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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Investigation on Effect of Magnetic Field Dependency Coefficient of Critical Current Density on the AC Magnetizing Loss in HTS Tapes Exposed to External Field

High-temperature superconducting (HTS) technology is the most promising, advanced, and beneficial technological developments of the last two decades in terms of fabricating more efficient, compact, and reliable electrical power apparatus. The second-generation HTS wires are now quite competitive with traditional conductors from the cost point of view. In addition, they are of high interest in electrical machine manufacturing due to their unique merits such as high current density, high magnetic field, and low loss. The most significant issue for any superconducting devices which work with alternating current or magnetic field is the AC loss of the HTS tapes. Since HTS tapes are always exposed to an external magnetic field in electrical machine applications, it is vital to consider the effect of this external field on their AC magnetizing (ACMG) loss. It is well-known that external magnetic field decreases the current carrying capability of the wire. In real life, critical current density of HTS tapes is dependent to magnetic field but this dependency sometime was not considered in modeling stage in order to make it faster and simple. In this paper, the electromagnetic properties of HTS tapes for use in superconducting electric machines have been investigated with a particular focus on the ACMG loss of YBCO tapes. For this purpose, a two-dimensional finite element model has been implemented based on the H formulation in order to study the effect of dependency of critical current density to magnetic field on the variation of ACMG loss. The modeling results will be helpful for electrical machine designers to have a better understanding about this effect and have a more accurate estimate of ACMG loss in design stage.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

The Influence of High Isostatic Pressure on Critical Current Density in C-Doped MgB{sub 2} Wires

This article reports the influence of isostatic pressure (from 0.1 MPa to 1.1 GPa), low annealing temperature of 570 {sup ∘}C, and annealing time for the formation of high-field pinning centers in 2% C-doped MgB{sub 2} wires. Measurements indicate that 1.1 GPa pressure significantly increases the density of high-field pinning centers below 20 K. However, lower pressure (0.6 GPa) slightly increases the density of high-field pinning centers. Increasing the annealing time from 120 to 210 min leads to a reduction of critical temperature (T{sub c}), irreversibility field (B{sub irr}), critical current density (J{sub c}), and upper critical field (B{sub c2}), suggesting that a long annealing time leads to a reduction of high-field pinning center density and the number of connections between superconducting grains. The high pressures and low annealing temperature lead to a high critical current density of 1000 A/mm{sup 2} in 7.2 T and 100 A/mm{sup 2} in 12.5 T at 4.2 K in MgB{sub 2} wires.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Effect of Y{sub 2}BaCuO{sub 5} Nanoparticle Doping on Critical Current Density of YBa{sub 2}Cu{sub 3}O{sub 7-δ} Bulk Superconductor

This study presents the effect of Y{sub 2}BaCuO{sub 5} (Y211) nanoparticle doping on critical current density and critical temperature of YBa{sub 2}Cu{sub 3}O{sub 7-δ} (YBCO) superconductor. Y211 nanoparticles with different particle sizes ranging from 34 to 455 nm were synthesized by a sol-gel method, then doped into the YBCO superconductor by 0.5, 1, and 2 wt.%. Samples were characterized using X-ray diffraction and scanning electron microscope measurements. The standard four-probe technique was used to measure the critical current density at 77 K. The results showed that in the all-doped samples, critical current density was higher than that of the pure sample. It was found that in the samples containing 1 and 2 wt.% of Y211 nanoparticles, by increasing the size of nanoparticles, the J{sub c} was increased, but in samples containing 0.5 wt.%, the J{sub c} decreased. The maximum critical current density of 64 A/cm {sup 2} was obtained for the samples doped with 2 wt.% of 455 nm Y211 nanoparticles. Also, it was observed that the critical temperature slightly decreased with nanoparticle doping.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Ultrahigh critical current densities, the vortex phase diagram, and the effect of granularity of the stoichiometric high-T c superconductor CaKFe 4 As 4

We present a comprehensive study of the critical current densities and the superconducting vortex phase diagram in the stoichiometric superconductor CaKFe 4 As 4 which has a critical temperature of ~35 K. We performed detailed magnetization measurements both of high quality single crystals for different orientations in an applied magnetic field up to 16 T and for a powder sample. We find an extremely large critical current density, J c , up to 10 8 A/cm 2 for single crystals when H∥(ab) at 5 K, which remains robust in fields up to 16 T, being the largest of any other iron-based superconductor. The critical current density is reduced by a factor 10 in single crystals when H∥c at 5 K and significantly suppressed by the presence of grain boundaries in the powder sample. We also observe the presence of the fishtail effect in the magnetic hysteresis loops of single crystals when H∥c. The flux pinning force density and the pinning parameters suggest that the large critical current could be linked to the existence of point core and surface pinning. Based on the vortex phase diagram and the large critical current densities, CaKFe 4 As 4 is now established as a potential iron-based superconductor candidate for practical applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Evidence from EXAFS for Different Ta/Ti Site Occupancy in High Critical Current Density Nb 3 Sn Superconductor Wires

