Amorphous-versus big cube- Zr2Ni for improving the kinetics of hydrogenation/dehydrogenation behaviors for MgH2 powders

Whereas all catalytic materials used to improve the behaviors of hydrogenation/dehydrogenation kinetics for MgH2 have long-range order structure, the present work proposes two different types of structure; i.e. short range- and medium range- order. For the purpose of the present study, ultrafine powders of amorphous- and big cube-Zr2Ni phases were prepared by ball milling small bulk pieces of tetragonal-Zr2Ni alloy prepared by arc melting technique. Small volume fraction (10 wt. %) of amorphous and big-cube powders obtained after ball milling for 100 and 150 h, respectively were individually mixed with as-synthesized MgH2 powders and then ball milled for 50 h. The results have shown that nanocomposite MgH2/10 wt.% metallic glassy Zr2Ni powders had high density of hydrogen (similar to 6 wt.%) and possessed fast kinetics of hydrogen uptake/release at 250 degrees C within 1.15 and 2.5 min, respectively. Whereas, MgH2/10 wt.% o f big cube Zr2Ni nanocomposite showed moderate improvement on hydrogenation (1.8 min)/dehydrogenation (7 min) kinetics due to the heterogeneous distribution of their particles onto the MgH2 powders. (C) 2017 Elsevier B.V. All rights reserved.