Том 55, № 2 (2019)

It is shown that an earlier-suggested method of computing isotherms of adsorption of vapor mixtures in a sample pore of active carbon using molecular dynamics can be applied for quantitative computation of adsorption isotherms of components of binary gas mixtures at temperatures higher than critical. It is shown that computed adsorption isotherms of mixture components in micropores and on graphene surfaces are quantitatively described by equations of the lattice model.

The TiO₂/kaolinite material—a filler for construction materials with the function of passive degradation of household organic pollutants—has been synthesized and its properties have been examined. Synthesis of the material has been performed under varied conditions: the amount of the reactive mixture and temperature of thermal treatment have been altered. Thereafter, the effect of the synthesis conditions on chemical composition, surface morphology, phase composition, adsorption parameters, and changes in the adsorption activity has been determined at irradiation by UV and visible light.

The electron structures of pure and oxidized aluminum surfaces at ambient temperature have been studied while analyzing the results of a simulation of optical conductance on the basis of optical experiments. It is established that oxidation of an aluminum surface in the solid state leads to splitting of the conduction band when it contains forbidden state regions. The heat of oxygen adsorption on aluminum stated has been determined on the basis of properties of surface states.

The catalytic activity of water-gas shift reaction catalyzed by Cu₁₂TM (TM = Cu, Ag, Au) cluster is analyzed by density functional methods with the PBE. The mechanism of the reaction is divided into the redox mechanism and formate mechanism. Compared with the carboxyl mechanism, it turns out that: Cu₁₂Au cluster performs the best catalytic activity in Cu₁₂TM (TM = Cu, Ag, Au) cluster whether proceeds through the three mechanisms. Interestingly, the initial catalytic rate of CO and the final CO₂ yield can be used to evaluate the catalytic activity of the mechanism. It is shown that catalyzed by Cu₁₂Au cluster, the redox mechanism is become competitive due to the lower ratio and high value of TOF. The carboxyl mechanism is another alternative pathway is found to be competitive. Our findings should be very useful for improving the catalytic properties for the industrially reaction.

On the basis of adsorption studies, the characteristics of formation of polyelectrolyte (PE) nanoadsorption layers of an aliphatic structure that creates a mineral–organic matrix on clay minerals and soils (kaolinite, montmorillonite, quartz sand, and gray forest and chernozem soils) surfaces have been revealed. It has been established that the polyacrylamide (PAM) and polyacrylic acid (PAA) adsorption limit values on all minerals are significantly higher than the calculated values for the single-layer formation. This indicates the surface adsorption of not only individual macromolecules, but also of secondary PE structures of types of bundles or fibrils determining the cluster-matrix structure of the modified surface. The study of the electric surface properties (electrophoretic mobility, electrokinetic potential, рН, and electroconductivity) of adsorption-modified PE suspensions of minerals and soils has corroborated that there are differences in the adsorption mechanism, ranging from physical to chemisorption with the formation of surface compounds, as a result of both differences between PE polar groups and the mineral type. It has been demonstrated that the mineral and soil surface modification by organic substances differently affects the dispersity, porosity, mean pore radii, total surface area, and pore volume in the direction of both an increase and decrease in size. Here, this results in significant changes in the differential pore volume and more homogeneous pore size distribution.

The electrochemical and power characteristics of the membrane electrode assemblies with PtCo/C, PtMn/C, PtZn/C, and PtNi/C cathode bimetallic catalysts, prepared from PtCo(CH₃СO₂)₄(СH₃СOОН), PtNi(CH₃СO₂)₄(СH₃СOОН), PtMn(CH₃СO₂)₄(H₂O), and PtZn(CH₃СO₂)₄(СH₃СOОН) bimetallic clusters, as a component of hydrogen–oxygen and hydrogen–air fuel cells, were studied. It is shown that various types of platinum-metal alloys with the ratio Pt : M = 1 : 1 (where M = Co, Ni, Mn, Zn) uniformly distributed over the surface of the support are formed after thermal degradation of the bimetallic clusters deposited on carbon black, and the catalyst grain size is 2–5 nm. The synthesized PtCo/C, PtMn/C, and PtZn/C catalysts are superior to a commercial platinum catalyst in terms of their high specific activity and, therefore, are promising for application in hydrogen–air fuel cells.

Magnesium oxide (MgO) is a versatile metal oxide with wide applications in electrical, chemical and pharmaceutical industries. Preparation of nano-MgO helps to enhance key physicochemical properties for optimal performance in industrial applications. In the present work, MgO nanoparticles were synthesized by magnesium nitrate precursor in ethanol. Different gelling agents were employed to investigate potential variations in the crystallinity and thermal behavior of the sol–gel product to control the nanoparticle’s size distribution. The crystal and thermal characteristics of the synthesized MgO nanoparticles were studied using X-ray diffraction (XRD) and Thermogravimetry-Differential Scanning Calorimetry (TG-DSC) analysis. The XRD data showed that all the samples demonstrated crystallinity except sample B which was amorphous. The TG-DSC characterization showed a three stage thermal decomposition for all the samples, leading to the formation of MgO nanoparticles. Based on the thermal analysis data, different calcination temperatures were selected to investigate their effects on stability, and the sample prepared with tartaric acid as a gelling agent and calcined at 500^oC demonstrated the smallest average particle size of 58.7 nm obtained from dynamic light scattering (DLS) analysis. Further, this sample was subjected to XRD, FTIR and TEM analysis which reveals that the calcination yielded impure, 30 nm sized spherical shaped, agglomerated MgO nanoparticles. Additionally, the physicochemical characteristics of the selected sample reveals that pure MgO nanoparticles with uniform morphology can be obtained via alteration of calcination time and heating rate.

