Vol 54, No 9 (2018)

The equilibrium potentials of Bi in a KCl–PbCl₂–BiCl₃ melt were measured by the EMF method at different temperatures and bismuth chloride contents. Empirical equations of isotherms and polytherms of the equilibrium potentials of bismuth were obtained. The conventional standard potentials of Bi in a molten mixture of potassium and lead chlorides were calculated. The changes in the Gibbs energy during the formation of bismuth trichloride from the elements in the melt were calculated. The coefficients of metal separation from alloys were estimated. The results indicate that it is promising to develop a technology for electrolytic processing of secondary raw materials for separating lead and bismuth in chloride melts.

Quasibinary phase diagrams of the system “low-melting cryolite–Sc₂O₃” the potential media for synthesizing alloyed alloys Al–Sc are plotted by the method of thermal analysis. The phase diagrams of (KF–NaF–AlF₃)–Sc₂O₃ with different content of NaF and the cryolite ratio (CR) 1.3 and 1.5 are the diagrams with simple eutectics. The liquidus temperature of the (KF–AlF₃)–Sc₂O₃ system increases with the increase in the Sc₂O₃ concentration due to the formation of a high-melting compound: potassium hexafluoroscandiate К₃ScF₆. The solubility of Sc₂O₃ in low-melting cryolite melts KF–NaF–AlF₃ increases with the increase in temperature and CR. In contrast Al₂O₃, the solubility of Sc₂O₃ in melts containing KF–AlF₃ with CR = 1.3–1.5 is much lower than in cryolite melts containing NaF. The conductivity of low-melting cryolite melts measured by the method of impedance spectroscopy decreases in proportion to the Sc₂O₃ concentration in the similar way as in salt melts containing Al₂O₃. Based on the experimental data obtained, the compositions of low-melting cryolite melts are proposed for the synthesis of doped Al–Sc alloys.

The interaction of the monel alloy and its corrosion resistance in a melt of alkali metal carbonates in an oxidizing atmosphere was studied. The selectivity of alloy dissolution and modification of the electrode surface after storage at a constant anode potential were analyzed. The generation and development of local corrosion defects (pit corrosion, intercrystallite corrosion, corrosion cracking) on monel alloy (70% nickel, 28% copper), copper, and nickel electrodes in the molten eutectic of lithium, sodium, and potassium carbonates at a working temperature of 773 K were studied. The anode polarization was accompanied by a change in the state of the electrode surface.

Lithium metazirconate Li₂ZrO₃ was synthesized by various methods, and its electric conductivity was studied in the range 300–600°C. For the sample obtained by solid-phase synthesis, the temperature dependence of conductivity is linear in the Arrhenius coordinates and coincides with the literature data for Li₂ZrO₃ obtained by the similar procedure. The sample synthesized and sintered in vacuum has higher electric conductivity, but contains a Li₂CO₃ impurity. Possible reasons for the abrupt change in the conductivity of Li₂ZrO₃ at 430–470°C reported in some works were considered.

Potentialities of the method of bilayer thin-film electrolyte electrophoretic deposition onto cathodic substrate are analyzed. Ce_0.8Sm_0.2O_1.9–δ (SDC) nanopowder and BaCe_0.89Gd_0.1Cu_0.01O_3–δ BCGCuO) micropowder are prepared by the methods of laser evaporation–condensation and pyrolysis, respectively. The effect of ultrasonic treatment on the SDC and BCGCuO particle distribution in suspensions and their electrokinetic properties are studied. The using of the ultrasonic treatment combined with centrifugation allowed obtaining an aggregative-stable suspension of the BaCe_0.89Gd_0.1Cu_0.01O_3–δ micron particles in the isopropanol–acetylacetone mixed medium (70/30 v/v) that is characterized by high zeta potential. Ce_0.8Sm_0.2O_1.9–δ and BaCe_0.89Gd_0.1Cu_0.01O_3–δ thin films are obtained at the La₂NiO_{4 +δ} cathode substrate using electrophoretic deposition; microstructure and electric properties of the prepared thin-film structures are studied. The conductivity and electric properties of the bilayer electrolyte were found to be determined by the Ce_0.8Sm_0.2O_1.9–δ film properties. Despite the sintering high temperature, the grain structure of the BaCe_0.89Gd_0.1Cu_0.01O_3–δ film is underdeveloped; this is determined by the micron powder properties.