Search

The electrical conductivity of LiCl–ZrCl4, NaCl–KCl (1:1)–ZrCl4 and KCl–HfCl4 molten mixtures has been studied for the first time as a function of temperature (770–1100 K) and the concentrations of ZrCl4 (0–25 mol%) or HfCl4 (0–30 mol%). A conductometric cell of an original construction has been used. The electrical conductivity of these mixtures ranges from 0.9 to 3.1 S/cm. The increase in the temperature results in the increase in the electrical conductivity, whereas the increase in the ZrCl4 or HfCl4 concentration results in its decrease. The obtained results on the electrical conductivity of MCl–ZrCl4 (M – alkali metals) melts are summarized, taking into account our previous measurements, and discussed on the basis of the available data on the structure of such melts.

The volatilities of the components of the saturated vapors of molten UCl4–NaCl–KCl mixtures containing 2.0, 5.0, 12.2, 25.1, 32.9, and 49.7 mol % UCl4 are measured by a transpiration technique in the temperature range 880–1200 K. The chemical composition of the saturated vapors is determined. The vapor phase is most likely to contain the binary NaUCl5 and KUCl5 compounds, which make a significant contribution to the total vapor pressure over the molten mixtures. The molten mixtures are found to exhibit negative deviations from ideal behavior.

The electrochemical reduction of pelleted heterophase powder Pd-Nd2O3-CeO2 mixtures was studied in molten LiCl-Li2O (1–1.5 wt%) at 650 °C. The influence of the composition of the mixture, as well as electrochemical factors—i.e., the amount of electricity passed and the cathode potential during electrolysis—were considered. It was found that in the presence of metallic palladium, neodymium and cerium oxides are reduced by lithium released at the cathode and form intermetallic compounds of different compositions. At potentials more positive than the formation of a phase based on liquid lithium at 0.5–0.8 V, CePd3 and NdPd3 intermetallic compounds are present in the reduced product. At potentials close to the formation of liquid lithium, a whole spectrum of intermetallic compounds is synthesized: CePd, NdPd, Ce3Pd4, and Nd3Pd4. The mechanisms of formation of palladium alloys with neodymium and cerium are proposed and considered. The degree of the reduction of lanthanide oxides was calculated from the data on the concentration of residual oxygen in the reduced product.

The electrical conductivity of ZnCl2–BeCl2 molten mixtures has been measured for the first time. The measurements are performed over a wide temperature range including supercooling regions. Isotherms of the electrical conductivity of ZnCl2–BeCl2 are found to demonstrate negative deviations from additive magnitudes.

The temperature and composition dependences of the electrical conductivity of ZnCl2-ZrCl4 molten mixtures characterized by high saturated vapor pressures have been measured for the first time.

The dependences of the electrical conductivity of NaCl-KCl-ZrCl4 molten mixtures with a molar ratio NaCl : KCl = 8 : 29 on the temperature (temperature range of 300–540°C) and the ZrCl4 concentration (54.3–75.2 mol %) have been measured for the first time using unique cells.

Reactions of ZrCl4 and HfCl4 with InCl and TlCl accompanied by formation of several solid complex compounds were studied by the Raman spectroscopy method.

The structures of crystalline (over a wide temperature range) and molten rare-earth metal-LnCl3 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy) trichlorides are comprehensively studied by Raman spectroscopy.

The Raman spectra of crystalline (over a wide temperature range) and molten GdCl3 are mea- sured. The hexagonal structure C26h (UClC26h3 type) of crystalline GdCl3 is found to change weakly over the entire temperature range under study. The temperature dependences of the characteristic frequencies change in the premelting range.

The structure of crystalline, molten (from the melting to the critical temperature), and gaseous (at high vapor pressures) gallium trichloride is studied by Raman spectroscopy for the first time.

Solutions of rare-earth metals (REM, Ln) in molten chlorides, including mixtures MCl + LnCl3, where M stands for an alkali metal, are studied by methods of potentiometry, voltammetry, and conductimetry in broad intervals of concentration and temperature. The results that had been obtained give sufficiently comprehensive and reliable enough information concerning the valence state of rare-earth metals, as well as the structure and composition of complex ions that make a substantial impact on the properties of electrolytes. It is demonstrated that the co-existence of ions of rare-earth metals in different oxidation states, which form as a result of possible redox reactions 2Ln3+ + Ln ↔ 3Ln2+, Ln2+ + Ln ↔ 2Ln+, and nM+ + Ln ↔ nM + Lnn+, clearly manifests itself in the thermodynamic and transport properties of molten systems Ln-LnCl3 and Ln-LnCl3-MCl.

The electrical conductivity of molten SnCl2 was measured in a wide temperature range (ΔT=763 K), from 551 K to temperature as high as 1314 K, that is, 391° above the boiling point of the salt. The specific electrical conductance was found to reach its maximum at 1143 K, after that it decreases with the temperature rising.

The density and electrical conductivity of cobalt and nickel dichlorides and their solutions in molten sodium chloride have been measured. The density was measured by a dilatometric method, and the electrical conductivity by an AC technique. The molar volume and equivalent conductance were calculated.

The data about possibility of the interaction between chlorides phosphorus and earth metals in science literature are absent.

The partial pressures of components in saturated vapours of HfCl 4 solutions in molten alkali chlorides and some of their mixtures are determined as a function of temperature (800–1300 K) and concentration (2–33 mol% HfCl 4 ) by dynamic (from 10 to 2 × 10 4 ) and static (from 1.3 × 10 3 to 2.6 × 10 5 Pa) methods. HfCl 4 vaporization enthalpy and entropy, activity coefficients and excess partial thermodynamic functions are calculated from tensimetric observations. The relations of these quantities to temperature and concentration are obtained. Alkali cations and temperature being unchanged. HfCl 4 partial pressure and activity coefficient rise more sharply the smaller is the ionic potential of alkali cations in the series from Li + to Cs + , as HfCl 4 concentration is increased. In dilute solutions ( N HfCl 4 4 activity coefficient reaches its lowest values, positive HfCl 4 vaporaization enthalpy and negative HfCl 4 excess partial enthalpy are the greatest, which is indicative of HfCl 4 complexing in molten alkali chlorides. Alkali chloride partial pressures vary almost in proportion to their mole fractions in melts, with their activity coefficients being close to one. Making use of experimental data on the equilibrium electrode potentials of hafnium in dilute solutions of its di- and tetrachloride in molten alkali chlorides, the decomposition potential of HfCl 4 solutions in these salts and their mixtures is computed as a function of temperature and concentration up to 33 mol% HfCl 4 . Quantitative expressions are derived for its temperature, concentration and alkali cation composition dependences. The relation of Gibbs energy to temperature is found for reaction Hf (s) + 2Cl 2(g) = HfCl 4(g) . Δ H 298 T and S o T of gaseous HfCl 4 being evaluated as a function of temperature at 1000–1200 K.