To meet critical current density, Jc, targets for the Future Circular Collider (FCC), the planned replacement for the Large Hadron Collider (LHC), the high field performance of Nb 3 Sn must be improved, but champion J c values have remained static for the last 10 years. Making the A15 phase stoichiometric and enhancing the upper critical field H c2 by Ti or Ta dopants are the standard strategies for enhancing high field performance but detailed recent studies show that even the best modern wires have broad composition ranges. To assess whether further improvement might be possible, we employed EXAFS to determine the lattice site location of dopants in modern high-performance Nb 3 Sn strands with J c values amongst the best so far achieved. Although Ti and Ta primarily occupy the Nb sites in the A15 structure, we also find significant Ta occupancy on the Sn site. These findings indicate that the best performing Ti-doped stand is strongly sub-stoichiometric in Sn and that antisite disorder likely explains its high average H c2 behavior. These new results suggest an important role for dopant and antisite disorder in minimizing superconducting property distributions and maximizing high field J c properties.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Influence of Critical Current Density Distribution on Transport AC Losses in Superconducting Wire in a DC Magnetic Field

In typical application-like conditions, the inhomogeneous distribution and anisotropy of critical current density must be considered simultaneously in transport AC loss calculation. In this paper, we derive the analytical formulas of transport AC losses for high-temperature superconductors (HTSs) with linear and quadratic distribution of critical current density under applied DC magnetic field. The influence of the inhomogeneous distribution and anisotropy of critical current density has been analyzed. The results show that the impact of the distribution form on transport AC loss is more obvious under applied DC magnetic field. And the influence of applied DC magnetic field will increase as the distribution form becomes steeper.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Semi-solid alkali metal electrodes enabling high critical current densities in solid electrolyte batteries

The need for higher energy density rechargeable batteries has generated interest in alkali metal electrodes paired with solid electrolytes. However, metal penetration and electrolyte fracture at low current densities have emerged as fundamental barriers. Here, we show that for pure metals in the Li-Na-K system, the critical current densities scale inversely to mechanical deformation resistance. Furthermore, we demonstrate two electrode architectures in which the presence of a liquid phase enables high current densities while preserving the shape retention and packaging advantages of solid electrodes. First, biphasic Na-K alloys show K + critical current densities (with K-β*-Al 2 O 3 electrolyte) that exceed 15 mA∙cm -2 . Second, introducing a wetting interfacial film of Na-K liquid between Li metal and Li 6.75 La 3 Zr 1.75 Ta 0.25 O 12 (LLZTO) solid electrolyte doubles the critical current density and permits cycling at areal capacities exceeding 3.5 mAh∙cm -2 . These design approaches hold promise for overcoming electro-chemo-mechanical stability issues that have heretofore limited performance of solid-state metal batteries.

25 ENERGY STORAGE↗
DOE OSTI2019

Effect of Inclusions on Magnetostriction in Superconducting Cylinder with Exponential Distribution of Critical-Current Density

The magnetoelastic behaviour subjected to the electromagnetic body force induced by flux pinning is studied with Kim model for zero-field cooling (ZFC) magnetization process, in which the non-uniform parameter η is considered for inclusion-superconducting matrix system. For superconducting composites, the effect of inhomogeneous distribution of critical current density on effective magnetostriction is also obtained based on the plane strain approach. The results show that the exponential distribution of critical-current density will lead to a larger trapped field and magnetostriction inside the inhomogeneous sample, which also means that it is worthwhile to investigate the magnetoelastic problem of bulk superconductors with inhomogeneous distribution of critical-current density.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Over 15 MA/cm2 of critical current density in 4.8 µm thick, Zr-doped (Gd,Y)Ba2Cu3Ox superconductor at 30 K, 3T

An Advanced MOCVD (A-MOCVD) reactor was used to deposit 4.8µm thick (Gd,Y)BaCuO tapes with 15mol% Zr addition in a single pass. A record-high critical current density (Jc) of 15.11MA/cm2 has been measured over a bridge at 30K, 3T, corresponding to an equivalent (Ic) value of 8705A/12mm width. This corresponds to a lift factor in critical current of ~11 which is the highest ever reported to the best of author’s knowledge. The measured critical current densities at 3T (B||c) and 30, 40 and 50K, respectively, are 15.11, 9.70 and 6.26 MA/cm2, corresponding to equivalent Ic values of 8705, 5586 and 3606A/12mm and engineering current densities (Je) of 7068, 4535 and 2928A/mm2. The engineering current density (Je) at 40K, 3T is 7 times higher than that of the commercial HTS tapes available with 7.5mol% Zr addition. Such record-high performance in thick flms (>1µm) is a clear demonstration that growing thick REBCO flms with high critical current density (Jc) is possible, contrary to the usual fndings of strong Jc degradation with flm thickness. This achievement was possible due to a combination of strong temperature control and uniform laminar fow achieved in the A-MOCVD system, coupled with optimization of BaZrO3 nanorod growth parameters.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Progress in Critical Current Density (J{sub c}) in Sintered MgB{sub 2} Bulks

