Formation of Disperse Silver Deposits by the Electrodeposition Processes at High Overpotentials

In this study, electrodeposition of silver from nitrate solution at the high overpotentials was analyzed. Morphologies of silver deposits obtained at the different overpotentials and with the different electrodeposition times were examined using the technique of scanning electron microscopy (SEM). The different disperse morphological forms, such as granules, needle-like and spongy-dendritic ones were formed during silver electrodeposition from this solution. The size of granules decreased and their number increased with the increase of overpotential of electrodeposition. With the increasing overpotential, the induction time for the appearance of spongy-dendritic forms decreased with a tendency to increase their ramification. Mathematic model describing the mechanism of metal electrodeposition at the high overpotentials is proposed and discussed on the basis of the obtained silver surface morphology

STM analiza površine srebrnog ogledala

In this work, the structure of a silver mirror surface was examined by the STM technique. It was shown that the structural characteristics which enable a high degree of mirror reflection from this surface, which is very close to the ideal reflectivity of silver, are: flat and mutually parallel parts of the surface which are smooth on the atomic level, and distances between adjacent flat parts which state several atomic diameters.STM tehnikom je ispitana struktura površine srebrnog ogledala. Pokazano je da su strukturne karakteristike koje su omogućile visok stepen ogledalske refleksije koji je bio veoma blizak idealnoj refleksivnosti srebra: ravni i međusobno paralelni delovi površine koji su glatki na atomskom nivou, i rastojanja između susednih ravnih delova koja iznose nekoliko atomskih prečnika

Novi metod određivanja specifične površine elektrohemijski istaloženog bakra

The specific surface of electrodeposited copper was determined using recently proposed way for the estimation of the real surface area of metal deposits. The obtained values of the specific surface of copper deposits were correlated with the corresponding morphologies of copper deposits.Specifična površina elektrohemijski istaloženog taloga bakra je bila određena korišćenjem nedavno predloženim načinom za procenu realne površine taloga metala. Dobijene vrednosti specifične površine taloga bakra su bile povezane sa odgovarajućim morfologijama taloga bakra

Effect of the orientation of the initially formed grains on the final morphology of electrodeposited lead

The processes of Pb electrodeposition under diffusion control were examined by scanning electron microscopy (SEM) of the formed crystals. The orientation of grains of hexagonal shape formed in the initial stage of electrodeposition strongly affected the final morphology of the Pb crystals. The formation of Pb crystals of the different shape from the same initial shape was discussed in terms of the effect of orientation of initially formed grains on the type of diffusion control. A spherical diffusion layer was formed around the tip of the hexagonal-shaped grain oriented with its tip towards the bulk solution that led to the formation of elongated crystals in the growth process. On the other hand, a cylindrical type of diffusion was responsible for the growth of hexagonal-shaped grains oriented with the lateral side towards the bulk solution. Pb crystals with well-defined sides parallel to the surface area of the macroelectrode were formed under this type of diffusion

General Theory of Disperse Metal Electrodeposits Formation

In this chapter, the fundamental aspects of disperse metals electrodeposition are discussed. The shapes of polarization curves in relation to the deposition process parameters are analyzed.Disperse metal deposits are formed with a nonuniform current density distribution over the surface of the macroelectrode. Adherent granular disperse deposits are produced in an electrodeposition process characterized by a large exchange current density, due to the formation of nucleation exclusion zones around growing grains on the inert substrate. Nonadherent dendritic or spongy deposits are formed in the dominant diffusion control on the level of the macroelectrodeand an activation control on the tips of microelectrodes placed inside the diffusion layer of the macroelectrode. Nonadherent honeycomblike deposit is formed in the presence of strong hydrogen codeposition. All the above cases are discussed in detail and explained using appropriate mathematical models. It is also shown that the formation of dendritic deposits at low level of coarseness strongly increases the apparent exchange current density for the depositionprocess, producing electrocatalytic effect.This is the author's version of the accepted, peer-reviewed manuscript: Popov K.I., Nikolić N.D. (2012) General Theory of Disperse Metal Electrodeposits Formation. In: Djokić S. (eds) Electrochemical Production of Metal Powders. Modern Aspects of Electrochemistry, vol 54. Springer, Boston, MA. [https://doi.org/10.1007/978-1-4614-2380-5_1]The published version: [https://cer.ihtm.bg.ac.rs/handle/123456789/4095

