Claims
- 1. An superconducting article comprised of one or more elongated metal matrix regions containing one or more embedded elongated superconducting Mg—B regions running the full length of the article, wherein the superconducting Mg—B regions have a density greater than 95% of the theoretical density, and a transition temperature in zero field of 30 K.
- 2. The superconducting article of claim 1, wherein the Mg—B superconductor comprises approximately 53 weight % Mg and 47 weight % B.
- 3. The superconducting article of claim 1, wherein the Mg—B superconductor comprises MgB2.
- 4. The superconducting article of claim 1, wherein the article is a monofilament.
- 5. The superconducting article of claim 1, wherein the article is a multifilament.
- 6. The superconducting article of claim 1, wherein the article is a round wire.
- 7. The superconducting article of claim 1, wherein the article is an aspected tape.
- 8. The superconducting article of claim 1, wherein the cross-sectional dimension of the article is in the range of 0.1 mm2 to 5 mm2.
- 9. The superconducting article of claim 1, wherein 40% to 80% of the cross-section is comprised of a non-superconducting metal matrix.
- 10. The superconducting article of claim 1 wherein the metal matrix is comprised of copper or a copper alloy.
- 11. The superconducting article of claim 1, wherein the metal matrix is selected from the group consisting of stainless steel, oxide dispersion strengthened copper and nickel alloys.
- 12. The superconducting article of claim 1 with a metal matrix comprised of copper or a copper alloy, and a second metal layer between the Mg—B regions and the copper regions.
- 13. The superconducting article of claim 12, wherein the second metal layer is a barrier layer.
- 14. The superconducting article of claim 13, wherein the barrier layer is selected from the group consisting of tantalum, niobium, nickel, nickel alloys, iron, tungsten, molybdenum and combinations thereof.
- 15. The superconducting article of claim 12, wherein the second metal layer is a high resistivity layer.
- 16. The superconducting article of claim 15, wherein the resistivity layer is selected from the group consisting of cobalt, manganese, NiTi, and NiZr.
- 17. The superconducting article of claim 1, wherein the superconducting regions further comprise flux pinning sites.
- 18. The superconducting article of claim 15, wherein the flux pinning sites are selected from the group consisting of particles of metal diborides, rare earth oxides, boron oxide, MgO, and boron.
- 19. The superconducting article of claim 1, further comprising a metal laminate on the outer surface of the article.
- 20. The superconducting article of claim 19, wherein the metal laminate is selected from the group consisting of copper, copper alloys, stainless steel, aluminum, aluminum alloys, and nickel alloys.
- 21. A method of making a high density Mg—B superconducting article, comprising the steps of:
providing a packed powder sheath, said powder comprising a source of magnesium and boron; subjecting the packed powder sheath to a symmetric deformation, said deformation selected to elongate the packed powder sheath to form a wire while retaining the free flow of particles within the powder core; subjecting the wire to high reduction rolling, said high reduction rolling selected to reduce the wire thickness by 40 to 95%; and heating the rolled article to improve the superconducting properties of the article.
- 22. The method of claim 21, wherein the powder of the packed powder sheath comprises a mechanically alloyed Mg+B powder.
- 23. The method of claim 21, wherein the powder of the packed powder sheath comprises a mixture of boron and magnesium.
- 24. The method of claim 21, wherein the powder of the packed powder sheath comprises MgB2.
- 25. The method of claim 21, wherein the particle size of the powder is in the range of 10 nm to 1 micron.
- 26. The method of claim 21, wherein the Mg—B superconductor further comprises flux pinning sites.
- 27. The method of claim 21, wherein the sheath is comprised of copper or a copper alloy.
- 28. The method of claim 21, wherein the packing density of the packed powder sheath is in the range of 35 to 80%.
- 29. The method of claim 21, wherein the symmetric elongating deformation is selected from the group consisting or wire drawing, extrusion and rod rolling.
- 30. The method of claim 29, wherein wire drawing is conducted using a die having a total die angle greater than or equal to 14°.
- 31. The method of claim 30, wherein wire drawing is conducted using a die having a total die angle in the range of 14° to 25°.
- 32. The method of claim 21, wherein the high reduction rolling reduces thickness in the range of 50 to 75%.
- 33. The method of claim 21, wherein the high reduction rolling is carried out using large diameter rolls that have a large contact area with the wire.
- 34. The method of claim 33, wherein the large diameter rolls have a diameter greater than 2 inches.
- 35. The method of claim 33, wherein the large diameter rolls have a diameter greater than or equal to about 4 inches.
- 36. The method of claim 21, wherein a low reduction rolling is carried out before the large reduction rolling.
- 37. The method of claim 36, wherein the low reduction rolling reduces the thickness of the wire by less than 20% per pass.
- 38. The method of claim 36, wherein the low reduction rolling alters the shape of the wire to provide a geometry that has a larger contact area with the roll in the subsequent high reduction rolling operation.
- 39. The method of claim 21, wherein the wire prior to high reduction rolling has a geometry is round, oval, square, rectangular or tape-like.
- 40. The method of claim 21, wherein the heating is carried out to convert a precursor of the Mg—B superconductor into the Mg—B superconductor.
- 41. The method of claim 21, wherein the heating is carried out to sinter the Mg—B superconductor.
RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C. §119(e) to U.S. Ser. No. 60/303,058, filed Jul. 5, 2001, all entitled “Processing of Magnesium-Boride Superconductors,” which is hereby incorporated in its entirety by reference.
Provisional Applications (1)
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Number |
Date |
Country |
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60303058 |
Jul 2001 |
US |