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Rubeli T.,Ecole Polytechnique Federale de Lausanne | Dutoit B.,Ecole Polytechnique Federale de Lausanne | Martynova I.,SuperOx | Makarevich A.,SuperOx | And 2 more authors.
IOP Conference Series: Materials Science and Engineering | Year: 2017

Superconducting wires are not perfectly homogeneous in term of critical current as well as stabilization. In resistive fault current limiter applications this could lead to hot spots if the fault current is only slightly above the nominal current of the device. Increasing stabilization by using thicker silver coating for example may prevent this problem but this method implies longer wire length to maintain the same impedance during a fault. Very efficient cooling in another way to prevent hot spots, this can be achieved in nucleate boiling regime. Optimal insulation can be used to prevent film boiling regime, staying in nucleate boiling regime in a much broader temperature range. In this work a novel technique is used to monitor in real time the temperature of the wire during the quench. Using this method several increasing insulation thicknesses are tested, measuring for each the heat exchange rate to the nitrogen bath. Exchange rate measurements are made in quasistatic regime and during the re-cooling of the wire. SuperOx wires provided with different insulation thicknesses exhibit an excellent stability, far above a bare wire. On the other side, for very thick insulations the stability gain is lost. Re-cooling speeds dependency on insulation thicknesses is measured too. © Published under licence by IOP Publishing Ltd.

Zeugner A.,TU Dresden | Kaiser M.,TU Dresden | Schmidt P.,Brandenburgische Technical University CottbusSenftenberg | Menshchikova T.V.,Tomsk State University | And 8 more authors.
Chemistry of Materials | Year: 2017

Structural engineering of topological bulk materials is systematically explored with regard to the incorporation of the buckled bismuth layer [Bi2], which is a 2D topological insulator per se, into the layered BiTeI host structure. The previously known bismuth telluride iodides, BiTeI and Bi2TeI, offer physical properties relevant for spintronics. Herewith a new cousin, Bi3TeI ( R3m, a = 440.12(2) pm, c = 3223.1(2) pm), joins the ranks and expands this structural family. Bi3TeI = [Bi2][BiTeI] represents a stack with strictly alternating building blocks. Conditions for reproducible synthesis and crystal-growth of Bi2TeI and Bi3TeI are ascertained, thus yielding platelet-like crystals on the millimeter size scale and enabling direct measurements. The crystal structures of Bi2TeI and Bi3TeI are examined by X-ray diffraction and electron microscopy. DFT calculations predict metallic properties of Bi3TeI and an unconventional surface state residing on various surface terminations. This state emerges as a result of complex hybridization of atomic states due to their strong intermixing. Our study does not support the existence of new stacking variants BixTeI with x > 3; instead, it indicates a possible homogeneity range of Bi3TeI. The series BiTeI-Bi2TeI-Bi3TeI illustrates the influence of structural modifications on topological properties. © 2017 American Chemical Society.

Fetisov S.S.,Russian Scientific RandD Cable Institute VNIIKP | Nosov A.A.,Russian Scientific RandD Cable Institute VNIIKP | Zubko V.V.,Russian Scientific RandD Cable Institute VNIIKP | Bykovsky N.V.,Russian Scientific RandD Cable Institute VNIIKP | And 6 more authors.
Journal of Physics: Conference Series | Year: 2014

Recently launched production of 2G wires by SuperOx Company permitted us to start tests of representative models of power cable made of their wires. In Russian Scientific R&D Cable Institute we have the test facility for extensive testing of heavily instrumented HTS cable models with full size cross-section and length up to 5 m. Our standard test program includes critical current measurements, current distribution measurements among layers, AC loss measurements, etc. In this paper we present details of first power cable models made of 4 mm width 2G wires from SuperOx and their test results. Model cables have two counter-wound layers with 18 tapes in each layer. Critical currents of cables were from 3 kA to ∼4.5 kA. We also measured AC losses and compared them with losses in model cables made of 2G wires of other producers. AC losses measured were compared with calculated ones and demonstrated the good coincidence between experiments and calculations. First model cables tests permitted us to conclude that SuperOx wires have good parameters for production of 2G HTS power cables with low AC losses. © Published under licence by IOP Publishing Ltd.

