the Raman results with the XRD ones, the vibrational frequency of the guest Ba was investigated as a function of the host cage size. As a result, a linear relation between guest vibrational frequency and the guest-host distance was identified.
    AMER INST PHYSICS, Jan. 2010, JOURNAL OF APPLIED PHYSICS, 107(1) (1), 13517, English
    Scientific journal

  • H. Fukaya, Md. Moniruzzaman, Y. Murata, M. Morinaga, T. Koyama, W. Hashimoto, K. Tanaka, H. Inui
    Interdiffusion coefficients of Al replacing elements in Ni-Al-X (X=Ti, V and Nb) were estimated by a series of experiments using diffusion couples of Al rich pseudo-binary systems at three different temperatures of 1423, 1473 and 1523K. In order to obtain interdiffusion coefficients of the pseudo-binary systems, the experimental data was analyzed by the Sauer and Freise method, and also impurity diffusion coefficients of Ti, V and Nb in Ni3Al were estimated by applying the Darken-Manning equation. The magnitude of interdiffusion coefficient decreased in order of V, Ti and Nb at all three temperatures. Impurity diffusion coefficients were described by the expressions: D-n = 4.4x10(-1) exp(-422kJ mol(-1) / RT) D-v = 5.3x10(-2) exp(-387kJ mol(-1) / RT) , D-Nb = 2.1x10(+1) exp(-479kJ mol(-1) / RT) , The activation enthalpies obtained from the experimental data confirmed the retardation of Ti, V and Nb diffusion in Ni3Al by the anti-site diffusion mechanism. These results are consistent with our previous work on diffusion of Re and Ru in Ni3Al.
    TRANS TECH PUBLICATIONS LTD, 2010, DIFFUSION IN SOLIDS AND LIQUIDS V, PTS 1 AND 2, 297-301, 384 - +, English
    International conference proceedings

  • Norihiko L. Okamoto, Misato Kusakari, Katsushi Tanaka, Haruyuki Inui, Shigeki Otani
    The elastic constants and thermal expansivities in monocrystals of three transition-metal diborides with the AlB2 structure, CrB2, TiB2, and ZrB2, have been investigated in the temperature ranges from 300 to 1373 K and from 300 to 1073 K. The anisotropic parameters deduced from the measured elastic constants and thermal expansivities indicate that of the three diborides, the anisotropy is the most and least significant in CrB2 and ZrB2, respectively. The factors determining the significance in anisotropy in atomic bonding in AlB2-type diborides are analyzed by an approach similar to the valence-force-field method and are discussed in terms of the deformation of the electronic charge around the metal atoms occurring to fit themselves in the (0 0 0 1) basal plane. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
    PERGAMON-ELSEVIER SCIENCE LTD, Jan. 2010, ACTA MATERIALIA, 58(1) (1), 76 - 84, English
    Scientific journal

  • Norihiko L. Okamoto, Tatsuya Koyama, Kyosuke Kishida, Katsushi Tanaka, Haruyuki Inui
    Phase relationships of manganese-substituted ruthenium sesquisilicide alloys have been investigated by using X-ray powder diffraction and scanning and transmission electron microscopy. A series of chimney-ladder phases Ru1-xMnxSiy (0.14 <= x <= 0.97, 1.584 <= y <= 1.741) are formed over a wide compositional range between Ru2Si3 and Mn4Si7. The compositions of these chimney-ladder compounds deviate slightly from the composition line connecting Ru2Si3 and Mn4Si7, which corresponds to the ideal composition line satisfying VEC (valence electron counting) = 14 rule. The occurrence of this compositional deviation is discussed in terms of the VEC rule and the atomic packing. The thermoelectric properties of the directionally solidified Ru1-xMnxSiy alloys (0.55 <= x <= 0.90) have also been investigated as a function of the Mn content and temperature. The dimensionless figure of merit (ZT) for those alloys with a high Mn content (x <= 0.75) increased with the increase in Mn content. The ZT value for a crystal with x = 0.90 was as high as 0.76 at 874 K. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
    PERGAMON-ELSEVIER SCIENCE LTD, Oct. 2009, ACTA MATERIALIA, 57(17) (17), 5036 - 5045, English
    Scientific journal

  • Satoshi Fujio, Katsushi Tanaka, Haruyuki Inui, Rintaro Ueji, Naoto Sumida, Hideki Yamochi, Gunzi Saito
    The convergent-beam electron diffraction (CBED) method proposed recently for enantiomorph identification has been successfully applied to an ambient-pressure superconductor kappa-(BEDT-TTF)(2)Cu(NCS)(2) [BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene]. Enantiomorph identification (either the left-handed or right-handed form within the space group P2(1)) of each crystal grown of kappa-(BEDT-TTF)(2)Cu(NCS)(2) was achieved at ambient temperature without the need to cool the specimens. Enantiomorph identification was possible within the framework of the proposed method only by taking an additional selected-area electron diffraction pattern to eliminate the ambiguity of 180 degrees rotation of the relevant CBED pattern about the incident beam. In the present study, all four specimens investigated exhibit the right-handed form.
    WILEY-BLACKWELL, Jun. 2009, JOURNAL OF APPLIED CRYSTALLOGRAPHY, 42(3) (3), 433 - 441, English
    Scientific journal

  • Kyosuke Kishida, Akira Ishida, Tatsuya Koyama, Shunta Harada, Norihiko L. Okamoto, Katsushi Tanaka, Haruyuki Inui
    The thermoelectric properties of ternary and Al-containing quaternary Ru1-xRexSiy chimney-ladder phases have been studied as a function of the Re concentration with the use of directionally solidified alloys. The Ru1-xRexSiy chimney-ladder phases exhibit n- and p-type semiconducting behaviors, respectively, at low and high Re concentrations, at which the X(=Si)/M(=Ru + Re) ratios are respectively, larger and smaller than those expected from the VEC (valence electron concentration) = 14 rule increases, i.e. as the alloy composition deviates from that corresponding to the p-n transition (x approximate to 0.5), indicating that the carrier concentration can be controlled by changing the extent of compositional deviation from the ideal VEC = 14 composition. The highest values of the dimensionless figure of merit obtained are 0.47 for ternary (x = 0.60) and 0.56 for Al-containing quaternary alloys. The reasons for the systematic compositional deviation from the ideal VEC = 14 compositions observed for a series of chimney-ladder phases are discussed in terms of atomic packing. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
    PERGAMON-ELSEVIER SCIENCE LTD, Apr. 2009, ACTA MATERIALIA, 57(6) (6), 2010 - 2019, English
    Scientific journal

  • 28pYG-5 高圧力下における構造I型Ge系クラスレートの粉末X線回折およびラマン散乱(28pYG クラスレート・高圧,領域7(分子性固体・有機導体))
    久米 徹二, 大野 聡, 矢島 一平, 佐々木 重雄, 清水 宏晏, 岡本 範彦, 田中 克志, 乾 晴行, 大石 泰生
    Mar. 2009, 日本物理学会講演概要集, 64(1) (1), 837, Japanese

  • Toru Inoue, Katsushi Tanaka, Hiroki Adachi, Kyosuke Kishida, Norihiko L. Okamoto, Haruyuki Inui, Tadaharu Yokokawa, Hiroshi Harada
    The evolution of orientation distributions of gamma and gamma ' phases in crept Ni-base single crystal superalloys have been investigated by theoretical calculations with elastic-plastic models and by experiments. As creep deformation proceeds, the crystallographic orientation distributions for both phases are broadened as a result of the waving of the raft structure, which occurs to reduce the total mechanical energy. The broadening of the orientation distribution occurs in such a way that the 001 pole broadens isotropically while the hk0 poles broaden preferentially along the < 001 > directions. Since the extent of the broadening increases almost linearly with the number of creep deformation, the measurement of the broadening by X-ray diffraction can be utilized in non-destructive methods to predict the lifetime of Ni-base superalloys. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
    PERGAMON-ELSEVIER SCIENCE LTD, Feb. 2009, ACTA MATERIALIA, 57(4) (4), 1078 - 1085, English
    Scientific journal

  • Plastic Deformations in Single Crystals of FePd With the L1(0) Structure
    Katsushi Tanaka, Wang Chen, Kyosuke Kishida, Norihiko L. Okamoto, Haruyuki Inui
    Compressive deformations of L1(0)-ordered single crystals of FePd have been investigated from room temperature to 873 K. The critical resolved shear stress for superlattice dislocations is hard to determine resulting from buckling that occurs after a small amount of conventional plastic deformation. The CRSS for superlattice dislocations determined from yield stress is significantly larger than that of ordinary dislocations. The CRSS for octahedral glide of ordinary and superlattice dislocations are virtually independent of the temperature, and the positive temperature dependence of the yield stress is not observed for both, ordinary and superlattice dislocations, by the present experiments.
    MATERIALS RESEARCH SOCIETY, 2009, ADVANCED INTERMETALLIC-BASED ALLOYS FOR EXTREME ENVIRONMENT AND ENERGY APPLICATIONS, 1128, 543 - 548, English
    International conference proceedings

  • Plastic Deformation Behavior of Ti(5)Si(3) Single Crystals
    Kyosuke Kishida, Masakazu Fujiwara, Norihiko L. Okamoto, Katsushi Tanaka, Haruyuki Inui
    Deformation behavior of binary stoichiometric Ti(5)Si(3) single crystals was examined as a function of the loading axis orientation and temperature. Two different types of deformation modes, namely {1100}[0001] prism slip, {2112}1/3 < 2113 > pyramidal slip were newly identified to be activated above 1300 C depending on the loading axis orientation. Critical resolved shear stresses (CRSS) for the {1100} [0001] prism slip and {2112}1/3 < 2113 > pyramidal slip were estimated to be about 130 MPa and 330 MPa at 1400 degrees C, respectively. The values of the CRSS for these two slip systems decrease monotonously with increasing the temperature.
    MATERIALS RESEARCH SOCIETY, 2009, ADVANCED INTERMETALLIC-BASED ALLOYS FOR EXTREME ENVIRONMENT AND ENERGY APPLICATIONS, 1128, 537 - 542, English
    International conference proceedings

  • Physical and Mechanical Properties of Single Crystals of Co-Al-W Based Alloys with L1(2) Single-Phase and L1(2)/fcc Two-Phase Microstructures
    Haruyuki Inui, Katsushi Tanaka, Kyosuke Kishida, Norihiko L. Okamoto, Takashi Oohashi
    Single-crystal elastic constants of Co(3)(Al,W) with the cubic L1(2) structure have been experimentally measured by resonance ultrasound spectroscopy at liquid helium temperature. The values of all the three independent single-crystal elastic constants and polycrystalline elastic constants of Co(3)(Al,W) experimentally determined are 15 similar to 25% larger than those of Ni(3)(Al,Ta) but are considerably smaller than those previously reported. Two-phase microstructures with cuboidal L1(2) precipitates being well aligned parallel to < 100 > and well faceted parallel to {100} are expected to form very easily in Co-base superalloys because of the large value of E(111)/E(100) and c(ij) of Co(3)(Al,W). This is indeed confirmed by experiment. Values of yield stress obtained for both [001] and [123] orientations of L1(2)/fcc two-phase single crystals moderately decrease with the increase in temperature up to 800 degrees C and then decrease rapidly with temperature above 800 degrees C without any anomaly in yield stress. Slip on {111} is observed to occur for both orientations in the whole temperature range investigated.
    MATERIALS RESEARCH SOCIETY, 2009, ADVANCED INTERMETALLIC-BASED ALLOYS FOR EXTREME ENVIRONMENT AND ENERGY APPLICATIONS, 1128, 369 - 374, English
    International conference proceedings

  • Orientation Dependence of Microstructure and Electrochemical Properties of LiCoO(2) Cathode Films Deposited on Single-Crystalline La(2/3-x)Li(3x)TiO(3)
    Kengo Goto, Kyosuke Kishida, Yuji Yamaguchi, Norihiko L. Okamoto, Katsushi Tanaka, Haruyuki Inui, Shunji Takekawa, Yasutoshi Iriyama, Zempachi Ogumi
    Two different types of single-crystalline lithium lanthanum titanate (LLT) / LiCoO(2) assemblies were prepared by depositing HT-LiCoO(2) on the LLT surfaces of (110)(p) and ((1) over bar 12)(p) to investigate the effects of the orientation dependence of microstructures on the electrochemical properties of the assemblies. Cyclic voltammetry shows that the (110)(p) assembly exhibits very small peak separation between anodic and cathodic reactions, while the peak separation is considerably large in the case of the ((1) over bar 12)p assembly. In the HT-LiCoO(2) thin film cathode formed epitaxially on LLT, four differently-oriented domains can be formed under the orientation relationships Of (111)(p)//(0001)(LiCoO2) and < 110 >(p)//<11<(2)over bar>0>(LiCoO2) between LLT (macroscopically Cubic) and HT-LiCoO(2) (rhombohedral). The HT-LiCoO(2) domains with their layered structure aligned perpendicular to the interface are dominantly formed for the (110)(p) assembly, whereas those with the layered structure inclined about 20 degrees against the interface are dominantly grown for the ((1) over bar 12)(p) assembly. Such a selective growth behavior of the HT-LiCoO(2) on the LLT surface is considered to play an important role for the observed orientation dependence of the electrochemical properties of the LLT/LiCoO(2) assemblies.
    MATERIALS RESEARCH SOCIETY, 2009, SOLID-STATE IONICS-2008, 1126, 125 - 130, English
    International conference proceedings

  • Microstructures and Mechanical Properties of Co(3)(Al,W) With the L1(2) Structure
    Takashi Oohashi, Norihiko L. Okamoto, Kyosuke Kishida, Katsushi Tanaka, Haruyuki Inui
    Microstructures and deformation behavior of gamma/gamma' Co-Al-W single-crystals and gamma'-Co(3)(Al,W) polycrystals have been investigated. Single crystals with the gamma/gamma' two-phase microstructure with a large volume fraction of the gamma' phase are obtained by the Bridgman method These single crystals exhibit anomalies in yield stress in compression at temperatures above 700 degrees C. Polycrystalline Co(3)(Al,W) alloys can be rolled in ambient atmosphere such that the nominal thickness was reduced by 40%. The values of tensile elongation obtained for the polycrystalline Co(3)(Al,W) alloys in air is slightly smaller than that obtained in vacuum, indicating that the Co(3)(Al,W) alloys are not severely susceptible to the environmental embrittlement in air.
    MATERIALS RESEARCH SOCIETY, 2009, ADVANCED INTERMETALLIC-BASED ALLOYS FOR EXTREME ENVIRONMENT AND ENERGY APPLICATIONS, 1128, 221 - 226, English
    International conference proceedings

  • Mechanical and Thermal Properties of Single Crystals of Some Thermoelectric Clathrate Compounds
    Norihiko L. Okamoto, Takahiro Nakano, Kyosuke Kishida, Katsushi Tanaka, Haruyuki Inui
    The mechanical and thermal properties of single crystals of the type-I clathrate compounds Ba(8)Ga(16)Ge(30) and Sr(8)Ga(16)Ge(30) have been investigated by measuring the elastic constants, coefficients of thermal expansion (CTE) and plastic deformation behavior in compression. The feasibility of these two clathrate compounds as a thermoelectric material in terms of mechanical stability under possible thermal stresses is evaluated by calculating thermal stresses that are expected to develop within these compounds when used as thermoelectric devises.
    MATERIALS RESEARCH SOCIETY, 2009, ADVANCED INTERMETALLIC-BASED ALLOYS FOR EXTREME ENVIRONMENT AND ENERGY APPLICATIONS, 1128, 27 - 32, English
    International conference proceedings

  • Influence of Elastic Properties on the Morphology of the gamma' Precipitates in Ni-Base Superalloys
    Wataro Hashimoto, Katsushi Tanaka, Kyosuke Kishida, Norihiko L. Okamoto, Haruyuki Inui
    Influence of elastic properties on the morphology of the gamma' precipitates in Ni-base superalloys have been investigated by a theoretical and 3-dimantional elastic energy calculation Large elastic anisotropy makes the shape of the precipitates more angular. The difference in the elastic properties between the matrix and the precipitates also has a significantly effect on the shape of the precipitates.
    MATERIALS RESEARCH SOCIETY, 2009, ADVANCED INTERMETALLIC-BASED ALLOYS FOR EXTREME ENVIRONMENT AND ENERGY APPLICATIONS, 1128, 227 - 232, English
    International conference proceedings

  • K. Tanaka, S. Fujio, H. Inui, R. Ueji, N. Sumida
    The convergent-beam electron diffraction (CBED) method we proposed recently for enantiomorph identification has successfully been applied to some amino acid crystals such as glutamic acid and threonin. Enantiomorph identification (either left-handed or right-handed form) can readily be made within the framework of the proposed method by noting the asymmetric intensity distribution of Bijvoet pairs of reflections in the CBED pattern taken along an appropriate zone-axis orientation. Although the proposed method usually requires only a single CBED pattern, some effort to eliminate the ambiguity of 180°-rotation of the CBED pattern about the incident beam is needed for enantiomorph identification for these organic crystals because of the lack of HOLZ (higher-order Laue zone) reflection disks. © 2009 IOP Publishing Ltd.
    Institute of Physics Publishing, 2009, Journal of Physics: Conference Series, 165, English
    International conference proceedings

  • Crystal Structure and Thermoelectric Properties of Mn-Substituted Ru2Si3 With the Chimney-Ladder Structure
    Tatsuya Koyama, Norihiko L. Okamoto, Kyosuke Kishida, Katsushi Tanaka, Haruyuki Inui
    Phase relationships of manganese-substituted ruthenium sesquisilicide alloys have been investigated by using scanning and transmission electron microscopy. A series of chimney-ladder phases Ru1-xMnxSiy are formed over a wide compositional range between Ru2Si3 and Mn4Si7. The thermoelectric properties of the directionally solidified alloys with the nominal compositions of Ru1-xMnxSiy (0.55 <= x <= 0.90) have been investigated as a function of the Mn content and temperature. The thermoelectric power factor and dimensionless figure-of-merit (ZT) for the alloys with high Mn contents (x >= 0.75) increase with the increase in the Mn content. The ZT value for the crystal with x = 0.90 is as high as 0.76 at 874 K.
    MATERIALS RESEARCH SOC, 2009, ADVANCED INTERMETALLIC-BASED ALLOYS FOR EXTREME ENVIRONMENT AND ENERGY APPLICATIONS, 1128, 173 - 178, English
    International conference proceedings

  • Change in the Thermoelectric Properties With the Variation in the Defect Structure of ReSi(1.75)
    Shunta Harada, Katsushi Tanaka, Kyosuke Kishida, Norihiko L. Okamoto, Haruyuki Inui
    Crystal structure variation and thermoelectric properties of binary rhenium silicide with different heat treatment conditions are investigated. In quenched rhenium silicide, dense planar defects are observed and the crystal structure is identified as crystallographic shear structure with crystallographic shear operation of ((1) over bar 09)(C11b) / [100](C11b). The crystallographic shear structure observed in quenched samples is not thermally stable. The structure is annealed out by prolonged heat treatment at relatively low temperature. Thermoelectric properties of quenched and annealed rhenium silicide are significantly different. The quenched sample is an n-type semiconductor, while the annealed sample is a p-type semiconductor. Planar defects in the quenched sample are expected to introduce a donor level in the band gap and the electrical conduction becomes n-type.
    MATERIALS RESEARCH SOCIETY, 2009, ADVANCED INTERMETALLIC-BASED ALLOYS FOR EXTREME ENVIRONMENT AND ENERGY APPLICATIONS, 1128, 9 - 14, English
    International conference proceedings

  • K. Tanaka, T. Ichitsubo, K. Kishida, H. Inui, E. Matsubara
    A condition for destabilizing the raft structure has been deduced from elastic energy calculations with the concept of "effective eigen-strain", where the effect of creep deformation is included in addition to the lattice mismatch. The calculations indicate that the 001 raft structure is stabilized by a small amount of creep deformation but becomes unstable when the creep strain in the gamma phase exceeds the magnitude required to fully relax the lattice mismatch. The excess creep strain is required to produce all internal elastic field that supresses further creep deformation, and has to be introduced in the primary creep stag. Via the instability of the 001 raft structure, the raft structure gradually turns into a wavy one in the second creep stage before its collapse. (c) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
    PERGAMON-ELSEVIER SCIENCE LTD, Sep. 2008, ACTA MATERIALIA, 56(15) (15), 3786 - 3790, English
    Scientific journal

  • T. Ichitsubo, E. Matsubara, K. Miyagi, W. Itaka, K. Tanaka, S. Hosokawa
    We have recently shown that the sound velocity obtained from the inelastic x-ray scattering (IXS) measurement exceeds the ultrasonic wave velocity of a Pd-based metallic glass in a rigid glass state far below its glass transition temperature. Here we report that no obvious evidence of faster processes, which are supposed to be an origin of the phenomenon, was detected in the low-temperature dependence of the elastic moduli and internal friction of the Pd-based metallic glass showing such a positive dispersion. The longitudinal elastic modulus at low temperatures, where any processes are considered frozen out, is less than the elastic modulus deduced from the IXS measurement at room temperature. These suggest that the positive dispersion observed in this metallic glass is not a time-dependent phenomenon.
    AMER PHYSICAL SOC, Aug. 2008, PHYSICAL REVIEW B, 78(5) (5), 1 - 52202, English
    Scientific journal

  • Norihiko L. Okamoto, Takahiro Nakano, Katsushi Tanaka, Haruyuki Inui
    The mechanical and thermal properties of single crystals of the type-I clathrate compounds Ba(8)Ga(16)Ge(30) and Sr(8)Ga(16)Ge(30) have been investigated by measuring the elastic constants, coefficients of thermal expansion (CTE), and plastic deformation behavior in compression. The values of bulk moduli extrapolated to 0 K for Ba(8)Ga(16)Ge(30) and Sr(8)Ga(16)Ge(30) are almost identical to each other, whereas the values of Young and shear moduli for Ba(8)Ga(16)Ge(30) are larger than those for Sr(8)Ga(16)Ge(30). The values of polycrystalline moduli for both Ba(8)Ga(16)Ge(30) and Sr(8)Ga(16)Ge(30) are all considerably smaller than those for pure germanium. The values of CTE for Ba(8)Ga(16)Ge(30) and Sr(8)Ga(16)Ge(30) are virtually identical with each other, but they are considerably larger than that of pure germanium. The feasibility of these two clathrate compounds as a thermoelectric material in terms of mechanical stability under possible thermal stresses is evaluated by calculating thermal stresses that are expected to develop within these compounds when used as a thermoelectric material in thermoelectric devises. (c) 2008 American Institute of Physics.
    AMER INST PHYSICS, Jul. 2008, JOURNAL OF APPLIED PHYSICS, 104(1) (1), 13529, English
    Scientific journal

  • Variation in the Einstein temperature of guest atoms in Ba-Ge-X type-III clathrate compounds
    Katsushi Tanaka, Jung-Hwan Kim, Kyosuke Kishida, Haruyuki Inui
    Einstein temperatures of guest atoms in Ba-Ge-(Al, In) type-III clathrate compounds have been estimated from the temperature dependence of the atomic displacement parameters determined by synchrotron X-ray powder diffractions. The lowest temperature is obtained for the vibration of Ba(2) atoms along the x-direction, which corresponds to the "rattling motion" of the guest atoms in the compounds. The temperature estimated is significantly low of about 50 K which agrees with the fact that the compounds have small lattice thermal conductivities of about 0.6 W/mK. Though the lattice thermal conductivity of Ba24Ge88Al12 is larger than that of Ba24Ge88In12, the Einstein temperature of Ba24Ge88Al12 is slightly smaller than that of Ba24Ge88In12. This discrepancy can be explained by the consideration of higher Debye temperature of Ba24Ge88Al12 than that of Ba24Ge88Al12, that is, lattice thermal conductivity without "rattling motion" is larger for Ba24Ge88Al12 than that for Ba24Ge88In12.
    MATERIALS RESEARCH SOCIETY, 2008, THERMOELECTRIC POWER GENERATION, 1044, 223 - 228, English
    International conference proceedings

