Search

Although the fascinating effect of superconductivity was discovered more than 100 years ago, only a few low-temperature superconductors, especially Nb3Sn and NbTi, have reached everyday-life use. After the discovery of superconductivity in MgB2 in 2001, a boom appeared in interest in employing MgB2 in commercial applications, facilitated by simple crystallographic structure, high critical temperature, low-cost raw ingredients, simple and fast production, and other advantages for moderate temperature applications. It only lacks high flux pinning and good mechanical performance. In this review, the implications of manufacturing procedures on the superconducting properties, crystal and electronic structure of MgB2 are discussed. The advantages and drawbacks of various manufacturing processes will be presented, as well as the ways how to improve MgB2 superconducting performance. The impact of oxygen reduction, elements doping, the introduction of defects and additives, and the effect of precursor refinement on superconducting properties are here compiled to give an overview of the progress of flux pinning enhancement in bulk MgB2. [ABSTRACT FROM AUTHOR]

Large impact craters on Earth are associated with prominent magnetic anomalies, residing in magnetite of the shocked target rocks and impactites. Shock experiments on magnetite suggest that up to 90% of magnetic susceptibility is lost at pressures >5 GPa, but can be partially restored by post‐shock thermal annealing. The magnetic property changes are caused by shock induced grain size reduction and fragmentation, as well as domain wall‐pinning at crystal lattice defects. A recent study of granitoids from the peak‐ring of the Chicxulub crater found that annealing may occur naturally, but can also be overprinted by high‐temperature hematite‐to‐magnetite transformation in non‐oxidizing environments. In this study, we isolate the effect of defect annealing and hematite‐to‐magnetite transformation using the evolution of hysteresis, isothermal remanent magnetization components and first order reversal curve (FORC) diagrams at different high‐temperature steps. We used a laboratory‐shocked magnetite‐quartz ore, a non‐shocked naturally oxidized granite, and a naturally shocked and oxidized granite. Our findings suggest that annealing of shock‐induced lattice defects partially restores some pre‐shock magnetic behavior and causes an apparent average bulk‐sample domain state increase. Hematite‐to‐magnetite transformation creates new fine‐grained magnetite that strongly overprints the original signal, and decreases the average bulk‐sample domain state. Where annealing and hematite‐to‐magnetite transformation both occur, the new magnetite masks the annealing‐induced property restoration and apparent domain state modification in the shocked magnetite. As magnetite oxidation is a ubiquitous process in surface rocks, these findings are fundamental to understand hematite‐to‐magnetite transformation as a potential overprint mechanism, and could have broad implications for paleomagnetic interpretations. Plain Language Summary: Magnetite is the dominant magnetic mineral in the Earth's crust and is also found in shocked rocks of impact craters, where it can lose up to 90% of its induced magnetization due to fractures and defects in the crystal lattice. Previous experiments in shocked magnetite ore suggest that thermal treatment can recover some shock‐induced defects, and even restore some lost magnetic properties. Similar changes in magnetic properties have been observed in non‐shocked granites with magnetite and hematite after heating, because in non‐oxidizing environments hematite transforms back to very small magnetite grains at high temperatures. Shocked magnetite from the Chicxulub crater is also oxidized to hematite before the impact, and it is unclear if the heating‐induced change of magnetic properties is due to the recovery of shock defects, or hematite‐to‐magnetite transformation. We investigated magnetite from a laboratory‐shocked magnetite‐quartz ore, a non‐shocked naturally oxidized granite, and the granite from Chicxulub at different temperature steps with high‐resolution magnetic methods, and delineated the effects of physical and chemical alteration. We find that hematite‐to‐magnetite transformation overprints the original signal in a similar way to the annealing of shock‐induced features. This study is fundamental for discriminating shock and chemical alteration on the magnetic behavior of magnetite. Key Points: Shock‐induced lattice defects in magnetite alter magnetic behavior and apparent magnetic domain state; annealing partially restores themHematite in oxidized magnetite transforms back to magnetite with heating. Newly formed magnetite has a SD‐SP grain size rangeUsing high‐resolution FORC analysis, we distinguish between annealing and newly formed magnetite from transformation in heating experiments [ABSTRACT FROM AUTHOR]

Understanding the biogeochemical transformations that particulate organic matter (POM) undergoes from production in surface waters to deposition on the seafloor is fundamental for interpreting the paleoceanographic record preserved in sediments. Here we use compound-specific N isotope analysis of amino acids (δ15N AA) from two sediment traps (deployed at 150 m and 250 m water depth) and underlying push-core sediments to investigate temporal and depth related changes in the export flux on a continental shelf basin influenced by a prominent benthic nepheloid layer (BNL). Despite apparent isotopic similarities between traps, molecular data show distinct patterns between the shallower (150 m) and deeper (250 m) sediment traps – specifically, depth-related differences in the relative contributions of particles with different processing histories. The export flux in the shallower trap is dominated by animal sources rather than phytodetritus. Significant microbial degradation in the deeper trap and sediments emphasizes the key roles of resuspension-deposition cycles that are mainly (but not exclusively) facilitated by a thick year-around BNL in the region. The BNL acts as a 'microbial reactor' reworking sinking POM before its ultimate deposition, and also diluting exported material with previously deposited surface sediments. This heavy modification of POM during its passage through and residence in the BNL opens potentially important questions for our current understanding of OC preservation and interpretations of proxy δ15N records in BNL-influenced areas. [ABSTRACT FROM AUTHOR]

Recently, it has been reported that the skyrmion Hall effect can be suppressed in an elliptical skyrmion-based device. Given that defects are unavoidable in materials, it is necessary and important to investigate the dynamics of an elliptical skyrmion in a defective racetrack device. In this work, the current-driven dynamics of an elliptical skyrmion in a defective racetrack device are systematically studied using micromagnetic simulations. The system energy analysis reveals that the magnetic parameters of the circular defect play critical roles in determining the type (repulsive or attractive) and the magnitude of the force on the elliptical skyrmion. The simulated trajectories show that the primary motion modes of the elliptical skyrmion in the defective racetrack can be divided into four types, which are dependent on the values of the Dzyaloshinskii–Moriya interaction (DMI) constant Dd, the perpendicular magnetic anisotropy constant Kd, the magnitude of the driving current density J, and the size d of the defect. Further investigation of the motion-mode phases of the skyrmion reveals the synthetic effects of Dd, Kd, J, and d. Finally, the minimum depinning current density J, which linearly depends on the parameters of Dd and Kd, is obtained for a skyrmion completely pinned in the defect. Our findings give insights into the dynamics of an elliptical skyrmion in the presence of a defect with different magnetic parameters in a racetrack device and may be useful for performance enhancement of skyrmion-based racetrack memory devices. [ABSTRACT FROM AUTHOR]

