V.V. Sergeev

Bochvar Research Institute of Inorganic Materials, Moskva, Moscow, Russia

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Publications (6)5.66 Total impact

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    ABSTRACT: The current carrying capacity of different design internal tin strands at high magnetic fields was investigated. Two high critical current density internal tin Nb<sub>3</sub>Sn strands with different level of mechanical properties have been designed. The increase of mechanical strength has been attained by replacing part of the stabilizing copper by strengthening elements made of “in situ” nanocomposite Cu-Nb rods. The analysis of the mechanical properties of the strands in virgin state and after the reaction heat treatment has been done. The microstructure of strands components including Nb<sub>3</sub>Sn filaments has been investigated. The results of current carrying capacity measurements of 0.6 mm diameter strands in magnetic fields up to 20 T (4.2 K; 0.1 μV/cm) and hysteresis losses measurements (± 3 T cycles) are presented. It was shown that for the strand with enhanced mechanical strength the non-Cu critical current densities attained were 2580 A/mm<sup>2</sup> and 235 A/mm<sup>2</sup> at 12 T and 20 T, respectively, and for the strand without strengthening elements the non-Cu critical current densities were equal to 2250 A/mm<sup>2</sup> and 500 A/mm<sup>2</sup> at 12 T and 20 T, respectively. The correlation between the microstructure and superconducting properties of the different strands designs are discussed.
    IEEE Transactions on Applied Superconductivity 07/2011; 21(3-21):2575 - 2578. DOI:10.1109/TASC.2011.2113311 · 1.32 Impact Factor
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    ABSTRACT: The layout optimization of ITER-type Nb3Sn internal tin (IT) superconducting strand for magnet systems of future fusion reactors was carried out aiming on the large scaled industrial production. The new approach to a formation of the initial composite billets for fabrication of IT superconducting strand has been proposed. This approach assumes the use of round shaped instead of hexagonal shaped Cu-Nb subelements covered by tin layers. The positive influence of the use of round shaped multifilamentary Cu-Nb subelements on the uniformity of filaments array in the final strands has been shown. The investigation on the use of composite filaments consisting of multiple niobium rods and rods made from NbTi alloy was carried out. It was shown that the use of proposed composite filaments enabled to effectively regulate the grain size of niobium in Cu-Nb subelements before the cold deformation by drawing. The experimental data on the influence of the proposed composite design of the filaments on the kinetics of Nb3Sn layer formation process are given. The relations of microstructure and properties of Nb3Sn IT strand with modified design have been analyzed. The superconducting properties attained met the main ITER requirements for the TF strands with non-copper critical current density higher than 800 A/mm2 (4.2 K; 12 T) and hysteresis losses (±3 T) less than 500 mJ/cm3.
    Journal of Physics Conference Series 07/2010; 234(2):022037. DOI:10.1088/1742-6596/234/2/022037
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    ABSTRACT: Addition of manganese in elements of matrix for internal-tin Nb<sub>3</sub>Sn strands has been investigated. Two types of multifilamentary strands with distributed source of tin, 1.8 wt.% Mn in elements of matrix before reaction heat treatment and 1 wt.% Mn in matrix after reaction, have been fabricated by internal-tin method. One of the produced strands had reinforced stabilizer from CuNb nanocomposite alloy. The increase of Nb<sub>3</sub>Sn layer growth rate in superconductors filaments of manganese doped strands was determined. Microstructures of Nb<sub>3</sub>Sn filaments after reaction heat treatment were investigated by SEM and TEM microscopes. The critical current density in magnetic fields up to 20 T, hysteresis losses, critical temperature and mechanical characteristics were measured. The increase of critical current density in internal-tin Nb<sub>3</sub>Sn strands with manganese doped matrix and the formation of fine microstructure Nb<sub>3</sub>Sn layers was revealed.
    IEEE Transactions on Applied Superconductivity 07/2009; 19(3-19):2560 - 2563. DOI:10.1109/TASC.2009.2018032 · 1.32 Impact Factor
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    ABSTRACT: Results of a study of promising Nb3Sn superconductors fabricated with the use of a “bronze” method and a method of “internal source of tin” for toroidal coils of the magnet system of the international thermonuclear experimental reactor (ITER) are presented. The main structural parameters and factors of the process of manufacturing technical superconductors based on Nb3Sn, which determine the superconducting properties, are analyzed. The current-carrying capacity and the losses to hysteresis are determined for conductors with various diameters. The structure of the layer of superconducting Nb3Sn compound is studied, and the relation between the structural parameters and the superconducting properties of the developed conductors is described. Examples of Nb3Sn superconductors with a reinforcing element from a nanocomposite alloy Cu - 18% Nb are presented. Strength characteristics of the reinforced conductors are studied. Prospects of further enhancement of superconducting properties of Nb3Sn superconductors obtained by both methods are estimated.
    Metal Science and Heat Treatment 11/2004; 46(11):504-513. DOI:10.1007/s11041-005-0010-x · 0.36 Impact Factor
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    ABSTRACT: The magnetic field (in range 5-12 T) and temperature dependencies (in range 4.2-12 K) of the transport current density J<sub>c</sub>(B, T) and temperature dependence of upper critical field B<sub>c2</sub>(T) in internal-tin multifilamentary wires are presented. The Summers relations have been applied for evaluation of the experimental J<sub>c</sub>(T) and B<sub>c2</sub>(T) data. The fitting parameters C, T<sub>cm</sub>(0), and B<sub>c2m</sub>(0) has been defined as giving the best fit to the experimental data. The microstructure of Nb<sub>3</sub>Sn filaments has been investigated by SEM. The particular features of the diffusion processes in internal tin wires lead to formation of the specific Nb<sub>3</sub>Sn filaments microstructure associated with high critical current density which have been analyzed.
    IEEE Transactions on Applied Superconductivity 07/2004; DOI:10.1109/TASC.2004.830366 · 1.32 Impact Factor
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    ABSTRACT: Nb<sub>3</sub>Sn superconductors with Cu-stabilization partly replaced by Cu-18 wt% Nb reinforcing layer have been developed and produced. The comparative analysis of superconductors with and without such layer was done. The level of ultimate tensile strength in reacted reinforced wire was higher by the factor of 1.4. Results of metallographic investigations of the reaction of Sn with Cu-matrix during heat treatment are presented. The current capacity of superconductors and "n" parameter have been estimated in magnetic field of 12 T at 4.2 K. Conductors microstructure has been studied and relationship with mechanical and superconducting properties has been discussed.
    IEEE Transactions on Applied Superconductivity 07/2004; 14(2-14):996 - 999. DOI:10.1109/TASC.2004.830365 · 1.32 Impact Factor