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30 results on '"Andreev, Andrey S."'

1. Co/multi-walled carbon nanotubes/polyethylene composites for microwave absorption: Tuning the effectiveness of electromagnetic shielding by varying the components ratio

Author

Kazakova, Mariya A., Semikolenova, Nina V., Korovin, Evgeniy Yu., Zhuravlev, Viktor A., Selyutin, Alexander G., Velikanov, Dmitry A., Moseenkov, Sergey I., Andreev, Andrey S., Lapina, Olga B., Suslyaev, Valentin I., Matsko, Mikhail A., Zakharov, Vladimir A., and Lacaillerie, Jean-Baptiste d'Espinose de

Published
2021
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4. Cobalt Carbon Bonding during Carbon Hydrogasification Revealed by 59Co Internal Field NMR

Author

Scholzen, Pascal, Han, Gao-Feng, Lang, Guillaume, Andreev, Andrey S., Baek, Jong-Beom, and d’Espinose de Lacaillerie, Jean-Baptiste

Abstract

Cobalt catalysts are involved in many chemical processes crucial to the energy transition and the shift from oil to biosourced chemicals. Thanks to the ferromagnetic character of cobalt metal, these catalysts can be studied by nuclear magnetic resonance (NMR) in the internal magnetic field of the particle. Using carbon hydrogasification as an example, this work illustrates the potential of 59Co internal field (IF) NMR to study the Co crystallite phase transitions and to distinguish quantitatively, within the limits of the skin effect, different Co–C intermediates present inside a sample containing cobalt and carbon. Here, the main Co–C intermediates evidenced are a Co/C solid solution and a Co3C phase. When using a ball milling process for carbon hydrogasification, a high amount of Co–C intermediates forms, and the reaction rate is increased by several orders of magnitude compared to a classic catalytic reaction (in a fixed-bed reactor). In this work, the time evolution of the 59Co IF NMR are compared to the reaction rate of carbon hydrogasification over the course of the ball milling process. We find a direct relationship between the amount of Co–C intermediates inside the sample and the reaction rate. This confirms that, like for a carbon hydrogasification reaction under classic conditions, the carbon dissociation and formation of Co–C bonds is the rate-determining step.

Published
2024
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8. Magnetic structure and internal field nuclear magnetic resonance of cobalt nanowires

Author

European Commission, National Science Foundation (US), Scholzen, Pascal [0000-0002-8760-3060], Lang, Guillaume [0000-0003-4749-1508], Andreev, Andrey S. [0000-0003-0664-8820], Quintana, Alberto [0000-0002-9813-735X], Malloy, James [0000-0003-2244-1483], Jensen, Christopher J. [0000-0001-7459-1841], Liu, Kai [0000-0001-9413-6782], d'Espinose de Lacaillerie, Jean-Baptiste [0000-0002-2463-6877], Scholzen, Pascal, Lang, Guillaume, Andreev, Andrey S., Quintana, Alberto, Malloy, James, Jensen, Christopher J., Liu, Kai, d'Espinose de Lacaillerie, Jean-Baptiste, European Commission, National Science Foundation (US), Scholzen, Pascal [0000-0002-8760-3060], Lang, Guillaume [0000-0003-4749-1508], Andreev, Andrey S. [0000-0003-0664-8820], Quintana, Alberto [0000-0002-9813-735X], Malloy, James [0000-0003-2244-1483], Jensen, Christopher J. [0000-0001-7459-1841], Liu, Kai [0000-0001-9413-6782], d'Espinose de Lacaillerie, Jean-Baptiste [0000-0002-2463-6877], Scholzen, Pascal, Lang, Guillaume, Andreev, Andrey S., Quintana, Alberto, Malloy, James, Jensen, Christopher J., Liu, Kai, and d'Espinose de Lacaillerie, Jean-Baptiste

