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V.r. Romanovskii - One of the best experts on this subject based on the ideXlab platform.
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Degradation of the Current-Carrying Capacity of low-temperature superconducting composites under the action of thermal perturbations
Technical Physics, 2016Co-Authors: V.r. RomanovskiiAbstract:The stability of transport Current introduced into a niobium titanium superconducting composite subjected to an external pulsed thermal perturbation has been studied. Stable states have been theoretically analyzed by solving Fourier and Maxwell equations that describe the thermoelectrodynamic states of lowtemperature superconductors with flux creep. It has been shown that, if the transport Current is permanently introduced, subcritical thermal perturbations, i.e., perturbations that do not take the composite to a normal state provided that the Current does not exceed the quench Current, may result in the appearance of unstable Current states. The higher the energy of the external thermal perturbation, the lower the instability onset Current. It has been found that the degradation of the Current-Carrying Capacity of the superconducting composite is due to intense heat release inside the superconductor, which is initiated by the thermal perturbations, and depends on the Current input rate, the instant of time the Current input is terminated, and cooling conditions.
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Current-Carrying Capacity dependence of composite Bi 2 Sr 2 CaCu 2 O 8 superconductors on the liquid coolant conditions
Superconductor Science and Technology, 2006Co-Authors: V.r. Romanovskii, K. Watanabe, Satoshi Awaji, NishijimaAbstract:The thermal runaway conditions of the composite Bi2Sr2CaCu2O8 superconductor cooled by liquid helium or liquid hydrogen are compared. The study based on the static analysis of thermoelectric modes was made when the volume fraction of the superconductor in a composite was varied. Some specific trends underlying the onset of thermal runaway in superconducting composites cooled by liquid coolants are discussed. It is stated that the operating modes of superconducting composites may be characterized by stable states during which the Current-Carrying Capacity of a superconductor is not effectively used even with a high amount of superconductor in the composite. These states are possible due to the corresponding temperature variation of the resistivities of the matrix and the superconductor in the high operating temperature range. They have to be considered in experiments when the critical Current of a superconductor is determined or when the optimal stable operating modes of the Current-Carrying elements based on the Bi2Sr2CaCu2O8 superconductor, which is cooled by liquid coolant, are defined.
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Limiting Current-Carrying Capacity of Ag-sheathed Bi2Sr2CaCu2O8 conductors: linear approximation
Superconductor Science and Technology, 2004Co-Authors: V.r. Romanovskii, K. Watanabe, Satoshi Awaji, Nishijima, K. TakahashiAbstract:The Current-Carrying Capacity of the Ag/Bi2Sr2CaCu2O8 multifilament conductor is studied in detail as a function of the heat transfer coefficient, resistivity of the matrix, and volume fraction of the superconductor. The thermal runaway parameters corresponding to the irreversible superconducting-to-normal transition are derived analytically under the aspect of possible finite temperature rise of the composite conductor before thermal runaway. The static analytical model determines the thermal runaway parameters. The power law describes the voltage–Current characteristic of a superconductor with a linear temperature dependence of the critical Current (linear approximation). The performed analysis reveals that the allowable magnitude of the Current and electric field before the thermal runaway may be higher than those determined by the criterion Ec = 10−6 V cm−1 in many practical cases. The condition of the stable state for the over-critical Current is formulated and the peculiarities of such operation regimes are discussed. It is shown that the essential stationary overheating of the superconductor may occur before the thermal runaway. The minimum value of the Current at which the thermal runaway starts is found if the volume fraction of superconductor in the composite is changed.
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Current Carrying Capacity reduction in superconducting multi-strand cable with different smoothness of voltage-Current characteristics of strands
Cryogenics, 1997Co-Authors: V.r. Romanovskii, A.v. GavrilinAbstract:The results are presented of a theoretical analysis of reasons for reduction of Current Carrying Capacity in superconducting multi-strand cable with thermally insulated strands at linearly changing transport Current of the cable. The voltage-Current characteristics (VCC) of strands are assumed to be described by the exponential function independent variables of Current density and temperature, and to diverge somewhat. The conditions of origination of thermomagnetic instabilities preceding the quench in the cable are determined by means of numerical solution of the set of transient equations of heat balance and circuits governing each strand temperature change in time and the Current redistribution throughout inductively coupled strands. It is shown that the quench Current of the cable decreases with an increase in the smoothness factor of a strand's VCC. For cables with a great quantity of strands, a tangible decrease of the cable quench Current could be unavoidable even if the grade of a bare percentage of strands has been going downward, and the cable Current Carrying Capacity normalized to the total number of strands could be wittingly less than that of one sound strand.
