Research on Hydrogen-Storage Amorphous and Nano-structured Alloys

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The objective of this research is to find novel hydrogen-storage alloys with amorphous as well as nanocrystalline structures, and to investigate their hydrogen storage properties. In addition, effects of hydrogenation on the structural change or stability of metallic multilayrs have also been studied.1. Hydrogen absorption in amorphous alloys Binary and ternary alloys containing transition metals and/or rare earths have been investigated. Alloys of Nd-Fe, Nd-Fe-B and Nd-Co-B systems with 5-30 at.%Nd have been studied in detail, and relationships between the hydrogen-storage ability and atomistic structures of the amorphous alloys have been revealed. Furthermore, amorphous alloys of Zr-Ni-V and Zr-Ni-Nballoys with 25-35 aat.%Zr and 5-25 at.%V and Nb have been studied. We succeeded in producing several amorphous alloys with good hydrogen-storage ability and structural stability, but their hydrogen absorbing and desorbing kinetics below 373K were not fast enough in comparison with those o … More f conventional intermetallic compounds and deserve further investigation.2. Hydrogen absorption in nanocrystalline alloys Alloys of Mg-Ni, Ng-Ni-La and Mg-Ni-Nd systems have been mainly studied. Nanocrystalline structures of these alloys with grain sizes of 50-100 nm have been obtained by annealing melt-spun amorphous alloys at temperatures just above the respective crystallization temperatures. These nanocrystalline alloys exhibit faster hydrogen absorbing kinetics and better PCT characteristics than the corresponding as-cast alloys with coarse grains. With further improvements, they will be used as practical hydrogen storage materials operative at 473-573K.3. Structure stabilization of metallic multilayrs by hydrogenation In the course of study of hydrogen absorption in metallic multilayrs such as Pd/Ti, Ni/Ti and Fe/Ti, we found that the multilayr structures are thermally stabilized by hydrogenation up to about 723K.Without hydrogenation, they should undergo interlayr mixing to form homogeneous equilibrium intermetallic phases. This stabilization is attributed to the transformation of Ti layrs into TiH_2, and may be applicable to multilayr technologies. Less