EFFECT OF ANNEALING ON THE HYDROGEN-STORAGE PROPERTIES OF RAPIDLY QUENCHED AB(5)-TYPE ALLOYS

The effect of annealing on the hydrogen-storage properties of rapidly quenched AB(5)-type alloys is investigated by electrochemical measurem ents and X-ray diffraction. Annealing affects discharge capacity, volt age 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 t emperatures such as 600 and 800 degrees C. These phases are responsibl e for the deterioration in cycle durability. (C) 1998 Elsevier Science S.A.