Influence Of Ion Concentration Research Articles

Assessing the Mechanical-to-Electrical Energy Conversion Process of a Droplet Sliding on the Poly(tetrafluoroethylene) Surface.

Utilizing moving droplets to generate electricity has garnered significant attention due to its high output voltage and power. However, the understanding of energy dissipation and conversion processes during droplet movement remains limited, hindering the development of effective ways to further enhance the device's performance. In this study, we developed a method to simultaneously evaluate the input mechanical energy and output electrical energy while droplets slide on a poly(tetrafluoroethylene) (PTFE) surface to assess the energy conversion process. The influences of ion concentration, droplet volume, and contact area with PTFE on the energy conversion efficiency were investigated, suggesting optimized parameters. Moreover, by introduction of an asymmetric electric field on the PTFE surface, the input mechanical energy can be significantly reduced. In combination with the enhanced electrical output originating from improved surface charge density, the energy conversion efficiency is improved by an order of magnitude from 0.61 to 9.08%. These results shed light on strategies to improve device performance based on moving droplets.

Theoretical investigation of electroviscous flows in hydrophilic slit nanopores: Effects of ion concentration and pore size

Nanopores with various shapes are well developed in unconventional reservoirs, and the transport phenomena of solutions in these reservoir rocks are ubiquitous but have not yet been fully understood. This article investigates the flow characteristics of solutions in hydrophilic slit nanopores through the combination of a modified Poisson–Boltzmann (MPB) model and the modified Navier–Stokes (NS) equation. To account for the nanoconfinement effects on ion concentration and fluid viscosity, an electrochemical potential term is used in the MPB model and a varying viscosity model (VVM) is introduced in the NS equation. The model rationality is first confirmed, and then the influences of ion concentration and pore size on the transport capacities of solutions in nanopores are illuminated. In addition, the hydrodynamic features of liquids in nanopores and the limitations of this coupled model are discussed as well. The results show that the dimensionless apparent permeability of the slit increases with an increase in ion concentration and pore size. The relative contributions of the electroviscous effect (EVE) and VVM to the total flow resistance reveal different varying trends as ion concentration or pore size increases, which is greatly related to the surface charge density and the sign of the charged wall. Additionally, although the effects of EVE and VVM resulting from the nanoconfinement are considered, average velocities of fluids in nanopores exhibit a linear correlation with the pressure gradient, which cannot be used to explain the nonlinear flow mechanism occurring in tight reservoirs. Furthermore, we also compare the velocity difference between the classical PB and MPB models. We hope that the findings in this work can help improve our understanding of the characteristics of liquid flow in tight reservoirs and provide vital practical implications for diverse engineering applications.

Electrochemical impedance spectroscopy of enhanced layered nanocomposite ion exchange membranes

This work presents the enhancement of Cl−/SO42− mono-selectivity of layered nanocomposite anion exchange membranes (AEMs) and the mechanism that supports this improvement. These nanocomposite membranes are based on commercial polyethylene AEMs and a nanocomposite negative thin layer composed of sulfonated poly (2,6-dimethyl-1,4-phenylene oxide) and a functionalized nanomaterial, Fe2O3−SO42− nanoparticles or oxidized multi-walled carbon nanotubes CNTs-COO−. The mechanism for monovalent selectivity was confirmed by characterizing nanocomposite membranes and commercial heterogeneous ion exchange membranes (IEMs) using ζ-potential and electrochemical impedance spectroscopy (EIS). ζ-potential measurements confirmed the modification of the charge of surface of the membrane after being coated with the nanocomposite layer. EIS measurements showed a totally different electrical performance between layered nanocomposite membranes and commercial IEMs. The electrical data from EIS was fitted to a Maxwell-Wagner model providing an equivalent electric circuit (EEC) for each membrane. The observed differences in ECC were related to the structural differences of the membranes. A physical explanation of the phenomena that caused these differences is provided. The influence of ion concentration on EIS measurements was also studied. To the best of our knowledge, this is the first time that an ECC related to the structure of advanced layered IEMs is proposed.

