Volume 24 № 1 2022
1. Tatyana S. Kartapova, Faat Z. Gil’mutdinov, Marina A. Eryomina, Andrey A. Kolotov
Influence of Ion-Beam Effects on the Electrical Conductivity of Thin Carbon Films on Insulating Substrates P. 5-17. Download.
In the present paper, the chemical composition and atomic structure of carbon films were studied by X-ray photoelectron spectroscopy and Raman spectroscopy. The thickness and topography of the obtained coatings were estimated by atomic force microscopy. The resistivity of carbon films was measured. Carbon films on a glass slide were obtained by magnetron sputtering in an argon atmosphere. The obtained carbon films were irradiated with N+ and Ar+ ions with the energy of 30 keV. The fluence for argon and nitrogen ions was 5·1016 ions/cm2 and 1017 ions/cm2. The experimental data of Raman spectroscopy and XPS did not reveal significant differences in the composition and structure of carbon films at the depth of the analysis. It should be noted that there is similarity between the Raman spectra of the initial carbon film and the film irradiated with argon at the maximum dose. It is shown, that under low fluence (5∙1016 ion/cm2; 30 keV) irradiation with argon and nitrogen, the electrical insulating properties of carbon coatings can be improved. The value of the electrical resistance can increase to 10 MΩ. Ion-beam processing can be used in a targeted manner to form carbon films and coatings with desired electrical conductivity. According to the AFM and scanning electron microscopy data, the carbon films are continuous without islands and breaks. There is a correlation between changes in the electrical resistivity of the carbon films and AFM data, which show a possible relationship between a particle size and insulating properties. It is assumed, that the chosen parameters of the ion modification lead to the radiation-thermal effect. As a result of annealing the disordered structure, coagulation of particles and partial graphitization of the film occur.
2. Vladimir G. Lebedev, Vitaly A. Kopytov, Vladimir I. Ladyanov
Isothermal Phase-Field Model of Solid-State Transformations with Elastic Stresses P. 18-32. Download.
The article proposes the thermodynamically consistent model of phase transitions in solid media for the case of pure substances. As a source of elastic stresses, the change in the density of a continuous medium during the phase transformation is considered; the dependence of the phase densities on temperature is obtained from the approximation of the experimental data. In this approach, the density of the substance of each phase is described by its own equation assuming that when the interphase moves, the substance of the decreasing phase is captured by the growing phase. The effect of the change of the crystal structure orientation is not considered in this approach. The proposed model is based on the phase field method and describes the interaction of phase transformations with elastic stresses caused by changes in the density of the matter in phases. The thermodynamic description of individual phases is based on the experimental Gibbs potentials. The limiting cases of the obtained model correspond to the isothermal phase-field model in pure substances and the model of thermo-elastic stresses. The model is used for the numerical analysis of the growth of a spherical ferrite embryo from austenite and can be the basis for taking into account stresses in the processes of the internal structure formation in metal solutions, in particular, dendrites. The diagrams of the phase field profiles and strain displacements obtained as a result of the numerical calculation are presented.
3. Nikolay G. Galkin, Konstantin N. Galkin, Igor M. Chernev, Oleg V. Kropachev, Dmitrii L. Goroshko, Evgenii Y. Subbotin and Dmitri B. Migas
Crystalline Structure, Optical Properties and Band Gap Nature of Semiconductor Ca2Si Films on Al2O3 Substrate P. 33-44. Download.
Nanocrystalline Ca2Si films on Al2O3(0001) were formed for the first time by converting a consumable 2D Mg2Si layer into a Ca2Si template with the preliminary formation of an amorphous 2D Si layer. It has been established that a Ca2Si template on a sapphire substrate makes it possible to grow oriented Ca2Si films by molecular beam epitaxy (MBE) at a temperature of 250 °C, for which one epitaxial ratio is observed: Ca2Si(211)/Al2O3(0001). The studies of the optical properties and parameters of the Ca2Si band structure on the sapphire substrate revealed the nature of the direct fundamental transition with the energy of 0.88±0.01 eV. It has been established that four direct interband transitions are observed in the band structure of Ca2Si: 0.88, 1.16, 1.49, and 1.61 eV with increasing oscillator strength. At photon energies from 0.78 eV to 0.88 eV, the main contribution to absorption is made by the Urbach tail on defects in Ca2Si nanocrystals. Absorption at grain boundaries is observed at photon energies from 0.6 eV to 0.78 eV and on free carriers - at energies less than 0.6 eV. The results obtained are important for optoelectronics in the near-IR region of the spectrum.
