Simulation of an electrolytic bath for electrodeposition of multilayer shielding coatings

In this the calculation work galvanic bath of Cu/(Ni+Cu) multilayer shielding coatings formation from an acetate electrolyte containing 0,03 mol/L of CuAc2, 0,3 mol/L of NiAc2 and 1,66 mol/L of acetic acid were made. According to the results of polarization studies values of coatings deposition pulse mode current density have been chosen and current efficiency of copper and nickel during deposition of Cu-Ni alloy has been determined. To ensure a constant formulation of the electrolyte it has been proposed to use insoluble anodes made of stainless steel and continuous circulation of the electrolyte. The scheme of steams enabling the adjustment of the solution formulation with the use of an additional collecting vessel has been developed. The formulation of the correcting stream continuously fed into the collecting vessel has been calculated

Измерение удельной поверхности рыхлого осадка меди электрохимическими методами

In the work the surface area of the electrode with dispersed copper deposit obtained within 30 seconds was evaluated by techniques of chronopotentiometry (CPM) and impedance spectroscopy. In method CPM the electrode surface available for measurement depends on the value of the polarizing current. At high currents during the transition time there is a change of surface relief that can not determine the full surface of loose deposit. The electrochemical impedance method is devoid of this shortcoming since the measurements are carried out in indifferent electrolyte in the absence of current. The area measured by the impedance is tens of times higher than the value obtained by chronopotentiometry. It is found that from a solution containing sulfuric acid the deposits form with a high specific surface area. Based on these data it was concluded that the method of impedance spectroscopy can be used to measure in situ the surface area of the dispersed copper deposits.В работе проведена оценка площади поверхности электрода с дисперсным осадком меди, полученным в течение 30 секунд методами хронопотенциометрии (ХПМ) и импедансной спектроскопии. В методе ХПМ поверхность электрода, доступная для измерения, зависит от величины поляризующего тока. При больших токах в течение переходного времени происходит изменение рельефа поверхности, что не позволяет определить полную поверхность рыхлого осадка. Метод электрохимического импеданса лишен этого недостатка, так как измерения проводятся в индифферентном электролите в отсутствие тока. Площадь, измеренная методом импеданса, в десятки раз превышает значения, полученные методом хронопотенциометрии. Установлено, что из раствора, содержащего серную кислоту, формируются осадки с высокой удельной поверхностью. На основании полученных данных сделан вывод, что метод импедансной спектроскопии может быть использован для измерения in situ площади поверхности дисперсных осадков меди

Determination of the Growth Time Period of Loose Zinc Deposit Using Interval Analysis Methods

Abstract: A characteristic of obtaining metal powders by direct current electrolysis is changes in the morphology of particles over the loose deposit layer thickness up to the formation of large spherulites. Deposits should be periodically removed from the cathode in order to obtain a powder with homogeneous composition. This paper justifies the choice of the parameter describing the change in loose deposit properties and proposes a method for determining the periodicity of its removal from the cathode. Loose zinc deposits were obtained at 25°C from zincate electrolyte containing 0.3 mol L–1 of ZnO and 4 mol L–1 of NaOH at a current setpoint exceeding six times the limiting diffusion current calculated using the smooth electrode. Electrode potential, deposit thickness and evolved hydrogen volume were measured directly in the process of electrolysis. Current redistribution between the metal reduction and hydrogen evolution leads to a change in the structure of loose deposit particles. It is shown that the differential current efficiency of zinc is the parameter describing the change in the loose zinc deposit density. Its value should not exceed 0.96, in order to ensure deposition of loose deposit with homogeneous properties. A further increase in current efficiency will lead to the formation of aggregates at the deposit growth front. It is proposed to determine the periodicity of loose deposit removal from the cathode using the empirical equation for the time dependency of differential current efficiency of zinc. The mathematical and statistical analysis of the data obtained in six replicates was carried out. The interval approach made it possible to significantly narrow the range of permissible differential current efficiency values and, as a consequence, to determine empirical equation coefficients with acceptable accuracy and calculate the growth time period of a deposit with homogeneous structure. The obtained approach can be used to estimate the time period of loose metal deposition accompanied by hydrogen evolution. © 2020, Allerton Press, Inc.This study was supported by the Government of the Russian Federation, regulation no. 211, state assignment no. 0836-2020-003

