Inorganic Materials

Low-dimensional flakes of the MX₂ (M — Ti, Zr, Hf, V, Nb, Ta, Mo, W, and X – S, Se, Te) in various organic solvents were obtained by liquid-phase exfoliation during ultrasonic treatment. The Hansen parameters of the obtained low-dimensional materials were calculated based on the Hansen parameters of the solvents and the measured optical absorption. It has been shown that the optical absorption and, consequently, the effectiveness of the solvent as an exfoliating agent increases with a decrease in the Hansen distance between the solvent and the dichalcogenide. The possibility of using the cosine distance between these values as an alternative to the Hansen distance is considered.

The paper presents experimental results of high-temperature synthesis of cast nitride materials in the V–Ti–N system. For the first time, cast materials based on solid nitride and intermetallic solutions of the V–Ti–N system have been obtained by self-propagating high-temperature synthesis in the combustion mode from a powder mixture of V₂O₅ + Al + AlN + Ti. The syntheses were carried out in a 3 L reactor at a nitrogen pressure of 5 MPa. The initial mixtures were placed in quartz crucibles. When burning mixtures with a titanium content of α_Ti = 0–7.5%, the final products melt, and they are completely separated (separated) into the oxide (upper ingot) and “metallic” (lower ingot) parts. upon combustion of the initial (base) mixture, which does not contain titanium (α_Ti = 0), cast materials consisting of vanadium nitride V₂N are synthesized. The introduction of titanium into this mixture leads to a significant change in the composition and microstructure of the final products. Titanium introduced into the initial mixture is dissolved in vanadium nitride to form solid solutions in V₂N. In addition, titanium participates in the redox reaction with vanadium oxide to form oxides that pass into the oxide (upper) ingot. The resulting end products were characterized by X-ray diffraction and electron microscopy. Their structural and phase components have been studied.

For the first time, theoretical dependences of the width Г(eV) of the X-ray photoelectron spectra of the outer (OVMO) and inner (IVMO) valence molecular orbitals electrons without taking into account the An 6s electrons, as well as the intensities ratio of these spectra (I_OVMO/I_IVMO = OVMO/IVMO) calculated by the relativistic discrete variation method for AnO₂ (An = Th–Lr) have been obtained depending on the atomic number Z. Satisfactory agreement has been established with the available relevant experimental data for AnO₂ of light actinides. The decrease in the OVMO XPS width in the Pa–Lr series is associated with a shift in the partial density of states of the An 5f electrons to the OVMO bottom while the increase in the IVMO width is mainly due to an increase in the magnitude of the spin-orbit splitting (ΔE_sl) of the An 6p-electrons. It has been found that the OVMO intensity is mainly related to the An 5f- and 6d-electrons, since the photoionization cross sections for these electrons are significantly larger than those for the An 7s-, 7p-, and O 2p-electrons.

Thulium stannate with a pyrochlore structure was prepared by solid-phase synthesis. The heat capacity of polycrystalline Tm₂Sn₂O₇ was measured by adiabatic and differential scanning calorimetry in the temperature range of 4.51–1573 K. The values of standard mole entropy, enthalpy change, and reduced Gibbs energy of Tm₂Sn₂O₇ have been calculated from smoothed heat capacity values. The standard Gibbs energy of formation of polycrystalline thulium stannate at T = 298.15 K has been evaluated.

High-entropy single-phase oxides with the perovskite structure Ca(Ti_0.25Sn_0.25Nb_0.125Ta_0.125M_0.25)O₃ (M = Fe, Zr) were synthesized for the first time by a simple one-step ceramic method and characterized by X-ray diffraction analysis. The powders were subjected to mechanical activation, which resulted in a partial phase transition from an orthorhombic phase to a tetragonal one. Both compositions demonstrated the ability to reduce Cr(VI) when illuminated with uV light and high sorption activity with respect to the methylene blue dye.

The paper investigates the polishing processes of two-phase Y₂O₃–MgO ceramics in order to improve the surface quality for optical applications. A comparative analysis of three processing methods is carried out: mechanical, chemical-mechanical and magnetorheological polishing. Consistent application of these approaches, including preliminary deep grinding and polishing to eliminate the disturbed layer, can significantly improve the cleanliness and accuracy of the treated surface. The final magnetorheological polishing ensures the achievement of an average roughness (R_a) of 0.6 nm, a standard deviation (RMS) of 0.8 nm, surface purity of the 2nd class according to GOST 11141-84 and shape accuracy of optical elements up to λ/4. Based on the results obtained, experimental optical elements were manufactured that meet modern requirements for a wide range of optical applications.

In order to assess the effect of the microstructure on the scattering of the impact toughness of hot-rolled steel, samples were examined after Charpy impact tests at a temperature of −60° C. The microstructure of the samples under the fracture surface has been studied. It has been experimentally shown that most of the cleavage facets are located in martensite-bainite interlayers in the ferrite-pearlite microstructure, which are formed in the axial region of the rolled product. Despite the fact that the proportion of martensite-bainite interlayers in the microstructure does not exceed 4%, their size and location relative to the applied stresses determine the impact toughness of standard transverse samples. The minimum values of impact toughness correspond to the largest total width of martensite-bainite interlayers and the highest concentration of Mn, Si and P. To assess the effect of the formation of martensite-bainite interlayers on the impact toughness, an indicator of the inhomogeneity of the microstructure C is proposed, taking into account both the width of the interlayers and the concentration heterogeneity in Mn, Si, and P.