Vol 52, No 11 (2016)

We have studied the wetting behavior of molten germanium on silica ceramics and amorphous silica coatings in vacuum at a pressure of 1 Pa and a temperature of 1273 K. The results demonstrate that the wetting of rough surfaces of ceramic samples and coatings by liquid Ge is significantly poorer than that of the smooth surface of quartz glass. The contact angle of polished glass is ~100°, and that of the ceramics and coatings increases from 112° to 137° as the total impurity content of the material decreases from 0.120 to 1 × 10^–3 wt %. Using experimental contact angle data, we calculated the work of adhesion of molten Ge to the materials studied. Its value for the surface of the ceramics and coatings decreases from 0.45 to 0.20 J/m² with decreasing impurity content, whereas the work of adhesion to a smooth glass surface is 0.55 J/m². We have fabricated fused silica test containers coated with high-purity amorphous silica. Using horizontal zone refining, we obtained germanium samples with a carrier concentration difference on the order of 10¹¹ cm^–3.

Using electrochemical deposition from an aqueous solution of Na₂S₂O₃ and CdSO₄, with a cadmium anode, we have grown CdS films on tin dioxide substrates (cathode). The CdS films have been shown to be polycrystalline, with the wurtzite structure. From the optical absorption and cathodoluminescence spectra of the films, we have determined their band gap at 298 and 78 K. With a zinc anode, we obtained polycrystalline Cd_1–хZn_хS (0 < x ≤ 0.017) films with the wurtzite structure. The Cd_0.983Zn_0.017S films have a larger band gap and higher luminescence intensity than do the CdS films.

We have studied the effect of magnesium added to the starting mixture as MgS or MgCl₂ on the performance characteristics of synthesized ZnS:Cu,Mn phosphor powders. It has been shown that the incorporation of certain amounts of magnesium into the ZnS:Cu,Mn phosphor leads to an increase in photo- and electroluminescence brightness and is favorable for Mn incorporation into the structure of the phosphor. In particular, additional doping of a dc electroluminescent ZnS:Cu,Mn phosphor with 30 mol % Mg ensured not only a shift of its luminescence spectrum to shorter wavelengths, thereby extending the color range of light sources, but also a twofold increase in its brightness.

We studied the interaction of Ti_0.40Mo_0.60 and Ti_0.34Mo_0.66 alloys with hydrogen and obtained hydrogen desorption isotherms at pressures of up to 250 MPa. At high hydrogen pressures, we observed the formation of Ti_0.40Mo_0.60Н_1.1 and Ti_0.34Mo_0.66Н_0.8 hydride phases. According to X-ray diffraction data, the hydrides consisted of phases with a body-centered cubic and face-centered cubic (CaF₂ structure) lattices. The structure of the deuteride based on the Ti_0.40Mo_0.60 alloy was studied by neutron diffraction. We identified the sites occupied by deuterium atoms and determined their occupancies.

We have studied the effect of final annealing temperature on the formation of lithium zinc titanate, its electrical conductivity, and its electrochemical performance. Li₂ZnTi₃O₈ has been shown to form in a wide range of annealing temperatures, from 673 to 1073 K. Its particle size increases systematically with increasing annealing temperature, whereas its conductivity decreases. The highest electrochemical capacity at low currents is offered by the materials annealed at 773 and 873 K, and the highest cycling stability is offered by the material prepared at 873 K.

The heat capacity of yttrium orthotantalate has been determined as a function of temperature by adiabatic calorimetry in the temperature range 0–340 K. Smoothed heat capacity data have been used to calculate the thermodynamic functions of yttrium orthotantalate.

Nanostructured TiO₂ in the form of elongated one-dimensional structures having a highly ordered layered morphology, with cobalt-containing agglomerates on their surface, has been prepared by hydrothermal treatment of CoTiO₃ powder in the presence of chitosan, a bioactive natural polymer. The synthesis products have been characterized by scanning electron microscopy, transmission electron microscopy, IR spectroscopy, X-ray diffraction, elemental analysis, and magnetic measurements. The structures have been shown to be up to several microns in length, and their typical width ranges from 100 to 400 nm. The one-dimensional structures retain high thermal stability at calcination temperatures of up to 800°C. After vacuum heat treatment at 600°C and above, the nanostructured material possesses anomalously high ferromagnetic characteristics.

This paper presents scientific and experimental data for low-firing hydraulic binders: hydraulic lime and Roman cement based on local mineral raw materials. The binders were prepared by firing representative samples of carbonate–clay magnesian raw materials from Tatarstan. Using X-ray diffraction, we identified the firing products, including a hydraulically active phase, and determined the structural characteristics of its minerals. The compositions of the binders were determined as functions of firing conditions. We examined the influence of the firing temperature and duration of magnesian raw materials in the preparation of binders on MgO activity and demonstrated for the first time the possibility of ensuring an active state of the MgO resulting from firing (up to 21%) and suppressing its negative effect on Roman cement and hydraulic lime hardening processes.

This paper considers the evaporation process in an evaporator–connecting tube–condenser system under conditions such that the evaporation rate is determined by the evaporation and condensation mechanisms and the hydraulic resistances of the evaporation and condensation compartments and connecting tube. We present a mathematical model and numerical simulation results that demonstrate quantitative patterns of a steady-state evaporation process in a closed evaporation–condensation system. For a particular example of selenium vacuum distillation, we have determined the evaporation coefficient of selenium from experimental data on the temperature dependences of the selenium evaporation rate and saturated vapor pressure.

This paper presents a study of the electrodynamic properties of polymer-matrix composite materials containing a filler in the form of multiwalled carbon nanotubes. We have examined the effect of filler alignment in the composites on their interaction with electromagnetic radiation. The composite materials have an anisotropic electrical conductivity, dielectric permittivity, and electromagnetic radiation attenuation coefficient because an applied electric field produces a preferential filler alignment direction.