Method for preparing hydrogen storage alloy

Abstract

A process for preparing a hydrogen storage alloy having as the main phase a body-centered cubic structure phase capable of absorbing, storing and releasing hydrogen, which comprises steps: a melting step of melting and homogenizing an alloy having a prescribed element ratio; a heat treatment step of retaining the homogenized alloy at a temperature (T) just under the melting point (Tm) of the alloy for a prescribed period of time; and a quenching step of rapidly cooling the heat-treated alloy.

1 . A process for producing a hydrogen storage alloy having as its main phase a body-centered cubic structure phase capable of absorbing, storing and releasing hydrogen, which comprises steps: 
 (a) a melting step of melting a starting alloy brought to a predetermined element ratio to form a homogeneous heat,    (b) a heat-treatment step of retaining the homogenized alloy at a temperature equal to or just lower than the melting point of the alloy for a predetermined period of time; and    (c) a quenching step of rapidly cooling the heat-treated alloy.    
     
     
         2 . The process according to  claim 1  wherein the ratio of the heat-treating process temperature (T) to the alloy melting point (Tm), T/Tm, is within a temperature range of 0.8≦T/Tm≦1.0, in the heat-treatment step.  
     
     
         3 . The process according to  claim 1  or  2  wherein the heat treatment step is conducted for a retaining period of time ranging from 1 min to 1 hr.  
     
     
         4 . The process according to any of  claims 1  to  3  wherein the starting alloy to be molten to form a homogeneous heat has a composition represented by the general composition formula:  
       Ti (100-a-0 4b) Cr (a-0 6b) M b    
       wherein M is V; and  
       20 ≦a  (at %)≦80 and 0 ≦b  (at %)≦10.  
     
     
         5 . The process according to any of  claims 1  to  3  wherein the starting alloy to be molten to form a homogeneous heat has a composition represented by the general composition formula:  
       Ti (100-a-0.4b) Cr (a-0.6b) M b    
       wherein M is at least one element of Mo and W; and  
       20 ≦a  (at %)≦80 and 0 ≦b  (at %)<5.  
     
     
         6 . The process according to any of  claims 1  to  3  wherein the starting alloy to be molten to form a homogeneous heat has a composition represented by the general composition formula:  
       Ti (100-a-0 4b) Cr (a-0 6b) V (b-c) M c    
       wherein 20≦a (at %)≦80, 0≦b (at %)≦10, and 
 0≦c (at %)<5; and  
 M is at least one element of Mo and W.