Effect of Applied Voltage on Melting and Wetting Behaviors of CaO-SiO2-MgO-Al2O3 slag on Alumina Substrate

The effect of applied voltage from 0 to 20 V on the melting and wetting behaviors of CaO-SiO₂-MgO-Al₂O₃ slag on single crystal alumina substrate was investigated using the sessile drop method. The spreading and shrinking phenomena of slag drop on conductive single crystal substrate were also observed online at 1561 °C by applying ±20 V voltages. The interface and reaction products were examined by SEM-EDS technique. It is found that the applied voltage has no obvious effect on the melting of the slag. Changes in apparent contact angle and spreading diameter were closely related to the magnitude and polarity of the applied voltage. Under experimental conditions, when applied voltages are 0, + 2, +5, + 20 and ±20 V, the final contact angles at 1561 °C were respectively 1.1 °, 3.5 °, 9.2 °, 14.4 ° and 1.5 °, and the final dimensionless spreading diameters of the last four applied voltages are respectively 1.94, 1.52, 1.35 and 2.21. Compared to the case without applied voltage, positive and negative voltages of 20 V can cause different results on the contact angle and spreading diameter of the molten slag on the substrate, which is considered to be mainly attributed to the effect that the applied voltage changes the interfacial tension between the molten slag and the substrate. The higher the applied positive voltage the greater the effect. Moreover, it is also found that high applied positive voltage significantly changes the distribution and the size of the particle phases with high melting point such as MgO⋅Al₂O₃ (MA) in the molten slag.

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