Том 92, № 7 (2019)

Technological aspects of the formation of wear- and corrosion-resistant coatings on aluminum alloys and steel via an integrated use of methods of the low-temperature heterophase transfer, microarc oxidation, and magnetron sputtering. The tribological and anticorrosion properties of the coatings developed were estimated.

Chemical precipitation from aqueous solutions of silver nitrate and sodium sulfide in the presence of sodium citrate as a stabilizer was used to synthesize powders and colloidal solutions of silver sulfide Ag₂S. The methods of X-ray diffraction, dynamic light scattering, and low-temperature adsorption of nitrogen were used to estimate sizes of silver sulfide particles in the precipitated powders and colloidal solutions. Changing the ratio between the reagent concentrations in reaction mixtures made it possible to obtain Ag_2S nanopowders with average particle sizes within the range from ∼1000 to 40–50 nm. The size of Ag_2S nanoparticles in the colloidal solutions obtained is 15–20 nm. The relationship between the particle size of silver sulfide and the supersaturation of solutions used for synthesis was considered.

To enhance the compactness of the chemically bonded phosphate ceramic coatings (CBPCs), different inorganic curing agents (MgO, CaO, and ZnO) are selected as the reinforcement. Tribological experiment and the analysis of microstructure, phase characterization and mechanical performance are carried out to clarify the mechanism of different curing agents on the effect of wear performance. It is found that the curing agents place a significant role on the wear performance of the coating. Compared with coating without curing agents, more bonded phase (AlPO₄) can be detected when curing agents (MgO, CaO) are used, which is mainly resulted by the high heat release from MgO and CaO related reactions, and this released heat energy enhances the formation of AlPO₄. The results indicate that the morphology and tribological performance of CBPCs using different kinds of curing agents are dependent on the weight ratio of AlPO₄ to α-Al₂O₃ (defined as RPA). The suitable value of RPA will not only improve the bonding strength among the ceramic particles, but also decreases the quantity of defects (such as pores). Upon the above results, CBPCs with MgO process superior wear resistance due to their dense and uniform microstructure.

Conversion of oxygenates to aromatic hydrocarbons in the syngas medium in the presence of a commercial zeolite-containing catalyst was studied. The influence of pressure on aromatization of dimethyl ether and ethanol was examined. At 400°C, an increase in the pressure from 0.1 to 3.0–10.0 MPa leads to a sharp increase in the yield of aromatic compounds. Dimethyl ether and ethanol, which are isomers belonging to different classes of compounds, were compared as substrates in conversion to aromatic hydrocarbons. At elevated pressure, dimethyl ether compared to ethanol exhibits higher selectivity in formation of the desired synthesis products, allowing synthesis of liquid hydrocarbons with increased content of arenes.

In this paper, the ZSM-5 zeolite base is used to produce light olefins in the process of converting ethylene to propylene, as well as copper oxide to improve the catalyst. After loading the copper oxide by inoculation, the modified catalyst was investigated for accurate determination of the specification by XRD, SEM, BET, and FTIR analyzes. The activity of this catalyst was evaluated in the process of ethylene to propylene conversion in a constant reactor under operational conditions (temperature 400°C, pressure 1 atm, and feed flow rate of 0.5 cc min⁻¹ of pure ethylene), which also shows the results of tests of catalyst activity evaluation The modified catalyst of selectivity of ethylene and propylene will increase as the temperature rises and the maximum selectivity table at 400°C will be achieved.

The surface of a carbon sorbent modified with poly-N-vinylpyrrolidone was studied by X-ray photoelectron spectroscopy (XPS). The modification involves polymerization of N-vinylpyrrolidone on the carbon sorbent surface to form poly-N-vinylpyrrolidone. The elemental composition of the carbon sorbent surface before and after modification was determined by XPS. The electronic state of atoms of the identified elements on the surface was evaluated. The contact of the modified carbon sorbent with normal saline simulating the biological medium leads to partial removal (desorption) of the polymer from the granulated sample.

A procedure was developed for preparing poly(methyl methacrylate) nanoparticles of 15–50 nm size from coarser (200–300 nm) polymer latex particles prepared by emulsifier-free emulsion polymerization. The hydrodynamic radii of the macromolecules in the t-BuOH (85 vol %)-H₂O (15 vol %) mixture at 30°C and in the i-PrOH (80 vol %)-H₂O (20 vol %) mixture at 25°C were determined by dynamic light scattering: R_h = 5.94 × 10⁻²M_w^0.3733 (R² = 0.9525) and R_h = 2.12 × 10⁻²M_w^0.4641 (R² = 0.9673), respectively.

