A comparison study of hydrogen storage performances of SmMg11Ni alloys prepared by melt spinning and ball milling

The melt spinning (MS) and ball milling (BM) technologies are thought to be efficient to prepare nanostructured Mg and Mg-based alloys for improving their hydrogen storage performances. In this paper, two technologies, viz. melt spinning and ball milling, were employed to fabricate the SmMg₁₁Ni alloy. The structure and hydrogen storage performance of these two kinds of alloys were researched in detail. The results reveal that the as-spun and milled alloys both contain nanocrystalline and amorphous structures. By means of the measurement of PCT curves, the thermodynamic parameters of the alloys prepared by MS and BM are ΔH_MS(des) = 82.51 kJ/mol and ΔH_BM(des) = 81.68 kJ/mol, respectively, viz. ΔH_MS(des) > ΔH_BM(des). The as-milled alloy shows a larger hydrogen absorption capacity as compared with the as-spun one. The as-milled alloy exhibits lower onset hydrogen desorption temperature than the as-spun one. As to the as-milled and spun alloys, the onset hydrogen desorption temperatures are 557.6 and 565.3 K, respectively. Additionally, the as-milled alloy shows a superior hydrogen desorption property than the as-spun one. On the basis of time that required by desorbing hydrogen of 3 wt% H₂, the as-milled alloy needs 1488, 574, 390 and 192 s corresponding to hydrogen desorption temperatures 593, 613, 633 and 653 K, while the as-spun alloy needs 3600, 1020, 778 and 306 s corresponding to the same temperatures. The dehydrogenation activation energies of the as-milled and spun alloys are 100.31 and 105.56 kJ/mol, respectively, the difference of which is responsible for the much faster dehydriding rate of the as-milled alloy.