Electrodeposition of metals into nanopores of templates represents a crucial area of study within the field of confinement-controlled electrochemistry. This review addresses the templated synthesis of nanocomposites (nonmetallic hard templates with one-dimensional cylindrical nanopores filled with metal or semiconductor) and single nanowires and nanotubes obtained by template dissolution. The focus is on the influence of electrochemical conditions such as electrolyte composition, electrodeposition regimes, and template characteristics on the morphological and physical properties of the resulting nanostructures. Additionally, this review introduces the theoretical modeling of mass transfer in templated electrodeposition, which is critical for understanding and optimizing the pore-filling processes and the uniformity of nanostructure formation. The potential applications of these nanostructures in fields such as electronics, optoelectronics, and catalysis are also discussed, highlighting their significant implications for advancing nanotechnology and materials science.

Templated electrodeposition is a versatile method for preparing metal nanostructures. Among the various parameters of this process, the effect of convection on the deposition process is less explored. The present work is devoted to the experimental and theoretical study of the influence of natural convection near nanoporous anodic aluminium oxide templates on the deposition of nanowires. Electrochemical deposition of copper nanowires was carried out with vertical templates parallel to the gravitational acceleration at various overpotentials. A model of nanowire electrodeposition was developed based on the Navier‒Stokes and diffusion equations. The length profiles of the nanowires, experimentally measured using scanning electron microscopy, were compared with the results of the numerical simulation. The simulation results were also compared with current-time transients recorded during metal electrodeposition into nanopores. In addition, an analytical expression has been proposed to describe the evolution of the deposition current density into nanopores under natural convection conditions.

Electrochemical machining (ECM) of the inner surface of cylindrical workpiece (WP) with an eccentric rotating cylinder tool-electrode (TE) is studied theoretically using a new mathematical model. The proposed model uses a moving coordinate system bound to the rotating WP. In this case, only the variation in the position of TE center during its orbital movement is taken into account. In addition, for convenient solution and analysis of results, the mathematical model was presented in the dimensionless form in order to reduce the number of parameters. The local one-dimensional approximation is used to calculate the distribution of the current density. It enables determining the distribution of the current density not from the solution of Laplace’s equation, but using a simple analytical equation. Three dimensionless parameters are proposed to characterize the properties of the workpiece material, the electrolyte solution and working conditions, and also the dimensions of the electrodes and the rate of their relative motion. These parameters are used in the numerical solution and analysis of the results. The obtained relationship between the accuracy and productivity of ECM with an eccentric rotating TE can be used to optimize the process. The error in the shape of workpiece surface is analyzed within the proposed model. The relation between the error of machining and the minimum interelectrode gap is revealed. A two-stage ECM scheme is proposed to reduce the shape error.

The formation of metal microstructures on metal substrates is theoretically analyzed by the example of local silver electrodeposition, using the numerical simulation of interrelated electrochemical and homogeneous chemical reactions. The silver electrodeposition localization and rate are shown to depend on the interrelation between full concentrations of ammonia, silver, and protons in solution. The ammonia relative concentration range is determined, which provided an acceptable combination of the silver electrodeposition localization and rate. By using some simplifications, the distributions of the concentrations of the participants in the reactions and the current density of silver ion reduction are numerically calculated for various concentrations of solution components and interelectrode distances. The degree of localization of metal deposition is shown to depend on the distribution of the concentrations of electroactive silver cations and the non-electroactive complex of this metal near the anode. The deposition rate was found to depend nonmonotonously on the interelectrode distances, which can be explained by difficulties in the reactants’ delivery at small interelectrode distances and increase of the fraction of the silver electroactive ions diffusing toward solution bulk at large interelectrode distances.

The metal electrodeposition into the nanopores of template of porous anodic alumina type under the conditions of mixed kinetics of metal deposition is studied theoretically using analytical and numerical methods. Two main periods of the process are studied: the non-steady-state formation of diffusion layer in the template pores and much longer process of pore filling with the metal. The effect of nonlinearity of the concentration dependence of the exchange current density of metal electrodeposition on the variation of the current density with the time during the diffusion layer formation and pore filling with the metal is studied.

Template-assisted electrodeposition is a versatile technique for preparing metal nanostructures, e.g. nanowires and nanotubes, in anodic aluminium oxide (AAO) templates with cylindrical channels. However, the fraction of pores in which the electrochemical process occurs is not known in advance, which makes coulometric control of the deposition process nontrivial. In this paper, we propose a simple method for determining the fraction of active nanopores, i.e., pores in which metal is deposited. This is based on the analysis of current transients registered during templated electrodeposition. The developed method makes it possible to estimate the density of deposited nanowires and their average length by coulometric control without using scanning electron microscopy.

