Microstructure and hydrogen storage properties of melt-spun Mg–Cu–Ni–Y alloys

Microstructural and hydrogen storage properties of three nanocrystalline melt-spun Mg-base alloys (Mg90Cu2.5Ni2.5Y5, Mg85Cu5Ni5Y5 and Mg80Cu5Ni5Y10) have been investigated in view of their application as reversible hydrogen storage materials. The activation procedure and the hydrogen sorption kinetics of these alloys were studied by thermogravimetry at different temperatures in the range from 100 °C to 380 °C. It has been found that these alloys can reach reversible gravimetric hydrogen storage densities of up to 4.8 wt.%-H2. Even at a low temperature of 100 °C, the hydrogenation kinetics of the investigated alloys is rather high in the range of 1.5 wt.%-H2 per hour. In the hydrogenated state, these alloys consist of MgH2, high temperature Mg2NiH4, Mg2NiH0.3, YH2, YH3 as well as MgCu2. The presence of MgCu2 indicates the reaction of Mg2Cu with hydrogen. After repeated hydrogenation/dehydrogenation the preservation of a nanocrystalline grain structure has been confirmed by scanning electron microscopy, energy-filtered and conventional transmission electron microscopy. Additionally, the distribution of hydrogen in the hydrogenated sample was mapped by means of electron energy loss spectroscopy.

Research highlights▶ Melt-spun Mg–Ni–Cu–Y can absorb up to 4.8 wt.%-H2. ▶ Even at 100 °C the hydrogenation kinetics is in the range of 1.5 wt.%-H2 per hour. ▶ nanocrystalline Y-H phases are finely dispersed in hydrogenated Mg–Ni–Cu–Y alloys. ▶ EFTEM imaging is a suitable technique to map the hydrogen distribution in Mg alloys.