In the current work, the effect of nano-sized Sn (50 nm)/Sr partial replacement on the superconducting properties such as crystal structure, quality of intra- and intergrain boundary coupling, dc electrical resistivity, and dc magnetization in the Bi-2212 ceramic superconductors were investigated. Ceramic superconductors with nominal composition of Bi2Sr2-x(Sn)xCa1Cu1.75Na0.25Oy where x = 0.25, 0.30, 0.35 and 0.40 were prepared by solid-state reaction method and characterized by powder X-ray diffraction (XRD), dc electrical resistivity, scanning electron microscopy (SEM) and magnetic hysteresis (M–H) measurements. Phase examination of by XRD indicated that the doping of x = 0.25 ratio nano-sized SnO2 to the strontium sites improved the formation of the Bi-2212 high-temperature superconducting phase. SEM micrographs showed that the morphological structure of all samples consisted of plate-like grains, which were separated from each other by grain boundaries, indicating the Bi-2212 superconducting phase. The highest superconductivity transition temperature among the samples was measured as the Tconset = 86 K at x = 0.25 in Bi2Sr2-x(Sn)xCa1Cu1.75Na0.25Oy. M–H loops of the Bi2Sr2-x(Sn)xCa1Cu1.75Na0.25Oy sample at x = 0.25 ratio is larger compared to other examples, indicating improvement intergrain connectivity as well as enhanced flux pinning centers. In addition, the critical current (Jc) values of the samples were calculated from M–H measurement using Bean's critical current model. The best Jc values were obtained as 570 A/cm2 at 15 K, which is a relatively high value for BSCCO superconductors with polycrystalline structure. [ABSTRACT FROM AUTHOR]

The non-toxic copper oxide superconductor, (Cu,C)Ba2Ca3Cu4O11+δ or (Cu,C)-1234, exhibits the highest irreversibility magnetic field among superconducting materials in the liquid nitrogen temperature range and can achieve a superconducting transition temperature of 117 K, providing a new sample system for physical studies of copper oxide high-temperature superconductors. This article examines the underlying mechanisms that contribute to the high critical transition temperature, high critical current density, and notable irreversibility field properties observed in superconductors based on (Cu,C)-1234 copper. It also investigates the recent advancements made in the methods employed for the fabrication of bulks and thin films of this superconductor. Additionally, a comparison is made between the performance parameters of (Cu,C)-1234 superconductors and other superconducting materials that possess critical temperatures surpassing 100 K. This comparison highlights the distinctive characteristics and advantages of (Cu,C)-1234. Finally, we present potential future applications in the fields of energy transmission, magnetic levitation, and scientific research. [ABSTRACT FROM AUTHOR]

Current-voltage characteristics have been calculated for a high-temperature superconductor containing triangular and square periodic arrays of pinning centers with various disorder rates. Non-monotonic dependences of critical current density on the disorder rate have been obtained for the triangular lattice, showing that a perfectly ordered lattice provides smaller critical currents than that with minor distortions, especially at high magnetic fields. For the square lattice, the critical current was mostly declining, with minor peaks at small disorder rates. A thorough analysis of the vortex dynamics has been done, showing the differences in the way vortices move through the disordered lattice and how their paths affect the critical current density. [ABSTRACT FROM AUTHOR]

BACKGROUND: Salt stress has recently emerged as one of the most significant abiotic stresses with negative impact on crop production. Photosynthesis is a vital biochemical process in plants, very sensitive to environmental constraints, including salt stress. OBJECTIVE: The aim of this study was to evaluate the impact of salt stress on photosystem II in the leaves of blackberry cultivars (Rubus fructicosus L.). METHODS: Two blackberry cultivars (Thornfree and Boysen) were exposed to salt stress (20, 40, and 60 mM NaCl) for 28 days in in vitro culture. The photosynthetic activity was evaluated by probing chlorophyll a fluorescence (JIP test) and photosynthetic pigments. RESULTS: The maximum quantum yield of PSII (Fv/Fm), performance indexes (PIABS and PItotal), and photosynthetic driving force (DFABS) were greatly affected by salt stress in the leaves of Boysen cultivar. Lower photosynthetic efficiency was confirmed by the increased values of absorption flux per RC (ABS/RC), trapping flux per PSII RC (TR0/RC), dissipation flux per RC (DI0/RC), decreased values of chlorophyll and carotenoid contents, disruption in the interaction between the light-harvesting complex and the core proteins of PSII, as well as disruption of the oxygen-evolving complex. CONCLUSIONS: The provided informations suggest that the photosynthetic apparatus of Thornfree cultivar was found to be more tolerant to salt stress compared to Boysen. [ABSTRACT FROM AUTHOR]

In planetary radiation belts, the Kennel‐Petschek flux limit is expected to set an upper limit on trapped electron fluxes at 80–600 keV in the presence of efficient electron loss through pitch‐angle diffusion by whistler‐mode chorus waves generated around the magnetic equator by the same 80–600 keV electron population. Comparisons with maximum measured fluxes have been relatively successful, but several key assumptions of the Kennel‐Petschek model have not been experimentally tested. The Kennel‐Petschek model notably assumes an exponential growth of chorus waves as the trapped electron flux increases, and a fixed maximum wave power gain of about 3. Here, we describe a method for inferring the near‐equatorial wave power gain using only measurements of trapped, precipitating, and backscattered electron fluxes at low altitude. Next, we make use of Electron Losses and Fields Investigation (ELFIN) CubeSats measurements of such electron fluxes during two moderate geomagnetic storms with sustained electron injections to infer the corresponding chorus wave power gains as a function of time, energy, and equatorial trapped electron flux. We show that wave power increases exponentially with trapped flux, with a wave power gain roughly proportional to the theoretical linear convective gain, and that the maximum inferred gain near the upper flux limit is roughly 10, with a factor of 2 uncertainty. Therefore, two key theoretical underpinnings of the Kennel‐Petschek model are borne out by the present results, although the strong inferred gains should correspond to higher flux limits than in traditional estimates. Key Points: A method for inferring equatorial wave power gain from low altitude electron flux measurements based on quasi‐linear theory is describedThe inferred chorus wave power gain increases roughly linearly with equatorial 180–300 keV trapped electron flux during moderate stormsInferred chorus wave power gains typically reach 10 near the upper flux limit [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSC) are emerging technologies that have shown continuous improvement in power conversion efficiency (PCE) and stability. However, a very important aspect that has been seldom considered is the reproducibility of PCE of PSC devices. It is possible to achieve PCE from 10.21% to 17.05% using scalable slot‐die‐coating technique. However, a spatial distribution of performance is clearly observed for device samples on a 4 × 4 cm substrate. The relatively low PCE is mainly coming from the losses of electrical mechanism. To have in‐depth understanding of the losses, the dominant loss analysis techniques including numerical simulations are used to explore the mechanism. In the results, it is indicated that a part of efficiency decrease is due to the increase of bulk defect density which linearly changes with the quality of the perovskite layer and related to recombination process. However, extremely high‐charge‐carrier transportation losses are found at the HTL/perovskite interface that are related to the Fermi‐level pinning mechanism for low‐efficiency device. The result of physics insight of perovskite solar cells leads to a strategy, where chemical passivation technique is used to achieve the PCE from 13.81% to 18.07% for the batch of devices with good reproducibility. [ABSTRACT FROM AUTHOR]

