Inorganic Materials: Applied Research最新文献

The issue of pore formation in the process of impregnation with a low-viscosity binder of the reinforcing layer of silica thread K11S6–170BA–100% satin weaving with a linear density of 170 tex is considered with a breaking load of at least 34.3 N (3.5 kgf). The mathematical apparatus necessary for the development of impregnation technology is considered in order to determine the optimal method of impregnation, which affects the type and size of the pores formed during the impregnation process. An assessment of capillary forces depending on the architectural parameters of the woven filler is carried out. The optimal interval of impregnation rates of the reinforcing layer during transfer molding of a product made of polymer composite material is determined, which makes it possible to minimize pore formation in the structure of the resulting laminate, which proceeds without the release of low-molecular reaction products, which makes it possible to reduce the porosity of the resulting part. The hardware and software complex was used to obtain results on the degree of impregnation of harsh cotton fabric without intensifying action.

The results of studying the possibilities of extracting strategic metals (Au, Ti) from gold-ilmenite placers located in the south of the Russian Far East are presented in this article. The need to apply hydrofluoride techniques in order to create a basis for technology to enrich titanium-bearing deposits is justified. The experience gained through the deep processing of gold ilmenite mineral resources will help us to identify ways to develop complex deposits in the Russian Far East in accordance with the principles of sustainable use of natural resources and environmental protection.

Study of the interaction of uranium dioxide granules, having different histories of origin, with hydrogen fluoride, the necessity of preliminary reduction of uranium oxides before conversion was substantiated.

This article considers issues related to the development of technology for producing gallium nitride templates with a reduced dislocation density on a sapphire substrate. The authors assembled and launched a complex of MOCVD equipment and set up control systems for the growth of in situ structures. Optimum technological modes for the step-by-step production of gallium nitride buffer layers on a sapphire substrate have been developed. These modes include substrate preparation by annealing and nitridation, growth of gallium nitride nucleation layers with their subsequent annealing, coalescence of a single-crystal layer, formation of a buffer layer with the required thickness, properties and doping levels based on various technological approaches to the formation of the nucleation layer. Experimental samples with a smooth, planar surface were obtained: with a pulsed supply of trimethylgallium, the thickness of the grown layer was 2.7–2.8 μm at a growth rate of 1.1 μm/h, full width at half maximum of the diffraction peak is 570 arcsec, the dislocation density is 2.7 × 10⁷ cm^–2; with a continuous supply of trimethylgallium, the thickness of the grown layer was 2.7–2.8 μm, the growth rate was 2.8 μm/h, full width at half maximum of the diffraction peak of 608 arcsec, the dislocation density was 5.1 × 10⁷ cm^–2, the electrical properties of this material were: n-type, carrier concentration was n = 1.0 × 10¹⁷ cm^–3, carrier mobility μ = 113 cm/Vs. Good correlation is observed between the results of thickness and surface morphology studies on SEM and in-situ structure growth monitoring systems. It is shown that the obtained samples in defect density and basic characteristics correspond to commercial templates of gallium nitride grown on sapphire substrate, presented in the world market.

A comparative study was conducted on four different bioactive glass compositions: 45S5, 52S4.6, two variants of 52S4.6 with varying weight percentages of magnesium oxide (MgO, 2.5 and 5.0), and a control group. The degradation rates and effects of these materials on pH levels in simulated body fluids were investigated, as well as the cytotoxicity and cellular proliferation of these materials using an adenocarcinoma cell line. The results showed that 52S4.6 bioactive glass, especially when doped with magnesium, had lower toxicity and a slower degradation rate compared to 45S5 bioactive glass. In addition, this type of bioactive glass had a weaker alkalinizing effect on biological media, suggesting that it may be more suitable for regenerative medicine and tissue engineering applications. In addition, magnesium-doped glass variants have been found to be more suitable for bone and dental surgery due to their ability to promote cell growth.

