Influence of the convective term in the Nernst-Planck equation on properties of ion transport through a layer of solution or membrane

The one-dimensional boundary-value problem of steady-state ion transport, which takes into account the convective component, is formulated and solved in terms of the Nernst-Planck model. This problem is investigated in connection with the diffusion layer, which is understood in a broad sense. This can be the diffusion layer as it is usually understood, i.e., located adjacent to a hydraulically permeable membrane. In another context it can be regarded as a capillary connecting two reservoirs filled with solutions of different concentration or as an uncharged macropore permeating the membrane and separating two solutions. Finally, the solution to the problem is applied to the membrane itself, which is represented as a quasi-homogeneous gel. In the latter case, a virtual electroneutral solution in local equilibrium with a small volume of membrane is considered. The problem is investigated in dimensionless form as a function of the Peclet number. It is shown that the Peclet number is numerically equal to the absolute value of the dimensionless convection velocity. The limiting current, concentration profiles, distributions of the field strength and potential, and effective transport numbers are analyzed as functions of the convective component.     

Effect of an ion-exchange filler on the deionized water quality in electrodialysis

Desalination channels, containing an inert separator and a monolayer of ionites AV-17 and KU-2 taken in various volume ratios, are studied while maintaining concentrations of all solution components invariant. It is shown that the composition of the ion-exchange filler of the desalination channel affects the rate of transport of salt ions through relevant membranes, pH, and specific resistance of desalinated solution. The behavior of membrane systems in an overlimiting state is explained by using notions about different mechanisms governing the so-called overlimiting current through anion-exchange and cation-exchange membranes     

Modification of the Material Surface by Boron Ions Based on Vacuum Arc Discharge Systems and a Planar Magnetron

Russian Physics Journal - The principle of operation and the characteristics of the experimental equipment intended for the generation of boron ion plasma and beams are presented. The equipment...     

Electroconvection in systems with heterogeneous ion-exchange membranes

The results of studying the surface morphology of heterogeneous cation-(MK-40) and anion-exchange (MA-40) membranes and calculating the structure of electroconvective vortices generated by the electric body force are shown. The body force and its distribution are estimated by taking into account real parameters of the membrane surface morphology. The calculations of vortices were carried out by solving the Navier-Stokes equation with the no-slip boundary condition and the preset body force distribution. It is shown that the body force induced by the flowing current can generate pairs of electroconvective vortices (electroosmosis of the second kind), where the size of induced vortices is comparable with the intermembrane gap in electrodialysis cells.     

Effect of alloying with boron on the phase composition and structure of Ni3Al

The structure of Ni₃Al alloy prepared by self-propagating high-temperature synthesis is studied by means of transmission electron diffraction, scanning microscopy, and X-ray structural analysis. The effect of alloying with boron on the morphology of the alloy structure is established. The grain and defect structures are investigated. The dislocation density and the internal stress are measured.     

Modifying the structural phase state of fine-grained titanium under conditions of ion irradiation

The results from quantitative investigations into the structural phase state of finely dispersed titanium before and after implantation with aluminum ions are presented. Two types of ??-Ti grains differing by phase composition, defect structure, and size are distinguished in the structure: fine grains in the range of 0.1?C0.5 ??m and coarse grains in the range of 0.5?C5 ??m. The presence of two types of TiO₂ particles in the material, i.e., rounded particles found at dislocations in the bulk of the ??-Ti grains and lamellar particles found only inside coarse ??-Ti grains, is established. The formation of the Ti₃Al phase is observed in the form of lamellar inclusions along the grain boundaries and rounded particles in triple joints. It is found that the particles of the TiAl₃ phase are isolated with a smaller volume fraction than the Ti₃Al phase; they are localized along the boundaries of coarse grains of the titanium matrix. It is established that the granular state and defect structure of the material change substantially after ion irradiation; i.e., the dislocation density and the fields of internal stresses in fine grains grow considerably, relative to the initial state of titanium.     

Effect of thermal treatment and re-doping on the volume fraction of the γ′ phase in complex-doped Ni-Al-Cr-based superalloy

Phase transformations of complex-redoped Ni-Al-Cr-based superalloys under different thermal treatment are investigated by means of diffraction electron microscopy. Alloys are obtained via directional crystallization. The factors affecting the formation of the long-range atomic order of the γ′ phase (an ordered multicomponent phase based on superstructure L1₂) are established from the experimental results. It is shown that the degree of long-range order is directly dependent on the strengthening of the superalloy.