Development of novel hydrogen absorption alloys and analysis of hydrogenation behavior by hydrogen micro-imaging system

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The purposes of the research were to investigate and improve the hydrogenation property of hydrogen absorption alloys by analyzing the hydrogen behavior in them using hydrogen micro-imaging system.For the Ti-Cr specimen with two-phase structure of BCC phase and TiCr2 Laves phase, hydrogen distribution is observed by tritium radioluminography and silver decoration method. The hydrogen diffusion coefficients at room temperature have been successfully determined by analyzing the tritium depth in the specimens. This result shows that the hydrogen diffusion in the Laves phase is slower than that in the BCC phase. The developed Ti-Cr alloy showed 3.5 mass% of hydrogen capacity at room temperature.For the Mg-Ni eutectic alloy specimen with two-phase structure of Mg phase and Mg2Ni phase, the relation between hydrogenation property and eutectic structure is examined by the PCT measurement. The specimen showed the hydrogen capacity of 6.3 mass% at 400℃. The hydrogenation behavior depends on the morphology of the eutectic structure, that is, the coarsening of the eutectic structure causes the acceleration of hydrogenation kinetics. Nickel coating by hybridization treatment is found to improve the hydrogenation kinetics drastically for both the pure Mg and Mg-Ni eutectic alloy.