Vol 90, No 6 (2017)

Mechanism by which nanocrystalline Bi₄Ti₃O₁₂ is formed in thermal treatment of coprecipitated hydroxides was studied. It was shown that the onset of the active formation is correlated with the melting point of the surface phase based on bismuth oxide. The technological synthesis parameters of Bi₄Ti₃O₁₂, at which crystallite sizes in the range 35–60 nm are provided, were determined.

The results of a study of the gas-sensitive properties of nickel oxide layers with respect to n-hexane, acetone, ethanol, benzene, o-xylene, toluene and ammonia are presented. NiO layers 100 ± 5 nm thick were obtained by chemical vapor deposition in the systems (EtCp)₂Ni–О₂–Ar and (EtCp)₂Ni–О₃–О₂–Ar. The electrical resistance of the layers changes in the presence of hexane, ethanol, benzene, and ammonia vapors. The electrical resistance of the obtained layers changed in the presence of vapors of hexane, ethanol, benzene and ammonia. Response and recovery time of the sensing element of the gas sensors did not exceed 6 s in the temperature range 500–600 K.

Potentialities of the method of electrophoretic deposition of thin-film coatings based on micrometer powders of multidoped barium cerate BaCe_0.8Sm_0.19Cu_0.01O_3–δ (BCSCuO) and BaCe_0.89Gd_0.1Cu_0.01O_3–δ (BCGCuO) were considered. Micrometer powders of BCSCuO and BCGCuO were produced by the methods of solid-phase and citrate-nitrate syntheses, respectively. The dispersity, fraction composition, and electrokinetic potential of nonaqueous suspensions of these powders and the electrokinetic parameters of the electrophoretic deposition process were examined. An ultrasonic treatment and ultracentrifugation produced aggregatively stable suspensions of BCGCuO and BCSCuO micrometer particles in a mixed (70/30 vol %) isopropanol–acetyl acetone medium. These suspensions are characterized by high positive values of the zeta potential (+24 and +28 mV, respectively). Thin film coatings of the electrolyte materials BCSCuO and BCGCuO, which are of interest for the technology of medium-temperature solid-oxide fuel cells, were produced by the electrophoretic deposition onto a dense model cathode.

Technology of high-purity trimethylalkoxysilanes was developed. To rule out the lability of chemical forms of trace impurities, an additional stage of the ion-exchange purification of the starting alcohols is introduced into the classical scheme of synthesis of trimethyl alkoxysilanes and deep rectification purification. To raise the yield of the final product, the stage of azeotropic distillation with azeotrope-forming components is introduced. Construction materials are chosen and a gas-chromatographic analysis of the impurity composition of trimethylalkoxysilanes was made. The development was performed with the use of CALS technologies.

Ru–Ba–Cs/Sibunit ternary catalysts were synthesized. Their activity in ammonia synthesis and the thermal stability of the support in a reducing atmosphere at elevated temperature depend on the molar ratio of the promoters. The results of studies using physical methods suggest that cesium predominantly interacts with the support, acting as an electronic promoter, whereas barium is a structural promoter. The synergistic action of the promoters at increased barium content of the catalyst was revealed. The highest activity in ammonia synthesis, 34.5 mL_NH3 g_cat^–1 h^–1, was reached for the 4% Ru–10.8% Ba–2.6% Cs/Sibunit catalyst.

Granular organo-inorganic amphiphilic sorbents with specific affinity for glucose were synthesized with the aim of developing selective hemosorbents for efferent therapy of hyperglycemia. The sorbents were prepared in oil/water/oil complex emulsions by copolymerization of 2-hydroxyethyl methacrylate and ethylene glycol dimethacrylate on the surface of selenium nanoparticles stabilized with polyvinylpyrrolidone. The phases were stabilized with excess selenium/polyvinylpyrrolidone nanocomplexes. Optimum synthesis conditions ensuring formation of hybrid sorbents with the physicochemical properties required for performing efficient preparative hemosorption and plasma adsorption processes were found. The specific affinity for glucose was reached by modification of these sorbents via imprinting with template glucose molecules in the surface polymer layer and via introduction of boric acid as an affine ligand into the hybrid matrices.

The reaction of congeners of Sovol commercial mixture of polychlorinated biphenyls with 2-aminoethanol in the presence of potassium hydroxide was studied. The results of thermodynamic modeling show that only hydroxy derivatives of polychlorobiphenyls should be formed. The optimum conditions for complete dechlorination of the congeners were determined: 1 atm, 170°С, molar ratio polychlorobiphenyls: 2-aminoethanol: potassium hydroxide = 1: 8: 6. The experimental data obtained using the theoretically chosen initial conditions for the reaction of polychlorobiphenyls with 2-aminoethanol show that the conversion increases from 82 to 96%.

