Inorganic Materials: Applied Research最新文献

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.

The electrical, mechanical and optical properties of silicon-carbon films obtained by electron beam evaporation of silicon carbide in an argon-oxygen gas mixture in the pressure range 3–5 Pa are presented. The electron beam was generated by a fore-vacuum plasma electron source. It is shown that with an increase in the oxygen content in the gas, the resistivity of the films increases, the hardness decreases and the optical band gap raises. Measurements of the composition and analysis of IR transmission spectra indicate the replacement of silicon-carbon bonds with silicon-oxygen bonds as the gaseous medium is enriched with oxygen.

Porous composite materials have been developed with a matrix composed of a mixture of polyvinylpyrrolidone (PVP) and sodium alginate (ALG), in which ceramic particles of double (manganese- and strontium)-substituted tricalcium phosphate (TCP) are distributed. X-ray diffraction analysis (XRD) demonstrated that the main crystalline phase of the (manganese and strontium)-substituted TCP is whitlockite. In vitro studies revealed that all tested materials are not adhesive to cells and exhibit no cytotoxic or inhibitory effects on them. The porous composite materials characterized by a high rate of bioreabsorption of ceramic particles and a strong potential for antibacterial activity and osteoinductive properties due to ion diffusion and changes in the surface layer properties can be used in reconstructive surgery for the restoration of bone tissue function.

Using machine learning programs, the prediction of 250 not yet obtained compounds of composition ABX (where A and B are different chemical elements, and X are As, Sn, Sb, Pb or Bi) with a crystal structure of the MgAgAs type was carried out and the values of their crystal lattice parameter were estimated. Using the cross-validation method, the best machine learning algorithms were selected for subsequent predicting. When making predicts about compounds that have not yet been synthesized, the most accurate programs were based on neural network training algorithms, support vector machines and k-nearest neighbors, for which the accuracy was determined to be 88.5, 91.0, and 88.4%, respectively. When predicting the value of the crystal lattice parameter of the predicted compounds, the best results were obtained using programs based on the Bayesian Ridge methods (coefficient of determination R² = 0.959, mean absolute error MAE = 0.0370, mean square error MSE = 0.0030), ARD Regression (R² = 0.950, MAE = 0.0401, MSE = 0.0036) and Ridge (R² = 0.959, MAE = 0.0368, MSE = 0.0029), i.e., the deviation of the calculated values from the experimental ones was in the range of 0.0368 to 0.0401 A. When predicting new compounds and estimating their crystal lattice parameters, only the values of the properties of the chemical elements included in their composition were used.

The high-temperature behavior of lanthanum zirconate ceramics was studied depending on the conditions of La₂Zr₂O₇ synthesis and sintering. Lanthanum zirconate was obtained by solid-phase synthesis, the ceramics were sintered in the temperature range of 1500–1550°C at different holding times. Thermal expansion and shrinkage activity of ceramics were studied by dilatometric analysis. Linear thermal expansion coefficients (LTECs) were determined in the temperature range of 200–1200°C during heating and cooling. The LTEC of the obtained ceramics is 9.1 × 10^–6 1/K, which is significantly less than the LTEC of tetragonal zirconium dioxide doped with yttria (YSZ), 13.5 × 10^–6 1/K. The LTEC decreases as the density of the ceramics increases. The microhardness of synthesized ceramics is 6.3 GPa.

A polymer composite material based on carboxylated latex of butadiene–nitrile copolymer has been developed for the production of dipped products. The polymer composite material includes biodegradation stimulators to accelerate the degradation of finished products under natural conditions after the end of their service life. The method for producing the polymer composite material is based on preparing a latex composition using dispersions of components from the sulfur vulcanizing group and a biofiller, which can be wood flour, coffee pucks, or potato starch. A coagulant composition was selected to ensure the formation of a defect-free latex gel on the mold surfaces during the production of dipped products. Tests measuring the tensile strength of polymer films confirmed the relevance of the developed polymer composite material formulation. It was established that low-filled compositions allow obtaining products with higher strength compared to unfilled ones. Standard methods confirmed the environmental safety of products based on the developed polymer composite material and the absence of toxic effects of their degradation products on the germination and early growth of higher plants. It was found that the decomposition products not only do not negatively affect the growth of higher plants but also promote their development. It was demonstrated that dipped products of various purposes can be produced on the basis of the developed polymer composite material containing biodegradation stimulators.