Thermal conductivity measurements and prediction for R2O-CaO- SiO2 (R=Li, Na, K) slags

Abstract

Thermal conductivities of Li2O-CaO-SiO2, K 2O-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 (TL), irrespective of the (%R2O)/(%CaO) ratio. Furthermore, plotting the thermal conductivities against T/TL (temperature normalised by TL) shows that the thermal conductivities for the melts are not dependent upon the (%R 2O)/(%CaO) ratio within experimental scatter as long as the SiO 2 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.