The precipitation-hardening Sm-Co magnets not only have irreplaceable applications under extreme conditions such as high temperatures, but are also the most typical magnets with pinning-controlled magnetization reversal mechanism. However, there have always been two views on this type of pinning, attractive or repulsive. In this article, the modification of the parallel interface to the titled interface, led to occurrence of quasi-repulsive and quasi-attractive pinning modes, by employing micromagnetic simulation methods. The corresponding domain wall energy relationship between the pinning phase and main phase was analyzed for different pinning modes, according to the morphology of domain wall from the simulation results. The analysis results indicated that relatively small difference in domain wall energy between the two phases led to quasi-repetitive and quasi-attractive pinning modes. Our findings can provide a reference for further understanding of the magnetization reversal mechanism of precipitation-hardening Sm-Co magnets. The emphasis on the influence of 1:5/2:17 interface orientation on pinning also provided a perspective on the magnetization reversal mechanism of other nanostructured permanent magnet materials. [ABSTRACT FROM AUTHOR]

How and why the reliability of ferroelectric HfO2‐ and HZO (Hf0.5Zr0.5O2)‐based memory devices strongly depends on the choice of electrode materials is currently under intense discussion. Interface conditions such as band alignment, defect formation, and doping are recognized as decisive and interrelated parameters, but a unified picture of the physical mechanisms is still missing. Here, two opposite scenarios of band alignment are found in TiN/HZO/TiN and IrO2/HZO/IrO2 using hard X‐ray photoelectron spectroscopy, revealing on the one hand the conditions for a stable device performance, and the origin of their degradation on the other. As a key difference, TiN electrodes scavenge oxygen from the HZO, while IrO2 electrodes supply it. Considering the electronic doping limit of HfO2, a key condition for the stability of ferroelectric devices can be identified: The alignment of the charge neutrality levelwith respect to the metallic Fermi level, which is pinned by the doping limit. Stable device performance can only be achieved for oxygen‐deficient HfO2‐based interfaces, where the Fermi level of the metal electrode is close to the conduction band of the ferroelectric insulator. This empirical model explains the fatigue behavior of HfO2‐based capacitors using either oxygen‐scavenging TiN or oxygen‐supplying IrO2 electrodes. [ABSTRACT FROM AUTHOR]

Boron (B)‐doped Nb3Al superconductors are prepared by mechanical alloying and subsequent sintering process in this work. Then, the critical current density (Jc) of Nb3Al with different amounts of B doping is studied. In the results, it is shown that Jc performance of Nb3Al is improved obviously after B doping. The best Jc value obtained in this work is 2.2 × 104 A cm−2 (4.2 K, 5 T) for Nb3(Al0.9B0.1) sample. Furthermore, the mechanism of enhanced Jc performance for Nb3(Al0.9B0.1) sample is comprehensively explored. It is found that B doping can significantly enhance the grain connectivity of Nb3Al superconductor, and the active cross‐sectional area fraction values increase from 0.11 for the undoped sample to 0.34 for Nb3(Al0.9B0.1) sample. In addition, the lattice distortion caused by the interstitially dissolved B may also serve as flux pinning centers, which strengthens the flux pinning force of Nb3(Al0.9B0.1). [ABSTRACT FROM AUTHOR]

Background: Salinity stress is an environmental constraint that normally develops concurrently under field conditions, resulting in drastic limitation of rice plant growth and grain productivity. The objective of this study was to explore the alleviating effects of NaCl pre-treatment on rice seedlings as well as the salt tolerance mechanisms by evaluating morph-physiological traits. Results: Variety Huanghuazhan, either soaked in distilled water or 25 mg/L Prohexadione calcium (Pro-Ca), were first hardened with varying concentrations of NaCl solutions (0 and 50 mM NaCl), and then subjected to varying degrees of salt stress (0 and 100 mM NaCl), indicated by S0, S1, S2 and S3, respectively. Growth analysis suggested that NaCl-pretreatment improved the root/shoot ratio in water-soaked rice plant at DAP 0. Data related to the reaction center density, photosynthetic electron transport efficiency, trapping efficiency were compared before (CK) using performance Index (PIabs). Compared to S2 (Pro-Ca-S2) treatment, PIabs did not show any difference with plants pre-treated with NaCl (S3 or Pro-Ca-S3). Rather than PIabs, significant difference was found in photosynthetic electron transport efficiency (ΨEo). The ΨEo value in Pro-S2 was significantly lowered as compared to Pro-S3 treatment at DAP 7, and the decrease rate was about 6.5%. Correlation analysis indicated leaf PIabs was weak correlated with plant biomass while the quantum yield for reduction of the PSI end electron acceptors, trapped energy flux per reaction center and PSII antenna size displayed strong positive correlation with biomass. Additional analysis revealed that 100 mM NaCl significantly reduced leaf linear electron flux under low-light conditions, regardless of whether seedlings had been pre-treated with 50 mM NaCl or not. Conclusions: NaCl-induced salt tolerance was related to the robust photosynthetic machinery. [ABSTRACT FROM AUTHOR]

To overcome the interfacial nature of spin‐orbit torque (SOT) in bilayers, novel bulk SOT (BSOT) is widely investigated to implement high‐density and low‐power spintronic devices. However, the underlying mechanism of efficient BSOT switching remains unclear, especially the anomalously enhanced effective spin Hall angle (θSH) with increasing ferromagnet thickness (tFM), due to lacking simple and high‐tunable material systems. Here, a series of Pt/Co multilayers with invariable thickness gradient and varying stacking numbers is designed to systematically explore BSOT origin and enable efficient switching via engineering symmetry breaking. As tFM increases, the critical current density decreases while the switching efficiency and θSH build up. Comparative experiments directly demonstrate that gradient‐induced local spin current is more efficient than that in the bilayer. Moreover, x‐ray absorption spectroscopy (XAS) results reveal that the increasing stacking number can effectively engineer the symmetry breaking at Pt/Co interface to induce strong interfacial spin‐orbit coupling. On this basis, it is concluded that the BSOT effect, as well as the anomalously enhanced switching efficiency, and θSH arises from gradient‐induced bulk and interface symmetry breaking. These findings clarify the underlying mechanism of BSOT, and broaden the scope of material engineering to improve switching efficiency and inspire more memory and computing applications. [ABSTRACT FROM AUTHOR]

Petrological assimilation is a key process in the evolution of high-grade metamorphic terrains in the continental crusts. This study examines the mechanisms of such macroscopic assimilation between felsic (F) and mafic (M) constituents as two petrologically interacting continuum phases, as observed in the Chotanagpur Granite Gneissic Complex (CGGC), India, which underwent amphibolite to granulite facies metamorphism (~775 to 900°C and 7 to 11 kb) between from the Paleoproterozoic to the late Mesoproterozoic. From field investigation we could recognized four interface patterns: planar, wavy, fingering and incoherent, which are generated at the interface between the Fand M units. We have adopted the Turing type reaction-diffusion (RD) approach, which is a well established theoretical model to interpret any complex auto-regulatory pattern in natural and physical sciences, to understand the physics of the self-organizing interface geometries observed across the CGGC. The RD model findings suggest that these patterns are constrained by a combination of: diffusion coefficients (DF, DM) of F and M, a linear or non-linear reaction term (R) that describes phase interactions and a pinning field (W) that introduces microscale heterogeneity. For linear interactions, F -- M undergo homogeneous mixing and show planar/wavy interfaces, when DF = DM and W =0. The mixing turns heterogeneous as DF * DM and W > 0, resulting in phase boundary migration with a fingering pattern. Non-linear reaction coupling enhances heterogeneous mixing and produces incoherent phase boundaries where F-phases host relics of M-phases, following a power-law size distribution. Striking similarities of interface patterns and fractal dimensions estimated from model and CGGC validate the proposed mechanism of macroscopic petrological assimilation. We argue that RD model provides a new insight into the genesis of hybrid rocks in metamorphic terrains. [ABSTRACT FROM AUTHOR]