Abstract

The magnetic properties of cobalt metal nanowires grown by electrodeposition in porous membranes depend largely on the synthesis conditions. Here, we focus on the role of electrolyte additives on the magnetic anisotropy of the electrodeposited nanowires. Through magnetometry and internal field nuclear magnetic resonance (IF NMR) studies, we compared both the magnetic and crystalline structures of 50 and 200 nm diameter Co nanowires synthesized in the presence or absence of organic additives. The spectral characteristics of IF NMR were compared structurally to X-ray diffraction patterns, and the anisotropy of the NMR enhancement factor in ferromagnetic multidomain structures to magnetometry results. While the magnetic behavior of the 50 nm nanowires was dominated, as expected, by shape anisotropy with magnetic domains oriented on axis, the analysis of the 200 nm proved to be more complex. 59Co IF NMR revealed that the determining difference between the samples electrodeposited in the presence or in absence of organic additives was not the dominant crystalline system (fcc or hcp) but the coherent domain sizes and boundaries. In the presence of organic additives, the cobalt crystal domains are smaller and with defective grain boundaries, as revealed by resonances below 210 MHz. This prevented the development in the Co hcp part of the sample of the strong magnetocrystalline anisotropy that was observed in the absence of organic additives. In the presence of organic additives, even in nanowires as wide as 200 nm, the magnetic behavior remained determined by the shape anisotropy with a positive effective magnetic anisotropy and strong anisotropy of the NMR enhancement factor.

Published
2022

9. Extreme Enhancement of Carbon Hydrogasification via Mechanochemistry

Author

Han, Gao‐Feng, primary, Zhang, Peng, additional, Scholzen, Pascal, additional, Noh, Hyuk‐Jun, additional, Yang, Mihyun, additional, Kweon, Do Hyung, additional, Jeon, Jong‐Pil, additional, Kim, Young Hyun, additional, Kim, Seong‐Wook, additional, Han, Sun‐Phil, additional, Andreev, Andrey S., additional, Lang, Guillaume, additional, Ihm, Kyuwook, additional, Li, Feng, additional, d'Espinose de Lacaillerie, Jean‐Baptiste, additional, and Baek, Jong‐Beom, additional

Published
2022
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11. Superparamagnetic behaviour of metallic Co nanoparticles according to variable temperature magnetic resonance

Author

Yakovlev, Ilya V., primary, Yakushkin, Stanislav S., additional, Kazakova, Mariya A., additional, Trukhan, Sergey N., additional, Volkova, Zoya N., additional, Gerashchenko, Alexander P., additional, Andreev, Andrey S., additional, Ishchenko, Arcady V., additional, Martyanov, Oleg N., additional, Lapina, Olga B., additional, and d’Espinose de Lacaillerie, Jean-Baptiste, additional

Published
2021
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20. Phase evolution during early stages of mechanical alloying of Cu–13 wt.% Al powder mixtures in a high-energy ball mill

Author

Dudina, Dina V., primary, Lomovsky, Oleg I., additional, Valeev, Konstantin R., additional, Tikhov, Serguey F., additional, Boldyreva, Natalya N., additional, Salanov, Aleksey N., additional, Cherepanova, Svetlana V., additional, Zaikovskii, Vladimir I., additional, Andreev, Andrey S., additional, Lapina, Olga B., additional, and Sadykov, Vladislav A., additional

Published
2015
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22. Surface Hydroxyl OH Defects of η-Al2O3 and χ-Al2O3 by Solid State NMR, XRD, and DFT Calculations.

Author

Volodin, Alexander M., Khabibulin, Dzhalil F., Papulovskiy, Evgeniy, Andreev, Andrey S., Shubin, Aleksandr A., Zenkovets, Galina A., Yatsenko, Dmitriy A., Tsybulya, Sergey V., and Lapina, Olga B.

Subjects
ALUMINUM oxide, HYDROXYL group, DENSITY functional theory
Abstract

For the first time, the detailed structure of χ-Al2O3 and η-Al2O3 surface has been established by implementing the NMR crystallography approach. The surface of η-Al2O3 has been demonstrated to be formed primarily by the (111) facets, while the χ-Al2O3 surface is a combination of (111) and (110) facets. This observation supports the block model of aluminum oxides previously proposed by Tsybulya and Kryukova [S. V. Tsybulya, G. N. Kryukova, Phys. Rev. B 77 (2008) 024112.]. The additional terminal OH groups, observed experimentally and not contributing to (111) and (110) theoretical calculations, are considered to be bonded to the tetrahedral aluminum sites. Their origin is related to the junctions of crystallographic faces of spinel building blocks, being a part of discussed model. Higher content of these terminal OH groups in χ-Al2O3 is a result of more junctions in the case of its more mosaic structure compared to η-Al2O3. [ABSTRACT FROM AUTHOR]

