This article has been retracted. Please see the Retraction Notice for more detail: https://doi.org/10.3103/S1068375526030014
This paper examines the influence of the ionization cost of molecules on the results of mathematical modeling of an electric discharge in water. A function approximating the dependence of the ionization cost of molecules on plasma temperature is proposed, and its parameters are determined. The adequacy of the refined mathematical model to the physical processes in the discharge channel and closed discharge chamber over a wide range of system parameters is substantiated by comparison with experimental data. The resulting relationships significantly improve the adequacy of the previously developed mathematical model to the physical processes occurring during a discharge in water and expand the range of parameters over which it can be used.
The utilization of corrosion inhibitors offers a cost-effective strategy to reduce corrosion in metal samples. There is a growing focus on developing inhibitor formulations that are both economical and environmentally friendly, emphasizing traits like biodegradability and affordability. Plant extracts, such as those from Azadirachta indica, commonly known as neem, have gained attention for their potential as corrosion inhibitors. This review highlights the inhibitory effects of various neem extracts, including neem seed oil, gum, and leaves extracts, on different metals and alloys. Neem extracts contain biocidal compounds like azadirachtin, which enhances their inhibitory effects, particularly in environments prone to biocorrosion. In summary, products derived from neem show promise as green corrosion inhibitors for a wide range of metal substrates, offering potential for use in corrosion protection applications.
An efficient, one-step method for formation of protective graphite ceramic coatings on light alloys (Al, Mg, Ti) has been developed. The method includes simultaneously high-frequency PEO-treatment and modification of ceramic coating with graphite formed in the electrolyte due to separation of dispersed particles from graphite counter electrodes under the action of plasma discharges and electroerosion. Studies of protective composite PEO-coatings obtained by the proposed method have shown that they are significantly superior in their performance properties to basic PEO-coatings not modified with graphite. Compared to basic PEO-coatings, the composite PEO-coatings had 10
The electroactivation of whey in continuous mode in electrolyzers with different configurations has been shown to be an important step in developing a wasteless technology for recovering whey proteins into protein–mineral concentrates. The flow mode of the whey and anode liquid; the electrolyzer configuration; variations in electrical and thermal parameters, pH, and redox potential; and biochemical changes in dry matter and protein composition have been demonstrated to be the key factors in scaling up the process to an industrial level. The specific energy consumption per unit volume of whey during whey processing in an EDC-3 electrolyzer, having a semicylindrical casing, has been found to be considerably lower than that during whey electroactivation in an EDP-2 electrolyzer, having a casing in the shape of a parallelepiped—which is due to the higher capacity of the former electrolyzer and the higher calcium ion concentration—but almost twice that in the case of whey processing in an EDP-5 slot-type electrolyzer. The study of the changes in the above-mentioned parameters during whey electroactivation led to the development of a slot-type electrolyzer with a semicylindrical casing for whey processing in continuous mode.
The possibilities of plasma-electrolyte treatment technology and equipment for obtaining electrolyte suspensions with graphene particles by exfoliation of graphite electrodes were studied. The regularities of graphite exfoliation in the anode-cathode processes of plasma-electrolytic treatment were established. It was found that the electrical modes of the technological alternating current source allow producing the electrolyte suspensions with graphene particles with varying degrees of defectiveness through the plasma-chemical exfoliation of graphite: from multilayer graphene particles (the cathode pulse mode) to graphene oxide particles with varying degrees of functionalization (the anode and intermediate modes). It has been established that plasma-electrolytic exposure of highly textured pyrolytic graphite, unlike polygranular graphite, causes the electrode to swell more than tenfold. It is shown that plasma-electrolytic treatment of synthetic graphites is highly effective for obtaining electrolyte suspensions with graphene particles.
