Implementation of the Chicot–Lesage Composite Hardness Model in a Determination of Absolute Hardness of Copper Coatings Obtained by the Electrodeposition Processes

The influence of various electrolysis parameters, such as the type of cathode, composition of the electrolyte and electrolysis time, on the morphology, structure and hardness of copper coatings has been investigated. Morphology and structure of the coatings were analyzed by scanning electron microscope (SEM), atomic force microscope (AFM) and X-ray diffraction (XRD), while coating hardness was examined by Vickers microindentation test applying the Chicot–Lesage (C–L) composite hardness model. Depending on the conditions of electrolysis, two types of Cu coatings were obtained: fine-grained mat coatings with a strong (220) preferred orientation from the sulfate electrolyte and smooth mirror bright coatings with a strong (200) preferred orientation from the electrolyte with added leveling/brightening additives. The mat coatings showed larger both measured composite and calculated coating hardness than the mirror bright coatings, that can be explained by the phenomena on boundary among grains. Independent of electrolysis conditions, the critical relative indentation depth (RID) of 0.14 was established for all types of the Cu coatings, separating the zone in which the composite hardness can be equaled with the coating hardness and the zone requiring an application of the C–L model for a determination of the absolute hardness of the Cu coatings.

Efficiency and selectivity of CO2 reduction to CO on gold gas diffusion electrodes in acidic media

The electrochemical reduction of CO2 to CO is a promising technology for replacing production processes employing fossil fuels. Still, low energy efficiencies hinder the production of CO at commercial scale. CO2 electrolysis has mainly been performed in neutral or alkaline media, but recent fundamental work shows that high selectivities for CO can also be achieved in acidic media. Therefore, we investigate the feasibility of CO2 electrolysis at pH 2–4 at indrustrially relevant conditions, using 10 cm2 gold gas diffusion electrodes. Operating at current densities up to 200 mA cm−2, we obtain CO faradaic efficiencies between 80–90% in sulfate electrolyte, with a 30% improvement of the overall process energy efficiency, in comparison with neutral media. Additionally, we find that weakly hydrated cations are crucial for accomplishing high reaction rates and enabling CO2 electrolysis in acidic media. This study represents a step towards the application of acidic electrolyzers for CO2 electroreduction.

Effect of De-Twinning on Tensile Strength of Nano-Twinned Cu Films

Tensile tests were carried on the electroplated Cu films with various densities of twin grain boundary. With TEM images and a selected area diffraction pattern, nano-twinned structure can be observed and defined in the electroplated Cu films. The density of the nano-twin grain structure can be manipulated with the concentration of gelatin in the Cu-sulfate electrolyte solution. We found that the strength of the Cu films is highly related to the twin-boundary density. The Cu film with a greater twin-boundary density has a larger fracture strength than the Cu film with a lesser twin-boundary density. After tensile tests, necking phenomenon (about 20 μm) occurred in the fractured Cu films. Moreover, by focused ion beam (FIB) cross-sectional analysis, the de-twinning can be observed in the region where necking begins. Thus, we believe that the de-twinning of the nano-twinned structure initiates the plastic deformation of the nano-twinned Cu films. Furthermore, with the analysis of the TEM images on the nano-twinned structure in the necking region of the fractured Cu films, the de-twinning mechanism attributes to two processes: (1) the ledge formation by the engagement of the dislocations with the twin boundaries and (2) the collapse of the ledges with the opposite twin-boundaries. In conclusion, the plastic deformation of nano-twinned Cu films is governed by the de-twinning of the nano-twinned structure. Moreover, the fracture strength of the nano-twinned Cu films is proportional to the twin-boundaries density.

PROSPECTS FOR THE USE OF TRICHLOROETHYL AMIDES WITH THIOAMIDE FUNCTIONS IN THE TECHNOLOGY OF BRILLIANT NICKEL PLATING

The influence of organic additives in the nickel-plating sulfate electrolyte on the pos sibility of obtaining shiny coatings is investigated. The presence in the structure of the additive of trichloramide fragments and substituents containing a thiocarbonyl group-a residue of thiourea or rubeanoic acid, allows to obtain shiny nickel coatings without the introduction of additional reagents.

USE OF PYRAZOLE-CONTAINING ISOTHIURONIUM SALTS AS GLOSS FORMING ADDITIVES IN ELECTROCHEMICAL NICKEL PLATING TECHNOLOGY

The introduction of available pyrazole-containing isothiuronium salts as additives to a standard nickel-plating sulfate electrolyte for the electrochemical production of shiny nickel coatings is considered

High-Potential Pseudocapacitive Energy Storage System: Iron-Based Polyferric Sulfate Electrolyte and Partially Sacrificial Graphite Electrode

Tremendous research works including nanofabrication techniques and crystal defect preparation approaches have been applied to enhance the capacitance of bulk materials. However, a comprehensive understanding of active sites in the reaction process is an enigma for all researchers. This work reported an environmentally friendly system with a basic polymerized ferric sulfate (BPFS) electrolyte and electroactive graphite electrode, which achieved high area capacitance and showed the different characteristics of active sites. This enhanced energy storage system shows the evidence that carbon materials are electrochemically activated as a result that active groups could react with iron groups in aqueous solutions. A high area specific capacitance of 12 F cm-2(1255 F g-1) is obtained in a mixed BPFS at 5 mV s-1 in a potential window of 2.1 V in a three-electrode cell. In an aqueous solution capacitor, a capacity of 4.8 F cm-2 at 30 mA from 0 V to 1.5 V is achieved at room temperature. It has the potential to develop a low-cost, high energy storage, and high safety system, which can be a lead-acid battery substitute.

Development of a new suspension electrolyte based on methane-sulphonic acid for the electrodeposition of Cu–TiO2 composites

Electrodeposition of composite coatings based on copper is a promising direction in the creation of advanced materials for multifunctional purposes. An important area of composites application is to use them in the treatment systems for gas emissions and wastewater. It is advisable to use semiconductor oxide materials, in particular titanium dioxide, as the photocatalysts in the photo destruction of organic pollutants of wastewater. The structural features of wastewater treatment equipment require that titanium dioxide particles should be fixed in a rigid matrix. Resolving the task of fixing photosensitive elements at the surface of a certain configuration implies the electrodeposition of coatings by composites, in particular Cu–TiO2. An important factor affecting the functional characteristics of composites and their manufacturing technology is the nature of the electrolyte. It has been shown that the electrodeposition of Cu–TiO2 composites from methane-sulfonate electrolytes makes it possible to reduce the coagulation of the dispersed phase and to obtain coatings with a high content of titanium dioxide from a suspension solution containing no more than 4 g/l of TiO2. It was established that the content of the dispersed phase in the composite made at a current density of 2 A/dm2 and the concentration of titanium dioxide in the electrolyte at the level of 4 g/l is 1.3 % by weight, which is twice as much as when using a sulfate electrolyte. It has been shown that the increase in the content of the dispersed phase in the coatings from 0.1 to 1.3 % by weight is accompanied by an increase in the degree of photo destruction of the colorant from 6 to 15.5 %. The micro-hardness of coatings increases, in this case, by 30 %. The proposed electrolyte to make the Cu–TiO2 composites is an important contribution to the development of the synthesis of wear-resistant high-performance photocatalysts for treating wastewater from organic pollutants