Transfer Diffusion Research Articles

Filtration flow rate at low convection volume in continuous hemodiafiltration using cytokine adsorbing hemofilter does not affect cytokine clearance in an experimental model

BackgroundIn recent years, continuous kidney replacement therapy (CKRT) with a cytokine adsorbing hemofilter (CAH) has been used in clinical practice to treat acute kidney injury associated with hypercytokinemia. Two types of CAH are available, including polymethyl methacrylate (PMMA) and polyethylenimine-coated polyacrylonitrile (AN69ST), each having distinct adsorption mechanisms. PMMA adsorbs substances with hydrophobic bases through hydrophobic interactions, resulting in occlusion of the membrane pores. AN69ST adsorbs positively charged substances through electrostatic bonds because its bulk layer is negatively charged. In both CAH, the adsorption efficiency of cytokines with large molecular weights is likely affected by filtration rather than by diffusion transfer. These adsorbing-type membranes have limitations in terms of filtration flow rate because of their low water permeability. The relationship between the adsorption effect and the filtration flow rate in CAH-CKRT has not been fully investigated.PurposeThe effect of low-convection volume settings below 600 mL/h on cytokine adsorption characteristics was experimentally investigated in CKRT.Materials and methodsTest solutions, including albumin (4.5%), creatinine (10 mg/dL), interleukin (IL)-6 (1000 pg/mL), and IL-8 (1000 pg/mL), were prepared. The test solution was circulated through the experimental circuit of continuous hemodiafiltration (CHDF) with a total convection volume ranging from 0 to 600 mL/h. The test solution was circulated through the experimental circuit of hemodiafiltration (CHDF) with various dialysate flow rates (QD; 0, 200, 400, and 600 ml/h) and filtration flow rates (QF; 0, 200, 400, and 600 ml/h). Samples immediately before and after CAH from the sampling port of the circuit were collected seven times at 1-min intervals. Clearances of creatinine, IL-6, and IL-8 were calculated for each setting of the proportions of QD and QF during CKRT using PMMA and AN69ST.ResultsCreatinine clearance increased with increasing QD and QF, regardless of the membrane type. There were no significant differences in the adsorption clearance of IL-6 and IL-8 among the different settings, regardless of the membrane type.ConclusionThe results of this study indicate that the cytokine clearance at a low convection volume in CAH-CKRT was not affected by the filtration flow rate.

Amorphization Stabilizes Te‐Based Aqueous Batteries via Confining Free Water

AbstractTellurium (Te), with its rich valence states (−2 to +6), could endow aqueous batteries with potentially high specific capacity. However, achieving complete and stable hypervalent Te0/Te4+ electrochemistry in an aqueous environment poses significant challenges, owing to the sluggish reduction kinetics, easy dissolution of Te4+ species, and a controversial energy storage mechanism. Herein, we demonstrate a crystallographic regulation strategy for robust aqueous Te redox electrochemistry. With strong hydrogen bonding, NH4Ac confines free water, prompting the amorphization of TeO2 (a‐TeO2). In situ synchrotron characterization, spectroscopy analysis, electrochemical evaluation, and theoretical calculations reveal a specific 4 e− solid‐solid transition pathway (Te to a‐TeO2) with accelerated diffusion and charge transfer kinetics, attributed to a closer unoccupied electron orbital to the Fermi level and a reduced water desorption energy barrier in a‐TeO2. Impressively, the a‐TeO2/Te redox exhibits a high reversible capacity of 834 mAh g−1 (99% of Te redox utilization), superior rate performance (644 mAh g−1 at 10 A g−1), and an ultralong lifespan (over 3000 cycles). These findings prove a new tactic to advance aqueous Te redox electrochemistry toward high‐energy aqueous batteries.

Bifunctional lignin-based hydrogel membrane with enhanced structural stability for synergistic uranium uptake.

