Temperature Dependence Research Articles

Analyzing the Temperature Dependence of Titania Photocatalysis: Kinetic Competition between Water Oxidation Catalysis and Back Electron-Hole Recombination.

This study examines the kinetic origins of the temperature dependence of photoelectrochemical water oxidation on nanostructured titania photoanodes. We observe that the photocurrent is enhanced at 50 °C relative to 20 °C, with this enhancement being most pronounced (by up to 70%) at low anodic potentials (<+0.6 V vs RHE). Over this low potential range, the photocurrent magnitude is largely determined by kinetic competition between water oxidation catalysis (WOC) and recombination between surface holes and bulk electrons (back electron-hole recombination, BER). We quantify the BER process by transient photocurrent analyses under pulsed irradiation. Remarkably, we find that the kinetics of BER (∼90 ms half-time) are independent of temperature. In contrast, the kinetics of WOC, determined from the analysis of the photoinduced absorption of accumulated surface holes, are found to accelerate up to 2-fold at 50 °C relative to 20 °C. We conclude that the enhanced photocurrent densities observed in the low-applied potential region result primarily from the accelerated WOC, reducing losses due to the competing BER pathway. At higher applied potentials (>+0.6 V vs RHE), a smaller (∼10%) enhancement in photocurrent density is observed at 50 °C relative to 20 °C. Photoinduced absorption studies, correlated with studies using triethanolamine as a hole scavenger, indicate that this more modest enhancement at anodic potentials primarily results from an enhanced charge separation efficiency. We conclude by discussing the implications of these results for the practical application of photoanodic WOC under solar irradiation, influenced by these temperature-independent and -dependent underlying kinetic processes.

A MODEL FOR PAYNE EFFECT AND ITS VARIATION WITH TEMPERATURE

ABSTRACT A fully objective and thermodynamically consistent constitutive equation that models the Payne effect and its temperature dependence is presented. It is based on a Helmholtz-potential–based thermodynamic framework and the notion of evolving multiple natural configurations. The model uses four additional parameters than those necessary to describe the viscoelasticity at small deformations to capture the Payne effect of the material. In addition, it uses only one additional parameter to capture the temperature dependence of the mechanical behavior. The model was shown to describe experimental results of the Payne effect reasonably well over a temperature range of −20 to 100 °C.

Measurement of high-temperature absorption cross-sections using an optical cell with a non-uniform temperature distribution

A mathematical method to enable absorption cross-section measurements using an optical cell with a non-uniform temperature distribution is formulated, validated and experimentally demonstrated in this study. The motivation of the proposed method is to facilitate high-temperature spectroscopic studies in the long-wavelength mid-IR region, and to offer an alternative to highly engineered optical cells. The method is based on virtual segmentation of the non-uniform temperature field within an optical cell into bins, each having a sufficiently uniform temperature. By collecting a set of absorbance measurements corresponding to unique temperature profiles and expressing the temperature dependence of the absorption cross-section in terms of a model with limited number of unknowns, a closed-form system of equations is obtained which can be solved to evaluate absorption cross-sections. It is shown, through a set of simulated validation cases, that modeling the temperature dependence in terms of a third order polynomial results in accurate reconstruction of the cross-section spectra for a wide range of cases. Piece-wise polynomials and an alternative nonlinear model are proposed for improved accuracy and to model potentially complex temperature dependencies of the absorption cross-sections. To demonstrate the application of the proposed method, an optical cell with a non-uniform temperature profile was used to measure the cross-section spectra of methane over 1280 – 1330 cm-1 at temperatures up to 523 K. The proposed method is expected to be highly useful in collecting spectroscopic data at high temperatures particularly in the mid-infrared region.

