Binary nitrate (NaNO3-KNO3)/expanded graphite (EG)/ nano-SiO2 composite heat storage materials, used as high-temperature thermal energy storage materials, were prepared by mechanical dispersion method, and the effects of EG and nano-SiO2 additives on thermal properties of compound salts were investigated by SEM (scanning electron microscope), STA (Simultaneous Thermal Analysis) and LFA (Laser Flash Apparatus). The results showed that the specific heat capacity of the composites increased first and then decreased with the increase of EG mass fraction. When the mass fraction of EG was 15%, the specific heat of the composite was 3.92J/(g·K), which was 2.58 times higher than that of pure binary nitrate, and the thermal conductivity of the composite was 8.46W/(m·K), which was 16.2 times higher than that of pure binary nitrate. Compared with NaNO3-KNO3/EG(15%wt) composite, the average specific heat capacity and thermal conductivity of the NaNO3-KNO3/EG(15%wt)/nano-SiO2 composite material increased by 15.98% and 42.91% respectively. The preparation process was simple, and the NaNO3- KNO3/EG/nano-SiO2 composite had a broad application prospect in high-temperature energy storage system.
Keywords binary nitrate, nanoparticles, expanded graphite, specific heat, thermal conductivity