Metal alloys forming passivating conductive oxides for durable electrical contact surfaces

Abstract

A metal alloy which when oxidized forms a highly conductive surface oxide layer. Alloy compositions such as, but not limited to, Ti—Nb, Ti—Ta, La—Sr—Cr, and La—Sr—Co are known to form oxide passivation layers which are highly conductive. Such alloys are useful in electrical contact apparatus. An electrical contact element formed of the alloy has a contact surface which when oxidized forms a highly conductive surface layer, thus maintaining electrical conductivity and continuity through the element. The oxide layer may be formed in situ after assembly of the electrical contact or may be provided in an oxidative step during manufacture. The electrical contact may be formed entirely of one or more of such alloys; or may be formed of an inexpensive substrate base metal, such as steel, having one or more of the alloys coated thereupon; or may be formed of a mixture of the base metal and the alloy.

What is claimed is:  
     
         1 . A metal alloy comprising at least two metal elements, said alloy being capable of forming a surface metal oxide layer that is conductive.  
     
     
         2 . An alloy in accordance with  claim 1  wherein said surface metal oxide layer exhibits an electrical surface resistance equal to about 0.0015 Ωcm 2  or less.  
     
     
         3 . An alloy in accordance with  claim 1  selected from the group of alloys consisting of chemical elements having the symbols Y—Ba—Cu, La—Sr—Co, La—Sr—Cr, La—Sr—V, La—Ca—Mn, La—Sr—Mn, La—Nd—Ni, Ti—Ta, Ti—Nb, Ti—V, Ti—W, Ti—Mo, Ti—Zr—Ta, Ti—Zr—Nb, Cr—Ta, Cr—Nb, Cr—Ti, Cr—Zr, Sr—V, Cu—Ti, Cu—Fe, Cu—Mn, Cu—Al, Cu—Si, Sn—Sb, Sn—In, Ni—Li, and combinations thereof.  
     
     
         4 . An alloy in accordance with  claim 1  wherein a first metal element is a main metal and an additional metal element is a dopant.  
     
     
         5 . An alloy in accordance with  claim 4  wherein said dopant is present in said alloy in a range between about 1 atom percent and about 50 atom percent.  
     
     
         6 . An alloy in accordance with  claim 4  wherein said dopant is present in said alloy between about 1 atom percent and about 10 atom percent.  
     
     
         7 . An alloy in accordance with  claim 4  wherein said dopant is present in said alloy in a range between about 1 atom percent and about 3 atom percent.  
     
     
         8 . An alloy in accordance with  claim 4  wherein said main metal is titanium and said dopant is selected from the group consisting of niobium and tantalum.  
     
     
         9 . An alloy in accordance with  claim 4  wherein said main metal is copper and said dopant is selected from the group consisting of aluminum, silicon, iron, manganese, vanadium, and titanium.  
     
     
         10 . An alloy in accordance with  claim 4  wherein the radius of said dopant metal atom differs from the radius of said main metal atom by less than about twenty percent.  
     
     
         11 . An alloy in accordance with  claim 4  wherein the radius of a cation of said dopant metal differs from the radius of a cation of said main metal by less than about twenty percent.  
     
     
         12 . An alloy in accordance with  claim 11  wherein said dopant cation is in a higher valence state than said main metal cation.  
     
     
         13 . An alloy in accordance with  claim 11  wherein said dopant cation is in a lower valence state than said main metal cation.  
     
     
         14 . An alloy in accordance with  claim 4  wherein said dopant metal and said main metal are present as an atomic solid solution.  
     
     
         15 . An alloy in accordance with  claim 4  wherein oxide compounds of said dopant metal and oxide compounds of said main metal are present as a solid solution of said compounds.  
     
     
         16 . An electrical contact for use in an electromechanical apparatus, comprising a metal alloy of at least two metal elements, said alloy being capable of forming surface metal oxide layers that are conductive.  
     
     
         17 . A contact in accordance with  claim 16  wherein said entire contact is formed of said metal alloy.  
     
     
         18 . An electrical contact in accordance with  claim 16  comprising: 
 a) a conductive core portion formed of base metal; and  
 b) an outer portion formed of said metal alloy and having said surface metal oxide layers that are conductive.  
 
     
     
         19 . An electromechanical apparatus, comprising an electrical contact including a metal alloy of at least two metal elements, said alloy being capable of forming a surface metal oxide layer that is conductive.  
     
     
         20 . An apparatus in accordance with  claim 15  wherein said apparatus includes a fuel cell.  
     
     
         21 . An apparatus in accordance with  claim 20  wherein said fuel cell is a proton exchange membrane fuel cell.  
     
     
         22 . An apparatus in accordance with  claim 20  wherein said fuel cell is a solid-oxide fuel cell.  
     
     
         23 . An apparatus in accordance with  claim 19  wherein said electrical contact is an electrical terminal.  
     
     
         24 . An apparatus in accordance with  claim 19  wherein said electrical contact is an interconnect for an electronic system.