Technological processes and material science. Рубрика в журнале - Siberian Aerospace Journal
Magnetic capacity in manganese sulfides with rare earth substitution Mn1-xRexS
Статья научная
Polycrystalline samples Mn1–xGdxS and Mn1–xYbxS with a concentration x = 0.2, near the concentration of ion flow through the fcc lattice, are studied in order to determine fluctuations in the valence of the ytterbium ion on dielectric properties. Dielectric constant and dielectric losses were determined from measurements of capacitance and loss tangent in the frequency range 102–106 Hz at temperatures of 80– 500 K without a magnetic field and in a magnetic field. The magnetic capacity and dielectric losses in the magnetic field of the sample were determined from the relative change in the real and imaginary parts of the dielectric constant of the sample in a magnetic field H = 12 kOe applied parallel to the capacitor plates. A temperature range with a sharp increase in dielectric constant and with a maximum dielectric loss has been discovered, which shifts with increasing frequency and magnetic field. An increase in dielectric constant and dielectric losses in a magnetic field above 170 K was found in Mn1-xYbxS. The increase in dielectric losses is explained by an increase in relaxation time, as a result of local deformations near ytterbium ions during valence fluctuations. The mechanism for reducing reactance in a magnetic field in Mn1–xYbxS at low frequencies due to capacitance, and at high frequencies due to inductance, has been determined. In the Mn0.8Gd0.2S compound, the imaginary part of the dielectric constant has two maxima. The low-temperature maximum shifts in a magnetic field towards high temperatures and is described in the model of localized electrons with freezing of dipole moments. Dielectric losses decrease in a magnetic field. The magnetic capacity decreases by an order of magnitude in Mn0.8Gd0.2S compared to Mn0.8Yb0.2S. The dielectric constant in both compounds is described in the Debye model with the activation dependence of the relaxation time on temperature, where the activation energies differ for ytterbium and gadolinium ions.
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Magnetic characteristics of iron nanoclusters
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The study of the nanocrystalline state, which significantly changes most of the physical characteristics of sub-stances, is very relevant. Of great practical interest are the works devoted to the study of the magnetic character-istics of nanocrystals of ferromagnetic substances. It has already been shown that the size of iron nanocrystals significantly affects the magnitude of their magnetization. Nevertheless, an adequate model of the structure of nanocrystalline formations consisting of a different number of iron atoms, which allows us to describe the exper-imentally detected changes in the magnetic characteristics, has not yet been presented. In this paper, we analyze nanocrystalline iron clusters that are different in configuration and number of their constituent atoms. Spatial models of clusters are constructed using a three-dimensional modeling program, and the coordinates of individual atoms in the cluster are determined. The proposed structures of nanocrystals are based on tetrahedrally close-packed cluster assemblies of iron atoms. The electron state density spectra were con-structed for the proposed clusters. For this purpose, the theory of the electron density functional was used, the calculation was carried out by the method of scattered waves in accordance with the band theory of crystals. It is shown that the appearance of magnetization in tetrahedral densely packed cluster formations is associat-ed with the excited electronic states of the atoms located on the surface of the nanocluster. Excited atoms have an increased electron density, that is, electrons are able to transition to states with higher energy, approaching the Fermi energy. In this case, the Stoner criterion necessary for the occurrence of magnetization is fulfilled. The con-figurations of electrons with spin up and down differ, which is why uncompensated magnetic moments appear. It is confirmed that the proposed models of iron nanoclusters satisfactorily correspond to the known experimental data.
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Magnetic impedance in nonstichiometric manganese sulfide
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The role of defects on the dynamic characteristics of manganese sulfide is studied by impedance spectroscopy in the frequency range 102–106 Hz and temperatures 80–500 K. Nonstoichiometry plays an important role in the formation of new transport and magnetic properties, as it leads to electrically inhomogeneous states. The phase composition and crystal structure of nonstoichiometric manganese sulfide were studied on a DRON-3 X-ray unit using CuKα – radiation at room temperature. According to X-ray diffraction analysis, the synthesized compound is single-phase and has a NaCl-type cubic lattice. From the frequency dependences of the impedance components measured in the absence of a field and in a magnetic field, the relaxation time of the current carriers in the Debye model is found. A sharp decrease in the relaxation time and its correlation with conductivity were found. The contribution to the impedance of the active and reactive parts of the impedance at frequencies below and above the relaxation time is established. The capacitance from the impedance hodograph in the equivalent circuit model is determined. In defective manganese sulfide, the temperature-dependent impedance has an activation character. The activation energy is determined in the range 250–500 K, which is attributed to the excitation energy of lattice polarons. The effect of a magnetic field on the dynamic characteristics of current carriers was studied as a result of a change in the impedance components in a magnetic field at fixed temperatures. The impedance increases in a magnetic field and reaches a maximum in the temperature range of charge ordering of vacancies. An increase in the impedance in a magnetic field is explained by a decrease in the diagonal component of the permittivity in a magnetic field in an electrically inhomogeneous medium. The experimental data are explained in the Debye model.
