Vol 2016, No 8 (2016)

Adiabatic compressibility β of an immiscible 0.5NaCl + 0.5AgI liquid mixture in the immiscibility range is studied experimentally and theoretically using the model of charged hard spheres. The compressibility is calculated by the relationship β = 1/u²ρ studied using sound velocity u measured by a pulse method and density ρ determined by hydrostatic weighing. It is shown that the compressibility of the upper phase decreases and that of the lower phase increases when the temperature increases because of the superposition of the effects of the thermal motion of ions and the phase compositions. The temperature dependence of the difference between the compressibilities of the equilibrium phases is described using the empirical equation Δβ = (T_c–T)^0.442, which is close to the mean-field theory description. The results of the model calculations adequately reproduce the experimentally observed temperature dependence of the compressibility of the coexisting phases. However, the theoretically predicted critical exponent (1/2) differs from the experimentally determined exponent by 13%. These results are discussed in terms of the nature of chemical bond in silver iodide.

A molecular dynamics simulation of molten LiF–NaBr and LiF–KBr mixtures at a temperature of 1280 K is performed over a wide concentration range to calculate the self-diffusion coefficients of the ions forming these mutual mixtures. It is found that the concentration dependence of the self-diffusion coefficient of the lithium cation in LiF–NaBr has an extremal character with a minimum, the position of which corresponds to the equimolar composition of the mixture.

The influence of the melt velocity in commercial electrolysis cells on the overheating is discussed

The behavior of uranium(III) and (IV) ions in the melts based on the eutectic mixture of lithium, potassium, and cesium chlorides has been studied using cyclic voltammetry in the range of 573–1073 K. The red-ox potentials of uranium have been determined and formal standard E_U(III)/U(IV)* red-ox potentials have been calculated.

The joint mechanical activation of chemically interacting iron and titanium has been studied by X-ray diffraction and atomic force microscopy. It is shown that chemically interacting metals Fe and Ti do not form any intermetallic compounds or solid solutions upon intense mechanical activation in a high-energy planetary mill. The products of mechanical activation are Fe/Ti mechanocomposites, in which titanium is distributed over the iron grain surface. An increase in the mechanical activation time leads to the agglomeration of powders and the formation of particles with a wide size range (5–25 μm). The iron crystallite sizes and the level of microstresses are reduced, indicating a decrease in the particle strength.

The topological structure of the quaternary Na⁺, K⁺//F^–, Br^–, NO₃⁻ system is studied using a computer-assisted research system. A tree of phases is constructed, and the eutectic characteristics of the secant triangle NaNO₃–KBr–NaF, (equiv. %) 84.6 NaNO₃–9.1 KBr–6.3 NaF, at 255.3°C are determined.

The electrochemical behavior of the tantalum mono-, di-, and trioxofluoride complexes in the equimolar NaCl–KCl melt is studied. The trioxofluoride TaO₃F^2– complexes are shown to discharge at the potentials that are more negative than those of alkali metal cations; that is, they are electrochemically inactive against the background of the equimolar mixture of sodium and potassium chlorides.

The correlation between the sequence of formation of intermetallic compounds and the nature of interphase interactions in the course of aluminothermic coreduction of titanium, nickel, and molybdenum from their oxides is analyzed.

A phase-field model is proposed for the solidification and melting of a binary concentrated solution (melt). The method of extended irreversible thermodynamics is used to derive thermodynamically consistent equations and to take into account low and high phase transformation rates. The Hillert parallel construction is applied to determine the driving forces of the solidification or melting of a binary system. When thermodynamic equilibrium states are described, the Gibbs potentials are assumed to be known. They are specified from the existing thermodynamic information databases or from experimental data. The results of a numerical investigation of the proposed model are presented.