Pavel Nikolaevich Degtyarenko

The study of the 12-mm-wide 2G HTS wires with gadolinium excess is presented. The GdBCO layer was grown by pulsed laser deposition using commercial production equipment and contained different concentration of Gd: pristine sample, +15%, +30%, and +45% of Gd contents. The samples were characterized by transport measurements over wide temperature (T) and magnetic field (B) ranges. The microstructure investigations were carried out by scanning transmission electron microscopy. The resistivity curves of the samples were measured in the field up to 9 T. We determined that the irreversibility temperature (T_irr) derived from these curves is maximum in case of B‖ab. Irreversibility temperature has been decreased with increasing of applied magnetic field from 0 to 3 Т and that confirmed by measurements of the resistivity transition as imaginary part of magnetic susceptibility (χ”). The maximum of T_irr obtained in the experiments indicate a different pinning structure mechanism in the studied samples.

Проведены систематические исследования ВТСП-лент второго поколения, облученных высокоэнергетичными ионами Xe с энергией 167 МэВ и флюенсами до 1 ・ 1012 см-2. Определено оптимальное значение флюенса (количества частиц, прошедших через 1 см2 поверхности образца) для получения максимального критического тока при различных температурах и внешних магнитных полях. Увеличение внешнего магнитного поля приводит к смещению пика критического тока в сторону больших значений флюенсов во всем диапазоне температур. Приводятся результаты микроструктурных исследований методами просвечивающей/растровой электронной микроскопии и рентгеновской дифракции. Показано, что в результате облучения образуются ионные треки диаметром порядка 5–8 нм, выступающие в роли эффективных центров пиннинга. Рентгеноструктурный анализ свидетельствует о снижении остроты текстуры под воздействием облучения.

The investigation results of magnetization, dynamic magnetic susceptibility and microstructure of samples of second generation high-temperature superconduc

Industrial 2G HTS wires optimized for low-temperature application are studied using XRD. We aim at understanding the origin of noticeable variation of the lift factor LF = J _c (20K, 8T)/ J _c (77 K, sf) with the final goal of narrowing down the statistical scatter of the performance in production wires. Two approaches are used - (1) the direct characterization of Y123 defect state through analysis of diffuse scattering effects and (2) quantification of YBCO nanostructure (contents of Y ₂ O ₃ precipitates, their size, strain state of Y ₂ O ₃ precipitates and Y123 matrix). Only weak correlations between the parameters extracted from XRD patterns and J _c (20K, 8T) have been found. A rather complex strain state of Y123 with out-of-plane tension, anisotropic in-plane compression, and (likely) overall contraction is observed. Further plans are discussed.

The changes in the superconducting properties of high-temperature superconducting tapes of the second generation within a wide range of temperatures and ap

The production of second-generation long-length high-temperature superconducting wires (2G HTS) greatly simplifies the construction of electrical devices based on them. In turn, the performance of 2G HTS is highly dependent on the manufacturing process, architecture, and materials on which they are produced. Particularly important in the process of industrial 2G HTS development is the addition of doping additives to reduce the anisotropy of the current-carrying capacity. In this work, the current-carrying capacity I _c (T, B, θ) of industrial 2G HTS samples with different deposition rate and concentration of BaSnO3 - 6 mol.% doping additives were measured in fields up to 9 T and at temperatures 65 and 77 K. Experimental measurements were carried out at various orientations of an external magnetic field of up to 1 T relative to the sample plane. It was found that the change of sputtering velocity leads to the decrease of current-carrying capacity at 77 K. The influence of the microstructural characteristics of the artificial pinning centers on the electrophysical parameters was considered.

Systematic studies of second-generation high-temperature superconducting wires with Gd excess relative to the stoichiometric GdBa2Cu3O7composition are reported. It has been revealed that filamentary defects in the form of non-superconducting Gd2CuO4phase located along the ab plane are formed during film growth. These inclusions lead to a change in the pinning mechanism of the vortex structure, due to which the peak of the critical current at +15% Gd is clearly observed.

Systematic studies of second-generation high-temperature superconducting wires with Gd excess relative to the stoichiometric GdBa₂Cu₃O₇ composition are reported. It has been revealed that filamentary defects in the form of non-superconducting Gd₂CuO₄ phase located along the ab plane are formed during film growth. These inclusions lead to a change in the pinning mechanism of the vortex structure, due to which the peak of the critical current at +15% Gd is clearly observed.

Bimetallic FeCo and FeNi nanoparticles attract much attention due to their promising magnetic properties and a wide range of practical applications as recording and storage media, catalytic systems in fuel cells, supercapacitors, lithium batteries, etc. In this paper, we propose an original approach to the preparation of FeCo- and FeNi/N-doped carbon nanocomposites by means of a coupled process of frontal polymerization and thermolysis of molecular co-crystallized acrylamide complexes. The phase composition, structure, and microstructure of the resulting nanocomposites are studied using XRD, IR spectroscopy, elemental and thermal analysis, and electron microscopy data. The main magnetic characteristics of the synthesized nanocomposites, including the field dependences and the ZFC-FC curves peculiarities, are studied. It is shown that the obtained FeCo/N-C nanocomposites exhibit exchange bias behavior at low temperatures. In turn, FeNi/N-C nanocomposites are ferromagnetically ordered.

Numerical calculations of parameters of an electrical power network where an HTS fuse is used as a fault current limiting device have been done. The calculations were performed for networks containing different types of HTS cables as well. The design of HTS fuse was developed based on the numerical calculation for the network-rated parameters considering the special types 2G HTS tape characteristics. The distinctive feature of these tapes is the minimal thickness (about 30 µm) of the substrate at the critical current 450–600 A. The tests were performed at a voltage of 1 kV and demonstrated the ability of circuit breaking at fault currents about 3–4 kA. A comparison of experimental results with the calculations allows us to conclude that the HTS fuse of this design can operate as a fault current limiting device in electrical power networks at various rated voltage levels.