Surface Engineering and Applied Electrochemistry最新文献

The article considers the issue of protecting substation equipment and overhead lines from high-frequency lightning surges using a device based on a nanocrystalline tape made of an amorphizing ferromagnetic alloy. The object of protection is a substation that uses a cable insert between the overhead line and the substation input. A distinctive feature is the fact that the 35-kV overhead line is made on pores for 110-kV overhead lines. A high danger of surges is shown with such a configuration of the overhead line that includes a cable insert. A method for protecting against high-frequency surges is proposed using a frequency-dependent device operating on the use of an anomalous skin effect.

Qualitative analytical dependence of the value of the coefficient of the surface tension of a liquid on the density of the electric charge on its surface was derived from general theoretical positions by asymptotic methods. It is shown that the value of the surface tension coefficient of a liquid decreases with an increase in the density of the electric charge on the surface of the liquid.

The review, based on the publications by both Russian and international researchers, presents an analysis of the problems of existing technologies for smelting copper concentrates. Three main problems requiring solutions were identified and considered: increasing the efficiency of smelting copper sulfide-containing ores by reducing the copper content in slags obtained during the conversion process; increasing efficiency, including by obtaining an additional economic effect from waste disposal; and reducing the harmful impact on the environment. It was established that trends towards the development of new efficient, environmentally friendly, and cost-effective technologies are characteristic not only of the selected research object but also of a number of other nonferrous metals, such as lead and zinc.

The effectiveness of sumac extract in preventing zinc from corroding in 1 M HCl has been investigated using potentiodynamic polarization (PDP), electrochemical frequency modulation (EFM), electrochemical impedance spectroscopy (EIS) and weight loss tests (WL) at different temperatures. By contrasting the inhibition effectiveness (%IE) with and without the extract, the inhibition efficiency was ascertained. It was found that the corrosion inhibition efficiency increased at higher extract concentrations, peaking at 93.7% at 300 ppm and 25°C, and that the temperature had an opposite effect. According to the PDP data results, sumac extract functions as a mixed-type inhibitor. Generally, the Langmuir adsorption isotherm matched the adsorption process. The extract adsorbs spontaneously onto the metal surface, according to thermodynamic conditions. Analyses of the corrosion product using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) revealed that a protective layer was formed on the metal surface. The outcomes from the several tested methods agreed rather well.

In materials science, titanium dioxide (TiO₂) is one of the widely studied material owing to its outstanding properties, such as tunable electronic properties, good photocatalytic activity, biocompatibility, high thermal and chemical stability, etc. Over the past few years, surface-engineered Cu nanostructures on TiO₂ has been considered as one of the promising candidate in the field of gas sensing and photoelectrochemical water splitting applications. In the present study, TiO₂ nanotubes (TNTs) were fabricated via the electrochemical anodization method and subsequently their surfaces were modified with Cu nanoparticles using a UV light assisted photo-reduction method. Tubular morphology and mixed phase (anatase-rutile) of TiO₂ were confirmed through field emission scanning electron microscopy and X-ray diffraction studies. The energy dispersive spectroscopy data confirmed the deposition of Cu onto the TNT surface. Diffuse reflectance spectroscopy study showed an electronic band gap of TNTs as 3.2 eV. The surface-modified TNTs samples demonstrated an enhanced sensitivity of 0.12 mA mM^–1 cm^–2 towards glucose detection and a higher photocurrent response of 0.28 mA cm^–2 compared with those of pure TNTs samples.

Equal-channel angular pressing (ECAP) technique induces two simultaneous processes in commercial zirconium (Zr) alloys with low (1%) and high (2.5%) niobium content (Nb): grain refinement and deformation-induced phase transformation. The grain refinement reduces the grain size to the sub-micro scale through increasing the grain boundary (or grain perimeter). The structural elements size is reduced to 169 nm for Zr–1% Nb and to 185 nm for Zr–2.5% Nb. During the phase transformation, β-Nb precipitates dissolve in α-Zr matrix to form a supersaturated solution. To demonstrate the effects of those processes on pitting resistance of zirconium alloys before and after ECAP, cyclic potentiodynamic polarization tests in a chloride-containing solution (Ringer) were performed. The results revealed that the corrosion rate (corrosion current density) decreased for nanostructured zirconium alloys, enhancing the corrosion resistance after ECAP. However, the phase transformation induced during ECAP reduced passivity and pitting resistance to chloride ions in alloys with low Nb content. In contrast, no significant change was observed during the two-phase to single phase transformation in high Zr–Nb alloys.

