Surface Engineering and Applied Electrochemistry最新文献

Oxides in the form of micro- and nanosized powder, containing agglomerates of particles with a high specific surface, were obtained by means of electric Ti and W wire explosion in the air. An X-ray phase analysis showed that the only product of Ti destruction is TiO₂, while the electric explosion of W conductors results in the formation of WO₃ + W₂O₇ mixture, in which tungsten anhydride WO₃ dominates, and traces of a residual metallic W come across. The photocatalytic properties of electroexplosive powder were studied using a model oxidation reaction of methylene blue. It was revealed that both TiO₂ and the WO₃ + W₂O₇ mixture demonstrate catalytic activity within a wide spectrum of radiation, including the visible one. The catalytic activity of the WO₃ + W₂O₇ mixture under ultraviolet and incandescent lamp radiation was inferior to that of TiO₂; however, in the solar radiation, the rate of dye degradation with the participation of tungsten oxides is higher. In this case, the average rate of decreasing concentration of the dye in water containing a mixture of WO₃ + W₂O₇ depends little upon the type of the radiation source.

Copper substituted ferrites (Cu_xFe_3 – xO₄; (0 ≤ x ≤ 1.0) were prepared by the egg white auto-combustion method at 550°C and investigated their physicochemical properties via the thermogravimetric analysis, infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and electrochemical ones via cyclic voltammenry and Tafel polarization. The formation of copper ferrites with a spinel phase was confirmed by the Fourier-transform infrared spectra having characteristic vibration peaks and by the X-ray diffraction spectra with reflection planes. The electrochemical performance of the oxygen evolution reaction of copper ferrites on glassy carbon electrodes was investigated in 1 M KOH. No redox couple was observed in cyclic voltammograms of the glassy carbon/oxide electrode in the selected oxygen overpotential regions. The iR-free Tafel polarization curves having higher Tafel slopes (b = 72–125 mV dec^–1) and a lower current density (i = 0.29–4.7 mA cm^–2 at 0.85 V) exhibited a sluggish nature of the fabricated oxide electrodes from the electrocatalytic point of view. The substitution of Fe by Cu in the oxide lattice considerably increased the electrocatalytic activity for the oxygen evolution reaction. Based on the current density for the oxygen evolution reaction, the 0.75 mol Cu-substituted oxide electrode was found to be the most active electrode among the prepared oxides. The order of the reaction related to the [OH^–] concentration was a unity for almost all of the electrodes except when 0.25 mol Cu-substitution followed the second-order kinetics.

Ceramics and composites, many of whose physicochemical properties significantly exceed similar properties of metals and their alloys, are processed qualitatively mainly by the electroerosion method. Despite the existing works, the mechanism of the initial stage of the removal of materials has not yet been identified. For a comprehensive understanding of the mechanism of the removal of dielectrics, a new model is proposed based on the experimental results obtained on an improved electroerosion installation. It was revealed that the initial stage of the removal of a dielectric material consists of three successive stages that are associated with the synergistic effect on the process of the anionic group of electrolytes, plasma flare, and the cavitation shock. This makes it possible to better understand the mechanism of the removal of composite and ceramic materials, which should contribute to ensuring the machinability of those materials and their wide use in promising technologies.

In this study, flavonoids were extracted from Laurus nobilis leaves, and the extract was evaluated as corrosion inhibitor for pipelines of reverse osmosis (RO) water at 25°C for different concentrations:1, 2, 3, 4, and 5 ppm, The extract demonstrated a high inhibition efficiency (96.3%) at 1 ppm. The effect of temperature on the inhibition efficiency for the optimal concentration of the flavonoid extract of 1 ppm was studied at 35, 45, and 55°C. The results revealed that the efficiency was reduced as temperature increased. Furthermore, the kinetic parameters like activation energy (E_{{text{a}}}^{*}), enthalpy of activation ΔH*, entropy of activation ΔS*, and Gibb’s free energy of activation ΔG* were calculated. Thus, the flavonoids extract of Laurus nobilis can be used as green inhibitor for corrosion because it does not contain toxic compounds. In addition, the effect of the flavonoids extract dissolved in the RO water on the liver enzymes and hematological parameters were studied after oral administration by male rabbits for 28 days. The results indicated no significant difference in the serum level of Alanine and Aspartate aminotransferase and alkaline phosphate, while the hemoglobin concentration and the red blood cells number increased after treatment with the flavonoids extract. Besides, application of the flavonoid extract revealed inhibition in the growth of Pseudomonas aeruginosa and Bacillus subtilis bacteria at 1 ppm concentration.

Photo-induced anisotropy measurements were carried out in thin films of azopolymers PEPC with Solvent Yellow 3, with the concentrations of 10 and 30 wt % of polymers with azo groups in their side-chain. The experimental dependences of the azimuths of the probe beam at the pump beam angles for samples were studied. The photoinduced dependence of the sample birefringence of the probe beam at the incident polarization angle of the pump beam was carried out by the polarimetric method for the studied samples. The geometric phase of anisotropic carbazole-containing azopolymers, in contrast to the dynamic phase, can be measured by the proposed polarimetric method without involving interferometry methods. This is possible because the geometric phase is not controlled by the difference in optical paths but is the result of a change of polarization inside the films due to photoinduced changes in its spatial structure.

By the example of electrodeposition of Co–W alloys, this work shows that observed peculiarities of induced codeposition, including the macroscopic size effect in the composition and properties of deposited layers and their nanocrystallinity, are a consequence of the fact that the deposition-inducing species (a complex of the deposition-inducing metal) has the form of a high-molecular-weight polymer. Under the conditions of (relatively) high current loading on a plating electrolyte (high volume current density), this results in involvement of water molecules in the electrochemical process, formation of oxy-hydroxide layers, hydrogenation, an increase in the alloy tungsten content as a result of the side reaction of hydrogen evolution, alkalization of near-electrode region, and polymerization of the deposition-inducing metal species. Because of the presence of macroscopic size effect (i.e., the dependences of composition and properties of deposited coatings on the electrodeposition surface area), industrial scaling up of this electrodeposition technology will require maintaining the current loading on a plating bath at a constant level, along with other parameters traditional for electrochemical materials science.

It is known that the methods of electrolytic oxidation, including traditional anodizing and microarc oxidation, implemented according to classical schemes in electrolytic baths with mechanical, pneumatic, and magnetic mixers, cannot provide high-quality homogeneous oxide coatings on the inner surfaces of products made from valve metal alloys. In this paper, the principal possibility of obtaining high-quality uniform coatings on the extended internal surfaces of products, including the surfaces of deep holes, when an electrolyte solution is passed through them, is revealed. It has been experimentally proved that, based on the proposed approach, it is possible to process products with deep holes, achieving a ratio of both minimum and maximum values of the thickness and the breakdown voltage of coatings on the internal and external surfaces in a range of 0.85–0.93. A possibility of forming coatings exclusively on the internal surfaces of products without changing the state of their external surfaces, moreover, without using expensive electrolytic baths—inside internal cavities of products themselves, is shown. A good correlation between the values of the thickness and of the breakdown voltage of coatings has been established. As a result, a possibility of indirectly determine the coatings thickness based on the results of their breakdown voltage measuring has been substantiated.