Preparation and characterization of flame retardant n-hexadecane/silicon dioxide composites as thermal energy storage materials

Abstract

Flame retardant n-hexadecane/silicon dioxide (SiO 2) composites as thermal energy storage materials were prepared using sol–gel methods. In the composites, n-hexadecane was used as the phase change material for thermal energy storage, and SiO 2 acted as the supporting material that is fire resistant. In order to further improve flame retardant property of the composites, the expanded graphite (EG) was added in the composites. Fourier transformation infrared spectroscope (FT-IR), X-ray diffractometer (XRD) and scanning electronic microscope (SEM) were used to determine chemical structure, crystalloid phase and microstructure of flame retardant n-hexadecane/SiO 2 composites, respectively. The thermal properties and thermal stability were investigated by a differential scanning calorimeter (DSC) and a thermogravimetric analysis apparatus (TGA), respectively. The SEM results showed that the n-hexadecane was well dispersed in the porous network of the SiO 2. The DSC results indicated that the melting and solidifying latent heats of the composites are 147.58 and 145.10 kJ/kg when the mass percentage of the n-hexadecane in the composites is 73.3%. The TGA results showed that the loading of the EG increased the charred residue amount of the composites at 700 °C, contributing to the improved thermal stability of the composites. It was observed from SEM photographs that the homogeneous and compact charred residue structure after combustion improved the flammability of the composites.