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Статья научная
Bismuth pyrostannate Bi2Sn2O7 is a diamagnet and belongs to the structural type of the A2B2O7 pyro-chlore class. In this class of compounds, in the presence of magnetic ions, very interesting magnetic proper-ties appear. Chromium- and iron-substituted bismuth pyrostannates Bi2(Sn0.9Me0.1)2O7, Me = Cr, and Fe were synthesized by solid-phase synthesis. X-ray diffraction analysis showed that the samples correspond to the Pc monoclinic cell of the Bi2Sn2O7 α-phase at room temperature. The magnetic properties up to 1100 K in magnetic fields up to 0.86 T and the electric polarization at frequencies of 10, 3, and 1 mHz in the tem-perature range 80–550 K have been studied. The effect of heterogeneous substitution by Cr3+ and Fe3+ ions on the magnetic properties and electric polarization of bismuth pyrostannate is investigated. An analysis of the experimental data revealed the dependence of the magnetic properties on the degree of filling of the elec-tron shells of chromium and iron ions. The Bi2(Sn0.9Cr0.1)2O7 compound exhibits ferromagnetic properties, while Bi2(Sn0.9Fe0.1)2O7 exhibits antiferromagnetic properties. In chromium-substituted bismuth pyrostan-nate during the α→β transition, the paramagnetic Curie temperature increases by a factor of 3. The temper-ature dependence of the inverse magnetic susceptibility is characterized by hysteresis in the temperature range of 400–900 K. The reverse magnetic susceptibility of Bi2(Sn0.9Fe0.1)2O7 in the entire temperature range is satisfactorily described by the Curie-Weiss law. Studies of the magnetic properties have established that the Fe3+ ions are in a high-spin state. The polarization hysteresis in Bi2(Sn0.9Cr0.1)2O7 is found, which shifts along the polarization axis and depends on temperature. Bi2(Sn1-xFex)2O7, x=0.1 is characterized by a linear field dependence. With an increase in the concentration of iron ions, a hysteresis arises in the field dependence of the electric polarization. The hysteresis of polarization in Bi2(Sn0.9Cr0.1)2O7 which depends on temperature was found. The nonlinear field dependence of the polarization in Bi2(Sn0.8Fe0.2)2O7 can be ex-plained by the interaction of the dipole and migration polarizations and the presence of oxygen vacancies. For the Bi2(Sn0.9Cr0.1)2O7 compound, a transition to the dipole glass state was found. In the β-phase of Bi2(Sn0.8Fe0.2)2O7 above T = 400 K, no polarization hysteresis is observed and the electron-relaxation polar-ization predominates. The mechanism of the occurrence of electronic polarization is explained with the ap-pearance of anionic vacancies upon heterogeneous substitution of tin ions.
