Possessing a high complex of mechanical and functional properties: tensile strength, hardness, wear resistance, corrosion resistance, heat resistance and bio-inertness, Al2O3–ZrO2 systems are an effective material used for the manufacture of products that operate in harsh conditions. The main problem with currently used production methods is the limitations caused by the aggregability of particles. One of the approaches to reducing the degree of their aggregation is the use of organic or mixed aqueous-organic media. At the same time, the question of the influence of the solvent on the phase composition and structure of the forming precursor of the oxide system remains open. In this regard, the aim of the work is to identify patterns of influence of the solvent composition and electrolysis conditions on the chemical and phase composition of the final product and some of its physicochemical characteristics. The synthesis of precursors of oxide systems was carried out using a diaphragm-free coaxial electrolyzer reactor, where the cathode is Kh18N10T steel, and the soluble anode is 99.95
A 40Bi2O3–30Li2O–15B2O3–7CuO–5TeO2–3MoO3 glass was synthesized by melt-quenching at 1200°C to investigate its structural, thermal, dielectric, and basic physical properties as a Bi2O3-rich oxide glass with potential relevance to thermoelectric research. Density and molar volume determined by Archimedes’ method were 4.63 g cm–3 and 48.28 cm3 mol–1, respectively, indicating a relatively compact glass network influenced by heavy metal oxides. X-ray diffraction confirmed the amorphous nature of the sample. Fourier-transform infrared spectra revealed vibrations associated with BO3 and BO4 units and borate-related species (including metaborate- and pyroborate-type units), consistent with a borate-based network modified by Bi2O3, CuO, and TeO2; however, boroxol rings cannot be assigned unambiguously from the present spectra. Differential scanning calorimetry conducted between room temperature and 650°C showed a glass transition near 420°C and no strong crystallization peak in this range, indicating good thermal stability at moderate temperatures. The dielectric response, measured between 100 Hz and 1 MHz, exhibited high capacitance and permittivity at low frequencies, followed by a marked decrease with increasing frequency, which can be attributed to the progressive freezing of ionic and interfacial polarization and is consistent with Maxwell-Wagner type behaviour. These results provide baseline information on the structure, thermal behaviour, and dielectric properties of this Bi2O3-rich glass composition and indicate that further work, including direct measurements of electrical resistivity, Seebeck coefficient, and thermal conductivity, is required before its thermoelectric performance can be fully assessed.
The samarium-doped ceria Sm0.2Ce0.8O2 – ⸹ electrolyte was synthesized by the co-precipitation method. XRD analysis confirmed the phase structure of the prepared electrolyte, which exhibited a cubic structure, with crystallite size varying from 22‒34 nm. SEM micrographs indicate homogenous, closely packed spherical grains and a relatively dense structure. Raman and UV–visible spectroscopy were used to observe molecular vibration and absorption. The electrolyte powder sintered at 1000°C showed a maximum ionic conductivity of 0.11 S cm–1 at 600°C in air.
The combined effect of fluoride (F–) and titanium (Ti4+) ions on the formation of hydrosilicate nanotubes under hydrothermal conditions. It was found that titanium ions can be incorporated into the crystalline structure of hydrosilicates and occupy positions within the nanotube channels. It was revealed that the temperature and the ratio of reagents in the hydrothermal fluid significantly affect the phase composition of the synthesis products, determining the phase ratio of hydrosilicates and titanium-containing components.
