Hydriding properties of a nano-/amorphous-structured Mg-Ni-H system

The alloys Mg-x at.% Ni (x=33, 38, 43 and 50) with nanometer-scale structures were successively synthesized by mechanical grinding of Mg₂Ni mixed with various amounts of additional Ni. The total hydrogen contents in these alloys increases from 1.7 mass% for x=33 to 2.2 mass% for x=43 and 50, while the dehydriding temperatures gradually lower from 440 K to 373 K with increasing of the Ni amounts. The value of the total hydrogen content in each alloy is reasonably explained by taking into account the hydrogen contents of the following three regions; the intra-grain region of nanostructured Mg₂Ni, its inter-grain region, and the amorphous MgNi region. The maximum hydrogen content in the amorphous MgNi region, 2.2 mass%, might imply a specific interatomic occupation of hydrogen atoms in this region.