Internal strain and its distribution within the crystal lattice play crucial roles in modulating dislocation activities, thereby affecting mechanical properties of materials. Through the synergistic application of integrated differential phase contrast, in situ transmission electron microscopy characterizations, and computational simulations, a method is unveiled for homogenizing dislocation pinning in NiCoCr multi‐principal element alloy (MPEA) through the introduction of a high concentration of oxygen atoms with high diffusion mobility. The doping of massive oxygen atoms creates a high density of strong local pinning points for dislocation motion. Notably, oxygen interstitials exhibit remarkable diffusion and mobility across different octahedral and tetrahedral sites within the distorted crystal lattice of NiCoCrO alloy, even at room temperature. The capability allows for the release of severe stress concentrations arising from dislocation entanglement and the establishment of new strong local pinning points at alternative locations in a uniform way, enabling the material with high strength and outstanding deformability. These findings suggest that interstitial atoms can exhibit significant mobility, even at ambient temperature, in complex MPEAs with spreading lattice distortion, opening new possibilities for dislocation engineering. [ABSTRACT FROM AUTHOR]

In order to describe the dependence of critical current on specimen length and crack size distribution in the superconducting tape with cracks of different sizes, a Monte Carlo simulation and a model analysis were carried out, employing the model specimens of various lengths constituted of multiple short sections with a crack per each. The model analysis was carried out to evaluate the effects of the two factors on the critical current of a specimen. Factor 1 is the size of the largest crack in a specimen, and Factor 2 is the difference in crack size among all sections at the critical voltage of critical current. Factors 1 and 2 were monitored by the smallest ligament parameter among all sections constituting the specimen and by the number of sections equivalent to the section containing the largest crack at the critical voltage of the critical current of the specimen, respectively. The research using the monitoring method revealed quantitatively that the critical current-reducing effect with increasing specimen length is caused by the increase in the size of the largest crack (Factor 1), and also, the critical current-raising effect is caused by the increase in the difference of crack size (Factor 2). As the effect of Factor 1 is larger than that of Factor 2, the critical current decreases with increasing specimen length. With the present approach, the critical current reducing and raising effects under various crack size distributions were evaluated quantitatively as a function of specimen length, and the specimen length-dependence of critical current obtained by the Monte Carlo simulation was described well. [ABSTRACT FROM AUTHOR]

In the present work, Tungsten trioxide (WO3) nanoparticles are added (up to 5 wt%) to Bi2Sr2.14Ca0.86Cu2Oy (Bi 2212) compound using a sol-casting method that facilitates their uniform distribution in the Bi 2212 matrix. Sintering at 870 oC, close to the melting point, has led to the formation of nearly spherical particles of WSr2CaO6 (W-alloy) phase (20–80 nm) by local reaction of distributed nano WO3 particles with Bi 2212 grains. These particles are well dispersed and located preferentially at the platelet-like grain boundaries in the superconducting Bi 2212 composites. This is of interest in analogy to the widely studied YBa2Cu3Oy (Y123) superconductor with two-phase microstructure with Y2BaCuO5 (Y211) precipitates, which is known to provide flux pinning and considerable enhancement of the critical current densities (Jc). The superconducting properties of the present Bi 2212 composites with varying amounts of second phase content are assessed by recording M-H loops at different temperatures 5 to 77 K. Critical current densities are found to be non-zero at 5 K in all the samples up to 9 T applied field, suggesting irreversibility fields to be above 9T. A considerable enhancement of Jc and flux pinning force are observed at temperatures 15–50 K, compared to pure 2212 phase at low concentrations (0.1 wt%) of nano WO3 addition in the composites. A minor drop in the superconducting transition temperature Tc (onset) from 90 to 80 K observed in the sample with higher WO3 addition (5 wt%) caused a lowering of flux pinning force at temperatures 50 K and above. Scaling laws of flux pinning show that normal surface pinning is the dominant mechanism in all the samples, which can be attributed to the structural defects at the 2212 platelet boundaries. Flux pinning is observed to be sustained in a broader field range and up to 50 K in all the samples with WO3 addition. This provides evidence that the interfacial defects associated with the second phase (W-alloy) particles, created at the platelet boundaries, are effective in providing flux pinning. [ABSTRACT FROM AUTHOR]

Optimisation of REBCO coated conductor tapes specifically for use in nuclear fusion will help improve the magnet component lifetimes in future tokamak reactor power plants. The focus of this work was exploration of a novel approach to irradiation studies on REBCO tapes, utilising multiple magnetic measurements to probe evolution of the REBCO flux-pinning landscape more deeply than reported in other studies, for the purpose of identifying primary limiting factors affecting performance. Gamma irradiation experiments were conducted, and pre-/post-irradiation results from DC and AC magnetic measurements using a Physical Property Measurement System (PPMS) are discussed. Magnetisation critical current density (Jc) decreased in all samples with increasing dose, except for the silver overlayer-only samples which did not contain artificial pinning centres (APCs), where Jc increased with dose. Removal of the copper stabiliser coupled with the presence of APCs allowed gamma irradiation to induce pinning force maximum peak shifts, from above 14 T before irradiation to below 9 T afterwards. Flux creep rate varied with the evolving pinning landscape, and the degree of Jc degradation directly correlated with creep rate fluctuations post-irradiation. Changes in critical temperature and diamagnetic saturation also corresponded with changes in Jc and flux creep rate. The major conclusion from this study was that minimisation of flux creep rate is the key to maintenance of performance under fusion-relevant operating conditions. Flux creep manifests as problematic AC losses in all high-temperature superconducting machines; therefore, future work will focus on reduction/prevention of the phenomenon to enhance longevity of performance in any application. [ABSTRACT FROM AUTHOR]

In this paper, the advantages and disadvantages of using B powder and C encapsulated B powder as a precursor during the production process of MgB2 with the addition of pyrene (C16H10) were investigated. Two MgB2 bulk samples with the addition of 10 wt % C16H10 of 1 g MgB2 were produced by the in-situ method using B powder and C encapsulated B powder. The C encapsulated B powder as a precursor was prepared by adding 10% C16H10 as a C source. From XRD and SEM analysis, a greater increase in MgO phase and a greater decrease in a-lattice parameter were observed for the sample produced with B, compared to the sample produced with C encapsulated B. The curves of critical current density (Jc) at 5 K showed a similar character for both samples. The Jc values at 5 K in self field were respectively obtained as 1.52 × 105 A/cm2 and 1.90 × 105 A/cm2 for the samples produced by B and C encapsulated B. The decrement ratio of in-field Jc at 20 K was less affected by increasing magnetic field for the sample produced using C encapsulated B due to the relatively higher increase in the irreversibility field (Hirr) and the upper critical magnetic field (Hc2) values. The Jc values at 20 K and 3 T were respectively determined as 1.49 × 104 A/cm2 and 1.93 × 104 A/cm2 for the samples produced with B and C encapsulated B. [ABSTRACT FROM AUTHOR]

