Value Of Critical Temperature Research Articles

Vortex phase diagram and transition in (Bi1.6Pb0.4Sr2Ca2Cu3O10-δ)1-x(SnO2)x superconductors

The superconducting vortex phase diagram of (Bi1.6Pb0.4Sr2Ca2Cu3O10-δ)1-x(SnO2)x ceramics, where x = 0, 0.002, 0.004, 0.006, 0.008, and 0.010, was investigated using resistivity measurement under magnetic fields. If the value of the offset critical temperature (Tc,offset) monotonously decreased on the SnO2-added samples, then the mean-field critical temperature (Tmf) would slightly improve on the x = 0.002 sample. The excess conductivity of all samples was analyzed based on the Aslamazov–Larkin and Lawrence–Doniach models. The c-axis coherence length at 0 K (ξc(0)) and the interlayer coupling strength were optimized on the x = 0.002 sample. The activation energy (U0) calculated using the Arrhenius model was also increased, and the maximum for the x = 0.002 sample was reached. The upper critical field (Bc2) deduced using the Werthamer–Helfand–Hohenberg model was also enhanced for the x = 0.002 sample. The small bundle field (Bsb), large bundle field (Blb), irreversibility field (Birr), and Bc2 were combined for the vortex phase (B-T) diagram of the x = 0.000 and x = 0.002 samples. All pinning regimes of the x = 0.002 sample were extended, clearly revealing the improvements in the flux pinning properties in that sample.

Optical response in a high-TcYBCO nanowire

We demonstrate the optical response from high-Tc superconductor nanowires at temperatures above that of liquid nitrogen. Using hard oxide Al2O3 as a mask material, we achieved miniaturized YBa2Cu3O7−δ wires with widths nearing 100 nm, a significant milestone for highly sensitive photodetectors. We investigated the photoresponse of these nanowires at temperatures almost an order of magnitude higher than previously reported, under varying temperature and bias current conditions. Our findings reveal a strong correlation between the optical response and the critical parameters of the superconductor, with peak optical responses close to the critical values of temperature and bias current density. Nanowire response to wavelengths from visible to near-infrared range demonstrated a pronounced absorption maximum at temperatures below Tc. These results lay a solid foundation for the development of high-Tc superconductor nanowire single-photon detectors, understanding of nanoscale high-Tc superconductor structure optical behavior, and advancing the prospects of quantum technologies.

A recipe for an effective selection of promising candidates for high-temperature superconductors among binary hydrides

Recent research on compressed binary hydrides have unveiled the potential for achieving superconductivity at near-room-temperature. Nevertheless, the available decision-making procedures standing behind the selection of constituent elements that may potentially exhibit high values of critical temperature (Tc) are far from optimal. In other words, a lot of experimental and numerical effort is wasted on exploring unpromising compounds. By conducting a deep study of a database containing over 580 binary hydride superconductors, we were able to observe some interesting relationships between Tc and selected physico-chemical properties of examined compounds. Among studied parameters, the ratio of the sum of the molecular weight of heavier atoms to the total mass of all hydrogen atoms in the chemical formula of hydride (MX/MH) was found to be the most valuable indicator that can help to screen for new promising superconductor candidates. This is because the highest Tc requires the lowest MX/MH ratio. Statistical analysis indicates a 28% chance of finding Tc > 200 K within 0 <MX/MH < 15. It is expected that these findings will not only allow for more efficient use of resources by improving future superconductor candidates selection but also they will accelerate ongoing experimental and numerical research that should bring new exciting discoveries in a much shorter time.

Europium-Subsituted Bismuth-Based Superconductors: Structural and Thermal Analysis via Chemical Sol-Gel Synthesis

The synthesis and characterization of Bi1.7-xPb0.3EuxSr2Ca2Cu3O10+δ superconductors with Eu substitution at varying ratios were investigated to determine their structural, electrical, and thermal properties. A sol-gel technique followed by calcination was employed to prepare samples with different substitution ratios. X-ray diffraction (XRD) was used for structural analysis, electrical properties with aid of nitrogen fluid measured by electrical resistivity, thermogravimetric analysis (TGA) conducted for thermal properties , and differential scanning calorimetry (DSC) were utilized for characterization" to improve clarity. XRD analysis revealed that the highest proportion of the high-temperature superconducting (HTS) phase occurred at a substitution factor of 0.2, corresponding to the highest critical temperature (Tc) value of 112 K. Raman spectra were conducting and showed a certain shifting with different substitution levels of Eu element. The thermal analysis highlighted the impact of substitution factor x on thermal stability, with the sample at x=0.2 exhibiting the highest thermal stability. TGA curves showed mass loss behavior for different x values, with distinct regions indicating the presence of residuals. The successful synthesis and characterization of these superconductors hold promise for practical applications.

