Method for producing La/Ce/MM/Y base alloys, resulting alloys, and battery electrodes
A carbothermic reduction method is provided for reducing a La-, Ce-, MM-, and/or Y-containing oxide in the presence of carbon and a source of a reactant element comprising Si, Ge, Sn, Pb, As, Sb, Bi, and/or P to form an intermediate alloy material including a majority of La, Ce, MM, and/or Y and a minor amount of the reactant element. The intermediate material is useful as a master alloy for in making negative electrode materials for a metal hydride battery, as hydrogen storage alloys, as master alloy additive for addition to a melt of commercial Mg and Al alloys, steels, cast irons, and superalloys; or in reducing Sm 2 O 3 to Sm metal for use in Sm—Co permanent magnets.
1. A method of making a metal hydride battery electrode material, comprising carbothermically reducing an oxide selected from the group consisting of La-containing oxide, a Ce-containing oxide, and MM-containing oxide in the presence of carbon as a reducing agent and a source of a reactant element X wherein X is selected from the group consisting of Si, Ge, Sn, Pb, As, Sb, Si, and P to achieve substantial completion of the carbothermic reduction reaction to form a low carbon rare earth-based alloy having a majority of a rare earth element selected from the group consisting of La, Ce, and MM, a minor amount of the reactant element X, and a low carbon content of about 2 weight % or less and alloying the carbothermically reduced, low carbon rare earth-based alloy with a transition metal to form the electrode material.
2. The method of claim 1 wherein the transition metal is Ni.
3. The method of claim 2 wherein some of the Ni is substituted by at least one of B, Al, Si, Ti, V, Cr, Mn, Co, Fe, Cu, Zn, and Mo.
4. The method of claim 1 wherein the rare earth-based alloy further includes an amount of Pr, Nd, and/or Zr.
5. The method of claim 1 wherein said minor amount of the reactant element X is about 5 to about 50 atomic %.
6. The method of claim 5 wherein said minor amount of reactant element X is about 5 atomic % to about 40 atomic %.
7. The method of claim 1 wherein the rare earth-based alloy comprises LaSi 0.5 .
8. The method of claim 1 wherein the rare earth-based alloy comprises LaX′ 0.5 where X′ is selected from the group consisting of Ge, Sn, Pb, As, Sb, Bi, and P.
9. The method of claim 1 wherein the rare earth-based alloy comprises CeSi 0.5 .
10. The method of claim 1 wherein the rare earth-based alloy comprises CeX′ 0.5 , where X′ is selected from the group consisting of Ge, Sn, Pb, As, Sb, Bi, and P.
11. The method of claim 1 wherein the rare earth-based alloy comprises MMSi 0.5 .
12. The method of claim 1 wherein the rare earth-based alloy comprises MMX′ 0.5 , where X′ is selected from the group consisting of Ge, Sn, Pb, As, Sb, Bi, and P.
13. The method of claim 1 wherein the electrode material comprises R(Ni 1-x ,Co x ) 5 where R is La, Ce, and MM and x is 0 to 0.75.
14. The method of claim 1 wherein said low carbon content is about 0.005 weight % to about 2 weight % of the alloy.
15. The method of claim 1 wherein the carbothermic reducing of said oxide occurs at a temperature less than about 1800 degrees C.