Surface Engineering and Applied Electrochemistry最新文献

Six new azo derivatives were successfully prepared and investigated as corrosion inhibitors for mild steel in 1 M H₂SO₄ solution by weight loss measurements for 24 h at 30°C. It was observed that at higher inhibitor concentrations, the rate of corrosion decreases while the inhibition efficiency and the surface coverage degree increase. The values of the standard free energy of adsorption showed that all prepared azo derivatives have physisorption effects. The correlation between experimental results and theoretical data was considered via semi-empirical molecular orbital calculations for the six studied inhibitors. Theoretical calculations were used to understand the interaction nature between the metal surface and the organic molecules of the studied corrosion inhibitors.

Kinetics of electrodeposition of composite Ni/TiO₂ coatings was studied using the electrolyte based on a deep eutectic solvent (DES) containing choline chloride, ethylene glycol, water additive, and nickel chloride. Degussa P 25 nanopowder was used as a dispersed phase in the electrolyte (1–10 g/dm³). The developed electrolyte allows depositing composite coatings with the content of titanium dioxide reaching ~10 wt %. The electrolytic deposition of the composite was shown to obey Guglielmi’s kinetic model. The main parameters of codeposition of TiO₂ particles into a nickel matrix were determined in the framework of this kinetic model. The codeposition of titanium dioxide was found to inhibit the reaction of the nickel ions' discharge. Electrocatalytic properties of the prepared composite Ni/TiO₂ coatings were evaluated with respect to the hydrogen evolution reaction in an aqueous alkaline solution. A noticeable improvement in the electrocatalytic activity was observed when titanium dioxide particles were introduced into an electrodeposited nickel matrix.

The corrosion inhibition effect of three different types of surfactants, namely, dodecyl trimethyl ammonium chloride (DTAC), octyl phenol poly (ethylene glycol ether) (TX-100), and dioctyl sodium sulfosuccinate (AOT) have been utilized as corrosion inhibitors for AISI 1037 carbon steel in 0.5 mol L^–1 hydrochloric acid. The inhibition efficiency of the surfactants was studied via chemical and electrochemical techniques. The results proved that the order of protection efficiency is: DTAC > TX-100 > AOT. Also, the data revealed that the inhibition efficiency increases by increasing the concentrations of surfactants and decreases by increasing the temperature of the medium. Polarization curves indicated that the investigated surfactants are mixed-kind inhibitors. The adsorption of these surfactants on the AISI 1037 surface follows the Langmuir adsorption isotherm. The calculated free energy from the Langmuir adsorption isotherm indicated that the investigated surfactants are adsorbed on AISI 1037 via mixed adsorption, i.e. physisorption and chemisorption, in 0.5 mol L^–1 HCl. The results of different tests are in excellent agreement.

The results of investigations of electrohydrodynamic (EHD) flows using the schlieren method in the following systems of electrodes are presented: “blade–insulated edge blade,” “blade–two rods,” and “rod with perforated insulation coating–two rods.” Single-stage EHD pumps were designed on the basis of the obtained results. The pressure-flow characteristics of the pumps were studied depending on various factors. It was shown that the performance of the EHD pumps can be increased applying dielectric coatings to the electrodes. The maximum efficiency was obtained in the “blade–blade with insulated edge” system of electrodes, while the maximum static pressure was obtained in a three-rod system with a perforated insulation coating of the emitter. The advantages of a three-rod system were specified as regards to the improvement of the flow characteristics of the pump due to the parallel arrangement of the electrodes and the increase in the pump pressure when using multistage pumps with grid electrodes.

The article presents the results of the studies into the intensification of the processes of extraction of water-soluble polysaccharides from plant raw materials—medicinal hyssop (Hyssopus officialis L.)—under the action of an electric current. The effect of direct, alternating, and pulsed electric currents on the degree of polysaccharides’ extraction was studied in comparison with the traditional pharmacopoeial method. It is shown that the energy consumption for the extraction process, intensified by a pulsed electric current, is significantly lower compared to extraction by convection heating. At the same time, the use of electric current makes it possible to reduce the processing temperature limits from 70 to 40°C, which will allow one to obtain not only aqueous but also aqueous-alcoholic and alcoholic extracts in the future, and, consequently, to extract biologically active water-insoluble substances.

