Vol 2017, No 2 (2017)

The thermal expansion coefficients of molten halides have been analyzed. This parameter has been found to be a constant for all halides except for lithium halides. Since the thermal expansion coefficient and the molar heat capacity of halides change symbatically, the ratio of the molar heat capacity to the thermal expansion coefficient is also a constant.

The liquidus temperatures of the BaO–BaCl₂–MCl systems (with M = alkali metal) are determined by thermal analysis. The caloric effects observed during melting of the barium-containing chloride eutectic with barium oxide additions are studied. A chemical mechanism of barium oxide dissolution in the melts is confirmed. X-ray diffraction patterns taken for the melt solidified after experiment indicate the presence of barium oxychloride Ba₄OCl₆ in the solid phase. It is shown that the significant increase in the liquidus temperature in adding the barium oxide to barium-containing chloride molten mixtures is related to substantial changes in their composition and structure.

The corrosion of 12Kh17 steel in the melts of alkali metal carbonates containing additions of various chemical types is studied using anodic potentiostatic polarization. The morphology of the 12Kh17 steel surface is analyzed by electron-probe microanalysis. The introduction of corrosion passivators and activators affects the mechanism of local corrosion damages. The corrosion of the steel proceeds according to an electrochemical mechanism. Carbonate anions serve as oxidizers of the steel along with oxygen dissolved in the melt. Treatment of a corrosive medium can be used to protect metallic constructions against corrosion in high-temperature salt electrolytes. Combined introduction of corrosion activators and passivators in a salt phase makes it possible to form protective layers with a high corrosion resistance.

The influence of strongly polarizing cations Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺ on the charge transfer kinetics of the redox couple Ti(IV)/Ti(III) is studied. The standard rate constants of charge transfer (k_s) for the Ti(IV)/Ti(III) redox couple in the (NaCl–KCl)_eq–NaF (10 wt %)–K₂TiF₆ melt upon the addition of the strongly polarizing cations into the starting melt are determined. The dependence of the charge transfer rate constants on the ionic potential of the cations is established. The activation energies of the charge transfer process are calculated for the fluoride complexes of the Ti(IV)/Ti(III) redox couple with the outer-sphere cations Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺.

The application of a number of algebraic expressions for describing the concentration dependences of the thermodynamic functions in liquid binary metallic systems with negative deviations from ideal behavior is considered.

The directional solidification of a ternary system with an extended phase transition region is theoretically studied. A mathematical model is developed to describe quasi-stationary solidification, and its analytical solution is constructed with allowance for a nonlinear liquidus line equation. A deviation of the liquidus equation from a linear function is shown to result in a substantial change in the solidification parameters.

A general scheme is used to consider the initial stages of electrocrystallization under potentiodynamic and galvanostatic conditions. Proposed theoretical models are shown to agree well with the experimental results obtained during the electrodeposition of silver crystals on an iridium microelectrode from nitrate melt containing an excess background electrolyte.

Cyclic voltammetry is used to study the formation of tetragonal oxide tungsten bronze of the composition K_xNa_yWO₃ on a Pt(110) substrate during electrodeposition from a K₂WO₄–Na₂WO₄–WO₃ melt. The potential ranges in which cathode products of various compositions and morphologies form are found. K_xNa_(0.66–x)WO₃ crystals are shown to form according to the nucleation/growth mechanism. A general scheme is proposed and used to write equations for cathode reactions.