Dependence of Thermal Conductivity on Size and Specific Surface Area for Different Based CoFe2O4 Cluster Nanofluids

Enhancing the thermal conductivity of fluids by using nanoparticles with outstanding thermophysical properties has acquired significant attention for heat-transfer applications. Nanofluids have the potential to optimize energy systems by improving heat-transfer efficiency. In this study, cobalt ferrite nanoparticles clusters with controlled mean sizes ranging from 97 to 192 nm were synthesized using a solvothermal method to develop novel nanofluids with enhanced thermal conductivity. These clusters were comprehensively characterized using transmission electron microscopy, X-ray diffraction, Raman spectroscopy, vibrating-sample magnetometry, and nitrogen physisorption. The CoFe2O4 cluster nanofluids were prepared using the two-step method with various base fluids (water, propylene glycol, and a mixture of both). Dynamic light scattering analyses of the average Z-size of the dispersed nanoadditives over time revealed that the stability of the dispersions is influenced by cluster size and the proportion of glycol in the base fluid. The thermal conductivity of the base fluid and nine different 0.5 wt% CoFe2O4 cluster nanofluids was measured using the transient hot wire method at temperatures of 293.15, 303.15, and 313.15 K, showing different temperature dependencies. The study also explores the relationships between the thermal conductivity, cluster size, and specific surface area of the nanoadditives. A maximum thermal conductivity enhancement of 4.2% was reported for the 0.5 wt% nanofluid based on propylene glycol containing 97 nm CoFe2O4 clusters. The findings suggest that the specific surface area of nanostructures is a more relevant parameter than size for describing improvements in thermal conductivity.

Temperature-Dependent Kinetics of Plasma-Based CO2Conversion: Interplay of Electron-Driven and Thermal-Driven Chemistry.

The transformation of CO2 into chemical building blocks for various industries is considered a key technology in a net-zero energy future. To realize this, plasma discharges are one of the most promising approaches thanks to their electron-driven reactions and high operational flexibility. Most studies focused on room-temperature and vibrationally-excited discharges, however, lately, the importance of thermal reactions is considered. Therefore, we developed a temperature-dependent plasma-chemical reaction mechanism to investigate the temperature dependence of plasma-based CO2 conversion. Here, we present the various effects of thermally-driven reactions on the CO2 conversion as a function of the gas temperature and specific energy input. Our analysis pinpointed the key reactions controlling the plasma-based CO2 conversion, shifting from an electron-driven to a thermal-driven regime. Additionally, we used the mechanism to verify the theoretical upper boundary of the process' energy efficiency, and discussed how our findings could lead to the further development and optimization of plasma discharges for efficient CO₂ conversion in the future.

Design and Investigation of a High-Performance Quartz-Based SAW Temperature Sensor

In this work, a surface acoustic wave (SAW) temperature sensor based on a quartz substrate was designed and investigated. Employing the Coupling-of-Modes (COM) model, a detailed analysis was conducted on the effects of the number of interdigital transducers (IDTs), the number of reflectors, and their spacing on the performance of the SAW device. The impact of the transversal mode of quartz SAWs on the device was subsequently examined using the finite element method (FEM). The simulation results indicate that optimizing these structural parameters significantly enhances the sensor’s sensitivity and frequency stability. SAW devices with optimal structural parameters were fabricated, and their resonant frequencies were tested across a temperature range of 25–150 °C. Experimental results demonstrate that the SAW temperature sensor maintains high performance stability and data reliability throughout the entire temperature range, achieving a Bode-Q of 7700. Furthermore, the sensor exhibits excellent linearity and repeatability. An analysis of the sensor’s response under varying temperature conditions reveals a significant temperature dependency on its Temperature Coefficient of Frequency (TCF). This feature suggests that the sensor possesses potential advantages for applications in industrial process control and environmental monitoring.

Biocompatible Acellular Dermal Matrix-Based Neuromorphic Device with Ultralow Voltage, Ion Channel Emulation, and Synaptic Forgetting Visualization Computation.

Neuromorphic bioelectronics aim to integrate electronics with biological systems yet encounter challenges in biocompatibility, operating voltages, power consumption, and stability. This study presents biocompatible neuromorphic devices fabricated from acellular dermal matrix (ADM) derived from porcine dermis using low-temperature supercritical CO2 extraction. The ADM preserves the natural scaffold structure of collagen and minimizes immunogenicity by eliminating cells, fats, and noncollagenous impurities, ensuring excellent biocompatibility. The ADM-based devices emulate biological ion channels with biphasic membrane current modulation, exhibiting temperature dependency and pH sensitivity. It operates at an ultralow voltage of 1 mV and demonstrates reliable synaptic modulation exceeding 4 × 104 endurance cycles. The activation voltage can be theoretically as low as 59 μV, comparable to brainwave signals with a power of merely 7 aJ/event. Furthermore, a brain-like forgetting visualization algorithm is developed, leveraging the synaptic forgetting plasticity of ADM-based devices to achieve complex computing tasks in a highly energy-efficient manner. Neuromorphic devices based on ADM not only hold potential in implantable biointerfaces due to their exceptional biocompatibility, ultralow voltage, and power but also provide a feasible way for energy-efficient computing paradigms through a synergistic hardware-software approach.

