Zirconia-stabilized multi-filamentary niobium-tin superconducting wire

Abstract

A multi-filament superconducting wire in which the filaments comprise zirconia-stabilized ultra-fine grain Nb 3 Sn. The superconducting wire is formed by wire-drawing a preform comprising a metallic matrix and at least one niobium alloy rod having zirconium and oxygen in solid solution and heat treating the drawn wire in the presence of tin to yield at least one continuous filament comprising ultra-fine grain Nb 3 Sn having semi-coherent ZrO 2 precipitates disposed therein. The ZrO 2 precipitates serve to stabilize the ultra-fine grain microstructure of the Nb 3 Sn at temperatures up to 1100° C. and allows Nb 3 Sn to maintain the ultra-fine grain microstructure when heat treated at temperatures that are greater than those previously used. By using higher temperatures to form Nb 3 Sn, the time required for heat treatment can be significantly reduced.

1 . A superconducting wire, said superconducting wire comprising: 
 a) at least one filament having a filament diameter, wherein said at least one filament is continuous and comprises a plurality of Nb 3 Sn grains having a plurality of ZrO 2  precipitates disposed therein, wherein said plurality of Nb 3 Sn grains has an average grain size of less than about 10 percent of said filament diameter; and    b) a metallic matrix surrounding and contacting said at least one filament, wherein said metallic matrix is electrically conductive at temperatures below about 77 K and has a coefficient of thermal expansion that is substantially the same as or greater than that of Nb 3 Sn.    
     
     
         2 . The superconducting wire according to  claim 1 , wherein said superconducting wire comprises a plurality of filaments.  
     
     
         3 . The superconducting wire according to  claim 2 , wherein said plurality of filaments includes at least one filament comprising one of elemental niobium, niobium zirconium alloy, and combinations thereof.  
     
     
         4 . The superconducting wire according to  claim 1 , wherein said filament diameter is less than about 10 microns.  
     
     
         5 . The superconducting wire according to  claim 4 , wherein said filament diameter is less than about 2 microns.  
     
     
         6 . The superconducting wire according to  claim 5 , wherein said filament diameter is between about 2 microns and about 1 micron.  
     
     
         7 . The superconducting wire according to  claim 1 , wherein said plurality of Nb 3 Sn grains has an average grain size of less than about 1 micron.  
     
     
         8 . The superconducting wire according to  claim 7 , wherein said plurality of Nb 3 Sn grains has an average grain size of less than about 200 nanometers.  
     
     
         9 . The superconducting wire according to  claim 1 , wherein said at least one filament comprises an outer layer of Nb 3 Sn surrounding a core of elemental niobium.  
     
     
         10 . The superconducting wire according to  claim 1 , wherein said metallic matrix imparts a compressive strain to said at least one filament.  
     
     
         11 . The superconducting wire according to  claim 1 , wherein said metallic matrix imparts zero strain to said at least one filament.  
     
     
         12 . The superconducting wire according to  claim 1 , wherein said plurality of ZrO 2  precipitates stabilizes said plurality of Nb 3 Sn grains up to about 1100° C.  
     
     
         13 . The superconducting wire according to  claim 1 , wherein said superconducting wire is formed from a preform, said preform comprising: 
 a) at least one niobium alloy rod, said at least one niobium alloy rod comprising a niobium alloy having oxygen and zirconium in solid solution, wherein zirconium and oxygen are present in an atomic ratio of about 1:2; and    b) a metallic preform matrix surrounding and contacting said at least one niobium alloy rod, wherein said metallic preform matrix comprises tin.    
     
     
         14 . The superconducting wire according to  claim 13 , wherein said metallic preform matrix is a copper-tin bronze.  
     
     
         15 . The superconducting wire according to  claim 13 , wherein said metallic preform matrix comprises between about 5 weight percent and about 13 weight percent tin.  
     
     
         16 . The superconducting wire according to  claim 1 , wherein said superconducting wire is joined to a second superconducting wire to form a laminate wire.  
     
     
         17 . The superconducting wire according to  claim 1 , wherein said superconducting wire is wound with a second superconducting wire to form a cable.  
     
     
         18 . The superconducting wire according to  claim 1 , wherein said superconducting wire is flattened to form a tape.  
     
