Improved activation and hydrogen storage properties of a Mg 85Ni 15 melt-spun alloy via surface treatment with NH 4+ solution

Abstract

An amorphous Mg 85Ni 15 melt-spun hydrogen storage alloy, processed by submersion in an aqueous solution of NH 4 +, is able to absorb nearly 5 mass% 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 NH 4 +-treated material compared to the as-spun material; and the kinetics of subsequent absorption/desorption cycles at 573 K are dramatically improved. The material activated at 473 K exhibits a decrease in hydride decomposition temperature by 30 K, observed via DSC and TPD experiments, compared to a sample activated at 573 K. The NH 4 +-treatment of a glassy alloy presented here provides a practical alternative to ball milling for forming a nanocrystalline material and facilitating activation, requiring much less time and a more commercially scalable option.