Process for heat treating superconductor wire

Abstract

An oxide superconductor wire is prepared by preparing a length of precursor wire for processing into an oxide superconductor wire and coating the precursor wire with an isolating layer. The coated wire is wound onto a reel in a spiralling manner, such that each turn of the spiral is in alignment with the preceding turn of the spiral along an axis perpendicular to the axis of winding. The wound precursor wire is then heated to form the oxide superconductor. The removable isolating layer is prepared by coating the wire with a solution including a metal oxide and a porosity-inducing component, and heating the coated wire so as to induce porosity and control grain size of the metal oxide so as to render the coating removable. The coating should function to isolate the overlapping turns of the wound wire from neighboring wires, so that not diffusion bonding or adherence between the turns occurs. The coating should also be readily removable because the coating can interfere with subsequent processing of the oxide superconductor wire.

What is claimed is:  
     
         1 . In a method of preparing a metal tube for a length of superconducting wire comprising inserting a superconducting base material into the metal tube, the metal tube having an outer surface, and packing or coiling the metal tube so that a portion of the outer surface of the metal tube would contact another surface, whereby heating the superconducting base material and metal tube to a temperature that forms of the superconducting phase of the superconducting base material, the temperature being sufficiently close to the melting point temperature of the metal tube, would cause the portion of the outer surface of the metal tube to adhere to the other surface, the improvement comprising: 
 coating the portion of the outer surface of the metal tube with powder material particles suspended in an effectively liquid component before the packing or coiling so that the portion of the outer surface of the metal tube does not contact the outer surface after the packing or coiling, the powder material having a melting point temperature higher than the melting point temperature of the metal tube, and the liquid component evaporating or burning away completely at the temperature that forms the superconducting phase of the superconducting base material.    
     
     
         2 . The method according to  claim 1 , wherein the powder material is a metal oxide.  
     
     
         3 . The method according to  claim 1 , wherein the coating is such that the particles do not touch the other surface after the packing or coiling.  
     
     
         4 . The method according to  claim 2 , wherein the coating is such that the particles do not touch the other surface after the packing or coiling.  
     
     
         5 . The method according to  claim 1 , wherein the liquid component comprises a solvent admixed with a polymer.  
     
     
         6 . The method according to  claim 1 , wherein the liquid component comprises a solvent admixed with a polymer.  
     
     
         7 . The method according to  claim 3 , wherein the solvent comprises at least one of acetone, alcohol or toluene.  
     
     
         8 . The method according to  claim 6 , wherein the solvent comprises at least one of acetone, alcohol or toluene.  
     
     
         9 . The method according to  claim 3 , wherein the polymer comprises polyvinyl butyral.  
     
     
         10 . The method according to  claim 8 , wherein the polymer comprises polyvinyl butyral.  
     
     
         11 . The method according to  claim 9 , wherein the polyvinyl butyral comprises from 0.1 to 10 percent by weight of the liquid component.  
     
     
         12 . The method according to  claim 10 , wherein the polyvinyl butyral comprises from 0.1 to 10 percent by weight of the liquid component.  
     
     
         13 . The method according to  claim 2 , wherein the metal oxide powder material comprises at least one of Al 2 O 3 , Cr 2 O 3 , Cu x O y , Ni x O y , Zn x O y , Z x O y  or Ta x O y .  
     
     
         14 . The method according to  claim 12 , wherein the metal oxide powder material comprises at least one of Al 2 O 3 , Cr 2 O 3 , Cu x O y , Ni x O y , Zn x O y , Zr x O y  or Ta x O y .  
     
     
         15 . The method according to  claim 2 , wherein the metal oxide powder material comprises Zr.  
     
     
         16 . The method according to  claim 15 , wherein the metal oxide powder material comprises Zr.