Abstract: The sheath (3) is a material, which includes an aluminium (Al) matrix, in which nanometric aluminium oxide particles (Al2O3) are homogenously dispersed, the content of Al2O3 is 0.25 to 5 vol. % and the balance is Al. It is preferred that Al2O3 originates from the surface layer present on Al powder used as feedstock material for consolidation. The superconductor based on magnesium diboride (MgB2) core (1) is fabricated by powder-in-tube or internal magnesium diffusion to boron technology, while the tube is the Al+Al2O3 composite, which is a product of powder metallurgy. A loose Al powder is pressed by cold isostatic pressing, and then the powder billet is degassed at elevated temperature and under vacuum, and then is hot extruded into a tube. A thin diffusion barrier (2) tube filled up with a mixture of Mg and B powders or Mg wire surrounded with B powder is placed into the Al+Al2O3 composite tube under inert gas or vacuum. Such composite unit is cold worked into a thin wire and then annealed at 625-655° C.

Abstract: The sheath (3) is a material, which includes an aluminium (Al) matrix, in which nanometric aluminium oxide particles (Al2O3) are homogenously dispersed, the content of Al2O3 is 0.25 to 5 vol. % and the balance is Al. It is preferred that Al2O3 originates from the surface layer present on Al powder used as feedstock material for consolidation. The superconductor based on magnesium diboride (MgB2) core (1) is fabricated by powder-in-tube or internal magnesium diffusion to boron technology, while the tube is the Al+Al2O3 composite, which is a product of powder metallurgy. A loose Al powder is pressed by cold isostatic pressing, and then the powder billet is degassed at elevated temperature and under vacuum, and then is hot extruded into a tube. A thin diffusion barrier (2) tube filled up with a mixture of Mg and B powders or Mg wire surrounded with B powder is placed into the Al+Al2O3 composite tube under inert gas or vacuum. Such composite unit is cold worked into a thin wire and then annealed at 625-655° C.