VOL 98, No. 4 (2025)

Using the sintering method near the softening temperature of the glass employed, glass-ceramic composites consisting of low-alkali aluminoborosilicate glass and barium titanate mixed in various proportions were successfully synthesized. The electrical properties of the samples were investigated in the microwave range. According to X-ray phase analysis, the synthesized samples are a mixture of barium titanate and an amorphous phase, as well as, under certain heat treatment conditions, products of glass crystallization (SiO2 – quartz and tridymite) and its interaction with the ferroelectric filler (Ba2TiSi2O8 – fresnoite). The dielectric permittivity level of the studied glass composite samples, measured at a frequency of 1 GHz, ranged from 9.2 to 25.0 with a dielectric loss tangent of 0.007…0.012.

Ceramics based on yttrium-aluminum garnet doped with ruthenium ions were synthesized. Ceramic samples were obtained by non-reactive sintering of nanocrystalline powders formed by chemical co-precipitation. The results indicated that the yttrium-aluminum garnet matrix can accommodate up to 0.5 аt. % of ruthenium cations without the formation of secondary phases or impurities. A slight deviation from the stoichiometry of the composition did not hinder the incorporation of ruthenium into the structure of the yttrium-aluminum garnet. Additionally, changes in the valence of the sintering additive did not influence the solubility of ruthenium ions in the ceramic material.

Phase and elemental analysis were performed for amorphous nanosized thin films of (InSe)20(GaSe)80 and (InSe)50(GaSe)50 compositions, and surface morphology studies were conducted. Optical transmission studies of thin films allowed us to establish that absorption corresponds to indirect allowed transitions for these compositions in accordance with the Tauc model, while the values of the optical band gap are Eg = 1.26 eV for (InSe)20(GaSe)80 and 1.07 eV for (InSe)50(GaSe)50 thin films.

The processes of powder production of CeO2 by reverse deposition are investigated. The CeO2 content in the resulting products is 99.2 % by weight. The main phase is cerium dioxide with a cubic lattice. The average particle size of the powder is ?42 microns, and the specific surface area is ?38.6 m2/g. A mass loss of 18 % occurs as a result of heating the material from 50 to 1200 °C. This mass loss is accompanied by endothermic effects with peaks on the DTA curve at temperatures of 144, 280 and 374 °C. The possibility of upgrading the properties of the resulting powder, in particular morphology, and determining the area of the most suitable application may become the topic of further research.

The paper presents the results of a study on the development of a primer-free enamel frit with increased chemical resistance to acids and alkalis, designed to protect steel pipelines. Zinc oxide was introduced into the composition of the frit, which helps to increase the resistance due to the higher chemical bond energy of the ion with oxygen compared with alkali metal ions. At the same time, the ZnO content is up to 10 wt. % reduces the frit's flow temperature. The experimental frit meets the standard requirements for spreading capacity (45 mm) and coefficient of thermal expansion (112?10–7 K–1). The introduction of zinc oxide in the amount of 5 wt. % in industrial borosilicate enamel leads to an increase in its chemical resistance by 4 times to acids and 8 times to alkalis compared to traditional industrial frit.

The paper investigates the possibility of thermal processing of waste from the chemical industry – phosphogypsum. It is shown that when phosphogypsum is dried, partial dehydration of dihydrous calcium sulfate occurs, and when calcined at temperatures of 600…1200 ?C, complete dehydration occurs. It was found that after heat treatment below 800 ?C, the samples actively absorb moisture. During the heat treatment of phosphogypsum in the presence of a reducing agent, two endothermic effects are observed associated with the sequential dehydration of CaSO4?2H2O, and a wide peak of the exothermic effect associated with the thermal destruction of the reducing agent and the formation of calcium sulfide from phosphogypsum. Phosphogypsum samples heat-treated in the presence of a reducing agent acquire the ability to emit a yellow-orange glow under the influence of ultraviolet radiation. Synthesized pigments can be used to produce water-based paints and varnishes.

The possibilities of obtaining fireclay crucibles for fire assay of ores with high quality indicators based on the highest-grade local raw materials of Uzbekistan – AKF-78 kaolin and fireclay obtained from this brand of kaolin were studied. In order to improve the physical and technical indicators of fireclay crucibles, pre-fired waste catalyst of the Shurtan Gas Chemical Complex (SGCC), containing 90.22 % Al2O3, was introduced into the composition of the masses. The optimal mass with a content of 8 % alumina waste withstands more than 11 – 13 melting without corrosion, and the heat resistance of the samples increases to 8 thermal cycles. At the same time, the amount of mullite formed after firing at 1420 ?C increases noticeably. The research promotes the use of local materials and recycling of industrial waste, which is environmentally friendly. This aligns with the goals of sustainable development by reducing waste and utilizing resources efficiently.