     
         19 . A preform for forming a superconducting wire, wherein the superconducting wire comprises at least one filament, wherein said at least one filament comprises a plurality of Nb 3 Sn grains having a plurality of ZrO 2  precipitates disposed therein and a metallic matrix surrounding and contacting said at least one filament, said preform comprising: 
 a) at least one niobium alloy rod, said at least one niobium alloy rod comprising a niobium alloy having zirconium and oxygen in solid solution, wherein zirconium and oxygen are present in an atomic ratio of about 1:2; and    b) a metallic preform matrix surrounding and contacting said at least one niobium alloy rod, wherein said metallic preform matrix comprises tin.    
     
     
         20 . The preform according to  claim 19 , wherein said metallic preform matrix comprises between about 5 weight percent and about 16 weight percent tin.  
     
     
         21 . The preform according to  claim 19 , wherein said metallic preform matrix is a copper-tin bronze.  
     
     
         22 . The preform according to  claim 19 , wherein zirconium comprises up to about 8 atomic percent of said niobium alloy.  
     
     
         23 . The preform according to  claim 22 , wherein zirconium comprises up to about 1 atomic percent of said niobium alloy.  
     
     
         24 . A superconducting wire, wherein said superconducting wire is formed from a preform comprising at least one niobium alloy rod, said at least one niobium alloy rod comprising a niobium alloy having zirconium and oxygen in solid solution, wherein zirconium and oxygen are present in an atomic ratio of about 1:2, and a metallic preform matrix surrounding and contacting said at least one niobium alloy rod, wherein said metallic preform matrix comprises tin, said superconducting wire comprising: 
 a) a plurality of filaments, wherein each of said plurality of filaments has a filament diameter, wherein at least one of said plurality of filaments is continuous and comprises a plurality of Nb 3 Sn grains having a plurality of ZrO 2  precipitates disposed therein, wherein said plurality of Nb 3 Sn grains has an average grain size of less than about 10 percent of said filament diameter; and    b) a metallic matrix surrounding and contacting said plurality of filaments, wherein said metallic matrix is electrically conductive at temperatures below about 77 K and has a coefficient of thermal expansion that is substantially the same as or greater than that of Nb 3 Sn.    
     
     
         25 . The superconducting wire according to  claim 24 , wherein said plurality of filaments includes at least one filament comprising one of elemental niobium, niobium zirconium alloy, and combinations thereof.  
     
     
         26 . The superconducting wire according to  claim 24 , wherein said filament diameter is less than about 10 microns.  
     
     
         27 . The superconducting wire according to  claim 26 , wherein said filament diameter is less than about 2 microns.  
     
     
         28 . The superconducting wire according to  claim 27 , wherein said filament diameter is between about 2 microns and about 1 micron.  
     
     
         29 . The superconducting wire according to  claim 24 , wherein said plurality of Nb 3 Sn grains has an average grain size of less than about 1 micron.  
     
     
         30 . The superconducting wire according to  claim 29 , wherein said plurality of Nb 3 Sn grains has an average grain size of less than about 200 nanometers.  
     
     
         31 . The superconducting wire according to  claim 24 , wherein at least one of said plurality of filaments comprises an outer layer of Nb 3 Sn surrounding a core of elemental niobium.  
     
     
         32 . The superconducting wire according to  claim 24 , wherein said metallic matrix imparts a compressive strain to said plurality of filaments.  
     
     
         33 . The superconducting wire according to  claim 24 , wherein said metallic matrix imparts zero strain to said plurality of filaments.  
     
     
         34 . The superconducting wire according to  claim 24 , wherein said plurality of ZrO 2  precipitates stabilizes said plurality of Nb 3 Sn grains up to about 100° C.  
     
     
         35 . The superconducting wire according to  claim 24 , wherein said metallic preform matrix is a copper-tin bronze.  
     
     
         36 . The superconducting wire according to  claim 24 , wherein said metallic preform matrix comprises between about 5 weight percent and about 13 weight percent tin.  
     
     
         37 . The superconducting wire according to  claim 24 , wherein said superconducting wire is joined to a second superconducting wire to form a laminate wire.  
     
     
         38 . The superconducting wire according to  claim 24 , wherein said superconducting wire is wound with a second superconducting wire to form a cable.  
     
     
         39 . The superconducting wire according to  claim 24 , wherein said superconducting wire is flattened to form a tape.  
     