The processes of mass transfer in the metal electrodeposition on a rotating disk electrode from the solution containing three sorts of ions (electroactive metal cation and indifferent electrolyte containing inactive cation and anion) are studied theoretically. The Nernst–Planck equations in the approximation of the solution electroneutrality reduced to a dimensionless form, which takes into account the elecrodiffusion and convective transfer of all types of ions, are used as the mathematical model. The numerical solution of the mathematical model is carried out by the finite volume method using a non-uniform grid. As a result of the numerical solution, the distributions of potential and ion concentrations are obtained with taking into account the interaction between the electric and hydrodynamic fields in the solutions with various concentrations of supporting electrolyte at various diffusion coefficients of ions of all sorts. The dependences of the limiting current of metal electrodeposition on the concentration of supporting electrolyte are obtained. When calculating the limiting current density in the absence of convection, the thickness of the Nernst diffusion layer is calculated taking into account the effective diffusion coefficient of the solution with three sorts of ions at various concentrations of supporting electrolyte. Using several examples with various ratios between the diffusion coefficients of the anion and inactive cation of the electrolyte, the error in the limiting current calculated using the Nernst diffusion layer approximation, as compared with the limiting current obtained taking into account the convective transport of ions, is estimated.

Within the framework of the Einstein fluctuation–dissipation relation, the theoretical analysis of the noise resistance is carried out for two classical electrochemical ac circuits: Ershler–Randles and Frumkin–Melik-Gaikazyan. It is shown that as the sampling period of the noise signal increases, the noise resistance in the Ershler–Randles circuit tends to its limiting value which coincides with the slow discharge resistance. The asymptotic behavior of the Frumkin–Melik-Gaikazyan circuit is of a different manner. As the sampling period of the noise signal increases, the curve of the noise resistance of the Frumkin–Melik-Gaikazyan circuit transforms into a straight line with the tangent inversely proportional to the thermodynamic capacitance of the electrode. The fluctuation–dissipation relation of Einstein may be used in the theoretical analysis of the noise resistance of other electrochemical ac circuits.

В статье рассматриваются специфические признаки авиационной отрасли как техноценоза: структурированность, аффилированность, общность целей развития, инновационная ориентированность, универсальность схемы финансирования, разнонаправленность прогнозных трендов развития, кооперация и специализация, корпоративные стратегии, тематическая направленность, структура интеллектуального капитала, конкурентоспособность, модульность развития, распределенность, эффективность деятельности. The article examines the specific features of the aviation industry as a technocenosis: structuredness, affiliation, commonality of development goals, innovation orientation, universality of the financing scheme, multidirectional forecast development trends, cooperation and specialization, corporate strategies, thematic focus, structure of intellectual capital, competitiveness, modularity of development, distribution, efficiency of activity.

Theoretical analysis of electrochemically inactive halate-anion ( XO3- , X = halogen) electroreduction at rotating disk electrode (RDE) under steady-state conditions via autocatalytic mediator cycle based on X-2/X- redox couple in acidic aqueous medium has been performed in relation to prospects to use this reaction as cathodic process of high energy density flow batteries. For the first time, full set of coupled diffusion migration-convection transport equations for the components of the system, including kinetic terms due to the comproportionation reaction between solute species, has been solved via numerical and analytical tools. All principal characteristics of the system have been found: distributions of concentrations of all components inside the diffusion layer as well as of induced electric field and of the chemical reaction rate, diffusion-layer thicknesses for all components as functions of the principal dimensionless parameters: passing current, J, ratios of the diffusion-limited currents for species H (protons) and A ( XO3-), J(HA), or for species C (X-2) and A, J(CA), ratio of the diffusion and kinetic layer thicknesses for species A, x(dkA) = z(dA) / z(k), as well as ratios of the diffusion coefficients of components, D-iA = D-i / D-A (i = other components). The strongest dimensionless current, J(max), which can pass across the system, can also be calculated for any set of particular values of the dimensionless parameters: J(HA), J(CA), x(dkA) and D-iA. General features of the dependence, J(max) vs. x(dkA), have been analyzed for various values of J(HA) (i.e. of the ratio of their bulk-solution concentrations, H-o/A(o)) while the value of J(CA) (and consequently of the concentrations' ratio, C-o/A(o)) is very small. It has been demonstrated that within the range of sufficiently low rotation frequencies the maximal dimensional current density, j(max), is comparable with the combined diffusion-limited current of species A ( XO3-) and H (H+), even for extremely low bulk-solution concentration of catalytic species C (X-2), C-o, i.e. passing current can reach enormous values, despite the electrochemical inactivity of species A and H. This feature which is highly beneficial for the application of this reaction in power sources is a direct consequence of the autocatalytic character of the redox-mediator cycle based on reactions of species XO3-, X- and X-2 in acidic medium. (C)2022 Elsevier Ltd.