The crucial role of cadmium acetate-induced conformational restriction in microscopic structure and stability of polystyrene-block-polyvinyl pyridine thin films

Block copolymers (BCPs) with inorganic components gained ground as a useful material with a broad range of applications. It is still a matter of discussion what influences of inorganic components on block copolymer structures. In this work we present the critical role of conformationally restricted effect by cadmium acetate (Cd(Ac)2) on microscopic structure and film stability of polystyrene-block-poly(2-vinylpyridine) (S2VP) and polystyrene-block-poly(4-vinylpyridine) (S4VP). The influence of ion concentration, coordination type, as well as physical ageing on micelles and films were investigated and discussed. It was revealed that the coordination type played a critical role in both micelle and thin film morphology. As ion concentration increased, the intermolecular coordination between Cd(Ac)2 and S4VP led to significant micelle coalescence and a decrease of film stability. However, intramolecular coordination between Cd(Ac)2 and S2VP only affected the micelle size. The film prepared from a physically aged low Cd2+ concentration S4VP solution formed mesoporous structure. AFM and GISAXS results showed excellent lateral ordering within mesoporous films. These results suggest a facile procedure for the preparation of block copolymer mesoporous structures which can provide the base for highly functional materials such as highly efficient catalysts, photonic devices, and photovoltaic films.

Simple and reusable picoinjector for liquid delivery via nanofluidics approach

Precise control of sample volume is one of the most important functions in lab-on-a-chip (LOC) systems, especially for chemical and biological reactions. The common approach used for liquid delivery involves the employment of capillaries and microstructures for generating a droplet which has a volume in the nanoliter or picoliter range. Here, we report a novel approach for constructing a picoinjector which is based on well-controlled electroosmotic (EO) flow to electrokinetically drive sample solutions. This picoinjector comprises an array of interconnected nanochannels for liquid delivery. Such technique for liquid delivery has the advantages of well-controlled sample volume and reusable nanofluidic chip, and it was reported for the first time. In the study of the pumping process for this picoinjector, the EO flow rate was determined by the intensity of the fluorescent probe. The influence of ion concentration in electrolyte solutions over the EO flow rate was also investigated and discussed. The application of this EO-driven picoinjector for chemical reactions was demonstrated by the reaction between Fluo-4 and calcium chloride with the reaction cycle controlled by the applied square waves of different duty cycles. The precision of our device can reach down to picoliter per second, which is much smaller than that of most existing technologies. This new approach, thus, opens further possibilities of adopting nanofluidics for well-controlled chemical reactions with particular applications in nanoparticle synthesis, bimolecular synthesis, drug delivery, and diagnostic testing.PACS85.85.+ j; 87.15.hj; 82.39.Wj

The influence of ion concentrations on the dynamic behavior of the Hodgkin-Huxley model-based cortical network.

Action potentials (APs) in the form of very short pulses arise when the cell is excited by any internal or external stimulus exceeding the critical threshold of the membrane. During AP generation, the membrane potential completes its natural cycle through typical phases that can be formatted by ion channels, gates and ion concentrations, as well as the synaptic excitation rate. On the basis of the Hodgkin-Huxley cell model, a cortical network consistent with the real anatomic structure is realized with randomly interrelated small population of neurons to simulate a cerebral cortex segment. Using this model, we investigated the effects of Na(+) and K(+) ion concentrations on the outcome of this network in terms of regularity, phase locking, and synchronization. The results suggested that Na(+) concentration does slightly affect the amplitude but not considerably affects the other parameters specified by depolarization and repolarization. K(+) concentration significantly influences the form, regularity, and synchrony of the network-generated APs. No previous study dealing directly with the effects of both Na(+) and K(+) ion concentrations on regularity and synchronization of the simulated cortical network-generated APs, allowing for the comparison of results obtained using our methods, was encountered in the literature. The results, however, were consistent with those obtained through studies concerning resonance and synchronization from another perspective and with the information revealed through physiological and pharmacological experiments concerning changing ion concentrations or blocking ion channels. Our results demonstrated that the regularity and reliability of brain functions have a strong relationship with cellular ion concentrations, and suggested the management of the dynamic behavior of the cellular network with ion concentrations.