     
         40 . An electromagnetic device comprising at least one superconducting wire, wherein said superconducting wire is formed from a preform comprising at least one niobium alloy rod, said at least one niobium alloy rod comprising a niobium alloy having zirconium and oxygen in solid solution, wherein zirconium and oxygen are present in an atomic ratio of about 1:2, and a metallic preform matrix surrounding and contacting said at least one niobium alloy rod, wherein said metallic preform matrix comprises tin, said superconducting wire comprising: 
 a) a plurality of filaments, wherein each of said plurality of filaments has a filament diameter, wherein said at least one of said plurality of filaments is continuous and comprises a plurality of Nb 3 Sn grains having a plurality of ZrO 2  precipitates disposed therein, wherein said plurality of Nb 3 Sn grains has an average grain size of less than about 10 percent of said filament diameter;    b) and a metallic matrix surrounding and contacting said plurality of filaments, wherein said metallic matrix is electrically conductive at temperatures below about 77 K and has a coefficient of thermal expansion that is substantially the same as or greater than that of Nb 3 Sn.    
     
     
         41 . The electromagnetic device according to  claim 40 , wherein said metallic preform matrix is a copper-tin bronze.  
     
     
         42 . The electromagnetic device according to  claim 40 , wherein said metallic preform matrix comprises between about 5 atomic percent and about 13 atomic percent tin.  
     
     
         43 . The electromagnetic device according to  claim 40 , wherein said electromagnetic device is one of a superconducting magnet, a motor, a transformer, and a generator.  
     
     
         44 . The electromagnetic device according to  claim 43 , wherein said electromagnetic device is a superconducting magnet, and wherein said superconducting magnet is incorporated into a magnetic resonance imaging system.  
     
     
         45 . A method of making a superconducting wire, the superconducting wire comprising at least one filament, wherein said at least one filament is continuous and comprises a plurality of Nb 3 Sn grains having a plurality of ZrO 2  precipitates disposed therein and a metallic matrix surrounding and contacting said at least one filament, the method comprising the steps of: 
 a) providing a niobium alloy having zirconium and oxygen in solid solution, wherein zirconium and oxygen are present in an atomic ratio of about 1:2;    b) forming at least one niobium alloy rod from the niobium alloy;    c) providing a metallic matrix material to the at least one niobium alloy rod;    d) forming a wire from the metallic matrix material and the at least one niobium alloy rod; and    e) heat treating the wire at a predetermined temperature for a predetermined time, thereby forming the superconducting wire.    
     
     
         46 . The method according to  claim 45 , wherein the step of providing a niobium alloy having zirconium and oxygen in solid solution comprises: 
 a) providing an alloy comprising elemental niobium and Nb 2 O 5 ;    b) decomposing the niobium alloy to form elemental niobium having oxygen dissolved therein;    c) providing zirconium to the elemental niobium having oxygen dissolved therein, wherein zirconium and oxygen are present in a ratio of about 1:2; and    d) forming a niobium alloy having zirconium and oxygen in solid solution.    
     
     
         47 . The method according to  claim 46 , wherein the step of decomposing the niobium alloy to form elemental niobium having oxygen dissolved therein comprises vacuum arc melting the alloy to form elemental niobium having oxygen dissolved therein.  
     
     
         48 . The method according to  claim 46 , wherein the step of forming a niobium alloy comprising a niobium alloy having zirconium and oxygen in solid solution comprises vacuum arc remelting the zirconium and the elemental niobium having oxygen dissolved therein to form a niobium alloy having zirconium and oxygen in solid solution.  
     
     
         49 . The method according to  claim 48 , further including the step of homogenizing the niobium alloy.  
     
     
         50 . The method according to  claim 49 , wherein the step of homogenizing the niobium alloy comprises heat treating the niobium alloy at a predetermined temperature for a predetermined time.  
     
     
         51 . The method according to  claim 45 , wherein the step of forming at least one niobium alloy rod from the niobium alloy comprises one of electron discharge milling the niobium alloy to form at least one niobium alloy rod therefrom, casting at least one niobium alloy rod from the niobium alloy, extruding at least one rod from the niobium alloy, and drawing at least one niobium alloy rod from the niobium alloy.  
     
     
         52 . The method according to  claim 51 , further including the step of cold-working the at least one niobium alloy rod.  
     
     
         53 . The method according to  claim 52 , wherein the step of cold-working the at least one niobium alloy rod comprises at least one of swaging, extruding, and wire-drawing the at least one niobium alloy rod.  
     
     
         54 . The method according to  claim 45 , wherein the step of forming a wire from the metallic matrix material and the at least one niobium alloy rod comprises: 
 a) forming a preform by surrounding the at least one niobium alloy rod with the metallic matrix material such that the metallic matrix material contacts the at least one niobium alloy rod; and    b) forming a wire from the preform.    
     
     
         55 . The method according to  claim 54 , wherein the step of forming a wire from the preform comprises extruding the wire followed by one of drawing the wire and swaging the wire.  
     
