Increase In Critical Temperature Research Articles

Crystal structures and electronic and magnetic properties of Janus bilayer Cl[formula omitted]Cr[formula omitted]I[formula omitted]

Two-dimensional (2D) magnetic material CrI3 has aroused extensive attention, because it could provide a new platform for investigating the relations between crystal structures and electronic and magnetic properties. Here, we study crystal structures and electronic and magnetic properties of three configurations (Cl–Cl I–I and Cl–I) of Janus bilayer Cl3Cr2I3 with two stacking orders (AB and AA1/3) by using the first principles approach incorporating the spin–orbit coupling (SOC) effect and the dipole correction. It is found that the spin polarization and the SOC effect can expand the lattice constant and the interlayer distance (ID) of the three configurations. Especially, the ID of the I–I configuration is 1 Å larger than that of the Cl–Cl configuration. The total energy calculation results show that the atomic configuration, the SOC effect and the stacking order play an important role in determining the magnetic ground states of the Janus layers. Our results indicate the atomic configurations of the Janus bilayers are not conducive to the increase of critical temperature. Interestingly, the Cl–I configuration has a vertical dipole moment, and its AFM state has large spin splitting. It is revealed that the non-periodic structure, the symmetry breaking of the average potential and the weak interlayer interaction lead to the vertical dipole moment and the abnormal AFM state that is not the most stable state.

Critical behaviours of anisotropic XY ferromagnet in the presence of random field

The anisotropic XY ferromagnet has been studied by Monte Carlo simulation in a three dimensional simple cubic lattice. The increase in critical temperature (ferro-para transition) has been noticed with increasing the strength of anisotropy. The effects of random fields (both with full circular symmetry and in angular window) on the critical temperature are investigated systematically in the anisotropic XY ferromagnet in three dimensions. Reduction of the critical temperature of anisotropic XY ferromagnet has been observed in the presence of random field. The compensating field (the required amount of field which preserves the critical temperature for isotropic XY ferromagnet) has been studied as a function of the strength of anisotropy. The compensating field was found to depend linearly on the strength of anisotropy. We have also studied the effects of random field confined in the angular window and observed the reduction of the critical temperature with increase of the angular extension. The critical behaviours are formalised by the usual finite size analysis and the estimation of critical exponents for the susceptibility and the specific heat.

Rotating SU(2) gluon matter and deconfinement at finite temperature

In this work a non-abelian gauge theory is reformulated in a rotating frame. With this new formalism, the influence of the background rotation on the color deconfinement transition for a pure SU(2) gluon system has been studied. The KvBLL caloron, which is a color neutral and topologically nontrivial solution of Yang-Mills equation at finite temperature, is reexamined under rotation and adopted as the confined vacuum of such a system. With rotation-modified solutions of the caloron's constituent solitons, i.e. dyons, the non-perturbative part of effective potential of the rotating system has been obtained. Combining with the perturbative potential by Gaussian fluctuations, the critical temperature of confinement-deconfinement phase transition is investigated. It is found that neither the rotational semi-classical potential nor Gaussian fluctuations can confine color charges more tightly when the rotation becomes faster. While only a stronger coupling constant is able to make the critical temperature increase with angular velocity, as what indicated in lattice simulations. And it is found a non-monotonic dependence of the critical temperature on the angular velocity is established because of the competition between these two contrary contributions.