The study addresses the modeling of the characteristics of electric and magnetic fields generated simultaneously through conduction, by directly passing current through the melt using electrode current leads, and induction, using an external inductor positioned above the surface of the melt. This hybrid method of energy treatment for a liquid metal system implements a complex superposition of electromagnetic fields, which determines the parameters of the thermal-force impact on the treated object. The functional capabilities of this method were analyzed through numerical experiments using simulation modeling. The obtained results demonstrated potential treatment modes capable of actively enhancing the incubation processes of crystallization, which ultimately allows one to find conditions for improving the structure and properties of the cast metal. Thus, the combination of simultaneous conduction and induced current treatment modes consistently led to a stronger impact on the liquid metal system compared to applying them separately. It was found that the genesis of the electromagnetic field superposition is mainly concentrated within the skin layer near the melt surface. The time characteristics of the electric and magnetic fields become nonlinear, which amplifies energy fluctuations within the system. At the same time, the amplitude values of the combined electromagnetic field characteristics increase by almost an order of magnitude, significantly enhancing the integral amplitude of the force impact on the melt. Thus, the simulation modeling results confirmed the innovative potential of the hybrid method of treating the melt simultaneously with conduction and induced currents for foundry applications.
—The paper presents experimental results on the preparation of samples with colloidal CdSe quantum dots (QDs) of various sizes by thermal synthesis from organic solvents and the fabrication of CdSe/PEPC (PEPC—poly-N-epoxypropylcarbazole) polymer nanocomposites (NCs) based on them. The QDs are characterized indicating their size calibration and are characterized by absorption in the infrared and visible ranges of the exciton energies of the absorption maxima. The same exciton maxima as QDs in CdSe are clearly visible in the NC QDs. The obtained results are also explained by the energy transfer from the PEPC polymer matrix to the QDs. The transparency properties of QDs in the NC systems in the visible and infrared ranges suggest their application in optoelectronics, biochemistry, etc. The use of such materials will expand the spectral range of luminescence and increase its intensity based on the processes of energy and electron transfer in atomic-type QDs.
Recently, metal-ceramic composites with an amorphous matrix have attracted special attention of researchers. In this work, composite coatings made of Fe-based metallic glass reinforced with titanium diboride (TiB2) were prepared for the first time. For this purpose, the method of electrospark deposition with a nonlocalized electrode consisting of iron granules, TiB2 powder, and amorphizing powder in various ratios was used. The thickness of the prepared composite coatings on 45 steel ranged from 37 to 44 μm. It was shown that the coating structure contains TiB2 particles, the maximum concentration of which is achieved at a titanium diboride to multicomponent powder ratio of 1 to 5. The surface roughness of the coatings had close values of 8.3–8.8 μm. It was found that the wetting angle of coatings reinforced with TiB2 with distilled water changes from 80.4° to 91.4°, whereas the hydrophobicity of the amorphous coating without TiB2 was higher (95.4°). It was found that reinforcing the amorphous coating with TiB2 allows increasing its microhardness from 10.0 to 12.5–14.65 GPa. The average values of the friction coefficient of coatings ranged from 0.76 to 0.58. The coating with the highest concentration of titanium diboride had the highest wear resistance. Its use allows reducing the wear of parts made of steel 45 almost ten times. It has been established that reinforcement of the amorphous coating with TiB2 according to the proposed method does not worsen its oxidation resistance. In general, the use of the developed coatings allows a 13- to 20-fold increase in the oxidation resistance of products made of steel 45 at 700°C.
A comprehensive study of silicon containing nanoclusters of impurity atoms (Ni, Mn, Cr, Gd, Eu, Se) has revealed a number of unique physical phenomena uncharacteristic of classical semiconductors. It has been established that cluster structures in the silicon crystal lattice ensure the stability of electrophysical parameters over a wide temperature range and high radiation resistance to γ- and electron irradiation. It has been shown that, at Ni cluster concentrations ≥1015 cm–3, the generation of thermal donors and radiation defects is suppressed without altering the conductivity type. Impurity atoms with unfilled d- and f-shells (Mn, Cr, Gd, Eu) have been found to form ferromagnetic states in silicon, controllable by an external magnetic field at room temperature. Multicharged Mn nanoclusters were found to create localized energy levels within the forbidden bandgap, explaining the observed negative magnetoresistance and impurity absorption with an edge at 0.2 eV. For selenium-doped silicon, the possibility of creating pulse generators with frequency modulation suitable for detecting monochromatic radiation has been demonstrated. The study of binary compounds in the silicon lattice confirmed their stability and potential for developing materials with controllable photoelectric, optical, and magnetic properties.