Biomimetic construction of cellular shell by adjusting the interfacial energy

Many unicellular organisms take their outer proteinaceous and lipidic membranes or carbonhydrate-rich cell walls as a template for biomineralization to synthesize a thin mineral layer as a functional covering. In nature most cells cannot be mineralized spontaneously in the normal states. Inspired by nature, we develop cytocompatible methods for cells encapsulated inside a mineral shell, called "cellular shellization." Using Layer-by-Layer (LbL) assembly, the precipitation of calcium minerals can be induced on the yeast cell surfaces. The effects of different synthetic polyelectrolytes on the calcifications of yeast, such as interfacial energy, zeta-potential, introduction time, and the affinity of mineral phase on the yeast cell surface have been studied by using constant composition method (CC) systemically and quantitatively. The results demonstrate that the effective adsorption of polyelectrolytes with carboxyl or sulfonate-rich groups on the yeast can enhance mineralization abilities of yeast cells readily, and the factor of interfacial energy plays a key role in the superficial mineralization of the cells. Furthermore, the influences of ion concentrations, as well as titration rates on the formation of inorganic shell, have also been examined. It is found that the biomimetic shell formation on the cell can also be achieved by using an appropriate selection of titration conditions rather than the pretreatment of LbL. Thus, the control of cellular biomineralization can become more feasible. In this study, we show that adjusting the interfacial energy is the key to cellular mineralization and suggest that these biomineralization treatments of single-cell may be applied as a potential and universal approach for cell-based sensing and therapy.

Effects of ion concentration and natural organic matter on arsenic(V) removal by nanofiltration under different transmembrane pressures

The removal of As(V) from synthetic water was studied using four different nanofiltration (NF) membranes (ESNA-1-K1, NF270, ESNA-1-LF, and HODRA-CORE). The influences of ion concentration, transmembrane pressure (TMP), and the presence of natural organic matter (humic acid, HA) on the arsenic removal efficiency and permeate flux were investigated. The arsenic rejection of ESNA-1-LF was higher than those of the other membranes in all experiments (> 94%), and the HODRA-CORE membrane gave the lowest removal of arsenic (< 47%). An increase in the ion concentration in the feed solution and addition of HA decreased the arsenic rejection of the HODRA-CORE membrane. However, both increasing of the ion concentration and addition of HA made the rejection increased for the other membranes (ESNA-1-K1, NF270, and ESNA-1-LF). With increasing TMP, for all four NF membranes, increases in both arsenic rejection and permeate flux were observed. The permeate fluxes of the four NF membranes decreased to some extent after addition of HA to the solutions for operating time of 6 hr.

Mechanistic insight into the individual ionic transportation in polymer electrolytes for use in dye-sensitized solar cells

Polymer electrolytes, acting as an ionic solid-state conducting phase, have been demonstrated as promising charge carrying mediators for energy storage devices. However, the large majority of polymer electrolyte studies are focused on cation transportation and little consideration has been given to the investigation of the anion transportation mechanism. In this study we focus on the individual ionic transportation mechanisms in polymer electrolytes for potential application in dye-sensitized solar cells (DSSCs). To explore the ionic transportation mechanism, polymer electrolytes with different ion concentrations were studied. The influence of ion concentration on the structure of the polymer electrolytes was elucidated using X-ray diffraction (XRD) and Raman spectroscopy. Additionally, the temperature and composition dependence of the ionic conductivity and restricted ion diffusion coefficient of the polymer electrolytes were studied to gain an insight into the ionic transportation mechanism. The behavior of the anion transportation was further discussed via the addition of I2 into the polymer electrolytes. The results imply that the disorder and flexibility of the polymer matrix are favorable for ionic transportation, and that mass transportation can be facilitated by increasing the I2 concentration in the polymer electrolyte, which could be applied in DSSCs.

