Conductivity Of Electrolyte Solutions Research Articles

The effect of sodium silicate concentration on microstructure and corrosion properties of MAO-coated magnesium alloy AZ31 in simulated body fluid

In recent years, magnesium and its alloys are considered as biodegradable implants. However magnesium implants may rapidly corrode before the natural healing process of the tissue is completed. In this investigation, micro arc oxidation process has been studied for avoiding primary corrosion of the magnesium alloy in simulated body fluid. Anodized coating was formed on AZ31 alloy in nontoxic silicate-alkaline solution at constant current. The effects of silicate concentration and conductivity of electrolyte solution on microstructure and corrosion properties of coating were evaluated. Scanning electron microscopy showed that a thick and condensed coating is formed after enough anodizing period. Energy dispersive spectroscopy showed that Si, O and Mg are the main components of the coating. Corrosion resistance of the coated and uncoated samples was assessed using potentiodynamic polarization and electrochemical impedance spectroscopy tests in SBF at 37 °C and pH of 7.4. Maximum corrosion resistance was achieved at 30 g/L concentration of sodium silicate in anodizing solution. It was observed that further increase in silicate concentration decreased the corrosion resistance.

Fluoroethylene Carbonate and Propylene Carbonate Mixtures Based Electrolytes for Supercapacitors

The electrochemical characteristics of the electrical double layer capacitors consisting of the microporous titanium carbide derived carbon (TiC-CDC) electrode in 1M (C2H5)3CH3NBF4 solutions in 4-methyl-1,3-dioxolan-2-one, (so-called propylene carbonate (PC)), 4-fluoro-1,3-dioxalan-2-one, (so-called fluoroethylene carbonate (FEC)), and in various mixtures of named solvents like FEC:PC (1:1 volume ratio), FEC:PC (1:9) and FEC:PC (1:19) have been studied using cyclic voltammetry and electrochemical impedance spectroscopy methods. The specific capacitance, phase angle and series resistance values dependent on the solvent system used and temperature applied (from -45 ºC to 90 ºC) have been established. The region of ideal polarizability ΔE ≥ 3.0V has been demonstrated for TiC-CDC electrodes in all electrolytes and at temperatures investigated, except at T ≥ 90 ºC. Specific conductivity and viscosity values have been obtained and correlated with electrochemistry data. The limiting capacitance, the characteristic time constant and complex power values depend noticeably on the solvent used for preparation of electrolyte, i.e. on the viscosity and specific conductivity of electrolyte solution used.

Supercapacitors Based on Propylene Carbonate with Small Addition of Different Sulfur Containing Organic Solvents

The electrochemical characteristics of electrical double layer capacitors consisting of the mainly microporous titanium carbide derived carbon (TiC-CDC) electrodes in 1 M (C2H5)3CH3NBF4 solutions in 4-methyl-1,3-dioxolan-2-one, (propylene carbonate (PC)) and mixtures of PC with diethyl sulfite (DES) or 2-oxo-1,3,2-dioxathiane (i.e., 1,3-propylene sulfite, (PS)) at different volume ratios have been studied using cyclic voltammetry, electrochemical impedance spectroscopy, constant current charge/discharge and constant power methods. The specific capacitance, phase angle and other values dependent on the solvent system used and temperature applied (from −45°C to 60°C) have been established. The region of ideal polarizability ΔE ≥ 2.7 V has been demonstrated for TiC-CDC electrodes in all mixed non-aqueous electrolytes and at temperatures investigated. Specific conductivity values have been obtained and correlated with the electrochemistry data. The limiting capacitance, the characteristic time constant and complex power and energy values calculated depend noticeably on the solvent mixture used, i.e. on the specific conductivity of electrolyte solution.

The effect of magnetic field on electrochemically deposited calcium phosphate/collagen coatings.

Nanostructured calcium phosphate/collagen (CaP/COL) coatings were deposited on the carbon/carbon (C/C) composites through electrochemical deposition (ECD) under magnetic field. The effect of magnetic fields with different orientations on the morphology and composition was investigated. Both the morphology and composition of the coatings could be altered by superimposed magnetic field. Under zero magnetic field and magnetic field, three-dimensional network structure consisting of collagen fibers and CaP were formed on the C/C substrate. The applied magnetic field in the electric field helped to form nanostructured and plate-like CaP on collagen fibers. For the ECD under magnetic field, the Ca/P molar ratio of the coatings was lower than the one under B=0. This may be contributed to the decreased electrical resistance or the increased electrical conductivity of electrolyte solutions under magnetic field. The nanosized CaP/COL coatings exhibited the similar morphology to the human bone and could present excellent cell bioactivity and osteoblast functions.