The present paper focuses on methods of further improving the flux pinning and critical current density of disk-shaped MgB{sub 2} bulk superconductors by adding excess Mg metal in combination with an optimum silver content and optimized processing conditions. Bulk MgB{sub 2} samples were produced by in situ solid-state reaction in Ar gas ambient using high purity commercial powders of Mg metal and 1.5 wt% carbon-coated amorphous B powders mixed in a fixed ratio of Mg/B = 1.1:2. Further, 4 wt% silver was added to improve flux pinning as well as mechanical performance of the bulk MgB{sub 2} material. The magnetization measurements confirmed a sharp superconducting transition with T{sub c,onset} at around 37 K, which is only by 1 K lower than in bulk MgB{sub 2} material produced without carbon-coated amorphous boron. The critical current density (J{sub c}) values significantly improved in the MgB{sub 2} material with 4 wt% of silver and 1.5 wt% of carbon-coated amorphous boron, sintered at 775 {sup ∘}C for 3 h. At 20 K, this sample showed J{sub c} at around 500 and 350 kA/cm{sup 2} in the self-field and 1 T, respectively, which makes it suitable for several industrial applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

On the Origin of Enhanced Critical Current Density and Thermal-Activated Flux Flow in K{sub x}Fe{sub 2−y}Se{sub 2} Superconductors: the Effect of Quenching and Mn Doping

A magnetotransport, vortex pinning, and critical current density study of superconducting K{sub 0.8}Fe{sub 2−z}Mn{sub z}Se{sub 2} (z = 0, 0.02) single crystals is reported. The parameters of upper critical field, coherence length, and anisotropic ratio at 0 K are presented. Based on thermally activated flux flow model, the values of pinning potential, U{sub 0}{sup ∥{sub c}}(U{sub 0}{sup ∥{sub a}{sub b}}), at 0.25 T are derived to be as large as 1.3 × 10{sup 4}(1.8 × 10{sup 4}) K for z = 0.02, which shows rather robust and retains still larger than pure ones up to 9 T. Utilizing scanning electron microscope, it is revealed the increased magnitude of magnetic moment in magnetic hysteresis loops correlates well with the crystal morphology variation. The evidence on the inhomogeneous distribution of Mn dopants between the matrix and stripe phase is also shown. Furthermore, the temperature dependence of critical current density is analyzed by different pinning regimes and the model of granular superconductor. It is demonstrated that the Josephson coupling between superconducting grains exists in quenched K{sub 0.8}Fe{sub 2−y}Se{sub 2}. However, for Mn-doped sample, the Mn dopant can induce strong vortex pinning in the form of fine K–Mn–Se inclusions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

High Critical Current Density in Internally-oxidized Nb 3 Sn Superconductors and its Origin

In this paper, we report achievement of non-Cu-matrix critical current density $(J_c)$ in internally-oxidized Nb 3 Sn superconductors that surpasses the best state-of-the-art Nb 3 Sn and the $J_c$ specification of the Future Circular Collider. We then explore the mechanism of the improvement, which was believed to be caused by refined grain size. However, our experiment showed that even with similar grain size, internally-oxidized wires had significantly higher $J_c$ than non-oxidized wires. This, combined with transmission electron microscopy and atom probe tomography studies which showed a high density of intragranular nano-precipitates with suitable sizes as pinning centers in internally-oxidized wires, demonstrates a significant contribution from the nano-precipitates.

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

Angular Dependence of the Critical Current Density in Two-Band Ginzburg-Landau Theory

In this study, we have calculated the angular dependence of critical current using the two-band Ginzburg-Landau (GL) theory, generalized for the anisotropic mass case in different bands. It was illustrated that the two-band GL theory gives analytical expression for the angular dependence of critical current density. In calculations, we employ results of microscopical simulations for Fermi surface of LaFeAsO{sub 1 − x}F{sub x} compound. It is shown that such a theory is in agreement with the experimental data for this compound. The obtained result was discussed in comparison with other studies which take into account pinning effects.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Ex Situ MgB{sub 2} Superconducting Tape with Very High Critical Current Density by Using Low-Temperature Sintering Precursor Powders

