An amorphous Mg85Ni15 melt-spun hydrogen storage alloy, processed by submersion in an aqueous solution of NH4+, is able to absorb >5 wt. % hydrogen at 473 K during the first hydrogenation cycle. The nanocrystalline microstructure formed during devitrification of the metallic glass is preserved by the lower required activation temperature of the NH4+-treated material; and the kinetics of subsequent absorption/desorption cycles at 573 K are dramatically improved, compared to the as-spun material. DSC experiments and thermodynamic calculations demonstrate that the decreased crystallite size of the 473 K activated material lowers the hydride decomposition temperature by 20 K to 50 K, in contrast to a sample activated at 573 K. The NH4+-treatment of a glassy alloy presented here provides a more practical approach to both forming a nanocrystalline material, and facilitating activation, compared to ball milling; requiring much less time and a more commercially scalable option.
Citation: Journal of Alloys and Compounds
Pub Type: Journals
Mg-based alloy, metallic glass, hydrogen storage, metal hydride, nanocrystalline