Developing biomass-based adsorbents with superior uranium uptake performance is imperative yet challenging for the sustainable development of nuclear energy. Herein, we constructed a novel lignin-based adsorbent (DLP@PAO) with dual functional groups and enhanced structural stability via ingenious integration of lignin and polyamidoxime. The two-step modification strategy was innovatively employed to phosphorylate lignin, significantly enhancing the phosphorylation efficiency and achieving an over eight-fold increase in the U(VI) uptake capacity of lignin. Benefiting from its double-crosslinked network and the strong electrostatic repulsion of phosphate groups, the DLP@PAO membrane, featuring a porous honeycomb structure, exhibits favorable shrinkage resistance even in acidic aqueous environments, facilitating the diffusion and mass transfer of U(VI) ions within the adsorbent. Notably, the synergistic effect of DLP and PAO components on U(VI) uptake was comprehensively verified through experimental data combined with density functional theory (DFT) calculation, which endows DLP@PAO with exceptional uptake capacity (701.02mg g-1) and selectivity (Kd=1.45×105 mL g-1) towards U(VI) ion. Moreover, DLP@PAO achieved a high U(VI) uptake efficiency of over 91.07% in a dynamic column device with 10 L of simulated wastewater, indicating its immense potential for practical wastewater treatment. Mechanistic studies revealed that the synergistic coordination between UO22+ ions and O as well as N atoms in the phosphate and amidoxime groups is primarily responsible for the U(VI) uptake by DLP@PAO. This work opens a new direction for the value-added utilization of lignin and advances the development of lignin-based adsorbents for U(VI) uptake.

Continuous photo-oxidation of methane to methanol at an atomically tailored reticular gas-solid interface

Photo-oxidation of methane (CH4) using hydrogen peroxide (H2O2) synthesized in situ from air and water under sunlight offers an attractive route for producing green methanol while storing intermittent solar energy. However, in commonly used aqueous-phase systems, photocatalysis efficiency is severely limited due to the ultralow availability of CH4 gas and H2O2 intermediate at the flooded interface. Here, we report an atomically modified metal-organic framework (MOF) membrane nanoreactor that promotes direct CH4 photo-oxidation to methanol at the gas-solid interface in a reticular open framework. We show that the domino synergy between colocalized single-atom palladium and iron on MOF nodes enables efficient generation and in situ utilization of H2O2 in the absence of liquid water, thus circumventing H2O2 dilution. Meanwhile, the “breathable” MOF membrane, optimized by solar-driven interfacial water management, provides high-flux channels to facilitate efficient gas diffusion and rapid methanol desorption and transfer. As a result, we demonstrate over 210 hours of continuous photosynthesis of 0.25 M methanol with unity selectivity, achieving an exceptional methanol productivity of 14.4 millimoles per gram of catalyst per hour.

Amorphization Stabilizes Te-Based Aqueous Batteries via Confining Free Water.

Tellurium (Te), with its rich valence states (-2 to +6), could endow aqueous batteries with potentially high specific capacity. However, achieving complete and stable hypervalent Te0/Te4+ electrochemistry in an aqueous environment poses significant challenges, owing to the sluggish reduction kinetics, easy dissolution of Te4+ species, and a controversial energy storage mechanism. Herein, we demonstrate a crystallographic regulation strategy for robust aqueous Te redox electrochemistry. With strong hydrogen bonding, NH4Ac confines free water, prompting the amorphization of TeO2 (a-TeO2). In situ synchrotron characterization, spectroscopy analysis, electrochemical evaluation, and theoretical calculations reveal a specific 4 e- solid-solid transition pathway (Te to a-TeO2) with accelerated diffusion and charge transfer kinetics, attributed to a closer unoccupied electron orbital to the Fermi level and a reduced water desorption energy barrier in a-TeO2. Impressively, the a-TeO2/Te redox exhibits a high reversible capacity of 834 mAh g-1 (99% of Te redox utilization), superior rate performance (644 mAh g-1 at 10 A g-1), and an ultralong lifespan (over 3000 cycles). These findings prove a new tactic to advance aqueous Te redox electrochemistry toward high-energy aqueous batteries.

Synergistically Inducing Ultrafast Ion Diffusion and Reversible Charge Transfer in Lithium Metal Batteries Using Bimetallic Molybdenum-Titanium MXenes.

