Ca-Mm-Ni based hydrogen storage alloys

Abstract

New alloys of the AB 5 type are disclosed which are of the formula: (Ca x M 1-x ) t (Ni 1-y T y ) 5 where M is one or several metals selected from the group consisting of misch metal (Mm) and other rare earth metals T is one or several semi-metals such as Si, Ge and Ga; 0<x≦1; 0<y≦0.5 and 0.8≦t≦1.2. Also disclosed is a process for preparing these new alloys and their use for hydrogen storage.

1 . A Ca-Mm-Ni based alloy of the AB 5  type, said alloy being of the formula:  
       (Ca x M 1-x ) t (Ni 1-y T y ) 5    (I)  where M is selected from the group consisting of: any mischmetal, any rare earth metal, and an homogeneous or an inhomogeneous combination of any of: (i) at least two mischmetals, (ii) at least two rare earth metals, and (iii) at least one mischmetal and at least one rare earth metal;    where T is selected from the group consisting of: metalloids, and an homogeneous or an inhomogeneous combination of at least two metalloids;    where 0<x≦1;    where 0<y≦0.5; and    where 0.8≦t≦1.2.    
     
     
         2 . The alloy of  claim 1 , wherein, in the formula I:  
       0.4≦x≦1; 0<y≦0.3 ; and 0.85t≦t≦1.2.  
     
     
         3 . The alloy of  claim 1 , wherein: 
 M is a mischmetal; and    T is any of Si, Ge and Ga.    
     
     
         4 . The alloy of  claim 1 , wherein: 
 M is a mischmetal; and    the metalloid of T is any of Si, Ge, and Ga.    
     
     
         5 . A method for storing hydrogen comprising using a Ca-Mm-Ni based alloy of the AB 5  type to store hydrogen, where the alloy has the formula: 
 (Ca x M 1-x ) t (Ni 1-y T y ) 5  (I), where M is selected from the group consisting of: any mischmetal, any rare earth metal and an homogeneous or an inhomogeneous combination of any of: (i) at least two mischmetals, (ii) at least two rare earth metals, and (iii) at least one mischmetal and at least one rare earth metal; where T is selected from the group consisting of: metalloids, and an homogeneous or an inhomogeneous combination of at least two metalloids; where 0<x≦1; where 0<y≦0.5; and where 0.8≦t≦1.2.    
     
     
         6 . A method of preparation of an alloy having the formula:  
       (Ca x M 1-x ) t (Ni 1-y T y ) 5    (I)  where M is selected from the group consisting of: any mischmetal, any rare earth metal, and an homogeneous or an inhomogeneous combination of any of: (i) at least two mischmetals, (ii) at least two rare earth metals, and (iii) at least one mischmetal and at least one rare earth metal;    where T is selected from the group consisting of: metalloids, and an homogeneous or an inhomogeneous combination of at least two metalloids;    where 0<x≦1;    where 0<y≦0.5; and    where 0.8≦t≦1.2;    wherein the method of preparation comprises: 
 a) preparing a powder by milling a mixture of elemental powders and/or pre-alloyed substances of the elemental ingredients of the alloy to be prepared in adequate proportions to obtain the required alloy; and  
 b) annealing and/or sintering the so prepared powder at elevated temperatures in a crucible for a short period of time in an inert or reactive atmosphere.  
   
     
     
         7 . The method of  claim 6 , wherein the milling in step (a) consists of a ball milling or mechanical alloying.  
     
     
         8 . The method of  claim 7 , wherein the milling in step (a) is carried out in the presence of at least one anti-sticking agent.  
     
     
         9 . The method of  claim 6 , wherein the annealing and/or sintering in step (b) is carried out at a temperature higher than 600° C. but not higher than 1100° C. in a steel crucible.  
     
     
         10 . The alloy of  claim 2  wherein: 
 M is a mischmetal; and  
 T is any of Si, Ge and Ga.  
 
     
     
         11 . The alloy of  claim 2  wherein: 
 M is a mischmetal; and  
 the metalloid of T is any of Si, Ge, and Ga.  
 
     
     
         12 . The method of  claim 5 , wherein, in the formula I:  
       0.4≦x≦1; 0<y≦0.3; and 0.85≦t≦1.2.  
     
     
         13 . The method of  claim 5  wherein: 
 M is a mischmetal; and  
 T is any of Si, Ge and Ga.  
 
     
     
         14 . The method of  claim 5  wherein: 
 M is a mischmetal; and  
 the metalloid of T is any of Si, Ge, and Ga.  
 
     
     
         15 . The method of  claim 12  wherein: 
 M is a mischmetal; and  
 T is any of Si, Ge and Ga.  
 
     
     
         16 . The method of  claim 12  wherein: 
 M is a mischmetal; and  
 the metalloid of T is any of Si, Ge, and Ga.  
 
     
     
         17 . The method of  claim 7  wherein the annealing and/or sintering in step (b) is carried out at a temperature higher than 600° C. but not higher than 1100° C. in a steel crucible.  
     
     
         18 . The method of  claim 8  wherein the annealing and/or sintering in step (b) is carried out at a temperature higher than 600° C. but not higher than 1100° C. in a steel crucible.