Preparation and properties of in-situ synthesized nanoparticles in NaNO3-KNO3

Abstract

Nitrate molten salt has been proved promising heat storage materials with good thermophysical properties in concentrating solar power. Increasing specific heat capacity of molten salt can help enhance its thermal storage capacity. Solar salt, a mixed molten salt of 60wt% NaNO3 and 40wt% KNO3, is a widely used heat storage and heat transfer medium in solar thermal power system. In this paper, we adopted the in-suit method to synthesize MgO nanoparticles into solar salt and investigated the effect of nanoparticles on the specific heat capacity of solar salt. The microstructure of the composites was observed by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), spherical and needle-like MgO nanoparticles are synthesized. The diameter of spherical MgO nanoparticles are about 50-200 nm. The length and width of needle-like MgO are 50-200 nm and 5-30 nm respectively. The specific heat capacity, latent heat and phase transition temperature of composites with different contents and different processes were tested by Differential Scanning Calorimetry (DSC). Results show that the specific heat capacity is increased by 118.6% in solid state when adding 14.8wt.% Mg(OH)2, and increased by 168.1% in liquid state when adding 10.4wt.% Mg(OH)2 after the samples calcined at 600 °C for 1h.