Metal batteries have captured significant attention for high-energy applications, owing to their superior theoretical energy densities. However, their practical viability is impeded by severe dendrite formation and poor cycling stability. To alleviate these issues, a 3D-structured bimetallic-Mo2Ti2C3Tx based fiber electrode was fabricated in this study and analyzed experimentally and computationally. The bimetallic Mo-Ti composition of MXenes synergistically achieved low binding and formation energies with lithium. In particular, the minimal lattice mismatch between the deposited Li metal and the Mo2Ti2C3Tx MXene anode substrate led to improved Li formation energy with respect to the MXene surface. Moreover, the synergy of the bimetallic Mo-Ti composition of the Mo2Ti2C3Tx MXene fiber substrate helped to amplify ion diffusion and reversible charge transfer. Consequently, the bimetallic MXene electrode exhibited an impressive Coulombic efficiency (99.08%) even at a high current density (5 mA cm-2) and a fixed cutoff capacity of 1 mA h cm-2 with prolonged cycle life (650 cycles). This report highlights a promising advancement in addressing the critical challenges facing metal battery operation, thereby offering an approach to improving performance for high-energy applications.

Ti3C2Tx/Au NPs/PPy ternary heterostructure-based intra-capacitive self-powered sensor for DEHP detection.

Phthalate esters, particularly di(2-ethylhexyl) phthalate (DEHP), are widely used plasticizers found in various consumer products, posing significant environmental and health risks due to their endocrine-disrupting effects. In this study, a novel enzyme-free intra-capacitive biofuel cell self-powered sensor (ICBFC-SPS) was developed. The ICBFC-SPS integrated a ternary heterostructure-based capacitive anode and a cathode with a sensing interface into a single-chamber electrolytic cell. The ternary heterostructure based on Ti3C2Tx MXene with ultra-small Au NPs and polypyrrole (PPy) NPs was prepared to provide the efficient glucose oxidation and robust electron production. Furthermore, the charge storage capacity was significantly enhanced through a synergistic combination of the double-layer capacitor mechanism of Ti3C2Tx and the pseudocapacitive behavior of PPy. Additionally, the intercalation of PPy NPs expanded the interlayer spacing, promoting electrolyte ion diffusion and charge transfer. The ICBFC-SPS demonstrated exceptional sensitivity with a linear detection range from 0.05 to 100000 ng/L and a detection limit of 9.51 pg/L for the sensitive and selective detection of DEHP in complex environmental and biological samples. The ICBFC-SPS addresses the limitations of traditional methods by providing a self-powered, highly sensitive, and portable platform for rapid, on-site DEHP detection. This work underscores the potential of self-powered sensors as transformative tools for real-time environmental monitoring and public health protection.

An electrochemical sensor based on electrodeposited methylene blue on a carbon nanotube decorated hydrogel for the detection of ascorbic acid.

In this study, a self-assembled electrochemical sensor was prepared by coating with a carbon nanotube (CNT) decorated hydrogel (HG) combined with electrodeposition of methylene blue (MB), and then used for the detection of ascorbic acid (AA). The three-dimensional network of HG has the advantages of large electroactive surface area, rapid diffusion and electron transfer rate, strong adhesive ability and stabilization of the polymerized MB. The MB provides high electrocatalytic activity and works as an electron transfer mediator to facilitate the oxidation of AA. The successful synthesis of the hydrogel and the preparation of the sensor are confirmed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The layer-by-layer assembly was identified by AFM with the heights of 22.1 nm and 186.8 nm for the hydrogel and MB layers, respectively. Under the optimal conditions, the sensor has a linear range of 0.1 mM to 10 mM and a detection limit of 0.05 mM. What's more, the prepared sensor also exhibits good stability (current retention of 91.22% after 100 cycles for testing 0.25 mM AA), excellent anti-interference ability, good reproducibility (RSD of 4.26% for five independent experiments), excellent operational stability (RSD of 1.66% for 30 consecutive AA additions), fast response time (<4 s) and shows satisfactory results in the detection of AA in vitamin C tablets.