Electrophysical properties of latent tracks of heavy ions in polymers

Poly(ethylene terephthalate) films irradiated by high-energy ions without additional etching have been studied. It has been shown that tracks of heavy high-energy ions in poly(ethylene terephthalate) may be considered to be single through capillaries suitable for studying electrophysical properties. It has been revealed that the surface electrical conductivities of electrolyte solutions (KCl, LiCl, MgCl2, and BaCl2) in the tracks of nonetched membranes are substantially higher, while the surface charges are noticeably lower, than those of etched membranes.

On the Influence of Molecular Structure on the Conductivity of Electrolyte Solutions – Sodium Chloride in Dioxane–Water Mixtures

AbstractTheoretical calculations of the conductivity of sodium chloride in water+1,4-dioxane mixtures are presented and compared with experimental measurements. The method of direct correlation force in the framework of the interionic theory is used for the calculation of transport properties in connection with the associative mean spherical approximation (AMSA). The effective interactions between ions in solutions are derived with the help of Monte Carlo calculations on the Born–Oppenheimer level. This work is based on earlier studies on structure of dioxane+water mixtures and the solvation of ions in it.

On the influence of molecular structure on the conductivity of electrolyte solutions - sodium nitrate in water

Theoretical calculations of the conductivity of sodium nitrate in water are presented and compared with experimental measurements. The method of direct correlation force in the framework of the interionic theory is used for the calculation of transport properties in connection with the associative mean spherical approximation (AMSA). The effective interactions between ions in solutions are derived with the help of Monte Carlo and Molecular Dynamics calculations on the Born-Oppenheimer level. This work is based on earlier theoretical and experimental studies of the structure of concentrated aqueous sodium nitrate solutions.

Fluoroethylene Carbonate as Co-Solvent for Propylene Carbonate Based Electrical Double Layer Capacitors

The electrochemical characteristics of the electrical double layer capacitors consisting of the microporous titanium carbide derived carbon (TiC-CDC) electrode in 1M (C2H5)3CH3NBF4 solutions in 4-methyl-1,3-dioxolan-2-one, (so-called propylene carbonate (PC)), 4-fluoro-1,3-dioxalan-2-one, (so-called fluoroethylene carbonate (FEC)), and in various mixtures of named solvents like FEC:PC (1:1 volume ratio), FEC:PC (1:9) and FEC:PC (1:19) have been studied using cyclic voltammetry and electrochemical impedance spectroscopy methods. The specific capacitance, phase angle and series resistance values dependent on the solvent system used and temperature applied (from −45°C to 90°C) have been established. The region of ideal polarizability ΔE ≥ 3.0 V has been demonstrated for TiC-CDC electrodes in all electrolytes and at temperatures investigated, except at T ≥ 90°C. Specific conductivity and viscosity values have been obtained and correlated with electrochemistry data. The limiting capacitance, the characteristic time constant and complex power values depend noticeably on the solvent used for preparation of electrolyte, i.e. on the viscosity and specific conductivity of electrolyte solution used.

Dynamic mechanism of equivalent conductivity minimum of electrolyte solution

The theory on electric conductivity of electrolyte solutions we have developed [T. Yamaguchi, T. Matsuoka, and S. Koda, J. Chem. Phys. 127, 064508 (2007)] is applied to a model electrolyte solution that shows a minimum of equivalent conductivity as the function of concentration [T. Yamaguchi, T. Akatsuka, and S. Koda, J. Chem. Phys. 134, 244506 (2011)]. The theory succeeds in reproducing the equivalent conductivity minimum, whereas the mode-coupling theory (MCT) underestimates the conductivity in the low-concentration regime. The theory can also reproduce the decrease in the relaxation time of conductivity with increasing the concentration we have demonstrated with a Brownian dynamics simulation. A detailed analysis shows that the relaxation of the conductivity occurs through two processes. The faster one corresponds to the collision between a cation and an anion, and the slower one does to the polarization of the ionic atmosphere. The increase in the equivalent conductivity with concentration is attributed to the decrease in the effect of the ionic atmosphere, which is in turn explained by the fact that the counter ion cannot penetrate into the repulsive core when the Debye screening length is compatible or smaller than the ionic diameter. The same mechanism is also observed in MCT calculation with static structure factor determined by mean-spherical approximation.

