Inorganic Materials: Applied Research最新文献

The interaction between zirconium dioxide-based pellets and carbon-containing material has been studied, including: thermodynamic evaluation was given, the reaction mechanism was proposed using the ideas about the chain mechanism of interaction between the granule and gaseous chlorinating agent, laboratory experiments on chlorination of granules with gaseous chlorine, including in fluidization mode, were performed.

Samples of structural aviation steel VNS-5 were implanted with carbon ions using ion-beam implantation. The modified layer was about 200 nm; the carbon content did not exceed 10% in this layer. This study shows that the VNS-5 specimens implanted with carbon ions exhibit high low-cycle fatigue properties. The origin and behavior of fatigue cracks in implanted samples differs from non-implanted material and does not depend on the magnitude of the load at low-cycle fatigue. The high surface residual compressive stress in the implanted material helps to suppress the nucleation and spread of surface cracks, thereby improving the fatigue resistance of steel.

The influence of cyclic tensile deformation in the loading/unloading mode for up to 45 cycles in the superelastic loop region on the inelastic characteristics and deformation structure of the nanocrystalline aging superelastic alloy Ti–50.9 at % Ni is studied. It is established that the distinctive feature of the initial stage (up to 5–10 cycles) is the accumulation of dislocations and the formation of a three-dimensional network with nodes pinned by Ti₃Ni₄ particles, limiting the dislocation activity. Achieving a high level of stresses in the strengthened dislocation structure with an increase in the number of cycles to 10–20 contributes to a decrease in the shear stability of the B2 structure and the occurrence of additional accommodative deformation mechanisms. The result of the relaxation of internal stresses arising near the boundaries of primary grains and their joints is the formation of kink-like deformation bands, providing a collective nature of the reorientation of the crystal lattice.

The conditions of healing of surface defects and structural strengthening of additive surface of Ti-ZrNb samples obtained by selective laser melting (SLM) with subsequent vacuum electric spark treatment (EST) by low-melting AlCaZrY electrode were investigated. The effect of electrode polarity on kinetics of mass transfer, structure, chemical and phase composition of modified surface was studied. The investigations were performed by methods of scanning electron microscopy, energy-dispersive spectroscopy and optical profilometry. It is shown that the use of the optimal mode of EST reduces the roughness of the additive surface by 3 times as a result of local melting of protrusions and filling of cavities up to 200 μm deep with the melt formed in-situ during the EST process. It is found that the structure of such a coating consists of an aluminum matrix strengthened by dispersed intermetallic inclusions Ti₃Al with a size of about 4 μm. The applied treatment made it possible to increase the wear resistance of the TiZrNb alloy against a steel ball by 2 times, and also to reduce the friction coefficient from 0.37 to 0.29.

Titanium dioxide nanoparticles were synthesized by the sol-gel method. The phase composition (amorphous), particle size (from 20 to 80 nm), pycnometric density (3.50 g/cm³), specific surface area (300 m²/g) and band gap width (3.4 eV) were determined. As(III) sorption experiments were carried out in the dark and under 440 nm LED irradiation, varying the pH of the aqueous medium from 1 to 12 and the sorption time from 15 to 180 min. Sorption kinetic curves were obtained and the maximum allowable concentration of arsenic in water was achieved.

Materials based on selenite-substituted hydroxyapatite and collagen were synthesized. Chemical analysis of solutions after precipitate separation confirmed the substitution of phosphate ions by selenite ions in the hydroxyapatite structure. Results of elemental analysis, X-ray phase analysis (XRD), and infrared spectroscopy (IR) verified these substitutions in the hydroxyapatite structure. Morphological studies revealed a trend of increasing aggregate size with higher concentrations of selenite ions and collagen. Scanning probe microscopy showed that samples with selenite ions exhibited greater surface roughness compared to collagen-containing samples. The BET (Brunauer-Emmett-Teller) method provided specific surface area measurements of synthesized powders. The highest values were recorded for samples with 10.0 g/L selenite ions, while the lowest were for collagen-containing materials. Resorption studies in TRIS-buffer (pH 7.40) and simulated body fluid (SBF) demonstrated increased dissolution rates for samples with high selenite ion content. Collagen addition reduced dissolution rates. Thermal analysis (200–800°C) identified the sample with lowest selenite ion concentration (1.5 g/L) as most thermally stable.

The problem of developing effective methods for predicting the defining characteristics of polymer composites under the influence of extreme environmental factors characteristic of the climatic conditions of the Arctic and Subarctic zones has been investigated. The formulated problems of developing effective forecasting methods are investigated within the framework of refined variational formulations based on modern provisions of the kinetic theory of strength. A number of fundamental principles and concepts were introduced that make it possible to optimally coordinate the defining parameters calculated on the basis of the constructed mathematical models at the macro level with the defining parameters of physical models describing molecular interactions at the micro level. A methodology has been developed for matching the parameters of mathematical and physical models at the micro and macro levels, which made it possible to solve the problem of restoring the parameters of physico-chemical processes occurring at the micro level, leading to destructive changes in composites and deterioration of their characteristics over time. Based on the conducted physical experiments, an objective assessment of the parameters of destructive chemical reactions in composites was carried out, which made it possible to construct effective generalized models of durability for a long-term period, as well as to conduct a constructive analysis of the influence of individual extreme factors on durability. The results of computational experiments are presented.

This paper presents research on the methylation of silicon dioxide surfaces derived from sulfuric acid decomposition of nepheline concentrate. Two methylation approaches were investigated: (1) direct attachment of methyl groups to the silica surface in nonpolar media with water molecule condensation, and (2) intermediate formation in an alkaline medium. Through comprehensive physicochemical characterization, we analyzed the morphology, surface elemental composition, and structural-surface properties of the methylated silica samples. The study revealed that silica subjected to direct methanol treatment exhibits a higher specific surface area (496 m²/g) compared to the sample prepared via alkaline intermediate formation (278 m²/g), likely due to the more complex synthesis mechanism of the latter. IR spectroscopy confirmed the presence of characteristic –C–H and –C–C-bond vibrations, indicating successful surface methylation. These findings, supported by porometry data, demonstrate partial hydrophobization of the silica surface and enhanced affinity for nonpolar organic compounds. The results suggest potential applications in developing membrane filters for organic compound separation.

In this work, the effect of a polar nanoporous matrix of barium titanate on the phase transition temperatures of embedded thiourea was investigated. An increase in the ferroelectric-paraelectric transition temperature of embedded SC(NH₂)₂ has been detected. This is explained by the fact that due to the higher coefficient of thermal expansion for thiourea compared to barium titanate, when the temperature drops from room temperature (not stressed) to 178 K (stressed), the compression of thiourea crystals occurs faster than barium titanate.

Magnetic nanoparticles of maghemite (γ-Fe₂O₃), cobalt (CoFe₂O₄), and zinc ferrites (ZnFe₂O₄) with varied size and morphology were synthesized by means cryochemical technologies. The synthesis route involved cryogenic spray drying of organic metal salts followed by their subsequent thermal decomposition. The use of iron(II) gluconate and iron(III) ammonium citrate as precursors results in the formation of micron-sized maghemite macroporous particles and 50–150 nm nanoparticles aggregated into micron-sized plate-shaped structures, respectively. Both maghemite samples exhibited an admixture of goethite. If solutions of iron acetylacetonate with zinc or cobalt acetate are used as precursors, then ZnFe₂O₄ nanoparticles with average size 10 nm and CoFe₂O₄ nanoparticles with average size 15 nm are formed.