Effect Of Electrical Double Layer Research Articles

An investigation on effect of EDL on heat transfer of micro heat pipe with square and triangular cross section

Electronic industries have always been trying to improve the efficiency of electronic devices with small dimensions through thermal management of this equipment, thus increasing the use of small thermal sinks. In this study micro heat pipes with triangular and square cross sections have been manufactured and tested. One of the main objectives is to obtain an understanding of micro heat pipes and their role in energy transmission with electrical double layer (EDL). Micro heat pipes are highly efficient heat transfer devices, which use the continuous evaporation/condensation of a suitable working fluid for two-phase heat transport in a closed system. Since the latent heat of vaporization is very large, heat pipes transport heat at small temperature difference, with high rates. Because of variety of advantage features these devices have found a number of applications both in space and terrestrial technologies. The theory of operation micro heat pipes with EDL is described and the micro heat pipe has been studied. The temperature distribution have achieved through five thermocouples installed on the body. Water and different solution mixture of water and ethanol have used to investigate effect of the electric double layer heat transfer. It was noticed that the electric double layer of ionized fluid has caused reduction of heat transfer.

Coupling PhreeqC with electro-diffusion tests for an accurate determination of the diffusion properties on cementitious materials

An improved numerical method as regard with the widely used analytical approximation is presented for determining the transport properties from electro-diffusion tests. Based on the geochemical software PhreeqC, this study aims to better understand and quantify the part of each phenomenon in the diffusion process: (i) the geometrical material properties (as porosity and tortuosity); (ii) the chemical reactions between chloride ions and the cement solid phase; (iii) electro-capillarity effects (such as electrical double layer effects). Tests have been performed on CEM I hydrated cement pastes of different W/C ratio (0.35; 0.42 and 0.50) with different chloride concentrations (500 and 50 mol/m3). The results revealed a good accuracy on the chloride diffusion coefficients DE, Cl− given by the numerical model while having a weak set of main adjustable parameters. The large amount of experimental data collected during the tests increases the robustness of the model.

Interfacial energy for solutions of nanoparticles, surfactants, and electrolytes

AbstractThe addition of surfactants to modify the surface property of nanoparticles (NPs) from hydrophilic to hydrophobic also enhances their interfacial properties. Several approaches were previously proposed to calculate the surface tension/interfacial tension (IFT) for different systems in the presence of NPs, surfactants, and electrolytes. However, most of these approaches are indirect and require several measured parameters. Therefore, a mathematical model is developed here to calculate the surface tension/IFT for these systems. The developed model takes into account the cohesive energy due to the interaction of the surfactant CH2 groups, the electric double layer effect due to the interaction among the ions of NPs, surfactants, and electrolytes, and the dipole–dipole interaction of NPs and electrolytes. The developed model is compared and validated with the laboratory experimental data in literature. The results reveal further understanding of the mechanisms involved in stabilization of oil/water emulsion in the presence of NPs, surfactants, and electrolytes.

Enhanced densification and dielectric properties of CaTiO3-0.3NdAlO3 ceramics fabricated by direct coagulation casting

Severe sintering conditions always cause defects that increase the dielectric loss of microwave ceramics. Direct coagulation casting (DCC) of submicron powder suspension, was applied to accelerate densification and enhance dielectric properties of 0.7CaTiO3-0.3NdAlO3 (CTNA) ceramics. The rapid in-situ coagulation of suspension was achieved by tailoring the pH value to the isoelectric point to weaken the repulsion of electric double layer and steric hindrance effect. Compared with the dry-pressed samples, the DCC-fabricated samples are more compacted, which provides a high initial densification value and a shortened diffusion path, and consequently promotes the material transportation and composition homogenization that inhibits the segregation of CaAl12O19. Additionally, the submicron powders accelerate the phase transition and domains growth, leading to a significant reduction of lattice defects in microstructure. Therefore, Q⋅f value of CTNA ceramics reaches more than 40,000 GHz, which is improved by 15 % compared with that of dry-pressed samples sintered under the same conditions.

