Microstructure and tailoring hydrogenation performance of Y-doped Mg ₂Ni alloys

In this work, the microstructure and the hydrogenation properties of melt-spun Mg₆₇Ni_33-xY_x alloys are studied with the purpose to investigate the influence of Y doping and rapid solidification on hydrogenation performance of Mg₂Ni. Mg₆₇Ni _33-xY_x (x = 0, 1, 3, 6) alloys are firstly prepared in an electric resistance furnace under the protection of a covering reagent. Then, the as-cast alloys are re-melted and spun on a rotating copper roller. The phase compositions and microstructures of as-cast and melt-spun alloys are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) with an energy dispersive spectrometer (EDS). The hydrogen activation properties and absorption/desorption kinetics of melt-spun Mg₆₇Ni _33-xY_x (x = 0, 1, 3, 6) ribbons are evaluated using an automatic Sieverts apparatus. The melt-spun Mg₆₇Ni₃₂Y alloy preserves high hydrogen absorption capacity and kinetics and absorbs 96% of the maximum capacity (3.79 wt. %) within 8 min. The lattice distortion caused by Y doping and the shrinkage porosity by melt-spun not only raise the hydrogen absorption/desorption rate, but significantly improve the hydrogen storage capacity of Mg₆₇Ni_33-xY_x (x = 0, 1, 3, 6) alloys. The activation and hydrogen absorption/desorption mechanisms are also discussed based on a nucleation and growth theory.