Comprehensive thermal properties of molten salt nanocomposite materials base on mixed nitrate salts with SiO2/TiO2 nanoparticles for thermal energy storage

The purpose of this investigation is to find and prepare novel heat storage materials to meet the requirement of Concentrating Solar Power (CSP) system. This paper focuses on the formulation, fabrication and characterization of a novel molten salt nanocomposite for high-temperature heat energy storage. The molten salt nanocomposite is based on eutectic quaternary salt, and two different concentrations of SiO2 and TiO2 nanoparticles are added to improve its specific heat capacity and thermal conductivity by microwave method. Concerning the material characterization, a suite of techniques was used, including simultaneous thermal analysis (STA) and laser flash analysis (LFA). The consequences demonstrate that the melting point and latent heat of molten salt nano composites can be reduced by adding two different concentrations of nanoparticles at the same time. The specific heat is 28.1% higher than that of the pure quaternary salt, and 6.3% and 9.8% higher than that of adding SiO2 and TiO2 nanoparticles separately when adding 0.1 wt% SiO2 and 0.9 wt% TiO2 nanoparticles to the quaternary nitrate. Compared with pure quaternary salt, the thermal conductivity of the molten salt nanocomposites increased by 53.7%, which was 16.8% and 6.3% higher than that of adding SiO2 and TiO2 nanoparticles separately. Upon inspection with scanning electron microscopy, a high-density nanostructure and heat transfer channel were observed, which appear to be the reason for the enhancement of specific heat and thermal conductivity of the material. Finally, the molten salt nanocomposite has a broad application prospects in high temperature thermal storage system.