  • Kyosuke Kishida, Yuji Yamaguchi, Katsushi Tanaka, Haruyuki Inui, Sho Tokui, Kazuhiro Ishikawa, Kiyoshi Aoki
    The microstructures and hydrogen permeability properties were investigated for Nb-NiTi eutectic alloys directionally solidified in an optical floating zone furnace. Rod-type eutectic microstructures with Nb rods aligned parallel to the growth direction are obtained with an alloy having a composition of Nb-41Ni-40Ti grown at relatively slow growth rates below 2.5 mm/h. The hydrogen permeability depends on the relative direction of aligned Nb rods within the membrane. The values for the specimens with Nb rods aligned perpendicular to the membrane surface are about an order of magnitude larger than those for the specimens with Nb rods parallel to the surface. The largest value for the former specimen is as high as 2.60 x 10(-8) mol H(2)m(-1) s(-1) Pa-1/2 (673 K), which is more than twice that reported for the as-cast Nb-NiTi eutectic alloy. No hydrogen embrittlement is observed between 573 and 673 K, indicating that the Nb-NiTi eutectic structure suppresses hydrogen embrittlement of Nb during hydrogen permeation. (c) 2007 Elsevier Ltd. All rights reserved.
    ELSEVIER SCI LTD, Jan. 2008, INTERMETALLICS, 16(1) (1), 88 - 95, English
    Scientific journal

  • Kyosuke Kishida, Mai Miyata, Naoyuki Wada, Norihiko L. Okamoto, Katsushi Tanaka, Haruyuki Inui, Hiroshi Koyama, Takeshi Hattori, Yasutoshi Iriyama, Zempachi Ogumi
    The crystal and defect structures of coarse-grained crystals of La2/3-x Li-3x TiO3 grown from the melt by the TammannStber method were studied by transmission electron microscopy and powder X-ray diffraction. The as-grown crystals of La2/3-x Li-3x TiO3 have a Li-poor composition of La-0.57 Li-0.29 TiO3 and a diagonal-type unit cell of 2(1/2)a(p) x 2(1/2)a(p) x 2a(p) with the tetragonal symmetry space group: P4/nbm <#125 >] due to both the La-cation ordering and the tilting of TiO6 octahedra. The secondary La2Ti2O7 phase precipitates in the form of plates in the La2/3-x Li-3x TiO3 phase with the orientation relationships of < 001 > p//[100]La2Ti2O7 and {110}p//< 001 > La2Ti2O7, which may cause detrimental effects to ionic conductivity.
    OXFORD UNIV PRESS, Dec. 2007, JOURNAL OF ELECTRON MICROSCOPY, 56(6) (6), 225 - 234, English
    Scientific journal

  • Jung-Hwan Kim, Norihiko L. Okamoto, Kyosuke Kishida, Katsushi Tanaka, Haruyuki Inui
    The crystal structure and thermoelectric properties of type-III clathrate compounds in the Ba-In-Ge system have been investigated as a function of In content. The solid solubility of In in the type-III clathrate compounds is determined to be about X=15 when expressed with the formula of Ba24InXGe100-X. Similar to our recent results obtained for type-III clathrate compounds in Ba-Al-Ge and Ba-Ga-Ge systems, values of electrical resistivity, Seebeck coefficient, and electronic thermal conductivity of those in the Ba-In-Ge system generally increase with the increase in the In content because of the decrease in the number of excess electrons as described with the simple Zintl concept. The changes in their lattice thermal conductivity with the In content are explained in terms not only of the low rattling frequency of the guest atom but also of the low Debye temperature of the cage framework. (C) 2007 American Institute of Physics.
    AMER INST PHYSICS, Nov. 2007, JOURNAL OF APPLIED PHYSICS, 102(9) (9), 94506, English
    Scientific journal

  • Katsushi Tanaka, Takashi Ohashi, Kyosuke Kishida, Haruyuki Inui
    Single-crystal elastic constants of Co-3(Al, W) with cubic L1(2) structure have been experimentally measured by resonance ultrasound spectroscopy at liquid helium temperature. The values of all three independent single-crystal elastic constants and polycrystalline elastic constants of Co-3(Al, W) experimentally determined are 15%-25% larger than those of Ni-3(Al, Ta) but are considerably smaller than previously calculated values of the constants. When judged from the values of Poisson's ratio, Cauchy pressure, and G(h)/B-h, the ductility of Co-3(Al, W) is expected to be sufficiently high so that Co-3(Al, W) can be practically used as the constituent phase of "Co-base superalloys." (C) 2007 American Institute of Physics.
    AMER INST PHYSICS, Oct. 2007, APPLIED PHYSICS LETTERS, 91(18) (18), English
    Scientific journal

  • Jung-Hwan Kim, Norihiko L. Okamoto, Kyosuke Kishida, Katsushi Tanaka, Haruyuki Inui
    The then-noelectric properties of type-III clathrate compounds in the Ba-Al-Ge system have been investigated as a function of At content. The solid solubility of At in the type-III clathrate compounds is determined to be slightly less than X= 12 when expressed with the formula of Ba24AlxGe100-x. As the At content increases, values of electrical resistivity and Seebeck coefficient increase, while that of lattice thermal conductivity decreases. The changes in electrical resistivity and Seebeck coefficient with the At content are explained in terms of the change in the number of excess electrons upon alloying with At, which can be described with the simple Zintl concept. The changes in lattice thermal conductivity with the Al content are explained in terms of the very low vibration frequency for the rattling motion of the Ba guest atom, which is caused by the increased size of the encapsulating cage of open dodecahedron upon alloying with Al. (c) 2007 American Institute of Physics.
    AMER INST PHYSICS, Aug. 2007, JOURNAL OF APPLIED PHYSICS, 102(3) (3), 34510, English
    Scientific journal

  • K. Kishida, N. Wada, H. Adachi, K. Tanaka, H. Inui, C. Yada, Y. Irlyama, Z. OgUini
    Two different types of lithium lanthanum titanate (LLT)/LiCoO2 assemblies were produced by depositing the LiCoO2 cathode on the cleaved or polished surfaces of polycrystalline LLT to investigate the effects of the LLT/LiCoO2 interface structure on the electrochemical properties of the assemblies. The microstructures and electrochemical properties of the assemblies were investigated as a function of charge/discharge cycle number. Cyclic voltammetry indicates that anodic and cathodic peaks shift to higher and lower potentials, respectively, with cycle number for the assembly produced with the cleaved LLT, whereas these potential changes are negligibly small for that produced with the mechanically polished LLT. LiCoO2 is formed epitaxially on LLT with the orientation relationships (110)(LLT)// (11 (2) over bar0)(LiCoO2) and [001](LLT)//. A complete set of elastic constants has been determined with the resonance ultrasound spectroscopy technique. The disordered alloy exhibits common features of usual fcc metals, and the ordered alloy clearly shows a tetragonal elastic anisotropy, c(11)<c(33) and c(44)<c(66). The temperature dependence of the moduli has also been investigated using a quenched disordered sample. The anisotropy factor 2c(44)/(c(11)-c(12)) is fairly large (about 3.0) at any temperatures, which may be related with the tweed pattern formation observed experimentally in the early stage of ordering. (C) 2004 American Institute of Physics.
    AMER INST PHYSICS, Dec. 2004, JOURNAL OF APPLIED PHYSICS, 96(11) (11), 6220 - 6223, English
    Scientific journal

  • INUI Haruyuki, FUJII Akihiro, SAKAMOTO Hiroki, TANAKA Katsushi
    The Japanese Society of Microscopy, Nov. 2004, Denshi kenbikyo, 39(3) (3), 162 - 167, Japanese

  • T Mehaddene, Pierron-Bohnes, V, M Zemirli, R Caudron, K Tanaka, H Numakura
    The local atomic arrangement was investigated by neutron diffuse scattering in a FePd single crystal at 1020 K. The measurements were carried out in the (10 0) and (I 10) reciprocal planes using a time-of-flight analysis to separate elastic and inelastic contributions. A set of Warren-Cowley short-range order (SRO) parameters (alpha(i); i = 1, 14) were obtained by fitting the data using the Borie-Sparks formulation. We mainly find a large Positive alpha(2) SRO parameter (attractive interaction between identical atoms). The Krivoglaz-Clapp-Moss approximation, used to estimate the effective pair interaction energies, leads to a strong negative value of the interaction V-2 between second nearest neighbors. (C) 2004 Elsevier B.V. All rights reserved.
    ELSEVIER SCIENCE SA, Sep. 2004, JOURNAL OF ALLOYS AND COMPOUNDS, 378(1-2) (1-2), 294 - 297, English
    Scientific journal

  • Defect structures in cosputtered thin films of transition-metal disilicides with C11(b), C40 and C54 structures
    H Inui, T Hashimoto, A Fujii, H Sakamoto, NL Okamoto, K Tanaka, M Yamaguchi
    Defect structures in crystallites of the stable phases in thin films of transition-metal (TM) disilicides (C11(b) MoSi2, C40 TaSi2, and C54 TiSi2) produced by cosputtering and subsequent annealing have been investigated by transmission electron microscopy (TEM). Crystallites in thin films of MOSi2, TaSi2, and TiSi2 all contain planar faults parallel to hexagonally arranged TMSi2 planes, which are a characteristic feature commonly observed in all three crystal structures. These planar faults are twin boundaries in all cases. Twins in thin films of these disilicides, thus, have a common characteristic that the twin habit plane is parallel to hexagonally arranged TMSi2 stoichiometric planes. For twins in thin films of C11(b) MOSi2, and C54 TiSi2, the twining elements can be deduced and the twin habit plane is found not to be parallel to the twinning (K-1) plane, but to be perpendicular to it. Twins formed in C40 TaSi2 thin films are different from those formed in C11(b) MOSi2 and C54 TiSi2 thin films, in that the crystal orientation of the twin is exactly the same as that of the matrix, since they are racemic twins that are only enantiomorphically (space groups of P6(2)22 or P6(4)22) related to each other.
    MINERALS METALS MATERIALS SOC, Aug. 2004, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, 35A(8) (8), 2229 - 2238, English
    Scientific journal

  • T Mehaddene, M Zemirli, Pierron-Bohnes, V, MC Cadeville, B Hennion, A Marty, Schuster, I, K Tanaka, H Numakura
    The frequencies of the normal modes of vibration of FePd single crystal have been measured using inelastic neutron scattering. The measurements were performed for the L1(0) ordered structure at 300 and 860 K and for the fcc disordered state at 1020 K. A general lowering of phonon frequencies with increasing temperature is found in FePd, the dependence being the strongest for acoustical transverse [xixixi] branches. The migration energies as well as several thermodynamic quantities have been calculated from the densities of states. The contribution of ordering to the migration energy, as experimentally determined in this work, agrees well with the obtained one by Monte Carlo simulations in the L1(0) structure. (C) 2003 Elsevier B.V. All rights reserved.
    ELSEVIER SCIENCE BV, Mar. 2004, CATALYSIS TODAY, 89(3) (3), 313 - 318, English
    Scientific journal

  • T Mehaddene, E Kentzinger, B Hennion, K Tanaka, H Numakura, A Marty, Parasote, V, MC Cadeville, M Zemirli, Pierron-Bohnes, V
    The frequencies of the normal modes of vibration of CoPt3 and FePd single crystals have been measured using inelastic neutron scattering. The measurements were performed in the L1(2) ordered phase (at 300 and 930 K) for CoPt3 and in the L1(0) ordered phase (at 300 and 860 K) for FePd. Dispersion curves were also measured in the fcc disordered states, at 1060 and 1020 K for CoPt3 and FePd, respectively. The activation enthalpy of atomic migration has been evaluated from the phonon density of states by applying Schober's model [H. R. Schober , J. Phys.: Condens. Matter 4, 9321 (1992)] and its extension to the L1(2) ordered structure. The phonon properties of FePd3 reported in the literature have been analyzed similarly and are compared with the results for CoPt3 and FePd. The contribution of the long-range order to the migration enthalpy estimated in the present analyses agrees well in magnitude with the previous evaluation by Monte Carlo simulation for alloys of the fcc, L1(2), and L1(0) structures.
    AMER PHYSICAL SOC, Jan. 2004, PHYSICAL REVIEW B, 69(2) (2), 024304, English
    Scientific journal

  • T Ichitsubo, K Tanaka, M Koujina, M Kawashima, M Hirao
    In this paper, we report the feasibility of controlling the nanostructure of magnetic thin films using a strong magnetic field. The effects of magnetic field on the structures of FePt ultrathin films (about 1 nm) and on the coercivity of FePt(/FePt3) thick films (about 300 nm) have been examined. These films were sputter-deposited on Si substrates at room temperature, and subsequently were annealed under a strong magnetic field of 100 kOe (10 T). The film structure and magnetic property of the resulting films are fairly affected by an applied magnetic field.
    INST PURE APPLIED PHYSICS, Jan. 2004, JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, 43(1) (1), 273 - 276, English
    Scientific journal

  • Crystallographic features of rhenium disilicide
    K Tanaka, H Inui, T Ohba, S Tsutsui, M Mizumaki
    Crystallographic features of Rhenium disilicide have been examined by powder and single-crystal X-ray diffractometry with a synchrotron radiation. The chemical composition of the compound is determined as Re4Si7 (ReSi2-x, x = 0.25) from lattice constants and specific density determined. The structure is defined as a vacancy ordered structure with the space group of Cm. The positions of the constituent atoms in the structure have been refined. The positions of silicon atoms apparently shift from the ideal positions of the C11(b) structure which is the structure without containing structural vacancies.
    MATERIALS RESEARCH SOCIETY, 2004, THERMOELECTRIC MATERIALS 2003-RESEARCH AND APPLICATIONS, 793, 305 - 310, English
    International conference proceedings

  • Convergent-Beam Electron Diffraction Method for Chiral Identification of Enantiomorphic Crystals
    TANAKA KATSUSHI
    2004, Trans. MRS-J., Vol. 29,(No. 1) (No. 1), 13 - 18, English
    Scientific journal

  • Y Nose, A Kushida, T Ikeda, H Nakajima, K Tanaka, H Numakura
    The phase boundaries pertaining to gamma(2) (FePt) and gamma(3) (FePt3) phases in the Fe-Pt system have been re-exammed by measuring (1) the compositions of interphase boundaries in diffusion couples, (2) the equilibrium compositions in two-phase alloys and (3) the electrical resistivity as a function of temperature. The results obtained by the three methods are consistent with each other. The gamma (fcc solid solution) <----> gamma(2) + gamma(3) eutectoid has been found to be located at a point higher in Pt concentration and lower in temperature than in the currently adopted phase diagram, the stability range of the gamma(2) phase exhibits considerable asymmetry. Other phase boundaries, as well as the ferromagnetic <----> paramagnetic transition in the gamma(2) phase detected by the resistivity measurements, are in fair agreement with the data in the literature.
    JAPAN INST METALS, Dec. 2003, MATERIALS TRANSACTIONS, 44(12) (12), 2723 - 2731, English
    Scientific journal

  • H Inui, A Fujii, K Tanaka, H Sakamoto, K Ishizuka
    A new CBED (convergent-beam electron diffraction) method is proposed for the identification of the chirality of enantiomorphic crystals, in which asymmetry in the intensity of the reflections of Bijvoet pairs in an experimental symmetrical zone-axis CBED pattern is compared with that of a computer-simulated CBED pattern. The intensity difference for reflections of these Bijvoet pairs results from multiple scattering ( dynamical nature of electron diffraction) among relevant Bijvoet pairs of reflections, each pair of which has identical amplitude and different phase angles. Therefore, the crystal thickness where chiral identification is made with the present method is limited by the extinction distance of Bijvoet pairs of reflections relevant to multiple scattering to produce the intensity asymmetry, which is usually of the order of a few tens of nanometers. With the present method, a single CBED pattern is sufficient and chiral identification can be made for all the possible enantiomorphic crystals that are allowed to exist in crystallography.
    BLACKWELL MUNKSGAARD, Dec. 2003, ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE, 59(6) (6), 802 - 810, English
    Scientific journal

  • K Tatsumi, Tanaka, I, K Tanaka, H Inui, M Yamaguchi, H Adachi, M Mizuno
    Elastic constants of LaNi5H7 and LaNi5 are calculated by a first principles pseudopotential method using plane-wave basis sets. Some extra calculations using model clusters were made in order to discuss the magnitude of chemical bondings. Inner displacements associated with all deformation modes are taken into account. Elastic constants are smaller and more isotropic in the hydride than those in the host. The electronic mechanism to determine the change in the elastic properties is investigated from the viewpoint of chemical bonding. Strong Ni-H bonds are formed in LaNi5H7 at the expense of Ni-Ni bonds. They play key roles in determining the elastic properties. The isotropic distribution of the Ni-H bonding charge in LaNi5H7 should be responsible for the isotropic elastic constants. Hydrogen atoms are found to relax considerably during the deformation to maintain the Ni-H bond length. When the inner displacements are ignored, the elastic constants of LaNi5H7 are as large as those of LaNi5. However, the remarkable displacement of hydrogen atoms during the elastic deformation plays an essential role in softening by hydrogenation.
    IOP PUBLISHING LTD, Oct. 2003, JOURNAL OF PHYSICS-CONDENSED MATTER, 15(38) (38), 6549 - 6561, English
    Scientific journal

  • T Ichitsubo, D Koumoto, M Hirao, K Tanaka, M Osawa, T Yokokawa, H Harada
    The elastic constants of the rafted Ni-base single-crystal superalloy, TMS-26, at high temperatures (similar to1000 degreesC) have been studied with acoustic resonance methods. The rafted superalloy can be regarded as an elastic body of tetragonal symmetry. The elastic anisotropy factors, c(11)/c(33) and E-100/E-001, increase with temperature up to 1.010-1.025. Although a micromechanics model can reproduce this trend, the calculated anisotropy (similar to1.001) is much smaller than the measurements, which can be related with the internal strain due to the lattice misfit. The elastic anisotropy of E-001 < E-100 = E-010 contributes to the transverse rafting under external stress. (C) 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
    PERGAMON-ELSEVIER SCIENCE LTD, Sep. 2003, ACTA MATERIALIA, 51(16) (16), 4863 - 4869, English
    Scientific journal

  • T Ichitsubo, D Koumoto, M Hirao, K Tanaka, M Osawa, T Yokohawa, H Harada
    Rafting mechanism in Ni-base single-crystal superalloys has been discussed with the total mechanical energy calculated for typical microstructures. We found that the actual rafting phenomena cannot be explained within the coherent elastic regime. The present calculations reveal that (i) only the transverse rafted structure with laminates normal to the stress direction can be realized, regardless of tensile or compressive stresses, and (ii) the lattice misfit is not relevant to the choice of the rafted structures. However, when the eigenstrain of the spherical (dilatational) symmetry changes into that of the tetragonal symmetry with misfit dislocations on the gamma/gamma' interfaces, the signs of lattice misfit and external stress govern the choice of the transverse or longitudinal rafts. It is concluded that the rafting belongs to an elastic-plastic phenomenon. (C) 2003 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.
    PERGAMON-ELSEVIER SCIENCE LTD, Aug. 2003, ACTA MATERIALIA, 51(14) (14), 4033 - 4044, English
    Scientific journal

  • T Hayashi, K Ito, K Tanaka
    High purity single crystals of the Mo5Si3C phase with the D8(8) type structure have been grown and their physical and mechanical properties have been measured. The composition of single crystals is Mo4.66Si3.00C0.402. Lattice constants of the compound are a = 0.7286 nm and c = 0.5046 nm. Vickers micro-hardness and fracture toughness are 13.4 MPa and 1.3 MPa m(1/2), respectively. The anisotropy ratio of thermal expansion coefficient (alpha(c)/alpha(a)) of the compound is approximately 2 at 773 K. In contrast, the elastic properties for the compound are nearly isotropic. The deformation behavior of the compound has been studied in compression using [0001], [1340] [2249] oriented single crystals. These single crystals can be deformed plastically at temperatures higher than 1573 K. Slip occurs on {0001} <11 (2) over bar0> and an unidentified non-basal system. (C) 2003 Elsevier Ltd. All rights reserved.
    ELSEVIER SCI LTD, Aug. 2003, INTERMETALLICS, 11(8) (8), 835 - 840, English
    Scientific journal

  • T Ichitsubo, S Kai, H Ogi, M Hirao, K Tanaka
    Elastic and anelastic properties of Zr55Al10Ni5Cu30 bulk glass have been investigated at high temperatures with the electromagnetic acoustic resonance technique within the frequency range of 300-1500 kHz. The elastic constants of ascast sample decrease monotonically up to the glass transition temperature T-g and jump up just above T-g, but such jumps disappear in the cooling and subsequent heating processes. This indicates that an irreversible structural stabilization occurs at T-g under ultrasound vibration. As for ultrasonic attenuation, prominent peaks appear at T, in the first heating process. These attenuation peaks can be attributed to the atom movements in the initial glassy state. (C) 2003 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.
    PERGAMON-ELSEVIER SCIENCE LTD, Aug. 2003, SCRIPTA MATERIALIA, 49(4) (4), 267 - 271, English
    Scientific journal

  • K Tanaka, K Morioka
    Shape recovery through L1(0)-fcc order-disorder transformation of FePd is examined. Under a uniaxial compressive stress, a reversible shape change associated with the order-disorder transformation is observed. Shape memory characteristics (transformation strain, time required for the transformation and temperature hysteresis) for single-crystal and polycrystal specimens are determined by a compression test under a constant stress. The transformation strain (4% for a single crystal) and time required for disordering (about 10 s for a. single crystal) are comparable with those of conventional martensitic shape memory alloys. The alloys can be used as shape memory materials with relatively high transformation temperature.
    TAYLOR & FRANCIS LTD, May 2003, PHILOSOPHICAL MAGAZINE, 83(15) (15), 1797 - 1806, English
    Scientific journal

  • T Hashimoto, H Inui, K Tanaka, M Yamaguchi
    The phase transformation behavior in binary and some ternary TiSi2 thin films produced by co-sputtering has been investigated as a function of annealing temperature, in an attempt to reduce the C49-->C54 phase transformation temperature by increasing the relative stability of the C54 modification with respect to the C49 modification through ternary alloying. Ternary elements investigated include Nb, Mo and Au, all of which have an electronegativity greater than that of Ti and thus are expected to increase the relative stability of the C54 modification by increasing the covalency of the C54 modification. The C49-->C54 phase transformation temperature is indeed found to decrease by 50 degreesC for Nb- and Mo-bearing thin films and by 100 degreesC for Au-bearing thin films when compared to that for binary thin films. The reduction in the phase transformation temperature by ternary alloying is in increasing order of the electronegativity of the ternary elements investigated. Thus, the electronegativity of ternary elements is found to be a good guide for controlling the relative stability of the C54 modification with respect to the C49 modification and therefore for controlling the C49-->C54 phase transformation temperature. (C) 2003 Elsevier Science Ltd. All rights reserved.
    ELSEVIER SCI LTD, May 2003, INTERMETALLICS, 11(5) (5), 417 - 424, English
    Scientific journal

  • H Inui, A Fujii, T Hashimoto, K Tanaka, M Yamaguchi, K Ishizuka
    Phase transformation and defect structures in thin-film TaSi2 produced by co-sputtering have been investigated as a function of annealing temperature by transmission electron microscopy. Crystallization of amorphous TaSi2 thin films occurs at 400 degreesC without forming any metastable phases. Most of C40 TaSi2 crystallites contain planar faults parallel to (0001) basal planes. Convergent-beam electron diffraction (CBED) indicates that these planar faults are not simple stacking faults but are twin boundaries bounded by two adjacent enantiomorphically-related twin domains; i.e., domains belonging to the space groups P6(2)22 (right-handed) and P6(4)22 (left-handed) having the identical crystal orientation arrange alternatively separated by twin boundaries parallel to (0001). The formation of these enantiomorphically-related domains in TaSi2 thin films with the hexagonal C40 structures is discussed in comparison with the formation of twin-related domains in MoSi2 (the tetragonal C11(b) structure) and TiSi2 (the orthorhombic C54 structure) thin films. A new CBED method is proposed for identification of enantiomorphically-related crystals, in which asymmetry in the intensity of Bijvoet pairs of FOLZ disks in an experimental symmetrical zone-axis CBED pattern is compared with that in a computer simulated CBED pattern. (C) 2003 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.
    PERGAMON-ELSEVIER SCIENCE LTD, May 2003, ACTA MATERIALIA, 51(8) (8), 2285 - 2296, English
    Scientific journal

