Electroplating of wear-resistant nanocrystalline coatings from a bath containing basic chromium(III) sulfate (chrome tanning agent)

V. Artemchuk: ORCID 0000-0002-6056-5834ENG: Regularities of the electroplating of chromium–carbon alloy coatings from a bath containing basic chromium(III) sulfate, carbamide, formic acid, sodium sulfate, aluminum sulfate, orthoboric acid, and sodium dodecyl sulfate are studied. Replacement of chromium sulfate as a source of trivalent chromium ions in the solution with basic chromium sulfate (chrome tanning agent) results in a decrease in the current density when metal deposition begins. As a result, the covering power of the bath increases. The effects discovered are determined by changes in the composition of the discharged chromium complexes. A certain excess of OH– groups in the inner sphere of electroactive chromium complexes results in acceleration of electroplat ing. The studied electrolyte based on chrome tanning agent enables one to produce thick high quality nanoc rystalline Cr–C alloy coatings with improved tribological characteristics.RUS: Исследованы закономерности электроосаждения покрытий сплавом хром-углерод из электролита, содержащего основной сульфат хрома(III), карбамид, муравьиную кислоту, сульфат натрия, сульфат алюминия, ортоборную кислоту и додецилсульфат натрия. Показано, что замена сульфата хрома на основной сульфат хрома (хромовый дубитель) в качестве источника ионов трехвалентного хрома в растворе приводит к снижению плотности тока, при которой начинает осаждаться металл; в результате улучшается кроющая способность электролита. Обнаруженные эффекты обусловлены изменением в составе разряжающихся комплексов хрома. Некоторое избыточное количество OH–групп во внутренней сфере электроактивного комплекса хрома ведет к ускорению процесса электроосаждения. Исследованный электролит на основе хромового дубителя позволяет осаждать толстослойные высококачественные нанокристаллические покрытия сплавом Cr-C с улучшенными трибологическими характеристиками.UKR: Досліджено закономірності електроосадження покриттів сплавом хром-вуглець з електроліту, що містить основний сульфат хрому (III), карбамід, мурашину кислоту, сульфат натрію, сульфат алюмінію, ортоборної кислоту і додецилсульфат натрію. Показано, що заміна сульфату хрому на основний сульфат хрому (хромовий дубитель) в якості джерела іонів тривалентного хрому в розчині призводить до зниження щільності струму, при якій починає осідати метал; в результаті поліпшується криюча здатність електроліту. Виявлені ефекти обумовлені зміною в складі разряжающихся комплексів хрому. Деякий надмірна кількість OH-груп у внутрішній сфері електроактивного комплексу хрому веде до прискорення процесу електроосадження. Досліджений електроліт на основі хромового дубителя дозволяє осаджувати товстошарові високоякісні нанокристалічні покриття сплавом Cr-C з поліпшеними трибологічними характеристиками

Mechano-electric interactions in heterogeneous myocardium: development of fundamental experimental and theoretical models.

The heart is structurally and functionally a highly non-homogenous organ, yet its main function as a pump can only be achieved by the co-ordinated contraction of millions of ventricular cells. This apparent contradiction gives rise to the hypothesis that 'well-organised' inhomogeneity may be a pre-requisite for normal cardiac function. Here, we present a set of novel experimental and theoretical tools for the study of this concept. Heterogeneity, in its most condensed form, can be simulated using two individually controlled, mechanically interacting elements (duplex). We have developed and characterised three different types of duplexes: (i) biological duplex, consisting of two individually perfused biological samples (like thin papillary muscles or a trabeculae), (ii) virtual duplex, made-up of two interacting mathematical models of cardiac muscle, and (iii) hybrid duplex, containing a biological sample that interacts in real-time with a virtual muscle. In all three duplex types, in-series or in-parallel mechanical interaction of elements can be studied during externally isotonic, externally isometric, and auxotonic modes of contraction and relaxation. Duplex models, therefore, mimic (patho-)physiological mechano-electric interactions in heterogeneous myocardium at the multicellular level, and in an environment that allows one to control mechanical, electrical and pharmacological parameters. Results obtained using the duplex method show that: (i) contractile elements in heterogeneous myocardium are not 'independent' generators of tension/shortening, as their ino- and lusitropic characteristics change dynamically during mechanical interaction-potentially matching microscopic contractility to macroscopic demand, (ii) mechanical heterogeneity contributes differently to action potential duration (APD) changes, depending on whether mechanical coupling of elements is in-parallel or in-series, which may play a role in mechanical tuning of distant tissue regions, (iii) electro-mechanical activity of mechanically interacting contractile elements is affected by their activation sequence, which may optimise myocardial performance by smoothing intrinsic differences in APD. In conclusion, we present a novel set of tools for the experimental and theoretical investigation of cardiac mechano-electric interactions in healthy and/or diseased heterogeneous myocardium, which allows for the testing of previously inaccessible concepts

A Comparative Study of Cathodic Electrodeposited Nickel Hydroxide Films Electrocatalysts

This paper describes the cathodic electrodeposition of Ni hydroxides from NiCl2 at const. potentials. In a single compartment electrochem. cell, the procedure yields black films that have the appearance of glassy C. XPS analyses reveal that the films consist of a mixt. of Ni(OH)2 and NiOOH in a proportion that depends on the deposition potential; also, SIMS analyses indicate that the coatings are richer in NiOOH in the inner regions towards the support. The electrochem. behavior was compared with data obtained on electrodes based on pure Ni(OH)2 prepd. by cathodic electrodeposition from Ni(NO3)2, following literature procedures. This comparison confirms the composite nature of black Ni hydroxide (BN) coatings, adding that Ni(OH)2 and NiOOH are present in nearly equal amts. The electrocatalytic activity of BN electrodes was tested in the oxidn. of MeOH in alk. solns. Exptl. results are consistent with a mechanism previously proposed in literature for the oxidn. of org. compds. on Ni electrodes. Comparison with electrodes based on pure Ni(OH)2 shows that, in the low potentials region, the presence of a high amt. of NiOOH causes a decrease of activity, while an opposite effect is obsd. when the potential is increased. The black Ni electrodes show a remarkable stability in repeated cycles of oxidn. of MeOH and O2 evolution; under similar conditions, conventional Ni(OH)2 films show an appreciable decrease in thickness, as evidenced by the decrease of peak charge in cyclic voltammetry expts