2014 年 25 巻 1+2 号 p. 5-8
MgB2 wires have been prepared by diffusion process in pure Mg metal tube. Amorphous B powder mixed with 5 mol% SiC nano-sized powder and 10 mol% MgH2 powder was encased in a Mg tube, and then the tube was inserted into a pure iron tube to form the Fe/Mg/B(powder) composite wires. The composite was drawn into around wires of 1.0 mm in diameter without intermediate annealing. The composite wires were heat treated at 630℃ for 5 h in Ar gas atmosphere. Some of the specimens were hot-pressed under 10 MPa during heat treatment. The MgB2 core was synthesized through the diffusion reaction between outer Mg metal tube and inner B powder. MgB2 core with no MgH2 addition forms denser structure without voids and cracks in comparison with MgH2 powder addition. The Ic values at 4.2 K for the hot-pressed MgB2 wire of no MgH2 addition and MgH2 addition were 79 A and 34.5 A at 6 T, which correspond to the Jc of 1151 A/mm2 and 377 A/mm2, respectively.