  • Haruyuki Inui, Norihiko L. Okamoto, Takashi Hashimoto, Katsushi Tanaka, Masaharu Yamaguchi
    The defect structures in orthorhombic C54 crystallites in thin films of Mo-doped TiSi2 produced by co-sputtering have been investigated by transmission electron microscopy. Almost all C54 crystallites contain a twin boundary parallel to (101), dividing a crystallite into two regions, each of which also contains many thin twins with the habit plane parallel to (001), which is inclined by about 45° from (101). Both of the two regions divided by the twin boundary parallel to (101) tend to have facets on (001) as well as thin twins with the habit plane parallel to (001). As a result, C54 crystallites exhibit a characteristic shape just like an oak leaf. While twins with the (001) habit plane have been observed in C54 crystallites in both binary and Mo-doped TiSi2 thin films, those with the (101) habit plane are present only in Mo-doped TiSi2 thin films. The twinning elements for (101) twins are determined to be K1 = (101), η 1 = [1̄01], K2 = (001) and η2 = [100]. The origin of (101) twins in Mo-doped TiSi2 is discussed in terms of the change in the c/a axial ratio upon alloying TiSi2 with Mo.
    Apr. 2003, Philosophical Magazine, 83(12) (12), 1463 - 1478, English
    [Refereed]
    Scientific journal

  • H Inui, NL Okamoto, T Hashimoto, K Tanaka, M Yamaguchi
    The defect structures in orthorhombic C54 crystallites in thin films of Mo-doped TiSi2 produced by co-sputtering have been investigated by transmission electron microscopy. Almost all C54 crystallites contain a twin boundary parallel to (101), dividing a crystallite into two regions, each of which also contains many thin twins with the habit plane parallel to (001), which is inclined by about 45 from (101). Both of the two regions divided by the twin boundary parallel to (101) tend to have facets on (001) as well as thin twins with the habit plane parallel to (001). As a result, C54 crystallites exhibit a characteristic shape just like an oak leaf. While twins with the (001) habit plane have been observed in C54 crystallites in both binary and Mo-doped TiSi2 thin films, those with the (101) habit plane are present only in Mo-doped TiSi2 thin films. The twinning elements for (101) twins are determined to be K-1 = (101), eta(1) = [(1) over bar 01], K-2 = (001) and eta(2) = [100]. The origin of (101) twins in Mo-doped TiSi2 is discussed in terms of the change in the c/a axial ratio upon alloying TiSi2 with Mo.
    TAYLOR & FRANCIS LTD, Apr. 2003, PHILOSOPHICAL MAGAZINE, 83(12) (12), 1463 - 1478, English
    Scientific journal

  • JJ Gu, K Kuwabara, K Tanaka, H Inui, M Yamaguchi, A Yamamoto, T Ohta, H Obara
    The crystal structure of the defect disilicide formed with Re (ReSi1.75) has been refined by transmission electron microscopy combined with first-principles calculation. The crystal structure is monoclinic with the space group Cm (mc44) due to an ordered arrangement of vacancies on Si sites in the underlying (parent) C11(b) lattice. The thermoelectric properties of ReSi1.75 are highly anisotropic. Its electrical conduction is of n-type when measure along [001] while it is of p-type when measured along [100]. Although the value of Seebeck coefficient along [100] is moderately high (150-200 muV/K), it is very high along [001] (250-300 muV/K). As a result, a very high value of dimensionless figure of merit (ZT) of 0.7 is achieved at 1073 K when measured along [001].
    MATERIALS RESEARCH SOCIETY, 2003, DEFECT PROPERTIES AND RELATED PHENOMENA IN INTERMETALLIC ALLOYS, 753, 501 - 506, English
    [Refereed]
    International conference proceedings

  • NL Okamoto, M Kusakari, K Tanaka, H Inui, M Yamaguchi, S Otani
    Coefficients of thermal expansion (CTE) and elastic constants of single crystals of ZrB2 have been determined in the temperature ranges from room temperature to 1073 K and from room temperature to 1373 K, respectively. The elastic constants of ZrB2 are best characterized by the large value of the Young modulus (as high as 500 GPa) and the small values of the Poisson ratio (0.13-0.15), indicating the high stiffness and hardness and the brittleness, respectively. The values of CTE along the a- and c-axis directions are 6.66 x 10(-6) and 6.93 x 10(-6) K-1, respectively, when averaged over the temperature range from room temperature to 1073 K. The CTE value along the a- axis direction of ZrB2 is only moderately larger than the corresponding value for GaN. This together with the small lattice mismatch along the a-axis direction between ZrB2 and GaN in the heteroepitaxial orientation relationship of (0001)(GaN) / / (0001) ZrB2 and [11 (2) over bar0](GaN) //[11 (2) over bar0](ZrB2) indicate that only a small compressive stress develops in the GaN thin-film crystal grown on the (0001) surface of the ZrB2 substrate. The stresses developed in the GaN thin-film crystal are evaluated with the values of CTE and elastic constants of ZrB2 determined in the present study. The evaluation verifies the suitability of ZrB2 as a substrate for heteroepitaxial growth of GaN. (C) 2003 American Institute of Physics.
    AMER INST PHYSICS, Jan. 2003, JOURNAL OF APPLIED PHYSICS, 93(1) (1), 88 - 93, English
    Scientific journal

  • Physical and mechanical properties of Mo5X3+alpha (X=Si, B, C) single crystals
    T Hayashi, K Ito, K Tanaka, M Yamaguchi
    Mo5X3+alpha (X=Si, B, C) intermetallic compounds such as Mo5SiB2 (D8(1)), Mo5Si3 (D8(m)) and Mo5Si3C (D8(8)) have a great potential for ultra-high temperature applications. The present study was undertaken putting greater emphasis on clarifying how their physical and mechanical properties are similar or different in terms of a structure type. Some interesting features are summarized in this paper. The resistivity Of Mo5SiB2, Mo5Si3 and Mo5Si3C single crystals exhibited a negative curvature (d(2)rho(T)/dT(2)<0), with a tendency towards saturation. In the Mo5Si3C with large rho(0) due to impurity carbon atoms, resistivity saturation is pronounced. In contrast, a much higher temperature is required to reach saturation in the Mo5SiB2. The anisotropy ratio of CTE (alpha(c)/alpha(a)) for the Mo5SiB2 is about 1.2-1.6 and is significantly reduced from about 2 of the Mo5Si3 and Mo5Si3C. On the other hand, the Young's modulus of the Mo5SiB2 is more anisotropic than those of the Mo5Si3 and Mo5Si3C. Plastic anisotropy was observed in the Mo5SiB2, because only slip on [001][100] is operative at 1500degreesC. On the contrary, plastic deformation was observed at temperatures above 1300degreesC for the Mo5Si3C and Mo5Si3. Anisotropy of their plastic deformation was much less than that of the Mo5SiB2, presumably because more than two slip systems can be activated. Creep resistance of the Mo5SiB2 is much better than that of the Mo5Si3 as well as the most advanced materials such as MoSi2 and Si3N4 based structural ceramics.
    MATERIALS RESEARCH SOC, 2003, DEFECT PROPERTIES AND RELATED PHENOMENA IN INTERMETALLIC ALLOYS, 753, 339 - 344, English
    International conference proceedings

  • Mechanical and thermal properties of single crystals of ZrB2
    NL Okamoto, M Kusakari, K Tanaka, H Inui, M Yamaguchi, S Otani
    Coefficients of thermal expansion (CTE), elastic constants and plastic deformation behaviors of single crystals of ZrB2, which possesses a hexagonal layered structure where pure Zr and pure B atomic planes stack alternatively along the c-axis, have been investigated in wide temperature ranges. While the observed elastic constants indicate highly anisotropic nature of atomic bonding being consistent with the layered structure, the observed CTE values are rather isotropic. Two operative slip systems, (0001)<11(2) over bar 0 > and on {1(1) over bar 00}<11(2) over bar 3 >, are identified in compression tests. The observed plastic behaviors are discussed in the light of the deduced anisotropy in atomic bonding.
    MATERIALS RESEARCH SOCIETY, 2003, DEFECT PROPERTIES AND RELATED PHENOMENA IN INTERMETALLIC ALLOYS, 753, 83 - 88, English
    International conference proceedings

  • Identification of chirality of enantiomorphic TaSi2 crystallites by convergent-beam electron diffraction
    H Sakamoto, A Fujii, H Inui, K Tanaka, M Yamaguchi, K Ishizuka
    The chirality of domains in enantiomorphic TaSi2 crystallites produced by co-sputtering and subsequent annealing has been determined by convergent-beam electron diffraction (CBED). TaSi2 possesses the hexagonal C40 structure that belongs to either the space groups P6(2)22 (right-handed) and P6(4)22 (left-handed). Two different CBED methods are employed to determine the chirality of each domain, both of which methods involve comparison of an experimental CBED pattern with a computer simulated one. In one method, the appearance of a structure factor invariant line that appears in a specific first-order Laue-zone (FOLZ) disk in a non-symmetric CBED pattern is inspected. In the other method, asymmetry in the intensity of Bijvoet pairs of FOLZ disks in a symmetrical zone-axis CBED pattern is inspected. Both methods successfully identify the chirality of each domain in the TaSi2 crystallites. Effects of zone-axis orientation as well as crystal thickness on the applicability of these two methods for identification of the chirality are briefly discussed.
    TRANS TECH PUBLICATIONS LTD, 2003, THERMEC'2003, PTS 1-5, 426-4, 1783 - 1788, English
    Scientific journal

  • Fe tracer diffusion in L1(0) ordered FePt
    Y Nose, T Ikeda, H Nakajima, K Tanaka, H Numakura
    Tracer diffusion coefficient of Fe-59 in FePt with the tetragonal L1(0) ordered structure has been measured by an ion-beam sputter-sectioning technique in the temperature range from 1173 to 1374 K. Anisotropy in diffusion has been studied using single-variant single-crystal specimens. The diffusion coefficient in the direction perpendicular to [001] axis (in the a-axis direction), D-a, is larger than that in the [001] (c-axis) direction, D-c, as expected from the atomic arrangement of the L1(0) ordered structure. ne ratio of the diffusion coefficients, D-a/D-c, is 1.3_3.6 for Fe42Pt58 and smaller at higher temperatures. The activation energy for the diffusion is 259 +/- 1 kJ/mol for D-a and 309 +/- 18 kJ/mol for D-c, while the pre-exponential factor is (1.63(-0.13)(+0.15)) x 10(-6) m(2)/s and (8.47(-6.88)(+36.5)) X 10(-5) m(2)/s respectively in Fe42Pt58.
    MATERIALS RESEARCH SOCIETY, 2003, DEFECT PROPERTIES AND RELATED PHENOMENA IN INTERMETALLIC ALLOYS, 753, 381 - 386, English
    International conference proceedings

  • Effects of elastic strain energies on a hydride precipitation in LaNi5-based compounds
    K Tanaka, H Inui, M Yamaguchi, M Koiwa
    The elastic energies associated with hydride formation have been calculated using coherent elasticity theory. The energies modify the required condition for hydride nucleation to lower temperatures or higher hydrogen gas pressures. Since the elastic energies are quite large, hydride cannot form in a crystal or on a planer surface without assistance of a lattice defect. Hydride can form with reasonable excess hydrogen gas pressure only at a corner of specimen at which the most part of elastic energy is released.
    MATERIALS RESEARCH SOCIETY, 2003, DEFECT PROPERTIES AND RELATED PHENOMENA IN INTERMETALLIC ALLOYS, 753, 529 - 534, English
    International conference proceedings

  • A Kushida, K Tanaka, H Numakura
    Diffusion in FePt has been studied with emphasis oil the effect of order-disorder transition by interdiffusion experiments below and above the L1(0)-Al transition temperature. The chemical diffusion coefficient in the disordered state obeys the Arrhenius law with the effective activation energy of 3.1 eV (1 eV = 1.6 x 10(-19) J). Anisotropy of diffusion in the ordered state has been examined using monovariant single-crystals of the tetragonal L1(0) structure. The coefficient of diffusion in the a-axis direction is slightly lower than the extrapolation of the diffusivity from the disordered state while that of diffusion in the c-axis direction deviates significantly toward lower values. The apparent activation energy for the diffusion in the two directions is 3.2 and 3.8 eV, respectively.
    JAPAN INST METALS, Jan. 2003, MATERIALS TRANSACTIONS, 44(1) (1), 59 - 62, English
    Scientific journal

  • K Ihara, K Ito, K Tanaka, M Yamaguchi
    Mo5SiB2 is a new refractory metal silicide with great potential for ultra-high temperature structural applications. We succeeded to grow high purity single crystals of Mo5SiB2 using an optical floating zone method. Single-crystal elastic constants at room temperature (RT) of the silicide were measured. Mo5SiB2. has less anisotropic single crystal elastic moduli and a lower shear modulus and a lower Debye temperature than MoSi2. Mo5SiB2, has a slightly higher bulk, shear. Young's moduli and Debye temperature than Mo5Si3, Mo5SiB3, has a RT Vickers hardness of around 18 GPa, which is much larger than those of Mo5Si3 and MoSi2 Fracture toughness around 2 Mparootm is comparable to those of Mo5Si3 and MoSi2. Compression tests were performed at 1500 degreesC. Slip was observed on [001](010) for [021] orientation. However, slip on <100>(001), which has been reported to be activated, was not observed. Mechanical properties of Mo5SiB2 single crystals are discussed in relation to the complex crystal structure of Mo5SiB2. (C) 2002 Elsevier Science B.V. All rights reserved.
    ELSEVIER SCIENCE SA, Jun. 2002, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 329, 222 - 227, English
    Scientific journal

  • T Ichitsubo, H Ogi, M Hirao, K Tanaka, M Osawa, T Yokokawa, T Kobayashi, H Harada
    This paper reports the elastic constants of the Ni-base single crystal superalloy (TMS-26) with a rafted (lamellar) structure having tetragonal symmetry. The elastic constants have been measured at room temperature with the resonance ultrasound spectroscopy method and the mode-selective electromagnetic acoustic resonance method. The value of the elastic constant c(33) (250.4 GPa) is almost equal to that of c(11) (252.5 GPa), which indicates that the rafted structure virtually has the elastic anisotropy of cubic system. (C) 2002 Elsevier Science B.V. All rights reserved.
    ELSEVIER SCIENCE BV, May 2002, ULTRASONICS, 40(1-8) (1-8), 211 - 215, English
    Scientific journal

  • Atomic structures and energetics of LaNi5-H solid solution and hydrides
    K Tatsumi, Tanaka, I, H Inui, K Tanaka, M Yamaguchi, H Adachi
    First-principles calculations on a primary solid solution of LaNi5-H and a hypothetically ordered full hydride. LaNi5H7 have been made employing ultrasoft pseudopotentials and plane-wave basis. Some intermediate hydrides were calculated as well. A full geometry optimization has been made to investigate their heat of formation in detail. Atomic positions of LaNi5H7 have been described in various ways through the Rietveld analyses of neutron-diffraction profile. The lowest energy structure by the present calculation is close to that of the model analyzed with the space group of P6(3)Mc by Lartigue et al. However, we found that the structure model with a single unit cell, i.e., Z=1, cannot be ruled out for LaNi5H7. Regarding the primary solid solution, the 12n site of LaNi5 is most stable among five possible interstices proposed in literature. The stability of the interstices can be explained by the number of near-neighbor Ni atoms, which is substantially different from the widely accepted view that the geometric radius by the rigid sphere model determines the stability. The theoretical heat of solution in the primary solid solution is -33 kJ/mol-H-2, which roughly agrees with the experimental value. On the other hand, the heat of formation of LaNi5H7 is -45 kJ/mol-H-2, which is 30-40% more negative than the experimental value. This discrepancy may be ascribed to the fact that all hydride samples are generally highly defective. The theoretical heat of formation of intermediate phases indicates that the LaNi5-H system dissociates to the primary solid solution and the full hydride. Expansion of the cell volume associated with hydrogenation is well reproduced by the calculation.
    AMER PHYSICAL SOC, Nov. 2001, PHYSICAL REVIEW B, 64(18) (18), 184105, English
    Scientific journal

  • Kazuyoshi Tatsumi, Isao Tanaka, Haruyuki Inui, Katsushi Tanaka, Masaharu Yamaguchi, Hirohiko Adachi
    American Physical Society (APS), Oct. 2001, Physical Review B, 64(18) (18)
    Scientific journal

  • K Tanaka, T Ichitsubo, M Koiwa
    When single crystals of equiatomic FePd in the disordered state are held at temperatures below the ordering temperature (923 K) but above 780 K, their transformation is markedly affected by application of either a compressive stress or a magnetic field. The distribution between orientational variants is affected, as expected, but also the volume fraction transformed and the rate of transformation change, each by as much as an order of magnitude. These effects are explained in terms of a change in nucleation rate brought about by the applied fields, and the associated development of an oriented internal stress field. The lower bound temperature of 780 K is identified with the spinodal ordering temperature for the transformation. A computer simulation based on the Ginzburg-Landau approach clearly supports these explanations. (C) 2001 Elsevier Science B.V. All rights reserved.
    ELSEVIER SCIENCE SA, Aug. 2001, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 312(1-2) (1-2), 118 - 127, English
    Scientific journal

  • Ren, X, N Miura, J Zhang, K Otsuka, K Tanaka, M Koiwa, T Suzuki, YI Chumlyakov
    Single crystal elastic constants of Ti-Ni alloys without (quenched) and with (aged) Ti3Ni4 precipitates were measured systematically by rectangular parallelepiped resonance method as a function of composition and temperature, and compared with Ti-Ni-Cu and Ti-Ni-Fe alloys, in an attempt to answer some long-standing questions as to the origin of the unique monoclinic B19' martensite, and why composition and thermomechanical treatment greatly changes the path of martensitic transformation. The results showed that softening in c(44) in additional to c', is a common feature for all Ti-Ni binary (both quenched or aged) and ternary alloys. This general feature just corresponds to the fact that all these alloys ultimately transform into B19', suggesting that softening in c(44) is responsible for the unique B19' martensite, which found no analogy in other beta phase alloys. We also found an interesting correspondence between the temperature dependence of anisotropy factor and transformation path. Prior to B2-B19' transformation anisotropy shows a decrease with lowering temperature; prior to B2-B19 an anisotropy increase, while prior to B2-R transformation a constant anisotropy. We further showed that three possible martensite candidates (R, B19, B19') are rooted in anomalies in specific phonon modes and elastic softening. We showed that the multi-stage transformations are restricted by a general rule: multi-stage transformation occurs in the sequence of increasing transformation strain. With this rule we can explain all known transformation paths by considering the effect of alloying addition and fine precipitates/dislocation network on relative stability of different martensites. We further predict that there may exist a new transformation path in Ti-Ni-based alloys: B2-R-B19-B19'. (C) 2001 Elsevier Science B.V. All rights reserved.
    ELSEVIER SCIENCE SA, Aug. 2001, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 312(1-2) (1-2), 196 - 206, English
    Scientific journal

  • K Tanaka, K Nawata, H Inui, M Yamaguchi, M Koiwa
    The crystallographic structures of seven binary transition-metal disilicides with the C11(b), C40 and C54 structures have been refined through analysis of single-crystal X-ray diffraction data. These transition-metal (TM) disilicides include those formed with Ti, V, Cr, Nb, Mo, Ta and W. Crystallographic parameters refined are space groups, lattice constants and atomic coordinates. In most of previous studies, silicon atoms have been considered to locate at the ideal positions so that the TM atoms are perfectly six-fold coordinated in TMSi2 layers prevailing in all the three structures. The present analysis shows that the silicon atones are displaced from the ideal positions. The magnitude of such displacement is found to be closely related to the interatomic distance in these pseudo-hexagonally arranged TMSi2 layers. In addition, the space group of three of the four C40 disilicides, VSi2, CrSi2 and TaSi2, is determined to be P6(4)22, which is of chirality with respect to that (P6(2)22) assigned in the previous studies. (C) 2001 Elsevier Science Ltd. All rights reserved.
    ELSEVIER SCI LTD, Jul. 2001, INTERMETALLICS, 9(7) (7), 603 - 607, English
    Scientific journal

  • K Ito, K Ihara, K Tanaka, M Fujikura, M Yamaguchi
    The T-2 phase in the Mo-Si-B system is a refractory molybdenum borosilicide with great potential for ultra-high temperature structural applications. We recently succeeded in growing high purity single crystals of the T-2 phase with a composition of Mo-14Si-26B (at.%) using an optical floating zone method. Electrical resistivity of the T-2 phase is isotropic with respect to the a and c axes and it monotonously increases with temperature from similar to 40 mu Omega cm at room temperature to similar to 80 mu Omega cm at 800 degreesC. The anisotropy ratio of thermal expansion coefficient (alpha (c)/alpha (a)) of the T2 phase is approximately 1.4 at 500 degreesC which is significantly smaller than 2.2 for Mo5Si3. The bulk, shear and Young's moduli and the Debye temperature of the T-2 phase are slightly higher than those of Mo5Si3. Slip on [001]{100} was observed on [021] oriented specimens both compressed and crept at 1500 degreesC. However, slip on < 100 > (001), which has been reported to be operative, was not observed. [001] dislocations are mostly straight and long, and tend to align along their edge orientation. The preference for slip on [001]{100} is interpreted on the basis of the crystal structure. The steady-state creep rate is low under the creep conditions. It is, for example, 3.1x10(-8) s(-1) at 1500 degreesC and 432 MPa. The activation energy and stress exponent for creep was found to be similar to 740 kJ/mol and 6.8, respectively. (C) 2001 Elsevier Science Ltd. All rights reserved.
    ELSEVIER SCI LTD, Jul. 2001, INTERMETALLICS, 9(7) (7), 591 - 602, English
    Scientific journal

  • 組織形成の計算機シミュレーションにおける問題点
    TANAKA KATSUSHI
    社)日本鉄鋼協会, 2001, 相分解による組織形成過程の研究最前線 －理論から実験まで－, 107 - 116, Japanese
    Symposium

  • Thermal fluctuation for the Time-dependent Ginzburg-Landau simulation
    TANAKA KATSUSHI
    2001, Phys. Rev. E, Vol. 63,(No.6, (2001),) (No.6, (2001),), 060101, English
    Scientific journal

  • Shape recovery through order-disorder phase transformation on equiatomic FePd
    K Morioka, K Tanaka
    Shape recovery not associated with martensitic transformation but with order-disorder phase transformation is examined in a model system of FePd. Under a uniaxial compressive stress, a reversible shape change (reduction and elongation in edge length) is observed by cooling and heating the specimen temperature. The elongation of the specimen associated with the disordering occurs at 950 K, and the reduction along the direction of a compressive stress associated with the ordering occurs at 830 K. The temperature hysteresis between ordering and disordering is about 120 K. For single crystals, the change in the edge length is large as about 4% when the compressive stress is applied along the [001] crystallographic direction.
    JAPAN INST METALS, 2001, PRICM 4: FORTH PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING, VOLS I AND II, (2001),, 1703 - 1706, English
    International conference proceedings

  • Refinement of Crystallographic Parameters in Refractory Metal Disilicides
    TANAKA KATSUSHI
    2001, Mat. Res. Soc. Symp. Proc., Vol. 646, N4.3.1 - N4.3.6, English
    International conference proceedings

