Inorganic Materials: Applied Research最新文献

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.

Experimental studies were conducted on the high-temperature forming of materials based on TiB/TiAl(Nb, Mo)B under process conditions that combine combustion in the mode of self-propagating high-temperature synthesis (SHS) of the initial powder components and their shear deformation following the passage of the combustion wave—free SHS compression. The objects of study were composites consisting of 100% TiB–(20–40) wt % Ti (TiB layer) and TiAl(Nb, Mo)B alloy (at %: 51.85 Ti–43 Al–4 Nb–1 Mo–0.15 B), as well as two-layer composite materials with the following layer proportions, vol %: 70TiB/30TiAl(Nb, Mo)B, 50TiB/50TiAl(Nb, Mo)B, 30TiB/70TiAl(Nb, Mo)B. The degree of deformation was chosen as the criterion for formability of the composites during shear deformation. It was established that, by varying the composition of each layer in the composite and the technological parameters of free SHS compression, it is possible to regulate the degree of deformation from 0.2 to 0.55. It was shown that the technological parameters of free SHS compression (holding time, pressing pressure, deformation rate) and the initial composition affect the formability and structure of the composites. The structural features and phase composition of the composites obtained were studied. It was demonstrated that a diffusion zone forms between the ceramic and intermetallic layers as a result of chemical interaction, the size of which can be regulated within the range of 30–150 μm.

A method for obtaining europium and gadolinium hafnates with the general formula Eu_2–xGd_xHf₂O₇ at x = 0–2 using microwave radiation is considered. The influence of the duration of microwave treatment and the temperature of subsequent calcination on the phase composition of europium and gadolinium hafnate powders is investigated. The optimum microwave treatment time for powder systems that ensures the maximum content of europium hafnate and gadolinium hafnate in the phase composition of the material is established. Deviations from the found optimal duration of microwave exposure result in samples containing phases of individual oxides of the initial metals, namely, hafnium dioxide and rare earth element oxides. Heat treatment at 1350°C intensifies the process of ordering the crystal structure, facilitating the transition from the metastable fluorite phase to the stable pyrochlore phase. This conclusion is supported by the calculated unit cell parameters of Eu_2–xGd_xHf₂O₇ compositions at x = 0 and 2 that underwent heat treatment at 1200–1450°C. In systems with x = 0.5–1.5 annealed at 1500°C, the dependence of the structural type in which they crystallize on the duration of microwave treatment is determined.

Abstract—This research studied the effect of centrifugal casting on the mechanical properties of deformable semi-finished products made of aluminum alloys of the Al–Zn–Mg–Cu and Al–Mg systems for space technology products. The study was carried out on sheets with a thickness of 3 mm and a rolling ring with a thickness of 10 mm. The samples were obtained from annular cast blanks measuring 350/240 mm (outer/inner diameter) cast by centrifugal casting. Hardness measurements were carried out along the width of the cast ring. The measurement results showed that the hardness practically did not change over the entire width, except for a zone at a distance of 5 to 7 mm from the inner edge of the ring. In this zone, the hardness decreases sharply. It has been determined that deformed semi-finished products obtained from blanks cast by centrifugal casting have minimal anisotropy of strength properties. The properties of the rolling ring of the Al–Mg alloy system exceed the properties of similar products manufactured using standard technologies. The proposed technology for manufacturing solid-rolled rings from blanks obtained by centrifugal casting will not only increase the reliability of products with a significant reduction in labor intensity, but also reduce their weight by increasing their mechanical characteristics.

Analysis of the mechanical behavior of aluminum reinforced with metallized spheres is carried out. Samples of reinforced aluminum obtained by improved casting technology are tested for bending. The role of metallized spheres in resistance to deformation is studied. The dependence of the bending strength on the diameter of the reinforcing spheres is determined. It is established that the use of spheres of minimum size is preferable, since the maximum load is achieved with low deformation and elongation of the sample. The use of polystyrene foam spheres coated with a copper–graphite layer results in a lightening of the product by up to 30% of the total weight.

The structure and thermal stability of the amorphous alloy Al₈₅Ni₅Fe₇La₃ in the initial rapidly quenched state and after xenon ion irradiation with energy of 167 MeV in the range of fluence values of 10¹²–2 × 10¹⁴ ions/cm² were studied. On the basis of the modeling of defect formation profiles, the heterogeneity of the defect distribution over the thickness of the irradiated sample was found. The mean free path of xenon ions was determined, which determines the zone of maximum accumulation of radiation defects. It is in this zone that nanocrystallization with the primary precipitation of the metastable intermetallic Al₈(Fe,Ni)₂La was detected by electron microscopy methods. A comparative analysis of the alloy structure after quenching, irradiation and annealing was carried out using complex structural research methods. It is shown that irradiation leads to a decrease in the degree of short-range order in an amorphous matrix and increases the thermal stability of an amorphous nanocrystalline structure partially crystallized as a result of irradiation.