The sequence of phase transformations in the process of crystallization of the Sr₂CrMoO₆ by the solid-phase technique from a stoichiometric mixture of simple oxides SrCO₃ + 0.5Cr₂O₃ + MoO, has been investigated. It was determined that the synthesis of the strontium chrome-molybdate proceeds through a series of sequential-parallel stages. By means of the differential thermal analysis and thermogravimetric analysis data, it has been established that five clearly expressed endothermal effects were observed in the temperature range 300—1300 K. It was found that during the studies of the phase transformations sequence in the process of the double perovskite synthesis, SrCrO₃, SrMoO₄ and Sr₂CrO₄ are the main concomitant compounds. Herewith, it has been observed that with the annealing temperature increase from 300 to 1270 K, the complex compounds SrCrO₄, SrCrO₃ (350—550 K) and SrMoO₄, Sr₂CrO₄ (600—750 K) are emerging initially and practically simultaneously. It has been revealed with a subsequent temperature increase that in the temperature range 940—1100 K, the SrMoO₄, Sr₂CrO₄ and SrCrO3 phase concentration dramatically drops with the emerging and growth of the Sr₂CrMoO_6-δ double perovskite. With that in the range up to 1120—1190 K, the main XRD reflexes intensity for the SrCrO₃ and SrMoO₄ lowers substantially, and their content in the samples at 1170 К is no more than 7,9 %. During a consideration of the derivative of the SrCrO₃, SrMoO₄ and Sr₂CrO₄ phase transformation degree (|(dα/dt)|mах), at which their crystallization rates are maximal, it has been determined that |(dα/dt)|_mах for the Sr2CrO4 corresponds to the maximal temperature 1045 K, which indicates the presence of considerable kinetic difficulties at the formation of the Sr₂CrO₄ phase. Thereafter this phase does not disappear and at its appearance the slowing down of the double perovskite growth takes place. On the base of investigations of the phase transformations dynamics for the obtaining of the single-phase Sr₂CrMoO_6-δ compound with the superstructural ordering of the Cr/Mo cations and improved magnetic characteristics, the SrCrO₃ and SrMoO₄ precursors were used with combined heating modes.

The process of growing silicon single crystals by the Czochralski method has been improved, which involves the use of two argon streams. 1st, the main flow, 15—20 nl/min, is directed from top to bottom along the growing single crystal. It captures the reaction products of the melt with a quartz crucible (mainly SiO), removes them from the chamber through a nozzle in the lower part of the chamber and provide dislocation-free single crystals from large loads. Similar processes are known and widely used in world practice since the 1970s. 2nd, additional flow, 1.5—2 nl/min, is directed at an angle
of 45° to the surface of the melt in the form of jets from nozzles arranged in a ring. This flow initiates the formation of a region of turbulent melt flow, which isolates the crystallization front from convective flows enriched with oxygen, and also enhances the evaporation of carbon from the melt. It is confirmed that the oxygen evaporated from the melt (in the form of SiO) is a «transport» for non-volatile carbon. Carrying out industrial processes showed that the carbon content in the grown single crystals can be significantly reduced, up to values smaller than in the feedstock. In single crystals grown using two argon streams, an increased macro- and micro-uniformity of the oxygen distribution, a significantly larger crystal length with a given, constant oxygen concentration, were also recorded. Achieving a carbon concentration of 5 to 10 times less than in the feedstock is possible with small amounts of argon for melting (15—20 nl/min compared to 50—80 nl/min used in conventional processes. The use of an additional argon flow, which has an outflow intensity 10 times lower than that of the main flow, does not distort the nature of the flow around the single crystal surface (“axial”), does not disrupt the growth of a dislocation-free single crystal, does not increase the density of microdefects, which indicates the absence of changes in temperature gradients and thermal shock leading to thermal stresses in a single crystal.

Features of development and application of methods for performing refractive index measurements based on multi-angle spectrophotometric reflection methods are considered. The influence of the shape, size, and surface treatment of samples on their spectral reflection dependences is described. It is shown that it is possible to determine the refractive coefficients using two spectrophotometric methods: the reflection spectrum from one face at a small angle of incidence of light close to normal, and the reflection method at the incidence of light at the Brewster angle. The method of reflection at an angle of incidence close to normal can be used in the case of a non–absorbing sample characterized by an extinction coefficient not exceeding (10^-6—10^-4). This method is an «express method», because it allows you to immediately obtain the dispersion dependence of the refractive index. The method allows us to measure the dispersion dependences of refractive coefficients for samples whose shape excludes multiple reflections — plates with one polished side; plates of large thickness, polished on two sides; prisms or plates with non-parallel faces. When measuring using the Brewster method, there are no requirements for the value of the extinction coefficient of the sample (absorption), you can use a sample of any shape, including polished plates on both sides. However, the resulting values of refractive indices are discrete, and a large array of measurement results must be accumulated. The measurement accuracy of both methods was determined, which is Δ = ±0,001 with a confidence probability P = 0,95. The applicability of spectrophotometric measurement methods is shown for samples of gadolinium-aluminum-gallium garnet, which is related to cubic crystals, characterized by the presence of a single refractive index. It is shown that the values of the refractive indices obtained by these two methods are well correlated within the accuracy of measurements.

