Superconductivity and thermal property of MgB ₂/Al composite materials

The superconductive MgB ₂/Al composite material with low and high volume fractions of particles were fabricated by our special pre-packed technique. The composite material showed homogeneous distribution of MgB ₂ particles in the Al-matrix with neither any aggregation of particles nor defects such as cracks or cavities. The critical temperature of superconducting transition (T _c) was obtained via electrical resistivity and magnetization to be about 37∼39 K. Specific heat measurements further supported these T _c findings. The Meissner effect was also verified in the liquid He, in which a piece of the composite floated above a permanent magnet. The thermal conductivity of the MgB ₂/Al composite material was about 25 W/K·m at 30 K, which value is much higher than those for the NbTi or Nb ₃Sn superconductive wires normally used in practice that are 0.5 and 0.2 W/K·m at 10 K, respectively.