Papers by Keyword: Superconducting Wire

Abstract: Bi-type superconductor is a high-temperature superconductor with mainly applied in the field of electricity. Silver is used as a wire sheath which causes the price of this wire production to be high. In this study Bi(Pb)-Sr-Ca-Cu-O (BPSCCO) wires were made by using stainless-steel (SS316) tubes which is cheaper and is not change its properties by the temperature of the formation of BPSCCO at 860°C. The preparation of superconducting wire is done by the Powder-In-Tube method, sintering and withdrawing/ rolling process. TiO₂ powder was added to analyze the effect on the formation of BPSCCO. Based on analyzing results, there is a dominant impurity phase that has been formed, namely Fe_2.5Ti_0.5O₄. We found that in the use of stainless-steel tubes and the TiO₂ powder (5wt%), 2223 phase was not formed. Although, small amounts of Bi₂Sr₂CaCu₂O₈ (2212) and Bi₁₀Sr₁₀Cu₅O₂₉ (2201) phases were found. Resistance versus temperature test using cryogenic equipment results indicate that there are symptoms of a low critical temperature around 10 K. 2212 and 2201 phases are thought to cause a low critical temperature in the samples, even though the decrease in electrical resistance does not reach zero. While the morphology of superconducting wire is quite well characterized from fairly even grains and only a small amount of porosity is formed.

Abstract: Development for superconducting wires of materials such as Nb₃Al and the high-temperature superconductors (HTS such as REBCO, Bi2223, and Bi2212) has been carried out for high-field magnet applications. It is known that these types of wire exhibit very different characteristics and performance for different applications. The development of Nb₃Al wire for high-field accelerator magnet has resulted in remarkable achievements in critical current using a Rapid Heating and Quenching (RHQ) method by High Energy Accelerator Research Organization (KEK) and National Institute for Materials Science (NIMS). As one example of a characteristic of Nb₃Al, the strain sensitivity of the critical current in the RHQ-Nb₃Al wire is better than that of Nb₃Sn wire. A strain study is needed to further the development of a high-filed magnet; therefore, we have carried out experimental studies using the neutron diffractometer at J-PARC Takumi. Researchers have recently achieved the highest critical current density for REBCO wires in a high-field above 15 T. For this reason, REBCO wire has been considered for high-field magnet NMR applications in Riken. But several obstacles remain, including coil degradation, shielding current and thermal runaway. In this paper, R&D on recent advances for applications will be presented.

Abstract: Our co-worker, Hishinuma et. al. has established a new route Powder-In-Tube (PIT) process using a high Ga content Cu-Ga compound in order to improve the superconducting property of the V₃Ga compound wire. In this study, we investigated microstructure of this high Ga content Cu-Ga/V composite superconducting wire. The different contrasts of matrix, V-Ga phase and Cu-Ga core were observed by SEM observation in cross section of 19 multifilamentary wire. And V-Ga phase was confirmed by SEM mapping. The area fraction of V-Ga phase increased when Ga content increased from 30% to 50%. Thin film sample with V-Ga phase for TEM was fabricated by FIB and observed by TEM in detail. Selected area diffraction pattern was obtained for V matrix, V-Ga phase and Cu-Ga core. The ratio of V to Ga for V-Ga phase was probably V₃Ga according to the EDS result. There was a linear interface between V matrix and V-Ga phase, while the interface between Cu-Ga core and V-Ga phase was not linear. On the other hand, there were some granular grains observed in V-Ga phase wear Cu-Ga core.

Abstract: Our co-worker, Hishinuma et. al. has established a new route Powder-In-Tube (PIT) process using a high Ga content Cu-Ga compound in order to improve the superconducting property of the V₃Ga compound wire. In this study, we investigated microstructure of this high Ga content Cu-Ga/V composite superconducting wire. The different contrasts of matrix, V-Ga phase and Cu-Ga core were observed by SEM observation in cross section of 19 multifilamentary wire. And V-Ga phase was confirmed by SEM mapping. The area fraction of V-Ga phase increased when Ga content increased from 30% to 50%. Thin film sample with V-Ga phase for TEM was fabricated by FIB and observed by TEM in detail. Selected area diffraction pattern was obtained for V matrix, V-Ga phase and Cu-Ga core. The ratio of V to Ga for V-Ga phase was probably V₃Ga according to the EDS result. There was a linear interface between V matrix and V-Ga phase, while the interface between Cu-Ga core and V-Ga phase was not linear. On the other hand, there were some granular grains observed in V-Ga phase wear Cu-Ga core.