Development of mathematical models of heat conductivity for modern electronic devices with elements containing foreign inclusions

This paper considers the heat conduction process for an isotropic medium containing a foreign half-through inclusion and heated by a locally concentrated heat flow. Linear and non-linear mathematical models for determining the temperature field have been built to establish the temperature regimes for the effective operation of electronic devices. The coefficient of thermal conductivity of a non-uniform structure is represented as a whole, using asymmetric unit functions, which automatically provides the conditions of ideal thermal contact on the surfaces of materials. This results in solving one heat conduction equation with discontinuous and singular coefficients. A linearizing function was introduced to linearize the nonlinear boundary value problem. Analytical-numerical solutions of linear and nonlinear boundary-value problems have been obtained in a closed form. A linear temperature dependence of the coefficient of thermal conductivity of structural materials was chosen for a heat-sensitive medium. As a result, an analytical-numerical solution was derived, which determines the temperature distribution in this medium. On this basis, a numerical experiment was performed, the results of which are graphically displayed and confirm the adequacy of the constructed mathematical models to a real physical process. The materials of the plate and inclusion are silicon and silver. The results for these materials based on the linear and non-linear model differ by 7 %. Their slight difference is explained by the fact that the values of the temperature coefficient of thermal conductivity are small. The models built make it possible to analyze the given environments in terms of their thermal resistance. As a result, it becomes possible to improve it, and protect structures from overheating, which could lead to the failure of individual nodes and their elements and the entire electronic device

Magnetic Memory Effects in BaFe2(As0.68P0.32)2 Superconducting Single Crystal.

Among many iron-based superconductors, isovalently substituted BaFe2(As1-xPx)2 displays, for x ≈ 0.3, apart from the quite usual Second Magnetization Peak (SMP) in the field dependence of the critical current density, an unusual peak effect in the temperature dependence of the critical current density in the constant field, which is related to the rhombic-to-square (RST) structural transition of the Bragg vortex glass (BVG). By using multi-harmonic AC susceptibility investigations in three different cooling regimes-field cooling, zero-field cooling, and field cooling with measurements during warming up-we have discovered the existence of a temperature region in which there is a pronounced magnetic memory effect, which we attributed to the direction of the structural transition. The observed huge differences in the third harmonic susceptibility at low and high AC frequencies indicates the difference in the time-scale of the structural transition in comparison with the timescale of the vortex excitations. Our findings show that the RST influence on the vortex dynamics goes beyond the previously observed influence on the onset of the SMP.

Dominant role of charge ordering on high harmonic generation in Pr0.6Ca0.4MnO3

High harmonic generation (HHG) is a typical high-order nonlinear optical phenomenon and can be used to probe electronic structures of solids. Here, we investigate the temperature dependence of HHG from Pr0.6Ca0.4MnO3 in the range of 7–294 K, including the charge ordering (CO) transition and magnetic transition temperatures. The high harmonic (HH) intensity remains almost constant in the high-temperature charge-disordered phase. However, as the temperature is lowered, it starts to increase near the CO transition temperature where an optical gap related to the CO appears. The anomalous gap energy dependence resembles the one recently reported in a Mott insulator. We attribute the suppression of the HH intensity at high temperatures to the destructive interference among HH emissions from thermally activated multiple charge configurations. Our results suggest that HHG is a promising tool for probing the fluctuation of local order in strongly correlated systems. Published by the American Physical Society 2024

Global Temperature Dependency of Biogenic HCHO Columns Observed From Space: Interpretation of TROPOMI Results Using GEOS‐Chem Model

