Search Results (110)

To improve solid-state lithium batteries, solution casting has been employed to create lithium ion-conducting copolymer electrolytes involving poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)/polyvinylpyrrolidone (PVP) blend polymers with various compositions. Following X-ray diffraction and Fourier transformation (FTIR), the structural characterisation and identification of molecular bonding in polymer electrolytes were confirmed. Through AC impedance analysis, the electrical characteristics of the solid-state polymer films were investigated. The dielectric conductivity of the sample was found to obey the modified Arrhenius relationship, while in the case of a sample with higher conductivity, it followed Arrhenius behaviour. The relaxation parameters and dielectric behaviour of the samples are demonstrated and discussed. Full article

The dielectric relaxation dynamics in polymer composites critically determine their functional performance in advanced electrical systems. This study systematically investigates hybrid epoxy composites comprising neat epoxy resin (EP) and paper-reinforced systems (EIP), modified with 10–50 wt% polypropylene glycol diglycidyl ether (PEGDGE) plasticizer. Through synergistic application of differential scanning calorimetry (DSC) and broadband dielectric spectroscopy (10⁻¹–10⁶ Hz), the quantitative relationships between plasticizer content, glass transition temperature (Tg), and dielectric relaxation processes were established. DSC analysis reveals a linear Tg dependence with increasing PEGDGE content, attributed to enhanced molecular mobility. Dielectric characterization demonstrates three distinct relaxation regimes: α-relaxation below Tg, interfacial polarization at epoxy/PEGDGE boundaries, and paper/epoxy interfacial effects in EIP systems. A quantitative dielectric relaxation model was developed based on complex modulus formalism, coupled with Vogel–Fulcher–Tammann (VFT) analysis of DC conductivity. Activation energy mapping through Arrhenius decomposition reveals three characteristic values: (1) 82.01–87.80 kJ/mol for α-relaxation, (2) 55.96–64.64 kJ/mol for epoxy/PEGDGE interfaces, and (3) 30.88–44.38 kJ/mol for epoxy/paper interfaces. Crucially, the plasticizer content modulates these activation energies, demonstrating its role in tailoring interfacial dynamics. Full article

The effect of thermo-oxidative aging on the hyperelastic behavior of ethylene propylene diene monomer (EPDM) rubber was investigated by a combined experimental and theoretical modeling approach. Firstly, the uniaxial tensile test of aged and unaged EPDM rubber was carried out. The test results show that the unaged EPDM rubber had the nonlinear large deformation characteristic of a “S” shape. The stiffness of the EPDM rubber was found to increase with the aging time and aging temperature. Then, in order to quantitatively characterize the hyperelastic behavior of unaged EPDM rubber, the fitting performances of the Mooney–Rivlin, Arruda–Boyce, and Ogden models were compared based on a uniaxial tensile stress–strain curve. The results show that the Ogden model provided a more accurate representation of the hyperelastic behavior of unaged EPDM rubber. Subsequently, the Dakin dynamic equation was adopted to associate the parameters of the Ogden model with the aging time, and the Arrhenius relationship was utilized to introduce the aging temperature into the rate term of the Dakin dynamic equation, thereby establishing an improved Ogden constitutive model. This improved model expanded the Ogden model’s ability to explain aging time and aging temperature. Finally, the improved model prediction results and the test results were compared, and they indicate that the proposed improved Ogden constitutive model can accurately describe the hyperelastic behavior of aged and unaged EPDM rubber. Full article

The motivation of this research was to analyze the dynamic properties, mainly the loss modulus, of vulcanized immiscible blends of natural rubber (NR) and styrene-butadiene rubber (SBR) in the glass transition zone, where the SBR phase is in a glassy state and the NR phase is in a rubbery state. The blends were cured at 433 and 443 K and studied around the glass transition using a dynamic mechanical analyzer. The dependence of the loss modulus on temperature was described by considering the phase separation, and the frequency dependence was also included to provide a deeper insight into the dynamic properties. This was achieved by integrating the mechanical model proposed by Zener, which considers a single relaxation time related to temperature using both the Arrhenius and Vogel–Fulcher–Tammann (VFT) relations. The best correlation with the data was obtained using the Arrhenius relationship. The activation energy of the NR phase increases with the NR content in the blend, while in the SBR phase, it varies slightly. The trends obtained are related to curative migration from the SBR to the NR phase, increasing the crosslink density at NR domain boundaries. These insights are valuable for optimizing the performance of these elastomeric blends in practical applications. Full article

