Effect of annealing on the hydrogen-storage properties of rapidly quenched AB5-type alloys

The effect of annealing on the hydrogen-storage properties of rapidly quenched AB(5)-type alloys is investigated by electrochemical measurements and X-ray diffraction. Annealing affects discharge capacity, voltage and cycle life. Annealing at an appropriate temperature can give a promising alloy with large capacity, high discharge voltage and long cycle life. Annealing at too high a temperature, such as 800 degrees C, results in the largest discharge capacity but the worst cycle life. Annealing can also flatten the discharge plateau regions. The striking difference in the phase structure between as-quenched and as-annealed alloys is that new phases occur as the product of annealing at high temperatures such as 600 and 800 degrees C. These phases are responsible for the deterioration in cycle durability. (C) 1998 Elsevier Science S.A.