AbstractTemperature is the principal driver of global atmospheric formaldehyde (HCHO) and its primary oxidation precursor biogenic volatile organic compounds (BVOCs). We revisit such a temperature (T‐) dependency globally, leveraging TROPOMI HCHO column data. We find substantial variations in the T‐dependency of biogenic HCHO across plant functional types (PFTs), with the highest over Broadleaf Evergreen Tropical Trees (doubling every 6.0 K ± 4.1 K) and lowest over Arctic C3 Grass (doubling every 30.8 K ± 9.6 K). The GEOS‐Chem model interprets HCHO columns' T‐dependency at the PFT level (r = 0.87), with a 16% discrepancy on average. The discrepancy can be explained by BVOC emissions T‐dependency for Broadleaf Evergreen Tropical Trees and Warm C4 Grass and can be attributed to the insensitivity of HCHO columns to BVOC emissions for other PFTs. Our findings underscore a potentially magnified variation of BVOC emissions by GEOS‐Chem and MEGAN therein, particularly in regions experiencing greater temperature variations.

Hydrodynamization and resummed viscous hydrodynamics

In this paper, I review our current understanding of the applicability of hydrodynamics to modeling the quark–gluon plasma (QGP), focusing on the question of hydrodynamization/thermalization of the QGP and the anisotropic hydrodynamics (aHydro) far-from-equilibrium hydrodynamic framework. I discuss the existence of far-from-equilibrium hydrodynamic attractors and methods for determining attractors within different hydrodynamical frameworks. I also discuss the determination of attractors from exact solutions to the Boltzmann equation in relaxation time approximation and effective kinetic field theory applied to quantum chromodynamics. I then present comparisons of the kinetic attractors with the attractors obtained in standard second-viscous hydrodynamics frameworks and aHydro. I demonstrate that, due to the resummation of terms to all orders in the inverse Reynolds number, the aHydro framework can describe both the weak- and strong-interaction limits. I then review the phenomenological application of aHydro to relativistic heavy-ion collisions using both quasiparticle aHydro and second-order viscous aHydro. The phenomenological results indicate that aHydro provides a controlled extension of dissipative relativistic hydrodynamics to the early-time far-from-equilibrium stage of heavy-ion collisions. This allows one to better describe the data and to extract the temperature dependence of transport coefficients at much higher temperatures than linearized second-order viscous hydrodynamics.

The effect of gamma irradiation on the dielectric properties of polyethylene-based composites with the CdS/ZnS binary system

Polyethylene-based composites with the CdS/ZnS binary system were obtained with a component ratio of 10% CdS/ZnS; 30% CdS/ZnS; 50% CdS/ZnS. The temperature dependences of the dielectric constant (ε) and the tangent of the dielectric loss angle (tgδ) of samples of HDPE+CdS/ZnS composites irradiated with a dose of 100 kGy, 50 kGy, and 200 kGy were shown. The dependences of the dielectric constant and the tangent of the dielectric loss angle of HDPE+Cds/ZnS composites on the gamma-irradiation dose have been determined.

Evidence for nematic fluctuations in FeSe superconductor: a 57Fe Mössbauer spectroscopy study

There has been controversy about the driving force of the nematic order in the FeSe superconductor. Here, we present a detailed study of the57Fe Mössbauer spectra of FeSe single-crystal powders, focusing on the temperature dependences of the hyperfine parameters in the vicinity of the nematic transition temperature,Ts∼ 90 K. The nematicity-induced splitting ofdxzanddyzbands, obtained from the anomalous increase in quadrupole splitting nearTs, starts at 143 K. The temperature evolution of the lattice dynamics, deduced from the recoilless fractions and second-order Doppler shifts, is found to undergo successively two segments of phonon-softening (160 K-105 K) and phonon-hardening (105 K-90 K), related to the appearance of local orthorhombic distortions aboveTsand the establishing way of the associated nematic correlations. Analysis of the linewidths shows that spin fluctuations occur not only below 70 K but also acrossTs(105 K-70 K), accompanied by the non-Fermi liquid behavior of the electrons. The results demonstrate the strong interactions between lattice, spin, and electron degrees of freedom in the vicinity ofTsand that the lattice degrees of freedom may play an essential role in driving the nematic order for FeSe.

