A research team from the Slovak research institute has developed a novel ultra-lightweight superconductive wire based on magnesium diboride (MgB2) core stabilized with unique aluminum (Al) composite sheath. Ultrafine-grained Al stabilized and strengthened with nanoscale alumina (Al2O3) particles, meets all demanding and contradictory requirements placed on the sheath material of MgB2 core superconductor wire. On one hand, the ultra-lightweight superconductor wire technologically allows the fabrication of ultra-lightweight superconducting wire based on MgB2 core through the process known as internal magnesium (Mg) diffusion (IMD) into boron (B). The superconductor wire has a low density of 2.71 g.cm-3, it mechanically stabilizes Mg + B powder core during cold working operations and it is stabile at the temperature of Mg melting. On the other hand, the superconductor wire sheath provides the advantageous mechanical and electrical properties required for superconductor operation at cryogenic conditions.
The superconducting effect can be utilized in many applications such as in the space program, aerospace area and energy industry, where for a number of reasons the low rotational and total weight of devices which include superconductive wire is needed. A low weight of the superconductor in such applications yields in a higher efficiency, lower power consumption, higher speeds and acceleration of moving devices. Of all known superconducting materials, MgB2 is the lightest superconducting material of approximately three times lower density compared to e.g., Nb3Sn. Thus, lightweight superconducting wires are naturally designed based on the MgB2 superconducting core. However, nowadays superconductor designs, for example based on NbTi, Nb3Sn as well as MgB2, use a sheath mostly based on Cu, Cu alloys and Cu metal matrix composites (MMC), which has suitable electrical and mechanical properties. However, Cu based sheath, which forms a significant volume portion of the superconducting wire, contributes heavily to the overall mass of the superconductive wire. The use of other metals and alloys as the sheath material, such as niobium (Nb) or steel, also leads to the high weight of superconducting wires. Consequently, even for a lightweight MgB2 core, technical solutions of superconductors which utilize Cu sheath are known. The above-described drawbacks are largely eliminated by the novel superconductor with the MgB2 core and the sheath from Al MMC, wherein the sheath covers at least one MgB2 core, the sheath and the core may be separated by a thin diffusion barrier layer, which may be of various materials e.g., Ti, Ta, Nb, Fe. The principal idea lies in the fact that the superconductor sheath is formed by deformation of the MgB2 core and the sheath from Al MMC in the form of a tube. The tube is being the product of powder metallurgy, wherein the microstructure consists of near- or sub-micrometre Al grains, stabilized and strengthened by a small amount of homogeneously dispersed nanometric Al2O3 particles, which forms in situ in Al matrix. Exceptional structural stability ensures that the Al composite sheath material retains the required mechanical properties i.e., high strength together with sufficient ductility, even after MgB2 formation at the temperature of ~650 °C, which is close to the melting point of Al. This can be advantageously utilized in some applications, where there is intense mechanical tensile loading of ultra-lightweight superconductor under cryogenic conditions e.g., in high-field superconducting magnets or cables for the transfer of very large currents.
The institute is expecting to enter licensing agreement with the aim to implementing a novel ultra-lightweight superconductive wire into existing or emerging products. The preferred type of cooperation is also financing agreement. The institute is looking for a partner who would provide investment or other financing to enable manufacture and commercialization.