Separation of calcium and magnesium solvated cations under the action of external periodic electric field on moving solution

The experimental results on the excitation of the phenomenon of selective drift of solvated ions under the action of an external “asymmetric” electric field on a circulating solution of calcium and magnesium chloride salts in polar liquid dielectric, i.e., in water, are presented. The objective of the experiments was the determination of the features of the effect of the field frequency and field strength amplitude on the phenomenon excitation, and the study of operating characteristics of the experimental device, i.e., the separation cell. The dependences of the efficiency of solvated cation separation on the external field frequency and the phenomenon excitation threshold in the field strength in the separation cell are determined.     

The structure and radiophysical properties of solutions of salts in liquid polar dielectrics

Solutions of metal salts in liquid polar dielectrics are treated as systems of interacting charged particles, that is, cations, anions, and water molecules around cations and anions. The size of solvated ion-clusters is estimated in the approximation of the existence of a self-consistent field in solution volume. The behavior of solutions under the action of external electric field and electromagnetic wave is analyzed. The condition under which a solution of a salt in a liquid polar dielectric reflects electromagnetic waves of a certain frequency is found.     

Sizes of solvated ion-clusters in salt solutions

Sizes of solvated ion-clusters were estimated in the approximation of oriented association of polarized solvent molecules around ions and in the approximation of the existence of a self-consistent field in the solution volume. It was shown that the salt concentration in the solution controls the applicability of this or that approximation. The cluster size strongly depends on the concentration at its high values. An increase in the concentration causes an increase in the frequency of the maximum manifestation of the effect of electroinduced selective drift of solvated ions.     

Coexistence of the relaxor-like and ferroelectric behavior in K1-xLixTaO3

ABSTRACT

The results of low-temperature linear and nonlinear susceptibilities, polarization measurements and the dc electric field dependence of the dielectric properties of the lithium-doped potassium tantalate K_1-xLi_xTaO₃, x = 0.034 (KLT-3.4%Li) solid solution are presented. The coexistence of the relaxor-like and ferroelectric behavior and different mechanisms leading to either of them are discussed. The observed ferroelectric phase transition is of the first-order type with temperature hysteresis. This transition is due to the off-center motions of Ta ions in the octahedral environment of oxygen ions. Clusters of Li⁺ ions produce a relaxor-like behavior and random electric field. This field reduces the depolarization field and allows off-center motions of Ta ions and an appearance of spontaneous polarization.     

Bifurcation resulting in self-focusing of the electric field near the poles of a conducting microgranule

The experimentally found phenomenon of self-focusing of an electric field and the concentration of ions near the poles of an ion-selective granule in an electrolyte solution under the action of an external electric field is theoretically justified. An asymptotic solution of the problem is obtained, and it is shown that the solution found loses stability at high field strengths and, after the corresponding bifurcation, passes into a new solution in which there is a sharp local amplification of the electric field and the ion concentration.     

Influence of unstable valence of cerium ions on the crystal field in ReNi compounds

To examine the effect of hybridization of 4f electrons with conduction electrons on the crystal field potential using neutron spectroscopy, we studied the effects of the crystal electric field (CEF) in intermetallic compounds of the type ReNi, in which chemical substitution is followed by a transition of the cerium ions from an intermediate valence state to the Kondo state. Measurements were performed both on cerium ions in the compounds Ce_1−x La_xNi (x=0.5, 0.8), where they have a whole-number population of the 4f shell, and on the paramagnetic impurity ion Nd in the series of compounds Re_1−x Nd_xNi (Re=Ce, La, Y), in which the cerium ions are found either in an intermediate valence state or in the Kondo state. From the neutron inelastic magnetic scattering spectra on Nd ions, we have reconstructed the crystal field parameters in ReNi compounds and calculated the CEF level diagram of Ce ions in these compounds as functions of the interion distances Re-Ni. The results of our calculations are in good agreement with the experimentally determined splitting diagram of the ground-state multiplet of the Ce ions. We have determined that as the degree of hybridization with the conduction electrons grows the CEF potential varies considerably and the effective splitting of the 4f shell of the cerium ions increases. The estimated energy scale of the splitting of the ground-state multiplet of the Ce³⁺ ions in the ReNi CEF (Δ_CEF∼15 meV) turns out to be commensurate with the Kondo temperature (T _K ;140 K for CeNi. Analysis indicates that the CEF potential has a substantial effect on the formation of the valence-unstable ground state of the f shell in this compound. Zh. éksp. Teor. Fiz. 113, 1731–1747 (May 1998)     

Helmholtz free energy of a multilayer system of highly charged plates immersed in an electrolyte

The Helmholtz free energy of highly charged plates immersed in an electrolyte solution in a finite container is investigated using mean field theory. Exact solutions of the Poisson-Boltzmann equation under Dirichlet and Neumann boundary conditions lead to analytical expressions for the free energies. Adiabatic potentials of the charged plates, which are derived from the free energy, have long-range weak attractive parts and medium-range strong repulsive parts, irrespective of the type of boundary conditions. The repulsion results mainly from the osmotic pressure of the excess ions trapped between the plates by the large surface charges and the attraction arises essentially from an electric pull from the intermediate cloud of excess counterions shared by the plates.     

