The article describes the design of an experimental equipment (sample) for determining the cohesive strength of powder coatings in inactive and aggressive environments. A method for determining the mechanical characteristics of samples with coatings is presented, as well as data from the results of testing the cohesive strength of coatings based on nickel, PN60Y40, PN40Y60, iron-aluminum, coatings of self-fluxing alloys based on nickel PGSR-2, PGSR-3, PGSR-4.
Keywords: experimental equipment, cohesive strength, gas-thermal powder coatings, physical and mechanical properties, plasma spraying
The results of the development of asymptotic expressions for the calculation of the background of internal friction at the boundaries of the General type for the limiting cases of frequency dependence are presented. Mathematical expressions are obtained on the basis of consideration of models of the border containing periodically located steps of alternating signs and the intercrystalline border of the general type consisting of parallel plane segments of the set width separated by alternating steps of identical height and cylindrical pores.
Keywords: model, boundary, internal friction background, relaxation, temperature-frequency dependence, slip rate
The results of a theoretical and experimental study of the synthesis of GaInAsBi thin-film structures formed on InAs substrates in the field of a temperature gradient are discussed. The features of interfacial interaction in the In-As-Sb system in the presence of isovalent solvents (In, Bi) have been studied. The values of the interaction parameters and the distribution coefficients of the system components are determined. Optimal technological modes for obtaining InAs-based heterostructures are presented. The properties of the surface of epitaxial layers are studied experimentally. It was found that the main control parameters are the temperature of thermomigration and its gradient. It is shown that the synthesized semiconductor materials can be effectively used in electronic devices of a new generation - electro-optical modulators and supersensitive sensor elements.
Keywords: epitaxial structure, crystallization, recrystallization, melt, segregation coefficient, organometallic compound, voltage sensitivity, near infrared range, solid solution, optical characteristic
The physicochemical properties of cobalt catalysts on a NaX zeolite support have been studied. The parameters of the specific surface area, reduction of deposited cobalt, and structural properties of the active component of catalytic systems have been determined. To establish these properties, the methods of BET, TPR, TPD-H2, IR spectroscopy were used. It is shown that the preparation procedure has a significant effect on the physicochemical characteristics of the samples.
Keywords: catalysts, cobalt, zeolite, dispersion, specific surface area of the active component
Methods of mathematical modeling of complex systems are considered. To construct mathematical models of changes in the electrical capacity of microlayers of magnetic nanofluids, the universal statistical package IBM SPSS Statistics was reasonably adopted. To optimize the construction of models, a database of the electric capacity of a cell with a microlayer of magnetic nanofluid and a program for generating a calculated model of the electric capacity of a capacitor with a magnetic nanofluid for IBM SPSS Statistics and Microsoft Excel were developed.
Keywords: magnetic nanofluid, concentration, microlayer, polarization, electric field, mathematical model, regression model
The article investigates the role of the preparation method and heat treatment in the formation of the physicochemical properties of cobalt catalysts on ZSM-5 support. Determination of the main characteristics of the samples showed that the Co/ZSM-5 I catalyst obtained by the impregnation method has the optimal cobalt dispersion and crystallite size.
Keywords: synthesis of hydrocarbons, cobalt, zeolite, preparation of catalysts, heat treatment
The results of studies of the structural and chemical properties of cobalt catalysts on zeolite HY support are presented. The samples were characterized by BET, TPR, TPD-H2, and IR-spectroscopy. It was found that these properties largely depend on the preparation method.
Keywords: Fischer-Tropsch synthesis, active surface, cobalt, zeolite, preparation method
This article presents and investigation the diffused reflection spectra of light from designed green pigments based on chromium(III) oxide, obtained by pyrochemical method by thermal decomposition of ammonium dichromate powder and hydrolytic method from chromium(III) sulfate in water-ammonia solution, as well as zinc oxide doped with cobalt, which are obtained by pyrochemical Sol-gel citrate method, with different levels of cobalt doping, obtained on the basis of silicone with the addition of obtained green pigments based on chromium(III) oxide), some commercial samples of PLA plastics are green in color and from naturally aging green leaves of grasses, trees and shrubs typical of areas with a transitional climate from mild continental to subtropical according to the Köppen classification. A comparative analysis of their diffuse light reflection spectra was performed to determine whether it is possible to partially simulate the diffused light reflection spectra from naturally aging green tree leaves with non-organic pigments or functional materials. Based on the analysis conducted, it is concluded that the studied commercial samples of green PLA plastics are categorically not suitable for simulating the spectra of diffused light reflection from green leaves. However, it is possible to create functional composite materials that can approximately imitate the spectra of diffused light reflection from green leaves of grasses, trees and bushes.