Ex situ MgB{sub 2} is usually considered as with lower critical current density (J{sub c}) compared to the in situ one due to much worse inter-granular connectivity. In this work, we reported the fabrication of ex situ MgB{sub 2} superconducting tape without dopants using Monel as sheath materials and Nb as the barrier, which has an excellent J{sub c} of 705 A/mm{sup 2} at 4.2 K under 4 T, almost as same as the in situ MgB{sub 2} wires. Massive and high-quality precursor powders with small grain sizes and quite low oxygen content were sintered at relatively low temperature and short time, 580 {sup ∘}C for 3 h. The effects of heat-treatment conditions and tape thickness on the microstructure and J{sub c} of ex situ MgB{sub 2} tapes were discussed. The results suggested that the improvement of grains-connectivity was responsible to the excellent J{sub c} properties of ex situ MgB{sub 2} tape.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Critical Current Density and AC Susceptibility of Bi{sub 1.6}Pb{sub 0.4}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} Superconductor with Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} Nanomaterial

The juxtaposition of superconductivity and magnetism is an interesting research topic due to the exclusivity nature of both phenomena. In this paper, we report the effect of nanosized (~ 5 nm) nickel zinc ferrite Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} (NZFO) on Bi{sub 1.6}Pb{sub 0.4}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} (Bi-2223) superconductor. Bi-2223 powders were prepared using the co-precipitation method. Samples with starting formula Bi{sub 1.6}Pb{sub 0.4}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10}(Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4}){sub x} for x = 0 to 0.1 wt% have been prepared. The structure, microstructure, electrical resistance, and AC susceptibility were determined. The transport critical current density, J{sub ct}, was measured using the 1 μV/cm criterion. The non-added sample sintered for 48 h showed the highest zero resistance temperature, T{sub c-zero} (105 K) and J{sub ct} of 1.83 A cm{sup −2} at 40 K. The x = 0.02 wt% sample sintered for 48 h (T{sub c-zero} = 103 K) showed the highest J{sub ct} of 5.30 A cm{sup −2} at 40 K. The peak temperature of the imaginary part of the complex susceptibility, T{sub p}, increased with sintering time and nanoparticle addition, indicating full flux penetration occurred at higher temperatures and improved intergrain coupling. NZFO nanoparticle did not suppress the transition temperature but it improved the transport critical current density by more than five times indicating it enhanced flux pinning and connectivity between grains in the Bi-2223 phase.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Large enhancement of the in-field critical current density of YBCO coated conductors due to composite pinning landscape

YBa 2 Cu 3 O 7 -based coated conductors (CCs) achieve the highest critical current densities (J c ) of any known superconductor and are a key technology for applications such as rotatory machines, high-field magnets and power transmission. Incorporation of nano-sized non-superconducting second phases as additional vortex pinning centers has been considered the most amenable route to further enhance J c at an industrial scale, and has been successfully used in commercial CCs. The resulting pinning landscape is quite complex, with both synergistic and competing interactions among the various types of defects. Particle irradiation, on the other hand, allows for a controlled post-processing incorporation of a well-defined defect morphology. We have previously shown that irradiation with protons and other light ions can further enhance the in-field J c in commercial state-of-the-art CCs. Here we develop a combined irradiation process that increases J c above values previously achieved by irradiating with only one species. Our new approach involves sequentially irradiating with 250 MeV Au ions and 4 MeV protons. For example, at T ~ 27 K (liquid neon) and μ 0 H ~ 4 T, a region of interest for rotatory machines applications, we obtain J c ~ 5 MA cm -2 , which is about 40% higher than the values produced by the individual irradiations. Finally, we conclude that this is due to the synergistic pinning effects of the introduced splayed, non-uniform columnar defects and small clusters.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Enhancement of Critical Current Density of MgB{sub 2} by Glutaric Acid Doping: a Simultaneous Improvement on the Intrinsic and Extrinsic Properties

In this study, we report an enhancement of critical current density of bulk MgB{sub 2} superconductors by glutaric acid (C{sub 5}H{sub 8}O{sub 4}) doping. The effects of glutaric acid doping on MgB{sub 2} lattice resulted in a record self-field J{sub c} of the order of 10{sup 6} A/cm{sup 2}. A simultaneous improvement in the connectivity, pinning force, and H{sub c2} is the major factor that determined excellent J{sub c} performance. X-ray diffraction analysis showed that samples were single-phase MgB{sub 2} with a minor trace of impurities. A dramatic change in grain morphology and homogeneity in grain distribution was found in the SEM images of doped samples. We observed that homogeneity in grain distribution played a crucial role in the connectivity and the upper critical field (H{sub c2}) of the doped samples. We were able to introduce a new dopant through a two-step mixing approach which is suitable to overcome the degradation of low field and self-field J{sub c} reported for carbon-doped MgB{sub 2} superconductor samples.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