Synthetic flux-grown end-member gahnite, ZnAl2O4, and several different colored crystals doped with one or more transition metals including Mn, Ni, Cr, Co, and Fe were studied by electron mi-croprobe methods and UV/Vis/NIR single-crystal optical absorption spectroscopy. The first major objective was to measure and assign the various electronic absorption features. The second was to analyze quantitatively the crystal colors using the experimental spectra and the CIE 1931 color- spacechromaticity diagram. The microprobe results show that the doped gahnites have transition metal concentrations between about 0.001 and 0.1 cations per formula unit. The spectrum of colorless, nominally pure ZnAl2O4 displays no absorption in the visible region. Microprobe analysis of a light-blue gahnite crystal reveals small amounts of Ni and Mn. The UV/Vis/NIR spectrum does not indicate any dd-electronic transitions relating to Mn. All absorption features also cannot be fully interpreted using Tanabe-Sugano diagrams for Ni2+ in either octahedral or tetrahedral coordination. A series of seven slightly different colored gahnites with differing concentrations of Cr3+ and most also containing smaller amounts of Ni was investigated. The spectrum of a one pink crystal shows two intense absorption features in the visible region. They are assigned to spin-allowed 4A2g → 4T2g (4F) and 4A2g → 4T1g (4F) transitions of VICr3+. Other spectra display additional weak bands and lines that are most probably spin-forbidden dd-transitions of Ni2+. These gahnites with Ni and Cr show varying purple colorations depending on the concentrations of both metals. Two more deeply blue gahnites contain Co2+ as demonstrated by their UV/Vis spectra but not by microprobe analysis. Two intense absorption features at ~7440 and ~16 850 cm–1 are observed and assigned to the spin-allowed transitions 4A2 → 4T1 (4F) and 4A2 → 4T1 (4P) of Co2+, respectively. Complex absorption fine structure, caused by spin-orbit and/or vibronic interactions, is also observed. Three diferent gahnites with yellow to orange colorations contain measurable Mn. Their spectra are similar in appearance and display several weak IVMn2+ spin-forbidden transitions located above 20 000 cm–1. The spectra of two green gahnites show several Fe spin-forbidden electronic transitions arising from single, isolated IVFe2+ and VIFe3+ cations between 10 000 and 25 000 cm–1. The intensities of some of the VIFe3+-related bands can be increased through exchange-coupled interactions with next nearest IVFe2+ neighbors. The colors of various doped gahnites and the end-member galaxite are analyzed using their single-crystal absorption spectra in the visible region. Their dominant wavelength, λk, and hue saturation, pc, values are given on the CIE 1931 color-space-chromaticity diagram and are discussed. The Hex colors of all crystals are calculated and can be compared to those of the studied crystals. [ABSTRACT FROM AUTHOR]

Higher density heat flux is the major cause of damage to the electronic component; therefore, cooling such components are of the utmost importance to operate in a safe zone and to increase their life. For this purpose, Microchannel heat sinks (MHSs) are among the most practical methods for dissipating unwanted heat. In this regard, the novel lozenge-shaped pin-fins in the flow passage of the microchannel heat sink (MHS) have been designed and proposed to achieve higher cooling performance. Aspect ratios (λ = 0.30, 0.39, 0.52, 0.69, 1.00) of several lozenge-shaped pin-fins have been used into the design of MHS to investigate their impact on heat transmission and fluid flow characteristics. A three-dimensional model of MHS with a lozenge-shaped has been generated and simulated numerically in the following range of Reynolds numbers, starting from 100 to 900. Heat transmission and flow characteristics have been presented and discussed in detail. It has been found that introducing lozenge-shaped pin-fins in MHS has greatly improved cooling performance. The highest improvement in Nusselt number has been observed when aspect ratio (λ) of lozenge-shaped pin-fins was 1.00. The Nusselt number have been varied in the following ranges of 6.96–12.34, 6.97–12.72, 7.01–13.62, 7.09–14.43, and 7.12–15.26 at λ = 0.30, λ = 0.39, λ = 0.52, λ = 0.69, and λ = 1.0, respectively. In addition, a study of the thermohydraulic performance of the proposed lozenge-shaped pin-fins in the MHS found that this design is an effective means of lowering operating temperature. [ABSTRACT FROM AUTHOR]

Nanoparticle-reinforced alloys offer the potential for high-strength, high-temperature alloys. While the classic Smith–Zener equation is widely used to predict grain size with pinning particles, it does not explicitly factor the influence of nucleation rate, which is a critical phenomenon that affects microstructure. A model is developed using the open-source phase-field modeling software, PRISMS-PF, to explore the impact of nucleation rate on alloy solidification for both random and clustered distributions of nanoparticles. Heterogeneous nucleation and grain boundary pinning are explicitly included, and a wide range of nanoparticle area fractions (0.01–0.1) and nucleation site densities (106–1012nuclei/m2), which affect nucleation rates, are modeled. Quantitative analyses inform a kinetically modified Smith–Zener relationship, which predicts grain size dependence on nucleation rate as dz ~ 1/J*0.15. Simulations also reveal a strong preference of nanoparticle pinning grains, especially at triple points. Total pinning fraction increases rapidly with nucleation rate before saturating between 0.85 and 0.90 for both random and clustered 2D distributions. At low area fractions (< 0.05), particle clustering increases grain size between 15% and 45% compared to random distributions. A main advancement of this work is the quantification of how nucleation rate, in addition to nanoparticle size and concentration, affects grain size and therefore alloy strength. [ABSTRACT FROM AUTHOR]

To date, MoS2 can only be achieved at microscale. Edge pinning effect caused by structure defects is the most obvious barrier to expand the size of structural superlubricity to macroscale. Herein, we plan to pin edge planes of MoS2 with nanospheres, and then the incommensurate structure can be formed between adjacent rolling nanoparticles to reduce friction. The sputtered MoS2 film was prepared by the physical vapor deposition (PVD) in advance. Then enough Cu2O nanospheres (∼40 nm) were generated in situ at the edge plane of MoS2 layers by liquid phase synthesis. An incommensurate structure (mismatch angle (θ) = 8°) caused by MoS2 layers was formed before friction. The friction coefficient of the films (5 N, 1,000 r/min) was ∼6.0×10−3 at the most. During friction, MoS2 layers pinned on numerous of Cu2O nanoparticles reduced its edge pinning effect and decreased friction. Moreover, much more incommensurate was formed, developing macro-superlubricity. [ABSTRACT FROM AUTHOR]