Statistical Analysis of the Distribution of Impurities during Copper Electrorefining

Abstract: Electrolytic copper refining allows one to obtain high-purity copper, so analyzing the main ways impurities transition into electrolysis products is a relevant problem. Solving it makes it possible to control the process when changing the composition of raw materials and, as a result, the content of impurities in the anodes. In this work, on the basis of a complex analysis and synchronization of a large array of data on impurity concentrations in various industrial environments obtained on a series of commercial cells, the directions of the flow of impurities is determined and the relationship between the content of impurities in the different products of the electrolysis (slime, electrolyte, and copper cathode) is established. It is shown that the transition of impurities from one process medium (source) to another (receiver) occurs by four main schemes: linear increase, no visible dependence, the presence of the limit concentration in the receiver, and the presence of the threshold concentration in the source. The results of a statistical analysis of the distribution of six impurities (bismuth, arsenic, lead, sulfur, nickel, and silver) belonging to different groups are presented in four main pairs of the impurity source–receiver: anode–solution, anode–slime, slime–cathode, and solution–cathode. For all dependencies of the impurity concentration in the source on the content in the receiver, the coefficients of linear regression equations are determined and their significance is estimated. The coefficients make it possible to explain the pathways of the impurity transition observed in the commercial cells and predict the quality of cathode copper and the composition of slime when the anode composition changes. Calculations show that the accumulation of impurities in the cathodes is due to the occlusion of slime particles and the incomplete removal of the solution from the surface of commercial cathodes rather than electrochemical reactions. Attempts to improve and develop the technology of copper electrorefining should be focused on finding surfactants that would prevent the adsorption of suspended slime particles on the cathode surface, as well as on more completely washing the electrolyte off of them. © 2021, Allerton Press, Inc.This work is performed in the frame of the State Assignment number 075-03-2020-582/1 dated 18.02.2020 (the theme number 0836-2020-0037)

Sedimentation of Ultradispersed Diamonds in the Citrate Copper-Plating Electrolyte

Abstract—The aggregation and sedimentation of ultradispersed diamonds (UDDs) in a citrate copper-plating electrolyte (CCPE) used to fabricate composite electrochemical coatings are investigated. The sedimentation and aggregation stability is investigated in order to select the UDD concentration in the CCPE. This is necessary to fabricate composite copper coatings with improved operational characteristics (increased hardness, wear resistance, and corrosion resistance), as well as impart them new properties (antifriction and catalytic). The UDD content in the electrolyte varies in limits from 0.2 to 2.0 g/L. The size distribution of the UDD particles in the electrolyte immediately after the suspension preparation and after the 10-day holding is determined using a Malvern Mastersizer 2000 laser diffraction analyzer. The aggregation and sedimentation stability of the UDD suspension in the CCPE is investigated by the gravimetric method with the continuous weighing of a quartz small cap immersed into this suspension. The quartz cap is associated with a Sartorius R200D analytical balance with the help of a quartz wire. The experimentally determined time dependence of the weight of settling UDD particles is Q = f(t). The relative size distribution of the particles is determined from this dependence. It is established that the sedimentation stability is substantially affected by the aggregation of the particles, the intensity of which increases with an increase in the UDD concentration. The results satisfying the requirements on the aggregation and sedimentation stability are found for the UDD suspension in the CCPE with a concentration of 1.0 g/L. In this case, the high content of the dispersed phase is combined with aggregation and sedimentation stability, which makes it possible to fabricate copper composite coatings with improved operational properties. © 2019, Allerton Press, Inc