The optimal value of the specific electrical energy introduced into the discharge channel was established, which ensures the maximum release of chemical (thermal) energy of exothermic reactions in the discharge channel. It was established that the amplitude of the pressure wave generated by a high-voltage electrochemical explosion in a condensed medium is determined by the electrical energy introduced into the discharge channel and does not depend on the mass of the exothermic composition. The condition for generating the maximum pressure pulse coincides with the condition for the release of maximum chemical energy and is determined by the optimal value of the specific electrical energy. The established patterns can be used in the synthesis of combined energy sources for discharge-pulse technologies.

Indium tin oxide (ITO) films on polycrystalline p-silicon substrates were obtained by an improved chemical vapor deposition method in a quasi-closed volume at the normal atmospheric pressure by thermal decomposition of vapors of alcoholic solutions of indium chloride and tin chloride. In order to clarify the dependence of the properties of ITO films on the substrate temperature and the ratio X = SnO₂/In₂O₃, the layers were synthesized in the temperature range 170–500°С in various X ratios solutions of indium and tin chlorides. The technological modes of the synthesis were set by controlling the temperature of the substrate and evaporators, to which alcoholic solutions of indium and tin chlorides were supplied, as well as by changing the ratio of the components and the rate of supply of the solution. Under such synthesis conditions, the film growth rate was ∼0.5–1.0 µm/h, which is much higher than in the case of spray pyrolysis under similar conditions. The thicknesses of ITO films were determined by using an MII-4 interference microscope and the transmission spectrum; the film thicknesses amounted to ∼3 μm. The dependence of the resistivity of ITO films on the substrate temperature has been studied. It was shown that the films obtained at the substrate temperatures of 240–260°C had a relatively low resistivity, so the films are of interest for solar cells applications. The X-ray spectra of ITO films were analyzed by identification with the map 00-006-0416 (In₂O₃, cubic) from the Joint Committee on Powder Diffraction Standard database. The average value of the lattice constant was calculated, and it was a = 10.1273 Å, thus being slightly larger than the lattice parameter of pure In₂O₃ (10.1195 Å), which is associated with the presence of Sn that affects the behavior of oxygen ions.

The influence of chemical composition and structural characteristics of elastomer mixtures on the mechanical properties of vulcanizates obtained on the basis of styrene ethylene-propylene butadiene-nitrile rubber (SKEP-BNK) is studied. The main attention is paid to the influence of the polydiene rubber (PD)- and dithiobis-maleimides (DTBFM) concentration on the strength properties, resistance to thermal-oxidative aging, and fatigue endurance of vulcanizates. The results of experimental work related to the change in mechanical properties depending on the variation of concentrations of these components in the mixture are presented. Possible mechanisms for improving the properties of vulcanizates under the influence of external factors are discussed.

The stimulatory effect of TiO₂ nanoparticles and the coordination compound of Sr(II) with a polydentate ligand on the amylase activity was established under submerged cultivation of the micromycete strain Aspergillus niger CNMN FD 06. After purification by gel-filtration on the column of PAD-10 and the ion exchange chromatography on the Hi-Trap^TM Q column, an increase in the specific activity of α-amylase in the case of the variants with the addition of TiO₂ nanoparticles and coordination compound of Sr(II) up to 15 523 and 14 656 U/mg, respectively, compared to the control version 12 037 U/mg was established. The yield of α-amylases after purification was also higher, with an increase of 31 and 20%, respectively, compared to that of control variant. The SDS-PAGE analysis of the isolated proteins revealed the presence of two bands in the active fractions with an apparent molecular mass equal to 65 and 40 kDa, with a more abundant band with a molecular mass of 65 kDa in the case of the preparation obtained with the addition of the Sr(II) coordination compound.