Zuzana Vasková

Density, Viscosity and Electrical Conductivity of the Molten Cryolite Electrolytes (Na 3 AlF 6 –SiO 2 ) for Solar Grade Silicon (Si–SoG) Electrowinning

Density, viscosity and electrical conductivity of the molten system Na 3AlF 6–SiO 2 have been investigated in the concentration range up to 50 mole % of SiO 2. Density was measured by means of a computerized Archimedean method, viscosity of the melt by computerized torsion pendulum method and the electrical conductivity by means of the tube–cell (pyrolytic boron nitride) with stationary electrodes. It was found that the density, viscosity and conductivity vary linearly with the temperature in all investigated mixtures. On the basis of the density data, the molar volume of the melts and the partial molar volume have been calculated.

(3,5-Dinitro­benzoato-κO)bis­[(2-pyrid­yl)methanol-κ2N,O]copper(II) 3,5-dinitro­benzoate

Department of Inorganic Chemistry, SlovakUniversity of Technology, Radlinske´ho 9,SK-812 37 Bratislava, Slovak RepublicCorrespondence e-mail:jaroslava.maroszova@stuba.skKey indicatorsSingle-crystal X-ray studyT = 293 KMean (C–C) = 0.004 A˚Disorder in main residueR factor = 0.042wR factor = 0.111Data-to-parameter ratio = 15.1For details of how these key indicators wereautomatically derived from the article, seehttp://journals.iucr.org/e.

Critical evaluation of partial molar volumes and excess partial molar volumes of molten fluoride melts

Different procedures of evaluation of partial molar volume and excess partial molar volume have been applied for three binary or quasi-binary molten fluoride systems: KF–K2TaF7, K2ZrF6–K2TaF7 and (LiF–NaF–KF)eut–K2ZrF6. In the first procedure partial molar volume is calculated based on mathematical fitting of molar volume, while in the second procedure partial molar volume is calculated based on mathematical fitting of excess molar volume. It was shown that both procedures are in principle consistent. However, some inconsistencies on values of partial molar volume can occur when local extremes are observed on concentration dependence of molar volume. In such situation, proper selection of mathematical functions is essential which requires relatively high density of experimental data. Moreover, when data on only restricted concentration range are available, only procedure of molar volume fitting is applicable for calculation of partial molar volume.

Interaction of metallic zirconium and its alloys Zry-2 and E110 with molten eutectic salt of LiF—NaF—KF containing zirconium fluoride components

The interactions of selected zirconium alloys used as special construction materials (Zr-pure, Zry-2, E-110) with the molten system of (LiF—NaF—KF)(eut.) with additions of K2ZrF6 or Na7Zr6F31 were studied. Corrosion losses of pure zirconium decrease sharply with 5 mole% addition of K2ZrF6 to (LiF—NaF—KF)(eut.). The presence of alloying additives (Sn, Nb) has a positive influence on corrosion resistance in the eutectic mixture — up to 60% increase in corrosion resistance in comparison with pure zirconium. The mass losses of pure zirconium indicate an increasing corrosion attack with increasing Na7Zr6F31 content in (LiF—NaF—KF)(eut.) mixtures.

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

Abstract Electrical conductivity of molten binary and ternary mixtures based on the system NaF–AlF 3 –SiO 2 was investigated by means of a tube–cell (made of pyrolytic boron nitride) with stationary electrodes. Viscosity of the binary system Na 3 AlF 6 –SiO 2 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 SiO 2 ; second, the region was with a higher content of SiO 2 (from 10% up to 40%). While the conductivity considerably decreased with content of SiO 2 in the second part; it surprisingly rose in the low content range. A small addition of SiO 2 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 SiO 2 to the molten cryolite had a huge effect on the viscosity.