SURFACE AND METALLOGRAPHIC MICROSTRUCTURE OF THE LA-ADDED AB(2) COMPOUND (TI, ZR)(MN, CR, NI)(2)

The surface properties and metallographic microstructures of AB(2)-hyd riding compounds Ti0.5-x/2Zr0.5-x/2LaxMn0.8Cr0.8Ni0.4 (x = 0.0-0.1) we re investigated for the purpose of understanding dramatically improved hydriding properties by small amounts of La addition. The results sug gest that the discrete La-Ni particles decorated on the crushed powder surfaces serve as both catalytic sites, such as a window? during init ial activation and a protective coating against surface contamination from long-time air/water exposure. Simultaneously, these La-Ni particl es could protect the AB(2) alloy surface against the normally damaging F-treatment by forming a highly reactive LaF3 compound to further acc elerate the hydrogen absorption as it did in the LaNi4.7Al0.3 alloy.