Nishijima - One of the best experts on this subject based on the ideXlab platform.
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Current-Carrying Capacity dependence of composite Bi 2 Sr 2 CaCu 2 O 8 superconductors on the liquid coolant conditions
Superconductor Science and Technology, 2006Co-Authors: V.r. Romanovskii, K. Watanabe, Satoshi Awaji, NishijimaAbstract:The thermal runaway conditions of the composite Bi2Sr2CaCu2O8 superconductor cooled by liquid helium or liquid hydrogen are compared. The study based on the static analysis of thermoelectric modes was made when the volume fraction of the superconductor in a composite was varied. Some specific trends underlying the onset of thermal runaway in superconducting composites cooled by liquid coolants are discussed. It is stated that the operating modes of superconducting composites may be characterized by stable states during which the Current-Carrying Capacity of a superconductor is not effectively used even with a high amount of superconductor in the composite. These states are possible due to the corresponding temperature variation of the resistivities of the matrix and the superconductor in the high operating temperature range. They have to be considered in experiments when the critical Current of a superconductor is determined or when the optimal stable operating modes of the Current-Carrying elements based on the Bi2Sr2CaCu2O8 superconductor, which is cooled by liquid coolant, are defined.
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Limiting Current-Carrying Capacity of Ag-sheathed Bi2Sr2CaCu2O8 conductors: linear approximation
Superconductor Science and Technology, 2004Co-Authors: V.r. Romanovskii, K. Watanabe, Satoshi Awaji, Nishijima, K. TakahashiAbstract:The Current-Carrying Capacity of the Ag/Bi2Sr2CaCu2O8 multifilament conductor is studied in detail as a function of the heat transfer coefficient, resistivity of the matrix, and volume fraction of the superconductor. The thermal runaway parameters corresponding to the irreversible superconducting-to-normal transition are derived analytically under the aspect of possible finite temperature rise of the composite conductor before thermal runaway. The static analytical model determines the thermal runaway parameters. The power law describes the voltage–Current characteristic of a superconductor with a linear temperature dependence of the critical Current (linear approximation). The performed analysis reveals that the allowable magnitude of the Current and electric field before the thermal runaway may be higher than those determined by the criterion Ec = 10−6 V cm−1 in many practical cases. The condition of the stable state for the over-critical Current is formulated and the peculiarities of such operation regimes are discussed. It is shown that the essential stationary overheating of the superconductor may occur before the thermal runaway. The minimum value of the Current at which the thermal runaway starts is found if the volume fraction of superconductor in the composite is changed.
Alexander A Balandin - One of the best experts on this subject based on the ideXlab platform.
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graphene on diamond devices with increased Current Carrying Capacity carbon sp2 on sp3 technology
Nano Letters, 2012Co-Authors: Jie Yu, Anirudha V Sumant, V Goyal, Alexander A BalandinAbstract:Graphene demonstrated potential for practical applications owing to its excellent electronic and thermal properties. Typical graphene field-effect transistors and interconnects built on conventional SiO2/Si substrates reveal the breakdown Current density on the order of 1 μA/nm2 (i.e., 108 A/cm2), which is ∼100× larger than the fundamental limit for the metals but still smaller than the maximum achieved in carbon nanotubes. We show that by replacing SiO2 with synthetic diamond, one can substantially increase the Current-Carrying Capacity of graphene to as high as ∼18 μA/nm2 even at ambient conditions. Our results indicate that graphene’s Current-induced breakdown is thermally activated. We also found that the Current Carrying Capacity of graphene can be improved not only on the single-crystal diamond substrates but also on an inexpensive ultrananocrystalline diamond, which can be produced in a process compatible with a conventional Si technology. The latter was attributed to the decreased thermal resistan...
