Fundamental aspects of copper electrodeposition in the hydrogen Co-deposition range

This a review paper considering fundamental aspects of copper electrodeposition at high overpotentials where parallel to copper electrodeposition, hydrogen evolution reaction occurs. The two types of copper deposits are formed in the hydrogen co-deposition range: (a) the open and porous structures denoted as the honeycomb-like ones, and (b) powdered deposits. Phenomenology of the formation of the honeycomb-like structure, as well as factors affecting the formation of this type of structure are described in detail. The increase of the specific surface area of the honeycomb-like structure by the application of the periodically changing regimes of electrolysis, such as pulsating overpotential (PO) regime is considered. Correlation between the shape of copper powder particles and the quantity of evolved hydrogen by which they are formed was also presented.Ovo je pregledni rad koji razmatra fundamentalne aspekte elektrohemijskog taloženja bakra na visokim prenapetostima gde paralelno procesu elektrohemijskog taloženja bakra se odigrava reakcija izdvajanja vodonika. Dva tipa taloga bakra su formirana u oblasti ko-depozicije vodonika: (a) otvorene i porozne strukture označene kao strukture pčelinjeg saća, i (b) praškasti talozi. Fenomenologija formiranja strukture pčelinjeg saća, kao i faktori koji utiču na formiranje ovog tipa strukture su detaljno opisani. Povećanje specifične površine strukture pčelinjeg saća primenom periodično promenljivih režima elektrolize, kao što je režim pulsirajuće prenapetosti (PP), je razmatran. Uzajamna veza između oblika čestica praha i količine vodonika izdvojene tokom njihovog formiranja je takođe predstavljena

Формирање металних прахова електролизом: облик честица као функција густине струје измене и пренапетости за реакцију издвајања водоника

The short survey of the dependence of the shape of electrolytically produced powder particles on the exchange current density for metal deposition and overpotential for hydrogen evolution reaction is presented. The decrease of the exchange current density leads to a branching of dendrites and their transformation from needle-like and the two-dimensional (2D) fern-like to the three-dimensional (3D) pine-like shapes. Vigorous hydrogen evolution inhibits the dendritic growth leading to a formation of cauliflower-like and the spongy-like particles. The very thin needles were obtained by molten salt electrolysis. Mechanisms responsible for the formation of both the dendritic (the general theory of disperse deposits formation) and the cauliflower-like and the spongy-like particles (the concept of „effective overpotential”) were also mentioned.Приказан је кратак преглед зависности облика електролитички произведених металних прахова од густине струје измене таложења метала и пренапетости за реакцију издвајања водоника. Смањење густине струје измене доводи до гранања дендрита и њихове трансформације од игличастих и дводимензионалних (2Д) налик папрати, до тродимензионалних (3D) дендрита налик стаблу бора. Интензивно издвајање водоника инхибира дендритични раст доводећи до формирања карфиоластих и сунђерастих честица. Веома фине игле су добијене електролизом из растопа. Такође су разматрани механизми одговорни за формирање и дендритичних (општа теорија формирања дисперзних талога) и карфиоластих и сунђерастих честица (концепт „ефективне пренапетости“).Lecture at the Meeting of Electrochemical Division of the Serbian Chemical Society held on 30 September 2019

Influence of the exchange current density and overpotential for hydrogen evolution reaction on the shape of electrolytically produced disperse forms

In this study, comprehensive survey of formation of disperse forms by the electrolysis from aqueous electrolytes and molten salt electrolysis has been presented. The shape of electrolitically formed disperse forms primarily depends on the nature of metals, determined by the exchange current density (j0) and overpotential for hydrogen evolution reaction as a parallel reaction to metal electrolysis. The decrease of the j0 value leads to a change of shape of dendrites from the needle-like and the 2D fern-like dendrites (metals characterized by high j0 values) to the 3D pine-like dendrites (metals characterized by medium j0 values). The appearing of a strong hydrogen evolution leads to formation of cauliflower-like and spongy-like forms (metals characterized by medium and low j0 values).The other disperse forms, such as regular and irregular crystals, granules, cobweb-like, filaments, mossy and boulders, usually feature metals characterized by the high j0 values. The globules and the carrot-like forms are a characteristic of metals with the medium j0 values. The very long needles were a product of molten salt electrolysis of magnesium nitrate hexahydrate. Depending on the shape of the disperse forms, i.e. whether they are formed without and with vigorous hydrogen evolution, formation of all disperse forms can be explained by either application of the general theory of disperse deposits formation or the concept of "effective overpotential". With the decrease of j0 value, the preferred orientation of the disperse forms changed from the strong (111) in the needle-like and the fern-like dendrites to randomly oriented crystallites in the 3D pine-like dendrites and the cauliflower-like and the spongy-like forms

