Superconductivity and Thermal Property of MgB<SUB>2</SUB>/Aluminum Matrix Composite Materials Fabricated by 3-Dimensional Penetration Casting Method

Abstract

Superconductive MgB2/Al composite material with low and high volume fractions of particles were fabricated by our special pre-packing technique and 3-dimensional penetration casting method. The composite material showed homogeneous distribution of MgB2 particles in the Al-matrix with neither any aggregation of particles nor defects such as cracks or cavities. The critical temperature of superconducting transition (TC) was determined by electrical resistivity and magnetization to be about 37–39 K. Specific heat measurements further supported these TC 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 MgB2/Al composite material was about 25 W/K·m at 30 K, a value much higher than those found for NbTi or Nb3Sn superconducting wires normally used in practice, which are 0.5 and 0.2 W/K·m at 10 K, respectively. A billet of the superconducting material was successfully hot-extruded, forming a rod. The same as the billet sample, the rod showed an onset TC of electrical resistivity of 39 K.