Vol 53, No 10 (2017)

This paper examines the IR sensitization of Pb_0.975Sn_0.025Se films by heat treatment in air. The films were annealed in the temperature range from 403 to 723 K. Heat treatment was accompanied by the recrystallization of agglomerates in the films. The photosensitivity of the films was shown to depend on heat treatment temperature. The films sensitized in the temperature range 653–700 K offer the highest photosensitivity (80–140 μV). The observed increase in the dark resistance and voltage sensitivity of the films is probably due to the formation of oxide phases on the surface of their microcrystallites.

We have studied the structural transformations and deformation behavior of an amorphous Al₈₅Ni₁₀La₅ alloy during nanoindentation and uniaxial tension tests and assessed the influence of crystalline phases resulting from lamp processing and heat treatment. Our results confirm the high effectiveness of lamp processing: at identical phase compositions, the lamp processing time is shorter by more than two orders of magnitude. The microplasticity of the amorphous alloy has been shown to manifest itself in both nanoindentation and uniaxial tension tests. The high proportion of local plasticity in the work of indentation has been accounted for in terms of possible intercluster sliding. The observed lamp processing- and heat treatmentinduced changes in the hardness of the alloy reflect changes in its phase composition and the percentages of the amorphous and crystalline phases, which does not rule out a cluster mechanism of local deformation or its deceleration by nanocrystalline phases in the amorphous–nanocrystalline structure.

Thermal transformations of 3[Pt(NH₃)₄]Cl₂–(NH₄)₂CrO₄ (I) and 3[Pt(NH₃)₄]Cl₂–2(NH₄)₂Cr₂O₇ (II) mixtures in a solid state have been studied by thermal analysis and mass spectrometry in an inert (Ar) atmosphere and air at temperatures from 40 to 550°C. The chemical and phase compositions of the thermolysis products obtained in argon have been determined: Pt and Cr₂O₃ in mixture I and Pt, a platinum-based Pt_{1 – y}Cr_y solid solution, and Cr₂O₃ in mixture II. The thermal transformation products of mixtures I and II in air consist of two phases: Pt and Cr₂O₃. It has been shown that interactions in the mixtures proceed through the formation of a metallic chromium phase. The materials obtained in this study can find application as catalysts for low-temperature fuel cells, as well as for organic synthesis processes.

Experimental data are presented on the high-temperature synthesis of cast inorganic materials in the MgO–Al₂O₃ system. Experiments were carried out in multipurpose self-propagating high-temperature synthesis (SHS) reactors at an argon pressure p = 5 MPa. The starting mixtures used in the experiments consisted of molybdenum(VI) and magnesium(II) oxides and aluminum. It has been shown that, varying synthesis parameters, one can control the phase composition and microstructure of the final oxide products. We have optimized synthesis conditions for the preparation of single-phase magnesium aluminate spinel, MgAl₂O₄. The SHS products have been characterized by X-ray diffraction and local microstructural analysis.

We have investigated the preparation of molybdenum powders by reducing the oxide compounds MoO₃, MgMoO₄, and CaMoO₄ with magnesium vapor at residual argon pressures in the range 5–20 kPa and temperatures in the range 700–800°C. Using the MgMoO₄ and CaMoO₄ compounds as precursors, we have obtained molybdenum powders with specific surface areas of up to 20 m²/g. The powders have a mesoporous structure. The reduction of the molybdenum compounds under such conditions was accompanied by separation of the reaction products due to the removal of magnesium oxide from the reaction zone.

Amorphous yttrium iron garnet films ranging in thickness from 100 to 600 nm have been produced on single-crystal silicon substrates by sputtering a polycrystalline target with the composition Y₃Fe₅O₁₂ (yttrium iron garnet) by a mixture of argon and oxygen ions. Before film growth, AlO_x or SiO₂ buffer layers up to 0.8 μm in thickness were grown on the Si surface. The heterostructures were crystallized by annealing in air at a temperature of 950°C for 30 min. The properties of the films were studied by magneto-optical techniques, using Kerr effect and ferromagnetic resonance measurements. The Gilbert damping parameter reached 2.8 × 10^–3 and the effective planar magnetic anisotropy field was independent of the nature of the buffer layer. This suggests that the thin-film heterostructures obtained in this study are potentially attractive for use in spin-wave semiconductor devices.

We have developed a process for the sol–gel synthesis of a SiO₂-based combined additive in the presence of superplasticizers and investigated the hydration kinetics, phase composition, microstructure, and strength characteristics of a modified cement stone. The results demonstrate that combined nanoadditives accelerate hydration processes, without significantly changing the structure of the modified cement stone. The observed strength gain in the samples is due to the rapid accumulation of cementitious substance during the hardening system formation process. The results of a detailed study of modified cement systems have been used to optimize the composition of the combined additive.

A composite of polyethylene and vermiculite, a natural aluminosilicate, has been prepared by treating vermiculite with a concentrated polyethylene solution in xylene. Varying the concentration of the polyethylene solution, we obtained materials with various compositions, which were then modified by heat treatment and chemical means (by HCl solution, followed by precipitation of metal ions). We have determined the elemental composition of the composite materials, obtained their IR spectra and X-ray diffraction patterns, and evaluated their surface properties and sorption capacity for organic dyes and oil products. The chemical modification of the composite materials increases their dye sorption capacity, which correlates with the observed changes in their specific surface area and specific pore volume.

Volatile impurities have been removed from iron pentacarbonyl of natural isotopic composition by vacuum pumping. We have examined the behavior of impurities in the course of fractional distillation of iron pentacarbonyl. As a result of simple distillation, we have obtained an iron pentacarbonyl sample containing on the order of 10^–4 mol % C₃–C₆ hydrocarbon impurities, 10^–3 mol % C₇–C₈ hydrocarbons, and 10^–8 to 10^–6 wt % metallic impurities. We have estimated the effective separation factor at a distillation rate of 0.021 kg/(m² s) for a number of impurities in Fe(CO)₅.