Magnetic and Magnetocaloric Properties of C56 like-Fullerene Structure: A Monte Carlo Study

We explored the magnetic and magnetocaloric properties of the C56 Fullerene-like system formed by the mixed spins 2 and 3/2. We applied Monte Carlo simulations using the Metropolis algorithm and show the effects of different physical parameters. We also established the ground state phase diagrams, at zero reduced temperature, in different planes formed by the reduced external magnetic field, the reduced coupling interaction between the mixed spins, and the reduced crystal field. We found that the total magnetizations predict a specific reduced critical temperature value, confirmed by the peaks observed in the magnetic susceptibilities. To elucidate the behavior of the magnetic entropy changes -ΔSm, of the C56 system, for several external magnetic field values we show that the reduced critical temperature value tC increases when increasing the reduced external magnetic field. In addition, we show the dependency of the maximum “magnetic entropy change” as a function of the reduced external magnetic field. We found an almost linear increase for this parameter when increasing the reduced external magnetic field values. The obtained hysteresis cycles of the studied system showed a decreasing effect of the reduced crystal field followed by a decrease of the magnetic hysteresis surface cycles, as well as the corresponding reduced coercive magnetic field values.

Superconductivity in breathing kagome-structured C14 Laves phase XOs2(X = Zr, Hf)

Recently, the emergence of superconductivity in kagome metals has generated significant interest due to its interaction with flat bands and topological electronic states, which exhibit a range of unusual quantum characteristics. This study thoroughly investigates largely unexplored breathing kagome structure C14 Laves phase compounds XOs2 (X = Zr, Hf) by XRD, electrical transport, magnetization, and specific heat measurements. Our analyses confirm the presence of the MgZn2-type structure in ZrOs2 and HfOs2 compounds, exhibiting type-II superconductivity with critical temperature ( TC ) values of 2.90(3) K and 2.69(6) K, respectively. Furthermore, specific heat measurements and electron–phonon coupling constants for both compounds indicate weakly coupled fully gapped superconductivity.

Assessment of superconducting and structural stability of advanced Y-123 and Y-358 ceramics with Tb/Y substitution in main matrices

In this study, the performances of Y1-x(Tb)xBa2Cu3O7-δ (Y-123) and Y3-x(Tb)xBa5Cu8O18-δ (Y-358) advanced ceramics prepared by sol-gel preparation route are investigated by the advanced characterization methods including X-ray diffraction (XRD), temperature dependent resistivity (ρ-T), vibrating sample magnetometry (VSM), scanning electron microscopy (SEM) and energy distribution spectroscopy (EDS) measurements and theoretical approaches. The EDS results illustrated that the Tb impurities were replaced successfully by the yttrium sites in the YBa2Cu3O7-y main matrix. Similarly, it was noted that the presence of excess impurities in the crystal structure led to the oxygenation problems. Electrical properties were determined by temperature dependent resistivity (ρ-T) measurements. ρ-T results indicated that Tb doping reduced the critical transition temperature (Tc) values for the transition to superconductivity for all samples in two YBCO phases. Although it appears to have negative effects of Tb ions on the number of mobile charge carrier concentrations in the σ antibonding in-plane Cu-O bonds, bipolaron formations in the polarizable lattices, oxidation states, and amplitude of the pair wave function of both phases, the other valuable properties (morphology, crystallinity quality, interaction between adjacent layers, critical current density, and flux pinning ability) were noted to improve remarkably in the case of the optimum amount in the Y-123 superconducting phase. In this context, the Y-358 superconducting phase was harshly affected by the substitution due to the change of the ortorombicity, localization problem, impurity phases, structure stabilization, crystal structure quality, crystallization system, homogeneities of oxidation states, oxygen ordering degree, and impurity scatterings. Besides, the analysis of the fluctuation induced conductivity indicated that the Y-123 ceramics with longer c-axis coherence length and less anisotropic nature exhibited well superconducting properties. Additionally, the doping ratio of x=0.01 led to the formation and distribution of more nucleation centers for the thermal fluxon motions of 2D pancake vortices. Similarly, the optimum Tb doped Y-123 system exhibited much durable to applied field strengths due to the best interaction quality between grains. Accordingly, this study recommended that the Y1-x(Tb)xBa2Cu3O7-δ advanced ceramic structure with new functionalities can find much more application areas in innovative, heavy-industrial technologies, and advanced engineering-related sectors.

