Electrical conductivity and viscosity of cryolite electrolytes for solar grade silicon(Si-SoG) electrowinning

Electrical conductivity of molten binary and ternary mixtures based on the system NaF-AlF3-SiO2 was investigated by means of a tube–cell （made of pyrolytic boron nitride） with stationary electrodes. Viscosity of the binary system Na3AlF6-SiO2 was measured by computerized torsion pendulum method. It was found that conductivity and viscosity varied linearly with temperature in all investigated mixtures. Obtained content dependence of electrical conductivity （isotherms） was divided into two parts. First, one represented the content region up to 10%（mole fraction） of SiO2;second, the region was with a higher content of SiO2 （from 10%up to 40%）. While the conductivity considerably decreased with content of SiO2 in the second part; it surprisingly rose in the low content range. A small addition of SiO2 to the molten cryolite （up to 10%） could slightly increase viscosity, but had no influence on the slope of this dependence since it is responsible for a glassy-networks formation in the melt. Further addition of SiO2 to the molten cryolite had a huge effect on the viscosity.

Structural correlation and chemistry of molten NaF-ScF_(3) with dissolved metal aluminium:TG/DTA,XRD,NMR and molecular dynamics simulations

For the first time,the mechanism of metal aluminum dissolution in NaF-ScF_(3) eutectic melts and the chemical interaction between the constituents of this mixture have been thoroughly studied by a combination of differential thermal analysis(DTA),high temperature and solid-state nuclear magnetic resonance(NMR),and X-ray diffraction(XRD) coupled with the molecular dynamic simulations.The formation of an insoluble Al_(3)Sc alloy in molten(NaF-ScF_(3))_(eut)system was proven,and the chemical mechanism of this aluminothermic Al_(3)Sc alloy production was elucidated.Corresponding ex situ examinations bring to light the formation of NaScF_4 and solid solution of Na_(3)(Al,Sc)F_(6) in cooled bath.The molecular dynamics calculations of the bath allow us to construct the structural model and to predict viscosity,density and electrical conductivity of the reagent melt to help to optimize the conditions of the alloy synthesis.

Electrochemistry of samarium in lithium-beryllium fluoride salt mixture

The electrochemical behaviour of samarium was investigated in LiF-BeF2 system on an inert （Mo） electrode by cyclic voltammetry and chronopotentiometry at 804, 833, 847 and 872 K. Redox process Sm3＋＋e–→Sm2＋ was recognized and analysed. Cyclic voltammetry data suggested that at potential sweep rates lower than 0.25 V/s, the reduction was limited by the diffusion of Sm3＋ ions. It was not possible to observe reduction process of Sm2＋＋2e–→Sm0 due to insufficient electrochemical stability of LiF-BeF2. Diffusion coefficients of Sm3＋ ions in LiF-BeF2 were calculated from voltammetric and chronopotentiometric data in the temperature range 804–872 K. Diffusion coefficient values obeyed Arrhenius law. Activation energy was calculated to be 102.5 kJ/mol.