MgB
2 wires have been prepared through diffusion process in pure Mg metal tube. Amorphous B powder mixed with 5 mol% SiC nano-sized powder addition 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 initially drawn into around wires of 1.0 ~ 0.8 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 isostatic pressed (HIP treated) under 100 MPa during heat treatment. The MgB
2 core was synthesized through the diffusion reaction between outside Mg metal tube and inside B powder with SiC addition. The MgB
2 core forms denser structure without voids and cracks in comparison with conventional in-situ powder in tube (PIT process) MgB
2 wires. The Ic values at 4.2 K for MgB
2 wire of 1.0 mm and 0.8 mm in diameter with HIP reach to 145 A and 164 A at 5 T, which correspond to the Jc of 1680 A/mm
2 and 2930 A/mm
2, respectively. These values are much higher than that of PIT processed MgB
2 wire.
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