EFFECT OF ELECTROLYTE COMPOSITION ON ELECTROCATALYTIC PROPERTIES OF NICKEL FOAMS

В работе установлено, что пористость никелевых пен оказывает влияние на каталитические свойства электрода по отношению к реакции выделения водорода. Показано, что пена, полученная из сульфат-хлоридного электрода обладает наибольшей пористостью. Величина перенапряжения водорода на данной пене была наименьшей среди исследованных образцов, что согласуется с результатами расчета пористости.It was found that the porosity of nickel foams affects the electrode catalytic activity for the hydrogen evolution reaction. It is shown that the foam obtained from the sulfate-chloride electrode has the highest porosity. The hydrogen overvoltage on this foam was the lowest among the samples studied, which correlates with the results of the porosity calculation

Approach to Estimating the Permeability of Metal Foams for Hydrogen Evolution

В соответствии с теорией протекания предложен подход, позволяющий на основе анализа количества и расположения выходов каналов на поверхности пен, оценить их проницаемость для эвакуации газа при получении водорода щелочным электролизом. Увеличение «массы» бесконечного кластера и числа связей коррелирует с уменьшением катодного перенапряжения.An approach based on percolation theory allows estimating channels permeability for hydrogen evacuation during alkaline electrolysis. Estimation is based on the analysis of number and location of channels on the foams surface. An increase in the infinite cluster “mass” and in the bonds number correlate with cathodic overvoltage decrease

Effect of the Nature of Deposited Metal on the Morphology of Electrolytic Deposits

Установлено, что природа ионов металла, разряжающихся на катоде, оказывает значительное влияние на морфологию осадка. Осадки никеля обладают характерной структурой пены: на них присутствуют крупные поры (каналы эвакуации водорода), вокруг которых кристаллизуется металл в форме дендритов. Осадки сплава Ni–Co по своей морфологии близки к рыхлым порошкообразным металлам.It was found that the nature of metal ions discharged at the cathode has a significant effect on the deposit morphology. Pure nickel deposits have a typical foam structure with large pores composed of dendrites. The Ni-Co alloy deposits are characterized by morphology close to loose powder metals

Выбор условий получения электролитических порошков цинка для металлнаполненных композиций

The paper presents a method of obtaining high-dispersed zinc powders by electrolysis and comparison of the properties of zinc-rich compositions prepared using as a pigment zinc powders obtained by different methods. Measurements have shown that the electrical conductivity of zinc-rich coatings containing electrolytic zinc powder, not inferior to the conductivity of the film with powder PZHD-0 obtained by the method of evaporation-condensation, despite the significant difference in the amount of zinc pigment. On the basis of the received data we can conclude that the use of electrolytic zinc powder as a pigment will significantly save zinc.В работе представлен способ получения высокодисперсных порошков цинка электролизом и сравнение свойств цинкнаполненных композиций, приготовленных с применением в качестве пигмента цинковых порошков, полученных разными методами. Проведенные измерения показали, что удельная электропроводность цинкнаполненных покрытий, содержащих электролитический порошок цинка, не уступает по проводимости пленкам с порошком ПЦВД-0, полученного методом испарения-конденсации, несмотря на существенное различие в количестве цинкового пигмента. На основании полученных данных можно сделать вывод, что использование электролитического порошка цинка в качестве пигмента позволит значительно экономить цинк.This work was supported by RFBR, project number 11-03-00226.Работа выполнена при поддержке РФФИ, проект № 11-03-00226

NICKEL POWDER SYNTHESIS BY DISPERSION DURING PULS ELECTROLYSIS

It was found that dispersion process begins at the current exceeding limiting diffusion current on the initial surface 40 times. At these conditions share of dispersed particles is 26 %. The paper has shown that pulse electrolysis mode, being alternation of the cathodic and anodic current pulses can be used for process intensification and obtaining of highly dispersed nickel particles.В работе установлено, что процесс диспергирования начинается при токах, превышающих предельный диффузионный ток на исходной поверхности в 40 раз. При этом доля диспергировавших частиц составляет 26 %. Показано, что для интенсификации процесса диспергирования и получения высокодисперсных частиц никеля может быть использован импульсный режим электролиза, состоящий в чередовании катодных и анодных импульсов тока