Using torch brazing techniques, 316 stainless steel was brazed to CP copper using flux-coated low silver content filler with 20% Ag. The brazing torch utilized a fuel mixture of propane gas with oxygen to produce the required heating amount due to the possibility of economic interest in employing low-silver-content filler. The brazing filler's braze ability with SUS304 and copper was scrutinized and deeply analyzed. A ferrite barrier layer was made on the stainless-steel side, and an excellent brazed joint was produced. Metallurgical studies using an optical microscope and a scanning electron microscope (SEM) confirmed the production of a ferrite layer. This layer's advantages were carefully examined with metallurgical testing, electron diffraction scanning (EDS), EDS mapping, and EDS line analyses, including preventing copper intergranular penetration into the stainless-steel grain boundary. The mechanical properties of the brazed joint and its usability were assessed through Vickers microhardness and tensile tests on the brazing seam and both base metals. The results of the brazing process showed that using flux-coated low-silver brazing techniques produced strong joints with satisfactory mechanical properties. These techniques are a cost-effective alternative to high-priced brazing fillers with high silver content. Geometrical models simulated the heat distribution using ANSYS and SOLIDWORKS software to analyze penetration depth, joint quality, surface cracks, and the relation between molten filler density variation and the wetting process. [ABSTRACT FROM AUTHOR]

Needs for neutron detection and monitoring in high neutron flux environments are increasing in several different fields. A completely solid-state, current mode bolometric detector is constructed as a solid substrate transition edge sensor based on a high-T c superconducting meander. The detector consists of four individual pixels of which three pixels include 10 B 4 C neutron absorption layers. The absorbed energy per neutron absorption reaction is modelled and compared to experimental data. The response of the tested detector is directly correlated to a cold neutron beam with a flux of 1.8 × 10 8 n / cm 2 / s modulated by a slit. The signal is found to be an order of magnitude higher than the thermal background. The dynamics described by the temporal saturation constants is governed by a modulation frequency less than 1 Hz . The thermal response is dynamic and never fully saturates for 50 s exposures. The efficiency for this proof-of-principle design is 1–2%. Possibilities for optimization are identified, that will increase the efficiency to become comparable to existing solid boron-10 detectors. The existing detectors with event-based read-out have limited functionality in high flux environments. The superconducting bolometer described in this work using current-mode readout will pave the way for high flux applications. [ABSTRACT FROM AUTHOR]

The gas‐insulated switchgear (GIS) is a vital component of a power system, and understanding the shock wave characteristics of its internal discharge is crucial to ensure the safe and stable operation of the entire system. In this study, a high‐speed shadowing technique is employed to obtain the shadowgraphs of a typical flow‐field evolution of sulfur hexafluoride (SF6) gas following the breakdown of a pin–plate gap inside a GIS. Experimental data were used to derive parameters, including the Mach number, propagation speed, distance of the discharge shock wave, and the temperature, pressure, density, and velocity of the SF6 gas after wave generation. With a 0.2‐mm discharge gap and 0.4‐MPa pressure, the discharge generates a spherical shock wave, centred at the contact between the discharge channel and electrodes, that propagates in all directions. The shock wave gradually weakens after 20 μs, propagating at near‐sonic speed, and its Mach number decreases from 2.92 to 1.15; similarly, its post‐wave parameters sharply decrease during the first 20 μs. Additionally, a significant reflection occurs when the shock wave propagates to the metal wall. The authors' findings provide a valuable reference for detecting and diagnosing the internal discharge in GISs. [ABSTRACT FROM AUTHOR]

Chemcial fertilizer as the main strategy for improving the vegetable yields was excessively applied in recent years which led to progressively serious soil problems such as the soil acidification. According the situation, five different biofertilizer treatments [no fertilizer (CK), inoculations of Bacillus subtilis (Bs, T1), combination of Bs and Bacillus mucilaginosus (Bs+Bm, T2), Bs and Bacillus amyloliquefaciens (Bs+Ba, T3), and Bm+Ba (T4)] were conducted to investigate the effect of the growth, leaf physiological indices, and chlorophyll fluorescence of spinach seedlings in the growth chamber. The growth and physiological indices of the spinach seedlings attained a maximum under the T2 treatments. Under the T2 treatment, the ABS/RC (Absorption flux per RC), TR0/RC (Trapping flux per RC), and ET0/RC (Electron transport flux per RC) was significantly increased, while the DI0/RC [Dissipated energy flux per RC (at t = 0)] was decreased. The OJIP curve was improved under of the inoculations of fertilizers, and the increasing range was the largest under the T2 treatment. The leaf light response curve (LC) was also significantly increased under the T2 treatment. The plant growth characteristics [leaf length (LL), leaf weight (LW), plant height (PH)] were positively correlated with the J-I-P test chlorophyll fluorescence parameters [PIABS (Performance index for energy conservation from exciton to the reduction of intersystem electron acceptors), φP0 (Maximum quantum yield of primary photochemistry), φE0 (Quantum yield of electron transport), ψ0 (The probability that a trapped exciton moved an electron in electron transport chain further than QA-), TR0/RC, and ET0/RC] while negatively correlated with φD0 (Quantum yield of energy dissipation) and DI0/RC. The leaf physiological characteristics [SP (soluble protein concentrations), SC (soluble carbohydrate concentrations), Chl a (chlorophyll a), Chl b (chlorophyll b), Chl a+b, Chl a/b, and WP (water potential)] were positively correlated with the J-I-P test chlorophyll fluorescence parameters (PIABS, φP0, φE0, ψ0, ABS/RC, TR0/RC, and ET0/RC) while negatively correlated with φD0 and DI0/RC. These results indicated that the combination of Bs+Bm inoculations promoted the growth of the spinach and improved the adaptability of the vegetable to acid soil while Ba inoculation didn't have any effects to plants. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of the z-pin pre-hole inserted (ZPI) process on the impact resistance and post-impact flexural properties of skin/stringer composite structure with different z-pin parameters. The responses of the specimens are characterized in terms of impact denting & cracking length, load-carrying capacity, energy absorption and so on. Experimental results demonstrate that the z-pin cannot inhibit the initiation of debonding cracks at the skin/stringer interface. However, the z-pin forms a bridging traction zone across the cracking and prevent it from developing, which ensures the skin/stringer structure preserve higher peak loading and impact resistance. The specimens with the highest z-pin density have better impact resistance and outstanding residual flexural post-impact properties. Moreover, z-pins play a bridging role through its own failure. One is the inter-fiber debonding and splitting or shear failure of z-pins due to "snubbing effect," the other is the sliding friction of z-pins and z-pins' elastic deformation. These results could provide some guidance for designing z-pinning connection of composite skin/stringer structure. [ABSTRACT FROM AUTHOR]

The analysis of possible current distributions when passing current through a periodically modulated long Josephson contact located in an external magnetic field is carried out. An approach based on the analysis of continuous configuration modification proceeding in the direction of Gibbs potential reduction is used for the calculation. The case when the pinning parameter is less than the critical value is considered. It is shown that at any value of the external magnetic field, there is a critical value of the transport current, when exceeded, the situation ceases to be stationary, as a result of which energy passes into radiation and heat, i.e., currents cease to be persistent. The value of the critical current is determined by the value of the magnetic field at which the vortices begin to fill the entire length of the contact. With an increase in the external magnetic field, the critical value of the current decreases. [ABSTRACT FROM AUTHOR]

The applicability of the calibration method for heat flux sensors based on anisotropic bismuth thermoelements and a heterogeneous copper—nickel structure using a reflected shock wave to determine the volt–watt coefficient is demonstrated. The coefficient obtained for a sensor based on anisotropic thermoelements is close to the stationary calibration data, and for a sensor based on a heterogeneous structure, to the results of numerical simulation. [ABSTRACT FROM AUTHOR]