4. Maria R. Koroleva, Olga V. Mishchenkova, Konstantin E. Simonenko, Aleksey N. Terentyev, Alena A. Chernova
Hydrodynamics of a Safety Valve Operation for a Low-Viscosity Liquid P. 45-55. Download.
A numerical study of the internal hydrodynamics of a safety valve operating in a regime close to critical has been carried out. Under these conditions the liquid viscosity significantly reduces, and its fluidity increases. Mathematical modeling was carried out based on the numerical solution of the Navier-Stokes equations for a viscous incompressible fluid using a quasi-stationary approach to describing the operation of a dynamic hydraulic system. One of the operating modes was studied when the properties (temperature, pressure, density) of the working fluid were closed to critical. The temperature of the liquid was Т = 0.8 Тc, static pressure was P = 0.22 Pc and density r = 2.8 rc. At this mode the dynamic viscosity coefficient equaled 3∙10-7 Pa·sec, and the saturated steam pressure was Ps = 0.144 Pc. The investigation of the design features of the safety valve elements has shown that they are responsible for the formation of the alternating zones of high and low pressure in the flow leading to cavitation. It is found that the stem geometry causes the formation of high and low pressure zones in the flow leading to cavitation and stem destruction. The diagrams of the relative pressure and velocity along the stem generatrix were built. The detailed diagram analysis shows the location of the dangerous flow zones where the cavitation zones can appear. In the experiment, the stem failure was also found in these areas. The numerical results permit to propose a new design of safety valve elements – a perforated disc and a stem with a smoothed outer profile. Numerical investigations of the new design of safety valve elements have been carried out. The analysis of the operation of the new disc with perforation and the new stem with a smoothed profile of the side surface has been performed. For the valves with perforated disc and with smoothed stem profile, the diagrams of the pressure and velocity along the stem generatrix were built. Both new designs reduce the cavitation effects. However, in the former case, the cavitation area is displaced along the disc, and in the latter case, one of the existing cavitation zones vanished, while the other is reduced. To reduce the effect of cavitation, a numerically justified transition to the stem with a smoothed surface is recommended.
5. Igor V. Zhurbin, Anna G. Zlobina, Alexander S. Shaura, Aigul I. Bazhenova
Statistical Analysis of Multispectral Imaging Data for the Reconstruction of Archaeological Sites P. 56-68. Download.
In the XX century, the territory of the absolute majority of archaeological sites in central Russia and the Urals was used as agricultural land. As a result of ploughing, the relief features of the structures were "smoothed out", and the destroyed occupation layer was redistributed throughout the settlement site. Such trends were noted in the study of medieval Finno-Ugric settlements. Areas of the occupation layer of different degrees of preservation are recorded: superficially disrupted, transported, and replaced layer. As a rule, the superficially disrupted and replaced layers are localized at the settlement site. The transported layer moves to the slopes of capes that limit the settlement site. This leads to the need to study the settlement site itself, as well as the adjacent territory. A new algorithm is proposed to restore the structure of the occupation layer of medieval settlements (without relief features). The first stage is the calculation of Haralick’s textural features. The second stage is the reduction of the number of features by the principal component analysis. The third stage is the segmentation of images by the k-means method. This procedure permits to divide the settlement site and adjacent territory into areas with a fundamentally different vegetation density. The comparison with the reference data (geophysical and archaeological studies, survey in the visible range, soil coring, etc.) allows us to interpret the selected areas. The research was carried out at the medieval fortified settlement Sadeykar (Glazovskii district, Udmurtia, Russia). The territory of the settlement has been plowed for a long time and currently the defensive structures (ditch and rampart) are not expressed in relief. As a result of the application of the proposed algorithm of the statistical analysis, the location of the areas of the occupation layer of various degrees of preservation was determined.
6. Nadezhda G. Bobenko, Yuriy A. Chumakov, Anna A. Belosludtseva
The Features of Fluorine and Hydrogen Adsorption on the Surface of Twisted Bilayer Graphene P. 69-81. Download.