This paper presents the results of a study on the controlled formation and comprehensive diagnostics of hybrid halide perovskite films for use in solar energy. The main focus is on the development of a technological approach that allows for targeted control of the morphology of the active layer at the synthesis stage. Films of the composition CH3NH3PbI3 (MAPbI3) modified with monoethanolammonium lead iodide (HOC2H4NH3PbI3, MEAPbI3) additives were obtained by centrifugation from dimethylformamide (DMF)-based solutions). It was shown that the electrophysical characteristics, correlating with the experimental values of the fractal dimension, change with changing the concentration of additives and effects on the fractal dimension. Varying the additive concentration of the (0–70
This study investigates the elastic, mechanical, and radiation shielding properties of tungsten–sodium–zinc–borate (B2O3–WO3–Na2O–ZnO) glasses containing α-Fe2O3 nanoparticles. Elastic and mechanical parameters were evaluated using the Makishima–Mackenzie model to assess the influence of α‑Fe2O3 content on the glass system. The calculated bulk modulus reached 203.76 GPa at 1 mol
Powdered aluminosilicate materials were synthesized directly from metakaolin by the dispersant template (DT) method to address the difficulty of grinding monolithic geopolymers for adsorption applications. The resulting powder was subjected to nitric acid treatment at various concentrations to examine the effects on composition, structure, texture, and acetone vapor adsorption. Comprehensive characterization indicated that the DT-derived parent material consisted of partially geopolymerized aluminosilicate together with residual metakaolin, and that acid treatment induced dealumination and partial breakdown of the aluminosilicate framework, leading to silica-rich structures. Nitrogen adsorption–desorption measurements showed that the specific surface area increased markedly with acid concentration, reaching the highest value for the sample treated with 5 mol L–1 nitric acid, which exhibited a surface area more than four times that of the untreated material. Acetone adsorption experiments demonstrated that the 5 mol L–1 nitric acid-treated sample adsorbed 16.0 µmol/g within 30 min and reached 26.2 µmol/g after 3 h, approximately 1.5 times greater than the untreated sample. The enhanced performance is attributed to the increased surface area and the development of a more favorable pore structure in the acid-treated, silica-rich aluminosilicate framework.
Sol-gel synthesis of (1 ‒ x)(Hf(OH)4–H2SiO3)‒xZrO(OH)2 precursor powders was performed. Ceramic composites (1 ‒ x)HfSiO4‒xZrO2 were obtained by sintering the precursor powders in the temperature range of 1000‒1300°C. Thermal behavior of the precursor powders was studied using the DSC/TG. X‑ray diffraction showed that the addition of ZrO2 stabilizes hafnium silicate, preventing its decomposition in the composites. It was found that sintering of (1 ‒ x)HfSiO4–xZrO2 compositions at 1300°C leads to partial decomposition of hafnium silicate with the formation of HfO2 and SiO2; at this temperature the composites are a mixture of hafnium silicate, monoclinic solid solutions of HfxZr1 – xO2, and SiO2. The Vickers microhardness values and thermal conductivity values in the temperature range from room temperature to 250°C were determined; SEM images of the fracture surface of ceramic samples before and after leaching were presented. The chemical resistance of ceramic composites as matrices for radionuclides was assessed using the leaching method. All characteristics of the compositions were obtained for the first time.
The paper presents a comparative study of ZnO, ZnO:Cu, and ZnO:Al films obtained by the sol–gel method. The concentration of dopants in all cases was 6 at
The development of white-light phosphors via Eu3+/Tb3+/Tm3+ co-doping remains challenging due to imbalanced energy transfer and site-selective incorporation. In this work, we investigate the luminescent properties of BaBi1.70 − xEuxTb0.15Tm0.15B2O7 (x = 0.05, 0.10, 0.15) solid solutions synthesized by solid-state reaction. Powder XRD confirms homogeneity of phosphors and a monotonic decrease of unit cell parameters, consistent with Bi3+ → Eu3+ substitution. Based on experimental data, the miscibility limit for the triple-doped system is estimated at x = 0.475, which is higher than that for single-doped BaBi2 − xEuxB2O7 (x = 0.45), indicating an expansion of the isomorphic miscibility range upon co-doping. Under 295 nm excitation, luminescence is dominated by intense red emission from Eu3+ (614 nm), while green (Tb3+) and blue (Tm3+) components are virtually absent. Excitation spectra at 614 nm show no features attributable to Tb3+ or Tm3+, and CIE coordinates remain in the red region (x ≈ 0.647, y ≈ 0.345). Although white emission was not achieved, this study provides some insights into the role of crystallographic site preference and compositional deformations in multi-ion-doped phosphor design which is essential for rational development of efficient UV-convertible white-light materials.
