VOL 98, No. 1 (2025)

The paper presents the results of the studies of a matrix based on borophosphate glass (BFS) with the addition of lithium chloride as a simulator of spent electrolyte, a type of radioactive waste formed during the pyrochemical processing of spent nuclear fuel. Based on the results of X-ray phase analysis and scanning electron microscopy, the phase composition and microstructure of the glasses were evaluated – the amorphous structure and homogeneity of the obtained material were confirmed. Using differential scanning calorimetry and thermal conductivity measurements, the thermophysical properties of the material are described, and it is shown that the inclusion of LiCl does not affect the glass transition temperature for the obtained glasses which equals ~410 ?C. However, the addition of lithium chloride affects the electrical conductivity properties studied by electrochemical impedance spectroscopy. Tests of mechanical strength and hydrolytic stability were carried out in accordance with the established requirements for the matrices for immobilization of radioactive waste. When studying the morphology of the glass surface in contact with water, the formation of a diffusion layer is observed as a result of the transition of sodium ions into a solution. The performed studies confirm the possibility of using glasses of the selected composition as a matrix for immobilization of the spent electrolyte based on lithium chloride.

The precursor powder and luminescent ceramics YAG:Ce based on it were obtained by reverse chemical deposition. The influence of sintering additives (CaO, MgO and TEOS), the concentration of the activator Ce3+, the temperature of vacuum sintering, as well as the temperature of air annealing on the luminescent properties of YAG:Ce ceramics has been studied. The following parameters have been identified as optimal parameters for the manufacture of YAG:Ce ceramics in terms of luminescence efficiency. The concentration of the sintering additive is 0.01 f.u., the type of sintering additive is TEOS, the vacuum sintering temperature is 1800 ?C, the air annealing temperature is 600 ?C for samples with TEOS. A sample with a luminescence efficiency of 319 Lm/W was obtained when exposed to 190 mW laser radiation with a spot diameter of ~5 mm.

The results of a study of dielectric properties and harmonic coefficient for barium titanate ceramics obtained from a mixture of BaTiO3 powders with particle sizes of 400 and 50 nm at different sintering temperatures are presented. It is shown that when the content of the finely dispersed component changes from 0 to 100 %, the dielectric constant ?(x) and the harmonic coefficient ?(x) are non-monotonic, reaching a maximum at x equal to 0.25 and 0.30. This dependence may be due to a change in packing density when the percentage composition of the components changes.

For the first time a series of ceramic powders of the composition (Y1–xLux)3Yb0.15Er0.03Al5O12 (YLuAG) with a garnet structure in which the atomic ratio of Y3+/Lu3+ cations varied from 80/20 to 20/80, were synthesized using the chemical coprecipitation method. It was determined that the process of garnet phase formation under the synthesis conditions used occurs through the formation of intermediate phases, the composition of which depends on the Y/Lu ratio in the solution of the initial salts. Based on the results of differential thermal analysis of precursor powders and X–ray diffraction of ceramic powders of the composition (Y1–xLux)3Yb0.15Er0.03Al5O12, calcined at 800, 900, 1000 and 1150 ?C, the temperature ranges of formation and decomposition of intermediate crystalline phases Y2O2SO4, Y2(SO4)3, Lu2(SO4)3 and Lu1–xYxAlO3, formed in the process of temperature synthesis of the phase with the garnet structure, were determined.

The article presents the results of determining the anti-filtration and sorption capacity of palygorskite and other clays of the Borshchevsky and Voskresensky cement raw material deposits, which are overburden rocks from mining operations. It was experimentally established that the filtration coefficients of the studied samples correspond to the current standard value, which allows their use in the technology of anti-filtration screens for solid municipal waste landfills. For the palygorskite clay sample, the filtration coefficient is 8?10-10 m/s. The values of the main sorption characteristics for the palygorskite clay sample were determined: specific surface area – 85,1 m2/g, specific volumes of micro- and mesopores, respectively – 0,0138 and 0,127 cm3/g. The values of static sorption capacity for heavy metals from an aqueous solution with a purification efficiency of > 94 % were obtained; the purification efficiency from oil products was > 60 %.

The peculiarities of obtaining porous materials based on different types of ash and slag materials (fly ash, boiler slag, ash-slag mixture) by the “self-foaming” technology using Na2B4O7 flux were studied. Changes in the internal structure and density of samples depending on the foaming temperature and flux content were considered. It was shown that samples based on boiler slag have the most uniform structure. The patterns of the influence of phase composition on the intensity of sintering and foaming were described, consisting in increased activity of interaction of glass phase components and simplification of softening of the aluminosilicate mass.

An overview of the research results on the laser modification of coatings sprayed by HVOF is presented. The review includes information on laser post-treatment of mainly on tungsten carbide-based coatings. Information on the main types of laser machines used for additional thermal treatment of coatings is provided. It was established that laser post-treatment has a significant effect on the microstructure of coatings, provides a higher density, reduces dispersion and porosity by 4 – 6 times, and allows you to adjust the distribution and value of residual stresses. It is shown that with the help of laser post-treatment, it is possible to increase the microhardness of coatings by 20…50 %, to increase the adhesive strength of the coating and the metal base, wear resistance and corrosion resistance, and to reduce the coefficient of friction by 20…65 %. The reasons responsible for the observed changes in the structural and strength characteristics of coatings after laser post-treatment with remelting are indicated.