Dominant factors of thermal conduction in alkali silicate glasses and melts: A molecular dynamics study

Abstract As representative compositions of the mold flux used in the continuous casting of steel, the temperature and composition dependence of the thermal conductivity of alkali silicate glasses and melts was investigated in the range of 300–1700 K using molecular dynamics (MD) simulations. MD simulations can exclude disturbances such as radiation, convection, and impurities, and extract only the effect of phonons on the thermal conduction. Thermal conductivity determined by the laser flash (LF) method was reported to be three times higher than that obtained by the unsteady hot wire (HW) method in the high‐temperature range of 1250–1550 K for 33.3Na 2 O–66.7SiO 2 (mol%). This study shows that (1) the thermal conductivity estimated by MD simulations was closer to the experimental value of the LF method than those of the HW method above 1200 K, which suggests that the LF method is reliable and that the effect of radiation on the thermal conductivity is not significant. (2) The decrease in the thermal conductivity measured by the LF method in the range of 1250–1550 K was attributed to the decrease in the bulk modulus of the 33.3Na 2 O–66.7SiO 2 melt. (3) In a series of Na 2 O–SiO 2 melts, the sound velocity calculated by MD decreased with increasing Na 2 O content, which is consistent with Shiraishi's ultrasonic wave measurements.