Gamma irradiation experiments were conducted to investigate the potential for improving the electrical properties of pure high-density polyethylene (HDPE) and an HDPE/α-Fe3O4 polymer composite. Changes in permittivity ε', loss tangent tan δ, and AC conductivity σac were studied in alternating fields for unirradiated and irradiated composites in the frequency range from 25 Hz to 1 MHz at room temperature. The irradiation dose ranged from 0 to 300 kGy. The conductivity versus AC frequency is directly proportional to the frequency. The study of dielectrics determined that, with an increase in the gamma-radiation dose, the relative permittivity and loss tangent increase, whereas the relaxation time of the segmental dynamics of the polymer chain decreases for all composites. The crystal structure and surface morphology of unirradiated and irradiated films were studied using a PANalytical EMPYREAN X-ray diffractometer and a JEOL JSM-6490LV scanning electron microscope.
This study focuses on the production and characterization of titanium dioxide (TiO2) nanoparticles (NPs) fabricated using an environmentally friendly technique, emphasizing their potential use in electrochemical biosensors. Knowledge of the physical and electrochemical properties of the NPs, such as their crystalline phases, shape, electrical conductivity, surface characteristics, and charge transfer resistance, is critical for enhancing their biosensor performance. Those properties were analyzed using ultraviolet-visible absorbance, X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The study also explored functionalization options for improving the interaction between TiO2 surfaces and target analytes, increasing the overall efficiency of electrochemical sensors. The results showed that the synthesized particle size was 22 nm, indicating an increase in the surface area, allowing the glassy carbon/TiO2-modified electrode to store input energy and then discharge, similar to a capacitor. Furthermore, the glassy carbon/TiO2-modified electrode demonstrated high sensitivity and stability. The findings suggest that environmentally synthesized TiO2 NPs can markedly accelerate the development of reliable and effective biosensing systems.
The influence of irradiation with γ-quanta on the current transport mechanism in the Al/p-CdTe/Mo structure was investigated. X-ray powder diffraction analysis determined the real structure of this material as Al/n-Al2O3/p-CdTe/n-MoO3/Mo. In its final form, it is represented as n+–p–n, where the base (p-CdTe) is in contact on both sides with wide-bandgap thin oxide layers of n-Al2O3 and n-MoO3 so that the n+–p junction is ideal and the p–n junction is nonideal. Upon the application of reverse bias (when a positive (+) voltage is applied to Al and a negative (–) to Mo), minority nonequilibrium charge carriers accumulate near the ideal contact, which results in an extended sublinear region in the reverse current–voltage characteristic of the structure before and after irradiation. This is explained within the framework of the theory of injection depletion effect by the injection of electrons from the rear junction n-MoO3/p-CdTe and by the emergence of diffusion and drift currents directed toward each other in the base of the structure. The shape and length of the sublinear region are preserved because of the high value of the frontal–ideal potential barrier n+–p, while in the range of various irradiation doses Φ (106, 107, 108, and 109 rad), the distribution profile of nonequilibrium charge carriers in the base of the structure remains virtually unchanged.
In this work, a new derivative of chalcone, i.e., 4-(2-(naphthalen-1-yl)vinyl)-N,N-diphenylaniline, was synthesized and subsequently characterized by FTIR, UV–Vis spectroscopy, 1H-NMR spectroscopy, and mass spectrometry. The compound antimicrobial activity was evaluated. The compound showed a moderate to strong inhibitory action towards a selection of Gram-positive (S. aureus, S. epidermidis), Gram-negative (Klebsiella spp., and E. coli), and fungal (Candida albicans) species, and its activity increased at higher concentrations. The compound electronic structure, molecular orbitals, and vibrational properties were studied using DFT and TD-DFT calculations. The bioactivity exhibited was explained by the proposed charge transfer mechanism evinced by the HOMO-LUMO energy gap and a dipole moment as well as the bioactivity exhibited by the studied compound. This is the chalcone derivative potential applications in electrophysiology. The chalcone derivative is a promising candidate for further study as an antimicrobial surface-active agent or as a functional material in electrochemical devices and coatings, as suggested by the synergy between experimental and theoretical data matching.
The emission spectra of isolated guanine molecules have been obtained in the 250–500 nm wavelength range due to excitation by a beam of slow electrons. At a beam energy of 100 eV, nineteen spectral bands and lines have been observed in the spectrum. It has been shown that the guanine emission spectra are caused by processes of dissociative excitation of molecules, dissociative excitation with ionization, and by the primary excitation of the electronic levels of guanine. The biophysical implications of the obtained results are discussed.
