Near-equilibrium Conditions Research Articles

Self-Organization of Micro- and Nanosystems in the Form of Patterns

In this work, the peculiarities of self-organization of patterned micro- and nanosystems under near-equilibrium condensation conditions were consistently considered. The criteria for stationarity of near-equilibrium condensation were introduced, and interrelations between the condensate local growth kinetics and the corresponding local technological parameters were described. Dissipative self-organization of small supersaturations in physically and chemically active medium-condensate systems were compared. The effectiveness of the unification of dissipative self-organization of small supersaturations and conservative self-organization of patterned micro- and nanosystems formation was shown, which forms the basis of a new concept of complete self-organized systems.

The Complex and Spatially Heterogeneous Nature of Degradation in Heavily Cycled Li-ion Cells

Abstract As service lifetimes of electric vehicle (EV) and grid storage batteries continually improve, it has become increasingly important to understand how cells perform after extensive cycling. The multifaceted nature of degradation in Li-ion cells can lead to complex behavior that may be difficult for battery management systems or operators to model. Accurate characterization of heavily cycled cells is critical for developing accurate models, especially for cycle-intensive applications like second-life grid storage or vehicle-to-grid charging. In this study, we use operando synchrotron X-ray diffraction (SR-XRD) to characterize a commercially manufactured polycrystalline NMC622 pouch cell that was cycled for more than 2.5 years. Using spatially resolved synchrotron XRD, the complex kinetics and spatially heterogeneous behavior of such cells can be mapped and characterized under both near-equilibrium and non-equilibrium conditions. The resulting data is complex and multifaceted, requiring a different approach to analysis and modelling than what has been used in the literature. To show how material selection can impact the extent of degradation, we compare the results from polycrystalline NMC622 cells to an extensively cycled single-crystal NMC532 cell with over 20,000 cycles – equivalent to a total EV traveled distance of approximately 8 million km (5.5 million miles) over six years.

Micellar Nanogels from Alginate-Based Diblock Copolysaccharides.

Alginates are marine polysaccharides known for their ability to selectively bind calcium ions and form hydrogels. They are widely used in biomedical applications but are challenging to produce as nanogels. Here we introduce a self-assembly route to create stable alginate-based nanogels under near-equilibrium conditions. Guluronate (G) blocks, which interact with divalent cations such as Ca2+, Ba2+, and Sr2+, were extracted from alginates and covalently linked through their reducing end to the reducing end of dextran (Dex) chains, forming linear block copolymers that self-assemble into micellar nanogels with a core-corona structure in the presence of these ions. Real-time dynamic light scattering (DLS) and small-angle neutron scattering (SANS) were used to study the self-assembly mechanism of the copolymer during dialysis against divalent ions. For the G12-b-Dex51 copolymer, we achieved spherical micelles with an 8 nm radius and an aggregation number of around 20. Although the type of divalent cation affected micelle stability, it did not influence their size. Micellar nanogels are dynamic structures, capable of ion exchange, and can disassemble with chelating agents like ethylenediamine tetraacetic acid (EDTA).

Bulk viscous late acceleration under near equilibrium conditions in f(R, T) gravity with mixed dark matter

Numerous studies have tried to explain the observed late acceleration of the Universe as being caused by the bulk viscosity associated with the dark matter (DM) component. However, for driving the said accelerated expansion, all such models require a violation of near equilibrium conditions (NECs) associated with the background viscous theory. But recently, it was found that, with the aid of a cosmological constant, it is possible to maintain NEC for the bulk viscous warm DM during certain evolutionary epochs of the Universe. Nevertheless, this negated the possibility of having a ‘solely’ viscous-driven late acceleration in Einstein gravity within the NEC limit. In the present study, we investigate a model of the Universe composed of mixed DM components, with viscous DM, and inviscid cold DM as its constituents, in the context of R+2λTvm gravity, and show that the model predicts late acceleration by satisfying NEC, critical energy condition and second law of thermodynamics (SLT) throughout the evolution, even in the absence of a cosmological constant. One intriguing feature observed in this model is the possibility of having a negative bulk viscous coefficient and yet satisfying the SLT. Finally, by applying both theoretical and observational constraints on the model parameters, we determined the best-fit values of model parameters and thereby analyzed the evolutionary behavior of some relevant cosmological observables.

