Volume 89, Nº 5 (2016)

Possibility of using products formed in centrifugal thermal activation of hydrargillite to obtain alumina catalysts washed to remove admixtures of alkali metals was considered. A comparison of the physicochemical and catalytic properties of the samples demonstrated that washing with water is more favorable than that with nitric acid; the catalytic activity and acid-base properties of the catalyst surface are determined not only by the content of Na, but also by the whole set of catalyst preparation conditions. The most active of the samples obtained in the study has acidity close to that of industrial aluminum oxide produced by the reprecipitation method, but surpasses it in activity: at 370°C, the total yield of ethylene and diethyl ether reaches a value of 88.8 mol %, which is 4% higher than that for the reference sample.

Synthesis of Co₃O₄ powders by the microwave method from citrate precursors is described. The structural, surface, and thermogravimetric characteristics of the resulting powders were studied depending on the cobalt ions and citric acid ratio. The specific capacity of the samples was determined to be from 665 to 831 mA h g^–1 after 100 cycles at a current density of 0.5C.

It was shown that dimethylformamide can be, in principle, used as a solvent of ammonium thiomolybdate for obtaining molybdenum disulfide particles by the aerosol-assisted chemical vapor deposition method. IR Fourier spectroscopy was used to examine (NH₄)₂MoS₄–C₃H₇NO liquid solutions and the thermal stability of dimethylformamide and ammonium thiomolybdate vapors. It was demonstrated that pyrolysis at temperatures of 700–900°C yields spherical molybdenum disulfide microparticles with average diameters in the range 0.6–1 µm and “onion” structure.

Procedure for obtaining new hybrid sorbents based on carbon fibers and chitosan-carbon materials modified with molybdenum, which determines the affinity of the sorbents for arsenate ions, is described. The surface morphology was examined and a qualitative chemical analysis of the surface of the composite sorbents was made by the method of scanning electron microscopy–energy-dispersive analysis. Sorption isotherms were obtained for unmodified materials, carbon fibers and chitosan-carbon materials, and hybrid sorbents in twicedistilled and tap water at low As(V) concentrations.

Graphite nanoplatelets treated with nitric acid of different concentrations were studied. The initial graphite nanoplatelets were prepared by ultrasonication of exfoliated graphite. The samples were examined by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and FTIR and Raman spectroscopy and were tested as electrode materials for supercapacitors.

Reactions of secondary amines containing gem-dichlorocyclopropane and cycloacetal fragments with allyl chloride, trans-1,3-dichloropropene, benzyl chloride, and chloromethyl-gem-dichlorocyclopropane were studied. The corresponding tertiary amines were obtained in 20–85% yield. Microwave radiation stimulates N-alkylation of the secondary amine containing the heterocyclic moiety. The structures of the tertiary amines prepared were studied. The configuration of the double bond in the trans-1,3-dichloropropene derivative is retained.

New composites based on activated caramelized aluminoborosilicate glass fabric and radiationsynthesized tetrafluoroethylene telomer solutions were prepared, and their properties were studied. The properties of materials prepared from standard commercial and caramelized glass fabrics were compared.

Biocompatible composite hydrogels based on polyacrylamide and reinforced with bacterial or vegetable cellulose were synthesized. In the mechanical characteristics and water content, these hydrogels are similar to knee joint cartilages with average rigidity level. The structure and chemical composition of the hydrogels after their residence for 45 days in laboratory animal joints were studied by scanning electron microscopy and energydispersive X-ray microanalysis. Prolonged contact of the hydrogels with bones results in formation of calcium phosphate spherulites similar in composition to hydroxyapatite.

A way to improve the kraft pulp production process via acid–base treatment of black liquor was suggested. Data on the process for kraft lignin production by the sulfuric acid procedure were substantiated.

The relationship between the critical detonation diameters of energetic substances and their specific surface area was revealed from the results of studying the detonation ability of a series of energetic substances [pentaerythritol tetranitrate (TEN), cyclotrimethylenetrinitramine (RDX), cyclotetramethylenetetranitramine (HMX), 2,4,6-trinitrophenylmethylnitramine (tetryl), benzotrifuroxan (BTF), hexanitrohexaazaisowurtzitane (CL-20), dinitrodifurazanylfuroxan (DNTF), dinitrodifurazanylfurazan (NTF), 1,1-diamino-2,2-dinitroethene (FOX-7)]. A mathematical expression for this relationship was suggested. The critical detonation diameters of highly dispersed (micrometer particles) energetic substances were determined by experiments and calculations. These diameters are in the range 0.06–0.8 mm, which makes these substances suitable for use in aerospace engineering, priming systems, detonation manifolds, and explosion logic devices.

Thin films of tin(IV) oxide were deposited in a Picosun R-150 installation from tetraethyltin using remote inductively coupled plasma at temperatures lower than 200°C with the aim of developing a material for thin-film current sources. The thickness and morphology of the films were studied by spectral ellipsometry and scanning electron microscopy. Both the thickness and roughness of the films considerably decrease with an increase in the synthesis temperature in the interval 100–180°C. The films are X-ray amorphous. As shown by X-ray photoelectron spectroscopy, tin in the films is in oxidation state +4.

Green synthesis of pure cobalt oxide nanoparticles (CoO-NPs) in aqueous medium has been carried out using gelatin. The main advantage of using gelatin as a stabilizing agent is that it provides long-term stability for nanoparticles by preventing particles agglomeration. The particles have been characterized using X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EADX), and thermogravimetric analysis (TGA). TEM image shows the formation of CoO-NPs with average particle size of 28 nm which agrees well with the XRD data. Cobalt oxide nanoparticles modified carbon paste electrode (CoO-NPs/CPE) displayed excellent electrochemical catalytic activities towards the oxidation of glucose. The electrocatalytic response showed a wide linear range of 7–1000 µM, as well as its experimental limit of detection can be achieved 5.3 µM. The modified electrode for glucose determination is of the property of simple preparation, good stability and high sensitivity.

Highly efficient visible-light-driven Ag₃PO₄/Bi₂MoO₆ hybrid photocatalysts with different mole ratios of Ag₃PO₄ were prepared via sonochemical method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that product are cubic Ag₃PO₄ nanoparticles supported on orthorhombic Bi₂MoO₆ nanoplates. Under visible light irradiation (>420 nm), the Ag₃PO₄/Bi₂MoO₆ photocatalysts displayed the higher photocatalytic activity than pure Bi₂MoO₆ for the decolorization of rhodamine B (RhB). Among the hybrid photocatalysts, 10% Ag₃PO₄/Bi₂MoO₆ exhibited the highest photocatalytic activity for the decolorization of RhB due to the efficient separation of electron–hole pairs.

The combustion method has been utilized to generate cobalt spinel ferrite nanoparticles. The generated nanoparticles were ball milled for different times. Physical and chemical properties of the nanoparticles were characterized by X- ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), and vibrating sample magnetometer (VSM). Crystalline structure of the nanoparticles was stable after ball milling. FTIR showed that oxygen-metal bonding was stronger after ball milling. Moreover, the ball milled nanoparticles magnetically were harder than the nanoparticle without ball milling.