Vol 91, No 1 (2018)

Fundamental aspects and specific features were studied of how composite coatings with oxygen-containing compounds of manganese are formed on the surface of D16 alloy in the course of the microarc oxidation from a silicate-alkaline electrolyte in the anodic-cathodic mode with interrupted discharge. The influence exerted by the concentration of potassium permanganate in the electrolyte on the elemental composition, morphology, and structure of the coatings was examined. It was found that the coatings are promising as catalytically active and corrosion-protection systems.

Results obtained in a study of the properties of titanium- and aluminum-oxide nanocoatings synthesized by the method of molecular layering on the surface of quartz optical fibers are presented. It is shown that, as the thickness of a titanium-oxide layer on the edge surface of a light guide increases, a cyclic change is observed in the power reflected from the fiber edge under the action of laser light. Aluminum-oxide nanocoatings on the extended side surface of the sheath of quartz fiber improve its heat resistance and mechanical bending strength. The results made it possible to significantly raise the reliability and extend the functional characteristics of fiber-optic pressure, temperature, and vibration sensors based on modified fibers in their service under extreme conditions.

Changes of the structural characteristics and electrical properties of fibers based on polyoxadiazole (Arselon) upon a low-temperature thermal treatment in an inert atmosphere were studied. Extremal dependences of the conductivity of the fibers on treatment temperature were observed and a mechanism of this process was suggested. The X-ray diffraction parameters of the Arselon fibers were determined for the extreme states and practical recommendations were made for using a preliminary heating of the fibers.

Catalytic coatings based on the Ni–Al–Al(OH)₃ system with the addition of metal hydroxides Mg(OH)₂ and Ca(OH)₂ are obtained by the method of cold gas dynamic spraying. The TGA/DSC curves were constructed and analyzed. The optimal temperature for thermal treatment at 750°C was chosen, at which in the coating the complete decomposition of hydroxides into metal oxides is provided, which is confirmed by the results of chemical and phase analysis. It was established that the thermal treatment has a positive effect on the specific surface of the coating increasing it by 3.5 times.

Procedure for synthesis of heterogeneous polyoxometalate catalysts based on sodium vanadomolybdophosphate or sodium peroxo vanadomolybdophosphate and supported by AV-17-8ChS anion exchanger was developed, their synthesis was performed, and the catalysts were studied in the course of oxidation of ferulic acid with peroxyacetic acid. A chromato-mass-spectrometric analysis was used to determine the main oxidation products, the composition of which agrees with the suggested conversion mechanism of ferulic acid in the process under study. It was shown that the regeneration of a spent catalyst via treatment with peroxyacetic acid can restore its original activity.

The parameters of synthesis by the spray method of cathode materials Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ and Li_1.25Ni_0.12Co_0.12Mn_0.51O₂, differing in lithium content were studied. The phase and granulometric composition, the morphology of the powder particles obtained, as well as an influence of temperature, total metal concentration, and pH of the solution on the properties of powders of cathode materials were studied. The discharge capacities of the obtained materials reached 260 mAh g^‒1 in the range of 2.5‒4.8 V.

Cyclability of the Li|Li₇La₃Zr₂O₁₂ interface was tested by voltammetry under externally applied potential difference. It was found that the solid electrolyte synthesized in the study contains a minor amount of an impurity in the form of lithium carbonate. This impurity forms, when brought in contact with metallic lithium, carbon that pierces the whole volume of the ceramic separator and produces a channel for a flow of electrons through the material, which leads to a poor cyclability of the solid electrolyte. A possible way to solve the given problem is via a purposeful replacement of the carbonate in the intergrain space of Li₇La₃Zr₂O₁₂ with another crystalline or glassy plasticizer that possesses an acceptable unipolar lithium conductivity (no less than 10^–6 S cm^–1) and forms, when brought in contact with metallic lithium, no electrically conducting compound or a compound capable of reversibly intercalating/deintercalating lithium.

Electroflotation of poorly soluble lanthanum compounds from model solutions simulating with high accuracy highly concentrated industrial salt systems was studied. The influence of various kinds of microadditives (flocculants and surfactants; cationic, anionic, and nonionic) on the efficiency of the recovery of lanthanum compounds from highly concentrated salt solutions was examined. For each supporting electrolyte (chloride, carbonate, sulfate, oxalate, nitrate), additives intensifying the process and enhancing its efficiency were found. The mean size and ζ-potentials of the dispersed phase particles were measured to account for the degrees of recovery reached in lanthanum electroflotation. A design of an installation for lanthanum recovery, allowing solution processing on the commercial scale, was suggested.

Physicochemical properties of aqueous solutions of binary mixtures of lignosulfonates and sodium dodecyl sulfate were studied. Introduction of sodium dodecyl sulfate into solutions of high-molecular-mass lignosulfonates at certain ratios causes macrophase separation of the systems with the formation of loose precipitates. A synergistic effect of a decrease in the surface tension is observed in the mixed solutions. This effect increases with increasing lignosulfonate molecular mass and temperature. The revealed relationships are caused by hydrophobic interactions of hydrocarbon radicals of sodium dodecyl sulfate with hydrophobic segments of lignosulfonate polymer chains with the formation of micellar associates. Aqueous solutions of binary mixtures of lignosulfonates (с_LS ≥ 0.2 g dm^–3) and sodium dodecyl sulfate (с_DSNa ≥ 0.08 g dm^–3) can be recommended for use as surfactant formulations for high-temperature autoclave leaching of polymetal ores.