Photoexcitation-induced passivation of SnO2 thin film for efficient perovskite solar cells.

A high-quality tin oxide electron transport layer (ETL) is a key common factor to achieve high-performance perovskite solar cells (PSCs). However, the conventional annealing technique to prepare high-quality ETLs by continuous heating under near-equilibrium conditions requires high temperatures and a long fabrication time. Alternatively, we present a non-equilibrium, photoexcitation-induced passivation technique that uses multiple ultrashort laser pulses. The ultrafast photoexcitation and following electron-electron and electron-phonon scattering processes induce ultrafast annealing to efficiently passivate surface and bulk defects, and improve the crystallinity of SnO2, resulting in suppressing the carrier recombination and facilitating the charge transport between the ETL and perovskite interface. By rapidly scanning the laser beam, the annealing time is reduced to several minutes, which is much more efficient compared with conventional thermal annealing. To demonstrate the university and scalability of this technique, typical antisolvent and antisolvent-free processed hybrid organic-inorganic metal halide PSCs have been fabricated and achieved the power conversion efficiency (PCE) of 24.14% and 22.75% respectively, and a 12-square-centimeter module antisolvent-free processed perovskite solar module achieves a PCE of 20.26%, with significantly enhanced performance both in PCE and stability. This study establishes a new approach towards the commercialization of efficient low-temperature manufacturing of PSCs.

Improving adsorption-based direct air capture performance through operating parameter optimization

Direct air capture (DAC) of CO2 through adsorption is a promising technology for mitigating climate change, but its high cost presents a significant challenge to large-scale implementation. To address this issue, this study presents a dynamic fixed-bed model of the closed-inlet temperature-vacuum swing adsorption (TVSA) process and investigates the impact of various operating and model parameters on DAC performance via dynamic simulation. The results indicate that optimizing the durations of the adsorption and regeneration phases is crucial for improving cyclic DAC performance. Maximizing the working capacity by driving both phases towards near-equilibrium conditions generally leads to the lowest specific energy requirement (SER), while cutting the adsorption phase earlier increases the CO2 productivity. Additionally, appropriate choices of operating parameters, such as feed gas velocity and vacuum pressure, can significantly improve DAC process performance. Furthermore, placing the DAC unit in a location with favourable temperature and humidity conditions, affordable heat source, and elevated CO2 concentration can greatly enhance the process and its cost-effectiveness. These individual approaches have the potential to multiply productivity and decrease SER by increasing the working capacity, shortening the cycle duration, and minimizing the absolute energy consumption. However, optimizing the DAC process necessitates careful consideration of trade-offs between productivity, SER, and various constraints. These insights, along with the developed model, can provide a valuable basis for further advancement of DAC technology.

Experimental examination of the phase transition of water on silica at 298 K.

The objective of this study was to investigate the prediction of the wetting characteristics obtained from the equilibrium adsorption analysis using the Zeta adsorption isotherm approach with an experimental study. Water vapor's adsorption and wetting characteristics on a hydroxylated and nano-polished silica substrate were studied in near-equilibrium conditions at temperatures near 298K. Using a UV-visible interferometer, water vapor adsorbate film thicknesses were measured and converted into amount adsorbed per unit area. The current results show that the wetting transition occurred at an average subcooling value of 0.39K, less than the predicted value of 0.49K. All the different experimental observations showed growth of film thickness as a function of subcooling value with a maximum film thickness of 12.6nm. The analysis of the results further showed that the maximum stable film was in a metastable state that then condensed in a dropwise manner, if perturbed by increasing the subcooling. The study further revealed that the adsorbate is unstable after transitioning. The solid surface energy calculated by including the near-equilibrium observations was comparable and close to that of the equilibrium studies, thus supporting solid surface energy as a material property.

