Polymer coating for filamentary YBa2Cu3Ox superconductors

Polymer coating for filamentary YBa2Cu3Ox superconductors was examined. The precursor filaments were prepared by solution spinning through aqueous pol y(vinyl alcohol) solution containing mixed acetates of Y, Ba and Cu. The as -drawn filaments were heated to remove volatile components and to generate a superconducting phase. The synthesis of polyamide acid for the polymer co ating was made. The filamentary superconductors were coated with the polyam ide acid and cured to convert to the polyimide. The surface of the sample w as an insulator. The critical current (I-c) value of the filamentary sample at 77 K was preserved by the polyimide coating. Moreover, the I-c for the polyimide-coated sample was maintained after holding at room temperature fo r more than 6 months. After thermal cycling between 77 K and room temperatu re 10 times, the I-c for the coated sample did not deteriorate, whereas the I-c for the sample without polymer coating disappeared. Polymer coating us ing epoxy resin applied to the filamentary superconductors was also examine d. (C) 2001 Kluwer Academic Publishers.