Thermal analysis investigation of hydriding properties of nanocrystalline Mg-Ni- and Mg-Fe-based alloys prepared by high-energy ball milling

The hydrogen loading characteristics of nanocrystalline Mg, Mg-Ni (Ni from 0.1 to 10 at.%), and Mg-Fe (Fe from 1 to 10 at.%) alloys in 3 MPa H-2 were examined using high pressure differential scanning calorimetry and thermogravimetric analysis. All samples showed rapid uptake of hydrogen. A decrease in the onset temperature for hydrogen absorption was observed with increasing Ni and Fe alloy content, but the thermal signatures obtained suggested that only Mg was involved in the hydriding reaction; i,e., no clear evidence was found for the intermetallic hydrides Mg2NiH4 and Mg2FeH6. Hydrogen loading capacity decreased with temperature cycling, and this was attributed to a sintering process in the alloy, leading to a reduction in the specific surface available for hydrogen absorption.