Reaction Mechanism Development for Methane Steam Reforming on a Ni/Al2O3 Catalyst

In this work, a reliable kinetic reaction mechanism was revised to accurately reproduce the detailed reaction paths of steam reforming of methane over a Ni/Al2O3 catalyst. A steady-state fixed-bed reactor experiment and a 1D reactor catalyst model were utilized for this task. The distinctive feature of this experiment is the possibility to measure the axially resolved temperature profile of the catalyst bed, which makes the reaction kinetics inside the reactor visible. This allows for understanding the actual influence of the reaction kinetics on the system; while pure gas concentration measurements at the catalytic reactor outlet show near-equilibrium conditions, the inhere presented temperature profile shows that it is insufficient to base a reaction mechanism development on close equilibrium data. The new experimental data allow for achieving much higher quality in the modeling efforts. Additionally, by carefully controlling the available active surface via dilution in the experiment, it was possible to slow down the catalyst conversion rate, which helped during the adjustment of the reaction kinetics. To assess the accuracy of the revised mechanism, a monolith experiment from the literature was simulated. The results show that the fitted reaction mechanism was able to accurately predict the experimental outcomes for various inlet mass flows, temperatures, and steam-to-carbon ratios.

Hierarchical micro-macro acceleration for moment models of kinetic equations

Fluid dynamical simulations are often performed using cheap macroscopic models like the Euler equations. For rarefied gases under near-equilibrium conditions, however, macroscopic models are not sufficiently accurate and a simulation using more accurate microscopic models is often expensive. In this paper, we introduce a hierarchical micro-macro acceleration based on moment models that combines the speed of macroscopic models and the accuracy of microscopic models. The hierarchical micro-macro acceleration is based on a flexible four step procedure including a micro step, restriction step, macro step, and matching step. We derive several new micro-macro methods from that and compare to existing methods. In 1D and 2D test cases, the new methods achieve high accuracy and a large speedup.

Pervasive carbonation of peridotite to listvenite (Semail Ophiolite, Sultanate of Oman): clues from iron partitioning and chemical zoning

Abstract. Earth's long-term cycling of carbon is regulated from mid-ocean ridges to convergent plate boundaries by mass transfers involving mantle rocks. Here we examine the conversion of peridotite to listvenite (magnesite + quartz rock) during CO2 metasomatism along the basal thrust of the Semail Ophiolite (Fanja, Sultanate of Oman). At the outcrop scale, this transformation defines reaction zones, from serpentinized peridotites to carbonated serpentinites and listvenites. Based on a detailed petrological and chemical study, we show that carbonation progressed through three main stages involving the development of replacive textures ascribed to early stages, whilst carbonate (± quartz) veining becomes predominant in the last stage. The pervasive replacement of serpentine by magnesite is characterized by the formation of spheroids, among which two types are identified based on the composition of their core regions: Fe-core and Mg-core spheroids. Fe zoning is a type feature of matrix and vein magnesite formed during the onset carbonation (Stage 1). While Fe-rich magnesite is predicted to form at low fluid XCO2 from a poorly to moderately oxidized protolith, our study evidences that the local non-redox destabilization of Fe oxides into Fe-rich magnesite is essential to the development of Fe-core spheroids. The formation of Fe-core spheroids is followed by the pervasive (over-)growth of Mg-rich spheroids and aggregates (Stage 2) at near-equilibrium conditions in response to increasing fluid XCO2. Furthermore, the compositions of carbonates indicate that most siderophile transition elements released by the dissolution of primary minerals are locally trapped in carbonate and oxides during matrix carbonation, while elements with a chalcophile affinity are the most likely to be leached out of reaction zones.