In this study, TiC-reinforced CoCrFeMnNi high-entropy alloy (HEA) composites were prepared by mechanical alloying (MA) and spark plasma sintering (SPS). The phase composition, microstructure, mechanical and thermal expansion behaviour of composite HEAs were investigated. The results reveal that the addition of TiC has no effect on the crystal structure, however, the microstructure and mechanical properties show a strong dependency on the TiC content. Compared to the original HEA, the composite HEA shows decreased grain size, resulting in TiC nanoparticles (NPs) retarding grain growth by pinning the grain boundaries. With increasing TiC content from 0 to 4 wt-%, significant increases in the hardness from 410 to 480 HV and compressive yield strength from 680 to 1100 MPa, which is mainly due to the grain boundary and dispersion strengthening effects. Moreover, the thermal expansion curves show linear increments up to 800°C and decrease with increasing TiC content. [ABSTRACT FROM AUTHOR]

In this study, for the first time, we present a systematic study of the critical current density Jc at two magnetic field orientations and in a single crystal of the superconducting pnictide EuCsFe4As4, which shows a magnetic ordering below Tc and belongs to the 1144 family. The anisotropy of Jc and its temperature dependence are determined. The exponents of the dependences from 0.1 to 1 T are in a good agreement with the theoretical predictions for strong Abrikosov vortex pinning, which is also confirmed by the values of the pinning strength estimated using the Dew-Hughes model. [ABSTRACT FROM AUTHOR]

It has been proposed that flux compactifications of supercritical string theories (i.e., with spacetime dimension D > 10) have dS vacua, with large D acting as a control parameter for corrections to the classical spacetime effective action. In this paper, we provide a detailed analysis of the self-consistency of such models, focussing on α′ and backreaction corrections. We first show that all supercritical AdS, Minkowski and dS vacua in this setting have ≳ O 1 curvature and/or field strengths in the string frame. This may be in tension with suppressing α′ corrections unless the coefficients of the higher-derivative terms have a sufficiently strong large-D suppression. We then argue that an additional and more severe problem arises in the dS case due to the backreaction of O-planes. In particular, we argue using a combination of geometric bounds and string-theory constraints that the O-plane backreaction is large in supercritical dS models. This implies that a large part of the naive classical geometry is eaten up by singular holes and thus indicates a breakdown of the classical description. Our finding resonates with several other recent results suggesting that string theory does not admit dS vacua in regimes where string and backreaction corrections are under control. As byproducts of our analysis, we derive a number of technical results that are useful beyond the specific applications in this paper. In particular, we compute the leading backreaction corrections to the smeared solution in a general flux compactification from D to d dimensions for an arbitrary distribution of O-planes and D-branes. We further argue for a general estimate for Green's functions on compact manifolds (and therefore for the backreaction corrections) in terms of their diameter, volume and dimension. [ABSTRACT FROM AUTHOR]

We investigated the temperature dependence of the current fluctuations in thin films of the quasi-two-dimensional 1T-TaS2 van der Waals material. The current fluctuations, determined from the derivative current–voltage characteristics of two-terminal 1T-TaS2 devices, appear prominently at the electric fields that correspond to the transitions between various charge-density-wave macroscopic quantum condensate phases and at the onset of the depinning of the charge density wave domains. The depinning threshold field, ED, monotonically increases with decreasing temperature within the nearly commensurate charge-density-wave phase. The ED value increases with the decreasing 1T-TaS2 film thickness, revealing the surface pinning of the charge density waves. Our analysis suggests that the domain depinning is pronounced in the nearly commensurate phase. It is induced by the electric field but facilitated by local heating. The measured trends for ED of the domain depinning are important for understanding the physics of charge density waves in quasi-two-dimensional crystals and for developing electronic devices based on this type of quantum materials. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive analysis of the effects resulting from the substitution of biowaste-derived carbon-dot (CD) from human hair on structural and superconducting properties of MgB2. Syntheses of polycrystalline samples were accomplished through a standard solid-state reaction route. X-ray powder diffraction results confirm the formation of MgB2 as a primary phase in all samples and show the successful substitution of carbon for boron in MgB2. The critical current density, determined at 20 K and 4.5 T, for carbon-substituted MgB2 synthesized at 850 °C was enhanced by more than four times compared with unsubstituted MgB2. The observed improvement is due to the formation of efficient pinning centers resulting from the incorporation of carbon substituting for boron in MgB2. Furthermore, x-ray photoelectron spectroscopy (XPS) confirmed the presence of carbon bonding to boron in MgB2 synthesized with biowaste-derived CDs, indicating successful incorporation into the structure. Ultraviolet photoelectron spectroscopy (UPS) results show that the carbon-substituted MgB2 can lead to changes in the electronic band structure and values of work function. These changes significantly impact the properties of MgB2 materials, including superconducting transition temperature, upper critical field, and critical current density. The XPS and UPS experimental results are in good agreement with density functional theory calculations for MgB2 with and without carbon substitution. [ABSTRACT FROM AUTHOR]

Sn–Pb solders are superconducting materials whose Sn and Pb are perfectly phase-separated. Recently, anomalous magnetic-flux trapping in a Sn45–Pb55 solder has been revealed, where the magnetic fluxes are selectively trapped in the Sn regions due to the supercurrents in the surrounding Pb regions. Here, we report on the observation of the anomalous critical field (Hc)-temperature (T) phase diagram of superconductivity in the Sn45–Pb55 solder. Although the Hc(T) for the Pb regions decreases with increasing field as in normal type-I superconductors and is consistent with the conventional trend with Hc(0) ∼ 800 Oe, the Hc(T) for the Sn regions exhibits anomalous behaviors. The most noticeable trend was observed in the field-cooled (under 1500 Oe) solder. The Hc-T phase diagram for the Sn regions largely varies when the applied external field is reversed, and Tc increases with increasing field amplitude when H < 0 Oe is applied. On the basis of the flux trapping and the observed anomalous Hc-T phase diagrams, we propose that the field-robust superconductivity in the Sn regions is related to the ferromagnetically aligned magnetic fluxes (or formation of vortices) in the Sn regions of the Sn45–Pb55 solder. [ABSTRACT FROM AUTHOR]

This study assessed the effect of Bacillus megaterium on seedling growth of Glycyrrhiza uralensis Fisch. under control and phosphorus (P) deficiency conditions. The results showed that P deficiency improved 1) G. uralensis root growth, 2) superoxide dismutase, catalase, and peroxidase activities, 3) inorganic P, starch, and soluble sugar contents in roots, 4) dissipated energy flux per reaction center, trapped energy flux per reaction center, and absorption flux per reaction center, and 5) net photosynthetic rate, stomatal conductance, transpiration rate, maximum fluorescence intensity after dark adaptation, and variable fluorescence. However, P deficiency significantly decreased chlorophyll and carotenoid contents in G. uralensis, but enhanced chlorophyll and carotenoid contents in B. megaterium. Our findings on the regulatory mechanisms of B. megaterium in response to P starvation hold promise for improving the success of G. uralensis cultivation. [ABSTRACT FROM AUTHOR]

