卷 90, 编号 7 (2017)

Twin-screw extruder was used to produce fibers based on polyactide and its stereocomplexes. The fibers were subjected to an additional 4- and 6-fold orientation stretching. The supramolecular structure of the oriented and unoriented fibers was studied. It was found that the degree of orientation stretching of the polyactide fibers affects their stress-strain and elastic characteristics and also their biodegradation kinetics.

Conditions were determined in which basic bismuth oxalate of composition BiC₂O₄(OH) can be obtained by direct precipitation upon addition of oxalic acid from nitrate solutions used in production of bismuth compounds. The composition of the compound was confirmed by X-ray phase and chemical analyses, IR and Raman spectroscopy, and thermogravimetry. Electron microscopy was used to examine the effect of the composition of the reaction medium and temperature on the morphology of the product being obtained. It was shown that β-Bi₂O₃ can be obtained in oxidative thermolysis of basic bismuth oxalate, depending on its morphology.

New procedure for synthesis of new complex compounds on the basis of boric, aminoacetic, and citric acids was developed. Specific features of the crystal formation for boron-based complex compounds were studied. The supposed application area of these compounds is associated with their biocide activity toward pathogenic microorganisms, such as Eschericia coli (intestinal bacterium), Staphylococcus aureus (aurococcus), and Candida albicans (yeast-like fungi of Candida genus).

X-ray phase, X-ray diffraction, and synchronous thermal analyses, Mossbauer and IR spectroscopy, and scanning electron microscopy were used to study processes occurring in the stages of mechanochemical oxidation and thermal treatment of coarsely dispersed iron and cast iron powders in a dispersion medium of water and oxalic acid solutions. The optimal mechanochemical-synthesis conditions were determined and it was found that the preparation method affects the phase composition, structure, and properties of the resulting oxides. It was experimentally confirmed that the mechanochemical oxidation method makes it possible to obtain oxides by the zero-sewage technology with a specific surface area 1.5–12 times larger that that in oxides produced by the conventional precipitation technique. An analysis of the reactivity of the samples in the model reaction of carbon monoxide conversion by steam demonstrated their high catalytic activity.

TiO₂, Cr₂O₃, ZrO₂, and SnO₂ films with thicknesses of ∼10–100 nm were produced via dipping into solution and subsequent annealing in air. The films were studied by the methods of scanning electron microscopy, elemental X-ray spectral analysis, optical spectroscopy, and X-ray diffraction. The electrical conductivity of the films in air and in a vacuum was measured. The adhesion of most of the films to the substrate was found to be high. A crystalline structure was observed for films thicker than 10 nm. The films have a specific surface resistance of 10⁸–10¹² Ω in air and 10⁹–10¹⁴ Ω in a vacuum. The films are promising as coatings for various purposes, including the development of structures of the core–shell type.

СBV-720 zeolite was compared to H-Beta zeolite and KU-2 cation-exchange resin in the catalytic performance in addition of alcohols to norbornene, in condensation of aldehyde and ketone with di- and triols, and in the Prins reaction of olefins with formaldehyde. These reactions, when performed on СBV-720 zeolite, occur 1.5–2 times faster than on the other catalysts. The corresponding ethers and cyclic acetals were synthesized.

Preparation of superhydrophobic conducting coatings based on silicone matrix and two types of carbon nanotubes, native and modified with alkyl groups, is described. The amount of carbon nanotubes per unit surface area was kept constant in all the samples, whereas the content of the polymer matrix was varied. The electrical conductivity, contact angle, and sliding angle were measured. The structure of the coatings was studied with an optical profilometer and a scanning electron microscope. The largest contact angle was 158.4° for the sample with 50 wt % content of native carbon nanotubes. For the samples with more than 20 wt % content of carbon nanotubes of both types, the sliding angle was less than 1°. Changes in the micro- and nanostructure of the coatings, observed with variation of the content of the polymer matrix in the samples, were studied. The relationship between the structural changes, on the one hand, and hydrophobic and water sliding properties of the conducting coatings, on the other hand, was demonstrated.

