卷 53, 编号 4 (2017)

The SnTe–Sb₂Te₃–Te system has been studied in the temperature range 300–430 K using emf measurements on reversible concentration cells of the type (–)SnTe(s) | liquid electrolyte, Sn²⁺ |(Sn–Sb–Te)(s)(+). The system has been shown to consist of two three-phase regions, separated by the SnSb₂Te₄–Te tie line. The best fit equation for the temperature-dependent emf data has been used to evaluate the partial thermodynamic functions of the SnTe and Sn in the alloys. Using these data, subsolidus phase diagram data for the SnTe–Sb₂Te₃–Te system, and relevant thermodynamic functions for SnTe and Sb₂Te₃, we calculated the standard Gibbs energy of formation, standard enthalpy of formation, and standard entropy of the SnSb₂Te₄ compound.

The Tl₂Te–Tl₅Te₃–Tl₉TbTe₆ system has been studied using differential thermal analysis, X-ray diffraction, and microhardness measurements. We have mapped out a number of vertical sections, the 680 K isothermal section of its phase diagram, and projections of its polythermal projections of its liquidus and solidus surfaces. The field of solid solutions with the Tl₅Te₃ structure (δ-phase) has been shown to account for more than 90% of the area of the composition triangle. Tl₂Te-based solid solutions (α-phase) exist in a narrow composition region.

Dense B₄C-based materials containing up to 4.9 wt % Si have been produced by hot pressing in the temperature range 1600–1700°C. In this process, the silicon melts to form a liquid phase, which improves the sinterability of the material. The boron carbide partially dissolves in the liquid Si to form silicon carbide between the B₄C grains. The relative density, bending strength, Vickers hardness, and fracture toughness of the materials obtained in this study are 99.0 ± 0.1%, 584 ± 12 MPa, 39.4 ± 0.1 GPa, and 5.3 ± 0.2 MPa m^1/2, respectively. The materials experience predominantly transcrystalline fracture.

Transmission and spontaneous photoluminescence excitation spectra of CsCdBr₃:Tm (1 and 2.5 at % Tm) crystals have been studied under different optical pumping conditions. The results demonstrate that the anti-Stokes luminescence intensity in the thulium-doped crystals is higher at the higher doping level. We have determined the resonance wavelengths of IR photons for two-photon excitation of visible luminescence in CsCdBr₃:Tm and identified the corresponding electronic transitions in thulium-related emission centers for Stokes and anti-Stokes luminescence.

High-purity arsine suitable for the growth of gallium arsenide-based epitaxial heterostructures has been prepared by processing a lewisite detoxification product: hydrolytic sodium arsenite. The proposed method involves the dissolution of hydrolytic sodium arsenite in water; electrolysis of the solution, resulting in the formation of arsenic acid and sodium hydroxide, which is subsequently used to absorb released chlorine; electrochemical arsine synthesis from the arsenic acid; and arsine purification by fractionation to a level of 99.9999%.

We have synthesized Au/MnO_x–CeO₂ nanocatalysts for the low-temperature oxidation of carbon monoxide. Gold nanoparticles applied by the deposition precipitation (DP) method were used as an active phase. The composition, structure, and textural characteristics of the materials and the charge state of the components of the catalysts were studied using X-ray diffraction, X-ray photoelectron spectroscopy, highresolution transmission electron microscopy, inductively coupled plasma mass spectrometry, and low-temperature nitrogen adsorption measurements. The carbon monoxide concentration in the catalytic oxidation products was determined by gas chromatography. The influence of calcination temperature on the charge state of the components of the surface layer of Au/ MnO_x–CeO₂ and the catalytic activity of the materials was examined. The catalytic activity of the materials was shown to be determined to a significant degree by the Mn³⁺, Au³⁺, and weakly bound oxygen concentrations in the surface layer.

A Li₃BaCaY₃(MoO₄)₈:Er³⁺ phosphor with a scheelite-like structure (sp. gr. C2/c) has been synthesized and its luminescence properties have been studied. The phosphor has been characterized by X-ray diffraction, differential thermal analysis, and IR spectroscopy.

We have examined the effect of synthesis and heat-treatment conditions on the phase composition of composites based on hydroxyapatite and zirconia. The zirconia present in the composite based on a mechanical powder mixture crystallizes predominantly in tetragonal symmetry at heat-treatment temperatures in the range 400–600°C and in monoclinic symmetry at 800°C. The zirconia present in the composites prepared via the mixing of hydroxyapatite gel with hydrated zirconia sol or coprecipitation crystallizes only in monoclinic symmetry. Annealing at 1300°C leads to the formation of a solid solution with the composition Ca_0.15Zr_0.85O_1.85 in all of the composites as a consequence of complete or partial hydroxyapatite decomposition and the thermal diffusion of Ca²⁺ ions into the ZrO₂ lattice. In the composites prepared by liquid-phase processes, heat treatment in the range 800–1300°C produces the smallest changes in the hydroxyapatite structure, which ensures high biological activity of the material.

A 5Ti + 3Si powder mixture has been studied by X-ray diffraction in order to assess the effect of mechanical activation (MA) time on its structural state. MA for 11 min or a shorter time leads to the degradation of the crystal structure and partial amorphization of titanium and silicon. MA has been shown to produce different structural changes in silicon and titanium. MA reduces the crystallite size of silicon to 300 nm and increases microstress to 700 MPa, whereas the only consequence of the MA of Ti is an increase in microstress to 550 MPa. MA for more than 11 min initiates a solid-state reaction which results in the mechanochemical synthesis of Ti₅Si₃.