Superconducting composite strip for high field coil windings - has strong continuous fibres coated with superconductor in metal matrix

摘要

Superconducting composite strip has a matrix of a metal (I), which is good electrical conductor, and embedded high-strength continuous fibres (II) with a dia. of 6-15 mu m (II) having an approx. 1-2 um thick coating of a brittle superconducting intermetallic cpd. (III) of the A3B type (in which A is Nb or V and B is Si, Ge, Sn or Al) with beta W/A 15-structure (II) pref. consists of C, graphite or W. The composite is ductile and has high strength (over 70 kp/mm2 e.g. up to 100 kp/mm2 for C in Al). The use of (III) in the form of a thin film has a favourable effect on its transition temp. The high critical magnetic field strength and mechanical strength of the strip make them suitable for winding high field coils. Also, the rectangular section and relatively high critical current density allow a large number of winding in a small space, e.g. a superconductor of 0.7 x 1.5 mm2 section can be wound to a dia. up to ca. 15 cm without impairing its mechanical and superconducting properties. The composite contains 15-50 vol.-% coated (II) and is produced by coating (II) with (III) by chemical vapour deposition and embedding in a (I) melt. E.g. C fibre yarn was coated with V3Si and embedded in Al, Cu or Ag.