International Journal of Energy Research, Vol.44, No.13, 10008-10022, 2020
Study on the microstructures and thermal properties ofSiO(2)@NaNO(3)microcapsule thermal storage materials
In this paper a novel SiO2@NaNO(3)microcapsule thermal storage material is successfully fabricated via water-limited sol-gel method. The effects of SiO(2)nanoparticles on the microstructures, thermal conductivity, specific heat capacity, latent heat and thermal stability are investigated. SEM and TEM investigation indicates that the spherical SiO(2)nanoparticles with an average diameters of 30 nm are coated on the surface of NaNO(3)evenly to form a homogeneous and stable core-shell structure. Microencapsulated composites are characterized by XRD and FTIR to determine the chemical compositions and structures. The thermal conductivity of SiO2@NaNO(3)microcapsules is significantly enhanced by 62.9% (0.756 W m(-1)K(-1)) compared with 0.464 W m(-1)K(-1)of that of NaNO3. In addition, the latent heat, phase change temperature, specific heat capacity and thickness of shell of the microencapsulated NaNO(3)with 18.1 wt% SiO(2)were 310.1 degrees C, 144.7 J g(-1), 1.831 J/(g center dot K), and 80-150 nm, respectively. Furthermore, microencapsulated NaNO(3)have excellent shape and thermal stability at working temperature range. SiO(2)nanoparticles are uniformly attached to the modified NaNO(3)by electrostatic interaction to create a physical protective SiO(2)barrier, which can effectively inhibit the leakage and cauterization of melting NaNO3.