Konstantin I. Popov

Electrodeposition of Metal Powders with Controlled Particle Grain Size and Morphology

The processes of metal deposition can be categorized into three main groups each of which has different requirements with respect to the physical state of the cathodic product. In electroplating the crystal layer is required to be fine grained, smooth, strongly adhesive, and glassy, i.e., to be easily polished. In refining and electrodeposition relatively coarse grained, rough, but adhesive deposits are required. They have to be of high purity and firm enough to endure handling before melting and casting into shapes suitable for further processing. In metal powder production by electrodeposition, a controlled product particle size is necessary and the product is favored not to or weakly to adhere to the cathode. Generally, powder production requires other conditions than those in electroplating.

Morphology of lead dendrites electrodeposited by square-wave pulsating overpotential

The effect of square-wave pulsating overpotential on the morphology of lead dendrites is discussed. It is shown that the morphology of lead dendrites strongly depends on the parameters determining the shape of the pulsating overpotential wave.

Hydrogen Co-deposition Effects on the Structure of Electrodeposited Copper

The creation of open porous structures with an extremely high surface area is of great technological significance because such structures are ideally suited for electrodes in many electrochemical devices, such as fuel cells, batteries, and chemical sensors. The open porous structure enables the fast transport of gases and liquids, while the extremely high surface area is desirable for the evaluation of electrochemical reactions. The electrodeposition technique is very suitable for the preparation of such structures because it is possible to control the number, distribution, and pore size in these structures by the choice of appropriate electrolysis parameters.

Electrodeposition of Ag from nitrate solutions : Part I. Effect of phosphate ions on morphology

The initial steps of silver deposition from nitrate solutions on silver and platinum substrate were studied. The formation of boulders was observed on both substrates, their growth onto platinum being the more regular. A compact Ag-surface film was not produced under the applied conditions, even after prolonged deposition. Instead, growth of (i) independent large Ag grains occurred at lower overpotentials and (ii) dendrites formed at higher overpotential values. In the presence of phosphate in unstirred solutions 2D and/or 3D dendrites were formed at lower and higher overpotentials, respectively. Increase in electrolyte temperature above 25∘C was found to cause dendrite coarsening, even at lower overpotentials. In stirred solutions compact Ag-surface films were deposited over a wide range of overpotentials, showing different structural features depending on the applied overpotential.

Structural characteristics of bright copper surfaces

In this work, the structures of copper surfaces polished mechanically and polished both mechanically and electrochemically, as well as copper coatings obtained in the presence of basic and top brightening addition agents were examined and compared with the structure of a silver mirror. It was shown by the STM technique that the structural characteristics important for the mirror brightness of the copper surface polished both mechanically and electrochemically and the copper coating are: (1) flat and mutually parallel parts of the surface which are smooth on the atomic level and (2) distances between adjacent flat parts are comparative with the distances between the adjacent flat parts of a silver mirror. Also, on the basis of the STM analysis, a mathematical model treating brightness from the point of view of geometrical optics was developed. X-ray diffraction analysis of the copper surfaces showed that mirror brightness is not associated directly with the degree of preferred orientation.

The visualization of the electrochemical behaviour of metal particles in spouted, fluidized and packed beds

Abstract The electrochemical behaviour of metal particles in spouted, packed and fluidized bed electrodes can be visualized in the same way as in the electrochemical corrosion demonstration. The cathodic reaction, indicated by bright red colour (grey in black-white photographs), occurs on the particles in contact with the cathode current feeder. The profile of red colour corresponds to the current density distribution. This is relevant for all particles in the fixed packed bed and in the annulus of the spouted bed, and for those particles in the fluidized bed which are in contact with the cathode current feeder. All the particles in the spout and fountain of the spouted bed and the majority of the particles in the fluidized bed are not in contact with the cathode current feeder. They are characterized by bipolar behaviour because the resistance of the electrical transfer through the particle is less than that through the surrounding electrolyte. The anodic reaction, indicated by dark blue colour (black in black-white photographs), occurs on the part of the particles in the direction of the cathode current feeder, while the opposite side of the particles is under the cathodic reaction, visualized by bright red colour. The method described could be used for the optimization of three-dimensional electrodes.

Electrode surface coarsening in pulsating overpotential copper electrodeposition

Abstract It is shown that copper deposits obtained in pulsating overpotential electrodeposition are different in structure and less coarse than deposits obtained in the constant overpotential regimes.

Acceleration of electrocatalytic reactions by pulsation of potential: Oxidation of formic acid on Pt and Pt/Pbads electrodes

Pulsating potential electrolysis has been applied to one typical electrocatalytic reaction ie, the oxidation of formic acid on platinum and platinum partially covered by lead adatoms electrodes. It has been found that much higher average cds can be obtained with such regimes than in constant potential electrolysis. The effect can be of considerable interest for the application in electrochemical power sources. An analysis of the mechanism of effects of pulsating potentials has been given. A calculated frequency dependence of the average current density is in agreement with experimental one for both electrodes.

General Theory of Disperse Metal Electrodeposits Formation

The most frequently used form of the cathodic polarization curve equation for flat or large spherical electrode of massive metal is given by