In the present paper, the simulation method is used to study the structure of the original and defective twisted graphene with a large number of atoms. An algorithm for determining AA-, AB-, and BA-superstructures on a twisted graphene surface has been developed and implemented. The dependence of the concentration of fluorine and hydrogen on the twist angle has been studied for four adsorption centers (AA, AB, and fullerene-like structures C48 and C72). The maximum concentration of adsorbate atoms for complete coverage of the studied adsorption centers and the corresponding twist angles are found. Cowley's short-range order parameters are calculated. An analysis of these parameters shows that short- and long-range order is possible in fluorinated and hydrogenated twisted graphene at angles from 2° to 58°. The concentrations and rotation angles, at which foreign atoms are an impurity or form areas with short-range and long-range order, are determined from the calculated concentration dependences of the short-range order parameters. The results can be useful for determining the optimal rotation angles for layers in twisted graphene, which are more or less subject to surface functionalization by fluorine and hydrogen. The investigation carried out is important for studying the functionalization of materials with a hexagonal structure and similar adsorption centers. The obtained qualitative agreement between the experimental and theoretical data on the study of the processes of hydrogenation and fluorination of twisted bigraphene confirms the applicability of the proposed approach to solving the problems.
7. Larisa S. Goruleva, Evgenii Yu. Prosviryakov
A New Class of Exact Solutions to the Navier-Stokes Equations with Allowance Made for Internal Heat Release P. 82-92. Download.
New exact solutions to the three-dimensional Navier-Stokes equations, where the heat transfer equation takes into account energy dissipation in a moving fluid, are discussed. The flows of viscous incompressible fluids can be in both steady- and unsteady-state. The construction of the exact solutions is based on the Lin-Sidorov-Aristov class of exact solutions. The characteristic feature of the velocity field representation is that it is described by linear forms with respect to two coordinates (horizontal or longitudinal). The coefficients of the linear forms depend on the third coordinate (vertical, or transverse) and time. The fluid pressure and temperature are quadratic forms with a similar structure for the velocity. This family of exact solutions describes the flows of viscous incompressible fluids with a spatial acceleration. In other words, nonlinear effects of inertia forces are taken into account, which are expressed through the convective derivative of the velocity and temperature vectors in the Navier–Stokes equations and the heat conduction equation, respectively. Since there is energy dissipation in fluids, two quadratically nonlinear effects compete. This significantly complicates the study of flows; therefore, the paper presents formulas describing a creeping flow (the Stokes approximation) and Oseen motion. Thus, the study shows the possibility of constructing exact solutions to the motion equations with mechanical energy dissipation into thermal energy for the full Navier–Stokes equations and for their linearized analogs in the Stokes and Oseen approximations.
8. Aleksej Yu. Armyanin, Elena S. Baymetova, Mikhail E. Hval'ko
Peculiarities of the Thermal Regime of an Oil Cooler with a Developed External Surface P. 93-103. Download.
For removing excess heat from working fluid, which forms during the hydraulic system operation in periodic modes, special convective heat exchangers such as oil coolers, the geometry of which directly affects their efficiency, are required. In this paper, we consider the issues of thermal regimes in flow paths and the body of an industrial oil cooler. The object of the study is a multi-section collector with a complex cross-sectional shape of the liquid supply channels and with a developed outer surface for effective cooling. The cooling section is made in the form of a flat tube with longitudinal inner channels with rectangular cross-sections, in which additional longitudinal ribs are placed to provide machine oil flow turbulence. It allows intensifying the heat exchange between the viscous medium and metal wall by preventing the formation of a laminar boundary layer. The heat-exchanger outer surface is equipped with multiple double-sided ribs to increase the device heat efficiency. By methods of mathematical modeling, the problem of conjugate heat exchange in the oil cooler channels and body is solved. The models of a heat-conducting viscous incompressible fluid, heat-conducting viscous compressible gas and heat conduction in a solid are used. The discretization of the basic equations is carried out by the finite volume method using the Open source product openFoam. As a result of the computational experiment, the realized thermal and aero-hydrodynamic modes of operation of a single element of the cooling section are revealed and described. The uneven heating of the cooling section body is shown. On the basis of the analysis of the obtained fields of gas-dynamic and thermophysical values the expediency of the constructive optimization of the external finning design is shown.
9. Nikita E. Suksin, Marina A. Shumilova, Irina S. Kazantseva
Galvanic Production Waste as a Raw Material for Obtaining Corrosion Inhibitor Sodium Nitrilotrismethylenephosphonatozincate P. 104-110. Download.