Moyzykh M.,Moscow State University | Samoilenkov S.,Russian Academy of Sciences | Amelichev V.,SuperOx | Vasiliev A.,RAS Research Center Kurchatov Institute | Kaul A.,Moscow State University
Journal of Crystal Growth | Year: 2013

Thin (80-800 nm) epitaxial silicon films on sapphire substrates were deposited via CVD technique and studied with XRD, SEM, EDS, EBSD, HRTEM and AFM methods. Increase of grain size, reduction of microtwin concentration and strong sharpening of crystallographic texture with increasing film thickness was observed. To our knowledge, XRD texture analysis in relation to film thickness of silicon on sapphire samples was performed for the first time. Thickness-dependent behavior of texture quality and film microstructure can be explained by the model of evolutionary selection and disclination formation. © 2013 Elsevier B.V.

Baskys A.,University of Cambridge | Patel A.,University of Cambridge | Hopkins S.C.,University of Cambridge | Kalitka V.,SuperOx | And 4 more authors.
IEEE Transactions on Applied Superconductivity | Year: 2015

(RE)Ba2Cu3O7-δ bulks are well known for their ability to trap high magnetic fields; however, it has been recently shown by the current authors that stacks of commercial YBCO-coated conductor tape can outperform YBCO bulks of similar size at temperatures below 60 K due to their superior thermal stability during multipulse magnetization. The latest progress in a comprehensive study being undertaken to optimize and tailor the stacks for applications will be discussed. In this paper, a method of binding layers of superconducting tape is reported, namely, soldering of Pb-Sn solder-coated high-temperature superconducting tape developed by SuperOx. The performance of tape before and after the soldering procedure is discussed, and a 100-layer stack, trapping a field of up to 1.6 T above the surface after pulse magnetization at 10 K, is reported. © 2014 IEEE.

Patel A.,University of Cambridge | Baskys A.,University of Cambridge | Hopkins S.C.,University of Cambridge | Kalitka V.,SuperOx | And 4 more authors.
IEEE Transactions on Applied Superconductivity | Year: 2015

The potential of (RE)BCO superconducting bulks in rotating machine designs has been explored through numerous experimental prototypes, with the bulks being magnetized to act as field poles. However, stacks of superconducting tapes have emerged as a promising alternative for trapped field magnets partly because of their suitability for the pulsed-field method of magnetization, which is considered the most practical method of trapping flux. The benefits of using a stack of tapes as rotor field poles suitable for motors are reported. The ability to have a long rectangular stack allows for motor designs with more efficient field poles in terms of the flux produced per unit area of the pole and easy scalability. Such a rectangular stack was experimentally magnetized for the first time using a race-track-shaped pulsed-field coil giving a highly uniform and well-defined trapped field. The unique self-supporting 120 mm by 12 mm stack was produced by compressing a high-temperature-superconducting tape coated with a thin layer of solder. Shorter rectangular stacks were pulse magnetized over a temperature range of 10-77 K using a fully automated pulsed magnetization system. © 2002-2011 IEEE.

Rudnev I.,National Research Nuclear University MEPhI | Menushenkov A.,National Research Nuclear University MEPhI | Blednov A.,SuperOx | Chepikov V.,SuperOx | Samoylenkov S.,SuperOx
Journal of Superconductivity and Novel Magnetism | Year: 2016

The results of the study of magnetization of Y1−xCaxBa2Cu3O7−δ HTS films deposited on the metallic substrate are presented. The magnetization measurements were carried out in a wide temperature range 4–77 K and magnetic fields up to 14 T. Based on critical state model, the analysis of the influence of calcium concentration on the critical current was performed. It was found that the change in Ca concentration causes the decrease in value of critical current density jc. The increase in temperature leads to enhancement of the observed effect. At T = 4.2 K and in the magnetic fields higher than 8 T, the jc reduction was found to be insignificant. This fact may indicate the possibility of jc growth in strong magnetic fields due to increase in carrier concentration caused by replacing Y3+ by Ca2+. © 2015, Springer Science+Business Media New York.

