Hydrogen storage alloy material and process for producing the same

Abstract

Disclosed is a hydrogen storage alloy material which is prepared by subjecting an amorphous alloy to a heat treatment in air or an oxygen atmosphere. The amorphous alloy has a composition, in atomic %, expressed by the following formula: Zr 100-a-b Pd a M b (wherein 15≦a≦40, 0<b≦10, and M is at least one metal selected from the group consisting of Pt, Au, Fe, Co and Ni). The Pd, the metal M and one or more compounds thereof are dispersed in a parent phase of ZrO 2 in the form of ultrafine particles. This alloy material exhibits a hydrogen storage amount of 2.5 weight % or more in a weight ratio relative to Pd contained in the material, and suited to a hydrogen storage/transportation medium. The alloy material can be produced by preparing a melt of a master alloy formed through a melting process, rapidly solidifying the melt at a cooling rate of 10 4 K/s or more to form the above amorphous alloy, and subjecting the amorphous alloy to an oxidizing heat treatment in air or an oxygen atmosphere at 250 to 350° C. to selectively oxidizing the alloy element of Zr so as to allow the hydrogen storage metal of Pd or a Pd compound to be dispersed in a parent phase of ZrO 2 in the form of nanoparticle-size ultrafine particles.

1 . A hydrogen storage alloy material prepared by subjecting an amorphous alloy to a heat treatment in air or an oxygen atmosphere, said amorphous alloy having a composition, in atomic %, expressed by the following formula: Zr 100-a-b Pd a M b  (wherein 15≦a≦40, 0<b≦10, and M is at least one metal selected from the group consisting of Pt, Au, Fe, Co and Ni), wherein said hydrogen storage alloy material has a structure where said Pd, said metal M and one or more compounds thereof are dispersed in a parent phase of ZrO 2  in the form of ultrafine particles.  
   
   
       2 . The hydrogen storage alloy material as defined in  claim 1 , which exhibits a hydrogen storage amount of 2.5 weight % or more in a weight ratio relative to Pd contained in said hydrogen storage alloy material.  
   
   
       3 . A hydrogen storage/transportation container comprising a hydrogen storage/transportation medium consisting of the hydrogen storage alloy material as defined in  claim 1  or  2 .  
   
   
       4 . A method for producing the hydrogen storage alloy material as defined in  claim 1 , comprising: 
 preparing a melt of a master alloy formed through a melting process;    rapidly solidifying said melt at a cooling rate of 10 4  K/s or more to form said amorphous alloy; and    subjecting said amorphous alloy to an oxidizing heat treatment in air or an oxygen atmosphere at 250 to 350° C. to selectively oxidize said alloy element Zr so as to allow said Pd, said metal M and one or more compounds thereof to be dispersed in a parent phase of ZrO 2  in the form of nanoparticle-size ultrafine particles.