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Magnetic properties of Mn1-xGdxSe sol-id solutions
Статья научная
Potential materials for spintronics operating under extreme conditions based on manganese selenides substituted with gadolinium are investigated. The technology of synthesis of solid solutions based on solid-phase reactions using MnSe and GdSe compounds is presented. As a result, Mn1-xGdxSe solid solutions with concentrations x = 0.05; 0.1; 0.15 and 0.5 were synthesized. The synthesis was carried out under vac-uum conditions of 10–2 Pa. The products of the primary synthesis were subjected to thorough grinding into powders, from which tablets were made under pressure for homogenizing annealing at 1370 K. After two hours of exposure, the synthesis products were tempered in cold water. At the final stage, homogeneous strong ingots of greyish-silver color were obtained. X-ray phase analysis of synthesized solid solutions of the Mn1-xGdxSe system was performed in Cu-K radiation in the point-by-point measurement mode with a scanning step along the angle Δ2θ = 0,03 degree; the time of information collection at the reference point Δτ =3 seconds. The spatial symmetry group and the parameter of the elementary crystal cell of solid solu-tions of the Mn1–xGdxSe system from X-ray diffraction analysis are determined. The dependence of the pa-rameter value of the crystal lattice of solid solutions on the concentration of gadolinium ions is found. The specific magnetization was measured by the ponderomotor method in a magnetic field with an induction of B = 0.86 Tesla and the magnetic susceptibility of the samples was determined in the temperature range of 80 ≤ T ≤ 950 K. The cycles carried out in the heating - cooling mode did not detect a change in properties. The Neel temperatures and the paramagnetic Curie temperature are determined from the Curie – Weiss law depending on the concentration of a rare earth element. A decrease in the temperature of the magnetic phase transition is established.
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Magnetoimpedance in thulium manganese chalcogenide
Статья научная
Control of transport characteristics under the influence of a magnetic field is promising from the point of view of creating magnetic field sensors resistant to radiation. The impedance and its components in thulium manganese chalcogenide in the frequency range of 102–106 Hz are studied. The temperature range with a prevailing contribution of the reactive and active parts of the impedance is found. The impedance components are described in the Debye model. When manganese is replaced by thulium ions, the frequencies of the maxima of the imaginary component of the impedance shift toward high frequencies in manganese selenide by two orders of magnitude. With an increase in the concentration of substitution by thulium ions in selenides, two relaxation times are found, compared with sulfides. The activation nature of the relaxation time, the activation energy from the concentration of thulium ions are found. An increase in impedance in a magnetic field in the region of low concentrations and a change in the sign of the impedance with temperature for high concentrations are established. Magnetoimpedance in chalcogenides passes through a maximum when heating the samples. The increase in impedance in a magnetic field is due to a change in the diagonal component of the permittivity in a magnetic field, which is proportional to the conductivity. A positive value of magnetoimpedance is described in the model of an electrically inhomogeneous medium. From the impedance, information can be obtained about the electrical inhomogeneity of the material.
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Статья научная
Operational characteristics of contacting elements of cars and mechanisms are by far defined by a layer quality indicators at the surfaces of contact. One of the ways of increasing details durability, including missile and space equipment details, is the superficial plastic deformation (SPD). In the article aspects of dynamic ways of hardening from the position of the wave theory of blow are considered. The construction of a shock stand on the basis of a linear electrodynamic drive with a size of 60 mm, operating in a shock-pulse mode, as well as a well-known mathematical model of the workflow – the movement of the armature with the tool at the moment of striking the surface. This model does not fully describe the operation process since the mass of the striker taken into account equaled 1 kg, which does not characterize the process of the impact tool, the purpose of which is the object deformation (for example, work hardening with the aim of surface material sealing or breakdown of the hole in it, or applying license plates markers). The mathematical model that describes the movement of the armature with the tool, taking into account the elastic deformation of the hardened surface was obtained. In the course of the performed calculation, the magnitude of the elastic deformation of the hardened surface was calculated from the dynamic component of the force impulse applied to it through the indenter (the tip of the impact tool). The layout of the shock stand with the equipment used, are offered. Experiments on the signal recording with various arrangements of piezoelectric transducers on the anvil – the hardened surface (diagrams of the sensors location are given) were carried out.
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Mathematical modeling of the flat ingot casting process for solving automation problems
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Aluminum alloys are widely used in the production of aircraft due to their strength, lightness, corrosion resistance, and necessary electrical conductivity. At the same time, aluminum ingots used in further processing of the space industry must be of high quality. Technological problems and defects arise when temperature, speed, and other technological parameters of casting are not observed, or when modes change. At the same time, foundry processes are partially automated; the human factor significantly affects product quality and work safety. Therefore, automation of these complex processes using mathematical models to predict casting parameters is an urgent task. The goal of the work is to create mathematical models available for use in automated process control systems (APCS), as well as for the development of a digital twin. The work presents simplified formulas for modeling the temperature distribution of an aluminum ingot during the casting process, cooling the metal when moving along a metal path, and test calculations of the temperature distribution inside the ingot when the ingot reaches a fixed length. The results of this work can be used to improve the efficiency and accuracy of controlling the process of casting aluminum ingots, to eliminate emergency situations.