Two-dimensional (2D) materials are regarded as key foundational materials for next-generation optoelectronic devices. As a promising new type of 2D layered semiconductor, Bi₂O₂Se has emerged as a strong candidate for high-performance opto-electronic devices due to its high carrier mobility, tunable bandgap, and excellent environmental stability. However, achieving precise control over Bi₂O₂Se growth to obtain high-quality Bi₂O₂Se remains a challenge in the field. In this study, we employed chemical vapor deposition (CVD) to grow thin-layer 2D Bi₂O₂Se flakes. We further used a transport model and thermodynamic Arrhenius fitting to analyze the relationship between vapor flux and the properties of the flakes. Density functional theory was used to study the electronic structure of the as-grown samples. The electrical and optoelectronic results demonstrate that Bi₂O₂Se-based FETs exhibit good performance in terms of mobility (129 cm²V⁻¹s⁻¹), on/off ratio (4.51 × 10⁵), and photoresponsivity (94.98 AW⁻¹). This work provides a new way to study the influence of vapor flux on the sizes and shapes of Bi₂O₂Se flakes for photodetectors. Full article

Magnesium sulfate leaching of ionic rare earth ores is generally characterized by a smooth outflow curve, a long leaching time, and a high impurity content in the leach liquor. To reveal the leaching law of rare earth cations and impurity aluminum ions in the leaching process of ionic rare earth ores in magnesium sulfate, equilibrium leaching and leaching kinetics experiments were carried out using ore samples of five particle sizes (<0.10, 0.10–0.25, 0.25–0.50, 0.50–1.00, and >1.00 mm). Furthermore, prediction models of equilibrium constants and rate constants were constructed based on ion-exchange theory. The results show that the equilibrium constants of the rare earth and aluminum ion-exchange reactions decrease gradually with the increase in the magnesium ion concentration, the decrease in the temperature, and the increase in the surface area of the particles. Moreover, the equilibrium constant prediction models of rare earth and aluminum with magnesium sulfate were constructed using data fitting. From the leaching kinetics experiment, there is a significant relationship between the reaction rate constant of ion exchange and the surface area of the particles: the larger the particle size, the smaller the reaction rate constant. Based on the kinetic test data and the Arrhenius equation, the frequency factors and activation energies of the ion-exchange reactions were inversely analyzed through the Chemistry Reaction Module of COMSOL. The reaction activation energy for rare earth and aluminum leaching is 10,743 J/mol and 10,987 J/mol, respectively. The rate constant prediction model was obtained by fitting the analyzed rate constant data. The rare earth and aluminum leaching results for the full-grade ores are in high agreement with the predictions of the constructed model, which verifies the validity of the proposed model. This study can provide theoretical support for the improvement of the leaching efficiency of rare earths and the optimization of the magnesium sulfate leaching process. Full article

This study investigates the hydrothermal liquefaction (HTL) aqueous phase (AP) of Shorea sawdust in a semi-flow batch reactor, focusing on the reaction network and computational fluid dynamics (CFD) simulation. High-performance liquid chromatography (HPLC) was used to detect lignocellulosic decomposition compounds, revealing the presence of glucose, galactose, xylose, furfural, ethanol, and other undefined compounds due to lignocellulosic decomposition. Reaction ordinate (R₀) indicates that the reaction progresses steadily as time increases, and higher temperature leads to a greater reaction ordinate, agreeing with Arrhenius’ assumption that gained energy enables molecules to overcome the activation energy barrier. However, saccharide C6 and C5 yield at 220 °C fluctuates as the reaction increases, suggesting secondary reactions. A kinetic model was built based on a reaction network, which was developed based on HPLC results. Arrhenius parameters revealed that reaction yield is influenced by temperature and time, whereas galactose, xylose, and ethanol production are time dependent. In contrast, glucose formation is influenced by both time and temperature. The prediction of saccharide yields by the model confirmed that 220 °C is the optimal temperature for glucose and ethanol production, balancing slow reactions and rapid degradation. CFD simulations show a uniform pressure distribution inside the reaction chamber with high localised pressure at the input (1570 Pa). In addition, feedstock particles tend to distribute along the chamber wall because of the laminar flow, which is consistent with the observation of the experiment. The findings highlight the intricate relationship between reaction conditions and the composition of the HTL product, contributing to a more comprehensive understanding of the process. Full article

