Mg-Ni-RE nanocrystalline alloys for hydrogen storage

Various nanocrystalline and nano-amorphous Mg-Ni-RE (RE = rare earth or Y) alloys with attractive hydrogen storage properties were prepared by direct quenching of the melt and by crystallization of amorphous precursors. Varying the quenching rate, different microstructures could be obtained by melt-spinning. Having a knowledge of the mechanism and kinetics of the crystallization process, the devitrification of the amorphous samples could be carried out in a controlled way leading to nanocrystalline material. The hydrogenation kinetics and the H-storage capacity of amorphous, partially and completely nanocrystalline alloys were investigated and it was found that they are dependent on the microstructure and on the phase composition of the alloys. Therefore, the crystallization of the amorphous or nano-amorphous alloys was thoroughly studied, applying different experimental methods and approaches. The sequence of the crystal phases formation and the development of the alloys microstructure were investigated. Crystallization kinetics and mechanisms were determined as well. (C) 2003 Elsevier B.V. All rights reserved.