Nb3al superconductor and method of manufacture

Abstract

A Nb Al superconducting wire and method for fabricating the same wherein Nb and Al powders in combination, or Nb—Al alloy powders are encapsulated in a metal tube, preferably copper or copper-alloy (e.g., CuNi), and the resultant composite is processed by conventional means to fine wire. Multifilamentary composites are produced by rebundling of the powder-filled wires into metal tubes followed by conventional processing to wire of a desired size. It is required for the use of Nb and Al powders in combination that the Nb and Al powder particle size be less than 100 nm. In the use of Nb—Al alloy powders, it is preferred, but not required, that the powder particle size be similarly of a nanometer scale. The use of nanometer-scale powders is beneficial to wire fabrication, allowing the production of long wire piece-lengths. At final wire size, the wires produced by practice of the present invention are heat treated at temperatures below the melting point of copper (1083° C.), with the heat treatment causing conversion of the powder cores or filaments to the A15 superconductor Nb Al. The resulting superconducting wires display critical superconducting properties previously achievable only by methods employing temperatures well in excess of the melting point of copper.