Andrey V. Vorotyntsev

Influence of the preparation technique on the optical properties and content of heterophase inclusions of AS 2 S 3 chalcogenide glasses

Bulk samples of As-S chalcogenide glasses were prepared by an interaction of vapors of volatile precursors in low-temperature non-equilibrium plasma discharge (plasma enhanced chemical vapor deposition (PECVD process)). Elemental arsenic and sulfur (As + S), and arsenic monosulfide and sulfur (As4S4 + S) were used as initial substances. In parallel, the As-S bulk samples were synthesized by “traditional” melting of the initial substances in the evacuated quartz ampoule from the same precursors. The optical properties of the bulk samples were compared. The exhausted gas mixtures were analyzed to clarify the difference in carbon impurities content. 3D laser ultra microscopy was used to determine the content of heterophase inclusions in the samples.

Preparation and Characterization of Facilitated Transport Membranes Composed of Chitosan-Styrene and Chitosan-Acrylonitrile Copolymers Modified by Methylimidazolium Based Ionic Liquids for CO2 Separation from CH4 and N2

CO2 separation was found to be facilitated by transport membranes based on novel chitosan (CS)–poly(styrene) (PS) and chitosan (CS)–poly(acrylonitrile) (PAN) copolymer matrices doped with methylimidazolium based ionic liquids: [bmim][BF4], [bmim][PF6], and [bmim][Tf2N] (IL). CS plays the role of biodegradable film former and selectivity promoter. Copolymers were prepared implementing the latest achievements in radical copolymerization with chosen monomers, which enabled the achievement of outstanding mechanical strength values for the CS-based membranes (75–104 MPa for CS-PAN and 69–75 MPa for CS-PS). Ionic liquid (IL) doping affected the surface and mechanical properties of the membranes as well as the gas separation properties. The highest CO2 permeability 400 Barrers belongs to CS-b-PS/[bmim][BF4]. The highest selectivity α (CO2/N2) = 15.5 was achieved for CS-b-PAN/[bmim][BF4]. The operational temperature of the membranes is under 220 °C.

Comparison of optical properties and impurities content of Ge-Sb-S-I glasses prepared by different methods

Bulk samples of Ge-Sb-S-I chalcoiodide glasses of different compositions were prepared by plasma enhanced chemical vapor deposition (PECVD). GeI4, SbI3 and elemental sulfur were the initial substances. Impurities content, optical, and structural properties of the samples were studied. The data obtained were analyzed and compared with the properties of the bulk samples prepared by interaction of the same initial substances into reactive-distillation column at 650°C. The dependence of optical properties of the glasses on preparation technique was discussed.

Quantum chemical simulation of the dissociative chemisorption of hydrogen on metal surfaces of nanoclusters

The mathematical and quantum chemical simulation of surfaces of Cd, Ba, Ca, Cu, Cs, Ti, Ni, Pd, W, and Pt metals was performed. The structural data were obtained for these surfaces, the behavior of a hydrogen molecule near these surfaces was studied. The calculations were performed in the framework of the density functional theory using the hybrid Becke—Lee—Yang—Parr functional in the LANL2DZ basis set. Mathematical modeling of the studied surfaces in the nanocluster approximation was performed by the Alexandrovich method. The results indicate that metals Ni, Pd, Pt, W, and Ti exhibit high catalytic activity in the dissociative chemisorption of hydrogen, while Ba, Cd, Cs, Ca, and Cu are lowly efficient because of the formation of hydrides.

Kinetics of catalytic hydrogen reduction of SiCl 4 in the presence of nickel chloride

We have studied the reduction of silicon tetrachloride in the presence of a nickel-chloride-based catalyst. The kinetics of the process have been analyzed and the order and activation energy of the reaction have been determined. One of the main reactions on the catalyst surface is the transfer of a chlorine atom from a chlorosilane molecule to a hydrogen molecule, resulting in the formation of hydrogen chloride. The proposed reaction mechanism is supported by X-ray diffraction and chemical analysis data.