The anodization process was applied to 17-4PH stainless steel to modify its surface and to enhance hydrophobicity. The effects of various H₂SO₄/glycerin electrolytes and applied voltages on the water contact angle, the surface morphology (roughness), and corrosion resistance were investigated. It was observed that a high ratio of an H₂SO₄/glycerin electrolyte and high applied potentials resulted in an increase of a contact angle and an enhancement of the surface roughness. The highest contact angle was found to be up to 122.3°, when anodizing at 40 V using 70/30 of H₂SO₄/glycerin as electrolyte. Any further increase in the ratio of H₂SO₄/glycerin tended to reduce the contact angle. An electrochemical test showed that corrosion resistance was dependent on the hydrophobicity and surface roughness.

The characteristics and parameters of an overstressed high-current discharge with a duration of 100–150 ns in air, which was ignited between an aluminum electrode and a chalcopyrite electrode (CuInSe₂), are presented. The air pressure was 13.3 and 101.3 kPa. In the process of microexplosions of inhomogeneities on the working surfaces of electrodes in a strong electric field, aluminum vapors and chalcopyrite vapors were introduced into the interelectrode gap, which creates the prerequisites for the synthesis of thin films based on quaternary chalcopyrite: CuAlInSe₂. The films synthesized from the products of electrode destruction were deposited on a quartz plate at a distance of 2–3 cm from the center of the discharge gap. The current and voltage pulses across the discharge gap of d = 1 mm, as well as the pulse energy input into the discharge, were investigated. The plasma emission spectra were studied, which made it possible to establish the main decay products of the chalcopyrite molecule and the energy states of atoms and singly charged ions of aluminum, copper and indium, which are formed in the discharge. The reference spectral lines of atoms and ions of aluminum, copper, and indium were established, which can be used to control the process of deposition of thin films of quaternary chalcopyrite. Thin films were synthesized from the degradation products of chalcopyrite molecules and aluminum vapors, which may have the composition of the quaternary chalcopyrite CuAlInSe₂; the transmission spectra of the synthesized films in the spectral range of 200–800 nm were studied. By the method of numerical simulation of the plasma parameters of an overstressed nanosecond discharge based on aluminum and chalcopyrite vapors in air by solving the Boltzmann kinetic equation for the electron energy distribution function, the electron temperature and density, the specific power losses of the discharge for the main electronic processes and their rate constants depending on the value parameter E/N for plasma of vapor-gas mixtures based on air, aluminum vapor, and ternary chalcopyrite were modulated.

The structural phase composition and some properties of a modified medium-carbon steel 45 surface after being subjected to cathodic plasma electrolytic nitriding in ammonium chloride and ammonia solution were studied. It was shown that the steel surface cathodic nitriding is accompanied with a high-temperature oxidation along with formation of FeO, Fe₂O₃, and Fe₃O₄ oxides, as well as nitrogen diffusion and quenching with formation of FeN, Fe₃N, and Fe₄N phases, martensite, and residual austenite. A competitive effect was revealed of the surface erosion resulting from the discharges and high-temperature oxidation on the morphology and surface roughness. It was found that the maximum microhardness of the modified layer reaches 1040 HV, and the current density of the nitrided surface corrosion decreases by 1.5–2.4 times.

The paper presents the results of extraction from amber, which was subjected to high-voltage electric pulse treatment in order to intensify the extraction of target components. This method of processing made it possible to achieve a high degree of grinding of the material and the occurrence of additional micro- and macropores, which increased a total contact area of the phases required for an effective process of extracting raw materials. The processing was carried out in chambers of a high-voltage pulse-periodic generator with storage capacities of 0.25 and 1.0 μF, an output voltage of 50 kV, and different number of pulses for the corresponding capacitance. Amber stones with an average size of 8.2 mm were selected for research. The process was carried out in an alcoholic medium with different electrical characteristics. The dependences of variations in the dry matter content, total mineralization, content of organic acids, active acidity pH, and optical density in the extract on the number of discharges at different pulse energies were obtained as a result. The density of amber before and after processing was determined, which showed the ability of electric spark discharges to create additional porosity of the material necessary to ensure effective internal mass transfer. The results of the study can be used for the industrial implementation of electrospark processing of amber in order to obtain extracts with a complex of useful substances applicable in food, pharmaceutical, and cosmetic industries.