Effect of various novel pre-treatments on drying and rehydration behaviour of ginger and quality attributes of dried ginger

Abstract The present study focused on the influence of different solution-based osmo-sonic pre-treatments on the drying, rehydration, and quality attributes of ginger cubes. Osmo-sonic pre-treated drying followed the empirical page model, and rehydration was better explained by the exponential model. All the pre-treatments increased the effective moisture diffusivity and mass transfer coefficient, which increased the drying rate from 22.34 to 79.78 %. Pre-treatment led to an increase in appearance by an increase in L* and a* and a decrease in b*. The FTIR spectra showed the absence of a new functional group, but a change was observed in the characteristics band upon pre-treatment. The comparison of different pre-treatment showed that the CA + US pre-treatment had a better drying profile, whereas DW + US had a better antioxidant profile with the highest TPC (22.31 mg GAE/g), TFC (58.37 mg QE/g), DPPH inhibition (89.01 %), and ABTS assay (13.27 mg TE/g).

Enhancing Supercapacitor Performance with Biomass-Derived Carbon Materials: A Review of Dimensional Innovations

Supercapacitor high-power density, rapid charge/discharge rates, long lifespan, and environmental friendliness have positioned them as extremely promising energy storage options. This study examines the physical and chemical characteristics of several biomass materials and their impact on supercapacitor performance. Additionally, we delve into the classification and fundamental concepts of supercapacitors. Biomass-derived carbon compounds exhibit abundant surface features and naturally occurring hierarchical structures that enhance electrochemical reactions, including diffusion and ion transfer. Historically, biomass has been the primary raw material for synthesizing innovative porous carbon compounds, representing a significant advancement in electrode materials for supercapacitors. Our study emphasizes the potential applications of one-, two-, and three-dimensional carbon compounds derived from biomass as electrode materials for supercapacitors by reviewing the latest research in this field. Additionally, we discuss the challenges faced today and the opportunities for enhancing the efficiency of carbon-based supercapacitor electrodes in the future.

Cathodic Reversible Selenium Redox Chemistry Over Oxygen Vacancies‐Dominated V2O3/Graphene for Rechargeable Mg‐Se Batteries

AbstractRechargeable magnesium‐selenium (Mg‐Se) batteries are characterized by high theoretical volumetric specific capacity, good cycling stability, and economical effectiveness. However, great challenges including limited capacity, low Coulombic efficiency, and short cycle life are encountered due to sluggish electrochemical kinetics and severe polyselenide shuttles. Herein, the active Se is encapsulated in hollow V2O3 microspheres and then connected by reduced graphene oxide (rGO) conductive network as the mixed‐dimensional cathode materials to accelerate reversible Se redox chemistry for high‐performance Mg‐Se batteries. Rich oxygen vacancies are generated within hollow porous V2O3 microspheres during their phase transformation under reductive atmosphere. The unique three‐/two‐dimensional (3D/2D) heterostructure of the Se‐loaded cathode materials (Se‐V2O3/G‐Vo) can facilitate Mg2+ diffusion and charge transfer, and also provide rich reaction sites for the polyselenide conversion. Additionally, the defect‐rich structure can deliver strong adsorption ability and abundant catalytic sites for reversible polyselenide conversion. Consequently, the Se‐V2O3/G‐Vo cathode materials show high reversible capacity of 580 mAh g−1 with 99.1% capacity retention at 200 mA g−1 current density after 80 cycles. This work should enlighten the design concept of metal oxide and graphene as Se‐based cathode materials for high‐rate and long‐life Mg‐Se batteries.

Charge injection dynamics in oxygen-functionalized and heteroatom-doped reduced graphene oxide and their impact on supercapacitor performance: An experimental and DFT investigation