Elastic, electronic, magnetic and magnetocaloric properties of janus MnXO (X=S, Se and Te) monolayers: First-principles and Monte Carlo investigations

In this work, we present the first theoretical analysis of the elastic, electronic, magnetic and magnetocaloric properties of 1T-phase Janus MnXO (X = S, Se and Te) monolayers using first-principle calculations based on density functional theory combined with Monte Carlo simulation. The stability of the studied monolayers has been analyzed by using the elastic constants Cij and formation energy, which indicate that all monolayers are stable. Moreover, the electronic properties reveal the metal characteristics of all monolayers, with a total magnetic moment of 3.25 μB, 3.81 μB and 4.09 μB for MnSO, MnSeO, and MnTeO, respectively. Further, the extracted critical temperature values (Tc) from Monte Carlo simulation are Tc = 115 K, Tc = 130 K and Tc = 82 K, for MnSO, MnSeO and MnTeO, respectively. Interestingly, the predicted maximum magnetic entropy change −ΔSmax and maximum relative cooling power RCP (and adiabatic temperature change) are 10,38 J/kg.K and 763,43 J/kg (7,11 K) for MnSO, 6,79 J/kg.K and 515,57 J/kg (3,25K) for MnSeO, and 6,39 J/kg.K and 407,16 J/kg (3,46 K) for MnTeO at a magnetic field of 5T. These results suggest that the Janus MnXO (X = S, Se and Te) monolayers are a potential materials for use in magnetic nanodevices and low-dimensional magnetic refrigeration.

Epitaxial growth and characterization of (110)-oriented YBCO/PBCGO bilayer and YBCO/PBCGO/YBCO trilayer heterostructures

We have grown and characterized (110)-oriented YBa2Cu3O7−x (YBCO)/PrBa2(Cu0.8Ga0.2)3O7−x (PBCGO) bilayer and YBCO/PBCGO/YBCO trilayer heterostructures, which were deposited by pulsed laser deposition technique for the nanofabrication of (110)-oriented YBCO-based superconductor (S)/insulator (I)/superconductor (S) tunneling vertical geometry Josephson junction and other superconductor electronic devices. The structural properties of these heterostructures, investigated through various x-ray diffraction techniques (profile, x-ray reflectivity, pole figure, and reciprocal mapping), showed (110)-oriented epitaxial growth with a preferred c-axis-in-plane direction for all layers of the heterostructures. The atomic force microscopy measurement on the top surface of the heterostructures showed crack-free and pinhole-free, compact surface morphology with about a few nanometer root mean square roughness over the 5 × 5 μm2 region. The electrical resistivity measurements on the (110)-direction of the heterostructures showed superconducting critical temperature (Tc) values above 77 K and a very small proximity effect due to the interfacial contact of the superconducting YBCO layers with the PBCGO insulating layer. Raman spectroscopy measurements on the heterostructures showed the softening of the Ag-type Raman modes associated with the apical oxygen O(4) and O(2)-O(3)-in-phase vibrations compared to the stand-alone (110)-oriented PBCGO due to the residual stress and additional two Raman modes at ∼600 and ∼285 cm−1 frequencies due to the disorder at the Cu–O chain site of the PBCGO. The growth process and structural, electrical transport, and Raman spectroscopy characterization of (110)-oriented YBCO/PBCGO bilayer and YBCO/PBCGO/YBCO trilayer heterostructures are discussed in detail.