Kaul A.R.,SuperOx | Samoilenkov S.V.,SuperOx | Amelichev V.A.,SuperOx | Dosovitsky G.A.,SuperOx | And 7 more authors.
Physics Procedia | Year: 2012

In this article we summarize our results on the fabrication process of the Ni-Cr-W biaxially textured tape, which is non-magnetic at 77 K. The deposition processes of the buffer and HTS layers by reel-to-reel MOCVD technology are described as well. The HTS wire is finished with reel-to-reel depositions of the silver protective layer by magnetron sputtering and copper stabilizing layer by electroplating. Sharp cubic texture with in-plane and out-of-plane misorientation below 7 degrees and low surface roughness (Ra < 5 nm on 5∗5 μm2 area) have been achieved on reeltoreel processed metallic tapes. The texture characteristics of the MgO buffer layer (δRD = 6.0°, δTD = 9.0°, ΔφTRUE = 5.2 °) have been found to be very close to those of the textured substrate tape. Using this structure with additional buffer layers we have succeeded in growing superconducting YBCO coatings with Ic (77 K, s.f.) values higher than 120 A per cm of the tape width at the HTS layer thickness of about 1 μm. © 2012 Published by Elsevier B.V. Selection and/or peer-review under responsibility of the Guest Editors.

Martynova I.,Moscow State University | Tsymbarenko D.,Moscow State University | Kamenev A.,SuperOx | Amelichev V.,SuperOx | And 3 more authors.
Materials Research Bulletin | Year: 2016

Chemical solution deposition of smooth amorphous Al2O3 thin films has been successfully used for planarization of long-length metallic substrates for 2G HTS superconducting wires production. A series of metal-organic precursors based on Al(iPrO)3, Al(acac)3, acetic acid, monoethanolamine (MEA) and diethylenetriamine (DETA) was developed. Correlations between the precursor composition and the features of its two-step thermal-induced transformation to amorphous Al2O3 were studied by 1H NMR, IR spectroscopy and thermal analysis. Utilizing the solutions of {Al(iPrO)3 + 2.5MEA + 6HAcet} in iPrOH and {Al(acac)3 + nDETA} in HAcet (n = 1 - 3) as precursors for dip-coating, we obtained the long-length Hastelloy C276 substrate covered by uniform amorphous 50-550 nm thick alumina films with surface roughness of about 0.5-1.5 nm. A 20 m long sample of 2G HTS wire with a commercial level of superconducting critical current of up to 300 A was prepared based on Hastelloy substrate tape planarized with Al2O3. © 2016 Elsevier Ltd. All rights reserved.

Martynova I.,Moscow State University | Tsymbarenko D.,Moscow State University | Kamenev A.,SuperOx | Kuzmina N.,Moscow State University | Kaul A.,Moscow State University
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2014

The Solution Deposition Planarization method was successfully used for smoothing Ni-alloy tapes with initial surface roughness of 26.7 nm (on 40×40 μm2 area) and 12.6 nm (on 5×5 μm2 area). New precursor solutions were prepared from yttrium acetate and diethylenetriamine or ethylenediamine in MeOH and i-PrOH - alcohols with different viscosities. Using those solutions yttria films with the residual roughness Sa=0.4 nm (on 5×5 μm2 area) and Sa=7.6 nm (on 40×40 μm2 area) were deposited on the Ni-alloy tapes. © 2013 Elsevier B.V.

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