Sergey Anatolievich Ghyngazov

Ceramic synthesis is the most important stage of ceramic production. Reducing its energy consumption and time costs is the goal of many studies. As an alternative to traditional solid-phase synthesis, synthesis in a powerful beam of fast electrons is considered. Mixtures of Al₂O₃ + TiO₂ oxides with and without the addition of ZrO₂ were heated in air by electrons with an energy of 1.4–2.5 MeV at a power density of up to 25 kW/cm² and higher at a movement speed of the cuvette with the powder mixture of oxides in the irradiation plane from 0.25 to 1 cm/s. The mixture melted during irradiation and the synthesis of complex titanates in the form of ceramic drops with a porous structure took place. It was found that porosity is regulated by irradiation parameters and cuvette movement speed. The synthesized ceramics have an oxygen deficiency and a characteristic gray-blue color. Annealing in air is accompanied by oxidation of the ceramics and transformation of this color into white. This occurs due to a change in the valence of a small part of Ti included in the ceramics from Ti³⁺ to Ti⁴⁺ as a result of oxidation. The thermal expansion curve shows hysteresis, indicating phase transformations due to oxidation. After thermal annealing in the atmosphere, the hysteresis disappears. Electron beam processing of the Al₂O₃ + TiO₂ mixture with the addition of ZrO₂ led to the synthesis of glass ceramics of a complex composition containing zirconolite. Zirconolite is currently the most promising material for the immobilization of radioactive materials. The main reason for the complication of the glass ceramics composition was the presence of uncontrolled impurities in the original mixture, in particular Ca. The hardness of the ceramics, depending on the porosity and synthesis conditions, can vary from 1.5 to 10.5 GPa.

High-entropy ceramics intended for thermal barrier coatings are developed to improve their performance properties, particularly by increasing their operating temperature. However, conventional synthesis of high-entropy ceramics is time-consuming. This study explores a nonconventional approach to reducing synthesis time by processing ceramic materials with a high-power beam of high-energy electrons (fast electrons). A powder mixture of the initial reactants Y ₂ O ₃ , Yb ₂ O ₃ , Lu ₂ O ₃ , Eu ₂ O ₃ , Er ₂ O ₃ , and Al ₂ O ₃ was heated in air using 1.4 MeV electrons at different electron-beam currents. The cuvette containing the powder mixture was moved beneath the beam at 1 cm/s, while the beam was scanned across the width of the internal volume of the cuvette. The total irradiation time was 10 s. At beam currents of 4 mA or higher, melt droplets formed within the irradiated powder mass, and their proportion relative to the unmelted powder increased with increasing current. Crystallization occured in the melt droplets during cooling. The resulted droplet-shaped ceramic product was highly porous because of the intense release of adsorbed gases from the melt. SEM images and EDS elemental maps relealed a uniform distribution of the constituent elements throughout the droplet-shaped ceramic product. XRD analysis identified the synthesized material as high-entropy (Y _0.2 Yb _0.2 Lu _0.2 Eu _0.2 Er _0.2 ) ₃ Al ₅ O ₁₂ ceramic. The powder that did not contribute to the formation of the droplet-shaped product was an intermediate product containing Er ₃ Al ₅ O ₁₂ and Y ₃ Al ₅ O ₁₂ garnets, together with Er ₂ O ₃ , Yb ₂ O ₃ , Y ₂ O ₃ , Eu ₂ O ₃ , Lu ₂ O ₃ , Al ₂ O ₃ oxides.