Modelling two-layer nanofluid flow in a micro-channel with electro-osmotic effects by means of Buongiorno’s mode

A fully developed steady immiscible flow of nanofluid in a two-layer microchannel is studied in the presence of electro-kinetic effects. Buongiorno’s model is employed for describing the behavior of nanofluids. Different from the previous studies on two-layer channel flow of a nanofluid, the present paper introduces the flux conservation conditions for the nanoparticle volume fraction field, which makes this work new and unique, and it is in coincidence with practical observations. The governing equations are reduced into a group of ordinary differential equations via appropriate similarity transformations. The highly accurate analytical approximations are obtained. Important physical quantities and total entropy generation are analyzed and discussed. A comparison is made to determine the significance of electrical double layer (EDL) effects in the presence of an external electric field. It is found that the Brownian diffusion, the thermophoresis diffusion, and the viscosity have significant effect on altering the flow behaviors.

Bioinspired Flexible, Dual‐Modulation Synaptic Transistors toward Artificial Visual Memory Systems

AbstractA prominent challenge for artificial synaptic devices toward artificial perception systems is hardware redundancy, which demands neuromorphic devices that integrate both sensing and processing functions. Inspired by the biological visual and nervous systems, a novel flexible, dual‐modulation synaptic field‐effect transistor (SFET) is demonstrated in this work. The flexible SFET is constructed with zinc oxide nanowires and sodium alginate, which acts as the semiconductor layer and the gate dielectric, respectively. An excitatory postsynaptic current in this artificial synapse can be triggered by both electrical and ultraviolet stimuli as presynaptic spikes as a result of the electric double layer effect and the photoelectric effect. More importantly, through the co‐modulation of light and electric stimuli, the memory level of the artificial synapses can be tuned based on the transformation between short‐term plasticity and long‐term plasticity initiated by the gate voltage. Different voltages can modulate the memory retention levels of the optical inputs similar to the function of the optic nerve system. The underlying mechanisms for the SFET are investigated using Fourier transform infrared spectroscopy, photoluminescence, and X‐ray photoelectron spectroscopy. Overall, the devices provide a novel idea to mimic visual memory, showing a promising strategy for future electronic eyes.

A high-performance electroactive PPy/rGO/NiCo-LDH hybrid film for removal of dilute dodecyl sulfonate ions

An electroactive ion exchange hybrid film of polypyrrole/reduced graphene oxide/NiCo-layered double hydroxide (PPy/rGO/NiCo-LDH) with three-dimensional (3D) “sand rose” flower-like structure was fabricated by a two-step electrodeposition method. NiCo-LDH nanosheets were electrodeposited on the surface of polypyrrole/graphene oxide (PPy/GO) conducting substrate for the removal of dodecyl sulfonate ions (DS− ions) with low concentrations. Herein, the electroreduction of GO to rGO enhanced the electron conductivity and the unique structure of hybrid PPy/rGO/NiCo-LDH film ensured the fast diffusion of electrons as well as ions. The electrochemical performance of hybrid film was characterized by cyclic voltammetry (CV) and electrochemical impedance spectrum (EIS), and the effects of the applied electrode potential, initial concentration of DS− ions and pH of the simulated wastewater on the uptake kinetics of DS− ions were investigated. As a result, the coexisting anions had no obvious effect on the adsorption of DS− ions and the removal percentage of DS− ions reached 92.31% in a 10 mg L−1 DS− solution with 0.8 V electrode potential. Especially, in the pH ranging from 5.0 to 9.0, the DS− ions were efficiently removed. In addition, the double-driven ion exchange mechanism coupling electric double-layer (EDL) effect of rGO and pseudo capacitance effect of PPy to remove DS− ions was proposed based on the X-ray photoelectron spectroscopy (XPS) and CV analyses. It is expected that such a novel PPy/rGO/NiCo-LDH hybrid electroactive ion-exchange film separation technology based on the double-driven mechanism could be a potential technique for wastewater treatment.

Boehmite and Akaganeite 1D and 2D Mesostructures: Synthesis, Growth Mechanism, Ageing Characteristics and Surface Nanoscale Roughness Effect on Water Purification

