Vol 42, No 6 (2016)

It has been established that the process of stabilization of the boron oxide melt in the temperature range 300–340°С is accompanied by universal changes in the intensity of the polarized V_v component of light scattering characterized with the formation of a minimum. It has been demonstrated that the above feature does not depend on the direction of the intensity approaching to the stationary state for the selected temperature; i.e., it is observed in the process of intensity relaxation from both high and low temperatures. Upon attainment of the minimal values, the increase of the V_v intensity with the stabilization time was found to be satisfactorily described by the empirical dependence of the exponential type. The characteristic times of intensity changes calculated in accordance with the respective equation significantly exceed the times of structural relaxation and increase along with the temperature decrease in accordance with the exponential dependence. It has been established that the characteristic times of intensity changes as its values approach the stationary one from a higher temperature are larger than when approaching from a lower temperature. It has been shown that under these conditions, changes in the intensity of the depolarized H_v component are characterized with the formation of a maximum registered for both modes (sample cooling and heating). It has been revealed that the increase of the H_v intensity in the maximum does not exceed 10% of its regular value, which allows relating the formation of a minimum of the V_v component to the decrease of the isotropic light scattering intensity.

Glass surface properties were investigated after air, nitrogen, oxygen and argon plasmas treatment. The samples were treated by low pressure plasma for 30 s with the gas flow 22 sccm. After modification kinetics of water spreading was measured. Surface topography was determined using optical profilometry, scanning electron microscopy and X-ray photoelectron spectroscopy. It was found that using all types of gases plasma treatment leads to decrease of the surface roughness. The kinetics of water spreading depends on gases type used for glass plates modification. Analyzing the photoelectron spectra the increase of oxygen amount on the surface was observed. For the increase of wettability and adhesive properties of plasma treated glass, the introduction of new polar functional groups on the surface has greater influence than changing the surface roughness.

The characteristics (composition of the quenched samples, ingot, and evaporation products) are studied of the melt of the corium–high alumina cement system in a weight ratio of 1: 1. In the quenched samples of the melt and ingot, signs of phase separation in the molten state are found. Below a temperature of 2100°C above the melt, aerosol particles with trimodal size distribution are formed; however, above this temperature, the nature of the granulometry of aerosols is bimodal. Moreover, the formation rate of aerosols increases dramatically. The form of aerosol particles under all the experimental conditions was spherical.

Effects of ZnO–B₂O₃ (ZB) addition on the densification, phase evolution and microwaves dielectric properties of Ba₄Sm_9.33Ti₁₈O₅₄ (BST) ceramics for low-temperature fired applications have been investigated. The sintering temperature of BST ceramics can be effectively lowered to about 1000°C with introduction of ZB. Tungsten bronze like single phase is observed in the BST ceramics with 0.5 and 1.0% ZB. However, Sm₂Ti₂O₇ secondary phase appears when ZB addition reaches 2%, and Sm₂Ti₂O₇ phase gradually increases with the increase ZB addition. Microwave dielectric properties of the present ceramics are strongly dependent on phase constitution and density. Optimal microwave dielectric properties of ε = 63.4, Qf = 2830 GHz, τ_f =–8.8 ppm/°C is obtained for BST ceramics with 1% ZB addition.

The crystal structures of 197 lithium–silicate compounds have been analyzed using the method of crystal chemistry analysis (TOPOS software package). The compounds whose structures are characterized with a combination of high values of such parameters as the channel radius, stability, gravimetric capacity, and capacity per volume unit have been revealed: LiFeSiO₄ (R3̄), Li₄Fe₂Si₃O₁₀ (C2/c), Li₂FeSiO₄ (Pc2₁n), and Li₂FeSiO₄ (C222₁). It has been demonstrated that lithium–iron silicates of the monoclinic syngony have high values of the capacity per volume unit, as compared to those of the rhombic syngony. The structural stability of the Li₂FeSiO₄ (Pc2₁n) framework has been corroborated using the method of computer simulation within the scopes of the electron density functional theory. The obtained information could facilitate creation of novel cathode materials of high capacity and specific accumulated energy.

Hybrid dispersion systems based on cellulose nanocrystals (CNC) and aluminum oxide have been prepared, and the influence of the ζ-potential on their stability has been studied for a wide range of the concentration ratio of the components. Their influence on the morphology and properties of the hybrid particles is evaluated. It is established that one can obtain stable colloidal dispersions with both negatively and positively charged particles or hybrid systems with a neutralized surface charge by controlling the surface potential.

An Al₂O₃–Fe₂O₃ dispersed oxide system has been obtained electrochemically in aqueous solutions containing chloride ions with the subsequent thermal treatment. The phase and elemental composition and structural characteristics of the samples have been studied using X-ray phase analysis, Mössbauer spectroscopy, and scanning electron microscopy. The effect of the electrolysis mode and thermal treatment on the characteristics of the samples which were synthesized is shown. It is found that a high-temperature treatment (1100°C) facilitates the formation of a complex oxide material whose phase composition is a combination of the α-Al₂O₃ (corundum) and α-Fe₂O₃ (hematite) crystalline phases and whose particles have nanometer sizes.

The optimal conditions of synthesis of one of the most promising precursors of biological apatites— octacalcium phosphate (OCP)—have been determined. The OCP synthesis was carried out by two main methods: hydrolysis of brushite and precipitation from an aqueous solution. The samples’ phase composition, morphology, and thermal stability, as well as their bioresorbability in electrolytes of different acidity, have been investigated.

Nanoparticles with different morphology have been obtained by hydrothermal method in the system MgO–SiO₂–TiO₂–H₂O. It has been found that in the investigated temperature–time interval the formation of nanotubes of hydrosilicate with the structure of chrysotile with a small amount of impurity phases predominantly takes place.

Glasses with the (8–x)Na₂O · xFe₂O₃ ∙ 22B₂O₃ ∙ 70SiO₂ compositions, where the Fe₂O₃ content varies from 2 to 6 mol %, which were heat-treated at the temperatures of 550 and 700°С for 144 and 2 h, respectively, have been studied by dilatometry, electron microscopy, and X-ray powder diffractometry. It has been shown that, with an increase in the total concentration of Fe₂O₃ in the glass, there is a trend to the transition from an interconnected to a droplet-matrix phase-separated structure. The crystal line phases of Fe₃O₄, FeSiO₃, and β-Fe₂O₃ are formed depending on composition, while the latter is observed only in the glass with the equivalent contents of Na₂O and Fe₂O₃. There is a minimum on the glass transition temperature dependence of the composition at equimolar (4 mol %) contents of Na₂O and Fe₂O₃.

Nafion-115 membrane hydration has been carried out by the treatment with hydrochloric acid solutions of various concentrations (0.025–3 M). The structure and electrophysical properties of the original untreated Nafion membrane and hydrated membranes have been studied. The current–voltage characteristics of the membrane electrode assembly of a fuel cell with the hydrated membrane have been analyzed.