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Zhang H.,Southwest Jiaotong University | Wen S.-L.,Southwest Jiaotong University | Pan M.,Southwest Jiaotong University | Pan M.,Western Superconducting Technologies Company | And 4 more authors.
Chinese Physics B | Year: 2016

Based on the density functional theory, we calculated the structures of the two main possible self-interstitial atoms (SIAs) as well as the migration energy of tungsten (W) atoms. It was found that the difference of the 110 and 111 formation energies is 0.05-0.3 eV. Further analysis indicated that the stability of SIAs is closely related to the concentration of the defect. When the concentration of the point defect is high, 110 SIAs are more likely to exist, 111 SIAs are the opposite. In addition, the vacancy migration probability and self-recovery zones for these SIAs were researched by making a detailed comparison. The calculation provided a new viewpoint about the stability of point defects for self-interstitial configurations and would benefit the understanding of the control mechanism of defect behavior for this novel fusion material. © 2016 Chinese Physical Society and IOP Publishing Ltd.

Qi M.,Northeastern University China | Qi M.,Northwest Institute for Nonferrous Metal Research | Sun Y.Y.,Xian University of Architecture and Technology | Pan X.F.,Western Superconducting Technologies Company | And 5 more authors.
IEEE Transactions on Applied Superconductivity | Year: 2014

Although the rapid heating quenching and transformation method has been used as a general way to fabricate high-performance \hbox{Nb}-{3}\hbox{Al} superconducting wires, the complicated heat treatment apparatus and techniques obstruct its practical application. In this paper, Nb-Al saturated solid solution (\hbox{Nb}(\hbox{Al})-{\rm ss}) was fabricated by the mechanical alloying method at room temperature, and the superconducting onset transition temperature (T-{c\hbox{-}{\rm onset}}) of the \hbox{Nb}-{3}\hbox{Al} bulk transforming from the \hbox{Nb}(\hbox{Al})-{\rm ss} reached 15.3 K. Based on these results, two groups of \hbox{Nb}-{3}\hbox{Al} superconducting wires were fabricated in combination with the in situ powder-in-tube method to investigate the effects of ball milling time, wire diameter and the cross-sectional shape on the superconducting properties, and the factors that affected the critical current density (J-{c}) were also discussed. The best value of J-{c} in magnetic induction at 6 T was obtained in the round wire with a diameter of \Phi1.0 mm fabricated with the powder ball milled for 5 h. © 2002-2011 IEEE.

Li J.F.,Western Superconducting Technologies Company | Li J.F.,National Engineering Laboratory for Superconducting Materials Preparation | Zhang K.,Western Superconducting Technologies Company | Zhang K.,National Engineering Laboratory for Superconducting Materials Preparation | And 16 more authors.
IEEE Transactions on Applied Superconductivity | Year: 2016

ITER toroidal field (TF) systems consist of 18 independent coils that are around the torus, whose primary function is to confine the plasma particles. The TF coil conductor is a cable-in-conduit conductor (CICC) made up of superconducting, Nb3Sn-based strands mixed with pure copper strands. As the only supplier in China, Western Superconducting Technologies Company, Ltd. (WST) will supply TF Nb3Sn strands using internal tin route for ITER, and over 6,000 km of Nb3Sn strands have been produced in the past four years. Main performance of Nb3Sn strands, including critical current, n value, wire diameter, Cu/non-Cu ratio, hysteresis loss and RRR are reported and analyzed in this paper. © 2002-2011 IEEE.

Pan X.F.,Western Superconducting Technologies Company | Yan G.,Western Superconducting Technologies Company | Cui L.J.,Western Superconducting Technologies Company | Chen C.,Northeastern University China | And 7 more authors.
IEEE Transactions on Applied Superconductivity | Year: 2014

In this paper, we reported the recent progress in developing practical kilometer-length rod-in-tube (RIT) multifilamentary Nb3Al superconducting wires at WST, which included the preparation of Cu/Nb-Al precursor wires, design and manufacture of rapid heating and quenching (RHQ) equipment, and RHQ heat-treatment process of Nb3Al wires. Superconducting properties and microstructure of the RIT Nb3Al wires have been discussed. By measuring magnetization and transport critical current properties of Nb3Al wires, it is found that, for all the samples, the onset superconducting transition temperature Tc reaches 16.8-17.3 K, and at 4.2 K and 15 T, the critical current density Jc of 830 A/mm2 at the Nb3Al wires have been achieved. This paper suggests that it is possible to develop the practical Nb3Al superconducting wires by using the RIT Nb3Al precursor wires, in combination with RHQ heat-treatment process. © 2014 IEEE.

Zhang K.,Northwestern Polytechnical University | Zhang K.,Western Superconducting Technologies Company | Zhang K.,State Engineering Laboratory of Superconducting Material Preparation | Zhang P.,Northwestern Polytechnical University | And 18 more authors.
IEEE Transactions on Applied Superconductivity | Year: 2016

Three kinds of Nb3Sn strands with different designs were made by bronze route. Studies were carried out on bronze-to-NbTa-volume ratio, filament diameter, annealing, hot isostatic pressure process, diffusion barrier, and heat treatment. It is important for strand designs to achieve a good performance. Moreover, bronze-to-NbTa-volume ratios of 2.4 and 2.8 were applied in the strand designs. Strands with lower bronze ratio means that more Nb3Sn layer fraction formed, while, at the same time, it is provided with a high critical current density (Jc). Jc increases with the reduction of filament diameter, when there is the same bronze ratio. In addition, Nb and Ta were used as diffusion barrier materials. A strand that used Nb barrier has several times hysteresis loss to a strand that used Ta barrier. When it comes to the intermediate processes, such as annealing and hot isostatic pressure, they could affect the homogeneous deformation and properties of strands. It is important to keep a low annealing temperature to realize a high Jc and n-value. As for the hot isostatic pressure process, it is helpful for uniform cross section. Furthermore, different heat treatments were also carried out, while analysis was also conducted on the microstructure. © 2002-2011 IEEE.

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