Characterization of Hydrogen-Storage Properties and Physical Properties of Zinc Borohydride and Transition Metals-Added Magnesium Hydride
Keywords:hydrogen absorbing materials, ball milling, scanning electron microscopy (SEM), X-ray diffraction, Ni, Zn(BH4)2, Fe, and Ti-added MgH2-based alloy
In this work, 90 wt.% MgH2 + 5 wt.% Ni + 1.7 wt.% Zn(BH4)2 + 1.7 wt.% Ti + 1.7 wt.% Fe samples (named 90MgH2 + 5Ni + 1.7Zn(BH4)2 + 1.7Ti + 1.7Fe) were prepared by milling in a planetary ball mill in a hydrogen atmosphere. The fraction of additives was small (10 wt.%) in order to increase hydriding and dehydriding rates without decreasing the hydrogen storage capacity much. The hydrogen absorption and release properties of the prepared samples were investigated. 90MgH2 + 5Ni + 1.7Zn(BH4)2 + 1.7Ti + 1.7Fe had an effective hydrogen storage capacity of 5 wt.%. The activation of 90MgH2 + 5Ni + 1.7Zn(BH4)2 + 1.7Ti + 1.7Fe was completed after 2 hydriding-dehydriding cycles. At n = 3, the sample absorbed 4.14 wt.% H for 5 min and 5.00 wt.% H for 60 min at 593 K under 12 bar H2. The sample dehydrided at the 3rd hydriding-dehydriding cycle contained Mg and small amounts of β-MgH2, MgO, Mg2Ni, TiH1.924, and Fe. The BET specific surface areas of the sample after milling in a hydrogen atmosphere and after 3 hydriding-dehydriding cycles were 57.9 and 53.2 m2/g, respectively.
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