An investigation of long-term degradation of Mm Ni₅-based hydrogen-absorbing alloys by water vapor

The effects of long-term absorption-desorption testing with hydrogen containing water vapor and of reactivation on the hydrogen absorption-desorption properties of hydrogen-absorbing alloys were experimentally investigated. With absorption times, the hydrogen-absorbing alloys degraded in the first several cycles. In subsequent cycles, the degraded alloys recovered and degraded again due to the pulverization. On reactivation with pure hydrogen, the hydrogen absorbing-desorbing capacity and rate of hydrogen absorption-desorption recovered, but the hydrogen-absorbing capacity did not recover completely to that before degradation, due to the extrinsic degradation.