  • First-principles study of LaNi5-H solid solutions and its hydrides
    K Tatsumi, Tanaka, I, H Inui, K Tanaka, M Yamaguchi, H Adachi
    Results of a theoretical study cif the atomic arrangements of LaNi5-H solid solutions and hydrides using a first-principles pseudopotential method is given. The lowest energy structure of LaNi5Hx (x=6-7), i.e., full-hydrides by the present calculation is close to that of the model analyzed with the space group of P6(3)mc by Lartigue et al on the basis of neutron diffraction experiments. For the atomic arrangements of the primary solid solution, the 12n site of the LaNi5 is found to be most stable among five possible interstitial sites proposed in literature. Atomic arrangements after the geometry optimization have been analyzed. The relative stability of the hydrogen sites shows no clear correlation with the initial hole radii, contrary to the widely accepted view. Instead of that, the number and length of the Ni-H bonds seem to be dominating the stability. Heats of formation and solution are then discussed by comparison with experimental values.
    JAPAN INST METALS, 2001, PRICM 4: FORTH PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING, VOLS I AND II, 445 - 448, English
    International conference proceedings

  • Elastic properties of LaNi5-based compounds
    K Tanaka, S Okazaki, Y Watayo, H Inui, M Yamaguchi, M Koiwa
    Single crystal elastic constants of binary LaNi5 and ternary La(Ni0.8Co0.2)(5) and La(Ni0.9Al0.1)(5) at room temperature have been determined by the rectangular parallelepiped resonance method. The ternary elements of Co and Al decrease most of the elastic constants, and increase the ratio of the bulk modulus to the shear modulus, B/G. The increment of the B/G ratio suggests a trend of improved ductility of these ternary LaNi5. The change in single crystal elastic constants with the ternary additions are explained quantitatively by the increase of the lattice constants with the substitutions. The constants were utilized for calculating elastic energies associated with coherent precipitation of hydride in the LaNi5 matrix. The elastic energy decreases by the substitutions but the decrement is not large. The calculation indicates that hydride hardly precipitates in the matrix without assistance of lattice defects; since hydride has to overcome extremely large elastic energy to precipitate.
    JAPAN INST METALS, 2001, PRICM 4: FORTH PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING, VOLS I AND II, 441 - 444, English
    International conference proceedings

  • H Inui, T Hashimoto, K Tanaka, Tanaka, I, T Mizoguchi, H Adachi, M Yamaguchi
    Phase transformation and defect structures in thin-film TiSi2 produced by co-sputtering have been investigated as a function of annealing temperature by transmission electron microscopy. Metastable C49 crystallites nucleate first in the amorphous matrix from as low as 100 degreesC. This is due to the lower surface energy of C49 crystallites arising from the similarity in electronic structure, chemical bonding and atomic density between the C49 and amorphous modifications. All C49 crystallites contain numerous (010) faults, which are boundaries between two differently oriented domains related to each other by a 90 degrees rotation about [010]. Stable C54 crystallites nucleate in the C49 matrix above 700 degreesC and most C54 crystallites contain twins with the twin habit plane parallel to (001), which is perpendicular to the (110) twinning plane. Ternary additions to TiSi2 thin films to reduce the C49-->C54 transformation temperature are discussed on the basis of the results from electron energy-loss spectroscopy (EELS) analyses described in the companion paper. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.
    PERGAMON-ELSEVIER SCIENCE LTD, Jan. 2001, ACTA MATERIALIA, 49(1) (1), 83 - 92, English
    Scientific journal

  • Cubic-tetragonal transformation under external stress by the time-dependent Ginzburg-Landau simulations
    T Ichitsubo, K Tanaka
    We have studied the effects of an external uniaxial stress on the cubic-tetragonal transformation through the computer simulations on the time-dependent Ginzburg-Landau (TDGL) approach. We have taken up the fcc-L1(0), ordering; the Landau free-energy function has been determined so as to reproduce the free energy obtained from the Monte Carlo calculations. The stress effects have been investigated for two types of the ordering processes: (i) nucleation process (at temperatures higher than the instability temperature T-0) and (ii) spinodal ordering process (at temperatures below T-0). When we have chosen properly the magnitude of the thermal fluctuation, the simulations have reproduced well our experimental trend that a single variant structure is formed when the ordering occurs via nucleation mode. The term of the thermal fluctuation is indispensable for obtaining the simulation results consistent with the actual phenomena.
    JAPAN INST METALS, 2001, PRICM 4: FORTH PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING, VOLS I AND II, 2431 - 2434, English
    International conference proceedings

  • Crystal structure and some physical properties of defect disilicide formed with Re
    K Kuwabara, H Hoshikawa, K Tanaka, H Inui, M Yamaguchi
    The crystal structure of the disilicide formed with Re has been refined by electron diffraction. Re disilicide does not reside at the composition of ReSi2 but has a stoichiometry formulated to be ReSi1.75. The crystal structure is monoclinic with the space group C2/m (mc44) due to an ordered arrangement of vacancies on Si sites in the underlying (parent) Cl I-h lattice. The crystal contains four differently oriented domains; two domains related with each other by the 90degrees-rotation about the c-axis of the underlying C11(b) lattice and twin domains for each of the two domains. The twin habit plane is (001) of the underlying C11(b) lattice and the thickness of twins is surprisingly very thin ranging from 100-300 nm. This microstructural feature plays a decisive role in electrical transport and optical properties, leading to highly anisotropic properties in terms of crystal orientation. The results from measurements of electrical resistivity and optical properties indicates ReSi1.75 is a semiconductor with a direct band gap of 0.23-0.33 eV and an indirect gap of 0.11-0.20 eV.
    JAPAN INST METALS, 2001, PRICM 4: FORTH PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING, VOLS I AND II, 967 - 970, English
    International conference proceedings

  • T Ichitsubo, K Tanaka, M Koiwa, Y Yamazaki
    Computer simulations based on the time-dependent Ginzbug-Landau approach have been performed for the formation of domain structure in the cubic-tetragonal transformation under an external field. The fcc-L1(0) ordering has been studied as a model case of the transformation, and the Landau free-energy function has been determined so as to reproduce the free energy calculated by the Monte Carlo simulation. The simulations have demonstrated the features observed in our experiments on FePd alloy under an external stress, and have clarified the formation mechanism of a single variant structure. The internal stress field developed by the preferential formation of a variant favored by the external stress further accelerates the trend cooperatively, and eventually leads to a single variant structure.
    AMER PHYSICAL SOC, Sep. 2000, PHYSICAL REVIEW B, 62(9) (9), 5435 - 5441, English
    Scientific journal

  • K Tanaka, T Ichitsubo, M Amano, M Koiwa, K Watanabe
    Effect of a magnetic field on ordering of FePd was examined. Single crystals of disordered FePd were heat treated at various temperatures under the magnetic field up to 10 T. When the temperature is higher than 793 K, a mono-variant structure of the L1(0) ordered phase is formed under the magnetic field of appropriate strength. The necessary conditions far the formation of the mono-variant structure are: the ordering proceeds by nucleation and growth process (the temperature of heat treatment must be higher than the spinodal ordering temperature), and magnetocrystalline anisotropy energy is sufficiently large to change the nucleation rates of different variants.
    JAPAN INST METALS, Aug. 2000, MATERIALS TRANSACTIONS JIM, 41(8) (8), 917 - 922, English
    Scientific journal

  • K Tanaka, S Okazaki, T Ichitsubo, T Yamamoto, H Inui, M Yamaguchi, M Koiwa
    The elastic energy associated with coherent precipitation of hydrides with various shapes in LaNi5 has been calculated by the Eshelby method with the single-crystal elastic constants experimentally determined by a rectangular parallelepiped resonance method. The calculated elastic energy amounts to about 70% of the change in chemical energy that occurs upon hydride formation. This implies the difficulty for coherent hydrides to nucleate in the perfect lattice of LaNi5. This is in contrast to the case of titanium or zirconium, in which the associated elastic energies are only about 15% of the chemical energy change. Hydride precipitation in LaNi5 is thus suggested to occur preferentially at free surfaces and lattice defects such as dislocations and grain boundaries. (C) 2000 Elsevier Science Ltd. All rights reserved.
    ELSEVIER SCI LTD, May 2000, INTERMETALLICS, 8(5-6) (5-6), 613 - 618, English
    Scientific journal

  • Effect of Magnetic field on Ordering of FePd
    TANAKA KATSUSHI
    2000, Trans. MRS-J, Vol. 25,(No. 2) (No. 2), 497 - 500, English
    Scientific journal

  • Understanding the martensitic transformations in TiNi-based alloys by elastic constants measurement
    Ren, X, N Miura, K Taniwaki, K Otsuka, T Suzuki, K Tanaka, YI Chumlyakov, M Asai
    The origin of the unique monoclinic martensite B19' in TiNi and TiNi-based alloys has remained obscure for many years. The formation of B19' martensite also challenged the well-known basal-plane shear/shuffle theory of martensitic transformation in beta phase alloys. Recently we proposed that the B2-B19' transformation stems from a strong coupling between a non-basal-plane shear (c(44) shear) with the basal-plane shear (c' shear), being manifested by a low-lying and decreasing anisotropy factor (c(44)/c') towards M-s. This model has gained experimental support from elastic constants measurement on Ti50Ni30Cu20 alloy which exhibits B2-B19 transformation (i.e. absence of the monoclinic shear). In the present study, we attempt to further verify this model by measuring the elastic constants of Ti50Ni40Cu10 alloy which undergoes a two-stage transformation B2-B19-B19'. The results clearly demonstrated once again that whenever the parent phase B2 does not transform directly into B19', the anisotropy factor exhibits an increase towards M-s, indicating that the c(44) shear is not included into the transformation. Therefore, the present study gives additional support to the coupling model of TiNi-based alloys. Furthermore, we tried to understand the multi-stage transformation in terms of coupling strength between the c' shear and c(44) shear. (C) 1999 Elsevier Science S.A. All rights reserved.
    ELSEVIER SCIENCE SA, Dec. 1999, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 273, 190 - 194, English
    Scientific journal

  • T Ichitsubo, K Tanaka, H Numakura, M Koiwa
    A procedure for calculating the configurational free energy with the Monte Carlo simulation is presented, accounting for the case of the application of external fields. First, the free energy for the L1(0) ordering systems without any external fields has been evaluated for the various values of the second nearest-neighbor effective interaction, and the feature of this method has been discussed from the viewpoint of the pair correlation. Next, this method has been applied to the case of application of external fields, demonstrating the calculation of the free energy under an external stress held For the L1(0) phase that has a tetragonal distortion dependent on the long-range order parameter. [S0163-1829(99)06037-3].
    AMER PHYSICAL SOC, Oct. 1999, PHYSICAL REVIEW B, 60(13) (13), 9198 - 9201, English
    Scientific journal

  • Elastic properties of high-temperature intermetallics
    K Tanaka, M Koiwa
    Recent developments in the technology of crystal growth and the method for measuring elastic constants allows data to be accumulated on the elastic properties of high temperature intermetallics. This paper reviews the elastic properties of technically important intermetallics: nickel-based L1(2) compounds, titanium aluminides and transition metal disilicides.
    WALTER DE GRUYTER GMBH, Jul. 1999, HIGH TEMPERATURE MATERIALS AND PROCESSES, 18(5-6) (5-6), 323 - 336, English
    Scientific journal

  • J Zhang, Ren, X, K Otsuka, K Tanaka, YI Chumlyakov, M Asai
    Elastic constants of a Ti-48 at%Ni-2 at%Fe single crystal prior to B2-->R transformation was measured by using the rectangular parallelepiped resonance (RPR) method. Both shear modulus c' and c(44) were found to soften with decreasing temperature towards the transformation temperature R-s. it was also found that in the vicinity of the transformation temperature, the anisotropy factor A of this alloy shows little temperature dependence, which is in contrast to the decrease for as-quenched binary Ti-50 at%Ni alloy (B2--> B19'), and the increase for Ti-30 at%Ni-20 at%Cu alloy (B2-->B19), respectively reported. Therefore, this phenomenon appears to be closely related to B2-->R transformation.
    JAPAN INST METALS, May 1999, MATERIALS TRANSACTIONS JIM, 40(5) (5), 385 - 388, English
    Scientific journal

  • Directional atomic bonds in MoSi2 and other transition-metal disilicides with the C11(b), C40 and C54 structures
    K Tanaka, H Inui, M Yamaguchi, M Koiwa
    The elastic constants of MoSi2l as well as other transition-metal (TM) disilicides with the C11(b), C40 and C54 structures are analysed by adopting an approach similar to the valence-force-field approach in order to elucidate the directional nature of atomic bonding. In the present approach, all interatomic forces are resolved into bond-stretching and bond-bending forces and the elastic properties are described with force constants corresponding to these two forces. The values of force constants are compared with each other. The directionality in atomic bonding in C11(b) disilicides is found to be stronger than any other disilicides with the C40 and C54 structures. Of the two C11(b) disilicides, the directionality in atomic bonding is stronger for WSi2 than for MoSi2. (C) 1999 Published by Elsevier Science S.A. All rights reserved.
    ELSEVIER SCIENCE SA, Mar. 1999, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 261(1-2) (1-2), 158 - 164, English
    Scientific journal

  • Nishitani, SR, S Fujii, M Mizuno, K Tanaka, Tanaka, I, H Adachi
    Using the formula including charge transfers on sites, the binding energy call be described by the sum of the short-range energy, the on-site charge transfer energy and the long-range electrostatic energy. For discussing the 'ionic' contributions on the binding energy, Madelung energies are calculated for the complex compounds of 3d transition metal (M) and metalloid (B,Si) of MB2, MSi2 and MSi and are compared to the heat of formation. (C) 1999 Elsevier Science B.V. All rights reserved.
    ELSEVIER SCIENCE BV, Feb. 1999, COMPUTATIONAL MATERIALS SCIENCE, 14(1-4) (1-4), 62 - 66, English
    Scientific journal

  • Formation of preferentially oriented structure of ordered FePd under external stress
    T Ichitsubo, K Tanaka, M Nakamoto, M Koiwa
    The microstructure of the equiatomic FePd alloy is modified substantially by applying a compressive stress during ordering; only one of three variants is preferentially formed to result in a single domain crystal. Such an effect of the applied stress is discussed in the framework of the classical nucleation theory. The nucleation rate of the favorably oriented domain is shown to be drastically enhanced by the external stress while that of unfavorable ones is decreased.
    JAPAN INST METALS, 1999, JAPAN INSTITUTE OF METALS, PROCEEDINGS, VOL 12, (JIMIC-3), PTS 1 AND 2, 389 - 392, English
    International conference proceedings

  • Elastic softening of Ti49.2Ni50.8 single crystal prior to B2-B19' martensitic transformation
    N Miura, J Zhang, Ren, X, K Otsuka, T Suzuki, K Tanaka, YI Chumlyakov, M Asai
    Recently we have proposed that the unique B2-B19' martensitic transformation, which involves a non-basal-plane shear, is due to the strong coupling between {110}1(1) over bar 0(B2) shear and (001)1(1) over bar 0(B2) shear, as manifested by a lowering in anisotropy factor prior to martensitic transformation (MT). Although the scarce existing elastic constant data of TiNi alloys (due to the great difficulty in growing single crystals) seem to support this view, further study is necessary for a reliable verification. In this study we prepared a single crystal of Ti492Ni508 alloy by a modified Bridgman method, and measured its elastic constants prior to B2-B19' MT by the rectangular parallelepiped resonance (RPR) method. We found that both c' and c(44) soften with approaching Ms temperature. In particular, anisotropy factor exhibits a decrease with decreasing temperature. These results strongly support the above view on the origin of B2-B19'MT.
    JAPAN INST METALS, 1999, JAPAN INSTITUTE OF METALS, PROCEEDINGS, VOL 12, (JIMIC-3), PTS 1 AND 2, 827 - 830, English
    International conference proceedings

  • Ren, X, K Taniwaki, K Otsuka, T Suzuki, K Tanaka, YI Chumlyakov, T Ueki
    Elastic constants of Ti50Ni30Cu20 alloy prior to the martensitic transformation B2 --> B19 was measured for the first time by using the rectangular parallelepiped resonance method. The softening in both shear modulus c' and c(44) was found with approaching transformation temperature. As a result of soft c(44), the anisotropy factor shows a low value of 2.8 in the vicinity of the transformation temperature. c(11), c(12), and bulk modulus were found to show little temperature dependence in the vicinity of the transformation temperature. Compared with the binary Ti50Ni50 alloy, Ti50Ni30Cu20 alloy exhibits a 40% higher and increasing anisotropy with approaching transformation temperature. Based on the experimental results, we explained why Ti50Ni30Cu20 transforms into B19 martensite, while Ti50Ni50 transforms into a strange monoclinic B19' martensite.
    TAYLOR & FRANCIS LTD, Jan. 1999, PHILOSOPHICAL MAGAZINE A-PHYSICS OF CONDENSED MATTER STRUCTURE DEFECTS AND MECHANICAL PROPERTIES, 79(1) (1), 31 - 41, English
    Scientific journal

  • Elastic constants and electron distribution in transition metal disilicides
    TANAKA KATSUSHI
    1999, Proc. of the U.S.-Japan, 67 - 70, English
    International conference proceedings

  • Effect of applied stress on ordering of FePd
    T Ichitsubo, K Tanaka, M Nakamoto, T Miyoshi, M Koiwa
    The effect of applied stress has been studied for the ordering of the equiatomic FePd alloys. One of the three variants is formed preferentially when a single crystal specimen is subjected to compressive stresses during ordering, resulting in the single domain L1(0) crystal. The effect of the stress seems to affect the nucleation process rather than the growth process.
    JAPAN INST METALS, 1999, JAPAN INSTITUTE OF METALS, PROCEEDINGS, VOL 12, (JIMIC-3), PTS 1 AND 2, 385 - 388, English
    International conference proceedings

  • K Tanaka, K Nawata, H Inui, M Yamaguchi, M Koiwa
    The temperature dependence of single-crystal elastic constants of Mo(Si,Al)(2) with the hexagonal C40 structure has been measured by the rectangular parallelepiped resonance method over the temperature range from room temperature to 1373 K. The silicide has the largest value of Poisson's ratio among transition-metal silicides with the C40 structure. This is interpreted in terms of the reduced directionality in atomic bonding due to the partial substitution of Al for Si atoms. The expression of the elastic constants on the basis of simple interatomic interactions cannot reproduce the elastic anisotropy of crystal with the C40 structure. The disagreement is considered to be a consequence of the occurrence of internal displacements during elastic deformation in crystals with the non-centrosymmetry. (C) 1998 Elsevier Science Limited. All rights reserved.
    ELSEVIER SCI LTD, Nov. 1998, INTERMETALLICS, 6(7-8) (7-8), 607 - 611, English
    Scientific journal

  • β-CuZnの弾性的性質
    TANAKA KATSUSHI
    日本伸銅協会, 1998, 伸銅技術研究会誌, Vol.37(37) (37), 102 - 105, Japanese
    Scientific journal

  • T Ichitsubo, M Nakamoto, K Tanaka, M Koiwa
    The equiatomic Fe-Pd alloy has an order-disorder transformation at about 650 degrees C. Three types of variants of the L1(0) ordered phase are formed with the c-axis parallel to either of the [100] directions of the disordered fee matrix. Since the ordered phase is tetragonal with c/a=0.966, the external stress is expected to modify the relative population of variants. This has been examined for a single crystal specimen by applying a compressive stress of 40 MPa during ordering treatment. Two types of ordering treatments were examined: (1) quenched from 800 degrees C followed by under-stress-aging at 400 degrees C for 1 h, and (2) slow cooling from a high temperature across the transition temperature (650 degrees C) down to 600 degrees C followed by furnace cooling to room temperature with the stress kept applied. X-ray diffraction measurement revealed that the specimen contains only one type of variant after treatment (2). The effect of the external stress is discussed quantitatively in the light of the calculation based on the continuum elasticity theory.
    JAPAN INST METALS, Jan. 1998, MATERIALS TRANSACTIONS JIM, 39(1) (1), 24 - 30, English
    Scientific journal

  • Effect of external fields on ordering of equiatomic FePd
    TANAKA KATSUSHI
    1998, Proc. of The Third Pacific Rim International Conference on Advanced Materials and Processing (PRICM-3), 1369 - 1374, English
    International conference proceedings

  • Diffusion of constituent elements in Ni3Ge studied by tracer and interdiffusion experiments
    TANAKA KATSUSHI
    1998, Proc. of The Third Pacific Rim International Conference on Advanced Materials and Processing (PRICM-3), 1257 - 1262, English
    International conference proceedings

  • Single-crystal elastic constants of MoSi2 with the C11(b) structure
    K Tanaka, H Onome, H Inui, M Yamaguchi, M Koiwa
    Single-crystal elastic constants of MoSi2 have been measured by the rectangular parallelepiped resonance (RPR) method over the temperature range 4-1373 K. The values at room temperature agree with those reported by Nakamura et al. [1], and the values extrapolated to 0 K are in good agreement with theoretical calculates by Alouani et al. [2]. Values of c(ij) except for c(12) and c(13) decrease with increasing temperature while those of c(12) and c(13) are virtually temperature independent. Elastic property of the compound is discussed in terms of the strength of atomic bonds by adopting the approach introduced by Musgrave and Pople [3]. The elastic constants are expressed with three parameters corresponding to first-nearest-neighbor central, first-nearest-neighbor non-central and second-nearest-neighbor non-central interactions. The extent of contribution of the directional nature in atomic bonding to the elastic properties of MoSi2 is discussed in the light of the temperature variation of the three parameters we introduced. (C) 1997 Elsevier Science S.A.
    ELSEVIER SCIENCE SA, Dec. 1997, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 240, 188 - 194, English
    Scientific journal

  • Self-diffusion in L1(2)-type intermetallic compounds Ni3Ge and Ni3Ga
    K Nonaka, T Arayashiki, H Nakajima, A Almazouzi, K Tanaka, T Ikeda, H Numakura, M Koiwa
    Self-diffusion coefficients of constituent elements in Lk-type intermetallic compound Ni3Ge and Ni3Ga have been measured with the radioactive isotope tracer of Ni-63, Ge-68 and Ga-67 using an ion-beam sputter-sectioning technique. Temperature dependence of the diffusivities is, respectively, expressed as in Ni3Ge compound, D-Ni = 2.5 x 10(-4) exp(-258 +/- 2 kJmol(-1)/RT) m(2)s(-1), D-Ge = 3.5 x 10(-3) exp(-333 +/- 11 kJmol(-1)/RT) m(2)s(-1), and in Ni3Ga compound, D-Ni = 1.7 x 10(-4) exp(-259 +/- 12 kJmol(-1)/RT) m(2)s(-1), D-Ga = 5.3 x 10(-6) exp(-233 +/- 17 kJmol(-1)/RT) m(2)s(-1). The Ni diffusivity is 127 to 392 times higher than the Ge diffusivity in the temperature range from 1048 to 1206K. This trend is consistent with the expectation based on the geometrical arrangement of Ni and Ge in Ni3Ge. However, the Ni diffusivity is only 1.2 to 2.3 times larger than the Ga diffusivity in the temperature range from 963 to 1177K in Ni3Ga. It is suggested that some Ga atoms are located in both sublattices, and diffuse through jumps between right-site and wrong-site in both sublattices.
    TRANS TECH-SCITEC PUBLICATIONS LTD, 1997, DEFECT AND DIFFUSION FORUM, 143, 269 - 274, English
    Scientific journal

  • K Tanaka, Y Mitarai, M Koiwa
    The elastic constants of several Al-based icosahedral alloys were measured over a temperature range from 4 K to 1073 s by the rectangular parallelepiped resonance method. The values of the bulk moduli of these quasicrystals are similar to those of conventional cubic crystals having similar melting temperatures, while the values of Young's and shear moduli are larger in comparison with conventional aluminium alloys. The latter feature is considered to be due to the strong directional bonding in the quasicrystals.
    TAYLOR & FRANCIS LTD, Jun. 1996, PHILOSOPHICAL MAGAZINE A-PHYSICS OF CONDENSED MATTER STRUCTURE DEFECTS AND MECHANICAL PROPERTIES, 73(6) (6), 1715 - 1723, English
    Scientific journal

