Fabrication of MgB₂ Wire by Suspension Spinning

Abstract

Suspension spinning of commercially available MgB₂ powder was examined to fabricate a long superconducting MgB₂ wire. The MgB₂ powders were suspended in a nonaqueous poly(vinyl alcohol) solution. The viscous spinning dope was extruded as a filament into a precipitating medium of methyl alcohol and coiled on a winding drum. The as-drawn filaments were pressed and heated in order to remove volatile compounds. The filamentary samples were then cold-pressed, enveloped by an iron sheet with a pellet of mixed powder of Mg and B or with Mg powders, vacuum-sealed in a fused quartz tube and sintered. The J_c of the sample was strongly dependent on the starting materials and sintering condition. Although the transport J_c value was low, such as 4500 A/cm² at 4.2 K and self-fields, a J_c value of more than 200 A/cm² was maintained by applying a field of 10 T. Doping of 5 at% nanoscale SiC resulted in an improvement in the J_c and superconductivity at 4.2 K was maintained by applying a field of 14 T.