Thermal conductivity of Na2O–B2O3–SiO2 melts

Abstract

ABSTRACT Borosilicate glasses are candidate materials for the immobilization of high-level radioactive waste. The values of thermal conductivity of different borosilicate melts are thus indispensable information when optimizing the temperature distribution in a glass melting furnace. In this study, the thermal effusivity of Na2O–B2O3–SiO2 melts was measured using a front heating–front detection laser-flash method. The thermal conductivity, which can be obtained by combining the measured thermal effusivity with the specific heat capacity and density, was calculated using the least-squares method; the values for the Na2O–B2O3–SiO2 melts either slightly decreased linearly with increasing temperature or remained almost constant over the investigated temperature range. The values of thermal conductivity of the Na2O–B2O3–SiO2 melts were higher than those of B2O3–SiO2 melts and lower than those of CaO–B2O3–SiO2 melts. Furthermore, the thermal conductivity of the Na2O–B2O3–SiO2 melts was compared with those of the B2O3–SiO2 and CaO–B2O3–SiO2 samples.