Gas atomized powders of hydride-forming alloys and their application in rechargeable batteries

Gas atomized powders of LaNi4.5Al0.5 and LaNi2.5Co2.4Al0.1 alloys were prepared and separated into fractions with different particle sizes. The dependence of morphology, oxygen content and crystal structure of the powders on particle size have been analyzed by means of XRD, SEM and EDS. The hydriding and electrochemical properties of different fractions were also evaluated. All fractions had a similar particle morphology and X-ray lattice parameters. EDS of the gas atomized alloys indicated that the surface of the smaller particles was less contaminated by oxygen than course particles. At the same time the fractions with particle sizes below 50 mu m had poor activity both for gas hydrogenation and electrochemical charging. On the DTA curve of the small particles fraction an additional exothermal peak was observed, which may be attributed to a thermal-induced crystallization of the more developed amorphous component of the small particles structure. Gas atomized powders having large particle sizes display hydrogen and electrochemical capacity similar to those of arc-melted alloys.