ABSTRACT
LaNi5 is the most studied compound as a hydrogen storage material. In the LaNi5-related intermetallic compounds, the thermodynamic and electrochemical properties were found to be strongly dependent on the nature of the substituted element, its content, and its microstructure. Compared to the microcrystalline alloy prepared by arcor induction melting, mechanically alloyed LaNi5 is easier to activate and has faster first hydrogenation kinetics. Mechanical alloying (MA) drastically reduces the hydrogen storage capacity of LaNi5 but it can be recovered by annealing. During the MA process, originally sharp diffraction lines of La and Ni gradually become broader and their intensity decreases with milling time. The cleanliness of the surface of nanocrystalline LaNi5-type alloys was studied by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy. The XPS intensity of the MA nanocrystalline alloy is considerably reduced compared to that measured for a thin film. The high gravimetric and volumetric storage capacities of LaNi5 type metal hydrides make them ideal hydrogen carrier.