  • K Tanaka, K Okamoto, H Inui, Y Minonishi, M Yamaguchi, M Koiwa
    Single-crystal elastic contents of Ti3Al have been measured from 3.3 to 290K by a rectangular parallelepiped resonance method. The elastic anisotropy of Ti3Al is similar to, but slightly larger than, that of pure Ti. The values of the measured elastic constants are compared with those calculated for pure Ti stressed to such an extent that it has the same lattice constants as Ti3Al. The difference is interpreted as indicating the existence of directional bonding in the compound.
    TAYLOR & FRANCIS LTD, May 1996, PHILOSOPHICAL MAGAZINE A-PHYSICS OF CONDENSED MATTER STRUCTURE DEFECTS AND MECHANICAL PROPERTIES, 73(5) (5), 1475 - 1488, English
    Scientific journal

  • K Tanaka, T Ichitsubo, H Inui, M Yamaguchi, M Koiwa
    The elastic constants of single-crystal gamma-TiAl (Ti-56O at.% Al) have been measured from 4 to 298 K. The values at 298 K agree with those recently reported by He, Schwarz, Migliori and Whang. c(12) and c(13) are virtually temperature independent while the other elastic constants normally decrease with increasing temperature. The values extrapolated to OK are c(11) = 187GPa, c(33) = 182GPa, c(12) = 74.8 GPa, c(13) = 74.8 GPa, c(44) = 109 GPa and c(66) = 81.2 GPa. The elastic anisotropy factors A(1) = 2c(66)/(c(11)-c(12)), A(2) = 4c(44)/(c(11) + c(33)-2c(13)) and c(44)/c(66) at OK are virtually equal to those at room temperature.
    TAYLOR & FRANCIS LTD, Feb. 1996, PHILOSOPHICAL MAGAZINE LETTERS, 73(2) (2), 71 - 78, English
    Scientific journal

  • 銅合金の弾性的性質
    TANAKA KATSUSHI
    日本伸銅協会, 1996, 伸銅技術研究会誌, Vol.35(35) (35), 183 - 189, Japanese
    Scientific journal

  • K Tanaka, M Koiwa
    The elastic constants of single crystals of several intermetallic compounds have been measured in our laboratory by the rectangular parallelepiped resonance method. This paper first describes the experimental procedure and the method of data analysis of the resonance spectrum to derive values of the elastic constants, and then gives the numerical results for materials measured so far: Ni-base Ll(2) compounds Ni(3)X (X = Mn, Fe, Al, Ga, Ge and Si), TiAl, Ti3Al, CoTi, Co3Ti and CoSi2. The elastic constants of various intermetallic compounds reported by other investigators are also given in tabulated form. Copyright (C) 1996 Elsevier Science Ltd
    ELSEVIER SCI LTD, 1996, INTERMETALLICS, 4(Suppl 1) (Suppl 1), S29 - S39, English
    Scientific journal

  • Measurements of Elastic Constants of Hexagonal Crystals by the Rectangular Parallelepiped Resonance Method
    TANAKA KATSUSHI
    The Korean Inst. of Metals and Materials, 1995, Proc. of The Second Pacific Rim International Conference on Advanced Materials and Processing (PRICM-2), 1153 - 1158, English
    International conference proceedings

  • M KOIWA, K TANAKA, H YASUDA
    The three elastic stiffness constants of various Ni-base intermetallic compounds Ni(3)X with L1(2) structure have been determined by the rectangular parallelepiped resonance method. Two types of specimen chamber were constructed for low temperature (down to 90 K) and for high temperature (up to 1200 K) measurements. In order to reduce the amount of numerical calculation needed to derive the values of elastic constants from the resonance spectrum, we have developed a systematic and efficient method of analysis, which is valid for crystals of cubic symmetry.
    ELSEVIER SCIENCE SA, Sep. 1994, JOURNAL OF ALLOYS AND COMPOUNDS, 211, 585 - 588, English
    Scientific journal

  • DETERMINATION OF ELASTIC-CONSTANTS BY THE RECTANGULAR PARALLELEPIPED RESONANCE METHOD
    K TANAKA, H YASUDA, H NUMAKURA, M KOIWA
    MINERALS, METALS & MATERIALS SOC, 1993, FIRST PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING ( PRICM-1 ), 491 - 494, English
    International conference proceedings

  • 直方体共振法による弾性率の測定
    TANAKA KATSUSHI
    日本学術振興会, 1993, 材料の微細組織と機能性第133委員会, 第138回研究会資料, 1 - 5, Japanese
    Symposium

  • Temperature dependence of elastic constants of several intermetallic compounds
    TANAKA KATSUSHI
    1993, Proc. of 3rd. Japan International SAMPE Symposium, 1171 - 1175, English
    International conference proceedings

  • Diffusion via Six-Jump Vacancy Cycles in the L12 Lattice
    TANAKA KATSUSHI
    1993, Defect and Diffusion Forum, Vols. 95-98, 855 - 858, English
    Scientific journal

  • K TANAKA, K HIRAGA, R OSHIMA
    In order to study the origin of tetragonality of bct martensite of substitutional type disordered Fe-Pd alloys, the change in the axial ratios and internal structures of the martensites with the systematic substitution of Pd for some of Ni in a typical bcc martensite of Fe-Ni alloys has been examined using optical and electron microscopy. It is found that the bct martensite is transformed from the fcc austenite not only via the fct martensite but also directly. The bct martensite is always accompanied by {112} internal twins in which the mottled contrast is observed. It is concluded that the tetragonality of the martensite is caused by the inhomogeneous arrangements of Pd atoms of the austenite.
    JAPAN INST METALS, Mar. 1992, MATERIALS TRANSACTIONS JIM, 33(3) (3), 215 - 219, English
    Scientific journal

  • K TANAKA, R OSHIMA
    A variant structure of bct martensite in Fe-Pd alloys was examined by transmission electron microscopy. The martensite variants constructing a colony which were transformed in a single crystal of austenite consisted of four kinds of variants belonging to a same "plane-group". On the other hand, the variants which were transformed from recrystallized austenite with annealing twins were composed two kinds of them belonging to a same plane group and two of their mirror symmetrical ones about the annealing twin plane. The variants formed at the annealing twins had a common [011]b direction which was nearly normal to a (111)f austenite annealing twin plane. Shape deformation matrices of the variants and the coherency at the interfaces of neighboring variants were calculated by Wechsler, Lieberman and Read's phenomenological theory. The results indicated that control factors of the selection of variants of the colony were not only a magnitude of total shape deformation but also the coherency at variant interfaces. Annealing twins play a role of the nucleation sites of new martensite plates and reduces the number of kinds of variants from 24 to 6 by the formation of variant interfaces at the twin plane.
    JAPAN INST METALS, Apr. 1991, MATERIALS TRANSACTIONS JIM, 32(4) (4), 325 - 330, English
    Scientific journal

  • Study of bct Martensite of Fe-Pd Alloys
    TANAKA KATSUSHI
    1990, Mater. Sci. Forum, Vols. 56-58, 175 - 180, English
    Scientific journal

■ MISC
  • 田中克志
    Lead, Japan Institute of Metals, 01 Aug. 2020, Materia Japan, 59(8) (8), 435 - 437
    [Invited]
    Introduction scientific journal

  • CrMnFeCoNi 高エントロピー合金の単結晶弾性率
    田中克志
    Lead, Mar. 2018, 日本機械学会誌, 121(1192) (1192), 16 - 19
    [Invited]
    Introduction scientific journal

  • CrMnFeCoNi系等原子量高エントロピー合金における局所格子歪と固溶強化量の相関
    岡本範彦, 弓削是貴, 田中克志, 乾晴行, GEORGE Easo P.
    2016, 日本金属学会講演概要(CD-ROM), 158th

  • CrMnFeCoNi高エントロピー合金の力学特性
    河村麻莉乃, 神原佑季, 田中克志, 岡本範彦, 岡本範彦, 乾晴行, 乾晴行
    2016, 日本金属学会講演概要(CD-ROM), 158th

  • FCC系高エントロピー合金の局所格子歪み測定と単結晶マイクロピラー圧縮
    岡本範彦, 藤本周, 陳正昊, 松野下裕貴, 弓削是貴, 田中克志, 乾晴行
    2015, 日本金属学会講演概要(CD-ROM), 156th

  • Fe-Zn系金属間化合物δ1p相の単結晶X線構造解析-ζ相構造との類似性-
    岡本範彦, 岡本範彦, 田中克志, 乾晴行, 乾晴行
    2013, 日本金属学会講演概要(CD-ROM), 153rd

  • Fe-Zn系金属間化合物δ1p相の結晶構造解析
    岡本範彦, 岡本範彦, 田中克志, 乾晴行, 乾晴行
    2013, 日本金属学会講演概要(CD-ROM), 152nd

  • チムニーラダーシリサイドにおけるPBET界面構造と熱電特性
    岡本範彦, 足立大樹, 岸田恭輔, 田中克志, 乾晴行
    2012, 応用物理学関係連合講演会講演予稿集(CD-ROM), 59th

  • CrB2における巨視的弾性率と微視的弾性率の違い
    田中克志, 岡本範彦, 乾晴行, 筒井智嗣, BARON Alfred Q.R., BARON Alfred Q.R.
    2012, 日本金属学会講演概要(CD-ROM), 151st

  • 低温で負の降伏応力の温度依存性を示すL12型金属間化合物の転位の分解様式
    長谷川喜彦, 長谷川喜彦, 田中克志, 岡本範彦, 乾晴行
    2012, 日本金属学会講演概要(CD-ROM), 150th

  • OS02-4-1 Elastic softening in CrB_2 at the magnetic transition temperature
    Tanaka Katsushi, Nagano Shinji, Okamoto Norihiko L., Inui Haruyuki
    The Japan Society of Mechanical Engineers, 19 Sep. 2011, Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics, 2011(10) (10), "OS02 - 4-1-1", English

  • N.L. Okamoto, H. Adachi, K. Kishida, K. Tanaka, H. Inui
    The Japan Institute of Metals and Materials, 01 Apr. 2011, Materia Japan, 50(4) (4), 149 - 151, Japanese
    [Refereed]
    Introduction scientific journal

  • Okamoto Norihiko, Adachi Hiroki, Kishida Kyosuke, Tanaka Katsushi, Inui Haruyuki
    Apr. 2011, Materia Japan, 50(4) (4), 149 - 151, Japanese
    [Refereed]
    Introduction scientific journal

  • チムニーラダーシリサイドのVECと異相界面制御による熱電特性向上
    岡本範彦, 足立大樹, 岸田恭輔, 田中克志, 乾晴行
    2011, 応用物理学関係連合講演会講演予稿集(CD-ROM), 58th

  • L12型Pt3Al単結晶の弾性定数と力学特性
    岡本範彦, 長谷川喜彦, 橋本和太郎, 田中克志, 乾晴行
    2011, 日本金属学会講演概要, 148th

  • 空孔規則配列相を有するReSi1.75の異方的な熱電特性
    原田俊太, 田中克志, 岡本範彦, 乾晴行
    2011, 日本金属学会講演概要, 148th

  • Fe-Zn-Al系Γ1相単結晶の力学特性
    岡本範彦, 田中克志, 乾晴行, 山口周
    2011, 日本金属学会講演概要(CD-ROM), 149th

  • S. Harada, K. Tanaka, H. Inui
    Thermoelectric properties of a homologous series of Magnéli phase titanium oxides TinO2n-1 (n = 2, 3..) have been investigated. Dense polycrystalline specimens with nominal composition of TiO2-x (x = 0.10, 0.20) have been prepared by conventional hot-pressing. X-ray diffraction analysis has revealed that prepared specimens are slightly reduced during hot-pressing. Electrical conduction is of n-type for all prepared titanium oxides and electrical resistivity and absolute values of Seebeck coefficient decrease with increasing oxygen deficiency. The carrier concentration of Magnéli phase titanium oxide increases with increasing oxygen deficiency. Lattice thermal conductivity decreases with increasing oxygen deficiency by more than 60% at room temperature and 40% at 773K compared to TiO2, which can be due to the presence of dense planar defects. The largest thermoelectric figure of merit Z, 1.6 × 10-4 K -1 at 773K, was obtained in TiO1.90 hot pressed specimen. © 2010 Materials Research Society.
    07 Sep. 2010, Material Research Society Symposium Proceedings, 1218, 1 - 6, English
    Report research institution

  • L12型金属間化合物Co3(Al,W)の塑性変形
    岡本 範彦, 岸田 恭輔, 田中 克志, 乾 晴行
    08 Mar. 2010, 日本学術振興会 耐熱金属材料123委員会研究報告, 51(1) (1), 101 - 106, Japanese
    Report scientific journal

  • L12型Co3(Al,W)合金の塑性変形機構
    岡本範彦, 足立大樹, 岸田恭輔, 田中克志, 乾晴行
    2010, 日本金属学会講演概要, 146th

  • チムニーラダーシリサイドに存在する特異な界面と熱伝導
    横林秀幸, 橋本裕, 岡本範彦, 足立大樹, 岸田恭輔, 田中克志, 乾晴行
    2010, 日本金属学会講演概要, 146th

  • 低温異常強化を示すL12型Co3(Al,W)およびCo3Tiの変形組織
    木岡現一郎, 岡本範彦, 岸田恭輔, 田中克志, 乾晴行
    2010, 日本金属学会講演概要, 146th

  • CrB2の磁気変態に伴う弾性異常
    田中克志, 永野伸次, 岡本範彦, 乾晴行
    2010, 日本金属学会講演概要, 147th

  • L12型金属間化合物の降伏応力の温度依存性
    岡本範彦, 岸田恭輔, 田中克志, 乾晴行
    2010, 日本金属学会講演概要, 147th

  • fcc/L122相Co基超合金におけるγ’析出相の整合性を保つ添加元素の選択
    田中克志, 大島真宏, 岡本範彦, 乾晴行
    2010, 日本金属学会講演概要, 147th

  • Co3(Al,W)単相合金の引張・圧縮変形挙動
    岡本範彦, 大橋貴志, 岸田恭輔, 田中克志, 乾晴行
    2009, 日本金属学会講演概要, 144th

  • fcc/L122相Co基超合金の単結晶クリープ変形
    大島真宏, 田中克志, 岡本範彦, 乾晴行
    2009, 日本金属学会講演概要, 144th

  • HAADF-STEM法によるRe4Si7の結晶構造解析
    原田俊太, 田中克志, 岸田恭輔, 岡本範彦, 乾晴行, 遠藤徳明, 奥西栄治
    2009, 日本金属学会講演概要, 145th

  • Ir添加Mn4Si7チムニーラダー化合物の結晶構造と熱電特性
    橋本裕, 岡本範彦, 岸田恭輔, 田中克志, 乾晴行
    2009, 日本金属学会講演概要, 145th

  • 遷移金属ダイボライド単結晶の弾性および熱膨張の異方性
    岡本範彦, 田中克志, 乾晴行, 大谷茂樹
    2009, 日本金属学会講演概要, 145th

  • fcc/L12二相Co基超合金のクリープ変形組織
    大島真宏, 田中克志, 岡本範彦, 乾晴行
    2009, 日本金属学会講演概要, 145th

  • 二相組織を有するクラスレート化合物の熱伝導挙動
    北本雄祐, 岡本範彦, 田中克志, 乾晴行
    2009, 日本金属学会講演概要, 144th

  • 一方向配列Nb相を含む複相合金の組織形態と水素透過特性
    橋本裕, 山口裕司, 岸田恭輔, 岡本範彦, 田中克志, 乾晴行, 石川和宏, 青木清
    2008, 日本金属学会講演概要, 143rd

  • 空孔規則配列相を有するReSi1.75基シリサイドの熱電特性
    原田俊太, 田中克志, 岸田恭輔, 岡本範彦, 乾晴行
    2008, 日本金属学会講演概要, 143rd

  • Co3(Al,W)の熱処理による組織変化と力学特性
    大橋貴志, 平山隆浩, 岡本範彦, 岸田恭輔, 田中克志, 乾晴行
    2008, 日本金属学会講演概要, 143rd

  • 熱処理により熱的APBを除去したFePd単結晶の塑性変形
    王晨, 田中克志, 岡本範彦, 岸田恭輔, 乾晴行
    2008, 日本金属学会講演概要, 143rd

  • Co/CO3(Al,W)2相合金のγ’相安定性に及ぼす添加元素の影響
    大島真宏, 田中克志, 岸田恭輔, 岡本範彦, 乾晴行
    2008, 日本金属学会講演概要, 143rd

  • 電子回折によるLa2/3-xLi3xTiO3の結晶構造解析
    後藤健吾, 岸田恭輔, 岡本範彦, 田中克志, 乾晴行
    2008, 日本金属学会講演概要, 143rd

  • Ni3Sn2基金属間化合物の規則構造とリチウム拡散挙動
    小庄孝志, 岸田恭輔, 岡本範彦, 田中克志, 乾晴行
    2008, 日本金属学会講演概要, 143rd

  • Ru2Si3基チムニーラダー相の分布と熱伝導率の相関
    小山達也, 原田俊太, 岡本範彦, 岸田恭輔, 田中克志, 乾晴行
    2008, 日本金属学会講演概要, 143rd

  • L10構造を持つ強磁性化合物の磁気変態温度近傍における磁気異方性
    田中克志, 王晨, 岡本範彦, 岸田恭輔, 乾晴行
    2008, 日本金属学会講演概要, 143rd

  • Ni基超合金のCuboidal組織におけるγ′相の配列と弾性異方性との相関
    橋本和太郎, 田中克志, 岸田恭輔, 岡本範彦, 乾晴行
    2008, 日本金属学会講演概要, 143rd

  • La-Ni系合金の水素吸蔵特性に及ぼすブロック層構成比の影響
    松本竜司, 田中克志, 岸田恭輔, 岡本範彦, 乾晴行
    2008, 日本金属学会講演概要, 143rd

  • クラスレート化合物単結晶の熱および機械的特性
    岡本範彦, 中野貴博, 岸田恭輔, 田中克志, 乾晴行
    2008, 日本金属学会講演概要, 143rd

  • クラスレート化合物の構造と物性
    田中克志, 金正煥, 岡本範彦, 乾晴行
    2008, 格子欠陥フォーラム講演予稿集, 2008

  • Shimizu H., Ohno S., Kume T., Sasaki S., Okamoto N. L., Tanaka K., Inui H., Ohishi Y.
    The Physical Society of Japan, 2008, Meeting Abstracts of the Physical Society of Japan, 63(0) (0), 815 - 815, Japanese

  • 構造I型Ga-Ge混晶クラスレートの高圧ラマン散乱及びX線回折
    大野聡, 久米徹二, 佐々木重雄, 清水宏晏, 岡本範彦, 田中克志, 乾晴行
    2007, 高圧討論会講演要旨集, 48th

  • KISHIDA Kyosuke, WADA Naoyuki, IRIYAMA Yasutoshi, OGUMI Zenpachi, TANAKA Katsushi, INUI Haruyuki
    日本金属学会, Nov. 2006, まてりあ, 45(12) (12), 850 - 850, Japanese
    Introduction scientific journal

  • Ni3Al基金属間化合物冷間圧延材の微細組織
    岸田 恭輔, 出村 雅彦, 平野 敏幸, 田中 克志, 乾 晴行
    Aug. 2006, 日本学術振興会 耐熱金属材料123委員会研究報告, 47(2) (2), 187 - 194, Japanese
    Report scientific journal

  • 熱電金属間化合物―ナノスケール欠陥制御と特性改善
    田中 克志, 岸田 恭輔, 乾 晴行
    01 Jul. 2006, 金属, 76(7) (7), 781 - 786, Japanese
    [Refereed][Invited]
    Introduction scientific journal

  • 表紙を語る−原子空孔の規則配列を操作する方法を探る−
    田中 克志, 岸田 恭輔, 乾 晴行
    01 Jul. 2006, 金属, 76(7) (7), 735 - 735, Japanese
    [Refereed][Invited]
    Introduction scientific journal

  • (Ru,Re)Siyチムニーラダー相の熱電特性に及ぼすAl添加効果
    石田央, 岡本範彦, 岸田恭輔, 田中克志, 乾晴行
    2006, 日本金属学会講演概要, 139th

  • 格子欠陥制御工学-材料機能のイノベーション Re添加Ru2Si3基シリサイドの結晶構造と熱電特性
    石田央, 岡本範彦, 岸田恭輔, 田中克志, 乾晴行
    2006, 日本金属学会講演概要, 138th

  • Ba-Ga-Ge系クラスレート化合物における内包原子サイトの分裂挙動と格子熱伝導率
    岡本範彦, 田中克志, 乾晴行
    2006, 日本金属学会講演概要, 138th

  • Research Report for Structural Control of Steels Through Phase Transformations in high Magnetic Fields Effects of Heat Treatments under a Magnetic Field on L1<sub>0</sub>‐Ordering Alloys
    田中克志, 市坪哲, 松原英一郎, 塩満一彦, 渡辺和雄, 高橋弘紀
    2006, 強磁場を利用した鉄鋼材料の組織制御研究会報告書 平成18年, 61 - 68, Japanese

  • 金属ガラスのガラス転移温度近傍における弾性・擬弾性
    田中克志, 市坪哲, 松原英一郎
    29 Mar. 2005, 日本金属学会講演概要, 136th, 110, Japanese

  • 金属間化合物材料の新たな可能性 Ru2Si3基シリサイドの結晶構造に及ぼすRe添加効果
    石田央, 岡本範彦, SIMKIN Benjamin A, 岸田恭輔, 田中克志, 乾晴行
    2005, 日本金属学会講演概要, 137th

  • (La,Li)TiO3の一方向凝固法による結晶育成と構造解析
    宮田麻衣, 和田直之, 岡本範彦, 岸田恭輔, 田中克志, 乾晴行, 加古智典, 矢田千宏, 入山恭寿, 小久見善八
    2005, 日本金属学会講演概要, 137th

  • 金属間化合物材料の新たな可能性 Type-Iおよびtype-IIIクラスレート化合物の二相組織における熱伝導率異常
    岡本範彦, 金正かん, 田中克志, 乾晴行
    2005, 日本金属学会講演概要, 137th

  • Type-Iクラスレート化合物の原子構造と熱電特性の相関
    岡本範彦, 中野貴博, 田中克志, 乾晴行
    2004, 日本金属学会講演概要, 134th

  • 直方体共振法による弾性率の測定
    TANAKA KATSUSHI
    2001, 材料の微細組織と機能性 -21世紀におけるニーズアンドシーズ, 日本学術振興会 材料の微細組織と機能性 第133委員会, 13 - 18, Japanese
    Introduction other

  • TANAKA KATSUSHI
    日本金属学会, 2001, 日本金属学会会報, 40(6) (6), 564 - 567, Japanese
    Introduction international proceedings

  • FePd,FePtの規則化過程に及ぼす強磁場の効果 (強磁場下の物性の研究--その他)
    田中 克志, 市坪 哲, 天野 雅之
    東北大学金属材料研究所附属強磁場超伝導材料研究センタ-, Jun. 2000, 東北大学金属材料研究所強磁場超伝導材料研究センタ-年次報告, (1999) (1999), 167 - 170, Japanese

  • Effect of external magnetic field on ordering process of FePd alloy
    ICHITSUBO Tetsu
    01 Mar. 1999, 材料とプロセス : 日本鉄鋼協会講演論文集 = Current advances in materials and processes : report of the ISIJ meeting, 12(3) (3), 599 - 599, Japanese

  • 微小試料による弾性率測定法
    TANAKA KATSUSHI
    アグネ技術センター, 1999, 金属, Vol.69(No. 2) (No. 2), 129 - 134, Japanese
    Introduction commerce magazine

  • TANAKA KATSUSHI
    日本金属学会, 1997, 日本金属学会会報, 36(3) (3), 254 - 259, Japanese
    Introduction scientific journal

  • TANAKA KATSUSHI
    日本金属学会, 1996, 日本金属学会会報, 35(4) (4), 380 - 385, Japanese
    Introduction scientific journal

  • 直方体共振法による弾性率の測定
    TANAKA KATSUSHI
    1994, 新素材, 日本工業出版, Vol.5,(No.3, (1994),) (No.3, (1994),), 54 - 58, Japanese
    Introduction commerce magazine

