Sendai, Miyagi, Japan

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Institute for Materials Research
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Advanced Institute for Materials Research (WPI-AIMR)
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    ABSTRACT: c-axis alignment in a polymer or crystal structure has drawn attention in numerous scientific and technological applications, including crystals, thin film growth, electro-optic devices, and phase difference optics. We here demonstrate a new approach based on retardation measurement that can obtain the direction of the c-axis alignment. This is employed to visualize the three-dimensional direction of continuous crystals as a thin optical film utilizing a liquid crystal panel, using retardation analysis equipment with high resolution measurement capability. The direction of the c-axis alignment is shown so as to allow a detailed characterization of the direction perpendicular to the plane. In this analysis, the direction of the c-axis alignment is identified, and differences between molecules at inequivalent sites are quantified. The results suggest that the excellent lubrication properties of the c-axis alignment may be due to a significant localization in lateral directions.
    Optics & Laser Technology 01/2015; 65:189–193. DOI:10.1016/j.optlastec.2014.07.022
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    ABSTRACT: The (3+13+1)-dimensional crystal structure of a higher manganese silicide (MnSiγ) phase is revealed using in situ high temperature powder X-ray diffraction (XRD) above room temperature. The compound consists of two tetragonal subsystems of [Mn] and [Si] with an irrational c -axis ratio γ=cMn/cSiγ=cMn/cSi. The in situ XRD results show that the MnSiγ phase is stable, in a vacuum of ∼∼1 Pa, up to 1093 K and partially decomposes into the monosilicide (MnSi) phase with further increase in temperature. Refined a - and cMncMn-axis lengths increase linearly and the thermal expansion coefficients are comparable with those of typical metallic electrode materials. In contrast, cSicSi-axis length changes its increment against temperature at TBDTBD ∼773 K. As a result, the temperature dependence of γγ starts to decrease gradually above TBDTBD, from 1.7387(1) (at 773 K) to 1.7244(1) (at 1173 K). This finding implies that the MnSiγ phase consecutively changes its irrational composition above TBDTBD, a typical temperature where the silicides exhibit a maximum figure-of-merit. An increase in hole carrier concentration is expected according to the valence electron counting concept. Although the nearest Mn–Mn and Mn–Si distances increase monotonically with temperature, the nearest Si–Si distance much increases by ∼0.05 Å from 2.439(4) Å at 773 K to 2.493(7) Å at 1173 K. The latter increase is considered to be caused by the introduction of excited electron carriers into the anti-bonding orbital, due to the bipolar diffusion (BD).
    Journal of Alloys and Compounds 12/2014; 616:263–267. DOI:10.1016/j.jallcom.2014.07.106
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    ABSTRACT: The microstructure, martensitic transformation and superelasticity were examined in Fe–30Ni–15Co–10Al–2.5Ti–0.05B polycrystalline alloy sheets. Thermoelastic transformation was obtained in an aged specimen at 550 °C with the γ (FCC) + γ′ (L12) structure. Moreover, it was found that a {0 1 2}〈1 0 0〉 recrystallization texture was formed and that the high fraction of low energy boundaries was increased in a 98.5% cold-rolled specimen. Suppression of brittle precipitation during aging was directly observed at those boundaries, resulting in improvement of ductility, and superelastic strain of over 4% was obtained in the polycrystalline alloy in a tensile test at room temperature.
    Journal of Alloys and Compounds 12/2014; 617:120–123. DOI:10.1016/j.jallcom.2014.07.136


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    Seiryo-machi 2-1, Aoba-ku, 980-8575, Sendai, Miyagi, Japan
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Current science 01/2000; 79:1208-1214.
Journal- Chinese Chemical Society Taipei 01/2007; 54(2). DOI:10.1002/jccs.200700037

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