Preparation of sodium nitrate/silica composite as shape-stabilized phase change material via sol-gel method and its characterization

NaNO₃)/SiO₂ composite was prepared as a shape-stabilized solid-liquid phase change material (PCM) by sol-gel method with Na₂SiO₃ as silica source. In this composite, the in-situ generated NaNO₃ acted as the latent heat storage material, and SiO₂ as the supporting material. Its chemical composition, morphology, structure and thermal properties were characterized. The results showed that the prepared composite PCM was a physical hybrid of NaNO₃ and SiO₂ only, NaNO₃ was well dispersed in the porous network of SiO₂. The composite had good thermal stability in the temperature range of less than 600℃, its phase change latent heats of melting and freezing were 144.1 and 142.6 kJ/kg, and the temperatures of melting and freezing 302.3 and 301.2℃, respectively. Furthermore, the NaNO₃/SiO₂ composite maintained good thermal energy storage and release ability even after 100 cycles of melting and freezing.