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Статья научная
In this scientific work, a method of controlling high-frequency products from polymeric composite materials is considered. The authors of the work present the rationale for choosing a method of high-frequency diagnostics as the most suitable for non-destructive testing of products from polymeric materials of machine-building and rocket-space purposes. In the presented article, the primary task of creating and studying a mathematical model of the effect of highfrequency radiation on a polymer product, including those with a “metallic inclusion” defect, has been stated and solved. In addition, the work presents the calculations of diagnostic parameters using the mathematical model developed during the study. The calculation of the dynamics of heating the product and the temperature distribution during the control process is presented. The results of the calculation of specific power are described, the dependence of the instantaneous power consumption on the warm-up time is found. In the study based on a mathematical model, the Aleo- Diagnost software package was developed and registered, which is directly intended to ensure the functioning of the diagnostic devices and the investigation of the monitoring process. In addition, the developed complex allows solving a number of such practical problems as the calculation of the operating voltage depending on the geometrical parameters of the product and the determination of the value of energy consumed for monitoring the product for a specified period of time. This stage was necessary, as the consumed energy is the main output parameter of the diagnosis. In addition, the value of energy consumed is taken as the basis for the organization of the process of non-destructive testing in the automated mode. The solution of the tasks in this work has significantly reduced the cost of preparation of diagnostic operations, as well as improve the quality of control of products on an industrial scale at the stages of manufacture, operation and during repair work. The article also presents practical results, conclusions.
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Статья научная
The article contains the results of scientific research on modeling the technological parameters of electron beam welding. The modeling used a material VT-14 with a thickness of 0.16 cm. The purpose of the simulation is to improve the quality of the weld due to the optimal shape and the absence of defects in the form of pores and cracks. A concentrated energy source equivalent to an electron beam is used in the calculations. During the study of the thermal process of heating the material, the authors developed and tested criteria that allow optimizing welding parameters such as welding speed and the position of the focal spot relative to the surface of the heated part. In their calculations, the authors applied an original method of finding the welding speed and the coordinates of the focal spot according to the functionals of the thermal model. The algorithm developed by the authors was successfully tested on AMG-6 material with a thickness of 10 cm. In the process of modeling welding for large thicknesses, results have been obtained that must be taken into account when optimizing the welding parameters of products with large thickness. The relevance of the presented material is confirmed by the demand for the quality of the technology of welding structures with an electron beam. Research by the authors of this direction will significantly expand the possibilities in the application of electron beam technology for rocket and space technology.
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Статья научная
The results of the study of the damping capacity of manganese-copper alloys based on the Mn – 40 % Cu alloy with additives (0.5 – 1.5) % zirconium in the field of amplitude-independent damping are present-ed. Mn – Cu alloys with high damping capacity can be effectively used to reduce vibration and noise. Stud-ies on the influence of a number of alloying elements on the magnitude and stability of the damping capaci-ty of Mn – Cu double alloys in the field of small deformations of relative shear are not enough. In the pa-per, the influence of one of these elements, zirconium, was elucidated. Mn – Cu alloys were smelted in an induction furnace. From the ingots cast into cast iron molds, samples for studies with dimensions (11 × 15 × 117) ± 1 mm were obtained by mechanical cutting. The samples were subjected to aging at a temperature of 643 K for 0.5–40 hours. The damping capacity of Mn – Cu alloys (the logarithmic decrement of attenua-tion of oscillations) was studied for longitudinal oscillations of samples in the frequency range 14–17 kHz and the amplitudes of the relative shift (1 ... 3) × 10–6. It has been established that alloying the Mn – 40 % Cu alloy with zirconium from 0.5 % to 1.5 % does not increase its damping capacity in the cast state, as well as in the cast and aged at a temperature of 643 K for 40 hours. It was found that the minimum values of the frequencies of resonant vibrations of samples of Mn – Cu alloys correspond to the maximum levels of the damping capacity of these alloys. Itʼs shown that the high damping capacity of cast and aged alloys at 643 K for 40 hours Mn – 40 % Cu, Mn – 38.5–39.5 % Cu – 0.5–1.5 % Zr after natural aging at 293 K for 7 months decreases by 2.0–2.6 times.
