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28 results on '"Kostyukov, Anton I."'

22. Synthesis, Spectroscopic and Catalytic Properties of FeOx/Al2O3 Nanopowders Prepared by CO2 Laser Vaporization.

Author

Baronskiy, Mark G., Kostyukov, Anton I., Zhuzhgov, Aleksey V., Zaitseva, Nadezhda A., Cherepanova, Svetlana V., Larina, Tatyana V., and Snytnikov, Valeriy N.

Subjects
*LASERS, *CATALYST testing, *SOL-gel processes, *IRON, *OPTICAL properties, *MOSSBAUER spectroscopy, *CATALYTIC dehydrogenation, *VAPORIZATION
Abstract

Nanostructured powders xFe/nano-Al2O3 with the Fe loading of x = 0.0 – 5.0 wt% were obtained using laser vaporization by CO2 laser. XRF, XRD, HRTEM, PL and UV–Vis DRS techniques were employed to investigate physicochemical, structural and optical properties of the synthesized nanopowders with the average particle size of 9 nm. Nanopowders xFe/nano-Al2O3 as model catalysts were tested in isobutane dehydrogenation reaction. The results obtained were compared with similar data for the xFe/γPb-Al2O3 systems synthesized by the conventional sol–gel method. According to XRD and UV–Vis DRS data, in the series of xFe/nano-Al2O3 samples a great part of Fe3+ ions is in the disordered environment of subsurface layers of Al2O3 nanocrystallites, predominantly in the tetrahedral coordination. In distinction to samples of the xFe/γPb-Al2O3 series, in the case of nanostructured xFe/nano-Al2O3 powders the formation of Fe2O3 phase does not occur at any concentrations of iron or conditions of testing. The analysis of the PL spectra of xFe/nano-Al2O3 powders also showed the presence of surface sites of Fe3+ ions, which were not detected for xFe/γPb-Al2O3. Catalytic testing of the xFe/nano-Al2O3 series samples in isobutane dehydrogenation revealed the formation of the iron active sites that ensure catalytic activity of the samples. Differences in the catalytic properties of FeOx/Al2O3 samples obtained by the sol–gel method and laser vaporization are related to different states of Fe3+ ions. Thus, the xFe/nano-Al2O3 nanopowders, in contrast to xFe/γPb-Al2O3, contain a large amount of active Fe3+ sites. These sites, being involved in the dehydrogenation reaction, are present predominantly on the surface of the nanopowders. [ABSTRACT FROM AUTHOR]

Published
2022
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23. Catalytic activity of laser-synthesized CrOx/Al2O3 nanocatalysts with different particle sizes in isobutane dehydrogenation.

Author

Kostyukov, Anton I., Zaitseva, Nadezhda A., Baronskiy, Mark G., Nashivochnikov, Aleksandr A., and Snytnikov, Valeriy N.

Subjects
*CATALYTIC activity, *ISOBUTANE, *DEHYDROGENATION, *SURFACE area, *VAPORIZATION
Abstract

CrOx/Al2O3 model catalysts in the form of nanopowders with the chromium content of 0.96 wt% and the mean particle size 5.5, 7.3, 11.7, 13.1, and 20.5 nm were synthesized by a laser vaporization technique. CrOx/Al2O3 nanocatalysts are mainly represented by softly agglomerated particles with a sphere-like morphology. It was shown that a considerable increase in the mean particle size from 5.5 to 20.5 nm with the corresponding decrease in specific surface area from 297 to 80 m2/g of the freshly prepared catalysts decreased isobutane conversion and selectivity to isobutylene at 550 °C by 2–4% and 10–15 mol.%, respectively. The laser synthesis was found to produce Al2O3 nanoparticles with stable highly dispersed Cr2O3 clusters on their surface, which serves as the active catalytic centers. The presence of such highly dispersed clusters with a size of 2–4 nm was confirmed by the HRTEM method. The catalytic properties of the tested nanocatalysts with the established steady state were stable in isobutane dehydrogenation over 25–30 dehydrogenation-regeneration cycles. On the nanocatalysts that reached a steady state, an increase in the mean particle size led to a decrease in isobutane conversion by 7 and 6%; selectivity to isobutene decreased by 11 and 10 mol.% at the reaction temperatures 560 and 580 °C, respectively. [ABSTRACT FROM AUTHOR]

Published
2022
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28. Laser-induced damage threshold of BaGa_4Se_7 and BaGa_2GeSe_6 nonlinear crystals at 1.053  μm

Author

Kostyukova, Nadezhda Y., Boyko, Andrey A., Erushin, Evgenii Y., Kostyukov, Anton I., Badikov, Valeriy V., Badikov, Dmitrii V., and Kolker, Dmitry B.

Abstract

We investigated the laser-induced damage threshold of two barium chalcogenides crystals, BaGa_4Se_7 and BaGa_2GeSe_6, at 1.053 μm radiation with a pulse duration of 7–10 ns at different pulse repetition rates, namely, 100 Hz, 500 Hz, and 1 kHz. The R-on-1 procedure was applied to determine the 0% probability damage threshold. Both crystals have close values of surface damage threshold at 0.1 kHz, 299  MW/cm^2 (2.28  J/cm^2) for BaGa_2GeSe_6, and 319  MW/cm^2 (2.30  J/cm^2) for BaGa_4Se_7.

Published
2019

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