     
         56 . The method according to  claim 55 , further comprising the step of re-stacking the wire following one of drawing the wire and swaging the wire, wherein the step of re-stacking the wire comprises extruding the wire followed by one of drawing the wire and swaging the wire.  
     
     
         57 . The method according to  claim 56 , wherein the step of re-stacking is repeated at least once.  
     
     
         58 . The method according to  claim 45 , wherein the step of heat treating the wire at a predetermined temperature for a predetermined time comprises heat treating the wire at a temperature of between about 700° C. and about 1100° C. for a time of up to about 48 hours.  
     
     
         59 . The method according to  claim 45 , wherein the step of heat treating the wire at a predetermined temperature for a predetermined time comprises winding the wire and heat treating the wire at a predetermined temperature for a predetermined time after winding the wire.  
     
     
         60 . A method of making a preform for a superconducting wire, wherein the preform comprises at least one niobium alloy rod, the at least one niobium alloy rod comprising a niobium alloy having zirconium and oxygen in solid solution, and a metallic preform matrix surrounding and contacting said at least one niobium alloy rod, the method comprising the steps of: 
 a) providing a niobium alloy having zirconium and oxygen in solid solution wherein zirconium and oxygen are present in an atomic ratio of about 1:2;    b) forming at least one niobium alloy rod from the niobium alloy;    c) providing a metallic matrix material to the at least one niobium alloy rod; and    d) forming a preform by surrounding the at least one niobium alloy rod with the metallic matrix material such that the metallic matrix material contacts the at least one niobium alloy rod.    
     
     
         61 . The method according to  claim 60 , wherein the step of providing a niobium alloy having zirconium and oxygen in solid solution comprises: 
 a) providing an alloy comprising elemental niobium and Nb 2 O 5 ;    b) decomposing the niobium alloy to form elemental niobium having oxygen dissolved therein;    c) providing zirconium to the elemental niobium having oxygen dissolved therein, wherein zirconium and oxygen are present in a ratio of about 1:2; and    d) forming a niobium alloy having zirconium and oxygen in solid solution.    
     
     
         62 . The method according to  claim 61 , wherein the step of decomposing the niobium alloy to form elemental niobium having oxygen dissolved therein comprises vacuum arc melting the alloy to form elemental niobium having oxygen dissolved therein.  
     
     
         63 . The method according to  claim 62 , wherein the step of forming a niobium alloy having zirconium and oxygen in solid solution comprises vacuum arc remelting the zirconium and the elemental niobium having oxygen dissolved therein to form a niobium alloy comprising a niobium alloy having zirconium and oxygen in solid solution.  
     
     
         64 . The method according to  claim 63 , further including the step of homogenizing the niobium alloy.  
     
     
         65 . The method according to  claim 64 , wherein the step of homogenizing the niobium alloy comprises heat treating the niobium alloy at a predetermined temperature for a predetermined time.  
     
     
         66 . The method according to  claim 60 , wherein the step of forming at least one niobium alloy rod from the niobium alloy comprises one of electron discharge milling the niobium alloy to form at least one niobium alloy rod therefrom, casting at least one niobium alloy rod from the niobium alloy, extruding at least one rod from the niobium alloy, and drawing at least one niobium alloy rod from the niobium alloy.  
     
     
         67 . The method according to  claim 60 , further including the step of cold-working the at least one niobium alloy rod.  
     
     
         68 . The method according to  claim 67 , wherein the step of cold-working the at least one niobium alloy rod comprises at least one of swaging, extruding, and wire-drawing the at least one niobium alloy rod.  
     
     
         69 . A superconducting wire, said superconducting wire comprising: 
 a) at least one filament having a filament diameter, wherein said at least one filament is continuous and comprises a plurality of Nb 3 Sn grains having a plurality of ZrO 2  precipitates disposed therein, wherein said plurality of Nb 3 Sn grains has an average grain size of less than about 10 percent of said filament diameter; and    b) a metallic matrix surrounding and contacting said at least one filament, wherein said metallic matrix has a coefficient of thermal expansion that is substantially the same as or greater than that of Nb 3 Sn,    wherein said superconducting wire is formed by: providing a niobium alloy having zirconium and oxygen in solid solution, wherein zirconium and oxygen are present in an atomic ratio of 2:1; forming at least one niobium alloy rod from the niobium alloy; providing a metallic matrix material to the at least one niobium alloy rod; forming a wire from the metallic matrix material and the at least one niobium alloy rod; and heat treating the wire at a predetermined temperature for a predetermined time to form said superconducting wire.