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 rare earth-based alloy, 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 at a temperature less than about 1800 degrees C. wherein X is selected from the group consisting of Si, Ge, Sn, Pb, As, Sb, Bi, and P to achieve substantial completion of the carbothermic reduction reaction to form a low carbon alloy that comprises a majority of a rare earth element selected from the group consisting of La, Ce, and MM, a minor amount of X present in an amount of about 1 weight % to 18 weight % of the alloy, and a low carbon content in an amount of about 2 weight % or less of the alloy.
2. The method of claim 1 wherein the oxide comprises La 2 O 3 .
3. The method of claim 2 wherein the alloy comprises LaSi 0.5 .
4. The method of claim 2 wherein the alloy comprises LaX′ 0.5 , where X′ is selected from the group consisting of Ge, Sn, Pb, As, Sb, Bi, and P.
5. The method of claim 1 wherein the carbothermic reduction is initiated at a temperature of at least about 1300 degrees C.
6. The method of claim 1 wherein the oxide comprises CeO 2 .
7. The method of claim 6 wherein the alloy comprises CeSi 0.5 .
8. The method of claim 6 wherein the alloy comprises CeX′ 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 oxide comprises mischmetal (MM) oxide.
10. The method of claim 9 wherein the alloy comprises MMSi 0.5 .
11. The method of claim 9 wherein the alloy comprises MMX′ 0.5 , where X is selected from the group consisting of Ge, Sn, Pb, As, Sb, Bi, and P.
12. The method of claim 1 wherein zirconium oxide also is present and reduced.
13. The method of claim 1 wherein the reactant element is Si.
14. The method of claim 1 including providing a substantially stoichiometric amount of carbon as a reducing agent relative to oxides present.
15. The method of claim 1 wherein the carbon content of the alloy is in a range of about 0.005 weight % to about 2 weight % C.
16. A method of making a rare earth-based alloy, comprising carbothermically reducing an oxide selected from the group consisting of a La-containing oxide, a Ce-containing oxide, and a MM-containing oxide in the presence of carbon particles as a reducing agent and silicon particles to achieve substantial completion of the carbothermic reduction reaction at a temperature below 1800 degrees C. to form a low carbon alloy that comprises a majority of a rare earth element selected from the group consisting of La, Ce, and MM, a minor amount of Si present in a range of about 1.0 weight % to about 18 weight % of the alloy, and an amount of C in a range of about 0.005 weight % to about 2 weight % of the alloy.