Optical Controlling of Thermal Parameters in a Nano-Body Containing Lithium Niobates Molecules

Thermal parameters including entropy, specific heat and thermal energy of a nanobody containing lithium niobates are theoretically investigated. When zero-index is present, these thermal quantities are controllable via the manipulation of optical parameters and geometry. Our exploration is started from the calculation of the thermal parameters in the THz gap, whose wavelength is ranging from 30 μm to 3 mm. It can be noted that the value of the entropy and specific heat is increasing when the wavelength is increasing in this optical range. Furthermore, we investigate its thermal behavior in the case of long wavelength, ranging from 3 mm to 650 m. It can be found that the variation of the entropy, the specific heat and the thermal energy from positive to negative, which indicates the transition from the thermal radiation to thermal absorption. Still, we calculate the value of critical temperature associate with the zero-index, it can be seen that these values of the temperature is modulated by the combining of the optical parameter and the wavelength. Several transitions of the thermal energy from the positive value to negative value can be seen. Our study shows potential and flexible application of optics in modulating the thermal quantities.

Study on the dynamic thermal response of phase change material integrated wall under indoor-outdoor dual thermal disturbances

The study mainly explored the dynamic thermal response of phase change material integrated wall (PCMW) under indoor-outdoor dual thermal disturbances (IODTD). A dual wave thermal disturbance dynamic boundary condition was proposed for PCMW based on the outdoor meteorological data and typical solar energy building analytical models of Lhasa, Yinchuan and Xi'an in China. The influence of different construction modes on the thermal performance of PCMW was numerically investigated by the sensible heat capacity method under IODTD. Then determined the crucial thermophysical parameters of PCM and analyzed the variation characteristics of temperature and heat flux fields of PCMW. The heat transfer frequency responses of different walls to outdoor thermal disturbances were calculated by the harmonic response method. The results indicated that the optimal location of PCM was on the interior side of the wall, and the critical values of phase change temperature and latent heat were 16 °C and 120 kJ/kg, respectively. It presented the maximum temperature and heat flux were 10 % and 36.2 % greater than ordinary walls (OW). Compared with OW, the attenuation and delay time of PCMW on outdoor sol-air temperature wave performed significantly, which plotted a higher decrement factor and longer time lag under external disturbances of different orders.

Prediction of radiation embrittlement of VVER-1000 RPV welded seam material at lifetime extension up to 60 years and more

The correctness of the model assumption about additivity of the contributions of hardening (formation of dislocation loops and radiation-induced precipitates) and non-hardening (formation and accumulation of grain boundary segregations) mechanisms to the final radiation embrittlement of VVER-1000 RPV weld materials has been verified. The paper presents the results of the experiment to obtain predicted values of the critical embrittlement temperature of weld metal with nickel content of 1.59–1.88% using accelerated irradiation in the IR-8 research reactor from states characterized by different starting level of grain boundary segregation. The procedure of accounting for the flux effect for the values of critical embrittlement temperature obtained using accelerated irradiation has been proposed. The conservativity of the weld metal radiation embrittlement dependence has been verified based on the modal assumption of additivity of the contributions of the strengthening and non-strengthening mechanisms up to the values of fast neutron fluence ~75–1022 neutrons/m2.

ЗАВИСИМОСТЬ ТЕМПЕРАТУРЫ ПЕРЕДНЕЙ ПОВЕРХНОСТИ ТОКАРНОГО РЕЗЦА ОТ ЭВОЛЮЦИОННЫХ ИЗМЕНЕНИЙ ТРИБОДЕФОРМАЦИОННЫХ ПОКАЗАТЕЛЕЙ ПРОЦЕССА ОБРАБОТКИ