Analysis of Ancient Slag Inclusion-Metal Systems as a Method to Disclose Processing Thermo-chemical Parameters: The Case Study of a Medieval Lombard Steel Bar from Northern Italy

An archaeometallurgical characterization of a VI to VII century Lombard steel bar from Ponte di Val Gabbia I site (northern Italy) was performed to reconstruct its manufacturing process and extract processing thermochemical parameters (i.e., temperature and oxygen chemical potential) from the slag inclusion-metal systems. Metallographic observations by optical microscopy and Vickers microhardness measurements indicated that the steel bar was forged from a heterogeneous steel lump, most probably an iron bloom, which was cooled in the air after the forging process. The chemical composition of non-metallic inclusions was determined by scanning electron microscopy coupled with X-ray dispersive spectroscopy. A multivariate statistical analysis of the smelting-derived non-metallic inclusions chemistry allowed to conclude that the steel bar was obtained by the direct or bloomery method. Under the hypothesis of local near-equilibrium conditions for the slag inclusion-metal systems, a thermodynamic-based strategy was adopted to estimate the firing conditions in the bloomery furnace in terms of both temperature and oxygen chemical potential of the reducing gas atmosphere. In particular, the computed temperatures are in the range of 1003 °C to 1171 °C, whereas the values of oxygen chemical potential vary between − 447.47 and − 385.79 kJ/mol.

A new perspective on skin-friction contributions in adverse-pressure-gradient turbulent boundary layers

For adverse-pressure-gradient turbulent boundary layers, the study of integral skin-friction contributions still poses significant challenges. Beyond questions related to the integration boundaries and the derivation procedure, which have been thoroughly investigated in the literature, an important issue is how different terms should be aggregated. The nature of these flows, which exhibit significant in-homogeneity in the streamwise direction, usually results in cancellation between several contributions with high absolute values. We propose a formulation of the identity derived by Fukagata et al. (2002), which we obtained from the convective form of the governing equations. A new skin-friction contribution is defined, considering wall-tangential convection and pressure gradient together. This contribution is related to the evolution of the dynamic pressure in the mean flow. The results of the decomposition are examined for a broad range of pressure-gradient conditions and different flow-control strategies. We found that the new formulation of the identity allows to readily identify the different regimes of near-equilibrium conditions and approaching separation. It also provides a more effective description of control effects. A similar aggregation between convection and pressure-gradient terms is also possible for any other decomposition where in-homogeneity contributions are considered explicitly.

Unveiling re-entrant phase behavior and crystalline-amorphous interactions in semi-conducting polymer:small molecule blends.

It has been reported recently that conjugated polymer:small molecule systems might exhibit complex, re-entrant phase behavior with hourglass or closed-loop miscibility gaps due to an 'apparent' lower critical solution temperature branch. However, the study did not firmly establish if the observations were reflecting equilibrium or not. To assure that the observed shapes of the binodals via a mixing experiment represent local near-equilibrium conditions that capture complex molecular interactions or equation-of-state effects, we present here the liquidus and the binodal for the exact same systems, i.e., PTB7-Th:PC61BM, PffBT4T-C9C13:PC71BM and PTB7-Th:EH-IDTBR, with the liquidus measured via a demixing experiment with long annealing time of days to weeks. We observe that the binodal displayed consistent trends with the liquidus, revealing an underlying thermodynamic and not microstructural or kinetic cause behind the complex phase behavior. Our results highlight the need for a novel, sufficiently complex physical model for understanding these non-trivial phase diagrams of semi-conducting materials. We also discover that the composition difference (Δϕ) between liquidus and binodal reflects the crystalline-amorphous interaction, exhibiting a linear relationship with the binodal composition (ϕb,polymer), i.e., Δϕ increases as χaa decreases. This possibly provides a new approach for obtaining the crystalline-amorphous interaction parameter χca(T) beyond the commonly used melting point depression method, which estimates χca near the melting temperature Tm of the crystalline component. The capability of obtaining χca(T) over a more extended temperature range may encourage more extensive studies and facilitate the understanding of χca in general, but particularly for all the novel non-fullerene acceptors that are able to crystallize.

Mass Accommodation of Water on Ice at Environmentally Relevant Temperatures: Insights from Fast Scanning Calorimetry.

