The paper presents a systematic review of recent advances in the development of polymer-matrix nanocomposites containing fibrous (sepiolite-palygorskite group) and non-swelling (kaolinite-serpentine group) clay minerals, as well as their modified forms obtained using surface reactions with organic and inorganic substances. An analysis of scientific trends and the current status of research in this area has been carried out, with particular emphasis on the influence of the types and forms of the considered mineral fillers on the properties of nanocomposites for various applications.
Keywords: polymer nanocomposites, clay minerals, kaolinite, halloysite, sepiolite, palygorskite
Modern development of x-ray technology allows to conduct a detailed study of multiphoton processes of absorption and scattering of x-ray photon by deep and subvalent shells of molecular systems in a wide range of energies. The specifics of solving the problem of interaction of an x-ray photon with a multiatomic system requires the use of a single-center approach to the calculation of the electronic States of molecules. The main disadvantage of this approach is a decrease in the accuracy of the calculation of spectroscopic quantities with limited consideration of the terms of the single-center decomposition of the molecular orbital. The paper studies the effect of accounting for higher harmonics of single-center molecular orbital decomposition on the calculation of the energy characteristics of molecular systems. The analysis of the parameters of the single-center decomposition of the functions of the nuclear ligand, depending on its charge. The criteria for inclusion of higher harmonics of single-center decomposition of atomic ligand functions in the molecular orbital are determined. The calculation of energy characteristics is performed on the example of diatomic molecules HF, LiF and BF. The selected series of molecules makes it possible to study the behavior of higher harmonics of the single-center decomposition of the molecular orbital depending on the growth of the atomic ligand charge.
Keywords: molecular orbital, single-center decomposition, higher harmonics, a nuclear ligand, the energy of the electronic state of a diatomic molecule
The paper presents an overview of the existing calculation schemes and the technique for obtaining the angular parts of the matrix elements of the spectroscopic quantities operators with the discussion of cases of complex electron configurations containing nonequivalent electrons. Using the example of a configuration with four unfilled electronic shells, the high efficiency of the technique for constructing wave functions of arbitrary electronic configurations is shown, based on a combination of Slater's determinant approach and the procedure for sequential coupling of orbital and spin moments on the basis of the Clebsch-Gordan coefficients in the LS coupling approximation.
Keywords: Slater determinant, Clebsch-Gordan coefficient, orbital angular momentum, spin moment, 3j-symbol, coefficients of fractional parentage, LS-coupling
The review of existing nanomaterials for stabilization of clay soils is carried out. The possibilities and limitations of the known nanotechnological approaches to the stabilization of clay soils are analyzed. The influence of nanomaterials on the physical and mechanical properties of clay soils is described.
Keywords: soil, clay mineral, bearing capacity, soil stabilization, nanomaterial
This work presents the results of investigation of one of the most widespread specimens of layered silicates minerals group - montmorillonite, that are the part of the natural dispersion of bentonite from Millerovo minefield via density functional theory (DFT) methods. The hygroscopic moistness of monoions forms of smectite group layered silicates is studied experimentally; these layered silicates are the most active components that significantly determine the properties of the dispersion as a whole. The correlation between hygroscopicity and theoretical values of inter-packet distances is established in studied samples by calculating total energies with optimization of the crystal structure.
Keywords: layered silicates, exchangeable cations, density functional theory, hygroscopicity, montmorillonite
The paper represents the results of theoretical study of molecules behavior of polar aprotonic solvent dimethyl sulphoxide on basal surfaces and in interpackage space of kaolinite. Spectral and energetic regularities of chemical bond formation are studied. Intercalation of DMSO molecules into interpackage space of kaolinite results in the shift of valence vibrations Si-O into high-frequency zone. It also results in vibration suppression of hydroxyl clusters of gibbsite layer. It proves the appearance of strong hydrogen bond between the molecules of polar aprotonic dissolvent and hydroxyl and siloxane kaolinite surfaces. The paper reveals that adsorption of DMSO molecules decreases the surface energy of kaolinite and enables its organophilicity.
Keywords: "layered aluminosilicates dimethyl sulfoxide, density functional theory, intercalation, hydroxyl surface siloxane surface kaolinite"
The paper describes the method for determining the position of the contact wire of electrified railways using microwaves. The method is based on the triangulation system of two georadars and allows to determine a contact wire zigzag and height from the rail head. The proposed method is all-weather with the possibility of continuous monitoring of the overhead contact wire in plan and profile with the opportunity to automate the processing and signaling abnormalities.
Keywords: railroad contact line, contact wire location, GPR, automatic control systems
This work deals with the study of atomic and electronic structure of kaolinite samples (Glukhovtsy deposit) and montmorillonite (Millerovsky deposit) by density functional theory. The applicability of existing exchange-correlation potential in the local density approximation (LDA) and the generalized gradient approximation (GGA) is analised for an adequate description of the physical properties of layered aluminosilicate. An experimental and theoretical study of the IR spectra of minerals, as well as the identification of the most intense absorption bands, performed in the approximation of DFT using the exchange-correlation potential PW91. The analysis of the band structure of these minerals, which showed that these compounds are direct-gap insulators.
Keywords: DFT, clay, clay minerals, phyllosilicates, atomic and electronic structure, crystalline systems, IR spectrum band strukutra, the electron density
This work deals with the integrated study of the composition and structural characteristics of the rock-forming minerals in Millerovsky bentonite clay. The qualitative and quantitative analysis of the clay samples is made by X-ray diffraction , X-ray photoelectron spectroscopy and thermal analysis . The morphological and microstructural features of minerals are investigated by scanning electron microscopy. The application of the method of direct theoretical calculation of the diffraction patterns is showm to determine the crystal-chemical parameters of the studied minerals. The results are aimed at explaining a number of physical and chemical properties of layered aluminosilicate.
Keywords: clays, clay minerals, layered silicates, x-ray diffraction, crystalline systems
The paper is devoted to developing an approach to solving the problem of structure identification of layered minerals of the kaolinite group by the Rietveld method. The calculations of the intensity of the diffracted X-ray radiation are performed for the koalinit samples obtained from different fields. Qualitative agreement between calculated and experimental results has managed the solution of the identification problem for the kaolinite unit cell Glukhovtsy deposit. The obtained results indicate the possibility of identifying the features of the crystal structure of layered minerals by direct calculation of diffraction patterns.
Keywords: layered minerals, crystal structure, group of koalinit, diffractogram, X-rays, Voigt function, phase composition