Vol 90, No 5 (2017)

Published data on the phase diagram, thermodynamic properties, and electrochemical behavior of the sodium–sulfur system are considered. The use of this system in rechargeable chemical current sources (batteries) at different temperatures is discussed.

High-temperature electrochemical synthesis and currentless transfer in molten salts were used to obtain coatings constituted by carbides of refractory metals (Mo₂C, Cr₇C₃, NbC, and TaC). It was found that the Mo₂C/Mo composite synthesized from a chloride-carbonate-molybdate melt has the highest catalytic activity. It was shown that the Mo₂C catalytic coating preserves its properties for at least 5000 h of tests. The protective properties of refractory metal carbides of composition Cr₇C₃, NbC, and TaC significantly improve the corrosion resistance of steel articles in concentrated solutions and raise their wear resistance by an order of magnitude.

Working conditions and the concentration regions of the joint precipitation of PbS and CdS at which substitution solid solutions Cd_xPb_1–x can be formed were determined by calculation of ionic equilibria in the citrate-ammonia reaction mixture at 298 and 353 K with consideration for the conversion fractions of lead and cadmium sulfides into the corresponding sulfides. The hydrochemical precipitation onto glass-ceramic substrates was used to obtain Cd_xPb_1–xS (0 < x ≤ 0.149) solid solution films with thicknesses of 0.5 to 1.7 μm and high supersaturation with the substituting component. All the films crystallize to form the B1 structure. The phase and elemental compositions and morphological specific features of the films were studied. It was shown that the thickness of the deposited layers is most strongly affected by the process temperature, ammonium hydroxide concentration, and relative amounts of the metal salts in the reaction mixture. It was found that there are oxygen and chlorine in the Cd_xPb_1–xS solid solutions, and the distribution of these elements across the layer thickness was determined, with the layer-by-layer distribution of chlorine having a pronounced oscillatory nature. It was shown that, as the chemical precipitation temperature is raised, the content of CdS in the substitution solid solutions grows exponentially. The activation energies Ea.ic of the lead and cadmium interchange in the PbS crystal lattice were found to be, depending on the initial concentration of the lead salt, 75.3, 42.8, and 22.2 kJ mol^–1.

The method of laser ablation of a target, followed by condensation, was used to obtain a weakly aggregated BCSO nanopowder from barium cerate. The dispersity, fraction composition of the nanopowder, electrokinetic potential of its nonaqueous dispersions, and electrokinetic parameters of the electrophoretic deposition process were determined. An ultrasonic treatment produced a stable suspension of the BCSO nanopowder in a mixed isopropanol–acetyl acetone medium (70/30 vol %). The suspension is characterized by a high and positive ζ-potential of +30 mV. The electrophoretic deposition onto a dense model cathode was used to obtain thin-film BCSO coatings that are of interest for the technology of solid-oxide fuel cells. The phase composition of the coating was examined. It was found that the successive annealings of the nanopowder at temperatures of 800–1400°C make it possible to reduce the content of unidentified crystalline phases in BCSO to trace levels (< 5 vol %).

Two methods (spraying and calendering) for fabrication of supercapacitor electrodes are considered. Results of tests of double-layer capacitors with aqueous (sulfuric acid) and organic (tetraethylammonium tetrafluoroborate dissolved in acetonitrile) electrolytes and electrodes fabricated from activated carbon are presented. It is shown that, depending on the type of the electrolyte, it is necessary to use different methods for fabrication of carbon electrodes.

The effect of catalysts on the yield of products formed in thermal treatment of wood in the filtration combustion mode was experimentally studied. Natural zeolite of TsPS brand and K₂CO₃ were used as catalysts. The products were analyzed and the results were compared with those for noncatalytic systems. With the catalysts, the combustion temperature decreased by 100–200°C. The yield of liquid products formed in wood pyrolysis decreased with increasing amount of a catalyst in the mixture, and the appearance of unburned carbon on catalyst particles was also observed.

A study of the catalytic activity of modified zeolites in the reaction of selective oxidative dehydrogenation of cyclohexane and methyl cyclohexane demonstrated that catalysts prepared on the basis of natural clinoptilolite modified with Cu²⁺, Zn²⁺, Co²⁺, and Cr³⁺ cations exhibit the highest activity in the reactions under consideration. Principles to be used when selecting high-efficiency catalytic systems for the reaction of oxidative dehydrogenation of alicyclic hydrocarbons to the corresponding dienes are formulated.

It was found that the solution composition, pH value, concentration, and nature of surfactants and flocculant affect the process of electroflotation extraction of copper hydroxide in the presence of an excess amount of ammonia. A relationship between the ζ-potential of the dispersed phase and the degree of copper extraction was found. It is shown that a cationic surfactant and flocculants positively affect the efficiency of the electroflotation extraction of copper. Under the optimal conditions, the degree of the electroflotation extraction reaches values of 95–96%, and that with additional filtration, 97–99%. A technological scheme for implementing the electroflotation process is suggested.

