High critical current of Ti-sheathed MgB₂wires for AC and weight-critical applications

Abstract

The peculiar features of magnesium diboride make it suitable for many potential applications. In the last four years of investigation of MgB 2 , the scientific community's research was mainly motivated by features such as low cost, compatibility with straightforward processing methods, relatively high critical temperature, and absence of weak links between grains. Other applications suggest the accentuation of other MgB 2 properties. In particular its very low mass density makes it attractive for space activities, where the cost per kilogram for orbiting is still a huge obstacle, e.g. the cost of transport to low Earth orbit can reach 15 k$ kg −1 . In order to promote the use of this compound for space activities, we tested titanium as a sheath material. Titanium is non-magnetic and its alloys are almost half the weight of steel but with yield stresses up to three times higher. We fabricated Ti-sheathed MgB 2 through the powder-in-tube process. These wires show similar results to those sheathed with Fe. At 4 K the critical current density J c is well above 7 × 10 5 A cm −2 . The interface between the superconducting intermetallic compound and the lightweight sheath does not show any evidence of reaction and diffusion up to 900 • C. An analysis was carried out using x-ray diffraction, scanning electron microscopy with an energy dispersive spectrometer, and electron microprobe analysis.

In-Field ${\rm J}_{\rm C}$ Enhancement on Ti-Sheathed ${\rm MgB}_{2}$ Wires Doped With TiC Nanoparticles

“…For certain applications, such as space propulsion, where lightweight superconducting magnets are required, metal material, such as Titanium, with low mass density, excellent mechanical strength and good chemical compatibility with is chosen as sheath material. Recently, we have fabricated Ti-sheathed wires with promising current carrying capability in the presence of external magnetic field [8]- [10]. The results are comparable with non doped Fe-sheathed wires and tapes.…”

Toroidal magnetic fields for protecting astronauts from ionizing radiation in long duration deep space missions

“…The real quality of the cable depends from several factors, some of them relative to the production process, other to the test and quality control on the whole length of the produced cable. It can be reasonably assumed that in the near future, and perhaps also nowadays, it could be guaranteed the production of a MgB 2 cable similar to the sample produced several years ago [9], carrying 1.3 kA/mm 2 at 2 T when operated at T ¼20 K. Assuming an operative density of current of 1.0 kA/mm 2 at 2 T and 20 K, and supposing that it reduces inversely to the maximum field in the superconductor, the density of current to be considered for the compact toroid (B max ¼4 T) is 0.5 kA/mm 2 , and for the large toroid (B max ¼2.67 T) 0.75 kA/mm 2 . The masses of the needed s. c. cable respectively reduce to 7.0 t and 7.6 t. The total mass of the toroids (cable þmechanics) becomes (Fig.…”

EDX and ion beam treatment studies of filamentary in situ MgB2 wires with Ti barrier

“…The in situ reaction to form MgB 2 in iron or Nb sheath occurs usually at lower temperatures (600-750 • C) [1][2][3], which has the benefit of reducing undesirable interactions between the starting powders and the sheath material. However, improved J c values of in situ wires were obtained for MgB 2 wires using Ti diffusion barrier annealed at temperatures up to 900 • C indicating no detrimental chemical interactions [4][5][6]. Successful fabrication of 4-filament square in situ wires have been reported using Ti as a barrier layer in MgB 2 /Ti/Cu/Monel with 10 wt% SiC in the core [5].…”