Using a conceptually simple, quasi-adiabatic, fast scanning calorimetry technique, we have investigated the sublimation kinetics of ice films with thicknesses ranging from 14 to 400 nm at environmentally relevant temperatures, between 223 and 268 K. The technique enables accurate determination of ice sublimation rates into vacuum under the conditions of free molecular flow during rapid yet quasistatic heating. The measured sublimation fluxes yield the vapor pressure of the ice samples, which is indistinguishable from that derived from experiments under near-equilibrium conditions. Thus, in agreement with the microscopic reversibility principle, we conclude that the mass accommodation coefficient of water by ice is unity and temperature-independent in the temperature range of the studies. We discuss these findings in the context of current computational and theoretical research into the chemistry and physics of aqueous interfaces.

Density change upon solidification of silicon cast irons

Amongst the possible defects that can appear during casting, voids due to solidification shrinkage is certainly the most usual and important in the case of cast irons. For any predicting work, the knowledge of the density of the phases of interest, namely liquid, austenite and graphite, is a prerequisite. The density of liquid and austenite in silicon cast irons are here assessed as function of composition and temperature based on the literature review. Estimate of theoretical expansion upon solidification are then derived for lamellar and spheroidal graphite cast irons and compared to reported experimental values obtained in near-equilibrium conditions.

Formation of smoother grain boundaries in 2D materials using high deposition rates during the last stages of growth

Grain boundary (GB) roughness can affect electronic and mechanical properties of two-dimensional materials. This roughness depends crucially on the growth process by which the two-dimensional material is formed. To investigate the key mechanisms that govern the GB roughening, we have performed kinetic Monte Carlo simulations of a simple model that includes particle attachment, detachment, and diffusion. We have studied the closure of the gap between two flakes during growth, and the subsequent formation of the GB for a broad range of model parameters. The well-known near-equilibrium (attachment-limited) and unstable (diffusion-limited) growth regimes are identified, but we also observe a third regime when the precursor flux is sufficiently high to saturate the gap between the edges with diffusing species. This high deposition rate regime forms GBs with spatially uncorrelated roughness, which quickly relax to smoother configurations. Extrapolating the numerical results (with support from a theoretical approach) to edge lengths and gap widths of some micrometres, we confirm the advantage of this regime to produce GBs with minimal roughness faster than near-equilibrium conditions. This suggests an unexpected route towards efficient growth of two-dimensional materials with smooth GBs.

Study of a Viscous ΛWDM Model: Near-Equilibrium Condition, Entropy Production, and Cosmological Constraints

Extensions to a ΛDM model have been explored in order to face current tensions that occur within its framework, which encompasses broadening the nature of the dark matter (DM) component to include warmness and a non-perfect fluid description. In this paper, we investigated the late-time cosmological evolution of an exact solution recently found in the literature, which describes a viscous warm ΛDM model (ΛWDM) with a DM component that obeys a polytropic equation of state (EoS), which experiences dissipative effects with a bulk viscosity proportional to its energy density, with proportionality constant ξ0. This solution has the particularity of having a very similar behavior to the ΛCDM model for small values of ξ0, evolving also to a de Sitter type expansion in the very far future. We explore firstly the thermodynamic consistences of this solution in the framework of Eckart’s theory of non-perfect fluids, focusing on the fulfillment of the two following conditions: (i) the near-equilibrium condition and (ii) the positiveness of the entropy production. We explore the range of parameters of the model that allow to fulfill these two conditions at the same time, finding that a viscous WDM component is compatible with both ones, being in this sense, a viable model from the thermodynamic point of view. Furthermore, we constrained the free parameters of the model with the observational data coming from supernovae Ia (SNe Ia) and the observational Hubble parameter data (OHD), using these thermodynamics analyses to define the best priors for the cosmological parameters related to the warmness and the dissipation of the DM, showing that this viscous ΛWDM model can describe the combined SNe Ia+OHD data in the same way as the ΛCDM model. The cosmological constraint at 3σ CL gives us an upper limit on the bulk viscous constant of order ξ0∼106 Pa·s, which is in agreement with some previous investigations. Our results support that the inclusion of a dissipative WDM, as an extension of the standard cosmological model, leads to a both thermodynamically consistent and properly fitted cosmological evolution.