The study objective is modeling the temperature distribution on the surface of a heavily loaded tribocontact - front surface of a lathe tool - chips taking into account evolutionary changes in the cutting system.&#x0D; The task to which the paper is devoted is to assess the influence of evolutionary changes of tribodeformation parameters of the cutting process on the average and maximum temperature of the front surface of the lathe tool.&#x0D; Research methods. Contact temperatures are found out on the basis of mathematical modeling using data obtained during field experiments at longitudinal turning of 15X2NMFA steel blanks without cooling by T15K6 hard alloy plates. During resistance tests, the chip contact length with the front surface and the chip reduction coefficient used for calculation are determined, as well as the average temperature in the cutting zone, the value of which is used to assess the adequacy of the results obtained by digital modeling. &#x0D; The novelty of the work. Forecasting the temperature increase on the front surface of the cutter, taking into account the contribution of evolutionary changes in tribodeformation parameters of cutting.&#x0D; The results of the study. In the studied cutting system, according to the results of resistance tests, a decrease in the chip reduction coefficient is recorded over the processing time. The temperature distribution on the front surface of the cutter is modeled in two versions: taking into account the evolutionary adjustment of the chip reduction coefficient and related parameters – sliding velocity and thickness of the plastically deformed layer in the chip, and without taking into account their changes. It is found out that modeling adjusted for changes in tribological indicators allows to obtain calculated values of the temperature of the front surface closest to the experimentally recorded of average temperature in the cutting zone. &#x0D; Conclusions: Forecasting contact temperatures adjusted for evolutionary changes in tribodeformation parameters will allow to determine more accurately the moment in the evolution of the cutting system at which critical temperature values can be reached, and further processing is associated with the risk of critical wear or deterioration of the treated surface.

Force Field for Calculation of the Vapor-Liquid Phase Equilibrium of trans-Decalin

Based on the TraPPE force field, previously unknown values of the parameters of the intermolecular interaction potential of trans-decalin were determined. Parametrization was carried out using experimental data on saturated vapor pressure and density at atmospheric pressure. The found parameters make it possible to adequately describe the boiling and condensation lines of trans-decalin and also predict the critical values of pressure, density, and temperature with satisfactory accuracy. Calculations of vapor-liquid phase equilibrium conditions for a binary CO2—trans-decalin mixture in supercritical conditions for CO2 were carried out. When quantitatively comparing the calculated values with experimental data, an underestimation of pressure at a temperature of 345.4 K by 30% is observed, which decreases to 5% for temperatures up to 525 K.

Fulfilling modern astrophysical observations and lattice QCD constraints based on a nonlocal NJL model with 3D form factor

AbstractIn the present work, we employ a nonlocal Nambu–Jona–Lasinio (NJL) model with a Gaussian form factor that is dependent on the spatial components of the momentum (3D‐FF). Focusing on the temperature‐baryon chemical potential plane, we investigate some aspects of the phase diagram. Initially, we propose an assumption that the range of interactions in momentum space may be modified by temperature, allowing us to obtain the critical temperature values based on lattice QCD (LQCD) predictions. Subsequently, we consider this model within a hybrid framework to examine the effects of temperature, together with neutrino trapping, in compact object configurations.

FRACTAL NANOPARTICLES OF PHASE-SEPARATING SOLID SOLUTIONS: MORPHOLOGY-DEPENDENT PHASE EQUILIBRIA IN TUNGSTEN HEAVY PSEUDO-ALLOYS

In this paper, we simulate thermodynamically the morphology-dependent phase equilibria in core-shell nanoparticles of a phase-separating solid solution using the example of W-Cr heavy alloy. The morphology of a nanoparticle is described in the framework of the fractal geometry methods. Itis shown that there are two possible heterogeneous states in a nanoparticle while the compositions of phases in both states differ from each other. The dependences of mutual solubilities of components on the temperature are obtained while the behavior of these dependences significantly differs depending on the particular state and the morphology of nanoparticle under consideration. In nanoparticles of a very complicated morphology, the phase separation itself gets suppressed and the nanoparticle remains inthe homogeneous state at the temperatures significantly below the macroscopic value of the upper critical dissolution temperature. The demonstrated regularities are explained based on three mechanisms of reducing the free energy of the system and the “competition” between them. In the final section, a method for calculating the equlibrium size distributions and average characteristics of nanoparticle ensembles is described along with a technique of measuring nanoparticle fractal dimensions based on the microscopy data.

