Effect of substitution of Nd for Mg on the hydrogen storage properties of Mg2Ni alloy

Hydrogen storage alloys Mg2-xNdxNi (x=0, 0.1, 0.2, 0.3) were prepared by vacuum induction melting under the protection of high purity helium atmosphere. Their phase structures, morphologies and hydrogen storage properties were intensively studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and pressure composition and temperature (PCT) experiments in the present work. XRD and SEM analysis results show that the Mg-Nd-Ni alloys appear multiphase structures involving Mg2Ni, Nd2Ni7, NdMg12 or Nd5Mg41 and other minor phases. It was found that the alloys exhibited good activation behavior, plateau characteristics, and hydrogen absorption-desorption reversibility and kinetic properties. The substitution of Nd for Mg has improved the hydrogen storage properties Of Mg2Ni evidently and kept relative high hydrogen capacities. The pressure composition isotherms (PCls) of the Mg-Nd-Ni alloys display two plateaus, the lower and narrow ones corresponding to MgH2 formation and the higher and broad ones corresponding to Mg2NiH4 formation. Among the Mg-Nd-Ni alloys, the Mg1.9Nd0.1 Ni alloy has the best hydrogen absorption and desorption kinetics, the highest hydrogen capacity and good reversibility. (C) 2008 Elsevier B.V. All rights reserved.