Metal alloys for forming conductive oxide coatings for electrical contacts

Abstract

Described is a metal alloy comprising at least two metal elements which are not precious metals, said alloy being capable of forming a surface metal oxide layer that is conductive having a contact resistivity of 100 Ωcm or less after the alloy has been subjected to 125° C. for 1008 hours. Also described is a process of preparing a metal alloy providing two metal elements which are not precious metals and oxidizing the metal alloy to produce a surface metal oxide layer that is conductive having a contact resistivity of 100 Ω-cm or less after the alloy has been subjected to 125° C. for 1008 hours.

1 . A metal alloy comprising at least two metal elements which are not precious metals, said alloy being capable of forming a surface metal oxide layer that is conductive having a contact resistivity of 100 Ωcm or less after the alloy has been subjected to 125° C. for 1008 hours.  
     
     
         2 . The metal alloy of  claim 1  having at least two metals from one or more of Periodic Table of Elements groups IA, IB, IIA, IIB, IIIA, IIIB, IVA, IVB, VA, VB, VIA, VIB, VIIA, VIIB.  
     
     
         3 . The metal alloy in accordance with  claim 2  selected from the group of alloys consisting of chemical elements having the symbols Cu—Ge, Cu—Sn, Cu—Ti, Cu—Fe, Cu—Sb, Cu—Ti—Ta, Cu—Ti—Nb, Cu—Sn—Sb, Sn—Sb, Sn—Ta, Sn—Nb, Ni—La, Ni—Li, Y—Ba—Cu, La—Sr—Co, La—Sr—Cr, La—Sr—V, La—Ca—Mn, La—Sr—Mn, La—Ba—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—Si, Cu—Al, Cu—In, and combinations thereof.  
     
     
         4 . The metal alloy in accordance with  claim 1  wherein a first element is a base metal and at least a second element is a dopant wherein said metal alloy has a resistivity less than or equal to 100 Ω-cm or less when exposed to an oxidative environment.  
     
     
         5 . The metal alloy in accordance with  claim 4  wherein said second element is uniformly dispersed in said first element during a melt state.  
     
     
         6 . The metal alloy in accordance with  claim 4  wherein said second element is a higher valence state than said first element.  
     
     
         7 . The metal alloy in accordance with  claim 4  wherein the anions of said second element is in a lower valence state than the anions of said first element.  
     
     
         8 . The metal alloy in accordance with  claim 4  wherein the ionic radii of said second element is substantially similar to the ionic radii of said first element.  
     
     
         9 . The metal alloy in accordance with  claim 3  wherein the Gibbs free energy of oxide formation of the metal of said second element is substantially similar to the Gibbs free energy of the oxide of said first element.  
     
     
         10 . The metal alloy in accordance with  claim 4  wherein said first element is Cu and said second element is selected from the group consisting of Ge and Sn.  
     
     
         11 . The metal alloy in accordance with  claim 1  wherein a first element is a base metal and a second element is a dopant, wherein said first and second elements phase separate in their oxide state and form conductive oxides.  
     
     
         12 . The metal alloy in accordance with  claim 1  wherein a first element is a base metal, a second element is a dopant and a third element is a dopant, wherein said first, second and third elements phase separate in their oxide state and form conductive oxides.  
     
     
         13 . The metal alloy in accordance with  claim 11  wherein said first, second and third elements phase separate into a conductive oxide surface layer.  
     
     
         14 . The metal alloy in accordance with  claim 12  wherein said first, second and third elements phase separate into a network of conductive veins.  
     
     
         15 . An electrical contact for use in an electromechanical apparatus comprising at least two metal elements which are not precious metals, said alloy being capable of forming a surface metal oxide layer that is conductive having a resistivity less than or equal to 100 Ω-cm or less after the alloy has been subjected to 125° C. for 1008 hours.  
     
     
         16 . The electrical contact of  claim 15  having at least two metals from one or more of Periodic Table of Elements groups IA, IB, IIA, IIB, IIIA, IIIB, IVA, IVB, VA, VB, VIA, VIB, VIIA, VIIB.  
     
     
         17 . The electrical contact in accordance with  claim 15  wherein said metal alloy is selected from the group of alloys consisting of chemical elements having the symbols Cu—Ge, Cu—Sn, Cu—Ti, Cu—Fe, Cu—Sb, Cu—Ti—Ta, Cu—Ti—Nb, Cu—Sn—Sb, Sn—Sb, Sn—Ta, Sn—Nb, Ni—La, Ni—Li, Y—Ba—Cu, La—Sr—Co, La—Sr—Cr, La—Sr—V, La—Ca—Mn, La—Sr—Mn, La—Ba—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—Si, Cu—Al, Cu—In, and combinations thereof.  
     
     
         18 . The electrical contact in accordance with  claim 15  wherein a first element is a base metal and at least a second element is a dopant wherein said metal alloy has a resistivity less than or equal to 100 Ω-cm when exposed to an oxidative environment.  
     
     
         19 . The electrical contact in accordance with  claim 15  wherein a first element is a base metal and a second element is a dopant, wherein said first and second elements phase separate in their oxide state and form conductive oxides.  
     
     
         20 . The electrical contact in accordance with  claim 15  wherein the first element is a base metal, the second element is a dopant and a third element is a dopant, wherein said first, second and third elements phase separate in their oxide state and form conductive oxides.  
     
     
         21 . The electrical contact in accordance with  claim 15  wherein the alloy is a base material comprised of Cu having a dopant selected from the group consisting of Ge and Sn.  
     
     
         22 . The electrical contact of  claim 21  wherein said Cu and said dopant phase separate into a network of conductive veins.  
     
     
         23 . A process of preparing a metal alloy providing two metal elements which are not precious metals and oxidizing the metal alloy to produce a surface metal oxide layer that is conductive having a contact resistivity of 100 Ω-cm or less after the alloy has been subjected to 125° C. for 1008 hours.  
     
     
         24 . The process of  claim 23  wherein the alloy produced has a mixed valance state.  
     
     
         25 . The process of  claim 23  wherein the provided alloy is a non conductive alloy.  
     
     
         26 . The process of  claim 23  wherein the alloy formed has a network of conductive veins in the oxide or a conductive oxide layer on the alloy.  
     
     
         27 . The process of  claim 23  wherein the oxidation step is performed by a thermal treatment of the alloy in an oxidizing atmosphere or a thermal treatment of the alloy in a reducing atmosphere, or treatment of the alloy with UV light or a treatment of the alloy with an electron beam or a treatment of the alloy with x-rays or a treatment of the alloy with microwaves or a treatment of the alloy with a chemical treatment in an oxidizing or reducing environment.  
     
     
         28 . A bipolar plate for use in a fuel cell state comprising a metal alloy having at least two metal elements which are not precious metals, said alloy being capable of forming a surface metal oxide layer that is conductive having a resistivity less than or equal to 100 Ω-cm or less after the alloy has been subjected to 125° C. for 1008 hours.  
     
     
         29 . A method of forming a bipolar plate for use in a fuel cell assembly, comprising: 
 (a) forming a substrate blank of the bipolar plate from a conductive metal; and    (b) depositing a layer on at least one surface of the blank, the layer comprising a metal alloy comprising at least two metal elements which are not precious metals, said alloy being capable of forming a surface metal oxide layer that is conductive having a resistivity less than or equal to 100 Ω-cm or less after the alloy has been subjected to 125° C. for 1008 hours.