The effect of pulse-on and pulse-offtimes on the efficiency of micro/nano ECM with ultra-short voltage pulses is theoretically analyzed. A new approximate analytical equation for the time of charging electrical double layer (EDL) is obtained. The equation takes into account all main parameters of the process. It enables one to determine the pulse-on time that provides a high localization of Faradaic process in the zones with small interelectrode gap and a high productivity of ECM process. The results of numerical calculations agree well with the data calculated by the proposed approximate analytical equation. The numerical calculations of the pulse-offtime are performed. The effect of reverse voltage pulse imposed in the pauses on the EDL relaxation time is analyzed. The amplitude of reverse voltage pulse is limited by the condition of the absence of the tool-electrode wear. The proposed algorithm for calculating the pulse-offtime and amplitude of reverse voltage pulse provides the required high coefficient of metal dissolution localization in the zone of small interelectrode gaps at a given pulse-on time. (C) 2020 Elsevier Ltd. All rights reserved.

The developed mathematical model satisfactorily describes the dependence of anodic potential on the current density of steady-state aluminum anodization in the region of average current densities where its main assumptions are fulfilled: the absence of merging of adjacent pores and the absence of overheating of oxide relative to the electrolyte. The model involves several parameters required for calculations. For anodization of aluminum, the values of these parameters are obtained by the analysis of experimental results published by various authors. Calculated current-voltage characteristics agree well with published experimental data. Using the model equations and appropriate parameters, one can calculate not only the dependence of anodic potential on the current density, but also main relationships between the characteristics of anodization: the barrier layer thickness, potential, porosity, spherical radius of pore bottom and spherical radius of cavity in the metal. (c) 2021 Elsevier Ltd. All rights reserved.

The steady-state shape of the end-face of metal wire, which is electrodeposited in a template nanopore, is studied. The deviation of the end-face shape from a plane due to the edge effect is analyzed. The developed model takes into account the dependence of the metal electrodeposition rate on the surface curvature. The model involves a dimensionless parameter that governs the shape of nanowire end-face. The end-face shape is calculated for various values of this parameter. The numerical and approximate analytical solutions of the problem agree well.

The effect of complex formation on the mass transfer during the metal electrodeposition on a rotating disk electrode from the solution containing three types of ions (metal cation, cationic complex, and non-electroactive anion) is studied theoretically. The dimensionless Nernst–Planck equations in the approximation of solution electroneutrality, which take into account the electro-diffusion and convective transfer of all types of ions and the homogeneous reaction of complex formation, are used as the mathematical model. The kinetics of electrochemical reactions is taken into account using the Butler–Volmer equations. In contrast to the known works, the approximations of the Nernst layer, equal diffusion coefficients of all types of ions, and equilibrium complex formation reaction are not used. As a result of numerical solution, the distributions of concentration, potential, and the rate of complex formation reaction are obtained at various parameters of the system under consideration. It is shown that the equilibrium and rate constants of complex formation reaction and the ratio between the diffusion coefficients of complex cation and anion have the strongest effect on the mass transfer.

The corrosion potential Ecorr of STARBOND–CoS alloy in the 0.5 M NaCl solution was measured for 100 h. The anodic and cathodic potentiodynamic curves were measured in the same solution after a preliminary exposure of the test specimen at the corrosion potential Ecorr for 2–100 h. The corrosion current densities icorr were determined using the method of Tafel extrapolation. It is shown that Ecorr shifts from +9 to +275 mV against a saturated silver–chloride reference electrode (sat. Ag/AgCl) and icorr decreases to 40 nA/cm2 in 100 h. These results are explained by the alloy self-passivation, which provides its high corrosion resistance. This enables one to use STARBOND–CoS alloy for fabricating implants.

The electrochemical noise of a system of two identical steel electrodes in the NaCl solution without and with an addition of benzotriazole (BTA) corrosion inhibitor is measured and analyzed. It is shown that this method is a convenient tool for testing the protective properties of inhibitor. The method of impedance spectroscopy applied to this electrochemical system gives the information on the mechanism of inhibitor action.

The effect of common outer diffusion layer in the vicinity of a template on the metal electrodeposition into the template pores is analyzed theoretically for two cases: (1) the template surface is uniformly accessible to the metal cations and (2) the electrolyte flows along the template surface. In the first case, the equation for the current density is obtained taking into account the common outer diffusion layer, the pore depth, and the kinetics of metal deposition. Under certain conditions, which can be determined from this equation, a common outer diffusion layer does not form, and its effect on the pore filling with the metal should not be taken into consideration. In view of the fact that the nanowire growth is a function of the electrolyte flow rate and kinetic parameters, in the second case, the dependences of inhomogeneity of pores filling with the metal on the liquid flow rate and kinetic parameters of electrochemical reaction are obtained. It is shown that, under the conditions of the formation of a common diffusion layer, the uniform pores filling requires controlled mass transfer in the electrolyte near the template and/or the lowest admissible overpotentials. (C) 2020 Elsevier Ltd. All rights reserved.

By the example of the study of AISI 1016 steel corrosion in the HCl solution, the potentialities of various methods for determining the corrosion currents are studied. The corrosion rate of steel without polarization is determined using the method of measuring ohmic resistance of test specimen. It is shown that the iterative method used for the analysis of potentiodynamic curves in the vicinity of corrosion potential avoids the complications that arise when the Tafel extrapolation method is used in the absence of pronounced Tafel sections in these curves.