Dynamic mechanical relaxation spectroscopy is used to study local dissipation processes of μ‑relaxation in a modified latex acrylate polymer in the negative temperature range taking into consideration their modification by different ionic phthalocyanines. Characteristic maxima of dissipation μ-relaxation losses due to a change in the polymer relaxation structure are observed.

A method for depositing electroactive coatings based on conductive polymers on a graphite foil has been developed. The electrochemical behavior of these electrodes has been studied. It has been shown that an anodic pretreatment of the graphite foil significantly improves the adhesion of the coatings to the foil surface and provides the formation of electroactive polymer coatings by the electrochemical oxidation of the monomer or by solution casting using a chemically polymerized monomer solution. The use of the modified graphite foil leads to an increase in the electrochemical capacitance of the electrodes and the coating stability.

Comparison of methods for modification of active carbon by fullerenes with and without a stabilizer is presented. The possibility of modifying active carbons using fullerenes by means of dispersing them using ultrasound in a water medium, which leads to increasing of protective power time of modified carbons by benzene vapors from humidified gas media as compared to initial adsorbent, is demonstrated. The sorption activity of materials in various dynamic conditions is estimated.

This paper explore the viability of novel microwave hybrid heating, Co-based coatings without CeO₂ (unmodified) and with CeO₂ (modified) in varying wt % (1, 2 and 3 wt %) were developed. The coatings were developed using domestic microwave oven of 2.45 GHz frequency, 900 W power and an irradiation time of 15 min. The characterization of unmodified and modified clads has been done in terms of microstructure, XRD, hardness and sliding wear behavior. The influence of sliding speed (1.2 and 2.4 m/s) and distance (3000 and 6000 m) on wear behavior were investigated. It was noticed that the wear resistance of coatings containing 1wt % of CeO₂ was higher than other coatings. Further, it was found that modified coating with optimum addition of cerium oxide (1wt % CeO₂) refined the microstructure, promotes the formation of hard carbides CeC_2, Cr₂₃C₆ and Cr₇C₃, enhanced microhardness to 17% as compared to unmodified.

The stabilizing effect on the resistance to ozone aging of polydieneurethane elastomers of new compositions based on polyfluorinated alcohol immobilized on a montmorillonite “carrier” introduced into the polymer at the stage of its preparation was studied. Structural and morphological features of the surface of elastomers were studied by Fourier transform infrared spectroscopy and electron and atomic force microscopy. It was revealed that intercalation of macromolecular chains of the matrix polymer is observed in the intralayer spaces of fluorine-containing organoclay with an increase in the degree of structural perfection of the macromolecular system, contributing to an increase in the ozone resistance of the obtained fluorine-containing materials.

A novel method of electrochemical synthesis of yttrium aluminum garnet (YAG: Al₅Y₃O₁₂) is successfully developed in the mixture of YCl₃ and AlCl₃ aqueous solution. The electrosynthesized YAG are further annealed and characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Ppy/YAG thin film is formed electrochemically on the surface of the stainless steel (SS). The anti-corrosive behavior of polypyrrole films in the presence of YAG nanoparticles synthesized by electropolymerisation on stainless steel (SS) electrodes have been investigated in artificial sea water solutions using potentiodynamic polarization and electrochemical impedance spectroscopy. The undoped polypyrrole synthesized in the presence of YAG nanoparticles coated electrodes offered a noticeable enhancement of protection against corrosion processes. Facile synthesis of YAG and Ppy/YAG nanocomposite and more efficient protection effect of nanocomposite film are main important novelty of the presented work.

Bitter leaf and Fenugreek seed oils were extracted from their parent seed plants for use as corrosion inhibitors for mild steel in HCl. Corrosion measurements were taken at a time interval of 72 h. The Fenugreek seed oil gave 90% efficiency with a regression coefficient of 0.99 in terms of its ability to resist HCl corrosion, while the bitter leaf oil extract gave a corrosion inhibition efficiency of 87% with a regression coefficient of 0.84. Based on analyses, the adsorption of the extracts to mild steel obeyed better, the Langmuir adsorption isotherm. From the calculated ∆Gs, the adsorption of Fenugreek and bitter leaf oils on the surface of the mild steel as corrosion inhibitors, were found to be clearly descriptive of physiosorption and chemisorption respectively. Furthermore, the FLE and BLE adsorption behavior on the mild steel can be described as that of mixed-type inhibitor. Based on the phytochemical test conducted, the better performance of the FLE relative to the BLE may be as a result of terpenoids which are present in the FLE.

A method for detection of causative agent of tularemia in aqueous solutions by surface plasmon resonance spectrometry was proposed. The kinetics of immobilization of antibodies to Francisella tularensis on the surface of gold-plated glass chips was studied. Based on a quantitative analysis of the results, it was concluded that the antibody molecules were predominantly laterally oriented on the surface. This conclusion was confirmed by analysis of sensorgrams of the subsequent antigen–antibody interaction. It is shown that the proposed method can reliably determine the presence of the causative agent of tularemia in aqueous solutions with a sensitivity of 1.0 × 10² cell/mL for several minutes. Various options for improving this method for detection of the tularemia causative agent to increase its sensitivity have been proposed.