The reactive liquid Mg infiltration process to produce large superconducting bulk MgB2 manufacts

An alternative and simple manufacturing process is presented to produce high density bulk MgB2 superconducting objects of large dimensions. The process avoids the use of high pressure apparatus and consists in the reactive infiltration of liquid Mg in B powders preforms. With an appropriately designed stainless steel container for the reactants, several manufacts of different shape have been obtained, including tubes, cylinders, rings or disks, of dimensions of the order of the tens of centimeters. The MgB2 material, unlike high temperature oxide superconductors, allows an easy percolation of the supercurrents across the grains boundaries, even if it is in the polycrystalline form. Due to this property, the large MgB2 manufacts obtained by the reactive liquid infiltration present high superconducting characteristics, as demonstrated by transport and magnetic measurements up to 35K. In particular the magnetic levitation and the magnetic shielding capability appear as the most promising applicative fields in which there is a need for large and homogeneously superconducting bulk pieces. For space applications, the use of MgB2 superconductors may enable a substantial improvement in the compactness and weight of cryogenic systems, with respect to the actual systems based on the liquid He temperatures. Furthermore, with respect to other high temperature oxide superconductors, MgB2, besides the disadvantages of the need of a 20-30K cryogenic system, presents the advantages of a relative lower density (2.4g/cm3), higher mechanical strength and easier processability, like that here described.