Improvement of hydrogen storage properties of Mg-Ni alloys by rare-earth addition

A simple and efficient method has been employed to prepare a Mg-rich Mg-Ni-Nd alloy which exhibits a substantially large hydrogen storage capacity with excellent absorption/desorption kinetics at moderate temperatures. This method consists of fully melting raw materials in a sealed steel crucible filled with Ar and subsequent quenching into cold water. It overcomes the difficulties in the melting process of the materials due to large differences in the melting points, specific weights, oxidizability and evaporativity of the raw materials at high temperatures. Initial activation processes, hydriding/dehydriding rates, and presure-composition isotherm (PCT) characteristics of the alloy have been examined and the results are compared with those of a MS-rich Mg-Ni alloy prepared with the same technique. The Mg-Ni-Nd ternary alloy can absorb similar to5.0 mass%H (H/M similar to1.6) at excellent speeds between 573 and 373 K, and can desorb it at moderate speeds between 573 and 473 K. This attractive property of the alloy can be explained by the catalytic action of Nd as well as the unrelaxed multiphase structure formed in the preparation process.