Kaolinite nanotube-stearic acid composite as a form-stable phase change material for thermal energy storage

Abstract Kaolinite (Kaol) is a natural industrial mineral that has the advantages of a low cost, flame retardance, and a porous layered structure. In this study, a form-stable phase change material (FSPCM) for thermal energy storage was prepared by adsorbing stearic acid (SA) into the pores of the washed and ultrasonically treated Kaol-cetyl trimethylammonium chloride intercalation compound (Kaol-nanotubes). Analysis techniques, including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetry (TG), and scanning electron microscopy (SEM), were used to study the structures, compositions, and thermal properties of the prepared composites. The maximum mass ratio of the SA adsorbed into the Kaol-nanotubes without leakage was as high as 35.6%, and this was ascribed to the extensive exfoliation and curling of the particles. SA was impregnated maximally into the Kaol and the Kaol-dimethyl sulfoxide intercalation compound (Kaol-DMSO) at 25.2% and 32.3%, respectively. The SA/Kaol, SA/Kaol-DMSO, and SA/Kaol-nanotube composites had phase change temperatures of 53.0 °C, 51.9 °C, and 52.4 °C and latent heats of 33.8, 43.4, and 47.5 J/g, respectively. Furthermore, these composites exhibited distinct enhanced thermal stabilities. Due to the high adsorption capacity, high latent heat, good thermal stabilities, and low cost, the SA/Kaol nanotube composite is a potential FSPCM for practical applications.