The thermal physical properties and stability of the eutectic composition in a Na2CO3–NaCl binary system

• The composition and phases of molten Na2CO3–NaCl were stability at high temperature.
• The thermal physical properties of mixture molten salt were measured.
• The mixture molten salt showed excellent thermal-cycling property.
• The appropriate operation temperature of eutectic Na2CO3–NaCl binary molten salts should employ below 1073 K.

The thermal physical properties of the eutectic Na2CO3–NaCl molten salts were investigated. The melting point of the binary salt mixture was 909 K, the density of the molten salts decreased linearly with increased temperature, and the viscosity has an exponential relationship with temperature. The vapor pressure increases significantly as the temperature is increased. The thermal stability of the eutectic mixture was measured by weight loss. The results indicate that the degree of volatility has a linear relationship with time. The heating and cooling curves of the molten salt were almost invariant during the cycle times. The titration and XRD studies demonstrate that the composition and phase of the molten salt were unchanged after high-temperature treatment. The morphology and content of the solid eutectic salts were observed by SEM-BSE and EDX. From this study, it can be concluded that the thermo-physical properties and thermal stability were excellent below 1073 K.