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graphene on diamond devices with enhanced Current Carrying Capacity carbon sp2 on sp3 technology
arXiv: Materials Science, 2012Co-Authors: Guanxiong Liu, Anirudha V Sumant, V Goyal, Alexander A BalandinAbstract:Graphene demonstrated potential for practical applications owing to its excellent electronic and thermal properties. Typical graphene field-effect transistors and interconnects built on conventional SiO2/Si substrates reveal the breakdown Current density on the order of 1 uA/nm2 (i.e. 10^8 A/cm2) which is ~100\times larger than the fundamental limit for the metals but still smaller than the maximum achieved in carbon nanotubes. We show that by replacing SiO2 with synthetic diamond one can substantially increase the Current-Carrying Capacity of graphene to as high as ~18 uA/nm2 even at ambient conditions. Our results indicate that graphene's Current-induced breakdown is thermally activated. We also found that the Current Carrying Capacity of graphene can be improved not only on the single-crystal diamond substrates but also on an inexpensive ultrananocrystalline diamond, which can be produced in a process compatible with a conventional Si technology. The latter was attributed to the decreased thermal resistance of the ultrananocrystalline diamond layer at elevated temperatures. The obtained results are important for graphene's applications in high-frequency transistors, interconnects, transparent electrodes and can lead to the new planar sp2-on-sp3 carbon-on-carbon technology.
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Graphene-diamond-silicon devices with increased Current-Carrying Capacity: sp 2 -Carbon-sp 3 -Carbon-on-Silicon technology
2012 IEEE Silicon Nanoelectronics Workshop (SNW), 2012Co-Authors: Guanxiong Liu, Anirudha V Sumant, Alexander A BalandinAbstract:Graphene demonstrated potential for practical applications owing to its excellent electronic and thermal properties. Typical graphene field-effect transistors (FETs) and interconnects built on conventional SiO 2 /Si substrates reveal the breakdown Current density on the order of 108 A/cm2, which is ∼100× larger than the fundamental limit for the metals but still smaller than the maximum achieved in carbon nanotubes. It was discovered by some of us that graphene has excellent thermal conduction properties with the thermal conductivity K exceeding 2000 W/mK at room temperature [1]. Few-layer graphene largely preserves the heat conduction properties [2]. However, the thermally resistive SiO 2 , with the thermal conductivity in the range from 0.5 to 1.4 W/mK, creates a bottleneck for heat removal. The latter does not allow graphene to demonstrate its true Current-Carrying potential. We show that by replacing SiO 2 with synthetic diamond one can substantially increase the Current-Carrying Capacity of graphene to as high as ∼ 20×108 A/cm2 under ambient conditions. The two-terminal and three-terminal top-gated graphene devices (see Figure 1) were fabricated on synthetic single-crystal diamond (SCD) and ultrananocrystalline diamond (UNCD). To ensure Si integration, the UNCD layers were grown at low temperatures compatible with Si CMOS technology [3]. Our results indicate that graphene's Current-induced breakdown is thermally activated. It was found that the Current Carrying Capacity of graphene can be improved not only on SCD but also on an inexpensive UNCD. The latter was attributed to the decreased thermal resistance of UNCD at elevated temperatures (see Figure 2). The obtained results are important for graphene's hetero-integration on Si substrates. The enhanced Current-Carrying Capacity is beneficial for the proposed applications of graphene in interconnects and high-frequency transistors.
S I Savchenko - One of the best experts on this subject based on the ideXlab platform.
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Nb-Ti superconductors of a high Current-Carrying Capacity
Superconductor Science and Technology, 1991Co-Authors: O. V. Chernyj, G F Tikhinskij, G E Storozhilov, M. B. Lazareva, L A Kornienko, N F Andrievskaya, V V Slezov, V V Sagalovich, Ya D Starodubov, S I SavchenkoAbstract:The effect of multiple prolonged heat treatment on the structure and critical Current density in Nb-50 wt.% Ti composites was studied in the case of monofilamentary superconductors. The treatment temperature range, in which high Jc values can be obtained, is determined. The influence of intermediate treatments on the increase in the quantity of precipitated alpha -phase is studied. The exponent specifying the kinetics of particle growth from the supersaturated solid solution is estimated. The interrelation between the critical Current density and the quantity of precipitated phase is established. The maximum critical Current density is 4*105 A cm-1 (B=5 T).
