<学位論文要旨>界面に着目した金属-水素系の材料設計 : Mg,Y および Zr 基複合材料の生成と水素化特性  [in Japanese] <Summary of Doctorate>Interfacial Materials Design for Metal-Hydrogen System : formation and hydriding properties of the Mg-, Y- and Zr-based composite materials  [in Japanese]

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Author(s)

    • 折茂 慎一 ORIMO Shinichi
    • 広島大学大学院生物圏科学研究科:(現)日本学術振興会:P. D. 広島大学総合科学部 Graduate school of Biosphere Sciences, Hiroshima University

Abstract

Much attention have been paid to the design of composite materials to achieve some requirements on material properties, especially in researches on structural materials. Thus the interface science and engineering on structural materials have been developed to microscopically understand the interface-phenomena; e. g. diffusion of composed elements, formation of interface phases, or phase transformation at interfaces. For the metal-hydrogen system as functional materials, the design like compaction with binding phases (mainly pure metals such as Cu, Al or Ni) were practically studied so far. Unfortunately, almost all researchers have not focused on the studies about relations between the interface-phenomena and the hydrogen-related reactions. Such relations have been mainly treated only as fundamental problems of "hydrogen trapping" or "hydrogen embrittlement". However, the current studies both on the composite (multi-phase) materials for hydrogen storage and on the processing of the advanced materials with hydrogen indicate that the interface-phenomena dominantly affect their functional and structural properties. The relations between the interface-phenomena and the hydrogen-related reactions should be investigated in details as a new direction of materials design technique; to effectively improve the material properties of the metal-hydrogen system. In the present thesis, therefore, the interfacial materials design focused on the solid-solid interface was applied to the investigation of the metal-hydrogen system. The purposes of the thesis are as follows : I) Study on the composite materials for hydriding reactions; to clarify the interface-phenomena during heat treatment, and moreover, to investigate the effects of their interface-phenomena on "kinetical and thermodynamical properties for hydride formation", "interdiffusion of hydrogen atoms" and "practical durability for cyclic hydriding reactions". II) Study on the hydrogen induced interface-phenomena; to clarify the mechanism of "hydrogen enhanced powder reaction" and "reactive mechanical grinding" under hydrogen atmospheres, and moreover, to investigate the hydriding properties of the composite particles synthesized by their induced phenomena. Through the characterizations of the composite materials relating to the Mg-, Y- and Zr-based intermetallic compounds, the interfacial materials design for/by the hydrogen-related reactions was investigated under the above purposes. The results obtained are summarized as follows : In chapter 3,the composite materials (Zr-based compound/Mg), composed of ZrCr_2 or ZrFe_<1.4>Cr_<0.6> as a host hydriding phase and elemental Mg as a chemical binding phase, were prepared under various heat treatment conditions. The formation/reduction of host-Mg interface oxides, the diffusion of composed elements across the host-Mg interface, and their effects on the hydriding properties of the host phases were investigated. Microscopic observations indicate that the heat treatment at 773K not only promotes the reduction of host phase oxides at the interface owing to the MgO formation, but also helps to form the diffusion-bonded interfaces. Because of these interface-phenomena, the host phases in the composite materials promptly react with gas phase hydrogen without any ativation treatments. Furthermore, they exhibit high durabilities for cyclic hydriding reactions. The mechanism for improving the hydriding properties of the host phases can be also applied for the Ti-based multi-component system. The hydrogen dissolved phases of ZrCr_<-0.6>Fe_<1.4> in the composite materials are continuously unstabilized with increasing the heat treatment temperatures. Next in chapter 4,the Cu-doped composite material (ZrCr_<1.8>Cu_<0.3>/Mg) was prepared to study both the formation of the interface Mg_2Cu phase and its effect on the low-temperature hydriding of the Mg phase. As a result of the diffusion of Cu mainly in grain boundaries

Journal

  • Memoirs of the Faculty of Integrated Arts and Sciences, Hiroshima University. IV, Science reports : studies of fundamental and environmental sciences

    Memoirs of the Faculty of Integrated Arts and Sciences, Hiroshima University. IV, Science reports : studies of fundamental and environmental sciences (21), 259-262, 1995-12-28

    Hiroshima University

Codes

  • NII Article ID (NAID)
    110000482251
  • NII NACSIS-CAT ID (NCID)
    AN10435936
  • Text Lang
    JPN
  • Article Type
    departmental bulletin paper
  • ISSN
    1340-8364
  • Data Source
    NII-ELS  IR 
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