Enhanced Magnetic Property of MgB 2 Wire Using Phenol-Formaldehyde Resin

We fabricated carbon (C)-doped hbox MgB 2 wires using phenol-formaldehyde resin (PF) as a C source to improve their critical current density ( J rm c ) in a magnetic field. In order to induce homogenous C doping, boron (B) powders were mixed with PF via liquid mixing technique and then the PF-treated B and Mg powders were mixed. The wires were fabricated by conventional powder-in-tube (PIT) process, followed by heat treatment through an in-situ reaction route. We observed that C was substituted for the B sites in the PF-doped hbox MgB 2 and that the actual C content increased with increasing PF content. The doped hbox MgB 2 wires exhibited lower critical transition temperature ( T rm c ) and self-field J rm c , but superior H rm c 2 value and better J rm c ( B ) performance than the undoped sample. The 3 wt% PF sample had the highest J rm c value of 7.77 10 3 Unknown character hbox A / cm 2 , which is significantly higher than that of the undoped sample ( 0.29 10 3 Unknown character hbox A / cm 2 ) at 5 K and 6.4 T.