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Статья научная
The analyzes of the requirements to 3D-configuration pipelines production at the rocket and space industry enterprises is done. A review of different approaches to pipe bending technology (with heat treatment and without heat treatment) is carried out. The object of the study is the bending process and a universal bending machine for pipelines’ production of complex configuration. The article is divided into four sections, which consider the key factors, causing directly the effectiveness of the technological operation of pipeline bending of a complex 3D-trajectory. An overview of no-temperature shaping of the pipeline is given in the first section. The requirements to the technology, excluding: corrugation, flattening, stretching and thinning of pipeline walls during their bending, are considered. The actual regulatory documents and industry aerospace standards, regulating production of pneumatic and hydraulic pipelines are given. An example of calculating the minimal allowable bend radius of the pipe, depending on the diameter and thickness of the pipe wall, is given. The requirements to unification of the pipe size production and gaps are listed. The dependence of the maximal allowable internal pressure in the pipeline is shown. The requirements to equipment, used in pipeline bending and to the design of the pipe bending machine are considered. In the second section, the possibilities of temperature influence on the pipe bending process are viewed. The analysis of patent and technical literature and six possible methods of effective thermal effects are presented: heating of the whole pipeline length, narrow zone heating of the bend pipe place, water cooling with nitrogen in the pipe, laser-cooling of atoms of the pipes, application of the petroleum products on the place of heating of the pipe and using of modern fillers inside the pipe to change its temperature. In the third section the tasks of the development of a universal bending machine are set; the system of the algorithm of the universal bending machine operation is considered; the system of algorithm of the bending machine operating with CNC is shown. The General functional scheme of the bending machine and the sequence diagram of the equipment operation is given.
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Plasmotron for coating internal surfaces of component parts
Статья научная
Plasma spraying is one of technologically appropriate, productive and effective methods of applying protec-tive coatings to component parts produced by aerospace, metallurgical and other industries, objects exposed to high temperatures, dynamic loads, aggressive media, etc. Plasma spraying makes it possible to apply quite a va-riety of materials, such as metals, oxides, carbides, nitrides, etc. to different surfaces. Certain problems may arise, though, in applying protective coatings to the inner surfaces of cylinders and complex parts of small size (about 100 mm). These complexities depend on the dimensions of the plasma generator proper. There are no home-produced small-size plasma torches, they are all imported from other countries. That causes certain prob-lems with delivery, to say nothing of very high commercial price. One of the ways to improve the situation is to develop small-size plasmatrons capable of applying high-quality coatings to the internal surfaces of limited-size parts; that may significantly reduce expenses through import substitution. The effectiveness of the proposed device is in working out a method of applying high-quality coatings to the inner surfaces of orifices as small as 60 mm in diameter (operating a plasmatron of smaller size), as well as in significant cost reduction due to domestic production. Sample calculations show that the price of that plasma-tron type will not exceed 0.5 million rubles.
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Point defects in nematic liquid crystal materials with conical anchoring at the interface
Статья научная
The topological point defects in nematic liquid crystal materials have been studied. The method of oblique light incidence has been proposed to determine an azimuthal director angle of an achiral nematic as well as a chiral nematic (cholesteric). The idea of the method is based on the dependence of the optical phase difference between ordinary and extraordinary light beams on the azimuthal director angle at the layer center at oblique incidence of light on a structure in which the polar director angle of a nematic liquid crystal is not equal to 0° or 90° (conical boundary conditions). It has been shown that the phase difference reaches a maximum at a zero azimuthal angle at the center of the layer regardless of the total twist angle of the director. The developed method has been used to analyze topological defects formed in the nematic and cholesteric layers under conical boundary conditions at the interface. The director field distributions of nematic and cholesteric near the surface point defects (boojums) with topological charges m = +1 and m = –1 have been drawn based on the experimental data. The proposed method of oblique light incidence can be used to analyze a wide class of the achiral and chiral liquid crystal media of various types: smectics, nematics, and cholesterics with tilted or hybrid boundary conditions.