Hydrogen Co-deposition Effects on the Structure of Electrodeposited Copper

The effects of codeposition of hydrogen on the structure of electrodeposited copper is discussed. The simultaneous hydrogen evolution and codeposition are more extensively studied in the cases of electrodeposition of chromium or iron group of metals and/or alloys. An increased hydrogen evolution during the electrodeposition of metals leads to noticeable changes in mass and heat transfer, limiting current density, and Ohmic resistance. Consequently, the simultaneous hydrogen evolution significantly influences the surface morphology of the deposited copper, thus leading to the formation of open porous structure with extremely high surface area. The honeycomb-like or other different features of the surface morphology, as well as various shapes of electrochemically prepared powders, are correlated to the amount of simultaneously evolved hydrogen during the electrodeposition process. From a practical point of view, due to extremely high surfacearea, materials prepared in this way can be technologically very useful for applications as electrodes in fuel cells, batteries, or sensors.This is the author's version of the accepted, peer-reviewed manuscript: Nikolić N.D., Popov K.I. (2010) Hydrogen Co-deposition Effects on the Structure of Electrodeposited Copper. In: Djokic S. (eds) Electrodeposition. Modern Aspects of Electrochemistry, vol 48. Springer, New York, NY. [https://doi.org/10.1007/978-1-4419-5589-0_1]Published version: [https://cer.ihtm.bg.ac.rs/handle/123456789/4097

Uticaj strukture čestica na nasipnu masu elektrolitički dobijenog bakarnog praha

The quantitative microstructural analysis and the sieve analysis of copper powder as well as the scanning electron microscopy analysis of the copper powders particles were performed. It was found that the structure of the copper powder particles determines the apparent density of copper powder. The powder particles from the same fractions of different powders occupy approximately the same volume, but the structure of metallic copper is very different. This causes the difference in apparent densities of copper powder obtained under different conditions. The more dendritic is the structure of powder particles the smaller is the apparent density of copper powder.Izvršena je kvalitativna mikrostrukturna i granulometrijska analiza bakarnih prahova kao i analiza morfologije i strukture čestica praha pomoću skenirajuće elektronske mikroskopije (SEM). Ustanovljeno je da struktura čestica praha određuje nasipnu masu bakarnog praha. Čestice iste frakcije različitih prahova zauzimaju otprilike istu zapreminu, ali je struktura metalnog bakra različita. Ovo uzrokuje razlike u nasipnoj masi bakarnog praha dobijenog pod različitim uslovima. Što je struktura čestica više dendritična to je manja nasipna masa bakarnog praha

Electrodeposition of Copper Powders and Their Properties

A powder is a finely divided solid, smaller than 1,000 μm in its maximum dimension. A particle is defined as the smallest unit of a powder. The particles of a powder may assume various forms and sizes, whereas powders, an association of such particles, exhibit, more or less, the same characteristics as if they were formed under identical conditions and if the manipulation of the deposits after removal from the electrode was the same [1, 2]. The size of particles of many metal powders can vary in a quite wide range from a few nanometers to several hundreds of micrometers. The most important properties of a metal powder are the specific surface, the apparent density, the flowability, and the particle grain size and distribution. These properties, called decisive properties, characterize the behavior of a metal powder.This is the author's version of the accepted, peer-reviewed manuscript: Nikolić N.D., Popov K.I. (2012) Electrodeposition of Copper Powders and Their Properties. In: Djokić S. (eds) Electrochemical Production of Metal Powders. Modern Aspects of Electrochemistry, vol 54. Springer, Boston, MA. [https://doi.org/10.1007/978-1-4614-2380-5_3]Published version: [https://cer.ihtm.bg.ac.rs/handle/123456789/4094