■ Lectures, oral presentations, etc.
  • クラスター展開法によるFCC二元系合金の弾性定数計算
    寺本 武司, 竹内 大次郎, 田中 克志
    日本金属学会2024年春期第174回講演大会, Mar. 2024, Japanese
    Oral presentation

  • MnCoNi のX 線・中性子非弾性散乱
    筒井 智嗣, 脇本 明拓, 梅本 好日古, 池田 陽一, 飯田 一樹, 梶本 亮一, 寺本 武司, 田中 克志
    日本金属学会2024年春期第174回講演大会, Mar. 2024, Japanese
    Oral presentation

  • CrMnFeCoNiサブシステムの極低温における構成元素の有効原子半径の測定
    田中 克志, 中野 希一, 寺本 武司
    日本金属学会2024年春期第174回講演大会, Mar. 2024, Japanese
    Oral presentation

  • TiNi形状記憶合金におけるマルテンサイト組織の弾性定数測定と内部応力状態解析
    寺本 武司, 田中 克志
    日本金属学会2024年春期第174回講演大会, Mar. 2024, Japanese
    [Invited]
    Keynote oral presentation

  • TiNi形状記憶合金のB19’マルテンサイト相の単結晶弾性率測定
    寺本 武司, 田原 正樹, 細田 秀樹, 筒井 智嗣, 田中 克志
    日本金属学会2023年秋期第173回講演大会, Sep. 2023, Japanese
    Oral presentation

  • 晶癖面バリアント形成時の応力場に対する単結晶弾性率の影響
    寺本 武司, 堀尾 昂平, 田中 克志
    日本金属学会2023年秋期第173回講演大会, Sep. 2023, Japanese
    Oral presentation

  • CrCoNiのフォノン分散
    筒井 智嗣, 飯田 一樹, 梶本 亮一, 寺本 武司, 松浦 直人, unping Du, 尾方 成信, 田中 克志
    日本金属学会2023年秋期第173回講演大会, Sep. 2023, Japanese
    Oral presentation

  • 第一原理計算によるBCC不規則合金の単結晶弾性率計算
    堀尾 昂平, 寺本 武司, 田中 克志
    日本金属学会2023年秋期第173回講演大会, Sep. 2023, Japanese
    Poster presentation

  • Ti-Nb-Al形状記憶合金のα”マルテンサイト相における 内部双晶形成時のエネルギー障壁の評価
    寺本 武司, 堀尾 昂平, モハマド コユン, 田中 克志
    日本金属学会2023年春期第172回講演大会, Mar. 2023, Japanese
    Oral presentation

  • CrCoNiミディアムエントロピー合金の加工軟化挙動
    田中 克志, 下原 涼太, 寺本 武司, 上路 林太郎
    日本金属学会2023年春期第172回講演大会, Mar. 2023, Japanese
    Oral presentation

  • CrMnFeCoNiのフォノン分散
    筒井 智嗣, 飯田 一樹, 梶本 亮一, 寺本 武司, 松浦 直人, Junpin Du, 尾方 成信, 田中 克志
    日本金属学会2023年春期第172回講演大会, Mar. 2023, Japanese
    Oral presentation

  • Ni基超合金TMS-26の高温低応力圧縮初期クリープ変形挙動
    田中 克志, 高島 良, 寺本 武司, 高田 裕治, 湯山 道也, 大澤 真人, 川岸 京子
    日本金属学会2023年春期第172回講演大会, Mar. 2023, Japanese
    Oral presentation

  • CrCoNiミディアムエントロピー合金の電気抵抗変化と内部組織の関係
    清水 崚雅, 北角 健太郎, 寺本 武司, 田中 克志
    日本金属学会2022年秋期第171回講演大会, Sep. 2022, Japanese
    Oral presentation

  • CrMnFeCoNiとCrCoNiのX線・中性子非弾性散乱
    筒井 智嗣, 飯田 一樹, 梶本 亮一, bin Mohamad Izlan Mohamad Qayyum, 下原 諒大, 清水 崚雅, 中野 希一, 脇本 明拓, 寺本 武司, 松浦 直人, 田中 克志
    日本金属学会2022年秋期第171回講演大会, Sep. 2022, Japanese
    Oral presentation

  • FCC構造を持つ高エントロピー合金の特異な弾性定数の起源
    田中 克志, 篠原 諒, 大谷 涼, 寺本 武司
    日本金属学会2022年秋期第171回講演大会, Sep. 2022, Japanese
    Oral presentation

  • X線非弾性散乱によるTiNi形状記憶合金のB19’マルテンサイト相の弾性率測定
    寺本 武司, モハマド コユン, 下原 諒大, 田中 克志, 筒井 智嗣, 田原 正樹, 細田 秀樹
    日本金属学会2022年秋期第171回講演大会, Sep. 2022, Japanese
    Poster presentation

  • Ni基超合金の初期クリープにおける応力符号の影響
    高島 良, 寺本 武司, 田中 克志, 高田 裕治, 湯山 道也, 大澤 真人, 川岸 京子
    日本金属学会2022年秋期第171回講演大会, Sep. 2022, Japanese
    Poster presentation

  • CrCoNiミディアムエントロピー合金における短範囲規則の形成に伴う電気抵抗変化
    田中 克志, 北角 健太郎, 篠原 諒, 下原 涼大, 寺本 武司, 上路 林太郎
    日本金属学会2022年春期大会(第170回)大会, Mar. 2022, Japanese
    [Invited]
    Keynote oral presentation

  • CrCoNi ミディアムエントロピー合金における短範囲規則状態の形成と物理的・機械的性質の変化
    田中 克志, 北角 健太郎, 篠原 諒, 下原 涼大, 寺本 武司, 上路 林太郎
    状態図・計算熱力学研究会 第２回研究会, Nov. 2021, Japanese
    [Invited]
    Invited oral presentation

  • CrCoNi合金の短範囲秩序の形成の速度論
    北角 健太郎, 田中 克志, 寺本 武司, 上路 林太郎
    日本金属学会2021年秋期大会(第169回)大会, Sep. 2021, Japanese
    Oral presentation

  • ハイエントロピー合金における電子密度分布
    大谷 涼, 寺本 武司, 田中 克志, 山本 一樹
    日本金属学会2021年秋期大会(第169回)大会, Sep. 2021, Japanese
    Poster presentation

  • 純金属から高エントロピー合金に至る弾性定数変化
    篠原 諒, 寺本 武司, 田中 克志
    日本金属学会2021年秋期大会(第169回)大会, Sep. 2021, Japanese
    Poster presentation

  • Co基二相超合金におけるCoAl基耐酸化被膜材の作製と評価
    森本 健一郎, 寺本 武司, 田中 克志
    日本金属学会2021年秋期大会(第169回)大会, Sep. 2021, Japanese
    Poster presentation

  • TiNbAl形状記憶合金のマルテンサイト変態初期における双晶界面選択の弾性相互作用エネルギー解析
    寺本 武司, 野口 大輔, Mohamad Qayyum, 田中 克志
    日本金属学会2021年春期第168回講演大会, Mar. 2021, Japanese
    Oral presentation

  • CrCoNi合金の短範囲秩序の形成に伴う電気抵抗変化
    北角 健太郎, 伊藤 祐介, 寺本 武司, 田中 克志, 上路 林太郎
    日本金属学会2021年春期第168回講演大会, Mar. 2021, Japanese
    Oral presentation

  • ハイエントロピー合金の特異な力学特性の支配因子解明
    乾 晴行, 土谷 浩一, 佐藤 裕之, 田中 將己, 橋本 直幸, 増野 敦信, 谷本 久典, 金 熙榮, 花咲 徳亮, 田中 克志
    日本金属学会2020年秋期第167回講演大会, Sep. 2020, Japanese
    [Invited]
    Keynote oral presentation

  • CrMnFeCoNiハイエントロピー合金における構成元素の有効原子半径
    田中 克志, 寺本 武司, 楢崎 桃子
    日本金属学会2020年秋期第167回講演大会, Sep. 2020, Japanese
    Oral presentation

  • TiNi形状記憶合金のマルテンサイト変態初期における組織の選択性とエネルギー障壁の関係
    寺本 武司, 永平 和也, 田中 克志
    日本金属学会2020年秋期第167回講演大会, Sep. 2020, Japanese
    Oral presentation

  • Co基二相超合金におけるγ/γ'二相と平衡する耐酸化性皮膜の作製と評価
    森本 健一郎, 寺本 武司, 田中 克志
    日本金属学会2020年秋期第167回講演大会, Sep. 2020, Japanese
    Poster presentation

  • CrCoNiミディアムエントロピー合金における短範囲秩序の形成
    北角 健太郎, 伊藤 祐介, 寺本 武司, 田中 克志, 上路 林太郎
    日本金属学会2020年秋期第167回講演大会, Sep. 2020, Japanese
    Poster presentation

  • Ni基超合金の初期クリープにおける引張と圧縮の非対称性
    徳田龍馬, 寺本武司, 田中克志, 高田裕治, 湯山道也, 川岸京子
    日本金属学会2020年春期（第166回）講演大会, Mar. 2020, Japanese
    Oral presentation

  • 純金属からハイエントロピー合金への弾性的性質の変化
    田中克志, 山田和樹, 寺本武司
    日本金属学会2020年春期（第166回）講演大会, Mar. 2020, Japanese
    Oral presentation

  • TiNi 形状記憶合金のマルテンサイト変態初期組織の選択性と界面エネルギーの関係
    TERAMOTO TAKESHI, 永平 和也, TANAKA KATSUSHI
    日本金属学会 春期講演大会(2019), Mar. 2019, Japanese, Domestic conference
    Public symposium

  • Variation in Positive Temperature Dependence of Strength of L12 Intermetallic Compounds in Co3(Al,W)-Co3Ti Pseudo Binary System
    MIKIO OMAE, TERAMOTO TAKESHI, TANAKA KATSUSHI
    MRS fall meeting & exhibit (2018), Dec. 2018, Japanese, International conference
    Poster presentation

  • Interfacial Energy and Geometry of Twin Boundary Between Martensite Variants in TiNi Shape Memory Alloy
    TERAMOTO TAKESHI, KAZUYA NAGAHIRA, TANAKA KATSUSHI
    MRS fall meeting & exhibit (2018), Dec. 2018, Japanese, International conference
    Oral presentation

  • Co3(Al,W)-Co3Ti擬二元L12型化合物における強度の逆温度依存性
    大前樹生, 寺本武司, 田中克志
    2018年度11月期耐熱金属材料123委員会研究報告, Nov. 2018, Japanese
    Oral presentation

  • 還元熱処理により作製したMagneli相酸化チタンの周期構造と熱伝導特性
    原田俊太, 小坂直輝, 八木貴志, 田中克志, 乾晴行, 田川美穂, 宇治原徹
    日本金属学会2018年秋期講演大会, Sep. 2018
    Oral presentation

  • ルチル型TiO2単結晶への周期的な面欠陥導入に伴う熱伝導率の変化
    小坂直輝, 八木貴志, 田中克志, 乾晴行, 田川美穂, 宇治原徹, 原田俊太
    第79回応用物理学会秋季学術講演会, Sep. 2018
    Oral presentation

  • Co3(Al, W) –Co3Ti擬二元L12型化合物における強度の逆温度依存性
    大前 樹生, TERAMOTO TAKESHI, TANAKA KATSUSHI
    日本金属学会 秋期講演大会(2018), Sep. 2018, Japanese, Domestic conference
    Poster presentation

  • bcc/B2 二相合金Fe-20Ni-20Alの高温クリープ強度
    河合 紀明, TERAMOTO TAKESHI, TANAKA KATSUSHI
    日本金属学会 秋期講演大会(2018), Sep. 2018, Japanese, Domestic conference
    Poster presentation

  • Ni基超合金高温クリープにおける内部応力場の発達とその役割
    TANAKA KATSUSHI
    日本機械学会関西支部 秋季技術フォーラム, Nov. 2014, Japanese, 兵庫県立大学, Domestic conference
    [Invited]
    Invited oral presentation

  • 新規Co基二相耐熱合金開発の現状と問題点
    TANAKA KATSUSHI
    日本鉄鋼協会第136回特殊鋼部会, Jun. 2014, Japanese, 千葉オークラホテル, Domestic conference
    [Invited]
    Invited oral presentation

  • Analytical study of elasticity of transition metal disilicides
    TANAKA KATSUSHI, INUI HARUYUKI
    The Czech-Japanese Workshop on High- Temperature Intermetallics, Apr. 2014, English, Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Brno, International conference
    [Invited]
    Invited oral presentation

  • Variations of lattice constant misfits in Co-based superalloys upon alloying
    TANAKA KATSUSHI, TANAKA KEN
    2014 Spring Meeting of The Japan Institute of Metals and Materials, Mar. 2014, Japanese, Tokyo, 添加元素に応じた格子定数ミスフィットの変化が観察された．一方，この変化の要因を添加元素の金属結合半径と合金内分配で説明することはできない添加元素も多い．Taのように主としてγ’相に固溶しγ’相の格子定数を変化させる添加元素ではほぼ添加元素の金属結合半径で説明できるのに対し， NiやCrのようにな添加元素は，γ-γ’の二相分離の幅を変化させる働きを持ち，結果としてγ相に固溶するW量が変化することで格子定数ミスフィットの値を変化させる働きを持つことが明らかとなった．, Domestic conference
    Oral presentation

  • Effects of Alloying Elements on Physical and Mechanical Properties of Co–Al–W-based L12/fcc Two-phase Alloys
    TANAKA KATSUSHI, INUI HARUYUKI
    THERMEC 2013, Dec. 2013, English, Las Vegas, USA, The changes in the γ’ solvus temperature and the volume fraction of Co-Al-W based alloys with fcc / L12 two-phase microstructures upon alloying with quaternary elements have been investigated. All investigated quaternary elements, except for Fe and Re, increase the γ’ solvus temperatures of Co-Al-W based alloys with varying efficiencies depending on quaternary element. On the o, International conference
    Oral presentation

  • Mg 基LPSO 相の弾性的性質
    UENO AKINOBU, TANAKA KATSUSHI
    日本金属学会2013春期大会, Mar. 2013, Japanese, 東京， 日本, Domestic conference
    Oral presentation

  • Fe-Ni-Al 基bcc/B2 二相合金の高温力学特性の添加元素による変化
    KONO RYOSUKE, TANAKA KATSUSHI
    日本金属学会2013春期大会, Mar. 2013, Japanese, 東京， 日本, Domestic conference
    Oral presentation

  • fcc/ L12二相Co 基超合金の解決すべき問題点
    TANAKA KATSUSHI
    日本金属学会2013春期大会, Mar. 2013, Japanese, 東京，日本, Domestic conference
    Keynote oral presentation

  • Co 基二相超合金の格子定数ミスフィットに対する添加元素の影響
    TANAKA KEN, TANAKA KATSUSHI
    日本金属学会2013春期大会, Mar. 2013, Japanese, 東京，日本, Domestic conference
    Oral presentation

  • 材料組織形成の弾性論を用いた解析
    TANAKA KATSUSHI
    若手フォーラム「組織制御に関する産学連携推進フォーラム」 第4回研究会, Dec. 2012, Japanese, 日本鉄鋼協会, 兵庫県赤穂郡， 日本, Domestic conference
    [Invited]
    Invited oral presentation

  • Microstructural evolution of monocrystalline Co–Al–W-based superalloys by high temperature creep deformation
    Sumitani Takahiro, TANAKA KATSUSHI
    Materials Research Society 2012 Fall Meeting, Nov. 2012, English, Boston, USA, International conference
    Poster presentation

  • Difference in elastic properties of CrB2 determined by microscopic and macroscopic measurements
    TANAKA KATSUSHI, TSUTSUI SATOSHI, OKAMOTO NORIHIKO, INUI HARUYUKI, Baron Alfred Q.R
    Materials Research Society 2012 Fall Meeting, Nov. 2012, English, Boston, USA, International conference
    Oral presentation

  • Role of internal stresses on thermal mechnical fatigue of Ni-based superalloys
    SUMITANI TAKAHIRO, TANAKA KATSUSHI
    日本金属学会2012秋期大会, Sep. 2012, Japanese, 日本金属学会, 松山，日本, Domestic conference
    Oral presentation

  • CrB2における巨視的弾性率と微視的弾性率の違い
    TANAKA KATSUSHI, OKAMOTO NORIHIKO, INUI HARUYUKI, TSUTSUI SATOSHI, BARON Alfred Q.R
    日本金属学会2012秋期大会, Sep. 2012, Japanese, 日本金属学会, 松山， 日本, Domestic conference
    Oral presentation

  • Relationship of creep to deformation microstructure in Co-based superalloys
    Sumitani Takahiro, Tanaka Katsushi, Inui Haruyuki
    The 2012 Spring Meeting of The Japan Institute of Metals, Mar. 2012, Japanese, 日本金属学会, Yokohama-city, Domestic conference
    Oral presentation

  • Elastic energy analysis of microstructural change in Ni-based superalloys
    Tanaka Katsushi
    The 2011 Autumn Meeting of The Japan Institute of Metals, Nov. 2011, Japanese, 日本金属学会, Ginowan-city, Domestic conference
    [Invited]
    Invited oral presentation

  • Elastic anomaly in CrB2 at around the magnetic transition temperature
    Tanaka Katsushi, Nagano Shinji, Okamoto Norihiko, Inui Haruyuki
    International Conference on Advanced Technology in Experimental Mechanics 2011, Sep. 2011, English, Kobe, Japan, International conference
    [Invited]
    Invited oral presentation

  • A Micromechanical Analysis of Creep Deformation Induced Microstructural Evolutions in Nickel Base Superalloys
    Tanaka Katsushi, Hashimoto Wataro, Inui Haruyuki
    Plasticity 2011, Jan. 2011, English, Puerto Vallarta, Mexico, International conference
    [Invited]
    Invited oral presentation

  • Morphology Change of gamma-prime precipitates in gamma/gamma-prime Two-phase Microstructure in Co-based Superalloys by Higher-order Alloying
    Tanaka Katsushi, Ooshima Masahiro, Okamoto Norihiko, Kishida Kyosuke, Inui Haruyuki
    2010 MRS Fall Meeting, Nov. 2010, English, Materials Research Society, Boston, USA, International conference
    Oral presentation

  • Mechanical Properties of Cr5Si3 with the D8m Structure
    Ochiai Yuji, Kishida Kyosuke, Tanaka Katsushi, Inui Haruyuki
    2010 MRS Fall Meeting, Nov. 2010, English, Materials Research Society, Boston, USA, International conference
    Poster presentation

  • Direct Observation of an Ordered Arrangement of Vacancies and Large Local Thermal Vibration in Rhenium Silicide by Cs-corrected STEM
    Harada Shunta, Tanaka Katsushi, Kishida Kyosuke, Okamoto Norihiko, Endo Noriaki, Okunishi Eiji, Inui Haruyuki
    2010 MRS Fall Meeting, Nov. 2010, English, Materials Reaserch Society, Boston, USA, International conference
    Oral presentation

  • Compression of Micropillars of TiAl Coexisting with Ti3Al
    Fujimura Kazuki, Kishida Kyosuke, Tanaka Katsushi, Inui Haruyuki
    2010 MRS Fall Meeting, Nov. 2010, English, Materials Research Society, Boston, USA, International conference
    Poster presentation

■ Research Themes
  • Variation of elastic properties with chemical short range ordering in high entropy alloys
    田中 克志
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area), Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area), Kobe University, Apr. 2021 - Mar. 2023, Principal investigator
    CrCoNiミディアムエントロピー合金試料を一定速度で加熱，冷却した時の電気抵抗の温度変化のその場測定結果を行った．圧延ままの試料では電気抵抗は小さく，熱処理を施すことで電気抵抗が増加することが明らかとなった．加熱過程において800 Kから900 Kの間では一旦熱処理後の試料よりも大きな電気抵抗値となる．圧延ままの試料であることから転位の存在が何らかの形で関与していると考えられるが，詳しいことは分かっていない．冷却速度が異なる場合における電気抵抗変化の違いについても検討した．900 K以下では電気抵抗の冷却速度依存性が見られ，冷却速度が速くなると内部の原子配列が熱平衡状態を保てなくなることが分かる．900 K以上では微分値も冷却速度に依存せず，これ以上の温度では試料が熱平衡状態にあることが確認された．また，熱平衡状態からずれ始める温度を求めると，この温度と冷却速度との間はアレニウスの関係を良く満たすことが分かった．この関係がさらに速い冷却速度に外挿しても成り立つと仮定すると，水焼き入れで実現可能な5000 K/秒の焼き入れ速度では1075 K程度の熱平衡状態が焼き入れ可能であるにすぎないことが明らかとなった． 次に1173 Kから水焼き入れを行なった後，653 K, 673 K, 693 Kと熱処理温度を変化させながら電気抵抗変化を測定した．熱処理温度を変化させた時間において活性化エネルギーを求めると，電気抵抗変化に係る活性化エネルギーは240~270 kJ/molと決定された．これはハイエントロピー合金中の各元素の拡散の活性化エネルギー240~320 kJ/molとほぼ同等である．

  • Acceleration of diffusional transformation by applied stress and its application to microstructural control
    上路 林太郎, 田中 克志
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B), Grant-in-Aid for Scientific Research (B), National Institute for Materials Science, Apr. 2020 - Mar. 2023, Coinvestigator
    鉄鋼材料の機械的性質向上に有効な加工熱処理プロセスにおいて、そのプロセス条件の最適化に必要な応力と変態の相関について、降伏応力以下の外力による拡散変態促進のメカニズムを解明し、不均一応力場を利用した新しい組織制御法を確立することを目的としている。本年度は、実用鋼の一種であるばね鋼（Fe-0.53C-1.5Si-0.8Cr-0.7Mn）に対して、変態後の組織観察を電子線背面散乱回折（ＥＢＳＤ）測定を行い、応力負荷によりパーライトノジュール（ブロック）が微細化することが明らかとなった。ノジュールサイズの微細化は、初期粒径が大きいほど促進される。このことは、応力による拡散変態の促進が核形成サイト密度の増殖によることを示唆している。温度-弾性変形関係に関しては、前年度整備した弾性定数測定系を用い、鋼の準安定γにおける弾性定数の共振法による高温域のオーステナイトの弾性定数の測定結果が得られた。 上記に加えて温度勾配下の圧縮・相変態挙動を実験により調査した。上記データ収集で対象としたものと同じ組成を有する炭素鋼（ばね鋼等）を用いた。やや大きなアスペクト比を有する試験片（長さ40ｍｍ程度×直径8ｍｍ程度）に対して、新調した局所加熱コイルを用いて温度勾配を付与した上で圧縮・相変態挙動を明らかにした。降伏応力以下の応力負荷（あるいは無負荷）状態における温度勾配下変態挙動に焦点を絞り、最大3K/mm程度（試験片長手方向におおよそ100K）の応力勾配を付与することに成功したが、温度勾配を伴うパーライト変態挙動に大きな変化は見られなかった。そこで、円周切り欠きを伴う円柱試験片を用い応力勾配化の変態挙動を測定できる実験条件の検討を行った。

  • Prototyping of lensless X-ray camera and application to element distribution image
    Tanaka Katsushi
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Challenging Research (Exploratory), Kobe University, 30 Jul. 2020 - 31 Mar. 2022
    In this study, we aimed to develop a new method for imaging the X-ray emission site without using a lens system by using a MURA code mask with Bi deposited on the Kapton film. Since the adhesiveness between the Kapton film and Bi was insufficient, fine patterns fell off at etching Bi. This maks it impossible to produce a mask for practical use. The software for reconstructing the image was evaluated using simulated data, and we were able to wrote a software that can be reconstructed correctly. Furthermore, the performance of the software has been improved, and it has become possible to process at a practical speed. It was clarified that the imaging of the X-ray emission site without using a lens system is sufficiently practical, although it is insufficient at present.