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Prediction of formation of competing phases during the growth of Cr2GaC THIN FILMS ON MgO(111)
Статья научная
MAX-phases are a family of ternary layered compounds with the formal stoichiometry Mn+1AXn (n = 1, 2, 3...), where M is a transition d-metal; A is a p-element (for example, Si, Ge, Al, S, Sn, etc.); X is carbon or nitrogen [1]. Layered triple carbides and nitrides of d-and p-elements (MAX-phases) exhibit a unique combination of properties characteristic of both metals and ceramics, which makes their application as various coatings in space industry very promising. Obtaining the desired properties of the MAX-phases depends on the technological conditions of material synthesis. This requires thorough theoretical modelling of the elements’ interaction at the interface. Concurrent growth of competing phases along with the MAX-phase may occur due to the favorability of competing phases’ formation and may also be promoted by lower energy interfaces with the substrate in comparison with a MAX-phase. In this work, we study thermodynamic favorability of competing phases and Cr2GaC MAX-phase depending on the chemical composition of the atomic flow. To study these compounds, it was necessary to consider the Cr-Ga-C system. According to the effective heat of formation model, each reaction of a certain phase formation can be characterized by enthalpy [2]. To find out the most favorable phases, it was necessary to calculate the enthalpy of all possible reactions. Thus, the task was to sort through all possible reactions between pure elements available in various ratios, in particular, in the ratio corresponding to the given MAX-phase stoichiometry, i.e. Cr:Ga:C=2:1: 1. Moreover, it is considered that the density of near-coincidence sites [3,4] for interfaces between MAX-phase, thermodynamically favourable competing phases and MgO(111) surface shows a role of the interface in the determination of the structural quality of the MAX-phase thin film grown on MgO(111).
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Production of finly despersed powder from graphite by electrolysis
Статья научная
Multifunctional coating is a multi-layer structure applied to the surface of an aircraft to protect it from external influences. The main tasks of the multifunctional coating are: restoration of properties, overall dimensions, mass of the surface of the product, which were violated under operating conditions; changing the initial physical, mechanical and chemical properties of the product surface to ensure the specified operating conditions. Today multifunctional coatings based on micro glass spheres with applied tungsten are widely used in aerospace engineering. However, this coating has a number of disadvantages: the coating layers heterogeneity; the composition contains a harmful and dangerous component – a fluorone dye. In this article it is suggested to replace the main component of a multifunctional coating with finely dispersed graphite powder obtained by electrolysis. For this purpose, the equipment based on the principle of a diaphragm electrolyzer was constructed. The main elements of the device are a stainless steel cathode and a graphite anode immersed in an aqueous solution. As a result of anodic processes, a finely dispersed graphite powder was obtained. The average particle size of the resulting graphite particles is 4 microns. This finely dispersed graphite powder can be used as the main component of a multifunctional coating in aircraft, since it has an even homogeneous structure, as well as higher values of the main mechanical properties of a multifunctional coating.
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Статья научная
The paper presents the results of studying the shielding properties of thin transparent films in single-walled carbon nanotubes on flexible substrates of polyethylene terephthalate. The films were formed by spraying colloidal solution on single-walled carbon nanotubes. The film thickness was determined by the volume of the sprayed colloidal solution and was measured using transmission electron microscopy in a cross-section mode. The morphology and structural quality of the films were studied by electron microscopy, optical spectroscopy, and Raman spectroscopy. The results showed the high structural quality of the material. According to Raman spectroscopy, the ratio of peaks intensities G / D is 23.4, which is the evidence of a significant predominance of carbon in the sp2 hybridization. It is typical for graphitelike systems and, in particular, carbon nanotubes. The spectral dependences of the transmission and reflection coefficients of radio waves in the K range of 18–26.5 GHz were studied. Absorption of radiation is the dominant shielding mechanism. Increasing the film thickness from 15.9 to 56.1 nm is accompanied by decreasing the surface resistance from 971 to 226 Ohm / sq, while optical transparency decreases from 93.58 to 76.71 %. Shielding efficiency increases from 2.29 to 6.6 dB, increasing the proportion of absorbed radiation from 34.6 to 51.2 % at a frequency of 18 GHz. This indicates the prospects for the use of films as electromagnetic shielding and anti-icing coatings in the aerospace industry.
