VOL 99, No. 9 (2026)

The present study investigates the physicochemical and biological characteristics of 45S5 bioglass under conditions of its interaction with a buffer solution simulating a biological environment. The primary focus was placed on examining biodegradation and the dynamics of acid-base balance changes in the model medium. It has been confirmed that the effectiveness of the material for biomedical applications is determined by the particle size employed. The study addresses the problem of accurate fractionation and provides a comparative analysis of two sample preparation methods: wet and dry sieving. It was established that wet sieving promotes the removal of fine fragments from the surface of larger fractions and reduces the material's influence on local alkalinization of the medium. Using Ehrlich ascites adenocarcinoma cells, it was demonstrated that the cytotoxic effect is attributable to chemical necrosis induced by the alkaline environment localized at the surface of the bioglass particles. It is concluded that the material holds potential for application in the field of adjuvant therapy for malignant neoplasms. The findings obtained are of significant importance for the development of novel biomedical implants and therapeutic systems.

Calcium-copper titanate (CaCu3Ti4O12/CСTO) is a highly demanded material for its colossal dielectric constant and temperature stability. CСTO has many applications as sensors, microwave absorbers, etc. However, ceramic capacitors are one of the most promising applications, but CСTO has a high loss tangent (usually tg? > 0.1 for pure CСTO). Therefore, many attempts have been aimed at reducing tg? while maintaining ?r > 10,000. This problem was solved by doping and alloying, which makes the CСTO ceramics production more difficult and expensive. In this paper, for the first time, an approach to reducing the tg? while maintaining a high ?r is demonstrated by solid-phase synthesis temperature reducing and optimizing the grinding and calcinating processes. The materials were examined using XRD analysis, the ceramics microstructure evolution was revealed using SEM; the relative density was estimated by Archimedes method. The ?r and tg? were determined by the capacitive method at 1 kHz, 100 kHz and 1 MHz. For the first time, pure CСTO ceramics with ?r = 10,821 and tg? = 0.051 at 1 kHz were obtained. The presented manufacturing approach contributes to adjustable dielectric properties of CCTO ceramics.

The effect of silicon carbide on the microstructure, phase composition, and mechanical properties of Al2O3–ZrB2 composites was investigated. It was found that in the binary Al2O3–ZrB2 composite, the aluminum borate phase Al18B4O33 (6 vol. %) forms during sintering, hindering densification. Porosity reaches 8 %, mass loss – 24 %, flexural strength – 300 MPa, fracture toughness – 4.2 MPa·m1/2. The introduction of SiC prevents aluminum borate formation due to the reaction with surface B2O3, leading to the formation of refractory SiO2 and aluminoborosilicate liquid phase. The three-component Al2O3–ZrB2–SiC composite achieves density ?98 % of theoretical, strength 450 MPa, hardness 19.1 GPa, and fracture toughness 5.5 MPa·m1/2. Crack branching on SiC and ZrB2 grains increases fracture toughness.

Previously unknown in the literature, complexes of hexamethylenetetramine (HMTA) with tungsten silicates of the composition Rb5[SiW11O39Fe(HMTA)]?20H2O, Cs5[SiW11O39Fe(HMTA)]?6H2O, Rb6[SiW11O39Zn(HMTA)]?12H2O, Cs6[SiW11O39Zn(HMTA)]?10H2O with the Keggin anion structure were synthesized and studied by electron and IR spectroscopy, nuclear magnetic resonance, thermal and X-ray phase analysis. The electronic absorption spectra of the HMTA complexes with tungsten silicatoferrates in the region of 270…600 nm indicate an octahedral environment of iron (III) atoms, and the shift of the absorption maximum of 290 nm for Rb5[SiW11O39Fe(H2O)]?10H2O to 310 nm for Rb5[SiW11O39Fe(HMTA)] indicates a change in the ligands in the immediate environment of iron atoms and the formation of HMTA complexes with tungsten silicate. This is also evidenced by the results of nuclear magnetic resonance of solutions of the synthesized zinc-containing compounds in D2O: the chemical shift of the 1H protons of the CH2 methylene groups in HMTA is 4.56 ppm, in the Rb6[SiW11O39Zn(HMTA)]?12H2O complex – 4.64 ppm; for the 13C carbon atoms in HMTA, the chemical shift is 71.1 ppm, and in the Rb6[SiW11O39Zn(HMTA)]?12H2O complex – 71.2 ppm. According to thermal analysis (TA), differential scanning calorimetry (DSC) and X-ray phase analysis, the products of thermolysis of the synthesized compounds at 650? are phases with the structure of pyrochlore and hexagonal tungsten bronzes. The catalytic properties of Rb5[SiW11O39Fe(HMTA)]?20H2O were studied in the production of carbon nanomaterials. A hybrid carbon-mineral material, nanocarbon (WOX), was obtained. It was characterized by X-ray diffraction analysis and electron microscopy. It exhibits high electrical conductivity and chemical resistance to concentrated acid solutions. The results of this study may be useful for the low-temperature synthesis of compounds with a pyrochlore structure, hexagonal tungsten bronze, and hybrid carbon-mineral nanostructures.