Profiles of peripheral regulatory T cells forecasts the feasibility of steroid withdrawal after liver transplantation based on cellular thermal modeling

After liver transplantation, steroid therapy is often used to prevent rejection. However, long-term steroid use can lead to serious side effects, therefore, this study aimed to evaluate the feasibility of peripheral regulatory T cell profiles for steroid discontinuation after liver transplantation through cellular thermal modeling and real-time monitoring of intracellular thermodynamics. In this study, cellular thermal modeling techniques were used to simulate the thermodynamic characteristics of peripheral TREgs under different conditions. The dynamic changes of peripheral Treg in liver transplantation animal models were monitored by flow cytometry and molecular biology. Significant changes in peripheral Treg profiles were observed after initiation of steroid therapy, especially in the discontinuation group, and these changes were strongly associated with the restoration of immune homeostasis. Real-time monitoring of the thermodynamic data revealed that peripheral Treg activity showed a specific temperature dependence in the cellular thermal model. Cell thermal modeling combined with real-time monitoring of intracellular thermodynamics provides a new perspective for evaluating the feasibility of peripheral regulatory T cell profiles for steroid discontinuation after liver transplantation. Strengthening the dynamic monitoring of peripheral Treg spectrum provides an important basis for the formulation of personalized immunosuppression strategies, and improves the therapeutic effect and quality of life of liver transplant patients.

Nighttime chemistry of furanoids and terpenes: Temperature dependent kinetics with NO3 radicals and insights into the reaction mechanism

In this study, the gas phase reaction of NO3 radical with three furanoids, furan (F), 2-methylfuran (2-MF) and 2,5-dimethylfuran (2,5-DMF) were investigated using a relative rate method in a temperature regulated atmospheric simulation chamber (THALAMOS). As part of this study, the temperature dependence of two monoterpenes, α-pinene (α-P) and 2-carene (2-C), that were used as reference molecules, is also reported. The kinetic measurements were performed in the range of 263–373 K, atmospheric pressure using zero air as bath gas. The reaction was followed using Selected ion flow tube mass spectrometry (SIFT-MS) to monitor in real time the mixing ratios of the investigated species. The corresponding Arrhenius expressions obtained were:kα−P+NO3(263−378K)=(1.32±0.16)×10−12×e462±70Tcm3molecule‐1s‐1.k2−C+NO3296–433K=8.77±2.71×10−13×e904±96Tcm3molecule‐1s‐1.kF+NO3263−353K=7.55±1.96×10−13×e254±79Tcm3molecule‐1s‐1.k2−MF+NO3263−373K=7.76±2.62×10−13×e922±262Tcm3molecule‐1s‐1.k2,5−DMF+NO3298–353K=2.58±0.77×10−13×e1692±136Tcm3molecule‐1s‐1.Where the estimated uncertainties include the 1σ precision of the fit and the estimated uncertainty in the precision of the Arhenius fit of the reference compound. In the case of furanoids, the negative temperature-dependence of the rate coefficients shows that the reaction mechanism is complex, indicating that the reaction involves the formation of an adduct that could lead either to NO3 addition to the double bond, as well as, in the case of 2-MF and 2,5-DMF, the H-abstraction from the methyl group attached to the ring. In addition to the kinetics measurements, the major products formed from the reaction of furan and 2,5-DMF with NO3 were studied. The two identified products from the reaction of furan with NO3, were 3H-furan-2-one (C4H4O2) and 2-butenedial (C4H4O2), formed by NO3 addition to the double bond of the furan ring. 3-Hexene-2,5-dione (C6H8O2) and 5-methylfurfural (C6H6O2) are the two major products of 2,5-DMF reaction with NO3, linked to the addition and abstraction pathways, respectively. Considering that 5-methylfurfural is the only primary product of the H elimination pathway of 2,5-DMF, the determination of its formation yields as a function of temperature, allowed us to extract the temperature dependence of the rate coefficients of the abstraction and addition pathways.Overall, the NO3 oxidation of the studied furanoids, is expected to be the dominant tropospheric loss process, in the studied temperature range.

Respective Roles of Electron-Phonon and Electron-Electron Interactions in the Transport and Quasiparticle Properties of SrVO_{3}.