In this paper, the study investigates the effect of magnetic relaxation on the ac susceptibility in type-II superconductors. To this end, the flux creep equation of ac response is deduced, and the characteristic relaxation time is modified. The relaxation effect is a key feature of flux creep. The results show that the change of the effective relaxation time directly affects the effective potential barrier and the approximate relaxation rate of the superconductor at a certain frequency when the critical current density and critical temperature are fixed, which in turn can cause significant changes in the imaginary part of the AC susceptibility. The results are expected to contribute to a better understanding of the flux dynamics of superconductors from a theoretical perspective. [ABSTRACT FROM AUTHOR]

FeSe1−xTex superconductor has a relatively simple crystal structure and a high superconducting transition temperature in bulk form at ambient pressure, which gives it great application potential. In this study, Nb is selected to partially replace Fe in FeSe0.4Te0.6 and a series of Fe1−xNbxSe0.4Te0.6 single crystals with x = 0, 0.01, 0.03, 0.06, and 0.1 were synthesized using the self-flux. The crystal structure and superconductivity are characterized by XRD and magnetization measurements. The fish-tail peak effect was observed in samples with x = 0, 0.01, and 0.03. The critical current density of the three samples with x = 0, 0.01, and 0.03 is estimated by using the Bean model. According to the Dew-Hughes model, the effect of Nb doping on the magnetic flux pinning behavior of FeSe0.4Te0.6 is also investigated. [ABSTRACT FROM AUTHOR]

Geometry-induced domain wall pinning has been studied in heterostructure with soft magnet Fe3Pt and hard magnet FePt. It is demonstrated that the domain wall is pinned at the interface region of the Fe3Pt/FePt heterostructure under a small current field owing to the spin-transfer torque. The pinning of the domain wall is strongly dependent on the geometry of both soft and hard magnets. The thickness of the heterostructure Fe3Pt/FePt has an important influence on the pinning of the domain wall, which is caused by the combined effects of demagnetization, exchange coupling, and anisotropy. Moreover, with an increase in the width of the hard magnet FePt, the current of the pinning domain wall increases. With an increase in the width of the soft magnet, Fe3Pt, the pinning current decreased to a minimum value and then increased. These results are helpful for the fabrication and design of magnetic storage devices. [ABSTRACT FROM AUTHOR]

This study proposes a modeling process for conveniently analyzing the thermal resistance of a double-sided cooling (DSC) power module used in automotive inverters. Conventionally, circular-shaped pin-fins are adopted in the heat sinks used in DSC modules. This study utilizes finite element method (FEM) simulation to estimate the junction-to-fluid thermal resistance and compares the simulation results with measured values. The modeling process achieves high accuracy, approximately 97%. The analysis involves an optimized design of the circular pin-fins, exploring parameters such as pin–fin spacing and diameter size. This optimization results in a sufficiently low device junction temperature while maintaining an acceptable pressure drop. Furthermore, the developed model is applied to two uncommon pin–fin shapes, cone and oval, and their performance is evaluated. The oval-shaped pin-fins reduce the device temperature by approximately 6.7%, from 156.2 to 145.7 ℃, with a slight increase in pressure drop from 2.18 to 2.92 kPa. However, this pressure drop is low enough to supply coolant to a xEV cooling system. These findings enhance the accuracy of thermal resistance analysis for DSC power modules and offer a cost-effective means of estimating results without the need for direct manufacturing and measurement of pin–fin shape changes. [ABSTRACT FROM AUTHOR]

In this study, for the first time, we present a systematic study of the critical current density Jc at two magnetic field orientations and in a single crystal of the superconducting pnictide EuCsFe4As4, which shows a magnetic ordering below Tc and belongs to the 1144 family. The anisotropy of Jc and its temperature dependence are determined. The exponents of the dependences from 0.1 to 1 T are in a good agreement with the theoretical predictions for strong Abrikosov vortex pinning, which is also confirmed by the values of the pinning strength estimated using the Dew-Hughes model. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive analysis of the effects resulting from the substitution of biowaste-derived carbon-dot (CD) from human hair on structural and superconducting properties of MgB2. Syntheses of polycrystalline samples were accomplished through a standard solid-state reaction route. X-ray powder diffraction results confirm the formation of MgB2 as a primary phase in all samples and show the successful substitution of carbon for boron in MgB2. The critical current density, determined at 20 K and 4.5 T, for carbon-substituted MgB2 synthesized at 850 °C was enhanced by more than four times compared with unsubstituted MgB2. The observed improvement is due to the formation of efficient pinning centers resulting from the incorporation of carbon substituting for boron in MgB2. Furthermore, x-ray photoelectron spectroscopy (XPS) confirmed the presence of carbon bonding to boron in MgB2 synthesized with biowaste-derived CDs, indicating successful incorporation into the structure. Ultraviolet photoelectron spectroscopy (UPS) results show that the carbon-substituted MgB2 can lead to changes in the electronic band structure and values of work function. These changes significantly impact the properties of MgB2 materials, including superconducting transition temperature, upper critical field, and critical current density. The XPS and UPS experimental results are in good agreement with density functional theory calculations for MgB2 with and without carbon substitution. [ABSTRACT FROM AUTHOR]

FeSe1−xTex superconductor has a relatively simple crystal structure and a high superconducting transition temperature in bulk form at ambient pressure, which gives it great application potential. In this study, Nb is selected to partially replace Fe in FeSe0.4Te0.6 and a series of Fe1−xNbxSe0.4Te0.6 single crystals with x = 0, 0.01, 0.03, 0.06, and 0.1 were synthesized using the self-flux. The crystal structure and superconductivity are characterized by XRD and magnetization measurements. The fish-tail peak effect was observed in samples with x = 0, 0.01, and 0.03. The critical current density of the three samples with x = 0, 0.01, and 0.03 is estimated by using the Bean model. According to the Dew-Hughes model, the effect of Nb doping on the magnetic flux pinning behavior of FeSe0.4Te0.6 is also investigated. [ABSTRACT FROM AUTHOR]

Dynamic strain aging (DSA) is induced by the coexistence of deformation-induced martensitic transformation (DIMT) and deformation twins (DTs) at 50 °C and 75 °C. DIMT can provide high diffusivity paths for carbon atoms from α′-martensite to α′/γ interfaces. A high density of nanoscale DTs is activated at α′/γ interfaces during subsequent deformation, which represents high-frequency emission of dislocations from interfaces, and the repeated pinning process of emitted dislocations by carbon atoms contributes to DSA effects. [ABSTRACT FROM AUTHOR]

The critical current density (Jc) of a superconductor with a high transition temperature is a fundamental quantity that determines the scope of the application of new superconductors in practice. Reports show that the critical transport current density of thin films of yttrium-based superconductors grown by different methods can range from the value106A/cm2' in temperature77k° to a value of the 107A/cm²order of4 ko. These values of current density provide the use of superconductors on a small scale in the electronic industry In this work, the dependence of the critical transfer current density of type II flat superconductor with a rectangular cross-section that is mixed in three magnetic fields that are applied perpendicular to the surface of the superconducting strip is investigated. The results of these calculations clearly show that (a)- as the thickness of the superconducting sample increases, the critical current density decreases (b)- the comparison of the results of the calculations of the application of three different fields indicates that with the increase of the field, it decreases. [ABSTRACT FROM AUTHOR]