An improved back-flush-to-vent gas chromatographic method for determination of trace permanent gases and carbon dioxide in ultra-high purity ammonia

A novel method for rapid, quantitative determination of trace permanent gases and carbon dioxide in ultra-high purity ammonia by dual-channel two-dimensional GC-PDHID is presented. An improved matrix back-flush-to-vent approach combining back-flush column switching technique with auxiliary NaHSO4 ammonia trap is described. The NaHSO4 trap prevents traces of ammonia from entering the analytical column and is shown not to affect the impurity content of the sample. The approach allows shortening the analysis time and increasing the amount of measurements without extensive maintenance of the GC-system. The performance of the configuration has been evaluated utilizing ammonia- and helium-based calibration standards. The method has been applied for the analysis of 99.9999+% ammonia purified by high-pressure distillation at the production site.

Kinetics of germanium tetrachloride reduction with hydrogen in the presence of pyrolytic tungsten

Pyrolytic tungsten coatings have been produced on the surface of ash microspheres under steady-state conditions using tungsten hexacarbonyl as a precursor. The nanostructured composites thus obtained were characterized by X-ray diffraction and scanning electron microscopy. We have studied the kinetics of the catalytic reduction of germanium tetrachloride with hydrogen in the temperature range 423–973 K in the presence of the composites as catalysts and determined the reaction order and activation energy for the catalytic reduction of germanium tetrachloride with hydrogen.

Catalytic effects of electrode material on the silicon tetrachloride hydrogenation in RF-arc-discharge

A silicon tetrachloride reduction in RF-arc-discharge (40.86 MHz) has been experimentally studied. The electrode material significantly affects the composition of the chlorosilanes in the gas phase at the outlet of the reactor which may be attributed to high and at the same time different catalytic activity of Cu, Ni, Nb, and Zr metals belonging to the transition of d-elements and W f-elements of the periodic table. The corrosion has been observed on the electrodes with the formation of chlorides of Cu, Ni, Nb, Zr, and W metals. In the system formed by two electrodes and plasma there are three main reactive regions in which the recovery of silicon tetrachloride by hydrogen at different flows is conducted independently from each other. The analysis of exhaust gases, chemically active plasma and condensed phase by emission-spectroscopy and GCMS spectrometry made it possible to propose the mechanism of formation of observed intermediate species and final products. On the basis of the obtained results we can conclude that this type of RF-plasma discharge includes two mechanisms of plasma chemical reactions: one with the participation of active particles formed in plasma and one initiated by the catalytically-active surface of the electrode.

Plasma treatment as another way to reduce selective absorption of water and oxygen traces in As-Se and As-S-Se bulk glasses for fiber drawing

Bulk samples of As-Se and As-S-Se chalcogenide glasses were prepared by interaction of vapors of volatile precursors in low-temperature non-equilibrium plasma discharge (PECVD process). The PECVD synthesis was carried out in the flowing quartz reactor at the walls temperature about 250 °C. Elemental As, S and Se were used as the initial substances. In order to compare the bulk samples were synthesized as well by “traditional” melting of the initial substances into evacuated quartz ampoule from the same precursors. The optical properties of the bulk samples prepared by different methods and their impurities content were compared.

The modelling of gasoline permeation through polymeric materials

There are several challenges of automobile industry development. One of the most evident ways is the reducing car weight by using polymeric materials for the construction of the main vehicle’s components. The paper considers the model to calculate the permeability of the vapour components by diffusion and solution through the polymer material. The time of the stationary state is determined. The theory was examined by the experimental study on the example of nitrogen permeation through polytetrafluoroethylene. The experimental results are in satisfactory agreement with the calculations. The diffusion coefficients based on the structure of the polymer were examined. In case of non-experimental data evaluation it can be performed by numerical methods.