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The primary objective of this article is on examining the impacts of mixed convection flow of Carreau fluid past a permeable stretched surface with Soret and Dufour effects occurring. For the flow analysis, the Darcy–Forchheimer porosity medium is taken into account. In order to explore the transference analysis of heat and mass rate, the impressions of thermal radiation, viscous dissipation, heat generation, Arrhenius activation energy, convective heat, and mass conditions impacts are taken into consideration. The flow equations initially exist as PDEs, and we then employ appropriate similarity transformations to change them into ODEs. The R–K 4th order strategy based on the shooting approach is used to numerically solve these ODEs. Through various emergent variables, the numerical results for the velocity, temperature, and concentration fields are shown. For a variety of distinct variables, the physical quantities such as friction factor, local Nusselt number, and local Sherwood numbers are shown. It is noted that the velocity field is reduced by the magnetic field, but the Weissenberg number buoyancy ratio parameter exhibits the opposite tendency. Further, it is noticed that temperature and concentration distributions have an improving tendency for the Soret and Dufour parameter.

Heterogeneous bubble nucleation is one of the most fundamental interfacial processes that has received broad interest from diverse fields of physics and chemistry. While most studies focused on large microbubbles, here we employed a surface plasmon resonance microscopy to measure the nucleation rate constant and activation energy barrier of single nanosized embryo vapor bubbles upon heating a flat gold film with a focused laser beam. Image analysis allowed for simultaneously determining the local temperature and local nucleation rate constant from the same batch of optical images. By analyzing the dependence of nucleation rate constant on temperature, we were able to calculate the local activation energy barrier within a submicrometer spot. Scanning the substrate further led to a nucleation rate map with a spatial resolution of 100 nm, which revealed no correlation with the local roughness. These results indicate that facet structure and surface chemistry, rather than geometrical roughness, regulated the activation energy barrier for heterogeneous nucleation of embryo nanobubbles.

Ammonia serves as a crucial chemical raw material and hydrogen energy carrier. Aqueous electrocatalytic nitrogen reduction reaction (NRR), powered by renewable energy, has attracted tremendous interest during the past few years. Although some achievements have been revealed in aqueous NRR, significant challenges have also been identified. The activity and selectivity are fundamentally limited by nitrogen activation and competitive hydrogen evolution. This review focuses on the hurdles of nitrogen activation and delves into complementary strategies, including materials design and system optimization (reactor, electrolyte, and mediator). Then, it introduces advanced interdisciplinary technologies that have recently emerged for nitrogen activation using high‐energy physics such as plasma and triboelectrification. With a better understanding of the corresponding reaction mechanisms in the coming years, these technologies have the potential to be extended in further applications. This review provides further insight into the reaction mechanisms of selectivity and stability of different reaction systems. We then recommend a rigorous and detailed protocol for investigating NRR performance and also highlight several potential research directions in this exciting field, coupling with advanced interdisciplinary applications, in situ/operando characterizations, and theoretical calculations. Considering the urgent demand for nitrogen activation in aqueous electrocatalytic nitrogen reduction reactions, we outline the challenges associated with nitrogen activation and delve into complementary strategies, including materials design and system optimization (reactor, electrolyte, and mediator). By evaluating various promising research directions coupled with advanced interdisciplinary applications, this review aims to provide valuable insights for developing potential nitrogen fixation systems in the future.

Poly(lactic acid) (PLA) is one of the most important bio-based and industrial compostable materials in food packaging. Its barrier properties towards oxygen and moisture are well documented. However, data on barrier properties of PLA towards organic molecules are scarce in the literature. This study investigated the diffusion of various organic molecules, including n-alkanes, 1-alcohols, 2-ketones, ethers, esters, amines, and aromatics, in two commercial PLA films with thicknesses of 20 µm and 30 µm. The diffusion coefficient (DP) values were determined from lag time in permeation tests conducted at temperatures ranging from 20 °C to 90 °C. The films were also characterized in terms of crystallinity, rigid and mobile amorphous fractions, and molecular weight. Activation energies (EA) were calculated based on the temperature dependence of the DP using the Arrhenius approach. In total, 290 DP values for 55 individual substances were determined, and 38 EA values were derived from these data. The EA correlated well with the molecular volume of the investigated substances. Moreover, the pre-exponential factor D0 showed a correlation with EA. These correlations enabled the establishment of diffusion modeling parameters for PLA, allowing the prediction of DP for untested substances. The diffusion behavior of PLA was further compared with the literature data for polyethylene terephthalate and polyethylene naphthalate, providing insights into the relative performance of these materials.

The present article investigates Darcy–Forchheimer 3D nanoliquid flow because of a rotating disk with Arrhenius activation energy. Flow is created by rotating disk. Impacts of thermophoresis and Brownian dispersion are accounted for. Convective states of thermal and mass transport at surface of a rotating disk are imposed. The nonlinear systems have been deduced by transformation technique. Shooting method is employed to construct the numerical arrangement of subsequent problem. Plots are organized just to investigate how velocities, concentration, and temperature are influenced by distinct emerging flow variables. Surface drag coefficients and local Sherwood and Nusselt numbers are also plotted and discussed. Our results indicate that the temperature and concentration are enhanced for larger values of porosity parameter and Forchheimer number.

