Berlin 2008 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 41: Poster SYM Hydrogen in Materials: New Developments

MM 41.11: Poster

Thursday, February 28, 2008, 18:00–20:00, Poster B

Formation and Hydrogen Reactivity of Complex Mg-Ni-La-(Co)-H phases — •Angelika Teresiak, Annett Gebert, Valentin Bunea, Jürgen Thomas, Jürgen Eckert, and Ludwig Schultz — Leibniz Institute for Solid State and Material Research Dresden,

Currently, Mg*Ni*RE(La) alloys are of great interest as new electrode materials for Ni-MH batteries. The recently discovered Mg₂NiLaH₇ hydride in the Mg−Ni−La−H quaternary system shows with 2,8 wt% (109 g/l H) a much higher hydrogen content than the well-known commercial LaNi₅H_x- and TiV₂H_x alloys.
In the present study we investigate the formation of the complex hydride Mg₂NiLa(Co)H_7*x by using various process routes, which aim at achieving material with nanocrystalline microstructure. The Mg₂NiLaH₇ forms completely by intensive ball milling of an inductively molten master alloy of Mg₂NiLa under hydrogen for 7.5h. Also, the gradual electrolytic charging of the master alloy using a current density of −1mA/cm² succeeded in forming the hydride. Starting from melt-spun amorphous ribbons, the crystallisation to nanocrystalline Mg₂NiLa and a subsequent hydrogenation under 0.5MPa hydrogen for 26h were performed and monitored by means of in situ high temperature XRD. Furthermore, the influence of Co additives to Mg₂NiLa on the phase formation and hydrogen absorption processes was studied.