Surface Engineering and Applied Electrochemistry最新文献

Abstract

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.

Abstract

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.

Abstract

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.

Abstract

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.

Abstract

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.

This work demonstrates that the macroscopic size effect, which consists in the influence of electrodeposition surface area on the composition and properties (microhardness and corrosion resistance) of alloy coatings prepared by induced codeposition of iron group metals with tungsten, is a particular case of this type of effects and this requires maintaining the volume current density (VCD) constant during electrodeposition. The effect is associated with the formation of surface oxy-hydroxide and hydrogenated layers. For electrodeposition of Fe–W and Co–W alloys from a citrate bath, it is established that a change in VCD at a definite value for current density of electrodeposition results in changes in the electrode potential, current efficiency, and alloy composition. Anodic dissolution of the modified surface layer allows increasing the microhardness but does not cancel the dependence of coating composition and properties on the electrode surface area.