Micellar Enhanced Ultrafiltration as a Method of Removal of Chromium(III) Ions from Aqueous Solutions

This study was undertaken to check the possibility of using micellar enhanced ultrafiltration (MEUF) in the removal of chromium(III) ions from water systems. The influence of ion concentration in the feed, type of surfactant (SDS or Rofam 10), and the membrane material on separation efficiency were studied and discussed. The use of environmentally safer surfactants from renewable sources was proposed, that is, oxyethylated rape fatty acid methyl esters – trade name: Rofam 10. The results presented show the possibility of using MEUF as an effective method for removing chromium(III) ions from aqueous solutions, especially from solutions of low concentration.

Numerical investigation of gain characteristics of Er3+/Yb3+ co-doped fiber amplifiers

Inthiswork,amodelforanalyzingthegaincharacteristicsofheavilyEr 3+ /Yb 3+ co-doped compactfiber amplifier is presented. Four-level rate equations andfinite-difference beam propagation method are applied to simulate the optical field evolution along the active fiber. Based on this model, the influences of ion concentration, fiber length and pump power on the gain characteristics of Er 3+ /Yb 3+ co-doped phosphate glass fiber amplifiers are the- oretically investigated. Numerical results show that for a fiber length of 3.6cm the internal gain can reach 27.2dB with NEr = 2.6 × 10 26 ions/m 3 and NYb = 1.2 × 10 27 ions/m 3 when pumped with 224mW at 980nm. The gain per centimeter is 7.56dB/cm. The results can provide useful information to optimize the gain performance of these compact fiber

Influence of ion concentration on the kinetics of electrodialysis with bipolar membranes

This work aims at the development of a mathematical model that describes the behaviour of electrodialysis on bipolar membranes (EDBM) systems in a wide range of solute concentrations. The mathematical model based on the application of the Nernst–Planck equation, accounts for the influence of diffusion and migration phenomena, and allows quantification of their relative importance in the mass transport flux as a function of the operating conditions. In order to check the validity of the proposed model with experimental results, the obtention of hydrochloric acid and sodium hydroxide from sodium chloride was selected as a model system. The variables of the experimental design were the current density (250–1000 A m −2) and the number of cell pairs (1 and 4). The contribution of diffusion to the total ionic flux was as high as 25% depending on the concentration level of the transported species. The diffusion coefficient of sodium and chloride ions did not remain constant within the whole range of experimental variables, describing the variation by means of an exponential equation D i = D 0 exp(− τC m), that was incorporated into the mathematical model.

Controlling the transport of cations through permselective mesoporous alumina layers by manipulation of electric field and ionic strength

The electric field-driven transport of ions through supported mesoporous γ-alumina membranes was investigated. The influence of ion concentration, ion valency, pH, ionic strength, and electrolyte composition on transport behavior was determined. The permselectivity of the membrane was found to be highly dependent on the ionic strength. When the ionic strength was sufficiently low for electrical double-layer overlap to occur inside the pores, the membrane was found to be cation-permselective and the transport rate of cations could be tuned by variation of the potential difference over the membrane. The cation permselectivity is thought to be due to the adsorption of anions onto the pore walls, causing a net negative immobile surface charge density, and consequently, a positively charged mobile double layer. The transport mechanism of cations was interpreted in terms of a combination of Fick diffusion and ion migration. By variation of the potential difference over the membrane the transport of double-charged cations, Cu 2 +, could be controlled accurately, effectively resulting in on/off tunable transport. In the absence of double-layer overlap at high ionic strength, the membrane was found to be nonselective.

