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

Abstract

Superconductive MgB 2 /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 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 determined by 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/KÁm at 30 K, a value much higher than those found for NbTi or Nb 3 Sn superconducting wires normally used in practice, which are 0.5 and 0.2 W/KÁm 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 T C of electrical resistivity of 39 K.

Wettability of Low Weight Borides by Commercial Aluminum Alloys − A Basis for Metal Matrix Composite Fabrication

“…No data on wetting properties of AlB 2 , CaB 6 , and MgB 2 with liquid aluminum and its alloys have been published so far. For MgB 2 , an investigation has been made concerning superconductivity of aluminum infiltrated MgB 2 , but no information about wetting was given . The same applies with regard to AlB 2 or CaB 6 except a few reports on the formation of AlB 2 and CaB 6 in aluminum melt and on the application of particulate CaB 6 reinforced aluminum matrix composites…”

Superconducting Properties of MgB<SUB>2</SUB> Particle Impregnated with Mg-Based Alloys

“…The details of sample preparation have been given elsewhere. 19) The powders were firstly ground in an agate mortar; secondly a preform of compacted MgB 2 powders of about 30 mm in diameter and 42 mm in length was prepared; the preform was located in a bottom of a steel mold and a host material of magnesium (or magnesium alloy) was placed on the preform; the mold was heat up to an appropriate temperature (the casting temperatures are given in Table 1 for all the samples); finally when the host material started to melt, a graphite disc from the top of the mold pressed to impregnate MgB 2 powders with the host material. The pressure was about 14 MPa.…”

“…A low temperature casting is a great advantage of SS-3DPC compared the PIT method, in which high temperature heat treatments easily introduced large voids in MgB 2 grains. Our previous work on MgB 2 /Al composite material demonstrated that the superconducting transition temperature (T c ) was observed at 38 K on the resistivity, a superconducting volume fraction estimated from magnetization was about 50%, 19) and further a superconducting wire of MgB 2 /Al of 1 mm diameter was extruded. 20) It has been known, however, that addition of aluminum to MgB 2 results in the loss of superconductivity.…”

“…19) This is a kind of the ex-situ technique, in which MgB 2 powder is impregnated with a half-melted host metal, such aluminum or magnesium, by pressure. A low temperature casting is a great advantage of SS-3DPC compared the PIT method, in which high temperature heat treatments easily introduced large voids in MgB 2 grains.…”

Fabrication of Al-Based Composite Extruded Plates Containing Cellulose Nanofibers and Their Microstructure and Mechanical Properties

“…7,8) The authors also have fabricated and reported composite materials of aluminum that exhibit, for example, photocatalytic properties of TiO 2 and superconducting properties of MgB 2 without compromising the properties of the functional composite particles by suppressing the reaction between the composite particles and aluminum matrix. 9,10) CeNFs are carbonized at around 200400°C. 3,11,12) Therefore, it is difficult to fabricate CeNF near the melting point of aluminum because CeNF is completely carbonized by the fabrication method using molten aluminum, which the authors have conventionally used.…”