As a result of the processing of galvanic-chemical production waste, ZnO was obtained, which is a raw material for the production of a corrosion inhibitor – sodium nitrilotrismethylenephosphonatozincate (Na4[N(CH2PO3)3Zn]∙13H2O). The studies of the protective ability of this compound for steel of various grades in an acidic environment were carried out. The essence of the method was to determine the mass loss of steel samples when they were placed in test media; after that, the inhibitor protective ability was assessed by changing the corrosion rate. The samples were polished with sandpaper with a successively decreasing abrasive grain size until the surface was smooth and shiny; after that they were washed with tap water, wiped with filter paper, rinsed with distilled paper, degreased with alcohol, dried, and weighed on a VLR-200 analytical balance with an error of ±0.05 mg. The prepared samples, suspended on a fishing line, were placed in glass vessels with a 10 % aqueous solution of iron trichloride hexahydrate (corrosive medium), the volume of which should be at least 10 cm3 per 1 cm2 of the surface area of the samples. The duration of the tests carried out under stationary conditions at room temperature was 24 hours. According to the results of the accelerated chemical determination of the resistance of the steel samples to electrochemical corrosion under standard conditions, the maximum specific rate was recorded for L6 steel grade; slightly lower corrosion rates are characteristic of grades 5117, 150Cr14 and 1066. There is practically no corrosion process in structural steel 321H, since it has a minimum iron content compared with the other studied grades and significant amounts of chromium, nickel and, also, the presence of titanium. The study of the inhibiting properties of Na4[N(CH2PO3)3Zn]∙13H2O in a corrosive environment with respect to the considered steel grades showed that the coordination compound has such properties. The inhibitor exhibits the best protective effect for all steel grades in the corrosive medium concentration in the range from 1 to 5 mg∙dm-3; a further increase in the concentration leads to a decrease in the protective effect. It is established that the isolated zinc oxide can be effectively used to obtain a coordination compound with inhibiting properties.
10. Pavel V. Gulyaev, Evgeny Yu. Shelkovnikov
Search and Recognition of the Studied Area in Probe Microscopy Using Markings Applied by Power Lithography or Nanoindentation P. 111-120. Download.
The article describes the processes of marked zone searching and recognition in scanning probe microscopy. The initial positioning of the probe with the help of an optical microscope and the subsequent marked zone searching by a series of overlapping scans are considered. The set of imprints (reference labels) applied with the help of a nanoindenter or a microscope cantilever is considered as marking. The imprints were applied at the corner points of the studied area. Typical images of imprints are given. It has been established that the main elements that make it difficult to recognize images of imprints are the presence of pile-ups and similar elements of the background relief. The analysis of the possibilities of conventional processing methods for highlighting image key points associated with reference labels is carried out. It is shown that the effectiveness of conventional methods can vary depending on the type of an image and the presence of noise. Based on the preliminary studies, it is proposed to use a template matching method for searching for image key points, as well as a structural analysis of the selected key points for determining their relation with marking imprints. It is established that the template matching method will be effective if key points are subjected to filtration. It is proposed to use local extremes of the cross-correlation function as image key points. An algorithm for such filtration is presented based on varying threshold values of the correlation coefficient and the size of the neighborhood of a key point. For the recognition of marking imprints, a structural analysis method based on the determination of distances between special points of the image is proposed. The results of recognition for various types of images are presented. The operability of the proposed algorithms in the presence of destabilizing factors is confirmed.
11. Andrey A. Shushkov, Polina E. Yanikaeva, Alexander V. Vakhrushev
Comparative Analysis of the Physical and Mechanical Properties of Surface Layers up to 200 nm of Cast Iron Grades A48-30B, 60-40-18 P. 121-129. Download.
A study and comparative analysis of the physical and mechanical properties of the surface layers up to 200 nm deep of gray cast iron A48-30B with lamellar graphite and ductile iron 60-40-18 with nodular graphite were carried out. A "strongly hard" phase with the similar hardness values was found on the surface areas of the two samples under study. For the samples, the average value of the studied "strongly hard" area hardness was Н60-40-18 = 34.71±12.23 GPa and НA48-30B = 34.57±14.56 GPa. It was found that without taking into account the areas with the "strongly hard" phase, the A48-30B sample had the average value of hardness
НA48-30B = 8.96±6.93 GPa, which was 65 % higher than the average value of the 60-40-18 sample hardness
Н60-40-18 = 5.43±2.57 GPa. The sample A48-30B had the average value of the plasticity index
PIA48-30B = 0.66±0.15 GPa without taking into account the "strongly hard" phase and the 60-40-18 sample had PI60-40-18 = 0.72±0.11 GPa . Thus, the surface of the 60-40-18 alloy cast iron sample is 9 % more ductile. Without taking into account the "strongly hard" phase, the elastic recovery parameter of the A48-30B and 60-40-18 sample was ERPA48-30B = 0.23±0.13 GPa and ERP60-40-18 = 0.17±0.08 GPa, respectively.