US 2001/0011066 A1 · Fabrication of superconducting wires and rods

Abstract

The fabrication of superconducting wires and rods having desired and consistent electrical and mechanical properties, in particular those based on Yttrium Barium Copper Oxide (YBCO) and Bismuth Strontium Calcium Copper Oxide (BSCCO), is disclosed. The first fabrication step is to form an extrudable paste by mixing YBCO or BSCCO superconducting powder with a set of organic additives, which include binder, plasticizers lubricant, dispersant, and a solvent. The following additional steps are performed on both YBCO and BSCCO based wires or rods: (i) using a piston extruder to extrude the superconducting wire or rod; (ii) drying the wire or rod to remove the solvent; and (iii) subjecting the wire or rod to a binder burn-out treatment to remove the remaining organic additives. In addition, YBCO wires and rods also require a sintering step, while BSCCO wires and rods also require cold isostatic pressing and heat treatment steps. The formation of cracks in thicker YBCO and BSCCO based rods during the drying and heating process steps is avoided by extruding hollow rods. The additives, processing parameters, and processing stages used to fabricate the superconducting wires and rods help achieve desired and consistent electrical and mechanical properties.

Claims57

Dependent claims

An extrudable paste used in the fabrication of superconducting wires and rods, comprising:

(a) a superconducting powder;
(b) ethyl cellulose;
(c) glycerol;
(d) stearic acid;
(e) triolein;
and
(f) a solvent.

4 more elements

A process for fabricating superconducting wires and rods, comprising the steps of:

(a) providing a piston extruder comprising a die barrel, an extrusion nozzle, and a ram;
(b) closing said extrusion nozzle;
(c) loading extrudable paste in the form of granules into said die barrel, said extrudable paste comprising BSCCO powder, a binder, a plasticizer, a lubricant, a dispersant, and a solvent;
(d) subjecting said die barrel to a vacuum of about 200 millitorr;
(e) compacting said extrudable paste by using said ram to apply a compaction stress of about 100 MPa;
(f) opening said extrusion nozzle;
(g) extruding a wire or rod through said extrusion nozzle using said ram, said ram extruding said wire or rod at a rate of about 0.02 to 0.1 inch/minute;
(h) initially drying said wire or rod in still air at room temperature until about 20% of said solvent is removed;
(i) subsequently drying said wire or rod in flowing air at a temperature of about 60° C. until all remaining solvent is removed;
(j) initially heating said wire or rod in flowing oxygen until a temperature of about 100° C. is reached;
(k) subsequently heating said wire or rod in flowing oxygen at a rate in the range of about 6 to 15° C./hour until a temperature of about 300° C. is reached;
(l) thereafter heating said wire or rod in flowing oxygen at a rate of about 20° C./hour until a temperature of about 500° C. is reached;
(m) packing said wire or rod in a flexible container;
(n) placing said container in a support fixture;
(o) applying a first isostatic load to said container to densify said wire or rod;
(p) heating said wire or rod, in an atmosphere of about 9% oxygen and about 91% argon, at a temperature of about 830° C. for about 72 hours;
(q) applying a second isostatic load to said container to densify said wire or rod;
and
(r) heating said wire or rod, in an atmosphere of about 9% oxygen and about 91% argon at about 840° C. for about 72 hours.

16 more elements

A superconducting wire or rod which is fabricated by the steps of:

(a) providing a piston extruder comprising a die barrel, an extrusion nozzle, and a ram;
(b) closing said extrusion nozzle;
(c) loading extrudable paste in the form of granules into said die barrel, said extrudable paste comprising BSCCO powder, a binder, a plasticizer, a lubricant, a dispersant, and a solvent;,
(d) subjecting said die barrel to a vacuum of about 200 millitorr;
(e) compacting said extrudable paste by using said ram to apply a compaction stress of about 100 MPa;
(f) opening said extrusion nozzle;
(g) extruding a wire or rod through said extrusion nozzle using said ram, said ram extruding said wire or rod at a rate of about 0.02 to 0.1 inch/minute;
(h) initially drying said wire or rod in still air at room temperature until about 20% of said solvent is removed;
(i) subsequently drying said wire or rod in flowing air at a temperature of about 60° C. until all remaining solvent is removed;
(j) initially heating said wire or rod in flowing oxygen until a temperature of about 100° C. is reached;
(k) subsequently heating said wire or rod in flowing oxygen at a rate in the range of about 6 to 15° C./hour until a temperature of about 300° C. is reached;
(l) thereafter heating said wire or rod in flowing oxygen at a rate of about 20° C./hour until a temperature of about 500° C. is reached;
(m) packing said wire or rod in a flexible container;
(n) placing said container in a support fixture;
(o) applying a first isostatic load to said container to density said wire or rod;
(p) heating said wire or rod, in an atmosphere of about 9% oxygen and about 91% argon, at a temperature of about 830° C. for about 72 hours;
(q) applying a second isostatic load to said container to density said wire or rod;
and
(r) heating said wire or rod, in an atmosphere of about 9% oxygen and about 91% argon at about 840° C. for about 72 hours.

16 more elements

Dependencies are inferred from the claim text.

Fabrication of superconducting wires and rods

Life of this patent

Fabrication of superconducting wires and rods

Life of this patent

Abstract

Claims57