Bipolaron Theory of Field Effect in High-Temperature Superconductors

Bipolaron Theory of Field Effect in High-Temperature Superconductors

Bipolaron Theory of Field Effect in High-Temperature Superconductors

Bipolaron Theory of Field Effect in High-Temperature Superconductors

Effects of the Mixing Process on the Rheological Properties of Waste PET-Modified Bitumen

This paper analyses the key findings of a study devoted to PET-modified bitumen. The research program was run according to the D-optimal experimental plan based on a factorial design. Five factors, i.e., the type of polymer (source), the type of bitumen (qualitative factors), PET amount, mixing rate, and mixing temperature (quantitative factors), controlled the bitumen–polymer mixing process. The experiment included a series of determinations of bitumen’s rheological characteristics obtained by MSCR (Jnr, R) and G*/sin(δ) at 50 °C, 60 °C, and 70 °C. The low-temperature properties of the composite (critical temperature) were evaluated using a BBR test. The findings showed that bitumen modification with PET primarily reduced the creep susceptibility of the bituminous–polymer mixture. The low-temperature characteristics of the modified bitumen played a secondary but essential role. The amount of polymer and the mixing rate interacted with the temperature, significantly reducing the stiffness of the composite, while the type and amount of bitumen had a substantial effect on the results obtained in the BBR test. It is worth noting that when combining bitumen and plastomer, special attention should be paid to ensuring a high level of homogeneity of the mixture by controlling the parameters of the mixing process accordingly. The tests and analyses provided crucial models (GLM), which allowed for the prediction of the plastomer-modified bitumen’s low- and high-temperature properties. The resulting relationships between factors and the identification of their impact on the bitumen properties enable a better understanding of the process of bitumen modification with PET. The conclusions presented here serve as a basis for future optimisation of the modified bitumen composition. The performed studies indicate that the use of >3% plastomer in bitumen 70/100 allows for a reduction in its susceptibility (MSCR) to below 0.5 kPa−1, making it suitable for bituminous mixtures for high-traffic roads. No significant increase in critical temperature (BBR) was observed.

Prediction of nodal-line fermion and phonon-mediated superconductivity in bilayer α-borophene

The electron deficiency of boron allows the formation of a variety of monolayer or few-layer two-dimensional structures (borophenes) with interesting physical properties. Recent experiments have also confirmed that interlayer covalent bonding makes the bilayer structure more stable than the monolayer. In this work based on α-borophene, we propose three free-stranding bilayer structures with dynamic stability. In these three metallic structures, the electronic band crossings around Fermi level form nodal lines. All these structures also exhibit strong electron-phonon couplings. The Bardeen–Cooper–Schrieffer superconducting critical temperature T c of the type-II structure went as high as 28.2 K, which was further improved to 32.0 K by the enhancement effect of Li adatom at the Debye frequency. However, no increase in critical temperature was observed in other Li-doping cases. Specifically, Li intercalation inside the bilayer causes a significant abrupt decrease in the critical temperature of type-I structure. Our results indicated that the bilayer borophene would be an ideal platform for the coexistence of topological electronic states and superconducting states.

Role of site–site interaction on the phase equilibria of multiple-site associating fluids in a functionalized slit pore

Vapor–liquid phase equilibria for multiple sites associating fluids with different associating strengths are investigated in a slit pore using grand-canonical transition matrix Monte Carlo method. The increase of critical temperature from two-site to four-site associating fluids at constant site strength is quite significant as compared to that of the one-site to two-site associating fluids, which is more pronounced at higher associating strength (ϵ* = 6). Monomer fraction and cluster size distribution are used to investigate the association of fluid particles in coexistence phases. The monomer fraction for both phases decreases with increased associating sites on the fluid particles due to more site–site interaction with neighboring fluid particles and forming a larger cluster. Therefore, the number of associating sites and their distribution play a vital role in the association of fluid particles. Moreover, the saturation chemical potential changes with the arrangement of the sites. For two-site associating fluids, we observe early vapor–liquid transition when the sites are oppositely placed, and when the sites are placed at 90°, the vapor–liquid transition is observed at the higher chemical potential. Moreover, four-site associating fluids with a square arrangement show early vapor–liquid phase transition, mainly because these arrangements of sites effectively interact with surface sites and the molecules in the next layer.

