A method is described for the production of superconductive wires based on hollow filaments made of MgB.sub.2, which comprises: a) the formation of a composite billet by means of the coaxial insertion in a tubular metallic container of a cylindrical bar made of metallic magnesium and amorphous boron powder in the interspace between the container and bar, said powder being pressed between the metallic container and the magnesium bar, in such a quantity that the weight ratio magnesium/boron is higher than 1.2; b) at least one plastic deformation treatment of the composite billet thus obtained until a wire with a pre-fixed diameter is obtained, with the subsequent winding of the wire onto a support; c) a thermal treatment of the filament product thus obtained, at a temperature ranging from 700.degree. C. to 950.degree. C. for a time ranging from 15 minutes to three hours.
A method of manufacturing a Fe-sheathed MgB.sub.2 wire includes the steps of: I. Selecting a carbon steel tube with 0.1% to 0.3% carbon; a. Crimping a first end of the tube; b. Selecting a Mg powder at least 99.8% pure, and sized for 325 mesh; c. Selecting a B powder, at least 99.99% pure, and sized for 325 mesh; d. Stoichiometrically mixing the Mg and B powders to form a mixture powder; e. Milling the mixture powder by using high-energy ball mill for 0.5 to 6 hours and using stainless steel mixing balls and vial, wherein the mass ratio of ball to powder is 20:1, to form a milled powder; f. Filling and packing the tube in an argon atmosphere with the milled powder to create a packing density of about 1.5 g/cm.sup.3; g. Crimping the second end of the tube to create a powder-filled tube; h. Rolling the powder-filled tube to create the Fe-sheathed MgB.sub.2 wire; and i. Annealing the as-rolled wire at 600 to 900.degree. C. for 0.5 to 3 hours at high purity argon environment to create superconducting wire.
A method is described for the preparation of superconductor massive bodies of MgB.sub.2, having a density close to the theorical value, which comprises the following passages: mechanical activation of crystalline boron with the formation of activated powders; formation of a porous preform of said powders; assembly of the porous boron preform and massive precursors of metallic magnesium in a container and sealing thereof in an atmosphere of inert gas or with a low oxygen content; thermal treatment of the boron and magnesium as assembled above, at a temperature higher than 700.degree. C. for a time greater than 30 minutes, with the consequent percolation of the magnesium, in liquid phase, through the activated crystalline boron powders.