Ultralow and negative thermal expansion in zirconium phosphate ceramics

Compounds of the series A 5 - 4 x Zr x Zr(PO 4 ) 3 (A = Na, K; 0 ≤ x ≤ 1), A 5 - 3 x R x Zr(PO 4 ) 3 (R = Al, Fe, Dy, Ho; 0 ≤ x ≤ 1.33), and A 5 - 2 x B x Zr(PO 4 ) 3 (B = Mg, Ca, Sr; 0 ≤ x ≤ 2), have been prepared and characterised by infrared and x-ray analysis and studied by high-temperature x-ray diffractometry in the temperature range 293 - 1023 K. These compounds are members of a broad family of structural analogues NaZr 2 (PO 4 ) 3 (NZP); their crystallographic formula is (M1)(M2) 3 L 2 (PO 4 ) 3 , where L and M positions are in the framework and framework voids, respectively. The examined phosphates have rhombohedral symmetry, and belong to the R3c space group, and some belong to R32. The influence of ion concentration, occupation of crystallographic positions and their types, and also the influence of radius sizes of interstitial ions on Zr-phosphate behaviour under heating, have been established. In the studied systems, the dependence of thermal expansion on the valence of cations in the L position from +1 up to +4 (A, B, R, Zr) and, accordingly, on the charge of framework and on the degree of M position occupation, was determined. These compounds showed thermal expansion anisotropy: negative expansion along the a axis and positive expansion along the c axis. It was shown that some K - Zr-phosphates had net negative or near-zero α a v values.

Resistance to Tracking and Erosion of Silicone Rubber Material under Various Types of Precipitation

Environment stress and contaminants have become more and more severe due to the development of industry. Outdoor polymer insulating materials in use may suffer from rainwater containing various chemical contaminants so that their resistance to tracking degrades. In this paper, the tracking resistance of high-temperature vulcanized silicone rubber (HTVSR) under various types of precipitation is evaluated by the incline-plane method, using artificial rainwater as a contaminant. The influences of ion concentration, acidity, and conductivity of rainwater on the energized silicone rubber material are studied. Experimental results reported here show that the degradation of the energized material increases with the ion concentration of the rainwater; the discharge current and the erosion of material increase. The conductive ions in rainwater could induce more tracking and discharge on the energized material surface, and acidic rainwater could accelerate the electrolyte process in the materials and dissolve the inorganic filler in silicone rubber. Although silicone rubber degrades under our process of accelerated aging using artificial rainwater, the ion concentration, acidity and conductivity of actual precipitation is insufficient to exert a significant degradation effect on silicone rubber. Silicone rubber can resist the erosion of even the most corrosive rainwater and does not fail.

The influence of the alkaline earth cations, magnesium, calcium, and barium on the dissolution kinetics of quartz

This study quantifies the influence of the four major dissolved solutes found in terrestrial and marine environments on the dissolution kinetics of quartz. Dissolution rates are dependent upon the concentration and identity of alkali and alkaline earth cations in near-neutral pH solutions. We determine the effect of alkaline earth cations upon quartz reactivity by measuring dissolution rates in 0.0001–0.2 molal solutions of MgCl 2, CaCl 2, BaCl 2, LiCl, KCI, and NaCl at near-neutral pH and 200°C. The results fit a first order rate law, where dissolution rates are slowest in pure water and increase with the introduction of salts in the order: Mgt+ < Ca 2+ ≈ Li + ≈ Na + ≈ K+ < Ba 2+. The trend is consistent with previously reported lower temperature measurements of dissolution rate for amorphous silica and sources of quartz. This suggests cation-specific effects hold for multiple silica polymorphs over temperatures of 25–200°C. Combining evidence from the literature and the kinetic data presented in this study, we propose a simple model: The dissolution rate of quartz. Alkali and alkaline earth cations indirectly enhance dissolution by] modifying rates of solvent motion, exchange, or orientation at the mineral-solution interface. Rate enhancement is proportional to the concentration of ions at the surface and their solvation character. The resulting model predicts (1) the dissolution rate of quartz for a suite of cations with weak surface interactions, (2) the influence of ion concentration, (3) that the catalyzing effect of salts diminish as the concentration of silicic acid in solution increases (decreasing reaction affinity) by increasing the amount of H 4SiO 4 at the interface, (4) that electrolytes have little rate-enhancing effect on the dissolution kinetics of silicate minerals, and (5) that dissolution rates of other oxide materials containing constituents with sluggish solvent interactions are also enhanced by introduction of alkali or alkali cations. Our findings reiterate the need to understand relationships between near-surface solute/solvent properties and mineral reactivity.