Correlation Between Viscosity and Electrical Conductivity of Aluminosilicate Melts
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NTRODUCTION
BOTH viscosity and electrical conductivity of aluminosilicate melts are of great importance to the hightemperature pyrometallurgy process. Viscosity greatly affects the foaming performance of slag, separation efficiency of metal and slag, and lubrication effect during the continuous-casting process. The electrical conductivity plays a prominent role on the heating of melts in electric smelting furnaces. Furthermore, both properties are very sensitive to the structures of aluminosilicate melts. Consequently, there are considerable demands for reliable viscosity and electrical conductivity data. However, because of the difficulty of high-temperature operations, obtaining data only via experimental measurements is time consuming and cannot fulfill the increasing requirements of data. Therefore, the modeling method is considered to be more efficient. Many models have been developed for viscosity,[1–4] and some simple formulas were also proposed to correlate conductivity with temperature and composition.[5,6] If the relation between viscosity and electrical conductivity can be obtained, the data sources will be greatly enlarged. Mills[7] pointed out that both viscosity and electrical conductivity can be well correlated by the number of nonbridging oxygen per tetrahedrally coordinated cation (NBO/T) or optical basicity, which indicates a relation may exist between them. Walden’s rule is the first quantitative expression for viscosity and GUO-HUA ZHANG, Lecturer, and KUO-CHIH CHOU, Professor, are with State Key Laboratory of Advanced Metallurgy and School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, P.R. China. Contact e-mail: [email protected] Manuscript submitted December 28, 2011. Article published online May 9, 2012. METALLURGICAL AND MATERIALS TRANSACTIONS B
electrical conductivity, which shows that the product of them for ionic liquid is a constant that is related to the physical properties of ions.[8] Thereby, if the Arrhenius expressions are used to describe the relations between the two properties and temperature, then the activation energies of them should be equivalent to each other. However, Walden’s rule cannot be fulfilled in the oxide melt because of the obvious differences between the activation energies of viscosity and electrical conductivity.[9] The conclusion offered by Kato and Minowa[10] can only be applied to a few systems within narrow composition ranges. In our previous papers,[11,12] the linear relations have been obtained between the logarithm of viscosity and the logarithm of electrical conductivity in MO-SiO2 (M = Mg, Ca, Sr, Ba), M2O-SiO2 (M = Li, Na, K), and CaO-(MgO)-Al2O3-SiO2 melts. However, some problems are still unresolved, as follows: (a) There is no systematic analysis for the influences of different factors on viscosity and electrical conductivity, (b) The influences of FeO and MnO on the relation between viscosity and conductivity are still unknown, although these two components are important for metallurgical slags. (c) It was
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