Published
2017
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26. Surface Hydroxyl OH Defects of η-Al2O3and χ-Al2O3by Solid State NMR, XRD, and DFT Calculations

Author

Khabibulin, Dzhalil F., Papulovskiy, Evgeniy, Andreev, Andrey S., Shubin, Aleksandr A., Volodin, Alexander M., Zenkovets, Galina A., Yatsenko, Dmitriy A., Tsybulya, Sergey V., and Lapina, Olga B.

Abstract

For the first time, the detailed structure of χ-Al2O3and η-Al2O3surface has been established by implementing the NMR crystallography approach. The surface of η-Al2O3has been demonstrated to be formed primarily by the (111) facets, while the χ-Al2O3surface is a combination of (111) and (110) facets. This observation supports the block model of aluminum oxides previously proposed by Tsybulya and Kryukova [S. V. Tsybulya, G. N. Kryukova, Phys. Rev. B 77 (2008) 024112.]. The additional terminal OH groups, observed experimentally and not contributing to (111) and (110) theoretical calculations, are considered to be bonded to the tetrahedral aluminum sites. Their origin is related to the junctions of crystallographic faces of spinel building blocks, being a part of discussed model. Higher content of these terminal OH groups in χ-Al2O3is a result of more junctions in the case of its more mosaic structure compared to η-Al2O3.

Published
2017
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27. Mechanochemical Synthesis of SiO44--Substituted Hydroxyapatite, Part II - Reaction Mechanism, Structure, and Substitution Limit.

Author

Bulina, Natalya V., Chaikina, Marina V., Andreev, Andrey S., Lapina, Olga B., Ishchenko, Arcady V., Prosanov, Igor Yu., Gerasimov, Konstantin B., and Solovyov, Leonid A.

Subjects
HYDROXYAPATITE, SILICON research, DOPING agents (Chemistry), CHEMICAL synthesis, CRYSTALS
Abstract

For the first time, silicate-substituted hydroxyapatites have been prepared from mixtures containing different amounts of silicon (0.2-2 mol per mol of apatite unit cell) by dry mechanochemical synthesis at room temperature in a planetary ball mill. The XRD, FTIR, TEM, and NMR spectroscopic data show that the product of the mechanochemical synthesis is a single-phase nanocrystalline apatite containing different amounts of carbonate and silicate ions and adsorbed water. In the annealed samples, three silicon concentration subranges can be distinguished, each of which is characterized by specific evolution of the lattice parameters. The formation mechanism of the silicate-substituted hydroxyapatite obtainable by this method is discussed. The studies indicate that the silicon substitution limit in the silicate-substituted lattice achievable by the dry mechanochemical synthesis followed by heat treatment is 1.2 mol per mol of apatite unit cell. [ABSTRACT FROM AUTHOR]

Published
2014
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28. Design of Al2O3/CoAlO/CoAl Porous Ceramometal for Multiple Applications as Catalytic Supports

Author

Andreev, Andrey S., Tikhov, Serguey F., Salanov, Aleksey N., Cherepanova, Svetlana V., Lapina, Olga B., Bolotov, Vasiliy A., Tanashev, Yuriy Yu., d’Espinose de Lacaillerie, Jean Baptiste, and Sadykov, Vladislav A.

Abstract

Porous ceramometal Al2O3/CoAlO/CoAl was studied by set of physicochemical techniques such as XRD, SEM, internal field 59Co and 27Al MAS NMR, and porosity measurements. They revealed the cermet containing three parts. First, cobalt-free large porous alumina particles which surrounded by the second oxide part representing spinel CoxAl3-xO4 (x=1,2,3) oxides. And third, oxygen-free metallic part consists of cobalt metal particles covered by Co-Al oxide protecting the metallic part from oxidation. Porosity measurements ascertained high porosity (60%) and good SSA (122 m2/g). Also the enhanced adsorption of microwaves due to metallic particles randomly distributed in oxides was found.

