PhC-2024

T.I. Chupakhina, A.M. Uporova, O.I. Gyrdashova, L.Yu. Buldakova, Y.A. Deeva, I.V. Baklanova, M.Yu. Yanchenko
Institute of Solid State Chemistry of the Ural Branch of RAS

Abstract: Solid of Sr₂Ti_1-xMn_xO₄ (x = 0; 0.01; 0.025; 0.05; 0.1) solutions with Raddlesden-Popper structure (A_n+1B_nO3_n+1, n = 1, structural type K₂NiF₄) were obtained by a precursor technology. Formate complexes of the corresponding metals synthesized by an original method were used as precursors. The products of thermolysis of the obtained complexes with an organic ligand are isostructural single-phase samples, which crystallize as agglomerates with an average size of 1 μm. Using energy dispersive X-ray analysis, we established a uniform distribution in the agglomerates of Sr²⁺, Ti⁴⁺ and Mn⁴⁺. According to electron spin resonance and optical spectroscopy, manganese in titanium-oxygen polyhedra of Sr₂Ti_1-xMn_xO₄ is predominantly in oxidation degree 4⁺. Increasing the concentration of manganese in the solid solution composition effectively narrows the forbidden band width of strontium titanate from 3.5 eV to 2.5 eV for Sr₂Ti_0,9Mn_0,1O₄. The catalytic properties Sr₂Ti_1-xMn_xO₄ were analyzed in the oxidation reaction of hydroquinone under irradiation of its aqueous solutions in the ultraviolet and visible spectral ranges. Under the described conditions, all photocatalysts showed a high rate of photooxidation. It was found that the photocatalytic activity of Sr₂Ti_1-xMn_xO₄ in 3 consecutive cycles of photooxidation under infrared stimulation exceeds the commercial catalyst Degussa P25 by 4 times.
Keywords: layered wide-gap semiconductors. perovskite, strontium titanate, formate synthesis, photocatalysis, voltammetry. electron microscopy. electron microscopy

A.G. Shirokova¹, S.A. Bibanaeva¹, E.A. Bogdanova^1,2, V.M. Skachkov¹, O.V. Koryakova^3
1 Institute of Solid State Chemistry of the Ural Branch of RAS
² JSC Giredmet
³ I.Ya. Postovsky Institute of Organic Synthesis of the Ural Branch of RAS

Abstract: In this article, the features of synthesis and physicochemical properties of a composite material based on precipitated hydroxyapatite and synthetic aluminosilicate zeolites are investigated. Using modern methods of analysis, both the obtained composite material and individual components included in its composition are certified. The material was synthesized by mixing with simultaneous grinding in a vibration mill of synthetic zeolite and hydroxyapatite, followed by annealing of the resulting mixture. The characteristics of the initial aluminosilicate zeolites and hydroxyapatite were clarified by infared spectroscopy, their interaction during mechanochemical synthesis and subsequent heat treatment of composites obtained on their basis was assessed. X-ray phase analysis of the initial synthetic zeolites indicates the loss of adsorbed and crystallization water and decomposition to complex aluminosilicate oxides of calcium and sodium during heat treatment at 1000 °C. It was also found that although precipitated hydroxyapatite is structurally unstable and its phase composition depends on temperature, the behavior of the composite material obtained on its basis differs significantly during high-temperature treatment. It was proven that thermal annealing of the composite obtained by mechanosynthesis during heat treatment at 1000 °C does not lead to chemical modification of the hydroxyapatite structure and the formation of a new compound due to the introduction of zeolite. Differential thermal analysis showed an increase in the stability of the composite material relative to its individual components. The morphology of the original materials and those subjected to heat treatment was studied using scanning electron microscopy; a change in morphology during sintering was shown. Along with the study of the thermal stability of the materials, an assessment of the linear shrinkage of the samples and their microhardness was carried out. The conducted comprehensive studies made it possible to recommend composites based on precipitated hydroxyapatite, containing 15 wt.% aluminosilicate zeolites in their composition, as promising materials for further study, possessing the best functional characteristics, including strength.
Keywords: synthetic zeolite, hydroxyapatite, infrared spectroscopy, X-ray phase analysis, differential thermal analysis, composite material

