Персона: Грехов, Алексей Михайлович
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Алексей Михайлович
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- ПубликацияТолько метаданныеPercolation Effects in Mixed Matrix Membranes with Embedded Carbon Nanotubes(2022) Eremin, Y.; Grekhov, A.; Belogorlov, A.; Еремин, Юрий Сергеевич; Грехов, Алексей Михайлович; Белогорлов, Антон АнатольевичPolymeric membranes with embedded nanoparticles, e.g., nanotubes, show a significant increase in permeability of the target component while maintaining selectivity. However, the question of the reasons for this behavior of the composite membrane has not been unequivocally answered to date. In the present work, based on experimental data on the permeability of polymer membranes based on Poly(vinyl trimethylsilane) (PVTMS) with embedded CNTs, an approach to explain the abnormal behavior of such composite membranes is proposed. The presented model considered the mass transfer of gases and liquids through polymeric membranes with embedded CNTs as a parallel transport of gases through the polymeric matrix and a “percolation” cluster—bound regions around the embedded CNTs. The proposed algorithm for modeling parameters of a percolation cluster of embedded tubular particles takes into account an agglomeration and makes it possible to describe the threshold increase and subsequent decrease permeability with increasing concentration of embedded particles. The numerical simulation of such structures showed: an increase in the particle length leads to a decrease in the percolation concentration in a matrix of finite size, the power of the percolation cluster decreases significantly, but the combination of these effects leads to a decrease in the influence of the introduced particles on the properties of the matrix in the vicinity of the percolation threshold; an increase in the concentration of embedded particles leads to an increase in the probability of the formation of agglomerates and the characteristic size of the elements that make up the percolation cluster, the influence of individual particles decreases and the characteristics of the percolation transition determine the ratio of the sizes of agglomerates and matrix; and an increase in the lateral linear dimensions of the matrix leads to a nonlinear decrease in the proportion of the matrix, which is affected by the introduced particles, and the transport characteristics of such MMMs deteriorate. © 2022 by the authors.
- ПубликацияТолько метаданныеEffect of Graphene Oxide on the Permeability of Asymmetric Polysulfone Membranes(2024) Gizzatov, A. S.; Petrov, M. A.; Eremin, Yu. S.; Grekhov, A. M.; Петров, Максим Александрович; Еремин, Юрий Сергеевич; Грехов, Алексей Михайлович
- ПубликацияТолько метаданныеEffect of High Pressures on the Transport of Liquids through a Commercial Reverse Osmosis Polyamide Membrane on a Porous Substrate(2021) Eremin, Y. S.; Panchikhin, M. O.; Grekhov, A. M.; Еремин, Юрий Сергеевич; Грехов, Алексей МихайловичThe paper presents the results of an experimental study on the effect of high pressures on the transport of liquids through a composite reverse osmosis membrane of an AG-90 industrial membrane module (GE Water & Process Technologies), which membrane consists of a microporous substrate (polysulfone) coated with a selective polyamide layer. It has been found that when a "philic" liquid (water) is forced through the membrane, permeability changes nonlinearly with increasing pressure and passes through an extremum at 7.5 MPa. For the membrane from the AG-90 module, hysteresis during the pressure increasing-decreasing cycle has been observed, which can be associated with irreversible deformation of the membrane structure by interaction with water at high pressures. For "phobic" liquids (glycerol, propanol-1, and propanol-2), the membrane permeability decreases nonlinearly with increasing pressure and this change can be explained in terms of known transport models.