The role of surface nanoscale roughness on the charging behavior of nanostructuredγ-AlOOH (Boehmite) andβ-FeOOH (Akaganeite)/γ-AlOOH (Boehmite) mesostructures deposited onto siliceous substrates has been investigated. Two-dimensional (2D) quantum-sized and one-dimensional (1D) nanometer sizeγ-AlOOH (Boehmite) structures and 2D atomically-thinβ-FeOOH (Akaganeite) nanobelts with a mean width of approximately 10 nm were deposited onto siliceous substrates in aqueous processes at moderate temperatures. Low cost and large scale manufacturing of siliceous substrates coated with 2D and 1Dγ-AlOOH (Boehmite) crystallites of 2.7 ± 0.5 nm in diameter, with an average length of 2.9 ± 0.9 nm and 250 ± 50 nm, respectively, that were further functionalized with atomically thin 2Dβ-FeOOH (Akaganeite) nanobelts was demonstrated. Zeta potentials of surfaces have been characterized by direct measurement of streaming potentials in NaCl aqueous electrolyte. A model explaining the pH dependent behavior of the zeta potential was proposed. The isoelectric point values of rough nanostructured surfaces are three pH units higher as compare to the flat crystallineγ-AlOOH (Boehmite) andβ-FeOOH (Akaganeite) surfaces, resulting in a high removal efficacy of submicron particles from aqueous suspension by the surfaces with combined microscale and nanoscale structures. This suggests the existence of a coupling electrokinetic effect of the local electrical double layer (EDL) fields with the local flow fields.

State of charge estimation for lithium-ion battery using an electrochemical model based on electrical double layer effect

This paper focuses on an efficient fundamental approach of the electrochemical model of lithium-ion batteries (LIBs), especially considering the effect of Electrical Double Layer (EDL) potential on the over-potential of batteries. Firstly, the electrode solid phase and electrolyte liquid phase in LIBs are modelled by electrochemical theory, especially emphasizing the influence of EDL structure. Three-parameter parabola method is effectively employed to simplify the model. Furthermore, a parameter identification method based on genetic algorithm is proposed according to the structure characteristics of EDL model. The accuracy of model is verified by comparing the output voltage of the EDL model under 0.1∼2C charging/discharging, 1C pulse discharging and New European Driving Cycle (NEDC) condition with the experimental terminal voltage. Finally, the battery SOC estimation method is developed by using the extended Kalman filter (EKF) algorithm based on EDL model and is verified by the 1C pulse discharge and the NEDC condition experiments. The results show that the proposed algorithm can accurately estimate the SOC value of LIBs. In addition, the algorithm has a strong correction effect on the initial SOC error and convergence.

Analytical solutions for unsteady forced convection pulsating flow in a microchannel in the presence of EDL effects

A forced convection flow driven in a microchannel by an applied pressure gradient that fluctuates with small amplitude harmonically in time in the presence of electrical double layer effects is investigated. An analytical expression for the electrostatic potential is obtained via Poisson’s equation. Based on this solution, we further obtain analytical solutions for velocity and temperature for both the cases Pr ≠ 1 and Pr = 1. Results show that they match each other as Pr → 1− and Pr → 1+. The explicit expression of the transient Nusselt number is derived. We notice that the Debye–Hückel parameter γ and the angular velocity Ω are key factors for flow behaviours. Our proposed study adds some new insights by including the time-dependent pressure term that is usually overlooked in previous works. It is expected that this work could help to understand the transportal mechanisms of forced convection flow in microfluidic equipment and instruments.

Modelling for water-based liquid lubrication with ultra-low friction coefficient in rough surface point contact

Abstract In this paper, a composite model of average flow Reynolds equation with considering electrical double layer (EDL) effect in roughness surface is proposed to analysis aqueous solution lubrication performance. The numerical simulations are conducted to explain the phenomena of water-based lubrication with ultra-low friction coefficient. The results have showed that: The EDL hydrodynamic and asperity contact will work together to balance the out applied load. The EDL effect has greatly benefited for enhancing film formation and decreasing the friction to obtain the ultralow friction coefficient. To achieve the liquid superlubricity, the sliding velocity, liquid viscosity, surface roughness and EDL effect should be comprehensively considered. The proposed numerical model could be provided a better understanding and design thin film lubrication behavior.

Transport and retention of biogenic selenium nanoparticles in biofilm-coated quartz sand porous media and consequence for elemental mercury immobilization

Bacterial biofilms are structured cell communities embedded in a matrix of extracellular polymeric substances (EPS) and a ubiquitous growth form of bacteria in the environment. A wide range of interactions between biofilms and nanoparticles have been reported. In the present study, the influence of a mixed bacterial biofilm on retention of biogenic selenium nanoparticles (BioSeNPs) and consequences for immobilization of elemental mercury (Hg0) in a porous quartz sand system were examined. BioSeNPs were significantly retained in the presence of a biofilm through electrical double layer effects, hydrogen bonding, and hydrophobic, steric and bridging interactions. Moreover, enhanced surface roughness, pore clogging, sieving and entrapment effects mediated by the biofilm also contributed to deposition of BioSeNPs. Whereas, thiol groups associated with the biofilm is a little helpful for the capture of Hg0. It is proposed that oxidative complexation between Hg0 and thiol compounds or S containing organic matter in the biofilm may result in the formation of Hg2+-thiolate complexes and HgS during the binding of Hg0 with BioSeNPs. The formation of mercury selenide was also involved in Hg0 immobilization in the porous quartz sand system.