The development of thermoelectric materials has attracted considerable attention with the emergence of a new class of high-entropy materials. Their fabrication is typically based on solid-state synthesis and involves prolonged mechanical mixing of powder precursors, high-temperature heat treatment, and multiple repetitions of these operations. The paper addresses the issues of accelerating the manufacturing process of highly en tropic ceramics for thermoelectric applications through the use of electron beam processing. The effect of cy clic processing of a powder mixture of initial reagents in air with a high-energy electron beam (E = 1.4 MeV) on the sintering of compacts was studied using high-entropy perovskite ceramics (Ca0.2Sr0.2Ba0.2Pb0.2La0.2)TiO3 as an example. The electron beam current was 4 mA (5 treatment cycles) and 5 mA (4 treatment cycles), with mechanical grinding of the powder after each irradiation step. It was found that electron beam treatment enhances the compaction/sintering kinetics. The efficiency of the treatment in creases with the number of cycles. As a result, the sintering process is accelerated, leading to increased ce ramic density and mechanical strength. These improvements are attributed to the formation of the high entropy phase (Ca0.2Sr0.2Ba0.2Pb0.2La0.2)TiO3 in the powder mixture as a result of electron beam processing.

The influence of the low-melting additive bismuth oxide on the consolidation processes of partially stabilized zirconium dioxide nanoparticles in compacts obtained under compacting pressures was studied: 1, 50, and 800 kg/cm². It is shown that, at a compacting pressure of ≤50 kg/cm², the density of the compacts is comparable in magnitude to the bulk density. It has been established that the introduction of a low-melting additive facilitates the production of ceramics from compacts of low density obtained at pressures from 1 to 50 kg/cm². At compacting pressure ≥50 kg/cm², the presence of the additive helps to obtain ceramics with a density of ≥5.8 g/cm³. During sintering, the concentration area of the additive is located in the intergranular boundaries. The presence of additives in ceramics, due to phase transformations with temperature changes, leads to crack formation mainly along grain boundaries. For low compacting pressures, a decrease in porosity and an increase in density and average grain size are observed as the compacting pressure and the content of the low-melting oxide additive increase. The research results are of great importance for the development of new ceramic 3D printing technologies.

In this work, models of the deformation behavior of polymer films of polyethylene and polyvinyl chloride are developed and analyzed, taking into account the influence of thickness, mechanical stress, temperature, time and dose of electron and ion irradiation. Experimental studies included tensile tests of polyethylene films of different thicknesses irradiated with krypton ions and electrons, as well as measuring the return deformation and its rate. It is shown that the quadratic and exponential models best describe the dependences of deformation on stress. Analytical formulas for the rate and acceleration of deformation are obtained, taking into account the influence of temperature and radiation dose. The results demonstrate a significant increase in the elastic properties and return deformation of irradiated samples, which is explained by the cross-linking of macromolecules and changes in the molecular structure under the influence of radiation. The proposed models and formulas can be effectively used in the development of devices and systems for monitoring the deformation of polymeric materials under radiation exposure in the aerospace, nuclear and electronic industries. Using the statistical analysis method, it was shown that the exponential model describes the dynamics of polyethylene deformation with a determination coefficient R² = 0.985, which significantly exceeds the accuracy of the linear model (R² = 0.85).

The properties of ceramics obtained by sintering of compacts from ultrafine and microfine aluminum oxide powders in a constant magnetic field were studied. Aluminum oxide activation sintering in a constant magnetic field makes it possible to reduce the sintering temperature of ceramics while simultaneously improving its quality. It was found that the effect of the magnetic field is most pronounced when sintering compacts from micropowders. It was determined that the density, microhardness, and tensile strength significantly exceed the corresponding values established for ceramics obtained by sintering of compacts of ultrafine aluminum oxide in a magnetic field.

The aim of this study was to investigate the effect of dose, temperature and mechanical stress on the return and rate of return deformation. The structure of the polymers under study begins to change under the influence of electron and ion beams, as well as temperature and mechanical stress, which leads to a change in such mechanical properties as return deformation and rate of return deformation. The authors proposed formulas for models that accurately explain the experimental data. In addition, using an optical microscope DM 6000M (Leica, Wetzlar, Germany), photographs of the surface morphology of unirradiated and irradiated materials before and after tensile testing were obtained. The results can be used to improve the properties of packaging materials in the food industry.