To elucidate the synergistic effects of oxygen functional groups (OFGs) and heteroatoms (HAs) on charge injection dynamics and the electrochemical performance of reduced graphene oxide (rGO), a combination of experimental techniques and density functional theory (DFT) analyses were employed. GO was synthesized using a modified Hummers method and the sample reduced hydrothermally at 150 °C demonstrated the highest areal capacitance of 817 mF/cm2. To understand the diffusion and charge transfer characteristics, the diffusion coefficient and distribution of relaxation time studied using the Electrochemical Impedance Spectroscopy data. Further the X-ray photoelectron spectroscopy (XPS) confirmed the incorporation of OFGs and HAs in the rGO. A partially oxygen-functionalized, nitrogen, and sulfur-doped graphene (NS-POG) model was constructed based on the XPS data and analyzed using DFT. The projected density of states analysis revealed a Fermi level shift, indicating the introduction of excess electrons due to incorporating OFGs and HAs in graphene, thereby improving the charge carrier concentration in the partially reduced or oxidized systems. The NS-POG system exhibited a quantum capacitance of 85.92 μF/cm2. Additionally, potassium ion (K+) adsorption studies indicated that the adsorption energy was highest near sulfur atoms, suggesting that electrolyte ions exhibit enhanced electrochemical activity in proximity to sulfur. These findings provide insight into the mechanisms by which OFGs and HAs enhance the performance of rGO and highlighting the potential of NS-rGO in supercapacitor applications.

Electrophoretic velocity of ion-releasing colloidal particles

By means of a matched asymptotic expansions approach the electrophoretic velocity and zeta potential of a catalytic particle that uniformly releases ions have been investigated. Attention is focused on large, compared to diffuse layer, particles characterized by the surface potential Φs and Damköhler number Da. The latter represents the ratio of the surface reaction rate to the diffusive transfer one. For vanishing Da, we recover the classical Smoluchowski formula for the electrophoretic velocity, which states that the zeta potential of the particle is equal to Φs and that the migration direction is determined by its sign. For small values of Da we show that the migration velocity is controlled mostly by Φs and affected by an ion release only slightly. However, even small Da can induce the electrophoresis of electro-neutral particles that would be immobile if inert. For larger Da the direction of migration and the sign of zeta potential become independent of Φs and are solely determined by the difference in diffusivity of released cations and anions. Still, the surface potential affects the magnitude of the particle velocity.

Analysis of Nanofluid Flow Over a Heated Circular Cylinder using the Volume of Fluid (VOF) Approach

This study employs a two‐phase Volume of Fluid (VOF) model to investigate the flow and heat transfer characteristics of Al₂O₃-water nanofluid over a heated circular cylinder at a Reynolds number of 100. Nanoparticle volume fractions (Φ) ranging from 1% to 10% were analyzed. A comprehensive grid-independence study and code validation were conducted to ensure the accuracy of the results. Increasing (Φ) from 0% to 10% led to significant changes in flow parameters: the mean drag coefficient increased by 27.8% (from 1.33 to 1.7), the fluctuating lift coefficient rose by 56.5% (from 0.23 to 0.36), and the Strouhal number increased by 6.7% (from 0.164 to 0.175). Heat transfer enhancement was observed with increasing nanoparticle concentration, as evidenced by the local Nusselt number at the front stagnation point (θ = 0°) rising by approximately 40% over the same (Φ) range. The study revealed significant changes in pressure distribution around the cylinder, with higher (Φ) values smoothing the pressure gradient and altering the separation point. Time-averaged temperature contours demonstrated more uniform thermal distributions and reduced wake sizes at higher (Φ) values, indicating improved thermal diffusion and heat transfer efficiency. The (VOF) model successfully captured complex two-phase flow dynamics, revealing asymmetric nanoparticle distributions in the wake region at higher concentrations. These findings have important applications in thermal management systems, including electronic and energy systems, potentially leading to more efficient cooling systems and heat exchangers.

Analysis of Entropy Generation Due to Heat and Mass Transfer in Porous Electrode of PEFC

