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Pan X.,Japan National Institute of Materials Science | Pan X.,Western Superconducting Technologies WST Co. | Matsumoto A.,Japan National Institute of Materials Science | Kumakura H.,Japan National Institute of Materials Science | And 3 more authors.
Applied Physics Express | Year: 2012

MgB 2/Fe tapes with various forms of mono- and co-doped C sources were prepared by an in-situ powder-in-tube (PIT) method to study the effect of different C sources on the transport critical current density J c behavior of MgB 2. A remarkable J c improvement at 4.2 K under higher fields and a significant increase in the actual content of C substitution for B were achieved for the tapes with various C sources co-doped. For these co-doped tapes, both enhanced H c2 and flux pinning properties are responsible for their J c improvement in this work. Comparing the 4wt% C 9H 11NO doped tape with the 20 wt% malic acid doped tape, the latter possesses much better in-field J c performance at 4.2 K and 10 T and sharper field dependence of Jc, which suggests that the flux pinning plays a crucial role in determining its J c behavior. © 2012 The Japan Society of Applied Physics.


Cui L.J.,Western Superconducting Technologies WST Co. | Yan G.,Western Superconducting Technologies WST Co. | Pan X.F.,Western Superconducting Technologies WST Co. | Zhang P.X.,Western Superconducting Technologies WST Co. | And 6 more authors.
Physica C: Superconductivity and its Applications | Year: 2015

With extremely high critical current density (Jc) and excellent strain tolerance, Nb3Al superconductor is considered as an alternative to Nb3Sn for application of high-field magnets. However, owing to their complex structure, Nb3Al superconducting wires can hardly meet the requirement of engineering application at present. In this work, a novel simple-structured Nb3Al superconducting wires with Cu-matrix and different filament numbers were prepared by the conventional jelly-roll method, as well as a heat-treatment of 800-850°C for 20-50 h. The results show that a 18-filament superconducting wire with length longer than 100 m can be successfully prepared by this method, and also this Nb3Al long wire has the Tc of 13.4 K and Jc of 4.7 × 104 A/cm2 at 4.2 K and 12 T. These suggest that with further optimization, the simple-structured Nb3Al superconducting wires are very promising to fabricate the km-grade long wires to meet the requirement of engineering application. © 2015 Elsevier B.V. All rights reserved.


Pan X.F.,Western Superconducting Technologies WST Co. | Feng Y.,Western Superconducting Technologies WST Co. | Yan G.,Western Superconducting Technologies WST Co. | Cui L.J.,Western Superconducting Technologies WST Co. | And 8 more authors.
Superconductor Science and Technology | Year: 2015

In this paper, we have reported the manufacture of a novel simple-structured jelly-roll Nb3Al precursor long wire, and its electromagnetic properties and microstructure with different rapid heating and quenching (RHQ) heat-treatments. By comparing three processing methods, it is found that the rolling and drawing (RD) method is more suitable to the fabrication of kilometer-length Nb3Al precursor wire without annealing. Using homemade RHQ equipment, we have successfully carried out RHQ heat-treatment of Nb3Al wire samples with various heating conditions. Based on magnetization and magnetoresistivity measurements, the onset superconducting transition temperature, T c and upper critical field, H c2 (0) of optimal Nb3Al wire reach 17.9 K-18.0 K and 29.7 T, respectively. Through microstructure and composition analysis, the Nb3Al superconductor in the optimal wire displays a typical 'layer-to-layer' structure, which comprises alternate crystalline Nb3Al and amorphous Nb layers, and the Nb3Al grains sizes are about 100 nm-300 nm. Furthermore, many small holes are dispersed in the Nb3Al superconductor due to the diffusion reaction from Al to Nb site. The work suggests the simple-structured Nb3Al precursor wire with RHQ heat-treatment is very promising for high-field application. © 2016 IOP Publishing Ltd.


Pan X.F.,Western Superconducting Technologies WST Co. | Pan X.F.,Northwest Institute for Nonferrous Metal Research | Yan G.,Western Superconducting Technologies WST Co. | Yan G.,Northwest Institute for Nonferrous Metal Research | And 12 more authors.
Physica C: Superconductivity and its Applications | Year: 2014

High-performance Nb3Al superconducting wire is a promising candidate to the application of high-field magnets. However, due to the production problem of km-grade wires that are free from low magnetic field instability, the Nb3Al wires made by rapid heating, quenching and transformation (RHQT) are still not available to the large-scale engineering application. In this paper, we reported the properties of the in situ powder-in-tube (PIT) Nb3Al superconducting wires, which were made by using the mechanically alloyed Nb(Al)ss supersaturated solid solution, as well as the low temperature heat-treatment at 800 °C for 10 h. The results show that Nb3Al superconductors in this method possess very fine grains and well superconducting properties, though a little of Nb 2Al and Nb impurities still keep being existence at present work. At the Nb3Al with a nominal 26 at.% Al content, the onset Tc reaches 15.8 K. Furthermore, a series of Nb3Al wires and tapes with various sizes have been fabricated; for the 1.0 mm-diameter wire, the J c at 4.2 K, 10 T and 14 T have achieved 12,700 and 6900 A/cm 2, respectively. This work suggests it is possible to develop high-performance Cu-matrix Nb3Al superconducting wires by directly using the Nb(Al)ss supersaturated solid-solution without the complex RHQT heat-treatment process. © 2014 Elsevier B.V. All rights reserved.


Du L.,Southwest Jiaotong University | Li P.,Southwest Jiaotong University | Liu Z.,Southwest Jiaotong University | Cui Y.,Southwest Jiaotong University | And 5 more authors.
Journal of Superconductivity and Novel Magnetism | Year: 2014

We investigated the reaction process of NbAl in samples prepared by the rod-in-tube method. Precursor strands were isothermally heat-treated at a very wide temperature range from 800 to 1,400 °C for 48 h. As a result, we obtained NbAl3 and NbAl diffusion layers below 1,000 °C; NbAl3 and Nb2Al at 1,000 to 1,200 °C; and NbAl3, Nb2Al, and a small amount of nonstoichiometric Nb3Al at 1,400 °C. Diffusion or reaction layers were observed clearly by scanning electron microscope for all of the samples mentioned above. Furthermore, nonstoichiometric Nb3Al phase can be found only at 1,400 °C through a higher resolution. Additionally, magnetic measurement results also show that the superconducting transition temperature is about 14.8 K only for the sample obtained at 1,400 °C for 48 h. © 2014, Springer Science+Business Media New York.

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