The graphitization of diamond single crystals with a grain size of 200–250 µm was studied when heated to 1000–1300°C. During the production of diamond–SiC composites by vacuum siliconization of a porous diamond matrix, not only the surface graphitization of diamond grains, but also the graphitization of the diamond at internal defects occurs. A decrease in the average strength of a single grain of diamond crystals as a result of their heat treatment both in an inert medium and during vacuum siliconization was demonstrated. It was found that siliconizing at a furnace temperature of 1550°C, despite the short process time, leads to a significant (40
Bismuth titanate Bi4Ti3O12 with crystallite sizes of 20–30 nm was synthesized by heat treatment of a coprecipitated mixture of hydroxides at a temperature of 450°C and prolonged isothermal holding. The thermal behavior and dielectric properties of the material are discussed in this paper. For the first time, data on the thermal conductivity of a Bi4Ti3O12-based nanoceramic material are presented.
Highly dispersed powders based on the CeO2–rare earth oxides (Sm2O3, Nd2O3, Dy2O3) systems were synthesized using the method of cocrystallization of nitrate salts. On their basis, ceramic materials were obtained, which are solid solutions with a cubic lattice of the fluorite type with coherent scattering regions (CSRs) of 66–88 nm (1300°С) and open porosity in the range of 2.0–6.5
In this study, organo-inorganic composites based on an epoxy polymer and an FeO-containing oxide pigment are obtained and studied. The structure and morphology of the materials are examined using X-ray diffraction, electron microscopy, optical spectroscopy, and microhardness measurements. It is shown that the composites have a homogeneous structure and contain small (up to 100 nm) particles consisting of various iron oxides (FeO, Fe3O4, and α-Fe2O3), which exhibit strong absorption of radiation in the near-IR region of the spectrum. The resulting composites exhibit high light absorption in the near-IR spectral region and may be promising as light-absorbing elements in laser systems.
Using computational methods (ToposPro software package), a combinatorial–topological analysis and modeling of cluster self-assembly are carried out. The crystal structures Sm6Pd10Sn11-mS54 (a = 17.386 Å, b = 4.514 Å, c = 16.926 Å, β = 121.38°, V = 1134.46 Å3, C2/m) and Sm3Pd5Sn5-mS52 (a = 17.205 Å, b = 4.520 Å, c = 14.206 Å, β = 99.71°, V = 1088.8 Å3, C2/m) are studied. For Sm6Pd10Sn11-mS54, 48 variants for identifying cluster structures with the number of clusters N = 3 (15 variants), 4 (22 variants), and 5 (11 variants) are established. The self-assembly of a crystal structure involving a cluster is considered. Cluster K6-1 = 0@6(Sm2Sn2Pd2) has the form of a double tetrahedron with the center at C1(4e, –1); cluster K6-2 = 0@6(Sm2Pd2Sn2) is a double tetrahedron with the center at C2(4f, –1); cluster K5 = 1Sn@4(Pd2Sn2) has the form of two linked three-atom PdSn2 rings with a common Sn atom at the 2c position with 2/m symmetry; cluster K4 = 0@4 (Pd2Sn2) is a tetrahedron with the center at the 4g position with symmetry 2; and cluster K3 = 0@3(SmSnPd) is formed by three atomic rings with the center at the 8j position. For Sm3Pd5Sn5-mS52, 41 variants of identifying cluster structures with the number of clusters N = 3 (21 variants) and 4 (20 variants) are established. The self-assembly of the crystal structure involving a cluster is considered. Cluster K6-1 = 0@6(Sm2Pd2Sn2) is a double tetrahedron with the center at C1(4e, –1); cluster K6-2 = 0@6(Sm2Pd2Sn2) is a double tetrahedron with the center at C2(8j, 1); cluster K5 = 1Sn@4(Pd2Sn2) consists of linked PdSn2 rings with a common Sn atom at position 2a with 2/m symmetry; and cluster K3 = 0@3(SnPd2) is formed by three rings with the center at position 4h (1/2, 1/3, 1/2). The symmetry and topological code of the self-assembly processes of 3D structures from precursor clusters was reconstructed in the following form: primary chain → layer → framework.