The paper presents the results of using plasma electrolytic treatment for sulfiding of carbon tool steel. The steel surface was saturated with sulfur in an electrolyte based on ammonium sulfate and dimethylsulfoxide at 550°C. Before and after diffusion saturation, various types of heat treatment were applied: quenching from 780°C after sulfiding, tempering before and after saturation from 780°C. An analysis of the structural and phase changes in the sulfided surface revealed the formation of FeS, Fe3S4, and Fe2S3 iron sulfides, the amount of which is determined by the use of heat treatment before and after saturation, and the formation of martensite after quenching and Fe3O4 oxides as a result of high-temperature oxidation. Tribological tests were conducted in the dry friction mode using the “shaft-bushing” scheme under a load of 10 N and the sliding speed of the sample on the counter body of 1.555 m/s per 1000 m of the friction path. An increase in weight wear after plasma electrolytic sulfiding with quenching was found to be 17 times greater than that of an untreated sample, 13 times greater than that of water- and oil-quenched samples, and 14 times greater than that of tempered samples. The wear resistance of sulfided steel was determined by the structure of the deformation zone material during friction, containing iron sulfides.
А possibility is shown of using plasma electrolytic polishing as a technology for postprocessing of additively manufactured alloy products, which ensures a change in the surface microrelief as a result of anodic dissolution and the action of pulsed spark discharges, removal of unmelted powder particles adhesively bound to the substrate from the surface, and a decrease in its roughness and an accompanying increase in wear resistance. Polishing was carried out under conditions effectively shown for treatment products made of titanium alloys obtained by the traditional method. An aqueous solution at 80°C based on ammonium fluoride with the addition of citric acid and pyrocatechol as complexing agents was used as an electrolyte. It was found that treatment at a voltage of 300 V for 20 min reduces the height roughness parameters Ra and Rz by an order of magnitude. Tribological tests were conducted in the dry friction mode using the shaft-bushing scheme under a load of 10 N. At a sliding speed of the sample on a counter body made of hardened tool steel of 1.555 m/s per 1000 m of friction path, there is a decrease in weight wear by 1.8 and 1.9 times and the friction coefficient by 10 and 42
The article presents the results of experimental studies of heat transfer during boiling of a dielectric fluid in an electric field on modified surfaces obtained by electrospark alloying. The influence of the electric field strength, electrode shape, interelectrode distance, heat-transfer surface material, roughness parameters, and other factors on the heat-transfer characteristics and the development of the boiling process was studied. A comparative analysis of the influence of the electric field and structural modification of the heat-transfer surface on heat-transfer intensity is presented. Heat-transfer intensification achieved was up to 3.5 times higher compared to that at boiling on a smooth surface in the absence of a field. Based on visual observations and high-speed filming, the mechanism of boiling in an electric field on modified surfaces is discussed.
This study investigates the effect of ultrasonic-assisted interval time on the microstructure and electrochemical corrosion properties of Watts-type nickel coatings prepared by electrodeposition. To address challenges such as coarse grains and porosity caused by concentration polarization during traditional direct current plating, ultrasonic intervals of varying durations were introduced. The surface morphology, crystallographic orientation, grain size, and corrosion resistance were analyzed using scanning electron microscopy, X-ray diffraction, and electrochemical techniques. Results reveal that continuous ultrasound and short-interval pulsing promote (220) texture and yield finer grains, with sample #3 exhibiting the strongest (220) orientation and smallest grain size. Longer intervals shift the preferred orientation to (200), enhance coating compactness and improve thermodynamic stability (higher open-circuit potential), but do not necessarily result in better corrosion resistance. Notably, sample #1 demonstrated the lowest corrosion current density and a balanced polarization resistance, indicating the best overall electrochemical protection. This study highlights the importance of ultrasonic interval tuning to balance structural and electrochemical properties in functional nickel coatings.
The temperature dependence of the electrical conductivity of composites based on magnetic particles and bentonite has been systematically investigated. The results indicate that the activation energy of charge carriers is strongly dependent on the particle sizes of the composites based on bentonite and magnetic particles. That behavior is attributed to quantum size effects within the particles. Furthermore, the influence of the magnetic particle size on the magnitude of magnetoresistance and the value of magnetic permeability in the studied samples has been established.
