Thermal Conductivity Measurements and Prediction for R₂O-CaO-SiO₂ (R=Li, Na, K) Slags

Abstract

Thermal conductivities of Li₂O-CaO-SiO₂, K₂O-CaO-SiO₂ and 37CaO-63SiO₂ slags have been determined using the non-stationary hot wire method over a wide temperature range between room temperature and 1823K to propose a prediction equation for thermal conductivities of R₂O-CaO-SiO₂ slag melts, where R represents Li, Na and K. The temperature coefficients of thermal conductivities for all the samples were negative in the liquid state. The thermal conductivities of slags having the same SiO₂ concentration, i.e., the same NBO/T (number of non-briging oxygens per tetrahedrally coordinated atom), decreased by replacement of CaO with R₂O but took almost the same value at their liquidus temperatures (T_L), irrespective of the (%R₂O)/(%CaO) ratio. Furthermore, plotting the thermal conductivities against T/T_L (temperature normalised by T_L) shows that the thermal conductivities for the melts are not dependent upon the (%R₂O)/(%CaO) ratio within experimental scatter as long as the SiO₂ concentration is kept constant. On the basis of this finding, an empirical prediction equation has been proposed for thermal conductivities of R₂O-CaO-SiO₂ melts.