Abstract: To identify the possibility of using GdAlO3 (GAO) as a buffer layer for YBa2Cu3O7-δ (YBCO) coated superconductor wire, we report the result of GAO deposition on SrTiO3 (STO) single crystal substrates by sol-gel processing. Precursor solution was prepared by dissolving stoichiometric quantities of gadolinium hexahydrate and aluminum isoproxide in a mixed binary solvent (2-4 pentanedione:methyl alcohol=1:1). The solutions were spin-coated on STO (100) single crystal substrates and heated at 500
~1100
for 2 h in wet Ar-5% H2 atmosphere. A FESEM observation of the surface morphology of the GAO has shown that it has a very smooth surface with a faceted morphology indicating epitaxy. It was shown in x-ray diffraction characterization that epitaxial GAO films with epitaxial orientation relationship of (001)[112]GAO||(100)[110]STO have been grown on STO (100) substrates.

Abstract: In the present 5-year national project since 2003, the development of YBCO coated conductors (CC) has advanced rapidly. The high performance processing group of SRL-ISTEC and Fujikura Ltd. has been working on the long tape of the PLD-YBCO superconductor on the IBAD-Gd2Zr2O7 buffered substrate tape. Very recently the SRL group achieved the highest value on the product of Ic x L in the world, 51,940 Am (212 m x 245 A). Fujikura Ltd. also realized the longest buffered substrate tape of 500m long IBAD tape and obtained a 200 m long coated conductor with Ic value of 88 A. In the low cost processing group using MOD, CVD and so on, the high Ic value of 525 A was obtained by SRL using the TFA-MOD method on the IBAD substrate. The 45m long TFA-MOD tape was also obtained with the Ic value of 155 A by Showa Electric Wire and Cable Company. Similarly 100- 200 m class long tapes were also obtained by the MOCVD (Chubu Power Electric Company) and PLD-HoBCO processes (Sumitomo Electric Industry Ltd.). Both groups above are further developing for the final goal of 500 m long tapes with the Ic of 300 A/cm-w at the production rate of 5 m/h. Furthermore, the feasibility study for the application has started due to the above success of long tape production. Several kinds of preliminary experiments using long coated conductors are now in progress for the power applications such as (1) Power Cable, (2) Transformer, (3) Motor and so on.

Abstract: The levels of stress and strain experienced by the windings of a superconducting magnet during its manufacture and operation are dependent on the mechanical properties of the multifilamentary composite wire that the windings are comprised of. It is also influenced by the change in dimensions of the wire during the reaction heat-treatment stage of the manufacturing process. Using specimens cut from a spool of 1.5mm diameter niobium tin type superconducting wire, the influence of the heat-treatment process on the mechanical properties and dimensions have been investigated. The heat-treatment was carried out in an inert atmosphere using apparatus specially developed for the purpose. For heat-treatment durations up to that required to complete the reaction of the niobium filaments into Nb3Sn, the volume and diameter of the wires increased with increasing heat-treatment duration. The maximum increase was 2% and 0.8% respectively. The length of the wires decreased slightly for the shorter heat-treatments, but increased up to 0.33% for the longer ones. The mechanical properties were significantly different for specimens that had no heat-treatment compared to those that had only a short heat-treatment, one that was insufficient to convert much of the niobium into Nb3Sn. Before heat-treatment the bronze within the wires is in a work-hardened state, but gets annealed during the heat-treatment and this is probably the major cause of the change in mechanical properties. Apart from becoming more brittle, the mechanical properties do not change much for different durations of heat-treatment. This is quite remarkable considering that the composition changes dramatically with the length of the heat-treatment.