Capacitance measurement of molten calcium silicate under shear stress field

The effect of shear stress on the crystallization behavior of molten 50CaO-50SiO₂ (mol%) slag was investigated by in-situ measurements of its electrical capacitance in wide temperature range including supercooled region. It is well known that the electrical capacitance of liquids should be generally much higher than that of solids because of the differences in their respective polarization mechanisms. The difference was employed as a sensitive indicator of the crystallization of molten silicates in an experimental furnace equipped with an electricalcapacitance measurement system. The system comprised a Pt-based alloy crucible and a rotating rod that allow us to evaluate the effect of shear stress, both connected to a capacitance meter (LCR meter). As expected, at a particular temperature, the electrical capacitance of the molten calcium silicate abruptly decreased by roughly three orders of magnitude, which clearly indicated crystallization confirmed by corresponding microstructural analyses. It was also found that, for the rotating-rod measurements (with shear stress), the temperatures at which the capacitance abruptly dropped were higher than that without the shear stress. This suggests that the agitation effect by the rotating-rod accelerates the crystallization of molten calcium silicate.