  • 単結晶弾性定数から見るハイエントロピー合金の力学特性と構造安定性
    田中 克志
    日本学術振興会, 科学研究費助成事業 新学術領域研究(研究領域提案型), 新学術領域研究(研究領域提案型), 神戸大学, 01 Apr. 2019 - 31 Mar. 2021, Principal investigator
    CrCoNi三元系，およびMnFeCoNi四元系合金に引き続き，他の三元系，四元系合金の単結晶の作製を行った．一方，弾性率測定については，液体ヘリウムの入手難によって，全ての結晶が揃った時点で測定を行うこととしたため，まだ弾性率測定は行えていない．現在，新たに単結晶の作製が完了した系は，三元系ではFeCoNi, MnFeNi, MnCoNiであり，四元系ではCrFeCoNiである．したがって，残りのfcc単結晶の作製が可能と考えられている三元系CrFeNiと四元系のMnCrCoNiの単結晶の作製が終了次第，全ての合金についての弾性率の測定を行う予定である． 弾性率の温度依存性を議論するにあたり，弾性率測定中の構造の安定性について疑義が生じたため，熱処理に伴う結晶の内部構造の安定性について電気抵抗測定によって調査した．その結果，CrCoNiミディアムエントロピー合金では600℃以下の熱処理において，CrMnFeCoNiハイエントロピー合金では700℃以下の熱処理において，熱処理温度の低下とともに顕著な電気抵抗の増加が起こることが明らかとなった．また，熱処理温度を変化させた時の電気抵抗の変化速度から見積もられた，反応の活性化エネルギーはいずれも200kJ/mol程度であり，拡散の活性化エネルギーより小さいものであった．さらに，焼き入れた試料の電気抵抗変化が見られなかった温度域での反応速度を見積もると0.1s以下のオーダーとなり，単に焼入れ時に熱処理時の熱平衡状態を保存することができていないだけと見ることができた．
    Competitive research funding

  • Tanaka Katsushi
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), Kobe University, 01 Apr. 2018 - 31 Mar. 2021, Principal investigator
    The lattice heat transfer rate decreased in the material to which Cr, which has stable trivalent ions, and Zr, which has stable tetravalent ions, decreased, but the electrical resistance increased at a larger rate. It became clear that the additions do not contribute to the improvement of thermoelectric performance. An attempt was made to precipitate a composite oxide in the crystal. The scattering ability of low-frequency phonons of the coarse composite oxide precipitated at the grain boundaries was not very large. We could not find any heat treatment conditions that could realize the dispersion of fine precipitates in the grains.
    Competitive research funding

  • Teramoto Takeshi, Tanaka Katsushi
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B), Grant-in-Aid for Young Scientists (B), Kobe University, 01 Apr. 2017 - 31 Mar. 2019
    In order to reveal the formation mechanism of the initial stage of the martensitic transformation, which is a room temperature structure of shape memory alloy, the interfacial energy of the twin included in the initial stage structure was evaluated by the first principle calculation in Ti-Ni. Twinning interfacial energy is predicted to be the controlling factor that determines the microstructure in the initial stage. However, the amount of the interfacial energy can not explain the formation process, and consideration of elastic strain energy is needed. Therefore, it was supposed that the structure determination of the initial stage microstructure occurred at a relatively large scale.

  • TANAKA Katsushi, SATO Hiroki, TAKAI Yutaka
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B), Grant-in-Aid for Scientific Research (B), Kobe University, 01 Apr. 2014 - 31 Mar. 2017, Principal investigator
    Partially reduced TiO2-x (x~0.1: Magnelli phase) consists of a regular stacking of TiO2 and Ti2O3 layers as a natural superlattice structure. To reduce the thermal conductivity without changing electrical properties, quadlivalient impurities of Zr or Sn are added to the crystal. Zr makes solid solution as expected but Sn does not make solid solution. Thermal conductivity of Magnelli phase does not significantly change upon alloying with Zr. On the other hand, the alloying lowers electric conductivity. As a result, thermoelectric properties are not improved by the alloying with Zr.
    Competitive research funding

  • 田中 克志
    科学研究費補助金／挑戦的萌芽研究, Apr. 2012 - Mar. 2013, Principal investigator
    Competitive research funding

  • 田中 克志
    科学研究費補助金／挑戦的萌芽研究, Apr. 2011 - Mar. 2012, Principal investigator
    Competitive research funding

  • 田中 克志
    科学研究費補助金／基盤研究(B), Apr. 2009 - Mar. 2012, Principal investigator
    Competitive research funding

  • TANAKA Katsushi
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research, Grant-in-Aid for Challenging Exploratory Research, Kobe University, 2012 - 2012
    Geometrically required dislocations are distributed at sub-grain boundaries that corresponds to interfaces of dendrites grown in Ni-based superalloys. In the present study, we have performed compressive creep tests to observe the development of creep dislocation networks at gamma/gamma-prime interfaces, and of parallel raft structure. When a compressive stress is applied along tothe growth direction, the magnitude of primary creep is very small compared with that applied perpendicular to the growth direction. We have constructed a creep testing machine that can use a very small specimen without dislocation networks in it.

  • TANAKA Katsushi
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research, Grant-in-Aid for Challenging Exploratory Research, Kobe University, 2011 - 2011
    A point or areal irradiation of a laser light is equipped to heat a specimen and to detect a specimen temperature. This method is suitable for investigating a local variation of thermal properties of the specimen. In the present study, a line focused laser beam is equipped for heating a specimen to suppress an extinction of heat wave and to restrict a direction of propagation. This allows us to measure not only the thermal diffusivity more preciously but also the anisotropy of the thermal properties. At present, the thermal resistance of the grain boundary is not able to measure quantitatively, however, know-hows of the measurement is accumulating.

  • TANAKA Katsushi
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B), Grant-in-Aid for Scientific Research (B), 2009 - 2011
    In this study, we demonstrate the efficiency as thermoelectric materials of off-stoichiometric oxide semiconductor in terms of electric and thermal conductivity. We succeed to obtain the value of dimensionless figure of merit to be 0. 3 in off-stoichiometric titanium oxide, that is quite large for ubiquitous oxides. The large value is due to a strong phonon scattering at crystallographic shear structure which is largely introduced by a thermal treatment.

  • OKAMOTO Norihiko, INUI Haruyuki, TANAKA Katsushi, KISHIDA Kyosuke, ADACHI Hiroki
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (Start-up), Grant-in-Aid for Young Scientists (Start-up), Kyoto University, 2008 - 2009
    Phase relationships of manganese-substituted ruthenium sesquisilicide alloys have been investigated by using x-ray powder diffraction, scanning and transmission electron microscopy. A series of chimney-ladder phases Ru_<1-x>Mn_xSi_y are formed over a wide compositional range between Ru_2Si_3 and Mn_4Si_7. Directionally solidified chimney-ladder compounds in the Ru-Mn-Si system exhibit a microstructure containing columnar domains of different chimney-ladder phases with compositional interfaces between adjacent phases. Despite a compositional variation, the transition-metal (Ru/Mn) sublattice is continuous over the interface while the Si sublattice is discontinuous. The lattice thermal conductivity of the directionally solidified alloys along the transverse direction decreases by increasing the density of the compositional interfaces while the electrical properties are preserved.

  • ディスプロポーショネーションの材料科学とその工学的応用
    乾 晴行, 岸田 恭輔, 田中 克志, 岡本 範彦
    日本学術振興会, 科学研究費助成事業 萌芽研究, 萌芽研究, 京都大学, 2008 - 2008
    地球環境保全のためCO_2ガス排出量の削減に向け多くの取り組みがなされる中,自動車駆動電源としての水素エネルギーが注目されている.実用的には水素をより多く吸蔵する合金が必要であり,Mg系合金に研究が集中している.Mg系合金では,La-Ni系合金とハイブリッドな水素吸蔵合金を作製すると不均化反応が抑制でき可逆的水素吸蔵放出量を維持できたり,遷移金属との積層体で一連の不均化反応を利用して可逆的水素吸蔵放出量や水素化反応速度を増加させ,水素の放出温度を本質的に低下させる試みがなされていたりと,不均化反応が重要な役割を果たすことが明らかになりつつある.本研究では,不均化反応を促進あるいは抑制する因子を実験的,理論的に探求し,不均化反応を積極的に工学的に応用する方策を見出すことを目的とした.特に,純Mgの水素放出温度に及ぼす応力効果,RE-Ni-Mg(RE:希土類金属)系におけるハイブリッド化合物の不均化反応抑制機構を調べた.純Mgはその水素化物の解離温度が350度と高いが,解離時に応力が加わると解離温度が低くなるとの仮説のものと,熱力学的に解離温度-応力の関係を導き,これを実証した.実証では,計算に基づいて4GPaの応力下,270度で水素化物の解離を行わせ,X線回折により純Mgの体積分率が大きく増加することを見出した.RE-Ni-Mg系ハイブリッド化合物では,REとしてCeを添加するほど不均化反応が促進され,Niの代わりにCoを添加するほど不均化反応が抑制されることを明らかにした.不均化反応の促進,抑制は水素化物の生成エンタルピーの変化により熱力学的に説明でき,ハイブリッド化合物の電池としての応用上,重要な知見が得られた.

  • INUI Haruyuki, KISHIDA Kyosuke, TANAKA Katsushi, OKAMOTO Norihiko
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A), Grant-in-Aid for Scientific Research (A), Kyoto University, 2006 - 2008
    Re, Ruのシリサイドに注目して, これらシリサイドのシリコン副格子(サブラティス)の配列の多様性に基づいた特異な微細組織を制御して, その特性改善および新たな物質探索, 特性向上の指導原理の確立を目指した.「金属副格子を一定に保つことによって電気伝導を低減することなく, Si副格子のナノ・スケール変調から生じる相界面により熱伝導を低減する」サブラティス・エンジニアリングがこれらの目的に有用であることを明らかにした.

  • 全固体リチウム2次電池のイオニクス界面ナノ構造設計
    乾 晴行, 岸田 恭輔, 田中 克志
    日本学術振興会, 科学研究費助成事業 萌芽研究, 萌芽研究, 京都大学, 2007 - 2007
    リチウム2次電池は,高作動電圧,高エネルギー密度から,小型で軽量な電池を構成でき,モバイル機器の駆動電源として使用されているが,一般に,電解質は可燃性の有機電解液で,液漏れ,発火の危険性があり,安全性の確保が大きな課題である.そのため,本質的な安全性の改善を目指して,可燃性の有機電解液を不燃性の固体電解質に置換する全固体リチウム2次電池の研究開発が進められている.電池の起電反応は活物質と電解質の界面で生じることを考えると,界面特性制御も視野に入れた正極/電解質/負極の材料の選定は非常に重要である.本研究では,正極としてLiCoO_2,固体電解質としてLLT((Li,La)TiO_3)を取り上げ,正極/電解質界面に的を絞って,この界面に電気化学的活性を持続的に付与するための条件を界面のナノ構造制御の観点から明らかにすることを目的とした.固体電解質LLTに正極LiCoO_2を貼付して電気化学特性を測定すると,界面構造の相違によりサイクル特性が大きく異なる.すなわち,LLTをへき開し正極を貼付したもの(へき開材)は,へき開後,機械研磨を経て正極を貼付したもの(機械研磨材)よりもはるかにサイクル特性が悪く,前者の充放電の過電圧はサイクル毎に変化するのに対し,後者のそれはサイクル数に依存しない.これは,へき開材ではLLTにLiCoO_2が直接接しているのに対し,機械研磨材では界面のところどころに島状にLLTの非晶質層がナノスケールで形成されてLLT非晶質層が,充放電に伴う正極の収縮・膨張により界面に生じる応力を緩和し割れを防止する役割を果たすためである.そのため,電気化学サイクル後には,へき開材では正極/電解質界面に沿って割れが発生するのに対し,機械研磨材では全く割れが発生しない.LLT単結晶についても同様の結果を得,{110}を最も持続的な電気化学特性を与える表面方位として決定した.

  • Ethics and laws of personal helps (psychological clinics and human care), those theories and development of educational programs
    HAMAUZU Shinji, MATSUDA Jun, TABATA Osamu, TANAKA Katsushi, HAYASHI Saiko, ISODA Yujiro
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B), Grant-in-Aid for Scientific Research (B), Shizuoka University, 2005 - 2007
    This research aims to construct ethics for helping and supporting, based on research results of clinical anthropology, bicethics and applied ethics, by collaborating of staffs participating education of clinical psychologists and experts of social welfare, the Juvenile Act, the Criminal Act, etc, and to develop practical education programs intending to enrich education of "ethics and laws of personal helpers". For this purpose it is also important to search methods of helps corresponding cultural and historical situations of our country through international cornparing of care and to construct an educational system far it. From 2005 to 2006 we made inspection researches in several foreign countries, in each years we organized lectures by lecturers invited from regional persons concerned with personal helping and laws. In 2006 we organized open lectures "Ethics and laws of personal helps" as enlightening activities for citizens about such a problem. As actions aiming to publish a textbook "Case book far ethics and laws of personal helps", we began the comprehensive subject "Ethics and laws of personal help? at the major field "Clinical human sciences" in graduate school, and kept up the discussion concerning concrete cases. From the subject in 2006 we made "Proceedings of documents and resumes for lectures" which we made use of also on the lecture in 2007 and worked out further And in 2007 we organized an open symposium in which we tried to make a dialogue with regional persons concerned based on our research results so far In this discussion it was made clear again that the struggling with ethical and legal dealing is very urgent in the field of personal helps, especially of psychological clinics Although the publication of "Case book for ethics and laws of personal helps" that we planed at first could not be realized inside of our research years, it is now approaching almost the completion and is in preparation now.

  • 分子キラリティー識別のナノ電子回折法
    乾 晴行, 邑瀬 邦明, 岸田 恭輔, 田中 克志
    日本学術振興会, 科学研究費助成事業 萌芽研究, 萌芽研究, 京都大学, 2006 - 2006
    物体には鏡像関係にあり,互いに重ね合わすことができないものが存在する.右手と左手はその一例で,キラルな物体あるいは対掌体,鏡像異性体と呼ばれる.鏡像異性体は,それぞれ単独に存在する時には物理的、化学的性質に差はないが,生体系は基本的に不斉環境にあるため鏡像異性体間で生理活性が異なる場合が多く,医薬品,食品などではこの区別,識別は大変重要である.本研究では,最近,考案・開発したナノ結晶にも応用できる結晶のキラリティー識別のための電子回折法を拡張,発展させて,分子のキラリティー識別を可能にする新規な方法の開発の可能性を検証した.第1ボルン近似を使ったマルチスライス法のアルゴリズムにより回折図形の計算を行った.分子における並進対称性の欠如のため,各スライス毎に回折角に関するピクセルを切って連続的な波数ベクトルにっいてマルチスライス計算を行った.分子には座標軸の取り方に任意性があるが,点群C_<2n>に属するシスチン(C_2対称),DMP323化合物(C_2対称),BphC酵素(C_4対称)で最も対称性の高いC_n軸である2回軸をz軸として取ると,電子線の入射方向をz軸に垂直にセットすれば,振幅は等しく位相が異なる分子構造因子を持つ回折線が非対称に現れ,右手系分子と左手系分子で強度の非対称性が反対称となるため,分子のキラリティー識別が可能であることが分かった.分子としてキラリティーを持ちうる10点群のうち,8点群は2回軸を持つため,同様に2回軸に垂直に電子線を入射させれば,強度の非対称性から分子のキラリティー識別が可能であることが分かった.2回軸を持たない点群C_1,C<2n+1>に属する分子では,本方法でのキラリティー識別は困難である.

  • Estimation of the lifetime of nickel base turbine blades by using elastic strain measurement
    TANAKA Katsushi, UEJI Rintaro, KISHIDA Kyosuke
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B), Grant-in-Aid for Scientific Research (B), 2003 - 2006
    Development of elastic strain in nickel base super alloy during creep deformation has been investigated. The results show that the change in elastic strain is owing to stack creep dislocations at gamma gamma-prime interfaces. Theoretical calculations about the stability of microstructure indicate that the raft structure is stabilized by a small amount of creep dislocations, however, the raft structure is destabilized by a large amount of creep dislocations. The critical amount of creep dislocations agrees with that for perfectly accommodate the lattice misfit between gamma and gamma-prime phases. In the destabilized raft structure, the most stable lamellar plane normal is not the [001] direction but that tilted toward the <111> direction. This is the reason why the raft structure collapses during the creep deformation. The measurement of elastic strain is useful to detect an early stage of creep deformation, however, the measurement is less sensitive to the change occurred in a later stage of its lifetime.

  • 空孔規則相シリサイド半導体の構造物性
    乾 晴行, 田中 克志, 岸田 恭輔
    日本学術振興会, 科学研究費助成事業 萌芽研究, 萌芽研究, 京都大学, 2005 - 2005
    組成幅がほとんどない化合物であるラインコンパウンドには,組成が古典的な化学量論に従わず構成元素比が整数でないものが多数存在する.このようなラインコンパウンドの基本的構造はほとんど既知であるが,実際には基本構造に多量の構造的原子空孔が組み込まれた空孔規則相として存在することが多い.特異な構造ゆえにラインコンパウンド空孔規則相には,その基本構造では考えられない高電気伝導度や低熱伝導率などの特異な物性を示すものがしばしば存在する.最近,我々は新たな熱電変換材料を探索する中,ReSi_<2-X>(X=0.25)やBa_8Ge_<46-X>(X=3)がこのような特異な物性を示すラインコンパウンド空孔規則相であることを発見し,本研究では,構造,特に「空孔規則構造」と「構造と物性の強相関」に関する系統的理解を目指して研究を行った.ReSi_<2-X>では,Reとの価電子数の多寡により空孔濃度を増減させることができ,その結果インコメンシュレート相が形成されるが,合金元素量増加に伴いインコメンシュレート構造は,シアー構造からアダプティブ構造へと変化する.この変化がおきる合金組成は合金元素に依存し,Moなどでは少ない添加量でこの変化が起こるものの,Ru, Fe, Cr, Nbなどでは固溶限ぎりぎりまでシアー構造が安定となる.熱電特性は概して,シアー構造を取る場合に低く,アダプティブ構造を取る場合に高い.たとえば,2%程度の合金添加でアダプティブ構造が形成されるMo添加の場合,[001]方向で得られた無次元性能指数は800KでZT=0.85(n型)であり,2元系Reシリサイドをはるかに凌駕する.添加量としては,シアー構造からアダプティブ構造へ変化するぎりぎりの組成で最も性能が良く,それ以上の添加ではかえって特性を悪くする.

  • Development of new nano-electron diffraction method for identification of crystal chirality and polarity
    INUI Haruyuki, TANAKA Katsushi, KISHIDA Kyosuke
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B), Grant-in-Aid for Scientific Research (B), Kyoto University, 2004 - 2005
    Enantiomorphism is usually referred to and used to describe objects that are lacking of improper rotation(rotoinversion and rotoreflections). Because of the absence of a center of symmetry (1^^-), a mirror plane (m=2^^-) and a 4^^-axis, such enantiomorphic (chiral) crystals or molecules can occur in two different forms that are related as a right hand and a left hand and these enantiomorphically-related crystals belong to either of the 11 crystal classes (point groups). These crystals are mirror related and are not superimposable with each other and one of the two enantiomorphic crystals exhibit optical bioactivities different from the other in most cases Therefore, distinction of chirality of enantiomorphic crystals is sometimes very important, as the well-known example of Thalidmide accident, which occurred as a tragedy due to the harmful side effect of one of the two members of the enantiomorphic crystals, has indicated. We have developed a new CBED method for identification of chirality and polarity of enantiomorphic crystals, in which asymmetry in the intensity of reflections of Bijvoet pairs in an experimental symmetrical zone-axis CBED pattern is compared with that of an computer simulated CBED pattern. The intensity difference for reflections of these Bijvoet pairs results from multiple scattering (dynamical nature of electron diffraction) among relevant Bijvoet pairs of reflections, each pair of which have identical amplitude and different phase angles. Therefore, the crystal thickness where chiral identification is made with the present method is limited by the extinction distance of Bijvoet pairs of reflections relevant to multiple scattering to produce the intensity asymmetry, which is usually of the order of a few tens nm. With the present method, only a single CBED pattern is sufficient and chiral identification can be made for all possible enantiomorphic crystals that are allowed to exist in crystallography.

  • Change in Financial System and Disposal of bad debts and Research on Law and Policy for Regional financial institution-Small Companies
    TANAKA Katsushi, FUJIHARA Toshio, HASEGAWA Shin, ISHIRO Hiromu, TORIHATA Yoichi, YAMAMOTO Yoshihiko
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B), Grant-in-Aid for Scientific Research (B), SHIZUOKA UNIVERSITY, 2002 - 2004
    Content of Report I Financial system and Regional Financial Institution 1 The Reform of Financial system and Regional-Medium-Small Companies 2 Financial Regeneration and Relationship-Banking II The Impact of Financial System Reform on Regional Finance 1 The Study of Financial Administration concerning Regional Finance 2 The Bankruptcy of Ashikaga Bank and the Reconstruction of Regional Finance 3 The Theoretical Problem on Regional Finance 4 The Economic Crisis and The Procyclicality III Disposal of bad debts, and Reform of Mortgage-Guaranty 1 Regional Financial Institution and Mortgage-Guaranty 2 Disposal of bad debts and Mortgage-Guaranty 3 Asset Securitisation and Mortgage-Guaranty IV Problems about the Corporation Law on Disposal of bad debts 1 Deregulation of Purchase of its own Shares by Company 2 Issue of the Right to subscribe for New Shares against the Hostile Takeover 3 Change of Law for Sharetransfer-Restriction 4 Special Favorable Issue of New Shares and the Responsibility of the Director to the Third-Parties 5 Problems of the Right to peruse the Accountingbook by the Shareholder V The Phases of Financial Crisis in Japanese Capitalist

  • 局在量子構造探求のための研究基盤の体系化
    足立 裕彦, 高野 幹夫, 田中 功, 菅野 了次, 田中 克志, 吉田 朋子
    日本学術振興会, 科学研究費助成事業 特定領域研究, 特定領域研究, 京都大学, 2000 - 2004
    本研究班では,局在電子構造の関与する複雑系についてのシミュレーションを行い,実験と密接な連携を行うことを目的としている。計算手法は主に平面波基底の第一原理擬ポテンシャル法を採用し,必要に応じて,原子軌道関数基底でのバンド計算を併用した.本年度としての成果を以下に箇条書きにする. 1)ZnOおよびMgO中のAlおよびGa溶質元素の存在状態を第一原理計算で予測した上で,本グループにてppmオーダーの不純物添加系を系統的に作製し,陽イオン空孔と不純物との相互作用を阪大グループとの共同研究での陽電子寿命測定により直接的に検証した.このようなextrinsitc要因の陽イオン空孔の生成をppmレベルで直接検証したのは世界ではじめての成果である. 2)民間企業との共同研究腕スピネル型LaCrO_3中のCr空孔の生成についての理論計算を行った.この結果は,酸化物固体燃料電池(SOFC)のセパレータの材料設計に有用である. 3)XANES/ELNES理論計算法を,米国ミズーリ大のChing教授らとの共同研究で確立し,酸化物系,窒化物系などで多くの応用例を示した. 4)ppmオーダーの不純物を添加したZnOおよびMgO系について,SPring8でのXANES実験を行い,超微量元素の定量的な状態分析技術を確立した. 5)新規リチウムイオン導電体の探索を,実験と理論計算の連携によって進めた。 これらは,すべて,特定領域の研究グループ間での密接な連携のもとに成り立っている.