During operation of polymer electrolyte fuel cells (PEFCs), the complicated multi-physics phenomena including heat and mass transfer, ionic and electronic transport and electrochemical reaction simultaneously occur in porous electrodes. It has been well known that the kinetic-theory based oxygen reduction reaction (ORR) and two-phase transport within cathode electrodes cause the severe overpotentials and performance degradation. In the previous studies, the energy loss in fuel cells and electrochemical devices has been experimentally investigated by using electrochemical impedance spectroscopy (EIS) and classified into the activation, ohmic and concentration polarization. EIS technique is a powerful method to analyze the sources of their performance loss, however, it cannot locally identify the key factors and transport processes causing the loss. To further enhance the power density and efficiency of PEFCs, it’s necessary to discriminate the critical phenomena influencing on the performance degradation using an alternative approach and design the better electrode/channel structure for reducing the energy loss. Several researchers attempted to apply the analysis of entropy generation to the elucidation of performance loss mechanisms in fuel cells and electrochemical devices [1-3]. Entropy is a physical property representing the thermodynamic irreversibility. The entropy generation analysis enables to identify the dominant phenomena inducing the overpotential in such devices and contributes to design the optimum structure minimizing the energy dissipation. Kjelstrup and Røsjorde [1] numerically estimated the local entropy production in various layers of a one-dimensional PEFC and found that the dissipation of energy due to charge transport in the electrolyte membrane is more important than the that of diffusion in the electrode. The author introduced the entropy generation analysis into the two-phase flow simulation for the cathode diffusion media of a PEFC and succeeded to locally estimate the entropy production rate due to oxygen diffusion within the porous electrode in the past work [3]. This study further analyzed the distributions of entropy production rate due to the heat transfer, diffusion and electrochemical reaction in the cathode porous electrode in more detail using the conventional two-phase flow PEFC model and extracted the significant process affecting the cathode overpotential. The author also investigated the effect of land/channel geometry on the local entropy generations of these phenomena in the electrode and discussed how to design its structure reducing the entropy generation.Fig. 1 shows the numerical results of the two-phase flow simulation and the entropy generation analysis in the cathode electrode. The two-phase flow model used in this study was developed by Natarajan and Nguyen [4]. (a), (b) and (c) denote the through-plane distribution of temperature across the cell and the profiles of oxygen concentration and water saturation in the cathode gas diffusion layer (GDL), respectively. (d), (e) and (f) are the distributions of entropy production rate due to heat flux, oxygen diffusion and ORR in the electrode. The fuel cell was operated for 50 s at the temperature of 80 oC and the current density of 1.0 A/cm2. It was noted that the entropy generation due to the electrochemical reaction gives a larger effect on the cathode overpotential than that of diffusion and heat transfer. That is very well known. The entropy production rate of ORR at the catalyst layer under the channel is larger than that under the land because the sufficient oxygen supply progresses the reaction more actively. Furthermore, the land/channel geometry has an influence on the entropy generation of diffusion and heat transfer in the cathode electrode. The entropy production rates due to oxygen diffusion and heat flux become remarkably high under the boundary between the channel and land owing to the large gradients of its concentration and temperature. To reduce the entropy generation in the porous electrode with the land/channel configuration, it’s necessary to design the cell structure uniformizing the reaction distribution and alleviating the gradients of current, concentration and temperature.

Characterizing Turbulence and Wave Dynamics Under Rotation: Enhancing Semiconductor Processes through CFD Analysis and High-Speed Imaging