Keywords: spectroscopy, diffuse reflection, functional materials, pyrochemical sol-gel citrate method, hydrolytic methods, chromium (III) oxides, inorganic pigments
Piezoceramics based on the lead zirconate-titanate (PZT) system is the basis of most transducers operating on the piezoelectric effect and are used in various electronic devices operating in the sections of electrical and hydroacoustics, ultrasonic technology, etc. In turn, piezoceramic materials created in the last century have substantially exhausted their potential for use in modern devices, and it is rather difficult to develop new compositions and is not economically efficient. In connection with the above, an urgent task is to find modern ways to increase the parameters of piezoceramic materials.
Keywords: piezoceramics, piezophase, piezomaterial, ceramic technology, microstructure
The article presents the results of studying the effect of the loading of active metal on the physicochemical properties of cobalt catalysts for the Fischer-Tropsch synthesis on a silicate support, promoted with aluminum. Using the BET, XRF, TPR, TPD-H2 methods, it has been established that the optimum cobalt content is 15‒18 wt. %.
Keywords: Fischer-Tropsch synthesis, catalyst, cobalt, active component, loading
Concentration changes of refraction and frequency of raman spectrum in melts of salt systems of alkali metals containing nitrate and thiocyanate anions are shown. The change in molar refraction and frequency confirmed the concept of additivity and linearity of isotherms when changing composition.
Keywords: molten salt, nitrates and thiocyanates of alkali metals, refraction, raman-spectr
The article considers the effect of Al2O3 loading on the physical and chemical properties of cobalt catalysts. The loading of the alumina additive has a significant effect on both the phase and texture properties, as well as on the cobalt reduction process in the composition of the studied samples. It was found that with increasing loading of the additive, the specific surface area of the catalysts decreases, and the cobalt recovery process slows down.
Keywords: Fischer-Tropsch synthesis, catalyst, cobalt, alumina, promoter, temperature programmed reduction
The paper discusses the problems of predicting the growth regimes of quasi-one-dimensional electronic structures - quantum nanowires based on three-component compounds A3B5. It is shown that modeling of growth processes of threads based on the Monte Carlo method can be an effective solution. The formation of quantum nanowires is carried out due to the external flow of particles transferred in the first series of experiments perpendicular to the substrate, in the second series - at random angles. The constructed model allows us to evaluate the effect of the composition on the geometric parameters of the formed objects. The critical thickness of quasi-one-dimensional structures is calculated. Conclusions are drawn about the control factors of the processes of thread growth. It is shown that compositional variations are an effective parameter for controlling the processes of formation of three-component 1D structures.
Keywords: quantum nanowires, Monte Carlo method, growth on a substrate, adsorption, diffusion, one-dimensional structures
The paper studies the liquid-phase epitaxy processes of a new material of infrared optoelectronics - indium arsenide doped with bismuth using a stepwise thermal field. An analysis of the phase equilibrium during the growth of a solid solution is carried out. The possibility of the formation of a mesostructure (modulation of the composition along the growth coordinate) is shown. The problems of defect formation in composite layers grown from a melt are considered. Ways of decreasing the dislocations density in gradient layers are discussed. A relatively simple method for controlling the thermal field of temperature in the crystallization zone and a new technological procedure for the sequential crystallization of solid solutions with a mesostructure have been developed.
Keywords: solid solutions, liquid-phase epitaxy, indium arsenide, mesostructure, stepwise thermal field, dislocation generation
The theoretical aspects of crystallization of multicomponent solid solutions are discussed. Antimonoid heterosystems in which bismuth is present are considered, a component that largely determines the photoelectric properties of the studied materials. The features of establishing the equilibrium of the liquid and solid phases in the process of crystallization of these systems are considered. The laws of the thermodynamic behavior of heterosystems in the conditions of gradient liquid-phase epitaxy are established. The results of experimental studies on the growth of solid solutions of multicomponent bismuthides on InSb substrates are presented.
Keywords: solid solutions, migrating liquid phase, indium antimonide arsenide, gallium bismuthide, binary pair, recrystallization, quasicrystalline structure
In this work, we simulated the graphene-MnO composite structure based on minimizing the electron density functional. The analysis of the processes of rearrangement of the interface surface SLG (monolayer of graphene) - MnО (111). In this case, the interface was subjected to hydrogenation. The distribution of the effective charge on graphene is investigated. A decrease in the work function of the charge carriers during hydrogenation of the interface is established.
Keywords: effective charge, graphene, passivated surface, density functional, interface, work function, energy gap, band structure
In this work a breaking of interatomic bonds of kaolinite unit cell under a microwave irradiation was studied. Using density functional theory method (DFT), free energy of the unit cell was computed: without an external field created by the microwave radiation, with the field along (100), and (010) and (001) directions of the unit cell. It was shown that unit cell free energy differences are several kJ/mol. Computational results are backed up by a band structure computation. The conlcution is that there is no bond breaking in the caolinite unit cell caused by the microwave irradiation.