- ПубликацияТолько метаданныеBehavior of Polytrimethylsilylpropyne-Based Composite Membranes in the Course of Continuous and Intermittent Gas Permeability Measurements(2021) Bakhtin, D. S.; Malakhov, A. O.; Polevaya, V. G.; Kulikov, L. A.; Grekhov, A. M.; Грехов, Алексей Михайлович© 2021, Pleiades Publishing, Ltd.Abstract: Two methods for monitoring the physical aging of polymer membranes by gas permeability measurements are compared. The traditional method with intermittent permeability monitoring is compared to the continuous permeability monitoring when the membrane occurs under excess pressure of the permeating gas throughout the experiment. A composite membrane with a thin (1 μm) selective polytrimethylsilylpropyne layer containing 10 wt % organic nanoparticles (porous aromatic frameworks) was taken as an example. The continuous permeability monitoring allows acceleration of the physical aging of the membrane and considerable (by two orders of magnitude) reduction of the experiment time. Fast physical aging in a carbon dioxide stream can be an efficient way to reach equilibrium gas permeability of membranes based on glassy polymers with high void volume.
- ПубликацияТолько метаданныеEffect of Taunit Carbon Nanotubes on the Optical Density of Polymer Films Made from Polysulfone, Polymethyl Methacrylate, and Polyvinyl Alcohol(2024) Khazeeva, E. R.; Eremin, Yu. S.; Grekhov, A. M.; Еремин, Юрий Сергеевич; Грехов, Алексей Михайлович
- ПубликацияОткрытый доступDimensional Transformation of Percolation Structure in Mixed-Matrix Membranes (MMMs)(2023) Grekhov, A.; Eremin, Y.; Грехов, Алексей Михайлович; Еремин, Юрий СергеевичA large number of studies of mixed-matrix membranes (MMMs) have confirmed the possibility of obtaining new materials with unique transport properties, including for solving specific problems in the separation of mixtures of liquids and gases. The choice of particles with a given affinity for the matrix and separable components allows researchers to adjust the selective properties of MMMs in a wide range, which changes the properties of MMMs in a wide range. However, even within the framework of the most complex percolation mechanism of the formation of the MMM structure, it is possible to explain only some of the observed effects. In particular, questions about the required particle concentration and fluctuation of properties in various MMM samples are still the subject of research. The results of the numerical modeling of such structures presented in this paper determined the possible causes of the observed deviations of the experimental results, for example, particle size dispersion, agglomeration, and interaction with the matrix. According to our research, the key factor that qualitatively changes the parameters of percolation structures is the ratio of the geometric dimensions of the system. We have confirmed in a wide range a significant change in the conditions of cluster formation and its power at different particle diameters and lengths (traditional parameters in percolation studies). But in our work, we additionally studied the effect on the cluster parameters of the interfacial layer and the anisotropy of the matrix (the transition from the cube to the film). The results obtained show that changing the parameters of the matrix–particle interaction affects agglomeration, and the degradation of the percolation structure is possible. That is, with an increase in concentration, the parameters of the percolation cluster, its power, and the probability of formation, may decrease. But even more negative changes in percolation structures are observed during the transition from a volumetric matrix to films. The anisotropy of space leads to the formation of percolation through the film in certain areas at low concentrations of particles. At the same time, in a significant part of the matrix, percolation between the film surfaces will be absent, and the effect of changing the properties of MMMs in the matrix as a whole decreases. Our study explains the observed instability of MMM properties at fixed concentrations and parameters of embedded particles, including the effect of reducing the influence of particles with increasing concentration.
- ПубликацияОткрытый доступEffect of polymer matrix on characteristics of percolation cluster composed of MWCNT(2020) Eremin, Yu. S.; Grekhov, A. M.; Еремин, Юрий Сергеевич; Грехов, Алексей Михайлович© 2020 Published under licence by IOP Publishing Ltd.Mixed matrix membranes (MMMs) with unique transport characteristics can be prepared by the addition of the minor amounts of carbon nanotubes. The paper presents the results of study gas permeability (O2, N2, CH4) for poly(vinyltrimethylsilane (PVTMS) and Poly(methyl methacrylate) (PMMA) with embedded multiwall carbon nanotubes (MWCNT). The paper shows how the choice of a polymer matrix affects the parameters of a percolation cluster from CNTs.