In this paper, constant strain rate compression was carried out by means of an MMS-100 thermal/force simulation tester in a temperature range of 790~940 °C, with a strain rate of 0.01–1 s⁻¹ and a compression volume of 60%. A linear regression method was used to fit the relationship between strain stress, strain rate, and deformation temperature, and the Arrhenius-type constitutive equation of Ti55531 titanium alloy was established; the heat deformation activation energy of Ti55531 titanium alloy was obtained as 211,747.5 kJ·mol⁻¹. A thermal processing map of Ti55531 alloy was established. EBSD results show that after hot compression, the recrystallization volume fraction greatly increased. The original sample recrystallization volume fraction was 23.2%. Under a deformation temperature of 850 degrees Celsius and deformation rate of 0.01, the recrystallization volume fraction rose to 38.5%; after the annealing process, the recrystallization volume fraction further increased to 72.6%. Under the deformation temperature of the thermal compression process, the higher the deformation rate, the larger its recrystallization volume fraction. After annealing, the recrystallization volume fraction further increased. This study can provide a reference and theoretical guidance for the development and optimization of the thermal processing process of Ti55531 titanium alloy. Full article

MoO₂ powders compacted under different uniaxial pressures ranging from 100 to 800 MPa, corresponding to the compact densities ranging from 55% to 65%, respectively, were sintered at targeted temperatures within 650–1050 °C for 1 h in an N₂ atmosphere. Then, their densification kinetics and grain growth were investigated. With regard to the densification of MoO₂ powders at room temperature, a linear relationship was observed between the compact density and log pressure in the uniaxial pressure range without fracture and local deformation. The relative densities of the sintered MoO₂ samples increased with increasing compact density and sintering temperature. At a given sintering temperature, the sample with the highest compact density exhibited the best densification rate. The grain size in the sintered samples was proportional to the relative density, and the grain growth obeyed the Arrhenius equation. The sintered samples with 55%, 60%, and 65% densities during the sintering process have different activation energies values depending on the sintering temperature. At low sintering temperatures, the activation energies for 55%, 60%, and 65% compact densities were 50.8, 39.6, and 26.1 kJ/mol, respectively, and at higher sintering temperatures, the corresponding values were 19.8, 21.5, and 25.4 kJ/mol. Full article

In response to the increasingly strict performance requirements of large molds, a novel Cr-Mo-V hot-work die steel has been developed. In order to study the high-temperature hot deformation behavior and plasticity of the novel steel, hot compression tests were conducted on the Gleeble-1500D thermal simulation testing machine at a deformation temperature of 950~1200 °C and a strain rate of 0.001~5 s⁻¹. Based on the Arrhenius constitutive model, a novel Cr-Mo-V steel high-temperature constitutive model considering strain was established. The reliability and applicability of this modified model, which includes strain compensation, were assessed using the phase relationship coefficient (R) and the average absolute relative error (AARE). The values of R and AARE for comparing predicted outcomes with experimental data were 0.98902 and 3.21%, respectively, indicating that the model demonstrated high precision and reliability. Based on the Prasad criterion, a 3D hot processing map of the novel Cr-Mo-V steel was established, and the instability zone of the material was determined through the hot processing map: the deformation temperature (950~1050 °C) and strain rate (0.001~0.01 s⁻¹) were prone to adiabatic shear and crystal mixing. The suitable processing range was determined based on the hot processing map: The first suitable processing area was the strain range of 0.05~0.35, the temperature range was 1100~1175 °C, and the strain rate was 0.001~0.009 s⁻¹. The second suitable processing area was a strain of 0.45~0.65, a temperature of 1100~1200 °C, and a strain rate of 0.0024~0.33 s⁻¹. Finally, the forging process of hundred-ton die steel forging was developed by combining 3D hot processing maps with finite element simulation, and the forging trial production of 183 t forging was carried out. The good forging quality indicated that the established hot processing map had a good guiding effect on the production of 100-ton test steel forging. Full article