Keywords: kaolinite, microwave field, covalent bonds, discontinuity, ab inito, density functional theory, unit cell, free energy, electronic band structure, clay
hydroxyapatite, non-collagenous protein, implant, quantum-chemical analysis, molecular model, one-electron spectrum, vibrational mode, osseointegration.
Keywords: hydroxyapatite, non-collagenous protein, implant, quantum-chemical analysis, molecular model, one-electron spectrum, vibrational mode, osseointegration
The temperature dependence of the contact angle of wetting allows of Pb-Na of different concentrations on substrates of Co-Cr, Ni-Cr and stainless steel substrate 25X18H9C2 was studied by the method of a lying drop. Measurements were carried out by the method of a lying drop from 359°C to 800°C in an atmosphere of pure helium grade A. It is shown that the value of the wetting angle decreases with increasing temperature, wetting thresholds are observed.
Keywords: wetting angle polytherms, wetting threshold, Co-Cr, Ni-Cr, 25X18H9C2 substrates
Known mechanisms of relaxation of tension in the film at small misfit deformation: the formation of waviness on the initially flat free surface of the film (the instability of the Asaro-tiller-Grinfeld); nucleation of misfit dislocations at the interface film-substrate; a redistribution of atoms near the wavy surface of the film due to the reduction of elastic energy in napylenie on a substrate a semiconductor film; reducing surface energy of the film by increasing its thickness; formation of nanoscale isolated Islands on the surface of the film (Stransky-Krastanov growth); due to the formation of misfit twinning. This paper presents the results of calculations taking into account these factors for different values of the parameters of the film and Islands.The equilibrium conditions of a two-component elastic layer containing mismatch dislocations are investigated. A nanometer-thick SiGe film on a Si substrate and nanometer-sized SiGe Islands on a wetting layer are considered. The uneven distribution of Ge in the sample volume is taken into account. Three-dimensional models of a flat film with dislocation and Islands are constructed. The calculation of elastic deformations is performed using the finite element method. Approximating formulas and iterative algorithm are used to calculate the Ge distribution in the film. According to the results obtained, the uneven distribution of Ge provides relaxation of elastic energy in the alloy, and Ge atoms are concentrated on the protrusions of the disturbed surface of the film and in the vertices of the Islands. Taking into account the heterogeneity of the Ge distribution in the samples has a significant impact on the growth of islets (stable growth occurs with smaller islets) and undulation on the free surface.
Keywords: thin film, heteroepitaxy, Ge, SiGe, misfit dislocations, elastic energy density, finite element method
The article presents the results of research on the morphology of cobalt catalysts for Fischer-Tropsch synthesis on a silicate support with promoting additives of aluminum, manganese and chromium using scanning and transmission electron microscopy. The effect of additives on the surface structure and dimensional characteristics of metallic cobalt was determined.
Keywords: morphology, electron microscopy, catalysts, Fischer-Tropsch synthesis, promoters
The article presents the results of research of the physical and chemical properties of cobalt catalysts on a zeolite support. Methods of BET, thermoprogrammed reduction, thermoprogrammed hydrogen desorption and IR-spectroscopy were used for study. The influence of the support nature on the structural (specific surface area, dispersion of metallic cobalt, size of metal crystallites) and chemical (degree of cobalt reduction) properties of catalysts was established.
Keywords: Fischer-Tropsch synthesis, catalysts, zeolite, hydrocarbon synthesis, structural properties
The work is devoted to the structural characterization of carbon nanotubes by means of electronic combination scattering of light. Samples of double-walled carbon nanotubes with various electronic configurations of the layers have been synthesized, their study has been performed by means of high-resolution transmission electron microscopy, electron diffraction, Rayleigh spectroscopy, as well as spectroscopy of combination scattering of light. The structural characterization of the synthesized nanotubes has been carried out using electronic combination scattering of light, which can play the role of an additional criteria for nanotubes indexing, helping to clarify and verify the obtained results.
Keywords: carbon nanotubes, catalytic chemical vapor deposition, spectroscopy of combination scattering of light
The equations of spinodal decay in binary systems in which there is a phase transition-improper decay are obtained. For the first time, spinodal equations for a phase transition with one multicomponent order parameter (two one-component) are obtained.
Keywords: binary solutions, spinodal decay, structural phase transition
The article presents the results of studies of cobalt catalysts for the synthesis of hydrocarbons on a silicate support with promoting additives of aluminum, manganese and chromium. The influence of additives on the structural (specific surface area, dispersion of metallic cobalt, size of metal crystallites) and chemical (cobalt reduction degree) properties of catalysts was established.
Keywords: cobalt, catalysts, hydrocarbon synthesis, structural properties, promoters