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Статья научная
Waffle shells are the main part of the overall dry mass of the products of the aerospace industry. Cell bottom thickness and the width of the longtitudal and circular edges are the main characteristics of the waffle grid. Mechanical cutting by using of the machine tools of SVO series which perform tracking and copying of the opposite wall thus providing the stability of the bottom thickness despite of the workpiece shape errors is the most wide-spread technology of the manufacturing of the waffle grid. There are different other factors which act during such a process and lead to bottom thickness and edge width errors which brings to increase of the weight of the part, use of the additional finishing operations and rise of the defects amount during milling process. Thus it is essential to solve the problem of the increase of the machining accuracy of the cell thickness bottom, which might cause the rise of the machining performance and might help to raise the quality of waffle shells. In order to do this, authors examine in detail the waffle grid mirror milling manufacturing process. The factors which lead to the cell bottom thickness deviations were described and classified. It was analyzed and shown in the paper that deviations of the spindle axis against the surface normal affect the magnitude of cell bottom thickness errors. Authors also perform the mathematical modeling of cell bottom thickness errors because of presence of backlash in tracking system. The paper presents a detailed description of various techniques to increase the machining accuracy of the cell bottom. It was demonstrated that the most suitable is to use the combined digital compensation method by using of self-tuning system. Implementation of the solution will enhance the mass-energy properties of the aerospace products by means of decrease of the overall dry mass by attainment the higher cell bottom machining accuracy. It also will bring to raise of the quality and reliability of production by reducing the defects amount. The mirror milling machining process was considered. The factors leading to the thickness er-rors of the pocket bottoms were classified. Perfomed the simulation of the thickness errors genera-tion caused by the influence of the most significant factors. Techniques to increase the accuracy during machining of the pocket bottoms were analysed, provided the reason of using the combined digital correction method with self-tuning from pass to pass.
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Research on electrical properties of manganese sulphides doped by thulium and ytterbium ions
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Materials exhibiting connection between electrical and magnetic properties are attractive for possible use as an element base in microelectronics, spintronics, and sensor devices. Compounds with mixed valence exhibit a number of metal-insulator phase transitions, magnetic phase transitions, including changes in magnetic properties without changing magnetic symmetry. Promising materials for studying these effects are cation-substituted Mn1−xRexS compounds (Re = 4f elements) synthesized on the basis of the antiferromagnetic semiconductor of manganese monosulfide. The latter is of practical importance in the development of new materials for temperature sensors, widely used in the metallurgical industry. The structural and electrical properties of compounds with mixed valences TmXMn1-ХS (0 ≤ X ≤ 0.15) and TmXMn1-ХS (0 ≤ X ≤ 0.25) were studied in the temperature range 80–1100K. The regions of existence of solid solutions of TmXMn1-XS sulfides with an fcc (face-centered cubic) lattice of the NaCl type were determined. It was found that conductivity decreases upon the substitution of manganese cations with thulium ions and the lattice constant increases more sharply in comparison with Vegard’s law. When ytterbium ions are substituted, the conductivity increases with increasing concentration and the temperature dependence has the form typical of semiconductors.
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Instruments measuring the Earth's magnetic field are widely used in the space industry. Increasingly, loworbit spacecraft orientation and stabilization systems include magnetometers manufactured using magnetoresistive technology. This is justified by the low weight, size and consumption of such devices, which makes them ideal for use on small-sized spacecraft. However, the main problem of magnetoresistive magnetometers is the need to estimate possible measurement errors. The influence of errors significantly reduces the accuracy characteristics of the device. In order to solve the problem, researchers propose various methods for evaluating and eliminating the influence of errors on measurements [1–7]. Among the ways to eliminate errors in the readings of the device, constructive solutions are used, such as putting the device at a distance from the spacecraft using a retractable boom, in order to reduce the influence of interference on the device from the apparatus [2]. Such a solution is advisable for large spacecraft, where the presence of a retractable boom will not complicate the design and will not increase energy consumption. For small spacecraft, such a solution is not advisable, for this reason, when discussing small-sized spacecraft magnetometers, much attention is paid to calibration methods, mathematical evaluation and error correction, both in ground and in flight conditions. The objectives of the article include the formation of a general understanding of the causes of distortions in the readings of anisotropic magnetoresistive magnetometers, methods of their mathematical evaluation. A review of methods and equipment for ground calibration is carried out. The characteristics of the calibrated parameters of magnetometers are given and a mathematical model of measurement of the device is proposed, taking into account errors. The basic operations and equipment used in the calibration process are described. The results of the work can be useful in designing workplaces for calibrating magnetometers, as well as in conducting empirical research in the field of magnetometric sensors.
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