Study on the Re-ignition Characteristics of High-Temperature Oxidization & Water Immersion Long-Flame Coal at Different Heating Rates

ABSTRACT The water immersion residual coal tend to happen spontaneous combustion accidents after mining the coal seam. For exploring the oxidative re-ignition properties of high-temperature oxidized water-impregnated long-flame coal, the thermal evolution law toward each pre-oxidized coal soaked in water under varying heating rates (Rh) (5, 10, 15°C/min) has been analyzed by thermogravimetric differential scanning calorimetry (TG-DSC). The findings are as follows: the DTG at the critical temperature (T1) and maximum weight loss temperature (T5) increases, the activation energy (E) decreases, and the heat output increases (maximum 6391J/g) with the rising Rh. The violent oxidated reaction process of coal samples has been delayed as the Rh was 10°C/min. The water-immersed coal sample (I200) contains more free water on the surface, and the maximum (0.45 mW/mg) and total (178.8 J/g) heat absorption of are higher. Oxidation at 200°C and soaking in water (O200I200) reduced the ignition point temperature (minimum 399°C) and E (minimum 18.5 kJ/mol), and increased the total heat release (maximum 323 J/g) making it easier to oxidize and re-ignite. Under the same Rh, the oxidation and combustion traits of each pre-oxidized water-immersed coal (PWIC) remained unchanged. Reducing the Rh can effectively prevent spontaneous combustion of high-temperature oxidized water-soaked coal in shallow-buried and short-distance coal seams in northwest of China.

Ion-beam assisted sputtering of titanium nitride thin films

Titanium nitride is a material of interest for many superconducting devices such as nanowire microwave resonators and photon detectors. Thus, controlling the growth of TiN thin films with desirable properties is of high importance. This work aims to explore effects in ion beam-assisted sputtering (IBAS), were an observed increase in nominal critical temperature and upper critical fields are in tandem with previous work on Niobium nitride (NbN). We grow thin films of titanium nitride by both, the conventional method of DC reactive magnetron sputtering and the IBAS method, to compare their superconducting critical temperatures T_{c} as functions of thickness, sheet resistance, and nitrogen flow rate. We perform electrical and structural characterizations by electric transport and x-ray diffraction measurements. Compared to the conventional method of reactive sputtering, the IBAS technique has demonstrated a 10% increase in nominal critical temperature without noticeable variation in the lattice structure. Additionally, we explore the behavior of superconducting T_c in ultra-thin films. Trends in films grown at high nitrogen concentrations follow predictions of mean-field theory in disordered films and show suppression of superconducting T_c due to geometric effects, while nitride films grown at low nitrogen concentrations strongly deviate from the theoretical models.

Effects of massive gravity on s-wave holographic superconductor

In this paper, analytical investigation of the properties of [Formula: see text]-wave holographic superconductors in the background of a massive gravity theory in the probe limit has been carried out by employing the Sturm–Liouville eigenvalue method. We obtain the analytical expression for the relation between the critical temperature and the charge density. We also obtain the expression for the condensation operator and value of the critical exponent. We observe that as we increase the massive gravity couplings, the critical temperature increases and the condensate decreases. Then we compute the frequency dependence of conductivity by solving analytically the wave equation for electromagnetic perturbations. From the real part of the conductivity, we finally estimate the energy band gap. Our results show that as one keeps on increasing the coupling parameters of the massive gravity background, the band gap energy increases compared to the holographic superconductors constructed in the Einstein gravity background. The results indicate that massive background is more favorable than Einstein gravity background for constructing a gravity dual of the strongly coupled high [Formula: see text] superconductor as it enhances the value of the critical temperature.