Published
2013
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29. Magnetic structure and internal field nuclear magnetic resonance of cobalt nanowires

Author

Pascal Scholzen, Guillaume Lang, Andrey S. Andreev, Alberto Quintana, James Malloy, Christopher J. Jensen, Kai Liu, Jean-Baptiste d’Espinose de Lacaillerie, European Commission, National Science Foundation (US), Scholzen, Pascal, Lang, Guillaume, Andreev, Andrey S., Quintana, Alberto, Malloy, James, Jensen, Christopher J., Liu, Kai, d'Espinose de Lacaillerie, Jean-Baptiste, Scholzen, Pascal [0000-0002-8760-3060], Lang, Guillaume [0000-0003-4749-1508], Andreev, Andrey S. [0000-0003-0664-8820], Quintana, Alberto [0000-0002-9813-735X], Malloy, James [0000-0003-2244-1483], Jensen, Christopher J. [0000-0001-7459-1841], Liu, Kai [0000-0001-9413-6782], and d'Espinose de Lacaillerie, Jean-Baptiste [0000-0002-2463-6877]

Subjects
Electrodeposited cobalt, Giant magnetoresistance, Nanoparticles, General Physics and Astronomy, Physical and Theoretical Chemistry, equipment and supplies
Abstract

The magnetic properties of cobalt metal nanowires grown by electrodeposition in porous membranes depend largely on the synthesis conditions. Here, we focus on the role of electrolyte additives on the magnetic anisotropy of the electrodeposited nanowires. Through magnetometry and internal field nuclear magnetic resonance (IF NMR) studies, we compared both the magnetic and crystalline structures of 50 and 200 nm diameter Co nanowires synthesized in the presence or absence of organic additives. The spectral characteristics of IF NMR were compared structurally to X-ray diffraction patterns, and the anisotropy of the NMR enhancement factor in ferromagnetic multidomain structures to magnetometry results. While the magnetic behavior of the 50 nm nanowires was dominated, as expected, by shape anisotropy with magnetic domains oriented on axis, the analysis of the 200 nm proved to be more complex. 59Co IF NMR revealed that the determining difference between the samples electrodeposited in the presence or in absence of organic additives was not the dominant crystalline system (fcc or hcp) but the coherent domain sizes and boundaries. In the presence of organic additives, the cobalt crystal domains are smaller and with defective grain boundaries, as revealed by resonances below 210 MHz. This prevented the development in the Co hcp part of the sample of the strong magnetocrystalline anisotropy that was observed in the absence of organic additives. In the presence of organic additives, even in nanowires as wide as 200 nm, the magnetic behavior remained determined by the shape anisotropy with a positive effective magnetic anisotropy and strong anisotropy of the NMR enhancement factor., NMR equipment at ESPCI Paris is funded in part by the Paris Region. This project has received funding from the European Union′s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 754387. Work at Georgetown University has been supported by the US NSF (ECCS-1933527). The acquisition of a Magnetic Property Measurements System (MPMS3) at GU, which was used in this investigation, was supported by the US-NSF (DMR-1828420). Bruno Bresson (ESPCI) is thanked for performing the SEM analysis., With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).

Published
2022

30. Extreme Enhancement of Carbon Hydrogasification via Mechanochemistry.

Author

Han GF, Zhang P, Scholzen P, Noh HJ, Yang M, Kweon DH, Jeon JP, Kim YH, Kim SW, Han SP, Andreev AS, Lang G, Ihm K, Li F, d'Espinose de Lacaillerie JB, and Baek JB

Abstract

Carbon hydrogasification is the slowest reaction among all carbon-involved small-molecule transformations. Here, we demonstrate a mechanochemical method that results in both a faster reaction rate and a new synthesis route. The reaction rate was dramatically enhanced by up to 4 orders of magnitude compared to the traditional thermal method. Simultaneously, the reaction exhibited very high selectivity (99.8 % CH 4 , versus 80 % under thermal conditions) with a cobalt catalyst. Our study demonstrated that this extreme increase in reaction rate originates from the continuous activation of reactive carbon species via mechanochemistry. The high selectivity is intimately related to the activation at low temperature, at which higher hydrocarbons are difficult to form. This work is expected to advance studies of carbon hydrogasification, and other solid-gas reactions., (© 2022 Wiley-VCH GmbH.)

Published
2022
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