Fabrication of Nb3Al Superconducting Wires Through Rapid Heating/Quenching in Open Air

Nb
₃
Al wire requires a simplified fabrication process as well as improved critical current density. We found that the reel-to-reel Rapid Heating/Quenching (RHQ) treatment could be safely operated in open air without an expensive dynamic vacuum system or a large metal vacuum chamber. It should provide a significant cost reduction. The electrode distance between the Cu pulley and the liquid Ga bath surface is set for 125 mm. The precursor wire is moving at speeds of 0.3, 0.6, or 1.0 m/s. The wire surface material (Nb) reacted with oxygen and made a homogeneous Ga-Nb oxide layer of several microns in thickness. Its surface morphology was very smooth, and it acted as a lubricant for the metal drawing dies of which would be considered a similar effect as an anode oxidation drawing technique. The Nb-Al supersaturated bcc solid solution alloy could be synthesized by RHQ in open air, and its synthesis condition might be shifted to slightly lower input heating energy. The heating energy in open air is probably adding an additional heating energy from the surface oxidation reaction.