Trimetallic NiMoW/Al₂O₃ catalyst was prepared using mixed H₄SiMo₃W₉O₄₀ heteropoly acid of Keggin structure and nickel citrate. Bimetallic NiMo/Al₂O₃ and NiW/Al₂O₃ catalysts based on H₄SiMo₁₂O₄₀ and H₄SiW₁₂O₄₀, respectively, were synthesized as reference samples. The use of mixed H₄SiMo₃W₉O₄₀ heteropoly acid as an oxide precursor allows the tungsten sulfidation degree and the degree of promotion of active phase particles to be increased. The hydrodesulfurization activity is enhanced as compared to NiW/Al₂O₃ catalyst. The synergistic enhancement of the activity of the NiMo₃W₉/Al₂O₃ catalyst relative to the bimetallic analogs is probably caused by formation of new mixed promoted active sites for direct desulfurization.

Supported oxide catalysts of the overall composition V_0.3Mo₁Te_0.23Nb_0.12/nAl–Si–O (n = 0, 10, 25, 35, 50, and 70 wt %) were tested in oxidative dehydrogenation of ethane and were characterized by chemical analysis, X-ray diffraction analysis, and transmission electron microscopy. The use of the Al–Si–O support in a wide range of its content (from 10 to 50 wt %) favors formation of nanodomains of the active М1 phase ensuring higher, compared to the bulk catalysts, activity in oxidative dehydrogenation of ethane. The formation of secondary phases of aluminum molybdate and vanadium–molybdenum double oxide, observed at the support content increased over 35 wt %, leads to worsening of the catalytic properties.

Mesoporous carbon prepared by template synthesis using SBA-15 mesostructured silicate material was tested as an electrocatalyst for electrochemical synthesis of Н₂О₂ from О₂ in a two-layer gas-diffusion electrode. Preparative syntheses of Н₂О₂ in 0.06 to 2.0 M aqueous solutions of various electrolytes (pH 2–8) were performed at current densities in the interval 0.05–0.19 A cm^–2. Solutions with an Н₂О₂ concentration of 1–2.8 M were prepared with 46–70% current efficiency. Thus, the material tested shows promise as an electrocatalyst of two-electron reduction of oxygen to Н₂О₂.

Synthesis in a gel as a method for the preparation of poly(chlorosulfostyrene) by treating polystyrene with chlorosulfonic acid was proposed, which makes it possible to obtain a polymer with a total degree of functionalization of sulfo and chlorosulfo groups up to 1.0. The possibility of regulating the degree of chlorosulfonation in the range from 50 to 100% was shown. The composition and structure of the products of polymer-analogous transformations were characterized by elemental analysis, FTIR spectroscopy, and thermogravimetry with IR identification of the decomposition products. Chlorosulfonation in the gel makes it possible to achieve a high degree of functionalization even at lower temperatures, at room temperature, and at less time than compared with known methods.

The structure of acrolein-modified chitosan films was studied by IR spectroscopy. Modification makes the films more hydrophobic. The physical and mechanical properties of films modified with acrolein solutions of low concentrations are improved relative to the unmodified films. The glass transition and decomposition temperatures of the samples were determined by dynamic mechanical and thermal gravimetric analysis. The possibility of using the materials for the development of matrices for tissue engineering was demonstrated.

Based on the advantages of graphene and zeolite, respectively, the graphene/zeolite composites with core-shell structure were synthesized. The features of the composites were characterized and experimental conditions were used to evaluate the potential of graphene/zeolite composites in removing copper ions Cu²⁺ and methyl orange (MO) in single and binary systems. In a single system, the adsorption of Cu²⁺ and MO are in accordance with the Freundich and Langmuir model, respectively, with maximum adsorption capacities at 39.06 and 2.71 mg g^–1. For the binary system, the coexistence of Cu²⁺ and MO increases the maximum adsorption capacity of the composite material compared with the single one and Langmuir model can better describe the co-adsorption behavior of Cu²⁺-MO binary mixture by the composites.

Olivine structure LiMn_xFe_1–xPO₄ (x = 0∼1) cathode materials were successfully synthesized through hydrothermal method. All obtained samples present monodispersed nanorod morphology with different particle sizes. After identifying specific capacity of as-synthesized cathode materials with half-cell, pouch-typed cells were assembled to investigate electrochemical performance of LiMn_xFe_1–xPO₄ (x = 0∼1) at level of full-cell. The results show that the assembled pouch-typed full-cells with as- obtained LiFePO₄ present excellent rate capability, high-low temperature capacity and cycle life. But even present higher operating potential of 4.1 V vs. Li, LiMnPO₄ show unacceptable electrochemical properties at level of full-cell, which presents a big challenge for the practical applications of LiMnPO₄.