Ultra-lightweight superconducting wire based on Mg, B, Ti and Al

P Kováč,M Kulich,A Rosová,P Krížik,J Kováč,I Hušek,T Melišek,M Balog,L Kopera

doi:10.1038/s41598-018-29354-1

Abstract

Actually, MgB2 is the lightest superconducting compound. Its connection with lightweight metals like Ti (as barrier) and Al (as outer sheath) would result in a superconducting wire with the minimal mass. However, pure Al is mechanically soft metal to be used in drawn or rolled composite wires, especially if applied for the outer sheath, where it cannot provide the required densification of the boron powder inside. This study reports on a lightweight MgB2 wire sheathed with aluminum stabilized by nano-sized γ-Al2O3 particles (named HITEMAL) and protected against the reaction with magnesium by Ti diffusion barrier. Electrical and mechanical properties of single-core MgB2/Ti/HITEMAL wire made by internal magnesium diffusion (IMD) into boron were studied at low temperatures. It was found that the ultra-lightweight MgB2 wire exhibited high critical current densities and also tolerances to mechanical stress. This predetermines the potential use of such lightweight superconducting wires for aviation and space applications, and for powerful offshore wind generators, where reducing the mass of the system is required.

Highlights

Many superconducting elements and compounds have been discovered[1], only few of them can be used for thermally and mechanically stabilized long length wires with high current densities
The first attempt to make an Al-stabilized MgB2 wire was made using Ta diffusion barrier and HITEMAL outer sheath[22], which demonstrated the possible production of Al-sheathed MgB2 wires
In this work we present original manufacturing method and properties of ultra-lightweight superconducting wire prepared by internal Mg diffusion process (IMD) into the B, which utilizes the lightest superconducting compound (MgB2 with 2.5 gcm−3) combined with the lightweight composite sheath (Al + 1.37 vol.% Al2O3 with a density of ~2.7 gcm−3) and light metallic barrier material (Ti with a density of 4.5 gcm−3)

Summary

Introduction

Many superconducting elements and compounds have been discovered[1], only few of them can be used for thermally and mechanically stabilized long length wires with high current densities. The first attempt to make an Al-stabilized MgB2 wire was made using Ta diffusion barrier and HITEMAL outer sheath[22], which demonstrated the possible production of Al-sheathed MgB2 wires It allowed to verify the utilization of Al + Al2O3 outer sheath for MgB2 wire and to show what superconducting properties, especially current densities, can be reached in medium magnetic fields. Due to lowered melting point of Al + 1.37 vol.% Al2O3 (∼ 652 °C)[22] in comparison to pure Al (660 °C) and close to melting of Mg (650 °C), really specific heat treatment is needed for MgB2/Ti/HITEMAL wire It should allow: (i) the fast formation of dense MgB2 phase[23], (ii) limited Ti/Al interaction and (iii) keeping the mechanical strength of Al + Al2O3 sheath

Methods

Results

Conclusion