Mesto Zapadnog Balkana u agendama Rusije i Turske u kontekstu hibridnih pretnji

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OPTIMIZATION BASED DETERMINATION OF THE SET OF CONTINUOUS-STATE COMPONENTS CRITICAL TO THE MECHANICAL SYSTEM STATE

This paper proposes a new approach to determining the set of the most critical continuous-state components in continuous-state mechanical systems. Unlike traditional importance measures, which determine the criticality of individual components, our approach provides selection of the entire set of critical components. In addition, it enables determination of the minimal budget for achieving full or any required performance levelof the mechanical system. We start from the continuum structure function and the system state definition through minimal cut sets. The problem defined in this paper is formulated as a determination of a set of components whose states maximize the system performance level under the budget constraint. Further, we prove that the solution of the formulated problem can be obtained based on the solution to a weighted minimal hitting set problem. The proposed approach is applied to a group of benchmark instances and the obtained results are compared to components’ rankings obtained by using traditional importance measures

Exploring trends in environmental pollution and hazardous chemical waste reporting

In contemporary society, environmental pollution and hazardous chemical waste are pressing concerns. This study investigates reporting trends related to environmental pollution and hazardous chemical waste in twelve scientific journals and daily newspapers. Notably, we found that the year 2013 marked a significant peak with the highest number of articles on these topics. Understanding the publishing and reporting trends of these subjects is pivotal for informed public education and underscores the significant influence of scientific research in shaping media reporting. As the global community faces increasing environmental challenges, accurate and scientific-based reporting is essential for fostering public awareness and facilitating effective solutions