Research on the Impact of Different VG on Electrokinetic Removal of Heavy Metal Wastes

This paper aims to investigate the effects of different VG (voltage gradient) on electrokinetic removal technology, and examine electrode pH, electric conductivity, voltage drop in the sample, electric current, and the electroosmotic flow. It is indicated that with the increase of VG, the electrolytic reaction rate accelerates during the electric removal experiment, which has affected both system current and the pH value & electric conductivity of electrolyte solutions. The higher VG is, the faster the electrolyte solution pH varies；the higher VG is, the faster the electric conductivity changes. Meanwhile the magnitude of electroosmotic flow increases with the increase of the VG.

Fabrication and electrochemical properties of polymer bilayered membranes

In this paper we report on a fabrication method of the “diode-like” polymer bilayered membranes that possess asymmetry of conductivity in electrolyte solutions—a rectification effect similar to that of a p–n junction in semiconductors. To produce membranes with the “diode-like” properties, a thin semipermeable polymer layer formed by plasma polymerization of organic compounds was deposited on one side of a porous substrate, where the substrate was a poly(ethylene terephthalate) track membrane. Pyrrole, thiophene, acetylene and 1,1,1,2-tetrafluoroethane were used as monomers to obtain the polymer layers on the membrane surface.

Structure and electrochemical properties of polymeric composite membranes with a selective layer

The structure and electrochemical properties of polyethylene terephthalate track-etched membranes were studied. The membranes were covered with a solution of a styrene-butylmethacrylate copolymer on one side. The formation of a selective layer of copolymer in the pores of the starting membranes led to composite membranes characterized by asymmetric conductivity in electrolyte solutions—a rectification effect similar to the p-n transition in semiconductors. The asymmetry resulted from a considerable decrease in the pore diameter in the deposited copolymer layer, changing the pore geometry, and was also due to the existence of an interface in the pores between the starting membrane and the copolymer layer, having different levels of hydrophilicity.

A parametric study of AC electrothermal flow in microchannels with asymmetrical interdigitated electrodes

In this study, the AC electrothermal (ACET) flow in a microchannel with asymmetrical planar electrode pairs, in the same configuration as an AC electroosmosis (ACEO) pump, is studied numerically. The electrical, temperature and velocity fields in the microchannel are obtained by solving the coupled electrical, momentum and energy equations. The effects of electrode size, gap and length ratios, electrical conductivity of electrolyte solution, thermal conductivity of microchannel base material, as well as voltage and the frequency of AC on ACET flow are investigated in details. It is found that in the operating frequency range of the ACEO pump, i.e. 100 Hz–100 kHz, the velocity of the ACET flow is frequency-independent and moves in the same direction as the ACEO flow, and effects of electrode size, gap and length ratios on flow velocity have the same trend as the ACEO flow. Because the ACET flow velocity is proportional to electrical conductivities of electrolyte solution linearly and to the fourth power of the applied voltage, while the ACEO flow velocity decreases with the increase of electrical conductivity of the electrolyte solution and is only proportional to the square of applied voltage, therefore the ACET flow should not be neglected in an ACEO pump for the cases of high conductivity of electrolyte solution and relatively high AC voltage where ACEO and ACET effects are comparable.

Surface-induced electrolytic dissociation of oxalic and phosphoric acid in mixed alcohol–water solvents

The electric conductance of solutions of oxalic, phosphoric and sulfuric acid (up to 0.025 M) in ethanol, methanol, and mixed alcohol–water solvents has been studied in the presence and absence of TiO 2 (1–10% by mass). TiO 2 enhanced the conductance of solutions of oxalic and phosphoric acid in anhydrous alcohol and in alcohol-rich mixed solvents. In water-rich mixed solvents “normal” behavior was observed, that is, TiO 2 depressed the conductance of electrolyte solutions. The enhanced conductance is interpreted in terms of surface-induced electrolytic dissociation. In nonaqueous solvents, oxalic and phosphoric acid occur chiefly in molecular form, even in very dilute solutions. TiO 2 binds the hydrogen oxalate or dihydrogen phosphate anions (which originate from neutral acid molecules) and the protons remain in solution in form of solvated cations. The lyonium cations have a substantially higher molar conductance than other ions due to the Grotthuss mechanism. This is why the enhancement of conductance is more substantial in solutions of weak acids than in solutions of other electrolytes.