Simulations of Temperature-Dependent Magnetization in FexGd100−x (20 ≤ x ≤ 80) Alloys

Theoretical calculations of the temperature-dependent magnetization in FeGd alloys were done with the use of Heisenberg-type atomistic spin Hamiltonian and Monte Carlo algorithms. The random allocation of atoms in the desired crystal structure was used for simulations of magnetically amorphous alloys. Performed calculations for the two different crystal structures have shown an important role of coordination number on the observed critical temperature and compensation point. Moreover, the value of the exchange interaction between Fe and Gd sublattices plays a key role in the simulations—an increase in the Fe–Gd exchange constant provides an increase in critical temperature for each concentration of elements, which explains the higher temperature stabilization of Gd moments. It was shown that obtained temperature-dependent magnetization behavior is consistent with experimental observations, which confirms the applicability of the atomic model used to study FeGd or other magnetic alloy structures.

Investigating the critical transitional temperature increase in graphene oxide doped bulk YBCO

Y1Ba2Cu3O7-δ (YBCO) was doped with thermally stable graphene oxide (TS-GO) and thermally unstable graphene oxide (TU-GO) in the following %wt. concentrations: 0.1, 0.5 and 0.7. TS-GO and TU-GO was characterized using RAMAN, fourier transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDX). The critical transition temperature (TCmid) increased in all TU-GO and TS-GO doped samples. The highest TCmid of 101 K was that of the 0.7 %wt. TU-GO doped sample. The increase in TCmid was greater for the samples doped with TU-GO. Non-stoichiometric oxygen content (δ) was seen to increase with an increase in doping concentration of both TS-GO and TU-GO. X-ray diffraction (XRD) analysis was carried out to determine the lattice parameters and phase characterization of the TU-GO and TS-GO doped samples. Lattice parameters show an increase in the copper oxide (CuO2) planar area with TCmid for TS-GO and TU-GO doping. To determine strain effects, the Williamson Hall method was used to determine the lattice strain (ɛ). The ɛ was seen to decrease for both TS-GO and TU-GO doped samples. The formation of magnetic manganese oxide nanoparticles in TS-GO and TU-GO doped samples was observed, and resulted from impurities found in the graphene oxide (GO) dopant material. The magnetic particles were extracted magnetically and characterized using EDX. YBCO was doped with trimanganese tetraoxide (Mn3O4) and manganese dioxide (MnO2) in a 0.1 and 0.2 %wt. concentration. The TCmid is seen to increase to 94 K and 104 K respectively for 0.1 %wt. MnO2 and Mn3O4 doped samples. The 0.2 %wt. doped Mn3O4 sample resulted in a decrease in TCmid. Magnetic susceptibility measurements confirmed a superconducting phase changes. The increase in TCmid above YBCO’s Tc = 93 K, correlates to the presence of manganese nano-impurities. This increase is hypothezied to be related to an increase in surface area of YBCO’s 2D copper oxide (CuO2) plane structure with GO doping.

The thermo-mechanical behavior of NiTi-X shape memory alloys

A commercial NiTi alloy with the chemical composition of 54.5 Ni-45.5 Ti (mass %) was used as a standard material to be compared with Ti50Ni45Cu5, 48 Ni-37 Ti-15 Nb (mass. %) and 48 Ni- 37 Ti-15 Ta (mass. %). The experimental alloys were cast, annealed and hot rolled in order to render the material more compact and to obtain 0.5 mm-thick lamellas. Two types of specimens were then obtained. The former were fragments with a mass of less than 50 mg that were cut and cleaned in alcohol, in an ultrasonic bath, before being subjected to differential scanning calorimetry (DSC) analysis. The latter were 0.5 × 4 × 25 mm rectangular specimens that were prepared to be subjected to dynamic mechanical analyses (DMA) and optical analysis (OM). The DSC investigation program comprised a heating–cooling cycle with a rate of 10 K/min and was used in order to obtain the critical transformation temperatures of direct and reverse martensitic transformations. DMA measurements consisting in a heating cycle with a heating rate of 5 K/min, a frequency of 1 Hz, a maximum deformation of 20 µm and a maximum of 9 N dynamical applied force, were used in order to observe the mechanical behavior under dynamic conditions. DSC tests suggested that Cu and Ta alloying led to an increase of critical temperatures of reverse martensitic transformation while Nb alloying dropped these critical temperatures as low as 0 °C. In addition, Ta alloying significantly increased the transformation temperatures. All the DMA thermograms emphasized a maximum of internal friction that could be associated with the reverse martensitic transformation. Storage modulus exhibited either continuous or step-like increase during heating, suggesting the presence of a thermoelastic transformation.