Z.V. Shomakhov¹, S.S. Nalimova², O.D. Zyryanova², V.M. Kondratev^3,4, Z.Kh. Kalazhokov¹, C.D. Bui², V.A. Moshnikov^2
1 Kabardino-Balkarian State University named after H.M. Berbekov
² Saint Petersburg Electrotechnical University «LETI»
³ Moscow Institute of Physics and Technology
⁴ Alferov University

Abstract: Currently, semiconductor gas sensors are of interest for various applications, including industry, medicine and environmental monitoring. One of the most important tasks in the sensor technology is to reduce the operating temperature of devices. In this paper, it is proposed to use WO_x/WS₂ nanostructures obtained by a hydrothermal method to solve this problem. The morphology, structure, and composition of the developed nanostructures were studied using scanning electron microscopy, reflected electron diffraction and X-ray photoelectron spectroscopy. It is shown that the nanostructures are formed by 1D and 2D nanoobjects with an average length of 200 nm and are nanocomposites consisting of tungsten oxide WO_x and tungsten disulfide WS₂. The study of sensory properties when exposed to isopropanol, ethanol and acetone vapors at room temperature was carried out. A reversible change in resistance is demonstrated when these gases appear in the atmosphere. Additionally, exposure to ultraviolet radiation during the measurement process leads to an increase in the response value and speed of the sensor layers in the case of interaction with isopropanol and ethanol vapors.
Keywords: gas sensors, room temperature, nanostructures, tungsten oxide, tungsten disulfide, nanocomposites

N.A. Shostak
Kuban State Technological University

Abstract: This article describes the features of determining the enthalpy characteristics of the hydrate formation process. Aspects of forming hydrate structures from hydrate-forming agent molecules and water are described. It is shown that the processes of the hydrate formation and dissociation have different natures, which are determined by the interaction of the hydrate former with water in one phase state or another: hydrate former – solid phase of water – ice, hydrate former – liquid phase of water, hydrate former in a critical (pseudocritical) state – liquid phase of water. The dependence of the water crystallization temperature on the pressure and nature of the hydrate former is analyzed. The energy processes occurring during the formation of clusters and unit cells of the crystal lattices of hydrate structures due to the release and absorption of the thermal energy are described. Dependences are proposed for calculating the heat of formation of the crystal lattice from ice-like associates of water molecules. It is shown that the process of restructuring the ice lattice into a hydrate lattice can be both exothermic and endothermic.
Keywords: cluster, crystal lattice, hydrate generator, hydrate formation, hydrate structure, ice-like associates, heat of formation

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A.S. Antonov¹, N.Yu. Sdobnyakov¹, V.A. Anofriev¹, M.S. Afanasiev^2,3, E.M. Semenova¹, V.V. Makaev^1
1 Tver State University
² MIREA – Russian Technological University
³ Fryazino Branch of V.A. Kotelnikov Institute of Radio Engineering and Electronics of RAS

Abstract: Nanoscale iron films of different thicknesses and at different spatial scales were studied using two alternative methods: atomic force microscopy and scanning tunneling microscopy. It was revealed that the surface morphology and fractal dimension depend not only on the film thickness but also on the deposition conditions and subsequent digital processing. It was concluded that the surface has a highly developed relief, which corresponds to high values of the fractal dimension. A hypothesis was put forward that the presence of iron oxides on the surface of the studied samples significantly affects their morphology, contributing to the formation of a complex and highly developed relief. These oxides lead to the formation of some structural inhomogeneities, which lead to the observation of agglomerates in a fairly wide range of fractal dimension values (from 2,49 to 2,94) on the film surface, i.e. oxides contribute to the aggregation of particles, creating a more complex surface structure. In addition, a method of separating agglomerates allowed us to record an increase in the value of the fractal dimension, which indicates the efficiency of separating and studying individual complex surface objects. Thus, for nanosized iron films, it becomes important to take into account the effects of oxidation and agglomeration of surface elements when analyzing them and choosing a method for obtaining them to identify structures with a certain value of the fractal dimension.
Keywords: atomic force microscopy, scanning tunneling microscopy, magnetron sputtering, fractal dimension, iron films