In this study, hydrosilicates with a chrysotile structure in the MgO–NiO–MeO–Me′O–SiO2–H2O (NaOH) systems are obtained using the reverse precipitation method followed by hydrothermal treatment, where Me and Me′ are Cu and/or Fe. The phase and elemental compositions are determined by X-ray spectral microanalysis and X-ray phase analysis, and the parameters of the crystal cell of the samples are calculated. The influence of the initial Ni-based nanoplatelets with Ni0.95 – xMgxCu0.05(OH)2/ Ni0.95xMgxFe0.05(OH)2/Ni0.90 – xMgxFe0.05Cu0.05(OH)2 composition is studied on the formation of mixed hydrosilicate nanotubes of the corresponding compositions with a chrysotile structure under hydrothermal conditions. The structure, morphology, and particle size parameters of the obtained nanopowders of mixed composition with a chrysotile structure are determined. The thermal stability of the obtained samples is determined using synchronous thermal analysis.
This article analyzes the acid–base characteristics of the surface of high-silica quartzoid glasses (QGs) containing cesium, and their interaction with an aqueous environment, which arise from changes in the functional composition of the surface and the desorption of cesium ions. The concentration of surface active centers with pKa = 5.0, 6.4, 8.0, and 14.2, as well as the dependence of their quantity on the cesium content in the glass and the conditions of QG synthesis, are studied.
In this study, the properties of TiS3 are investigated as a potential electrode material for electrochemical multivalent Ca- and Mg-ion batteries. Using density functional theory, we carry out calculations to thoroughly study this material. It is found that TiS3 is the most suitable material for cathodes of Ca-ion batteries. Intercalation of Ca2+ cations in TiS3-based cathode materials turned out to be energetically favorable, with an operating voltage of 1.98 V relative to Ca/Ca2+. This result is noteworthy because high-voltage electrodes for multivalent batteries are relatively rare. Diffusion coefficients of Mg2+ and Ca2+ amounted to 6.59 × 10–13 and 4.03 × 10–21 cm2 s–1, respectively. The diffusion coefficient can be further improved by lattice strain engineering and the use of two-dimensional materials. The maximum theoretical capacity values were 618 and 588 mAh/g for Mg0.5TiS3 and Ca0.5TiS3, respectively. The specific stored energy of Ca0.5TiS3 amounted to 1132 W h/kg, which exceeds that of LiCoO2 (1070 W h/kg), despite its lower electrochemical stability.
Young’s modulus (elastic modulus) of ceramics is a fundamental property that influences the mechanical characteristics of the material. When designing a ceramic material, a large number of experiments are required to determine the influence of phase composition on the elastic modulus. To quickly select the composition of a composite, it would be optimal to calculate its properties; however, today, there is no consensus on the dependence of Young’s modulus of composite materials consisting of brittle components on their composition. This paper proposes an equation for calculating the elastic modulus of a diamond–silicon carbide composite, which includes its phase composition, elastic moduli of the phases, composite porosity, and pore shape factor, which allows for a fairly accurate prediction of the material’s properties.
For the first time, a single-phase sample with a stoichiometry of 1 : 2 : 1 (Cs2B4SiO9) is obtained in the Cs2O–B2O3–SiO2 system using the solid-phase reaction method. It is shown that excess silica leads to stabilization of this phase even under conditions of a deficiency of B and Cs. The thermal behavior up to 950°C is investigated using DSC, TG, and X-ray diffraction, in comparison with the annealing and quenching method. It is shown that Cs2B4SiO9 melts incongruently with the formation of CsBSi2O6. According to dilatometry measurements, the average linear coefficient of thermal expansion (LCTE) of Cs2B4SiO9 in the region up to 400°C is 16 × 10–6°C–1 and 26 × 10–6°C–1 in the temperature range of 450–600°C.