Safety, feasibility, and application of intraperitoneal gas-based hyperthermia beyond 43°C in the treatment of peritoneal metastasis: An in-vivo pilot study.

Background43°Celsius (C) is currently the highest temperature used in the treatment of peritoneal metastasis (PM). Despite sufficient data on water- based hyperthermic solutions in PM treatment, there is currently no information on gas-based hyperthermia extending beyond 43°C. This study is the first to provide in-vivo data on different organ systems during and after intraperitoneal gas-based hyperthermia beyond 43°C. The aim of this study is to explore in-vivo feasibility, safety, and efficacy of this novel concept from a biological perspective.MethodsFor this study, three swine were subjected to laparoscopy and subsequent gas-based intraperitoneal hyperthermia at 48°, 49° and 50°C under a high-flow air stream. Intraoperative data from multiple temperature sensors were analysed. Additionally, intraoperative anaesthesiologic and gasometrical data was analysed. Postoperatively, swine were monitored for one week and laboratory work-up was performed on postoperative days 1, 3 and 7.ResultsDuring gas-based intraperitoneal hyperthermia, anesthesiologic parameters did not exhibit critical values. No intra- or postoperative complications were observed. Distinct temperature measurements on the skin, cystohepatic triangle and esophagus did not display any temperature increase. Postoperative laboratory workup did not show any changes in hemoglobin, white blood cell count, platelets, or kidney function.DiscussionBased on our data, there are no safety concerns for the application of gas-based hyperthermia between 48 - 50°C. In fact, no critical systemic temperature increase was observed. With respect to possible limitations, further in-vivo studies are required to evaluate whether gas-based intraperitoneal hyperthermia may be a therapeutic option for PM patients.

Surface roughness effects on magnetic properties of thin films: A computational Monte Carlo study

By means of Monte Carlo simulation, a computational approach is proposed to investigate the surface roughness effects on the critical and hysteresis behaviors of Heisenberg ferromagnetic thin films. Here, the atomic sites of the film’s surface are changed systematically from their regular positions using a disorder parameter, thereby allowing us to smoothly interpolate between smooth and rough surfaces. Threshold values of the structural disorder level at which the system critical temperature increases are identified. Furthermore, the surface roughness increases is observed to have a profound impact on the system’s magnetic hysteresis loops. In particular, a significant increase in the loop’s area is observed as the roughness increases, thereby increasing the coercivity of the thin magnetic film.

Spatial variation of critical temperatures between snow and rain over Turkey

This study investigates the critical temperatures that separate rain and snow events by using hourly precipitation information, air and dew point temperatures. The study period was taken to be 1997–2016 for air temperatures and 2007–2016 for dew point temperatures. In the study, only the winter season was taken into account, as it includes both snow and rain observations. During the study period, 8 different winter periods were identified for different parts of the country. To define the temperature at the onset of each precipitation event, an interpolation was applied to hourly air temperature values. It is found that critical air temperature values range from 0.5 to 2.2 °C with an average value of 1.4 °C. In addition to critical actual temperature, critical dew point temperatures vary from − 2.1 to 1.3 °C with an average value of − 0.2 °C. As a result of this investigation, only a statistically significant relationship was found between relative humidity and critical dew point temperature. This relationship states that approximately 8–9% increase in relative humidity may cause 1 °C increase in critical dew point temperature.

