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 a nd EDS. The hydriding and electrochemical properties of different frac tions were also evaluated. All fractions had a similar particle morpho logy and X-ray lattice parameters. EDS of the gas atomized alloys indi cated that the surface of the smaller particles was less contaminated by oxygen than course particles. At the same time the fractions with p article sizes below 50 mu m had poor activity both for gas hydrogenati on and electrochemical charging. On the DTA curve of the small particl es fraction an additional exothermal peak was observed, which may be a ttributed to a thermal-induced crystallization of the more developed a morphous component of the small particles structure. Gas atomized powd ers having large particle sizes display hydrogen and electrochemical c apacity similar to those of arc-melted alloys.