Structural characteristics of bright metal coatings

U rаdu su ispitаnе strukturе gаlvаnskih prеvlаkа mеtаlа kоје su nајčеšćе srеću u prаksi, tј. gаlvаnskih prеvlаkа bаkrа i cinkа. Prеvlаkе cinkа su tаlоžеnе iz sulfаtnоg kupаtilа sа dеkstrinоm i sаlicil аldеhidоm kао dоdаcimа zа sјај, dоk su prеvlаkе bаkrа tаlоžеnе iz dvа rаzličitа sulfаtnа kupаtilа, i tо iz kupаtilа sа dоdаtkоm tiоurее i iz kupаtilа sа dоdаtkоm mоdifikоvаnоg pоliglikоl еtrа, PЕG-а 6000 i 3-mеrkаptо аlkаn sulfоnаtа. Таkоđе, ispitаnе su i strukturе mеhаnički glаčаnе, i mеhаnički i еlеktrоhеmiјski glаčаnе pоvršinе bаkrа. Nаvеdеnе strukturе su upоrеđеnе sа strukturоm pоvršinе srеbrnоg оglеdаlа kао еtаlоnоm. Pоvršinе su ispitаnе tеhnikоm skеnirајućе tunеlskе mikrоskоpiје (SТМ), rеntgеnskо-difrаkciоnоm аnаlizоm i mеrеnjеm rеflеksiје svеtlоsti sа njihоvih pоvršinа. Pоkаzаnо је dа sе оglеdаlski sјај mеtаlnih pоvršinа mоžе pоvеzаti sа visоkim stеpеnоm оglеdаlskе rеflеksiје kојi sе približаvа idеаlnој rеflеksivnоsti istоg mеtаlа, uz štо mаnji stеpеn difuznе rеflеksiје. SТМ аnаlizа gаlvаnskih prеvlаkа bаkrа i cinkа, glаčаnih pоvršinа bаkrа i pоvršinе srеbrnоg оglеdаlа је pоkаzаlа dа strukturnе kаrаktеristikе kоје mоrајu dа budu ispunjеnе dа bi mеtаlnе pоvršinе bilе оglеdаlski sјајnе: (1) rаvni dеlоvi pоvršinе kојi su glаtki nа аtоmskоm nivоu i (2) rаstојаnjа izmеđu susеdnih rаvnih dеlоvа kоја su upоrеdlјivа sа istim rаstојаnjimа kоd pоvršinе srеbrnоg оglеdаlа. Оglеdаlski sјај prеvlаkа bаkrа i pоvršinе bаkrа glаčаnе i mеhаnički i еlеktrоhеmiјski је оdrеđеn rаvnim i mеđusоbnо pаrаlеlnim, аtоmski glаtkim dеlоvimа pоvršinе kојi ukаzuјu nа njihоvu slојеvitu strukturu. Оglеdаlski sјај prеvlаkа cinkа је оdrеđеn mеđusоbnо pаrаlеlnim аtоmski glаtkim pоvršinаmа hеksаgоnаlnih kristаlа cinkа. Nа оsnоvu dоbiјеnih rеzultаtа, prеdlоžеn је mаtеmаtički mоdеl pо kоmе sе sјај rаzmаtrао sаmо sа stаnоvištа gеоmеtriјskе оptikе. Rеntgеnskо-difrаkciоnоm аnаlizоm је pоkаzаnо dа sе оglеdаlski sјај mеtаlnih pоvršinа nе mоžе pоvеzаti sа njihоvоm prеfеrеnciјаlnоm оriјеntаciјоm. U visоkоm stеpеnu su оglеdаlski rеflеktоvаlе svеtlоst: а) rеlаtivnо nеurеđеnа strukturа i mеhаnički i еlеktrоhеmiјski glаčаnе pоvršinе bаkrа kоја је tеžilа (200) prеfеrеnciјаlnој оriјеntаciјi, b) prеvlаkа bаkrа istаlоžеnа sа tiоurеоm sа (111) prеfеrеnciјаlnоm оriјеntаciјоm, i c) prеvlаkа bаkrа istаlоžеnа sа mоdifikоvаnim pоliglikоl еtrоm, PЕG-оm 6000 i 3-mеrkаptо аlkаn sulfоnаtоm sа (200) prеfеrеnciјаlnоm оriјеntаciјоm. SТМ аnаlizа nаvеdеnih pоvršinа је tаkоđе pоkаzаlа dа sе оglеdаlski sјај gаlvаnskih prеvlаkа nе mоžе pоvеzаti sа mеhаnizmоm njihоvоg tаlоžеnjа u prisustvu dоdаtаkа zа sјај. Меhаnizmi tаlоžеnjа bаkrа u prisustvu tiоurее i kоmbinаciје tri аditivа su rаzličiti, pri čеmu su оbе prеvlаkе u približnо istоm stеpеnu оglеdаlski rеflеktоvаlе svеtlоst.In this work, the structures of copper and zinc coatings were examined. The zinc coatings were electrodeposited from a sulfate solution in the presence of dextrin/salycil aldehide mixture. The copper coatings were electrodeposited from a sulfate solution in the presence of thiourea, as well as in the presence of modified polyglycol ether, PEG 6000 and 3-mercapto alkane sulfonate. Also, the structures of copper surfaces polished mechanically and polished both mechanically and electrochemically were examined. These structures are compared with the structure of a silver mirror as reference standard. Copper and zinc coatings, different polished copper surfaces and a silver mirror surface were examined by STM, X-ray diffraction analysis and a measurements of the reflection of light from their surfaces. It was shown that mirror brightness of metal surfaces can be associated with the high degree of mirror reflection which approaches very nearly the ideal reflectance of the same metal, with the small degree of diffuse reflection. STM analysis showed that structural characteristics which must be fulfilled in order for metal surfaces to be mirror bright: (1) flat parts of the surface which are smooth on the atomic level and (2) distances between adjacent flat parts which are comparative with the distances between the adjacent flat parts of a silver mirror surface. Mirror brightness of the copper coatings and the copper surface polished both mechanically and electrochemically was determined by flat and mutually parallel parts of the surface which are smooth on the atomic level and which point out layer structure of these surfaces. Mirror brightness of zinc surfaces was determined by mutually parallel atomically smooth zinc hexagonal crystal surfaces. 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 with the preferred orientation. Mirror brightness were: a) relatively disordered the copper surface polished and mechanically and electrochemically, b) the copper coating electrodeposited in the presence of thoiurea with (111) preferred orientation and c) the copper coating electrodeposited in the presence of modified polyglycol ether, PEG 6000 and 3-mercapto alkane sulfonate with (200) preferred orientation. STM analysis of these surfaces showed that mirror brightness can not be associated with a mechanism of metal electrodeposition. The mechanism of copper electrodeposition is different by the deposition in the presence of thiourea and in the presence of modified polyglycol ether, PEG-6000 and 3-mercapto alkane sulfonate