IntroductionIn semiconductor manufacturing, precision in wafer processing is crucial for advancing device technology. The spinning system, essential for wafer cleaning and etching, significantly impacts device quality by facilitating dynamic air-liquid interactions, affecting surface chemistry. This study utilizes Computational Fluid Dynamics (CFD) and high-speed camera analysis to explore turbulence and wave dynamics, confronting Fast Fourier Transform (FFT) analysis against the Kolmogorov cascade to improve manufacturing outcomes by understanding these dynamics more thoroughly.Experimental SetupOur approach integrates high-speed imaging with advanced CFD simulations to capture and analyze the wave phenomena in spinning liquid films. High-speed cameras are strategically positioned to provide comprehensive side and top views, enabling detailed observation of wave formation and interaction with the air. Concurrently, CFD simulations offer a granular view of the fluid dynamics, focusing on the generation and propagation of turbulence within the liquid film. The application of FFT analysis to CFD data allows us to delve into the turbulent wave dynamics, specifically investigating the energy cascade, per the Kolmogorov theory [1]. This methodology not only deepens our understanding of wave behavior but also highlight its potential impacts on key factors defining the exchange kinetics of the liquid-air interface.DiscussionFor a single wafer, a gas molecule, characterized by a diffusion coefficient D, will diffuse through the liquid film of thickness h to reach the wafer surface in a time approximated by t ~ h²/D. Specifically for oxygen, (D~2×10⁻⁹ m²/s) and 100µm thin film, the process takes about 5 seconds, while the coverage of the liquid takes less than 0.5s so an order of magnitude lower [2]. The Peclet number (Pe), defined by Pe=Uh/D, represents the advection to diffusion ratio. Here, Pe~10-4 >> 1 indicating advection dominance. This suggests wave and hydrodynamics (laminar vs. turbulence) primarily transport air into the liquid. Near the wafer edge, where the flow speeds up and the liquid film thins out, gas molecules reach the wafer faster than at its center.Advection rates are higher on wavy surfaces due to complex streamlines shaped by the undulating contours of the interface. This will enhance mixing transport, while the increased surface area boosts heat and mass exchange. Depending on wave celerity, recirculation atop the waves further boost local mixing [3,4].In Figure 1, the FFT analysis indicates that turbulent dynamics align with the Kolmogorov cascade, highlighting a spectrum of energy dissipation that could significantly impact oxygen diffusion and heat transfer. These findings suggest that the wave-induced turbulence could be leveraged to optimize the distribution of reactive species and thermal management during the spinning process. It highlights that the energy is injected by the swirling and concentric waves near the center of the wafer.In Figure 2, the Iribaren number, a dimensionless metric for classifying wave breaking patterns [5], is extracted from the liquid thickness distribution on wafer. It compares the slope steepness to the wave steepness, predicting whether waves will spill, plunge, or surge. Spilling waves, associated with low Iribarren numbers below 0.5 as found in our study, gently dissipate energy over wide areas. These spilling waves dissipate energy over long distances, breaking into smaller wavelets and introducing turbulence showing complex interactions between wave dynamics and the wafer.Figure 3 shows the dynamics of spilling waves with concentric waves collapsing towards the edge using a high-speed camera. This phenomenon is observed in a side view of a centrally dispensed fluid on a rotating wafer. The captured speed range is notably high, exceeding 50 km/h. The size and number of waves are affected by the rotation speed. A wave will collapse faster at high rpm because of a thinner film and higher centrifugal forces.ConclusionThis research reveals the relationship between wave dynamics in spinning liquid films and their potential impact on semiconductor manufacturing efficiency. The synergy of high-speed imaging, CFD analysis, and FFT insights not only enhances our understanding of fluid dynamics but also paves the way for optimizing wafer cleaning and etching techniques. This study lays the groundwork for future technological advancements, promising to elevate the precision, efficiency, and quality of semiconductor production.

Turbulence Structure and Mixing in Strongly Stable Couette Flows over Thermally Heterogeneous Surfaces: Effect of Heterogeneity Orientation

AbstractDirect numerical simulations (DNS) of plane Couette flows over thermally heterogeneous surfaces at bulk Reynolds number $$Re=10^4$$ R e = 10 4 and bulk Richardson number $$Ri=0.25$$ R i = 0.25 are performed. The focus of the present study (that extends previous work by the authors) is the effect of surface heterogeneity orientation on boundary-layer structure. The temperature of the upper and lower walls is either homogeneous or varies sinusoidally, where the temperature-wave crests are either normal or parallel to the mean flow (HETx and HETy cases, respectively). Importantly, the horizontal-mean surface temperature is the same in all simulations. The stratification is strong enough to quench turbulence over a homogeneous surface, but turbulence survives over heterogeneous surfaces. In all heterogeneous cases, both molecular diffusion and turbulence transfer momentum down the gradient of mean velocity. The total (turbulent plus diffusive) heat flux is down-gradient, but quasi-organized eddy motions generated by the surface thermal heterogeneity induce heat transfer up the gradient of the mean temperature. Comparative analysis of HETx and HETy cases shows that the configuration with the spanwise heterogeneity is more turbulent and more efficient in transporting momentum and heat vertically than its counterpart with the streamwise heterogeneity. Vertical profiles of mean fields and turbulence moments differ considerably between the HETx and HETy cases, e.g., the streamwise heat flux differs not only in magnitude but also in sign. A close examination of the second-order turbulence moments, vertical-velocity and temperature skewness, and the flow eddy structure helps explain the observed differences between the HETx and HETy cases. The implications of our DNS findings for modelling turbulence in stably-stratified environmental and industrial flows with surface heterogeneity are discussed.