高压电场浓缩液体物料技术的研究及进展

高压电场干燥技术是一种全新的干燥技术 .文章对高压电场浓缩液体的机理进行了探讨 ,认为是内部离子注入、非均匀电场和外部离子风吹动三合一的结果 .通过以自来水、葡萄糖酸钠溶液等液体物料为样品 ,首次在高压电场下进行浓缩实验 ,表明高压电场能够加速水分子的脱出 .文章对当前的研究状况进行了介绍     

Dipole moments of molecules solvated in helium nanodroplets

Stark spectra are reported for hydrogen cyanide and cyanoacetylene solvated in helium nanodroplets. The goal of this study is to understand the influence of the helium solvent on measurements of the permanent electric dipole moment of a molecule. We find that the dipole moments of the helium solvated molecules, calculated assuming the electric field is the same as in vacuum, are slightly smaller than the well-known gas-phase dipole moments of HCN and HCCCN. A simple elliptical cavity model quantitatively accounts for this difference, which arises from the dipole-induced polarization of the helium.     

Effect of an electric field on the emission of sodium ions from the surface of NaAu alloy

We investigate how an electric field affects the desorption of sodium ions from the surface of a NaAu semiconductor film formed on a gold substrate. It is shown that an external electric field affects the equilibrium concentrations for sodium cations in the near-surface area and their dilution in a Na _x Au _y film.     

Confinement physics for thermal, neutral, high-charge-state plasmas in nested-well solenoidal traps

A theoretical study is presented which indicates that it is possible to confine a neutral plasma using static electric and solenoidal magnetic fields. The plasma consists of equal temperature electrons and highly stripped ions. The solenoidal magnetic field provides radial confinement, while the electric field, which produces an axial nested-well potential profile, provides axial confinement. A self-consistent, multidimensional numerical solution for the electric potential is obtained, and a fully kinetic theoretical treatment on axial transport is used to determine an axial confinement time scale. The effect on confinement of the presence of a radial electric field is explored with the use of ion trajectory calculations. A thermal, neutral, high-charge-state plasma confined in a nested-well trap opens new possibilities for fundamental studies on plasma recombination and cross-field transport processes under highly controlled conditions.     

On the Velocity Distribution Function of Light Ions in Heavy Gases in an Electric Field

The special properties presented by the Boltzmann collision operator in the case of an induced-dipole interaction (Maxwellian interaction) between ions and neutrals are exploited to obtain in such case a proper solution of the Boltzmann equation for light ions in heavy gases in an electric field. Meanwhile it is proved that consideration of more than two terms of the spherical harmonic expansion of the ion velocity distribution requires to improve the usual accuracy of the terms deriving from the collision integral; vice versa, the improvement of the accuracy of the collision terms requires to retain more than two terms of the spherical harmonic expansion. The consistency of our procedure and results in the approximation neglecting the square of the ion-neutral mass ratio with respect to unity is discussed. Finally, the most significant velocity averages are calculated on the basis of the obtained ion distribution. In the limit of the above approximation they are shown to agree with Wannier's results.     

Probe Measurements in Electronegative Plasmas: Modeling the Perturbative Effects of the Probe‐Holder

A basic property of an electronegative plasma is its separation into two distinct regions: an ion‐ion region far from boundaries, where the densities of positive and negative ions are higher then electron density, and a near‐boundary electron‐ion region, where negative ions have practically negligible density. This is due to the influence of the ambipolar electric field, which depends on electron (not negative ion) plasma parameters. This electric field “holds off” negative ions from the boundary, as the ions have lower mobility and temperature compared to the electrons. Therefore, negative ions will be repelled by any object inserted into the plasma. This can lead to errors in measurements of negative ion and electron parameters by any invasive method. Numerical modeling of electric probes in an argon‐oxygen plasma clearly demonstrates possible errors of direct measurements of negative ion probe current. This can also affect results from the photo‐detachment method and direct measurements of negative ion energy distribution (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

In situ TEM studies of oxygen vacancy migration for electrically induced resistance change effect in cerium oxides

Oxide materials with resistance hysteresis are very promising for next generation memory devices. However, the microscopic dynamic process of the resistance change is still elusive. Here, we use in situ transmission electron microscopy method to study the role of oxygen vacancies for the resistance switching effect in cerium oxides. The structure change during oxygen vacancy migration in CeO₂ induced by electric field was in situ imaged inside high-resolution transmission electron microscope, which gives a direct evidence for oxygen migration mechanism for the microscopic origin of resistance change effect in CeO₂. Our results have implications for understanding the nature of resistance change in metal oxides with mixed valence cations, such as fluorite, rutile and perovskite oxides.     