  • New thermoelectric materials with high performance (ZT>l)-Re silicide 4
    INUI Haruyuki, TANAKA Katsushi
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B), Grant-in-Aid for Scientific Research (B), KYOTO UNIVERSITY, 2002 - 2003
    There is a renewed interest in thermoelectric materials because of the increased attention to environmental safety. The performance of thermoelectric properties is usually evaluated with the so-called dimensionless figure of merit ZT where Z=α^2σ/κ, and, α, σ, κ denote Seebeck coefficient, electrical conductivity respectively and thermal conductivity. The performance is better for the larger ZT value and it is generally believed that the condition of ZT>1 must be satisfied for thermoelectric materials to be practically used. We have recently found that Re-silicide exhibits a large ZT value close to ZT=1. In the present study, we made an effort to further improve the thermoelectric performance of this Re-silicide through ternary alloying. We expect the performance improvement not only through the changes in electronic structure but also through microstructure changes such as the change in the density and arrangement of Si vacancies and the formation of incommensurate structure. The binary silicide exhibits ZT=0.75 at 800K when measured along [001]. When transition-metals are replaced with Re, incommensurate microstructures are usually formed starting with the shear structure followed by the adaptive structure as the alloying content increases. The alloying amount at which the transition from the shear to adaptive structures occurs depend on each alloying elements. This occurs at a low content for Mo and W while the adaptive structure does not form within the solubility limit for Ru, Fe, Cr and Nb. Generally speaking, the property improvement occurs when the alloy takes the adaptive-type structure, whereas when the alloy takes the shear-type structure, no significant improvement occurs. The ZT value of 0.85 is achieved for 2at.% Mo added Re-silicide, which exhibits an adaptive structure. When Al is added to replace Si, the adaptive structure is locally formed in the close vicinity of twin boundaries. This leads to the significantly decreased thermal conductivity, resulting in the Zt value greater than 1 at 400K.

  • Development of a mechanical spectroscopy measurement system for an extended temperature range and its applications.
    NUMAKURA Hiroshi, TANAKA Tatsushi
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B), Grant-in-Aid for Scientific Research (B), Kyoto University, 2001 - 2003
    (1) Development of the system A system for characterizing the elasticity and anelasticity of solids has been successfully developed, which works by the forced-vibration method in the frequency range between 10^<-5> Hz and 10 Hz from room temperature to 1,000℃. It measures the relation between the stress and strain (the real and imaginary parts of the complex elastic modulus) under forced torsional vibration of a rod or plate-shaped specimen, of 0.5-1 mm in thickness and 10-50 mm in length, with a strain amplitude between 10^<-5> to 10^<-4>. The measurement sequence is fully automated with a computer. With the temperature held constant, measurements are repeated with sweeping the frequency, thereby obtaining the elastic modulus and internal friction as functions of frequency. It is also capable of free-decay measurements in resonance vibration, at a constant temperature or under a steady temperature variation. (2) Applications Anelastic relaxation due to jumps of antisite atoms in L1_2 ordered alloys has been measured, from which the jump rates of the atoms and the diffusion coefficients have been successfully evaluated. The relaxation effects due to stress-induced reorientation of interstitial solute atoms in bcc metals have been systematically measured, and it has been verified that the instrument can determine the relaxation strengths and relaxation rates at satisfactory accuracy.

  • Structural Studies of Supercritical Fluid Metals using Synchrotron Radiation
    TAMURA Kozaburo, SHIMOJO Fuyuki, HOSHINO Kozo, INUI Masanori, UTSUMI Wataru, FUNAKOSHI Kenichi
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Specially Promoted Research, Grant-in-Aid for Specially Promoted Research, 1999 - 2003
    We have performed structural investigations on expanded fluid metals such as Hg, Rb and Se focusing on the metal-nonmetal (M-NM) transition. These substances are typical examples in which the M-NM transit ion occurs with volume expansion. Hg is a divalent metal and the M-NM transition with the Wilson type takes place. In the M-NM transition of fluid Rb the electron correlation is considered to play a key role. Se is a liquid semiconductor which shows the semiconductor-metal-insulator transition with expansion. We have measured x-ray diffraction, small angle x-ray scattering and inelastic x-ray scattering at temperatures up to 2000 K and pressures up to 2000 bar with He gas compression, in the wide density region from liquid to dense vapor surrounding the liquid-vapor critical point, by the use of synchrotron radiation at SPring-8. We have accumulated structural data of static and dynamic ones such as S(Q), g(r) and S(Q,ω). We have obtained important results showing strong correlation between the M-NM transition and the structural change. For example, small angle x-ray scattering measurements for fluid Hg reveals that a weak density fluctuation appears accompanying the M-NM transition. From the inelastic x-ray scattering measurement for fluid Hg we have observed a fast sound at the M-NM transition region. The sound velocity is triple the ultrasonic velocity. The fast sound is strongly connected with the fluctuation in the local structure with the time-and-space scale of nm and ps which may induce the M-NM transition. In Rb and Se we have also obtained important results. For fluid Rb we have developed a molybdenum cell the use of which enabled us the structural studies up to the supercritical region.

  • Trial construction of a non-contacting measurement system of elastic constants for tiny crystals
    TANAKA Katsushi, KODAMA Isao
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B), Grant-in-Aid for Scientific Research (B), 2001 - 2002
    A new apparatus for measuring elastic, constants of tiny crystals has been developed. The appa rates is based on the Brillouin scattering that is frequently applied to the measurement of non-metallic materials, for example ceramics or organic materials. The most of apparatus for measuring the Brillouin scattering in uses Ar-ion laser that has very large volume and electrical power required is quite large to obtain enough output power. We adopt a new light source that is diode pumped solid state (DPSS) laser, which has very small volume and high efficiency of conversion from electrical to light. The most important point of the light source for the Brillouin scattering is the line width (purity) of the light. We have checked the purity and confirmed that the line width is enough narrow for the Brillouin scattering Another key part of the apparatus is light detector ; the detector must has high sensitivity, stability and low noise feature. A photo multiplier is frequently used to the detector, however, conventional one has low quantum efficiency. We adopt a new type of photo multiplier that has a different material to emitter with high quantum efficiency of about 40% for the light of 532nm By using such newly developed parts, we have succeeded to construct a new apparatus having small volume and high efficiency

  • Enhancement of the rafting in Ni-based superalloys by controlling elastic misfit
    TANAKA Katsushi
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), Grant-in-Aid for Scientific Research (C), KYOTO UNIVERSITY, 2001 - 2002
    The elastic energies associated with the formation of raft structure of Ni-based superalloys has already been calculated and discussed by Nabarro et al. However, this involves an uncertain part about the method of approximation. Our calculation in the framework of purely elastic regime concerning a macroscopic shape deformation indicates that their conclusion is wrong owing to its method of approximation. Our calculation also leads the normal raft always forms regardless to the sign of the lattice misfit and external stress. This result does not agree with the experimental results and indicates that the mechanism of rafting cannot be explained by the calculation in the framework of purely elastic regime. When creep dislocations are induced before rafting, our calculation indicates that the dislocations can creep into so called normal channels but cannot creep into parallel channels. This anisotropic behavior of the motion of creep dislocations changes the spherical symmetry of the lattice misfit into the tetragonal symmetry which makes the morphology of raft as experimentally observed. The driving force for rafting in the framework of elastic regime is very small in comparison with other thermodynamic energies. So, it is difficult to explain the mechanism of rafting only by the elastic interactions. That in the framework of elastic-plastic regime where creep dislocations are taken into account is quite large and mainly depends on the lattice misfit. We conclude that the dominant factor for the choice of morphology of rafting and the elastic misfit is the secondary factor.

  • Powdering limit of hydrogen absorbing intermetallic compounds
    YAMAGUCHI Masaharu, ITO Kazuhiro, TANAKA Katsushi
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A), Grant-in-Aid for Scientific Research (A), Kyoto University, 2000 - 2002
    Mechanisms of the reversible hydrogen absorption and desorption in Ti_3Al-base alloys was studied by means of pressure-composition isotherm measurements and microscopy observations before and after hydrogen absorption on specimens subject to heat treatment and cold rolling. The alpha-hydride to beta-hydride phase transformation in the Ti_3Al-base alloys occurs at a very low pressure and is reversible under normal conditions. However, the transformation between beta and gamma hydrides can be made reversible if the specimen is heat treated so that it contains O-phase in its microstructure or is appropriately deformed by cold rolling. The beneficial effects of O-phase on hydrogen absorption/desorption were demonstrated in three Ti-AT-Nb alloys with compositions in the vicinity of Ti_2NbAl. The beneficial effects are found to be related to the structure and strain field of O-phase rather than the interface between the O-phase and matrix. Their hydrogen absorption and desorption properties are improved when they are mildly deformed. Microstructure observations show that the beta and gamma hydride transformation occurs in a way very similar to the martensitic transformation and can be analyzed within the frame work of the martensitic transformation. The lattice shear deformation is accomplished by a high density of screw dislocations in the transformed laths. Such screw dislocations can be introduced by cold rolling. The hydrogen absorption/desorption properties of other intermetallic materials may be expected to be improved similarly to Ti_3Al-base alloys. Thus, the hydrogen absorption and desorption of Mg-Ca-Ni alloys, which absorb hydrogen easily and form a very stable hydride, was investigated. However, we have not succeeded in enhancing their hydrogen absorption and desorption properties yet. Further work is needed to clarify the reason for this.

  • Mechanism of atomic diffusion in nickel-based intermetallic compounds of L1_2-type
    NUMAKURA Hiroshi, TANAKA Katsushi
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), Grant-in-Aid for Scientific Research (C), KYOTO UNIVERSITY, 1999 - 2000
    The mechanism of atomic diffusion in Ni_3Al, Ni_3Ga and Ni_3Ge has been studied by examining the thermodynamic properties of these materials, most importantly the concentrations of intrinsic point defects, using various experimental techniques. The hypothetical order-disorder transformation temperature of Ni_3Al has been evaluated from the transformation temperatures of a series of alloys Ni_3 (Al, Fe). The transformation temperatures have been determined by in situ measurements of electrical resistivity, and extrapolation to zero Fe content gives 1721 ± 34 K as the transformation temperature of Ni_3Al. This value is in good agreement with the value 1680-1740 K deduced from an analysis of thermodynamic activity data using the results of Monte-Carlo simulation. We proposed earlier an atomistic model of diffusion, where both Ni and Al atoms are assumed to migrate in the crystal primarily by the vacancy mechanism in the sublattice for Ni atoms (the α sublattice vacancy mechanism) ; the model can reasonably explain the diffusivities of Ni and Al in Ni_3Al. In that discussion, which is based on a pair interaction model of thermodynamic properties, the value of the effective interaction energy between atoms is most critical. The transformation temperature is physically equivalent to the effective interaction energy, and thus the value obtained in this investigation substantiates the discussion made earlier. The thermodynamic activity of components has been measured for Ni_3Ga and Ni_3Ge by solidelectrolyte electromotive-force method. For Ni_3Ga, the effective interaction energy has been determined to be 0.101 ± 0.002 eV from the variation of the activity with composition. The concentrations of point defects and the thermodynamic factor for chemical diffusion have been estimated with the aid of a thermodynamic model, and on their basis the mechanism of diffusion has been examined. The data of tracer diffusion and chemical diffusion for this compound can also be accounted for by the α sublattice vacancy mechanism. The method of activity measurements employed has turned out inappropriate for Ni_3Ge. To resolve the problem, knowledge of the details of the Ni-Ge-O ternary phase diagram is required but is not available at the moment. This is the task left to the future. Thus, no reliable value of the effective interaction energy in this compound has been obtained. Nevertheless, it has been shown that the diffusion behavior in this compound can be understood in terms of the α sublattice vacancy mechanism, if the interaction energy is assumed to be as high as 1.5eV.The α sublattice vacancy mechanism is thus a most plausible mechanism of diffusion for this class of materials.

  • Inner displacement and directional bonding in transition metal disilicides
    TANAKA Katsushi
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), Grant-in-Aid for Scientific Research (C), KYOTO UNIVERSITY, 1997 - 1998
    For the first step of this project, we have measured single crystal elastic constants of transition metal disilicides with the C11_b, C40 and C54 structures. The elastic constants have been analyzed by the valence force field approach where the inter-atomic interaction is classified into two terms ; bond-stretching and bond-bending. Relative values of the coefficients of these two terms for each transition metal disilicide indicate the directionality of the inter-atomic bonding. The directionality of inter-atomic interaction in the materials with the C11_b structure is the strongest one, and that in the materials with the C40 structure are classified into two groups. The strength of TiSi_2 is located at the middle position between the two groups of the C40 structure. For the next step, we have performed the X-ray analysis to refine the crystallographic parameters of these compounds. The analysis indicates that the position of silicon atoms in the materials are slightly displaced from the position compiled in the data book. The displacement is associated with the anisotropic inter-atomic interactions of Si-Si and Si-TM.This is clearly demonstrated from the electron distribution maps which are constructed from the measured intensities of the diffraction by the maximum entropy method.

  • Point-defect properties and diffusion mechanism in intermetallic compounds of L1_2 type
    KOIWA Masahiro, NAKAJIMA Hideo, TANAKA Katsushi, NUMAKURA Hiroshi
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B), Grant-in-Aid for Scientific Research (B), KYOTO UNIVERSITY, 1996 - 1997
    We have studied the properties of point defects and diffusion behavior in A_3B itermetallic compounds of L1_2 ordered structure, Ni_3Al, Ni_3Ga and Ni_3Ge. 1.The formation energies and migration energies of vacncies and substitutional defects in Ni_3Al, as well as other quantities characterzing the defect properties, have been calculated by computer simulation, using an improved set of inter-atomic potntials for Ni_3Al. 2.Positron annihilation experiments have been carried out to determine the formation energy of vacancies in Ni_3Ga. It is in the range between 1.7 and 1.8eV. 3.The tracer-diffusion coefficients of the constituent elements have been measured for Ni_3Ga and Ni_3Ge over a wide temperature range. The diffusivity of Ni is close to the self-diffusivity in pure Ni. The diffusion coefficient of Ga in Ni_3Ga is about 1/2 times that of Ni, whereas the diffusion coefficient of Ge in Ni_3Ge is less more than two orders of magnitude smaller than that of Ni. 4.Chemical diffusion coefficient has been measured for the three compounds by single-phase interdiffusion experiments. The chemical diffusion coefficient increases with increasing the concentration of the minor element (B in A_3B), the dependency being the strongest in Ni_3Ge. 5.The thermodynamic factor in chemical diffusion has been formulated in the framework of the pairwise interaction model for the thermodynamics of ordered alloys. By analysing experimental data of thermodynamic activity, the thermodynamic factor for Ni_3Al has been evaluated, and using this value the diffusivity of Al in Ni_3Al has been estimated to be about 1/3 times the diffusivity of Ni. 6.A model for the atomic diffusion processes in these materials has been proposed : the diffusion of both species of A atoms, A and B,occur in the sublattice of atoms via ordinary vacancy mechanism. The model can account for the oberved magnitudes of the diffusion coefficients and their variations with composition.

  • 金属シリサイドの弾性特性とその温度依存性
    田中 克志
    日本学術振興会, 科学研究費助成事業 奨励研究(A), 奨励研究(A), 京都大学, 1996 - 1996
    本研究では純Si,CoSi_2,WSi_2,VSi_2,MoSi_2,TiSi_2の弾性率の測定を行う予定であったが,時間的な制約からMoSi_2(Cll_b)およびTiSi_2(C54)の単結晶弾性定数の測定を4K〜1373Kの温度範囲で行った.これらの遷移金属シリサイドの弾性的性質に共通することは,ポアソン比が0.2以下と非常に小さいことであり,これは格子内部における結合の方向性が強いことを示唆している. 一方,これら遷移金属シリサイドを構成する機何的な原子配列の類似性に着目し,全ての独立な弾性定数を,各種変形に対応した最近接原子間距離の変化と結合角の変化の2つのパラメータで表す試みを行った.その結果,Cll_b,C40,C54と異なった結晶構造をとる遷移金属シリサイドの弾性的性質が,その独立な弾性定数の個数(それぞれ6個,5個,9個)によらず,すべての結晶構造に共通な2つのパラメータで良く記述されることが明らかとなった.このことは,これらの物質の弾性異方性の違いがほとんど内部の原子配列の違い(原子層間のスタッキングの違い)に依っており,原子種の違いによる原子間結合の強さ,方向性の違いによる効果は極わずかなものであることを示している. またこの解析の結果,弾性率の温度変化は結合角に依存する部分の軟化が大きく,熱振動による原子位置のボケが大きく温度変化に寄与していることが明らかとなった. 以上の結果は1997年4月に開催される「高温における金属間化合物に関する国際会議」で発表されるとともに投稿論文としてまとめられる予定である.

  • 高温下における金属間化合物の弾性挙動
    小岩 昌宏, 田中 克志
    日本学術振興会, 科学研究費助成事業 重点領域研究, 重点領域研究, 京都大学, 1994 - 1994
    1.測定精度の向上 直方体共振法による弾性率測定では、コンピュータによる共振周波数の計算精度と試料を直方体に整形する際の理想的な直方体形状からのずれの2点が測定精度全体の大きな割合を占めている。近年のコンピュータの著しい発達により、高精度の計算を短時間で行うことができるようになり、試料の整形のずれが大きな誤差の要因となっていた。今回新たに購入した研磨機とゴニオメータとを組み合わせて用いることによって、従来の方法より簡単に高精度の試料を作成することが可能となった。その結果、理論的に計算された共振周波数と実測値はほとんど一致するようになった。また、同一組成の試料を2個用意し、それぞれ独立に弾性率の測定を行った結果、誤差の大きいものでも約1%程度と、数mm角の試料から非常に高精度の弾性率測定が行われていることが確かめられた。 2.高温弾性特性の測定 上記のように本方法における弾性率の測定精度を確認した後、Ni3Geに対して弾性率の温度依存性の測定を行った。本金属間化合物は、以前の測定において弾性異方性の温度変化に異常が見られた系である。精度の高い今回の測定においても同様の異常が見られ、さらにその異常の観察される温度が組成によって変化するという新たな知見を得ることができた。

  • 直方体共振法による低対称性物質の弾性率測定
    田中 克志
    日本学術振興会, 科学研究費助成事業 奨励研究(A), 奨励研究(A), 京都大学, 1994 - 1994
    1.振動モードの測定 共振時の直方体試料の両端点における変位を直接測定する装置を新たに設計、製作した。この新しい原理に基づく装置を用いて、すでに数値解析により変位の対称性が分かっている試料に対して実験的に変位の対称性の測定を行った結果、両者は一致し本装置によって試料の両端点における変位の対称性、すなわち振動モードの決定を実験的に行うことができることを確認した。 2.Ti_3Alの弾性率測定 本方法による振動モードの決定によって、従来は直方体共振法のみによってはその測定が実質的に不可能であるとされてきた六方晶の弾性率測定が可能となった。Ti_3Alは次世代高温構造材料として期待されている物質であり、その弾性率の値を多くの研究者が必要としているにも拘わらず未だその測定がなされていなかった六方晶の物質である。本試料の直方体への整形には新たに購入したダイアモンド噴霧器を用いることによって整形精度を高める工夫を行った。この物質に対して本方法による弾性率の測定を試みた結果、世界で初めてこの物質の弾性率の値を決定することができた。求められた弾性異方性は純チタンのそれに比較的近く、特に際だった特徴は見ることができなかったが、ポアソン比は比較的小さな値であった。これは金属間化合物の結合の方向性を反映しているものと思われる。

  • 金属間化合物の非化学量論性と弾性特性
    小岩 昌宏, 田中 克志
    日本学術振興会, 科学研究費助成事業 重点領域研究, 重点領域研究, 京都大学, 1993 - 1993
    液体ヘリウム温度における弾性率測定装置の製作 液体ヘリウム温度での弾性率を効率良く測定するため、温度変化および試料交換が容易な連続フロー型クライオスタットCF-1200(オックスフォード・インストゥルメンツ社製)を設備備品として購入した。また、このクライオスタットに合わせて、試料セルを新たに設計、製作した。現在、京都大学極低温センターのヘリウム液化機の運転が停止しているため十分なテストが行えていないが、いくつかの金属間化合物の極低温における弾性率の値が明らかになりつつある。 非化学量論性と弾性特性との関連 いくつかの第3元素を添加したNi_3(Al,X)について弾性率測定を行った。組成による違いを議論する前に、同一組成の試料を用いて直方体共振法の測定精度について検討を行った。その結果、ほとんどの測定値は0.5%以内のばらつきの範囲に入っていることが分かった。特にC_<44>については誤差のほとんどが密度の誤差から生じており、密度が正しく測定されれば0.1%程度の誤差しか生じないことが明かとなった。他の弾性率については密度の他に試料の直方体からの僅かなずれが誤差の要因であった。これについても、さらに正確な直方体形状に試料を加工することによって精度の向上が期待できる。 組成の違いによる弾性率の違いは極く小さなものであるようで、残念ながら今回の測定では上記の測定誤差のなかに入ってしまい、系統的な結論を出すには至らなかった。X線回折による格子定数の測定などによって密度を正確に導きだせば、上記の測定誤差をかなり小さくすることが可能である。非化学量論性と弾性特性との関連を明らかにするためには、今後このような点も考慮に入れて、さらに正確な測定を行う必要がある。

  • 金属間化合物の高温弾性特性
    小岩 昌宏, 田中 克志, 沼倉 宏
    日本学術振興会, 科学研究費助成事業 重点領域研究, 重点領域研究, 京都大学, 1992 - 1992
    1000℃近傍までの高温における単結晶の弾性定数測定装置を製作し、種々の金属間化合物について測定を行った。用いる試料は、一辺が2mm程度の直方体であり、種々の固有振動を励起し、その共振振動数の値から弾性定数をもとめる。振動の励起と検出には圧電素子をトランスデューサーとして使用する。常温近傍の測定は、圧電素子と試料が直接接触する配置で行うが、高温測定の場合には、アルミナ・ロッドを振動伝達棒として用い、その末端近傍に圧電素子を接着した。この方式では、共振スペクトルが振動伝達棒の共振の影響を受けるため、試料自体の共振振動を弁別するのに熟練を要し、解析に時間がかかるが、圧電素子自体は加熱されないため、広範な温度域での測定が可能となる。 立方晶の場合、独立な弾性定数はC_<11>、C_<12>、C_<44>であるが、共振スペクトルから弾性定数をもとめる際には、C_<44>とポアソン比ν、異方性因子Aを変数としてえらび、あらかじめ、νとAの種々の組合せについて期待されるスペクトルを計算しておき、実測スペクトルをこれらと比較して近似的な値をもとめ、内挿により正確な値を決定した。 上記の装置および解析方式により、Ni基のLl_2型化合物i_3X(X=Mu,Fe,Al,Ga,Ge,Si)について、80K〜1200Kにおける弾性定数をもとめた。これらの化合物の弾性的性質は、確子定数の大きさと関連があること、Ni_3Geの弾性異方性Aは温度の上昇とともに低下するが、400℃近傍で最小値を示したのち増加すること、など興味ある結果が得られた。

  • メゾスコピックスケールの不均一組織による弾性の変化の解明
    田中 克志
    日本学術振興会, 科学研究費助成事業 奨励研究(A), 奨励研究(A), 京都大学, 1992 - 1992

  • The construction of a prototype apparatus for measurement of elastic constants with small specimen
    KOIWA Masahiro, MAEZONO Akikazu, TANAKA Katsushi, NUMAKURA Hiroshi
    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Developmental Scientific Research (B), Grant-in-Aid for Developmental Scientific Research (B), KYOTO UNIVERSITY, 1991 - 1992
    The elastic constants are fundamental material constants. Measurements of single crystal elastic constants have been usually performed by ultrasonic techniques, which essentially measure the velocity of elastic waves propagating in a material ; the specimen size required is typically about 10mm in length. It is not always easy to obtain single crystal specimens of such a size, in particular of "new materials". The alternative method which allows the use of smaller specimens is the rectangular parallelepiped resonance (RPR) method. In the RPR method, the measurement of the resonance spectrum is relatively easy, but the analysis of the spectrum to derive the elastic constants is laborious. We have developed a systematic and efficient method of analysis of the resonance spectrum valid for cubic symmetry crystals. The new method allows the analysis by a conventional personal computer. We apply the method to determine of the elastic constants of several intermetallic compounds in wide temperature range, from 77K to 1200K.The resonance frequencies in such a wide temperature range are obtained by a newly constructed apparatus. In the conventional method, the analysis of the RPR spectrum is made without any information on the vibrational mode of each resonance peak. To overcome this essential shortcoming, we have attempted to determine the resonance mode of each resonance peak by measurement of the symmetry of the deformation of the specimen. A new apparatus with two transducers to detect the displacements has been constructed, and used successfully to determine the vibrational mode.

  • Elastic properties of crystal lattice
    Competitive research funding

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