Rheology and agglomeration behavior of semi-crystalline polyamide powders for selective laser sintering: A comparative study of PA11 and PA12 formulations

In this study, we investigated the rheological behavior of various polyamide powders as a function of temperature, shear rate, and relative humidity. Near the glass transition temperature (Tg), powders exhibited an abrupt increase in static flow threshold, indicating caking due to particle agglomeration. At higher temperatures, a transition from elastic to plastic flow was observed around 80∘C, accompanied by changes in the plateau value of the shear modulus (G0′) for different powders. In the dense flow regime, a critical temperature value dictated the transition between caking (powder’s tendency to form lumps or masses) and free-flowing behavior, with temperature promoting agglomeration and shear rate causing dispersion. The critical temperature increased with the strain rate, highlighting the delicate balance between agglomeration and dispersion. Also, it is found that Relative Humidity (RH) plays a crucial role in reducing the stress developed within the sample and counteracting the temperature effect. Additionally, the slow compaction dynamics of powders were studied, revealing an inverse logarithmic law with a characteristic relaxation time (τ) that strongly correlated with the angle of repose.

A temperature and pressure dual-responsive, stretchable, healable, adhesive, and biocompatible carboxymethyl cellulose-based conductive hydrogels for flexible wearable strain sensor

The study aimed to develop a novel temperature and pressure dual-responsive conductive hydrogel with self-healing, self-adhesive, biocompatible, and stretchable properties, for the development of multifunctional anti-counterfeiting and wearable flexible electronic materials. A conductive hydrogel based on carboxymethyl cellulose (CMC) was synthesized by simple “one pot” free radical polymerization of CMC, acrylamide (AAm) and acrylic acid (AAc). The hydrogel displayed temperature responsiveness and possessed an upper critical solution temperature (UCST) value. In addition, hydrogels also had surprising pressure responsiveness. The synthesized hydrogels were characterized by FTIR, TGA, DSC, and XRD analysis. Importantly, the obtained hydrogels exhibited exceptional mechanical properties (stress: 730 kPa, strain: 880%), fatigue resistance, stretchability, self-healing capability, self-adhesive properties, and conductivity. In addition, valuable insights were obtained into the synthesis and application of flexible anti-counterfeiting and camouflage materials by the temperature and pressure dual-responsive hydrogels. Moreover, the prepared hydrogel, with an electrically sensitive perception of external strain (GF = 2.61, response time: 80 ms), can be utilized for monitoring human movement, emotional changes, physiological signals, language, and more, rendering it suitable for novel flexible anti-counterfeiting materials and versatile wearable iontronics. Overall, this study provided novel insights into the simple and efficient synthesis and sustainable manufacturing of environmentally friendly multifunctional anti-counterfeiting materials and flexible electronic skin sensors.

Experimental investigation of saturated vapor pressure and critical parameter for R1234ze(Z) (cis-1,3,3,3-tetrafluoropropene) and R1336mzz(Z) (cis-1,1,1,4,4,4-hexafluoro-2-butene)

In this study, metal-bellows variable volumetry was used to measure the saturated vapor pressures and critical parameters of R1234ze(Z) and R1336mzz(Z). The critical temperature, critical pressure, and critical density values were evaluated, and new vapor pressure correlations were formulated based on the obtained data. The low uncertainties of the measured values indicate the reliability and reproducibility of the data. The combined expanded uncertainties of critical temperature, critical pressure, and critical density were less than 50 mK, 21 kPa, and 0.6 % (k = 2, 0.95 level of confidence), respectively. 17 vapor pressure data points of R1234ze(Z) and 20 vapor pressure data points of R1336mzz(Z) were obtained at temperatures ranging from 260 K to 441 K. The combined expanded uncertainties of the temperature and saturated vapor pressure measurements were less than 20 mK and 2.2 kPa (k = 2, 0.95 level of confidence), respectively. The results provide important thermophysical data for the use of R1234ze(Z) and R1336mzz(Z) in HTHP, and can aid in the design and optimization of HTHP systems.

Effect of a Wake-Field on the Dissociation of Quarkonium in Collisional Quark–Gluon Plasma

We have studied wake effects on the dissociation of heavy quarkonia states J/ψ and Y by introducing an in-medium modification to the inter-quark potential. The wakes in the quark–gluon plasma were modeled using linear response theory using a dynamic dielectric function obtained from kinetic theory (Boltzmann equation) with a Bhatnagar–Gross–Krook (BGK) collision term. The in-medium modified potential was used to investigate the dissociation character depending on various parameters such as the velocity of quarkonium moving through the medium and the collision frequency. We have also calculated critical values of the dissociation temperature. Modifications of the dissociation energy due to wake-field effects were found.