Pingxiang Zhang - One of the best experts on this subject based on the ideXlab platform.
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strongly improved Current Carrying Capacity induced by nanoscale lattice strains in yba2cu3o7 δ ba0 7sr0 3tio3 composite films derived from chemical solution deposition
Journal of Materials Chemistry C, 2016Co-Authors: Li Lei, Lu Liu, Xiuting Wang, Shasha Wang, Jiqiang Jia, Gaoyang Zhao, Lihua Jin, Pingxiang ZhangAbstract:It is commonly expected that YBa2Cu3O7−δ (YBCO) coated conductors can exhibit strong vortex pinning force when they are used at high temperature (77 K) and different magnetic field orientations which are angled to the YBCO c-axis. In this paper, we showed a simple approach, making a YBCO film to epitaxially grow on the Ba0.7Sr0.3TiO3 (BST) microarray buffered LaAlO3 (LAO) substrate, to introduce nanoscale crystalline defects into the YBCO matrix. High concentration nanodefects including dislocations, intergrowths, stacking faults and plane buckling have been observed by high-resolution transmission electron microscopy (HRTEM). It was demonstrated through magnetization vs. magnetic field strength measurement that these nanodefects could provide quasi-isotropic vortex pinning characteristic of the so-called nanostructured YBCO films, containing large numbers of defects, which would promote power applications of coated conductors. It is believed that non-superconductivity regions (the dimension is close to the order of ξ, the coherence length of YBCO) caused by nanodefects are considered as effective pinning centers to inhibit flux creep. Therefore, large pinning energy can be easily obtained for YBCO films if considerable nanodefects are introduced into the epitaxial YBCO matrix no matter which method is employed to produce the nanostructured YBCO film. We illustrated the essential reason for the strong enhancement of the critical Current density of the YBCO film under both self- and applied magnetic fields, that is, lattice strains (elongated and shortened Cu–O bonds) caused by crystalline nanodefects lead to the distinctly improved Current-Carrying Capacity of the YBCO film.
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Strongly improved Current-Carrying Capacity induced by nanoscale lattice strains in YBa2Cu3O7−δ–Ba0.7Sr0.3TiO3 composite films derived from chemical solution deposition
Journal of Materials Chemistry C, 2016Co-Authors: Li Lei, Lu Liu, Xiuting Wang, Shasha Wang, Jiqiang Jia, Gaoyang Zhao, Lihua Jin, Pingxiang ZhangAbstract:It is commonly expected that YBa2Cu3O7−δ (YBCO) coated conductors can exhibit strong vortex pinning force when they are used at high temperature (77 K) and different magnetic field orientations which are angled to the YBCO c-axis. In this paper, we showed a simple approach, making a YBCO film to epitaxially grow on the Ba0.7Sr0.3TiO3 (BST) microarray buffered LaAlO3 (LAO) substrate, to introduce nanoscale crystalline defects into the YBCO matrix. High concentration nanodefects including dislocations, intergrowths, stacking faults and plane buckling have been observed by high-resolution transmission electron microscopy (HRTEM). It was demonstrated through magnetization vs. magnetic field strength measurement that these nanodefects could provide quasi-isotropic vortex pinning characteristic of the so-called nanostructured YBCO films, containing large numbers of defects, which would promote power applications of coated conductors. It is believed that non-superconductivity regions (the dimension is close to the order of ξ, the coherence length of YBCO) caused by nanodefects are considered as effective pinning centers to inhibit flux creep. Therefore, large pinning energy can be easily obtained for YBCO films if considerable nanodefects are introduced into the epitaxial YBCO matrix no matter which method is employed to produce the nanostructured YBCO film. We illustrated the essential reason for the strong enhancement of the critical Current density of the YBCO film under both self- and applied magnetic fields, that is, lattice strains (elongated and shortened Cu–O bonds) caused by crystalline nanodefects lead to the distinctly improved Current-Carrying Capacity of the YBCO film.