Predicting the superconducting transition temperature and relative resistance ratio in YBa[formula omitted]Cu[formula omitted]O[formula omitted] films

The increase in critical temperature, Tc, of high-temperature superconductors fulfills the needs of practical applications with liquid-helium-free refrigeration and a delay in magnet failure. The YBa2Cu3O7 (YBCO) superconductor exhibits Tc of greater than 90 K and an upper critical field of greater than 100 T, which is a promising candidate in high-field magnet design. Due to their large anisotropy in current transportation, YBCO superconductors are usually processed as thin films by pulsed-laser deposition. But the research requires significant manpower for materials synthesis, analysis, and quench detection, as well as costly equipment and facilities. In this work, we develop the multiple linear regression model to shed light on the relationship between pulsed laser deposition parameters and the superconducting transition temperature (Tc) and relative resistance ratio (rR) in the laser deposition of YBa2Cu3O7 films. The model is straightforward and simple and demonstrates a high degree of accuracy and stability, contributing to fast low-cost estimations of Tc and rR.

Self-heating ignition of large ensembles of Lithium-ion batteries during storage with different states of charge and cathodes

Self-heating is a possible cause of ignition of the open-circuit Lithium-ion battery (LIB) during storage. However, previous studies mainly focused on self-heating of a single cell, without considering the effect of heat transfer on large-size storage. In this study, a one-dimensional computational model, coded in the Gpyro, is used to study ensembles containing 1 cell to 5 million cells. Results show that ignition occurs at the central cell of the ensemble, while the outer surfaces remain at ambient temperature. As the length of ensembles increases from 0.01 m to 10 m, cell thermal runaway temperatures quantified using the critical temperature increase rate of 10 °C/min as defined in standard SAE-J2464 are insensitive to ensemble size, decreasing from 188 °C to 184 °C, but the critical ambient temperature triggering ignition decreases with size from 183 °C to 98 °C. This shows that the critical ambient temperature should be used to guide storage rather than the standard suggested critical temperature increase rate, which does not represent the criticality of ignition. The model predicts that higher state of charge (SOC) cells are easier to self-ignite. An ensemble containing 5 million 80% SOC cells can self-ignite at 40 °C. Self-heating ignition propensity of the Lithium Cobalt Oxide cathode LIB is larger, compared with Lithium Nickel Cobalt Manganese Oxide cathode. This study finds that the SAE-J2464 standard is not sufficiently robust to understand self-heating ignition during storage, and predicts the effect of the SOC and cathode chemistry on critical ambient temperature, contributing to the protection against LIB fires.

Study on the effects of reversible aging on the low temperature performance of asphalt binders

Reversible aging refers to a time-dependent stiffening of asphalt binder that results from the time-delayed increase in stiffness when the asphalt binder is stored at low temperatures. The increase in stiffness will distinctly affect the low temperature performance of the asphalt binder, but existing researches rarely consider this. This paper aims to investigate the effects of reversible aging on the low temperature performance of asphalt binders, and to reveal the underlying mechanism of reversible aging. To this end, four different types of asphalt binders were selected for the extended bending beam rheometer (EBBR) test at different conditioning times. The thermal stress was computed based on the rheological data obtained from the EBBR test to quantify the influence of low temperature reversible aging on the cracking resistance of the asphalt binders. The Avrami isothermal crystallization kinetics theory was used to analyse the reversible aging process of asphalt binders from the perspective of macro-crystal structure. Furthermore, the molecular dynamics was performed to simulate the reversible aging process of asphalt binders from a microscopic point of view. The results from this study show that the low temperature performance of asphalt binders continues to decline with the extension of the conditioning time, which is manifested by the increase in grade loss, thermal stress and critical cracking temperature. Reversible aging exhibits great impact on the low temperature performance of asphalt binders by lowering the low temperature grade of asphalt binders up to one grade. The Avrami isothermal crystallization kinetic theory can accurately characterize the reversible aging tendency of asphalt binders. The molecular dynamics simulation results show that the asphaltene component contributes the most to the reversible aging of asphalt binder.