Planar waveguides in multicomponent glasses fabricated by field-driven differential drift of cations

The fabrication of planar waveguides by a constant-current thermal poling procedure in multicomponent glasses rich in alkali or alkaline earth ions is described. Near the anode, the dc electric field applied to the substrate separates the mobile cations into regions according to their mobility. Each region presents a different refractive index, allowing a waveguide to be formed. This method produces waveguides with an index increase greater than 10(-2) in soda-lime glass with no external ion source, and the waveguides are buried beneath the substrate surface without an additional step.     

Electron paramagnetic resonance of Ce3+ ions in lead thiogallate single crystals

The results of electron paramagnetic resonance (EPR) studies of Ce³⁺ impurity ions in single crystals of lead thiogallate PbGa₂S₄ have been reported. The Ce³⁺ ions substitute for Pb²⁺ ions in the crystal lattice of PbGa₂S₄. A number of paramagnetic cerium centers in lead thiogallate have been observed. The spectra are described by the spin Hamiltonian of rhombic symmetry with the effective spin S = 1/2. The g factors of the main cerium centers have been determined. A large number of paramagnetic centers are due to both nonequivalent positions of lead and local charge compensation under the substitution Ce³⁺ ?? Pb²⁺.     

Radial Distributions of Dusty Plasma Parameters in a DC Glow Discharge

A non‐stationary non‐local kinetic model for radial distributions of dusty plasma parameters based on the solution of Boltzmann equation for electron energy distribution function is presented. Electrons and ions production in ionizing collisions and their recombination on dust particle surface were taken into account. The drift‐diffusion approximation for ions was used. To obtain the self‐consistent radial distribution of electric potential the Poisson equation was used. It is shown that at high dust particle density the recombination of electrons and ions can exceed their production in ionization collisions in the region of dusty cloud. In this case the non‐monotonous radial distribution of the electric field is formed, the radial electric field becomes reversed and the radial electron and ion fluxes change their direction toward the center of the tube (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Theoretical analysis of transcranial Hall-effect stimulation based on passive cable model

Transcranial Hall-effect stimulation(THS) is a new stimulation method in which an ultrasonic wave in a static magnetic field generates an electric field in an area of interest such as in the brain to modulate neuronal activities. However, the biophysical basis of simulating the neurons remains unknown. To address this problem, we perform a theoretical analysis based on a passive cable model to investigate the THS mechanism of neurons. Nerve tissues are conductive; an ultrasonic wave can move ions embedded in the tissue in a static magnetic field to generate an electric field(due to Lorentz force).In this study, a simulation model for an ultrasonically induced electric field in a static magnetic field is derived. Then,based on the passive cable model, the analytical solution for the voltage distribution in a nerve tissue is determined. The simulation results showthat THS can generate a voltage to stimulate neurons. Because the THS method possesses a higher spatial resolution and a deeper penetration depth, it shows promise as a tool for treating or rehabilitating neuropsychiatric disorders.     

Production of cerium zinc molybdate nano pigment by innovative ultrasound assisted approach

Ultrasound assisted synthesis of yellow rare earth cerium zinc molybdate anticorrosion nanopigment is presented. This new class of pigment is eco-friendly alternatives to lead, cadmium and chromium pigment as these pigments contains carcinogenic species like Cr⁶⁺ which is responsible for human disease. The synthesis of nanosized cerium zinc molybdate was carried out using cerium nitrate, sodium zinc molybdate as a precursor materials by conventional and ultrasound assisted chemical precipitation method without addition of emulsification agent. XRD, FTIR and elemental analysis confirm the formation of cerium zinc molybdate nanoparticles. The conductivity results indicate that conventional synthesis takes longer time, while in sonochemical technique (US), reaction completes within short period of time. Improved solute transfer rate, rapid nucleation, and formation of large number of nuclei are attributed to presence of cavitation. Saturation of the Ce³⁺ ions reaches earlier in case of sonochemical technique which restricts the growth of particles hence smaller size is obtained. The crystallite size of cerium zinc molybdate was found to be 27 nm from XRD analysis.     

Self-consistent hybrid model for a stratified positive column of a low pressure glow discharge

The stratification of a positive column of a low-pressure glow discharge in inert gases has been studied with the help of a self-consistent hybrid model. The model is based on the solution of a nonlocal kinetic Boltzmann equation for the electron distribution function, a nonstationary drift-diffusion equation for the ions, and the Poisson equation for the electric field. Spatial electron and ion density distributions and the electric field distribution in the positive column were obtained. The converged solution of the model gives a self-consistent resonant strata length L and the value and the form of the modulated plasma parameters. An unexpected surprising result was obtained: for a given potential drop in the positive column of a low-pressure glow discharge, a self-consistent spatially modulated striation-like electric field does not lead to the resonant increasing of the ionization frequencies in the discharge as compared with a constant electric field with the same potential drop. Usually, it was assumed that, in spatially modulated field distributions, all the parameters in a striated plasma will be more pronounced and have a resonant form. The text was submitted by the authors in English.