This article presents a novel aging-coupled predictive thermo-electrical dynamic modeling tool tailored for primary lithium manganese dioxide ($Li\text{-}Mn{O}_2$) batteries in active implantable medical devices (AIMDs). The aging mechanisms of rechargeable lithium batteries are well documented using computationally intensive physics-based models, unsuitable for real-time onboard monitoring in AIMDs due to their high demands. There is a critical need for efficient, less demanding modeling tools for accurate battery health monitoring and end-of-life prediction as well as battery safety assessment in these devices. The presented model in this article simulates the battery terminal voltage, remaining capacity, temperature, and aging during active discharge, making it suitable for real-time health monitoring and end-of-life prediction. We incorporate a first-order dynamic for internal resistance growth, influenced by time, temperature, discharge depth, and load current. By adopting Arrhenius-type kinetics and polynomial relationships, this model effectively simulates the combined impact of these variables on battery aging under diverse operational conditions. The simulation handles both the continuous micro-ampere-level demands necessary for device housekeeping and periodic high-rate pulses needed for therapeutic functions, at a constant ambient temperature of 37 °C, mimicking human body conditions. Our findings reveal a gradual, nonlinear increase in internal resistance as the battery ages, rising by an order of magnitude over a period of 5 years. Sensitivity analysis shows that as the battery ages and load current increases, the terminal voltage becomes increasingly sensitive to internal resistance. Specifically, at defibrillation events, the ${\displaystyle \frac{\partial V}{\partial R}}$ trajectory dramatically increases from ${10}^{-12}$ to ${10}^{-8}$, indicating a fourth-order-of-magnitude enhancement in sensitivity. A model verification against experimental data shows an R² value of 0.9506, indicating a high level of accuracy in predicting the $Li\text{-}Mn{O}_2$ cell terminal voltage. This modeling tool offers a comprehensive framework for effectively monitoring and optimizing battery life in AIMDs, therefore enhancing patient safety. Full article

In this study, we investigated the density of states extraction method for atomic-deposited ZnO thin-film transistors (TFTs) by analyzing gate-dependent field-effect mobility. The atomic layer deposition (ALD) method offers ultra-thin and smooth ZnO films, but these films suffer from interface and semiconductor defects, which lead to disordered localized electronic structures. Hence, to investigate the unstable localized structure of ZnO TFTs, we tried to derive the electronic state relationship by assuming field-effect mobility can be expressed as a gate-dependent Arrhenius relation, and the activation energy in the relation is the required energy for hopping. Following this derived relationship, the DOS of the atomic-deposited ZnO transistor was extracted and found to be consistent with those using temperature-dependent measurements. Moreover, to ensure the proposed method is reliable, we applied methods for the extraction of DOSs of doped ZnO transistors, which show enhanced mobilities with shifted threshold voltages, and the results show that the extraction method is reliable. Thus, we can state that the mobility-based DOS extraction method offers practical benefits for estimating the density of states of disordered transistors using a single transfer characteristic of these devices. Full article