An original modification of the directed crystallization method is considered as a multi-cassette process, which has comparative simplicity and high productivity. The basis of this research was domestic patents and technological research carried out at the National University of Science and Technology MISIS. As a result, mathematical models of the multi-cassette method were developed that allow both a three-dimensional radiative — conductive analysis of thermal processes in the entire volume of the hot zone and a two-dimensional analysis of convective — conductive heat transfer in a separate cassette. The parametric calculations carried out on their basis were aimed to the identifying an influence of locations and sizes of the hot zone components to a thermal field in the cassette unit; the establishing an influence of vertical heat supply equability to the cassette unit and an influence of heating power decrease during the plate crystallization, as well as to the determining an influence of small cassette design distortions and violation of cooling uniformity in its bottom part on the occurrence of convection and asymmetrical thermal field. By means of the conductive-radiative heat transfer model for the entire hot zone there were carried out parametric calculations and it was analyzed an influence of hot zone components (their locations and temperatures) on the heat exchange conditions at the cassette unit boundaries. By means of the conductive-convective model for a cassette it was determined that the boundary thermal conditions asymmetry, as well as an unstable vertical temperature gradient, result in the convective vortices and a significant deviation of the crystallization front from a flat shape. The calculations with using the convective mass transfer model showed that an increase of the crystallization rate by an order significantly increases a tellurium flux into the crystal, thereby substantially changing a melt composition near crystallization front and, thus, being a potential cause of dendritic growth. The reliability of the calculation results was checked on a number of tests, in which the influence of heat and mass transfer on the crystallization front shape was analyzed at cassette cooling rates corresponding to the growth processes of bismuth telluride polycrystals.

In this work, we calculate the effective thermal conductivity coefficient for a binary semiconductor heterostructure using the GaAs/AlAs superlattice as an example. Different periods of layers and different ambient temperatures are considered. At the scale under consideration, the use of models based on the Fourier law is very limited, since they do not take into account the quantum-mechanical properties of materials, which gives a strong discrepancy with experimental data. On the other hand, the use of molecular dynamics methods allows us to obtain accurate solutions, but they are significantly more demanding on computing resources and also require solving a non-trivial problem of potential selection. When considering nanostructures, good results were shown by methods based on the solution of the Boltzmann transport equation for phonons; they allow one to obtain a fairly accurate solution, while having less computational complexity than molecular dynamics methods. To calculate the thermal conductivity coefficient, a modal suppression model is used that approximates the solution of the Boltzmann transport equation for phonons. The dispersion parameters and phonon scattering parameters are obtained from first-principle calculations. The work takes into account 2-phonon (associated with isotopic disorder and barriers) and 3-phonon scattering processes. To increase the accuracy of calculations, the non-digital profile of the distribution of materials among the layers of the superlattice is taken into account. The obtained results are compared with experimental data showing good agreement.

The article is devoted to the problem of solving scientific problems in the field of high-performance computing systems. An approach to solving a certain kind of problems in materials science is the use of mathematical modeling technologies implemented by specialized modeling systems. The greatest efficiency of the modeling system is shown when deployed in hybrid high-performance computing systems (HHPC), which have high performance and allow solving problems in an acceptable time with sufficient accuracy. However, there are a number of limitations that affect the work of the research team with modeling systems in the HHPC computing environment: the need to access graphics accelerators at the stage of development and debugging of algorithms in the modeling system, the need to use several modeling systems in order to obtain the most optimal solution, the need to dynamically change settings modeling systems for solving problems. The solution to the problem of the above limitations is assigned to an individual modeling environment functioning in the HHPC computing environment. The optimal solution for creating an individual modeling environment is the technology of virtual containerization. An algorithm for the formation of an individual modeling environment in a hybrid high-performance computing complex based on the «docker» virtual containerization system is proposed. An individual modeling environment is created by installing the necessary software in the base container, setting environment variables, installing custom software and licenses. A feature of the algorithm is the ability to form a library image from a base container with a customized individual modeling environment. In conclusion, the direction for further research work is indicated. The algorithm presented in the article is independent of the implementation of the job management system and can be used for any high-performance computing system.

The effect of passivating ALD Al₂O₃, SiN_x and SiON coatings of different thicknesses on the change in the charge and density of states of AlGaN/GaN heterostructures are studied. The electrophysical parameters of the structures were evaluated using C-V characteristics measured at different frequencies and I-V characteristics. Based on the considered zone diagrams of structures with different control voltages and the evaluation of the elemental composition of the films by Auger spectroscopy, it was shown that the cause of the formation of a large positive charge upon deposition of ALD Al₂O₃ and SiN_x films is the appearance of an additional piezoelectric charge in the AlGaN buffer layer. It is shown that the use of SiON films with an oxygen concentration of more than 3% does not lead to the formation of an additional positive charge, but can cause current fluctuations when measuring I-V characteristics. A possible mechanism of carrier transport in the SCR region, leading to such fluctuations, is considered.