Fluid flow and vortex-shaped structure formation mechanisms ofAl-Ag-Ge alloy

<p indent="0mm">Fluid flow and solidification mechanisms of Al₇₀Ag₂₀Ge₁₀ alloy were systematically investigated using electromagnetic levitation, induction, arc, and resistance melting techniques coupled with finite element simulation method. A unique type of vortex-shaped microstructure was formed in these four experiments. This was different from the result under slow solidification conditions. The formation of the vortex-shaped structure was affected by fluid flow and cooling rate of alloy melt. The Lorentz force caused turbulent flow in alloy melt, while the turbulent flow during arc melting was driven by arc force under electromagnetic levitation or induction melting conditions. The surface tension and buoyancy force caused laminar flow in alloy melt during the resistance melting process. Due to rapid flow, the Ag₂Al phase nucleated ahead of the Al phase, primarily under near-equilibrium conditions. The metastable Ag₂Al dendrites grew as vortex-shaped morphology and preserved the melt flow pattern during solidification. The increased cooling rate caused a rapid growth of metastable Ag₂Al dendrites with increased vortex density. The curvature radius of metastable Ag₂Al dendrites decreased with enhanced melt flow; meanwhile, the more drastic nucleation and growing competition among phases occurred. Finally, irregular Al, Ag₂Al, and Ge ternary eutectics fully formed inside the vortex-shaped structure.

Programmable heating and quenching for efficient thermochemical synthesis

Conventional thermochemical syntheses by continuous heating under near-equilibrium conditions face critical challenges in improving the synthesis rate, selectivity, catalyst stability and energy efficiency, owing to the lack of temporal control over the reaction temperature and time, and thus the reaction pathways1-3. As an alternative, we present a non-equilibrium, continuous synthesis technique that uses pulsed heating and quenching (for example, 0.02 s on, 1.08 s off) using a programmable electric current to rapidly switch the reaction between high (for example, up to 2,400 K) and low temperatures. The rapid quenching ensures high selectivity and good catalyst stability, as well as lowers the average temperature to reduce the energy cost. Using CH4 pyrolysis as a model reaction, our programmable heating and quenching technique leads to high selectivity to value-added C2 products (>75% versus <35% by the conventional non-catalytic method and versus <60% by most conventional methods using optimized catalysts). Our technique can be extended to a range of thermochemical reactions, such as NH3 synthesis, for which we achieve a stable and high synthesis rate of about 6,000 μmol gFe-1 h-1 at ambient pressure for >100 h using a non-optimized catalyst. This study establishes a new model towards highly efficient non-equilibrium thermochemical synthesis.

High-Resolution Single-Molecule Magnetic Tweezers.

Single-molecule magnetic tweezers deliver magnetic force and torque to single target molecules, permitting the study of dynamic changes in biomolecular structures and their interactions. Because the magnetic tweezer setups can generate magnetic fields that vary slowly over tens of millimeters-far larger than the nanometer scale of the single molecule events being observed-this technique can maintain essentially constant force levels during biochemical experiments while generating a biologically meaningful force on the order of 1-100 pN. When using bead-tether constructs to pull on single molecules, smaller magnetic beads and shorter submicrometer tethers improve dynamic response times and measurement precision. In addition, employing high-speed cameras, stronger light sources, and a graphics programming unit permits true high-resolution single-molecule magnetic tweezers that can track nanometer changes in target molecules on a millisecond or even submillisecond time scale. The unique force-clamping capacity of the magnetic tweezer technique provides a way to conduct measurements under near-equilibrium conditions and directly map the energy landscapes underlying various molecular phenomena. High-resolution single-molecule magnetic tweezerscan thus be used to monitor crucial conformational changes in single-protein molecules, including those involved in mechanotransduction and protein folding.