The spectral and transport properties of strongly correlated metals, such as SrVO_{3} (SVO), are widely attributed to electron-electron (e-e) interactions, with lattice vibrations (phonons) playing a secondary role. Here, using first-principles electron-phonon (e-ph) and dynamical mean field theory calculations, we show that e-ph interactions play an essential role in SVO: they govern the electron scattering and resistivity in a wide temperature range down to 30K, and induce an experimentally observed kink in the spectral function. In contrast, the e-e interactions control quasiparticle renormalization and low temperature transport, and enhance the e-ph coupling. We clarify the origin of the near T^{2} temperature dependence of the resistivity by analyzing the e-e and e-ph limited transport regimes. Our work disentangles the electronic and lattice degrees of freedom in a prototypical correlated metal, revealing the dominant role of e-ph interactions in SVO.

A synchronous improvement of strength and elongation caused by solid solution in low-silver SAC solder with superior necking resistance properties

The current SAC(Sn–Ag–Cu) solder often experiences rapid degradation of mechanical properties at high temperatures and is prone to fracture under dynamic loads, thus failing to meet the interconnection requirements of industrial electronic products that operate under high power and vibration loads. In light of this, this paper aims to enhance the overall performance of the alloy by reducing the fraction of the second phase in SAC305 alloy, altering the type of second-phase particles, and strengthening the matrix β-Sn phase. Additionally, based on thermodynamic calculations of phase diagrams, the internal phases and elemental solid solubility of the alloy under different temperature conditions are accurately designed, thereby improving the alloy's strength while maintaining its elongation almost unchanged. The experimental results indicate that the designed Sn1.0Ag0.7Cu–3Bi4In1.5Sb alloy exhibits a higher rate sensitivity factor m (0.0559), which is more than double that of the Sn1.0Ag0.7Cu–5Bi4In3Sb alloy (0.0239). This improvement is primarily attributed to the enhanced interaction between the matrix β-Sn and the solid solution effect. Larger compound phases, such as Cu6Sn5 and Ag3Sn, only play a role in the low-rate loading region. Additionally, the alloy demonstrates strong temperature dependence, which is also related to the dissolution of the In element in the matrix β-Sn. The solid solution of the In element significantly enhances the high-temperature elongation rate of the alloy, increasing from 11.9% at low temperatures to 21.3% at high temperatures. The successful development and implementation of this research provides a new solution for interconnection of electronic devices under high-speed dynamic loading and high-temperature service.

Effect of restricted geometry on phase transitions in nanostructured sodium nitrate

The study of structure of nanocomposite material based on porous glass with 7 nm average pore diameter filled by sodium nitrate from the melt under pressure has been carried out by synchrotron radiation diffraction upon heating and cooling. The temperature evolution of the elastic peak lineshapes corresponding to the sodium nitrate structure has been analyzed, and it is shown, that in the “virgin” sample there are two types of nanoparticles with dendrite spatial organization and with fundamentally different characteristic sizes. The temperature dependences of the critical index β(T) for the structural transition in sodium nitrate have been obtained, and the crossover in this dependence for nanoparticles with a characteristic size of about 20 nm has been found at T∗ ∼ 445 K both upon heating and cooling. The temperatures of the structure and “melting – crystallization” phase transitions observed in this nanocomposite have been determined.

Temperature Dependence of Hydrotropy.

The solubility of hydrophobic solutes increases dramatically with the temperature when hydrotropes are added to water. In this paper, the mechanism of this well-known observation will be explained via statistical thermodynamics through (i) enhanced enthalpy-hydrotrope number correlation locally (around the solute) that promotes the temperature dependence and (ii) hydrotrope self-association in the bulk solution that suppresses the temperature dependence. The contribution from (i), demonstrated to be dominant for urea as a hydrotrope, signifies the weakening of interaction energies around the solute (local) than in the bulk that accompanies incoming hydrotrope molecules. Thus, studying hydrotropic solubilization along the temperature and hydrotrope concentration provides complementary information on the local-bulk difference: the local accumulation of hydrotropes around the solute, driven by the enhanced local hydrotrope self-association, is also accompanied by the overall local weakening of energetic interactions, reflecting the fluctuational nature of hydrotrope association and the mediating role of water molecules.