The study compares two types of coatings based on an alumina phosphate binder with a cobalt-containing spinel pigment: one without wollastonite and one with its addition. The coating without wollastonite exhibits a color change from blue to lilac due to the destruction of the CoAl2O4 spinel and the formation of cobalt pyrophosphate (Co2P2O7). Surface integrity damage is observed after heat treatment at 280…300 °C. X-ray diffraction (DRON-07 diffractometer) and IR spectroscopy (FT-801 Fourier spectrometer) analyses revealed that the introduction of wollastonite into the coating composition stabilizes the spinel, preserves the blue color, and maintains the acicular (needle-like) structure of wollastonite. Along with the phases of berlinite (AlPO4), wollastonite (CaSiO3), and brushite (CaHPO4·2H2O), the presence of an amorphous alumino-silico-phosphate polymer coating with a homogeneous structure was determined. The obtained composition is recommended for decorative protection of ceramics and concrete.

The electrical properties of the complex oxide Bi2Сu0.25Ni0.75Ta2O9 with a pyrochlore structure (space group Fd-3m, 10.5200(5) ?), synthesized by the solid-phase method, were studied using impedance spectroscopy. The porous microstructure of the ceramic is formed by partially fused, rounded ceramic grains with longitudinal dimensions of 1…2 ?m. Impedance plots were analyzed, and electrical circuits describing the sample's behavior with increasing temperature were modeled. The activation energy for the sample's conductivity is virtually independent of temperature and is 0.466(5) eV, typical of semiconductors. No dielectric relaxation was observed for the sample. A bipolar conductivity model was proposed to describe the sample's electrical behavior.

One of the main disadvantages of sulfur concrete is the formation of a crack defect when cooled in metal molds. The proposed way of using sequential addition of components, temperature control at the entire mixing stage of the mixture is based on previous studies, which showed that the main factors determining the compressive strength of samples are both sulfur itself and its interaction with fine filler, as well as its strength properties. The work is devoted to determining the influence of technological factors and methods of preparing mineral components on the strength of sulfur-concrete samples. To prepare sulfur-concrete samples, ground industrial sulfur produced by Kaspiigaz LLC, natural zeolite of the Kempendyaysky field, and crushing waste from carbonate rocks of the Sasaabytsky field were used. For experimental studies, compositions were prepared with the following content: ground sulphur 30 wt. %, filled with fine zeolite powder in amount of 5 wt. % and limestone crushed stone screening – 65 wt. %, using three methods of preparing mineral components. For mixing, a developed forced mixer was used, which provided an upper load of raw materials and unloading of the finished sulfur-concrete mixture. The determination of the compressive strength of sulfur-concrete samples was carried out on an IP-1A-1000 test machine, structural studies of samples were carried out on a JEOL JSM-6480LV high-resolution scanning electron microscope. A scheme of a mixing installation is proposed, which made it possible to optimize the multivariable stages of preparing a mixture for making sulfur-concrete samples due to the special shape of the blades and their location on the rotating shaft, as well as uniform heating of the mixture, high-quality mixing of ingredients is ensured to obtain a homogeneous technological mixture, the properties of which are the same in any individual volume. A method has been selected that makes it possible to produce sulfur-concrete samples without defects and increase the compressive strength by 17 %.