By nitriding the Zr–V pair while preserving the shape of the original metallic blanks, binary compact nitrides were synthesized. The kinetic and voltammetric dependencies of the nitriding process were determined. For the individual metals and the weld zone, interaction with nitrogen proceeds via different mechanisms. Pure metals react with nitrogen through the formation of three- and two-layered structures. Nitriding of the weld zone is accompanied by the decomposition of the Zr–V solid solution with segregation of metallic vanadium at grain boundaries as a separate phase. Simultaneously, mutual dissolution occurs between the nitrogen reaction products: nitrogen solid solutions in both metals and their nitrides of varying stoichiometry. The ceramic formation process is accompanied by diffusion of vanadium into the region of its lower concentration and the formation of the intermetallic compound Zr_0.3V_0.6N_0.1, which does not interact with nitrogen at the synthesis temperature. For gradient and ceramic structures (Zr–V)N_x in the temperature range from –195.7 to +550°C, the nature of the dependence of the thermoelectromotive force (thermo-EMF) on nitriding time was established and its magnitude was evaluated. The obtained ceramic and gradient materials can be used as ceramic thermoelectric converters.

The Mathcad 15.0 computer algebra system is used to predict the deformation behavior of hyperelastic materials. The results we obtained were compared with the predictions of other models. The models are ranked against the rating given in papers dealing with the finite deformation mechanics. The list comprises seven models: neohookean, Mooney–Rivlin (2-parameter), Mooney–Rivlin (3-parameter), Ogden, polynomial, Veronda–Westmann, and the Yeoh model. The prognostic accuracy of the results of model calculations relative to the experimental data is estimated using mathematical statistics indicators. An example of calculating the parameters of hyperelastic deformation model is given for a biomaterial sample (a piece of skin taken from the human back).

Composite materials based on a mixture of high-density and low-density polyethylenes, including additives of fine nickel oxide, were investigated using X-ray phase analysis (XPA), differential thermal analysis (DTA), and scanning electron microscopy (SEM). An improvement in the strength, deformation properties, and thermo-oxidative stability of the composites was revealed upon the introduction of fine nickel oxide, which is apparently associated with the formation of interfacial bonds between the nickel-containing nanoparticles and the components of the polymer composition. It was shown that nanocomposites based on a mixture of high-density and low-density polyethylenes, including additives of fine nickel oxide, can be processed by both pressing and methods of injection molding and extrusion, thereby expanding their fields of application. Small amounts of the nanofiller introduced into the polymer act as structure-forming agents, that is, artificial crystallization nuclei, which contributes to the formation of a fine spherulitic structure in the polymer, as characterized by the improved physical–mechanical and thermal properties of the resulting nanocomposite.

The processes of loading and release of rhodamine B from polycaprolactone nanofibers and a composite material based on mineralized polycaprolactone nanofibers, both modified and unmodified with magnetite nanoparticles, were investigated. It was established that the amount of rhodamine B loaded into polycaprolactone nanofibers mineralized with calcium carbonate microparticles exceeds the amount of dye incorporated into “pure” polycaprolactone fibers by 1.5 times.

Thermodynamic conditions of the influence of the gas phase composition on the growth of silicon nanowires (NWs) using particles of various metals as growth catalysts have been determined. The dependence of the growth rate of silicon NWs in the open chemical system SiCl₄–H₂ on the molar ratio of the components [SiCl₄] and [H₂] has been experimentally established. With an increase in the molar ratio [SiCl₄]/[H₂], the growth rate of NWs passes through a maximum, and at high concentrations of silicon tetrachloride, due to interaction with the gas phase, the etching of surface layers of crystals and the substrate is possible. It is shown that, in contrast to the SiH₄–H₂ system, the observed extreme behavior of the dependence of the NW growth rate on the composition of the gas phase is due to the reversibility of the chemical reaction between SiCl₄ and H₂. A direct correlation between the thermal conductivity coefficient of the metal-catalyst and the growth rate of NWs is established. A thermodynamic model of the process, which determines the thermodynamic conditions for the preferential growth of Si NWs by the vapor → liquid → crystal mechanism in relation to crystallization by the vapor → crystal mechanism, is considered. The values of standard changes in molar enthalpy, entropy, and Gibbs energy of some reactions occurring in the chloride-hydrogen process for obtaining silicon NWs are calculated. The range of changes in the gas phase composition for stable growth of NWs at a given growth temperature is determined.