The phase diagrams of the Zn(PO₃)₂–Ca(PO₃)₂ and Zn(PO₃)₂–Ni(PO₃)₂ systems were studied, and the double phosphates CaZn(PO₃)₄ and NiZn(PO₃)₄ were allocated. The anions of these compounds are chain polyphosphates with PO₄ tetrahedra in the period of identity. The structures and mechanism of the action of these compounds as additives to lubricants were described using quantum-chemical analysis. Improvement of the physicochemical and tribotechnical characteristics of lubricating materials containing these phosphates compared to the traditionally used lubricating materials was confirmed in tribotechnical tests.

Monomeric and polymeric organosilicon derivatives of 1-acetylguanidine, which exhibits sorption properties, were synthesized. The organosilicon polymers prepared were studied as sorbents for heavy [Hg(II)] and noble [Ag(I), Au(III), Rh(III), Pd(II), Pt(IV)] metals. They actively take up platinum group metals and exhibit metallochromic properties by analogy with the starting compound, 1-acetylguanidine. Their interaction with all the elements studied is accompanied by coloration. The initial monomers exhibit similar metallochromic properties.

Polyfunctional anion exchangers based on aniline, epichlorohydrin, and some polyamines were synthesized. The composition and structure of the anion exchangers were studied by IR spectroscopy and elemental analysis. Molybdenum sorption was studied by classical polarography, and dependences of the sorption of molybdenum(VI) ions on the solution acidity, concentration of metal ions, and time of contact of the resins with the Na₂MoO₄ solution were determined in batch experiments. These ion exchangers exhibit high performance in sorption of molybdenum ions. The developed sorbents with increased sorption ability can successfully solve problems of removing molybdenum(VI) ions from process effluents in nonferrous metallurgy.

The influence exerted on the supramolecular structure and properties of polycaprolactam by new composites based on 1,1,5-trihydroperfluoro-1-pentanol immobilized on montmorillonite support, introduced into the polymer melt, was studied. As found by electron microscopy and X-ray diffraction analysis, the layered structure of the fluorinated organoclay undergoes delamination in the bulk of the polymer matrix with the formation of an exfoliated nanocomposite. The modifier exerts a complex effect on the caprolactam structure, consisting in changes in the size of supramolecular formations and redistribution of the fraction of α- and γ-crystalline forms, which favors enhancement of the thermal oxidation resistance of the material.

The dependence of the physicomechanical properties of epoxy nanocomposites subjected to heat and humidity aging on the type of covalently functionalized carbon nanotubes and on the uniformity of their distribution in the epoxy matrix was studied. Two types of carbon nanotubes were used: those modified with carboxy and amide groups. The elastic modulus, bending deflection, and ultimate bending strength for the initial epoxy nanocomposites with carbon nanotubes and for those subjected to heat and humidity aging were determined. The epoxy binders modified with carboxylated carbon nanotubes are more resistant to the action of aging factors. The presence of aggregates of carboxylated carbon nanotubes in the epoxy matrix positively influences the preservation of physicomechanical properties of the composite subjected to heat and humidity aging. Microscopic examination revealed structural features of the epoxy nanocomposite and their effect on the resistance of the composite to the heat and humidity aging.

A new type of Ce-promoted Ni catalyst with KIT-1 as the support is prepared by using a sol-gel method. The catalyst exhibits excellent catalytic activity and superior stability in CO₂ reforming of methane (CH₄/CO₂ reforming) reaction. Effects of CeO₂ and KIT-1 with wormlike pore structure on catalytic activity are investigated by N₂-physisorption, XRD, H₂-TPR and TG techniques. The results indicate that the wormlike pore structure of KIT-1 is in favor of the high dispersion of metallic particles, and the doping of CeO₂ promotes the dispersion of Ni particles on the surface of support, which inhibits the agglomeration and sintering of active particles in CH₄/CO₂ reforming reaction. Moreover, carbon deposition on the surface of the catalysts decreases obviously due to the introduction of CeO₂. Experimental results during CH₄/CO₂ reforming show that the catalyst presented better catalytic performance than other Ni-based catalysts at 700°C and a gas hourly space velocity (GHSV) of 32 L g_cat^–1 h^–1, which is attributed to better textural property of KIT-1, better dispersion of active species, and lower carbon deposition. Especially, 6% Ce-NiO/KIT-1 shows the best catalytic activity among the series of catalysts prepared in this experiment.

The EU-1 zeolite with Si/Al = 25 was synthesized by hexamethonium bromide as a template. The effects of crystallization time, synthesis temperature, and the pH of the synthesis gel on the structure and crystallinity of EU-1 zeolite were investigated. The synthesized EU-1 zeolite was characterized by X-ray powder diffraction, BET, Fourier transforms infrared spectroscopy, scanning electron microscope, and inductively coupled plasma. The most effective conditions for synthesis of EU-1 were identified as follow: synthesis time 72 h, temperature 200°C, pH of gel ≃ 13, and aging time of 12 h. The catalytic performance of this catalyst was investigated for meta-xylene isomerization reaction in a fixed bed reactor under the following conditions: pressure of 10 bars, the temperature of 380°C, feed space velocity of 3.35 h^–1 and 4 g of the EU-1 catalyst. In comparison to other reported catalysts our synthetic EU-1 showed good m-xylene conversion and high PX/OX ratio.