Key Engineering Materials Vol. 670

Abstract: Electron beam processing is one of the effective methods for modification of surface material properties. Influence of electron beam irradiation on the structure of polymeric materials such as polyvinyl alcohol and polylactic acid was investigated. Electron beam processing was carried out at 8 kV accelerating voltage and a pressure of 3 x 10^-2 Torr, the emission current was from 25 to 40 A, the pulse duration was from 150 to 300 μs and the pulse number was from 1 to 10. The elemental composition and the structural state of the surface of irradiated polymer materials were studied by infrared spectroscopy (IR-spectroscopy), X-ray photoelectron spectroscopy (XPS), scanning-electron microscopy (SEM) and atomic-force microscopy (AFM) methods. It was established that certain chemical processes take place and some physicochemical properties change under electron treatment.

Abstract: New type of Ag-containing nanostructured catalyst for high-temperature alcohol oxidation was developed on the basis of mesoporous SiO₂ support. Active component (silver clusters/nanoparticles) stabilized by support surface and polyphosphate inside the pores. It was shown that Ag/P₂O₅/SiO₂ catalyst provides high activity in the course of ethylene glycol oxidation to glyoxal at 500-600 °C. Formation of stable structure of catalyst during thermal treatment includes self-organization of mesoporous structure and chemical bonding of phosphate with silica. The catalyst treatment in red-ox conditions leads to reversible oxidation-reduction of silver and its redistribution from bulk to surface of the catalyst. Silver nanoparticles stabilized with silica-phosphate support are active species in the ethylene glycol oxidation into glyoxal.

Abstract: Thermochemically activated aluminum trihydroxide (Al (OH)₃) is an important intermediate for ceramics, construction materials, catalysts, etc. Functional properties of materials based on Al (OH)₃ depend on its phase composition and porosity. A series of thermochemically activated Al (OH)₃ calcined at temperatures from 120 to 800 °C were studied by low-temperature N₂ sorption, XRD and thermal analysis. It was shown that transformation of gibbsite to boehmite occurs below 300 °C and is accompanied by increasing of specific surface area and pore volume. Transformation of boehmite to γ-Al₂O₃ proceeds above 400 °C. The sample calcined at 500 °C was shown to consist of monophase γ-Al₂O₃ with specific surface area of 206 m²/g and pore volume of 0.55 cm³/g.

Abstract: The moulded Al₂O₃ materials prepared by mixing of thermochemically activated aluminum trihydroxide (TCA ATH) with wood flour were proposed to be used as promising porous catalyst support for various processes. A series of Al₂O₃ supports with different wood flour loading (0, 2 and 5 %wt.) were studied by SEM, low-temperature N₂ sorption, XRD, granule strength and water-absorbing capacity. It was shown that supports were characterized by porous structure with mesopore sizes of 2-20 nm and specific surface area of 159-186 m²/g. The increase of the amount of wood flour leads to increase of the share of pore volume with wider than 10 nm and the decrease of the strength of alumina granules. Thus, optimization of preparation conditions allows obtaining alumina materials with desired porous structure.

Abstract: The paper presents results of investigations of α-Ti microhardness modified by aluminum ions having diverse grain sizes, namely: 0.3 μm, 1.5 μm, and 17 μm. These investigations show that the decrease of the grain size and the additional ion implantation result in the significant modification of the structural and phase state of the alloy and its mechanical properties.

Abstract: The effect of the chromium-magnesium precursor preparation techniques on physicochemical properties (BET surface area, total pore volume, mean pore diameter) and catalysts activity in the gas-phase hydrofluorination of perchloroethylene to pentafluoroethane (Freon 125) was studied. Kinetics of the catalytic reactions was studied for the most active catalyst. Based on the experimental data, the pathway of perchloroethylene fluorination with HF was suggested.

Abstract: Nanocrystalline TiO₂ powder was synthesized using microwave-assisted hydrothermal treatment of titanium oxysulfate in the presence of NH₄F. X-ray powder diffraction analysis and Raman spectroscopy were used to determine phase composition and particle size of obtained titanium dioxide. The studies using methods of TEM and EDX spectroscopy have shown that synthesized TiO₂ powder is a promising functional material for fabrication of photoanode of dye-sensitized solar cells (DSSCs).

Abstract: Aluminates of alkaline earth elements have high photoluminescence properties and resistance to UV radiation. Due to this, they are widely used in optical industry. In this work magnesium calcium aluminate was prepared by sol-gel method. The main stages of the formation of the crystalline structure CaMgAl₁₀O₁₇ were determined by thermal analysis, X-ray diffraction and IR spectroscopy. The surface morphology was studied using scanning electron microscopy. The ratio of elements in the product was installed by X-ray microanalysis.

Abstract: Unstable intermediate oxidation products in the solution of Luteolin [L] and Genistein [G] were discovered by HPLC-MS-ESI(-) in aerobic conditions at pH=8. These covalently bonded compounds of [2L-H₂] and [L+G-H₂] compositions, as well as trimeric [L+2G-2H₂], can be separated by the HPLC, but easily undergo further destruction. Possibly, such compounds are products of initial radical oxygenation. In trimeric conjugate Luteolin, as a more potent reducing agent, binds two Genistein molecules together.

Abstract: Microwave-assisted high temperature hydrolysis of titanium oxysulfate, in the presence of ammonium fluoride, allows synthesizing nanocrystalline titanium dioxide photocatalysts possessing photocatalytic activity as high as the commercial photocatalyst Evonik Aeroxide® TiO2 P 25. Dye-sensitized reactions play an important role in organic dye discoloration in the presence of fluorinated titania.