This paper presents physical-aging data for the silicone oil tetramethyl-tetraphenyl trisiloxane. The density and the highfrequency plateau shear modulus G∞ were monitored following temperature jumps starting from fully equilibrated conditions. Both quantities exhibit a fast change immediately after a temperature jump. Adopting the material-time formalism of Narayanaswamy, we determine from the dielectric loss at 0.178 Hz the time evolution of the aging-rate activation energy. The relative magnitude of the fast change of the activation energy differs from that of the density, but is identical to that of G∞. In fact, the activation energy is proportional to G∞ throughout the aging process, with minor deviations at the shortest times. This shows that for the silicone oil in question the dynamics are determined by G∞ in—as well as out of—equilibrium.

Coal is a crucial energy source globally, but it poses environmental challenges due to high temperatures and harmful missions during combustion. This study investigates bituminous coal's oxidation combustion in low-oxygen environments using thermogravimetry and differential thermogravimetry tests. We explore the thermal behavior and kinetic properties of three coal samples during combustion. Our findings reveal that, as oxygen concentration decreases, the combined combustion index of the coal samples also decreases during the oxygen-absorption stage. Additionally, the apparent activation energy of coal increases with its conversion rate (temperature). We observe a shift in the reaction mechanism from three-dimensional dissipation mode to two-dimensional as the oxygen concentration decreases. Notably, the activation energy initially rises and then decreases with increasing conversion (temperature) during the pyrolysis combustion stage, with a shortened phase of increased activation energy at lower oxygen concentrations. Furthermore, the kinetic mechanism transitions from stochastic nucleation and growth to one-dimensional phase-boundary mode with decreasing oxygen concentration. These insights enhance our understanding of coal oxidation combustion in low-oxygen environments, contributing to strategies for mitigating coal spontaneous combustion.

PurposeThe main purpose here is to explore the unsteadiness characteristics in magnetized flow of Reiner–Rivlin nanofluid. Energy and concentration expressions are modeled by utilizing Buongiorno model for nanoscale particles. Additionally, Joule heating and activation energy are also deliberated.Design/methodology/approachThe bvp4c solver in MATLAB is employed for graphical and numerical outcomes.FindingsA similar trend of temperature field is seen against thermophoresis and Brownian movement parameters. Thermal transport rate decreases via Prandtl number. Augmentation in mass transport rate is noted through unsteadiness parameter.Originality/valueTo the best of author’s knowledge, no such consideration has been given in the literature yet.

Air leakage rates are a crucial factor affecting the oxygen supply and heat storage capacity of coal spontaneous combustion (CSC) in goaf in underground coalmines. A suitable airflow rates in goaf can significantly promote CSC. To accurately reveal the effect of airflow rate on CSC, a bituminous coal was selected, and the thermogravimetric and differential scanning calorimetry were used to receive the mass loss characteristics and enthalpy changes for sample. Six characteristic temperatures and five reaction stages were identified under multiple airflow rates, the combustion characteristics were calculated, and apparent activation energy was obtained by Coats–Redfern, FWO and Starink methods. The results indicate that with the increasing airflow rate, the characteristic temperatures decreased firstly and then rose, of which all characteristic temperatures at 150 mL min −1 were the lowest. Meanwhile, the stability and combustion capability of sample were prominently enhanced, and its exothermic ability and heat release enlarged, and the reaction capability with oxygen was the highest at 150 mL min −1 . Then, the Avrami–Erofeev equation ( n  = 3/2) was verified to be the most appropriate mechanism of the coal sample. In addition, apparent activation energy of sample was the lowest at 150 mL min −1 , and the CSC ability was sensibly strengthened. The findings will serve as a theoretical basis for the initial stage on CSC in underground coalmines.

Ultrafine materials with unique characteristics have a broad range of utilization. The motivation of this paper was to investigate the size effect on the thermo-oxidative degradation behaviors and chemical kinetics of polystyrene (PS) solid particles. In this study, microscopic PS particles with four different-diameter distributions, containing 5, 10, 15, and 50 μm, were picked as tested samples. Then, the thermogravimetry analysis test of PS samples was conducted under an air atmosphere with three different heating rates. Activation energies were calculated and validated by multiple traditional kinetic approaches, and a linear relationship between activation energy and the reciprocal of the particle diameter has been concluded. A distributed activation energy model (DAEM) with two pseudo-components was developed and employed to decouple the polyurethane pyrolysis in the air atmosphere. A set of n th-order reactions is hypothesized to occur with a constant pre-exponential factor and having a continuous activation energy distribution pattern conforming to the Gaussian density function in each kinetic process. A multi-parameter optimization program was developed to calculate ten DAEM parameters based on the experimental data from three different heating rates by avoiding the ill condition resulting from the kinetic compensation effect. Moreover, the numerical relationship between activation energies and particle diameter has been analyzed. The results of this study are instructive for the determination method of kinetic triplets, the modification of reaction models, and especially the construction of waste polymer kinetics and combustion models.