Patent ID: 6689193
Filing Date: 2004-02-10
Classification: B22F,C01B,C22C,H01M,Y02E,Y10S

Abstract:
A process for producing a hydrogen absorbing alloy powder, comprising the steps of throwing a starting powder into a ball mill, in which an AE powder comprising at least one alloy element AE selected from the group consisting of Ti, V, Mn, Fe, Ni, Cu and Al, and an Mg powder are weighed so that an alloy composition comprises an amount of AE in a range of 0.1% by weight&lE;AE&lE;20% by weight and the balance of Mg, and subjecting the starting powder to a mechanical alloying in a hydrogen atmosphere to provide a hydrogen absorbing alloy powder comprising an Mg alloy powder;wherein in said mechanical alloying, an acceleration 5 times or more and 20 times or less the acceleration of gravity is generated within a container of the ball mill; wherein said hydrogen absorbing alloy powder has a hydrogenation rate equal to or higher than 50%; wherein said hydrogen absorbing alloy powder is subjected to a dehydrogenating thermal treatment at a temperature t set in a range 80Â° C.&lE;t&lE;450Â° C. and for a time h set in a range of 0.5 hour&lE;h&lE;10 hours either in vacuum or in a hydrogen atmosphere; and wherein said hydrogen absorbing alloy powder after being subjected to the dehydrogenating thermal treatment has a particle size d0 in a range of 0.1 &mgr;m&lE;d0&lE;200 &mgr;m, and includes a plurality of metal crystal grains constituting a matrix and having an average grain size D in a range of 100 nm&lE;D&lE;500 nm.