The reaction of 1,1,1,2-tetrafluoroethane with fluorine in a gas-liquid reactor with a high-speed stirrer and with perfluorodecalin or perfluoro-1,3-dimethylcyclohexane as a liquid phase occurs as hydrogen substitution without noticeable cleavage of C-C bonds, yielding penta- and hexafluoroethane. The fluorination of methane in perfluorodecalin under the same conditions yields, depending on the methane and fluorine concentrations in their mixtures with an inert gas, products of successive hydrogen substitution by fluorine when the reaction occurs in approximately isothermal mode and products corresponding to the thermodynamic equilibrium when the reaction occurs in the mode of gas-phase diffusion combustion on the gas bubble scale.

The quercetin molecularly imprinted polymer microspheres were prepared by reversible addition-fragmentation chain transfer free radical polymerization combined with precipitation method (RAFTPP) with the dibenzyl trithiocarbonate (DBTTC) as RAFT reagent and quercetin as template molecule. The effects of solvents and cross-linking agent on the morphology and size of polymers were investigated, and the polymers were preliminarily screened by scanning electron microscope. The adsorption experiment and adsorption model analysis were carried out on the molecularly imprinted polymers (R-MIP) prepared under optimal condition and on the molecularly imprinted polymers prepared with a traditional precipitation polymerization (T-MIP). Consequently it was determined that, QR-MIP max was 37.71 mg g⁻¹ and QT-MIP max was 29.61 mg g⁻¹. The results showed that the R-MIP had a good adsorptive property and was obviously superior to T-MIP. R-MIP was used as solid-phase extraction filler in combination with the HPLC method to conduct enrichment, separation and measurement of the quercetin in honeysuckle and clove leaves, which effectively removed the matrix interference and the recovery rate of this method was 93.8–102.9%.

Hybrid nanocomposites based on poly(3,6-di(3-aminophenyl)amino-2,5-dichloro-1,4-benzoquinone) and single-walled carbon nanotubes were obtained under monomer polymerization conditions in concentrated formic acid under the action of benzoyl peroxide in the presence of single-walled carbon nanotubes. The electrochemical behavior in an aprotic lithium electrolyte of composite electrodes having the form of strips of anodized graphite foil having on its surface an active layer of a stable suspension of the nanocomposite in formic acid was examined in the absence of any binding and electrically conducting additives. The specific electrochemical capacitance of the coating reaches a value of 500 F g⁻¹ at a charge-discharge current of 1.5 mA cm⁻² in an inorganic electrolyte composed of 1 M LiClO₄ in propylene carbonate. It was found that the Faraday pseudo-capacitance makes an insignificant contribution to the electrochemical capacitance of composite electrodes, which is mostly determined by the charging of an electric double layer. The nanocomposite coatings are characterized by high stability of their electrochemical characteristics at a coulomb efficiency of 97–100%. The fall of the capacitance upon prolonged cycling (>300 cycles) does not exceed 4%. The electrochemical characteristics of electrodes on friable substrates of anodized graphite foil strongly surpass those for electrodes obtained on nickel or rolled graphite foil as substrates.

Structural changes in a promising cathode material LiNi_0.8Co_0.1Mn_0.1O₂ for lithium-ion batteries were in situ studied by X-ray diffraction analysis in the course of electrochemical reactions. The Rietveld method and TOPAS 5 software package were used to examine changes in the unit cell parameters of LiNi_0.8Co_0.1Mn_0.1O₂ and the reasons for these changes. It was found that the unit cell volume increases by 2% relative to the discharged state (2.7 V) upon charging to 4.2 V.

Results are presented of experimental studies of the conversion of products formed in gasification of wood, peat, coal-wastes, and shale rock via the partial oxidation by air in a flow-through filtration converter filled with various kinds of porous packing. Charcoal ZPS zeolite and Raschig porcelain rings served as a packing. It was possible to experimentally select for all kinds of packing the modes in which the combustion heat of the conversion products is not lower than that of the starting gaseous products. The conversion of pyrolysis tars was 60–85% and depended insignificantly of the type of a packing. The experimental results were compared for products formed in gasification of wood and coal waste with the data calculated in terms of the thermodynamic conversion model. The satisfactory correspondence between the results of a thermodynamic calculation and experimental data was obtained for products formed in gasification of wood, in which the content of pyrolysis tars is rather high.

Reactions of commercial polychlorobiphenyl mixtures with alkali in polyalkanolamines were studied. The major reaction products are hydrophilic mixtures of hydroxy derivatives of polychlorobiphenyls. The highest conversion of commercial polychlorobiphenyl mixtures was reached when using 2-aminoethanol. This reaction can be used as the step of pretreatment of technogenic waste prior to microbiological degradation.