Influence of water dilution on performance of chromium polymer weak gel in porous medium

In order to explore the influence of water dilution on performance of Cr3+ polymer weak gel in porous medium, the performances of pure polymer solution and Cr3+ polymer weak gel were studied according to the laboratory testing of viscosity, micro-structure performances (polymer molecule aggregate dimension, polymer molecule aggregate configuration and Zeta potential), seepage characteristics and oil displacement effect under the condition of water dilution. The results indicated that, after diluting by water, pure polymer solution and Cr3+ polymer weak gel had an almost same viscosity, but there were obvious differences in micro-structure performance and seepage characteristics. Different with pure polymer solution, with the decrease of polymer concentration, on the one hand, the influence of free Cr3+ on electric double layer and shielding effect on electrostatic exclusion got weaker, on the other hand, water molecules were attracted by hydrophilic groups on the Cr3+ polymer weak gel molecular chains and then entered into the three-dimensional spatial structure of Cr3+ polymer weak gel, producing hydration and expansion. Therefore, the polymer molecule aggregate dimension of Cr3+ polymer weak gel presented a trend of continuous increasing. This characteristic was good for keeping the injection pressure at a higher value during diluting in the porous medium, which could be used to improve oil recovery in offshore oilfield through conducting injection of water-alternating- Cr3+ polymer weak gel.

Study of electrokinetic effects for heat transfer in microchannel with sinusoidal thermal boundary conditions

PurposeThe purpose of this study is to obtain the numerical as well as regularity results for the nonlinear elliptic set of equations arising in the study of fluid flow in microchannel induced by the pressure in the presence of interfacial electrokinetic effects.Design/methodology/approachFor the numerical study, the authors implemented traditional FDM approach, and for the regularity results they used the classical energy estimates. The interfacial electrokinetic effects result in an additional source term in classical momentum equation, hence affecting the characteristics of the flow and heat transfer. The sinusoidal temperature variation is assumed on side walls.FindingsThe results were obtained for various combinations of physical parameters appearing in the governing equations. This study concludes that in the presence of electric double layer, the average heat transfer rate reduces along with larger values of Reynolds number. It is observed that the heat transfer increases with the increase in amplitude ratio and phase deviation. The flow behavior and heat transfer rate inside the microchannel are also strongly affected by the presence of κ (kappa).Originality/valueTo the best of the authors’ knowledge, the problem of heat transfer through microchannel in combination with sinusoidal temperature variation at boundary with electric double layer effects has not been considered previously. Hence, this paper focuses on the influence of the sinusoidal boundary temperature distributions on both sidewalls of a rectangular microchannel through parallel plates with electrokinetic effects on the pressure-driven laminar flow. In addition, a detailed mathematical analysis is also to be carried out to verify the regularity of this model with the proposed boundary conditions. The study used the classical energy method to get the regularity results.

Natural Vermiculite Enables High‐Performance in Lithium–Sulfur Batteries via Electrical Double Layer Effects

AbstractLithium–sulfur batteries with potentially high specific energy are viewed as very promising candidates for next‐generation lightweight and low‐cost rechargeable batteries. However, sulfur‐based cathodes suffer from dissolution of polysulfides causing shuttle effects. Here, in order to confine elemental sulfur and anchor the polysulfides, a novel host that is an inexpensive natural clay mineral, viz., vermiculite is proposed. When compared to regular carbon–sulfur composites, vermiculite–sulfur composites offer promising rate capability and much better cycling stabilities, displaying capacity retentions of ≈89 and ≈93% within 200 cycles at C/2 and 1 C, respectively, and ≈60 % at C/5 within 1000 cycles. Postmortem studies, advanced adsorption tests, density functional theory calculations, and zeta potential measurements in combination with intrinsic characteristics of the natural vermiculite provide insights into the new mechanism. The vermiculite contains naturally present surface cations which show a strong tendency to adsorb Sn2− anions, hence protecting them from dissolution. The excess surface charge is most probably compensated by excess Li+ in the space charge zones which is beneficial for charge transfer and local conductivity. The reported results show that natural clay‐minerals are promising sulfur hosts being able to fixate sulfides via electrical double layer effects, thus enabling high‐performance in lithium–chalcogen batteries.

