The National University of Science and Technology “MISiS”

V. I. Moskvitin, Professor, (499) 236-65-79

A. P. Lysenko, Assistant Professor of Non-ferrous Metals and Gold Department

The researchers have repeatedly suggested that cryolitealumina melts structure should not be uniformed at both low and high alumina contents. In this article the researchers present the measurement results of the most structurally sensitive chemical-physical properties observed in cryolitealumina melts, their electroconductivity and viscosity. The results of polarization measurements at low alumina content are also attached. Melt resistivity was determined with the aid of a 4-electrode cell by means of applying to it a stabilized alternative sinusoidal current. Density measurements were carried out by using an amplitude — amplitude version of a vibration method. The measurements of electrode potentials were made by using a commutative method in respect to the electrode of comparison. The analysis of dependencies obtained and polarization measurements by using aluminium oxyfluoride for the purpose of comparison made it possible to show that at low alumina contents in cryolite the process of dissociation runs with O^2- and AIO⁺. The first section of polarization curves may be associated with surface saturation of a platinum anode with O^2– ions absorption. The second section of the polarization curves is responsible for oxygen ions discharge reactions. As alumina content increases in the melt the formation of polymer clusters with brunching bindings may occur. It decreases the activity of simple oxygen-ions and of the main current carriers – sodium ions, which consequently leads to electroconductivity decrease. Meanwhile the viscosity of the melt starts growing. Therefore the melts under discussion show a tendency to overcooling during crystallization, which is the case on practice.

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