Transition from ballistic to diffusive heat transfer in a chain with breaks.

The transition from a ballistic to a diffusive regime of heat transfer is studied using two models. The first model is a one-dimensional chain with bonds, capable of dissociation. Interparticle forces in the chain are harmonic for bond deformations below a critical value, corresponding to the dissociation, and zero above this value. A kinetic description of heat transfer in the chain is proposed using the second model, namely, a gas of noninteracting quasiparticles, reflecting from randomly occurring barriers. The motion of quasiparticles mimicks heat (energy) transfer in the chain, while the barriers mimic dissociated bonds. For the gas, a kinetic equation is derived and solved analytically. The solution demonstrates the transition from the ballistic regime at small times to the diffusive regime at large times. In the diffusive limit, the distance traveled by a heat obeys square-root asymptotics as in the case of classical diffusion. However, the shape of the fundamental solution for temperature differs from the Gaussian function and therefore the Fourier law is not satisfied. Two examples are considered to demonstrate that the presented kinetic model is in good qualitative agreement with the results of the numerical solution of the chain dynamics. The presented results show that bond dissociation is an important mechanism underlying the transition from ballistic to diffusive heat transfer in one-dimensional chains.

Modeling of the Nanofiltration Process Based on Convective Diffusion Theory

The article formulates the state of the problem of improving the theoretical calculation of the nanofiltration kinetic characteristics in the time cycle of separation of industrial solutions containing copper(II), iron(III), trisodium phosphate and OP-10 (a wetting agent used in electroplating, a product of treating a mixture of mono- and dialkylphenols with ethylene oxide) using the equations of convective diffusion, hydrodynamics and mass transfer. To calculate the kinetic characteristics of the nanofiltration process, the mathematical model was improved by numerically solving the equations of convective diffusion, the Navier–Stokes equation and the flow continuity equation in a polar coordinate system with initial and boundary conditions. The theoretical results obtained in the process of an analytical solution of the system of equations allow calculating changes in concentrations in the permeate and retentate tracts and the permeate volume during nanofiltration separation. The acceptability of the developed nanofiltration method for separating solutions is assessed by comparing the calculated data according to the mathematical model with the experimental data obtained on the nanofiltration unit during separation of solutions containing copper(II), iron(III), trisodium phosphate and OP-10.

Biopolymers as three-dimensional structural binders for nickel-cobalt sulfide supercapacitor electrodes

Ion diffusion and electron transfer are hindered by commonly used hydrophobic binders, which directly affect the electrochemical performance of the electrodes. Hydrophilic binders are selected to efficaciously solve the problem of relatively low actual specific capacitance and rate performance in the field of nickel cobalt sulfide electrode materials. In the paper, RuCoNiS electrodes were prepared using polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), xanthan gum (XG), and chitosan (CS) as binders. The surface wettability, morphological structure, specific surface area, and electrochemical performance of electrodes with different binders were analyzed by XRD, SEM, BET, CV, GCD, and EIS, etc. It's shown that the synthesis of CoNi2S is confirmed by XRD. The XPS results verify the existence of RuO2 and Ni2+/Ni3+ and Co2+/Co3+ redox couples. A cross-linked network structure is formed on the surface of the RuCoNiS by CS. The CS-RuCoNiS electrode has the largest specific surface area and microporosity. Ion migration in the electrolyte is facilitated by the excellent wettability of the CS-RuCoNiS electrode. The CS-RuCoNiS electrode reachs 1193.52 F g-1, which is 1.74 times higher than that of the PTFE-RuCoNiS electrode at 1 A g-1. The CS binder with its three-dimensional structure has the highest ionic conductivity of 2.29 × 10-4 S cm-1, a lower Rct, good cycling stability with a capacity retention of 84.3 % after 5000 cycles at 200 mV s-1, and excellent rate performance of 85.6 %. It can provide a practical application in supercapacitors.