A Feedback Interpretation of the Doyle–Fuller–Newman Lithium-Ion Battery Model

The Doyle-Fuller-Newman “psuedo-2-D” electrochemical model of a lithium-ion battery is shown to have a feedback structure when electric double-layer effects are included. This opens the possibility for the model to be rigorously analyzed using input-output systems theory. Several immediate consequences of the feedback structure are discussed, including observability and well-posedness issues, and an application to reduced-order modeling is described.

(Invited) Sensing, Measuring and Imaging Surface Charge with Nanoscale Pipettes

Charge is a fundamental interfacial property that governs physical and chemical interactions at surfaces. The workings of catalysts, sensors, separation devices, biological interfaces, and colloidal systems, are well known to be strongly influenced by surface charge, typically present in the form of protonated or deprotonated chemical moieties. Directly measuring and sensing charge in situ, especially for small (micro/nanoscale), heterogeneous charge distributions presents an interesting and important challenge for electroanalytical chemistry. Here, recent studies in mapping interfacial charge with scanning ion conductance microscopy (SICM) and the influence of electrolyte concentration on the charge sensing mechanism will be described. We have validated a SICM method that utilizes current‐voltage relationships that can be intuitively understood for surface charge detection. The effect of electrical doublelayer (EDL) thickness on signal generation on chemically modified surfaces will be demonstrated. The differential measurement approach used here allows visualization of individual domains of surface charge. EDL effects are modeled with finite element simulations, and extension of our studies to sensing at biological samples and mineral samples will be demonstrated.

Equivalent circuit model modified for free-standing bilayer lipid membranes beyond 1 TΩ

A cell is the basic functional unit of living organisms. Bilayer lipid membranes (BLMs), which form cell membranes can be assembled by using artificial methods. The electrochemical characteristics of BLMs are normally investigated using electrochemical impedance spectroscopy (EIS); however, the equivalent circuit need to be modified by the experimental conditions. In this study, we formed plain BLMs to determine the underlying equivalent circuit model of free-standing BLMs, and we measured the electrical characteristics using EIS. To analyze the results of EIS, we proposed equivalent circuit models including electrical double layer (EDL) effects on both sides of a BLM. We also extracted and evaluated the electrochemical parameters; the aperture-suspended BLMs using an Si chip having tapered edge recorded TΩ-order membrane resistances, which were one order higher than those reported in most previous studies. Regarding the capacitances of EDL, we compared the extracted values and the calculated results.

A fractal study for the effective electrolyte diffusion through charged porous media

Electrolyte diffusion in electrolyte solutions exists in various areas including rechargeable batteries, soil physics and chemical engineering. In this paper, a fractal model based on the capillary model and fractal theory of porous media is proposed to quantify the effective electrolyte diffusivity in porous media with consideration of the electrical double layer (EDL) effects. The present model explicitly relates to the micro-structural parameters of porous media and electrokinetic parameters. To validate this model, a comparison is carried out with experimental data and semi-analytical model results, and yields satisfying agreement. Besides, the influences of the parameters (the porosity, equivalent particle diameter, ratio of the minimum pore radius to the maximum pore radius, molar concentration, zeta potential, and dimensionless parameter β) are discussed in details.

Study on pore size effect of low permeability clay seepage

Low-permeability clays are characterized by a large amount of clay minerals and a special distribution of pore sizes, so their seepage behavior shows an obvious pore size effect. Therefore, conventional seepage theories show deviations in describing the seepage behavior of low-permeability clays. This paper analyzes two reasons for the pore size effect in low-permeability clay seepage: the pore distribution property and the electric double layer effect of the clay surface. Considering these two factors, the seepage theory of the pore size effect based on the microscale seepage of the circular tube model is proposed. The rationality of this theory is tested by the seepage experiments of natural undisturbed clay and artificial clay, and from these experiments, three beneficial conclusions are drawn: (1) The results of the pore size effect seepage theory are in good agreement with the experimental results and are better than the modified Kozeny-Carman equation; (2) The properties of the electric double layer have a certain regular influence on the seepage behavior of the clay; (3) Considering the properties of the soil pore size distribution, the results obtained by using the pore size effect theory are much closer to the experimental results than the results calculated using the average pore diameter of the clay.