In this paper, promising nanocomposite materials based on carbon and titanium are considered. It is shown that the use of a highly porous matrix is of particular interest. Materials based on such matrices have minimal weight and high strength characteristics. The paper also describes composites based on porous carbon fibers with metal oxides. The directions for producing composites can be divided into three types: matrix method, coating of finished nanoparticles with an inert shell, and the formation of nanoparticles and matrices in one process. The coating of nanoparticles with an inert shell prevents their oxidation and preserves the necessary magnetic properties. When using methods such as IR pyrolysis, arc evaporation forms third-party metal-carbon phases that pollute the resulting material. To avoid this, reducing agents are used, for example, hydrogen when coking nanoparticles in a methane plasma current restores metal particles from its Sol-gel and prevents them from reacting with carbon. But with this method, it is difficult to control the particle size. Using a ready-made matrix allows you to control the size of nanoparticles. However, this method uses high temperatures, and sometimes hydrogen, which complicates the production process. The main problem in the field of nanocomposites is the search for more technological, simple, cheap and environmentally friendly methods for obtaining nanocomposites with high performance characteristics. The developed technology for forming the pore space of the initial carbon matrix does not have the above disadvantages. This technology has a simple, cheap, environmentally friendly design. high temperatures are not used in the process of producing nanocomposites and third-party metal-carbon phases are not formed. The resulting nanocomposite materials were used as electrodes for ultra-high-volume capacitor structures. When studying the capacitance and electrical characteristics of samples, it was found that the formation of metal on a porous carbon matrix can significantly reduce the internal resistance of the cell and increase the specific energy consumption.

Aluminum — a metal whose scope of application is constantly expanding. At present, aluminum and its alloys in a number of areas successfully displace traditionally used metals and alloys. The widespread use of aluminum and its alloys is due to its properties, among which, first of all, low density, satisfactory corrosion resistance and electrical conductivity, ability to apply protective and decorative coatings should be mentioned. All this, combined with the large reserves of aluminum in the earth’s crust, makes the production and consumption of aluminum very promising. One of the promising areas for the use of aluminum is the electrical industry. Conductive aluminum alloys type E-AlMgSi (Aldrey) are representatives of this group of alloys.
One of the promising areas for the use of aluminum is the electrical industry. Conducting aluminum alloys of the E-AlMgSi type (Aldrey) are representatives of this group of alloys. The paper presents the results of a study of the temperature dependence of heat capacity, heat transfer coefficient, and thermodynamic functions of an aluminum alloy E-AlMgSi (Aldrey) with gallium. Research conducted in the “cooling” mode. It is shown that the temperature capacity and thermodynamic functions of the E-AlMgSi alloy (Aldrey) with gallium increase, while the Gibbs energy decreases. Gallium additives up
to 1 wt.% Reduce the heat capacity, enthalpy, and entropy of the initial alloy and increase the Gibbs energy.

The use of “warm liquid” tetramethylsilane (TMS) in ionization chambers for measuring dose profiles in water phantoms to prepare the accelerator for a proton therapy session is relevant. One of the promising areas of radiation therapy is proton therapy. To increase the conformality of proton therapy, it is important to know exactly the dose distributions from the energy release of the proton beam in the water phantom before conducting a proton therapy session. A television-type detector (TTD), which measures the profiles of the Bragg peak by the depth of the beam in the water phantom, helps to increase the accuracy of the dose distribution knowledge. To accurately determine the profile of the Bragg peak by the beam width in the water phantom, an additional method is proposed that will allow TTD to quickly determine the profile by the width of the Bragg peak in on-line mode. This prefix to the TTD will improve the quality of summing up the therapeutic beam-thanks to accurate knowledge of the profile by width, and therefore the formed high-dose distribution field will correspond to the irradiated volume in the patient and will increase the conformality of irradiation. The additional prefix to the TTD is designed on an organosilicon “warm liquid” and represents a high-precision ionization chamber with coordinate sensitivity along the width of the water phantom. The fully developed technology for obtaining “warm liquid” TMS allows creating both microdosimeters for proton therapy and detectors for measuring “dose profiles” in water phantoms during accelerator calibration. The considered prefix to the TTD detector - the calibrator meter of the dose field (KIDP) - can also be used independently of the TTD and with great accuracy measure the dose profiles of the Bragg peak in the water phantom, both in depth and width. KIDP can also be used to measure the outputs of secondary “instantaneous” neutrons and gamma quanta emitted from the water phantom orthogonally to the direction of the proton beam.