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The effects of thermal neutron irradiation and excess oxygen on the properties of Ti-sheathed MgB2 wires were investigated separately in this paper. No significant influence was observed when thermal neutron irradiation with fluence levels of 1.23 x 1014 and 5.75 x 1014 cm2 were applied on the sample, while fluence level of 3.16 x 1015 cm2 provided a strong suppression of in-field critical current density. Excess oxygen in sample preparation process had negative effect on the properties of the MgB2 wires. The samples prepared in air possessed lower critical temperature and in-field current carrying capability in comparison with the sample prepared in glove box. [ABSTRACT FROM AUTHOR]

For large-scale electric power applications of MgB2 wire, especially at AC environments, development of nonmagnetic sheath material is essential. In this study, Cu-sheathed MgB2 wire was fabricated using the powder-in-tube method and ultra-fine Mg and B precursor prepared by high-energy ball milling. Lowering the annealing temperature and shortening the annealing time effectively limit the reaction between Mg and Cu. Critical current density of the wire annealed at 700° C for 5 minutes is 4.3 × 104 A/cm² at 20 K and self-field. Adding excess Mg in precursor further enhances critical current to 250 A at 20 K and self-field. These results demonstrate the potential of Cu-sheathed MgB2 wires for large-scale applications. [ABSTRACT FROM AUTHOR]

Ti-sheathed MgB2 wires doped with different amount of TiC nanoparticles were investigated. X-ray diffraction pattern suggested the existence of TiC0.59 phase and carbon incorporation into MgB2 lattice to form Mg(B1-xCx )2. Strong enhancement of in-field current carrying capability was observed on 2.5% TiC doped sample. The temperature effect was also studied. It was found that 850°C was the optimized annealing temperature. [ABSTRACT FROM AUTHOR]

Recent studies on metal-clad superconducting MgB[sub 2] wires indicates that iron is one of the best candidates as a cladding metal. Also it was found that grain refinement of MgB[sub 2] leads to more compacted material which yields high transport critical current density. In this study, we prepared the iron-clad MgB[sub 2] tapes by using the powder-in-tube technique. A modified rolling process was applied to cold work the powder-filled tubes into tapes. Very fine grains were observed on as-rolled tapes. Tapes manufactured using this process were found to carry 260 Ampere at 20 K under self-field and 180 Ampere under 1.5 Tesla. The transition temperature is 39.4 K and ΔT = 0.6 K. The results indicate that grain refinement is very effective in improving the current carrying capability of the MgB[sub 2] tapes. [ABSTRACT FROM AUTHOR]

Presents measurements of the direct current transport critical current of oriented-grained YBa[sub 2]Cu[sub 3]O[sub 7] (YBCO) superconductors. Production of high quality current contacts using thick silver pads; Formation of silver pads by sputter etching the YBCO surface; Details of the contact fabrication method.

Abstract: The phases in Cu sheathed MgB2 wires fabricated using very short annealing time are studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and critical current (I c) measurements. By comparison with the XRD pattern of our synthesized MgCu2, the XRD line located at 2θ ≈36.1° for all Cu-sheathed MgB2 wire samples is unambiguously identified to be due to the MgCu2 phase. This line was previously unidentifiable due to its absence in the standard pattern of MgCu2 recorded in the current powder diffraction file (PDF) database. We found that the XRD lines previously attributed to Cu atoms by other groups, are actually due to the CuMg δ (with δ ≈6%) phase, indicating that copper does not exist in the form of un-reacted atoms in the core materials of these Cu-sheath MgB2 wires. For samples heat treated at 700°C or below, the phases are basically the superconducting MgB2 and impurity MgCu2 phases. Quantitative analysis indicates that the molar percent of the MgB2 phase in these samples is over 90%. For samples heat treated at 725°C or above, two additional phases, CuMg δ and MgB4 phases, are also present. The content of CuMg δ phase increases rapidly with the increase of the heat treatment temperature from 725°C and 750°C. This increase in CuMg δ content is one of the factors responsible for the dramatic decrease of I c. These phase identification results are consistent with our SEM result and the published Cu–Mg phase diagram. It is also found that the variation of the MgB2 fraction with the heat treatment temperature peaks at 700°C, well correlated to the variation trend of I c with heat treatment temperature. [Copyright &y& Elsevier]