Minimum ignition energy (MIE) has been extensively studied via experiments and simulations. However, our literature review reveals little quantitative consistency, with results varying from 0.324 to 1.349 mJ for ϕ = 1.0 and from 0.22 to 0.944 mJ for ϕ = 0.9. Therefore, there is a need to resolve these discrepancies. This RANS study aims to partially address this knowledge gap. Additionally, it presents other flame evolution parameters essential for robust combustion design. Using the reactingFOAM solver, we predict the threshold energy required to ignite the fuel mixture. For this, the single step using the Arrhenius law is selected to model ignition in the flame kernel of stochiometric and lean CH₄/air mixtures, allowing it to develop into a self-sustained flame. The ignition power density, an energy quantity normalised with volume, is incrementally varied, keeping the kernel critical radius r_s constant at 0.5 mm in the quiescent mixture of two equivalence ratios ϕ 0.9 and 1.0, for varied operating pressures of 1, 5, and 10 bar at the constant initial temperature of 300 K. The minimum ignition energy is validated with twelve independent 1-bar datasets both numerically and experimentally. The effect of pressure on MIEs, which diminish as pressure rises, is significant. At ϕ = 1.0 (and 0.9), the flame temperature reached 481.24 K (457.803 K) at 1 bar, 443.176 K (427.356 K) at 5 bar, and 385.56 K (382.688 K) at 10 bar. The minimum ignition energy was validated using twelve independent 1-bar datasets from both numerical simulations and experiments. The results show strong agreement with many experimental findings. Finally, a mathematical formulation of MIE is devised; a function of pressure and equivalence ratio shows a slightly curved relationship. Full article

Ethylene-propylene-diene monomer (EPDM) is a key engineering material; its mechanical characterization is important for the safe use of the material. In this paper, the coupled effects of thermal degradation temperature and time on the tensile mechanical behavior of EPDM rubber were investigated. The tensile stress-strain curves of the aged and unaged EPDM rubber show strong nonlinearity, demonstrating especially rapid stiffening as the strain increases under small deformation. The popular Mooney–Rivlin and Ogden (N = 3) models were chosen to fit the test data, and the results indicate that neither of the classical models can accurately describe the tensile mechanical behavior of this rubber. Six hyperelastic constitutive models, which are excellent for rubber with highly nonlinearity, were employed, and their abilities to reproduce the stress-strain curve of the unaged EPDM were assessed. Finally, the Davis–De–Thomas model was found to be an appropriate hyperelastic model for EPDM rubber. A Dakin-type kinetic relationship was employed to describe the relationships between the model parameters and aging temperature and time, and, combined with the Arrhenius law, a thermal aging constitutive model for EPDM rubber was established. The ability of the proposed model was checked by independent testing data. In the moderate strain range of 200%, the errors remained below 10%. The maximum errors of the prediction results at 85 °C for 4 days and 100 °C for 2 and 4 days were computed to be 17.06%, 17.51% and 19.77%, respectively. This work develops a theoretical approach to predicting the mechanical behavior of rubber material that has suffered thermal aging; this approach is helpful in determining the safe long-term use of the material. Full article

The present experimental study assesses the mechanical properties of glass/carbon/glass hybrid composite laminates after being exposed to moisture in a deep freezer and elevated temperatures for extended periods. The top and bottom layers of the hybrid laminates are reinforced with glass fibre, and the middle layer is reinforced with carbon fibre using the epoxy matrix as a binder polymer material. The hybrid laminates were manufactured using the resin transfer moulding method, and their compressive and tensile properties were determined using a tensile testing machine. The storage modulus, loss modulus, and damping factors of all groups of laminates were identified using a dynamic mechanical analysis as a function of temperature and vibration frequency. The experimental results on compressive and tensile properties revealed slight variations when the hybrid laminates were kept at low temperatures in a deep freezer for extended periods. This might occur due to the increasing molecular crosslinking of the polymer network. As the testing temperature increased, compressive, tensile, storage modules, loss modulus, and damping factors decreased. This might occur due to the increasing mobility of the binder material. Particularly, the highest stiffness parameters were obtained at −80 °C/GCG (glass/carbon/glass) laminates due to the presence of a beta transition in the glassy region. The relationships between the glass transitions and the targeted frequencies were characterized. The values of the glass transition shift towards higher temperatures as the frequency increases. This might occur due to a reduction in the gaps between the crosslinking of the epoxy network when the frequency increases. The accuracy of the storage modulus results was compared with the empirical models. The model based on the Arrhenius law provided the closest correlation. Meanwhile, another model was observed that was not accurate enough to predict when gamma and beta relaxations occur in a glassy state. Full article