Daniel Berthelot. Part I. Contribution to thermodynamics

Daniel Berthelot (1865-1927) did fundamental research on the conductivity of electrolyte solutions, thermodynamics, pyrometry, and photochemistry. In thermodynamics he proved that the limiting density of gases can be used to determine their atomic and molecular weights; he provided the first proof that the principle of corresponding states requires a third parameter and discovered several thermodynamic loci that could be used for this purpose. He improved the van der Waals equation of state by making the term a/v2 a function of the temperature and developed a new equation of state that may be considered the basis of the Redlich-Kwong equation of state.

Determination of phase transition points of ionic liquids by combination of thermal analysis and conductivity measurements at very low heating and cooling rates

The determination of phase transition points of nine different ionic liquids (ILs) was performed by thermal analysis with simultaneous recording of conductivity. Conductivity of electrolyte solutions and ILs drastically changes during phase transitions and thus is an additional and very sensitive indicator for measuring phase transition points. Evaluation of temperature–time functions and conductivity–time functions with our computer-coupled automated equipment enabled the determination of melting temperatures with high accuracy and reliability. This claim is based on large samples, low temperature change rates and by regularly repeated measurements, i.e. at least seven measurements per IL. The melting temperatures of 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate, 1-butyl-1-methylpyrrolidinium tris(penta-fluoroethyl)trifluorophosphate, and 1-methyl-3-propylimidazolium iodide were, to our knowledge, determined for the first time. The melting temperatures of the other 1-butyl-1-methylpyrrolidinium-, 1-ethyl-3-methylimidazolium-, 1-hexyl-3-methylimidazolium-, and trimethylsulfonium-based ILs showed either a very good accordance with values published in literature or were distinctly higher.

Properties of poly(ethylene terephthalate) track membranes with a polymer layer obtained by plasma polymerization of pyrrole vapors

The structure and the charge transport properties of poly(ethylene terephthalate) track membrane modified by pyrrole plasma were studied. It was found that polymer deposition on the surface of a track membrane via plasma polymerization of pyrrole results in the creation of composite nanomembranes that, in the case of the formation of a semipermeable layer, possess asymmetric conductivity in electrolyte solutions – a rectification effect similar to that of a p–n junction in semiconductors. It is caused by presence in the membranes of two layers with different functional groups and also by the pore geometry. Such membranes can be used to create chemical and biochemical sensors.

A theoretical study on the frequency-dependent electric conductivity of electrolyte solutions. II. Effect of hydrodynamic interaction

The theory on the frequency-dependent electric conductivity of electrolyte solutions proposed previously by Yamaguchi et al. [J. Chem. Phys. 127, 234501 (2007)] is extended to include the hydrodynamic interaction between ions. The theory is applied to the aqueous solution of NaCl and the concentration dependence of the conductivity agrees well with that determined by experiments. The effects of the hydrodynamic and relaxation effects are highly nonadditive in the concentrated solution, because the hydrodynamic interaction between ions affects the time-dependent response of the ionic atmosphere. The decrease in the electric conductivity is divided into the contributions of ion pair distribution at various distances. The long-range ionic atmosphere plays a major role at the concentration as low as 0.01 mol/kg, whereas the contribution of the contact ion pair region is important at 1 mol/kg. The magnitude of the contribution of the contact ion pair region is scarcely dependent on the presence of the hydrodynamic interaction. The transport number of cation is calculated to be a decreasing function of concentration as is observed in experiments.

A theoretical study on the frequency-dependent electric conductivity of electrolyte solutions

The theory on the ultrasonic absorption of electrolyte solutions we have proposed previously [T. Yamaguchi et al., J. Chem. Phys. 126, 144505 (2007)] is extended to calculate the frequency-dependent electric conductivity of the solution. The ionic contribution of the dielectric relaxation spectrum is obtained at the same time. The theory is able to handle the contributions of both the ion-pair dynamics and the relaxation of ionic atmosphere, as is the case of ultrasonic absorption. The effect of the barrier height between the contact and solvent-separated ion pairs is investigated in detail. It is clarified that the competition between the dissociation and reorientational relaxation rates of the contact ion pair is an important factor for the ion pair to be regarded as the ion pair in terms of ionic conductivity.

Revisit of Joule heating in CE: The contribution of surface conductance

We present in this short communication the true form of Joule heating in CE which considers the contribution of surface conductance. This increased conductivity of electrolyte solution within electrical double layer has never been discussed in previous studies. The resultant intensive heat generation near the capillary wall is demonstrated using numerical simulation to produce not a locally strong temperature rise, but an additional temperature elevation in the whole solution compared to the model neglecting surface conductance. The latter effect is, however, negligible in typical CE while it might become significant in very small channels.