An intumescent fireproofing formulation on silicone base, modified with mineral components (calcium carbonate, wollastonite, aluminosilicate microspheres), was studied by synchronous thermal analysis (Netzsch SТА 449 F5 Jupiter®). Introduction of 2–20 wt % wollastonite or aluminosilicate microspheres enhances the heat resistance (the ash residue increases by 27–40%) and reduces the combustibility of the modified fireproofing formulations (the total thermal effect of thermolysis of the fireproofing formulation decreases by a factor of more than 3). The optimum content of wollastonite and aluminosilicate microspheres is 5 wt %. Addition of calcium carbonate gave no complex positive effect.

The influence of the forming conditions on the structure and properties of Aquivion® perfluorinated proton-conducting membranes prepared by casting from a dimethylformamide solution was studied. At properly chosen and controlled conditions of solvent evaporation and subsequent heat treatment, membranes with more ordered morphology and structure, high level of mechanical properties, and high proton conductivity can be obtained. These results are attributed to the structural self-organization of the polymer base of the membranes in the course of nanofilm formation. The properties of Aquivion® type membranes prepared by casting and pressing were compared. The possibility of improving the strength properties of the membranes to the level close to that of the membranes prepared by extrusion was demonstrated.

D,L-Lactide–ε-caprolactone copolymers were synthesized by polymerization in the bulk. Films of these copolymers were prepared, and their strain properties and degradation rate under physiological conditions were studied. Introduction of ε-caprolactone into the copolymer increases the film elasticity and decreases the degradation rate compared to poly(D,L-lactide) homopolymer, and also favors spreading of human keratinocytes. The films obtained can be used for treatment of wounds and burns.

Specific features of formation of composite materials based on polyethylene, multi-walled carbon nanotubes, and cobalt nanoparticles (MWCNT–PE and Co/MWCNT–PE) by in situ polymerization were revealed. The in situ polymerization technique is based on ethylene polymerization on a highly dispersed Ti-containing catalyst supported on the surface of MWCNT and Со/MWCNT. This method ensures uniform distribution of MWCNT and Co/MWCNT in the polyethylene matrix. The effect of MWCNT and Со/MWCNT on the final properties of the composite materials was determined. Introduction of MWCNT into the polyethylene matrix increases the specific electrical conductivity of the material. Such composite materials can be used for preparing concentrates with preset composition for the subsequent preparation of antistatic coatings. Introduction of the Со/MWCNT filler into the polyethylene matrix makes the material paramagnetic owing to Co nanoparticles and allows its use for preparing coatings that efficiently protect from electromagnetic radiation.

In this study, the Cu-doped Ce‒Mn/ATP denitration catalyst was prepared by impregnation method and heterogeneous precipitation method and its denitrification performance was tested. It was found that the denitrification effect was obviously improved after Cu doping. And the denitration effect of the catalyst prepared by the heterogeneous precipitation method was better and the denitrification rate was above 98%. Under this method, n(Cu: Mn) = 1 had the best denitration effect, with a maximum of 99.76%. The prepared catalysts were characterized by means of XRD, XPS, BET, and SEM. The results showed that CuMn₂O₄ and CuO appeared in the Cu doped catalysts. Moreover, the doping of Cu enriched the pore structure and surface morphology of the catalyst, so that the catalyst showed good denitrification performance.

To increase the photogenerated carrier separation and reduce the electron-hole recombination process for photocatalysts performance. In this article, hierarchically macroporous structured TiO₂/SnO₂ materials with controllable composition and phases have been successfully synthesized by using a typical process. This method involves several sequential preparation steps: (1) preparation of core-shell structure SnO₂/PS submicrospheres by hydrothermal method; (2) preparation of TiO₂/SnO₂/PS submicrospheres by assembling amorphous TiO₂ on surface of SnO₂/PS submicrospheres; (3) direct calcination of TiO₂/SnO₂/PS submicrospheres to eventually produce hierarchically structured TiO₂/SnO₂ materials with pores-in-pores. With rutile phases TiO₂, TiO₂/SnO₂ macroporous materials show significantly enhanced catalytic activity when used as photocatalysts for the degradation of Rhodamine B under UV irradiation. The photodegradation ratio of Rhodamine B was 96% for 25 min.

xWO₃–(100–x)P₂O₅ (70 mol % ≤ x ≤ 82 mol %) glasses were obtained by melt quenching. Their thermal properties were studied by the DTA method. It was found that the rise of WO₃ сontent leads to a decrease in thermal stability of glasses and lower glass transition and crystallization temperatures. The compositions 70WO₃–30P₂O₅ and 75WO₃–25P₂O₅ are not crystallized in the temperature range 35–950°C.

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