Formation of colloidal particles in tin-containing alcoholic solutions was studied in relation to the SnCl₂ concentration, storage time, and kind of the solvent and stabilizing additive. The highest category of flame resistance and the highest resistance of the fireproofing coating to repeated launderings are reached when the poly(ethylene terephthalate) fabric is activated with alcoholic SnCl₂ solutions with high concentration of 10–15-nm colloidal particles prior to application of an inorganic fireproofing compound.

The formation mechanism, structure, and properties of new network copolymers prepared by thermochemical transformations of Rolivsans with aromatic diamines were studied by IR, ¹Н NMR, and ¹³С NMR spectroscopy and by dynamic mechanical, thermal, and elemental analysis.

Two groups of niobium-containing hexagonal mesoporous silica (Nb-HMS) samples were prepared hydrothermally using niobium oxalate and niobium ethoxide as Nb source, respectively. The samples were characterized by XRD, N₂-adsorption, ICP-AES, UV-Vis, respectively. They were also evaluated by the epoxidation of cyclohexene with cumene hydroperoxide (CHP) as oxidant. It is revealed that the samples possess typical hexagonal mesoporous structure in which most of Nb species exist in the form of framework pentahedral coordinated state. Meanwhile, the Nb-HMS samples from niobium ethoxide give more excellent catalytic performance than those from niobium oxalate. It is likely because that the former samples have a higher total amount of Nb species and a higher proportion of isolated framework Nb species. Accordingly, niobium ethoxide is a better niobium source than niobium oxalate.

Layered transition metal oxide LiNi_xCo_yMnzO₂ cathode materials with different Li amount were successfully synthesized via co-precipitation method. Monodispersed Li[Ni_0.5Co_0.2Mn_0.3]O₂ and Li-rich Li_1.1[Ni_0.5Co_0.2Mn_0.3]O₂ spherical agglomeration consisted of secondary particles, which is favorable for the higher tap-density of materials, can be easily obtained. The pouch-typed cells with obtained materials were assembled to investigate electrochemical performance at level of full-cell. The results show that the assembled pouch-typed full-cells with Li-rich sample present higher capacity, better rate capability and cycle life.

In the present study, adsorption of Cd(II) ion from an aqueous solution on natural clinoptilolite (NC), natural bentonite (NB), modified clinoptilolite (MC) and modified bentonite (MB) were investigated. Response surface methodology (RSM) and central composite design (CCD) were used for NC and NB in order to investigate the effect of pH and contact time on adsorption efficiency and process optimization. Based on statistical analysis, the Cd(II) adsorption model was highly significant, with very low p-values. pH’s 5.35 and 3.89, and contact times 20.49 and 16.27 h, with adsorption efficiency 94.86% and 87.42%, were found to be optimum for Cd(II) ion adsorption on NC and NB, respectively. The experimental data was fitted to adsorption isotherm models, indicating the monolayer sorption of Cd(II). The Jossesns, Unilan, Baudu, and Freundlich models were selected as the best models, with correlation coefficients of 0.8973, 0.9930, 0.9267, and 0.9723, and with lowest error for NC, NB, MC, and MB, respectively, with negligible differences compared to the experimental values. The results showed that the NC adsorption efficiency is higher than NB in both cases.

Recoverable and recyclable heterogeneous Y₂(CO₃)₃ nanoparticles efficiently catalysed the one-pot synthesis of tetrahydropyrans via multicomponent reaction of dimedone, aromatic aldehyde, and malanonitrile using methanol as a solvent. The desired products were obtained with 84–95% yields. The present approach offers several significants such as short reaction time, high yield, easy purification, minimum catalyst loading, and use as an alternative catalyst. Y₂(CO₃)₃ and Zr(CO₃)₂ nanoparticles were prepared by hydrothermal method. The synthesized catalysts was characterized by various analytical investigative techniques like FTIR, XRD, SEM, EDAX, TEM with SAED, and BET surface area.

Oxidation resistance of biodiesel synthesized by ester interchange of vegetable oil and animal fat triglycerides with methanol was studied. When stored under common conditions (in the dark at 20–25°С), the biodiesel is stable for no less than a year. However, the thermal oxidation resistance of biodiesel is low. The results obtained by different methods suggest that the processes occurring in the course of thermal oxidative degradation include not only radical-chain oxidation but also various condensation reactions showing no correlation with the former process. With this fact taken into account, additives enhancing the thermal oxidation resistance of biodiesel to the level of petroleum fuels containing no additives and no biodiesel were found among shielded phenols and aromatic amines. These additives prolong the shelf life of biodiesel fuel, which today is as short as 3 months, and allow the admissible concentration of biodiesel in mixtures with petroleum diesel fuel (7 vol %) to be increased.

In the title the evolution should be replaced by evaluation.