Fabrication and properties of microencapsulated n-octadecane with TiO2 shell as thermal energy storage materials

Microencapsulated n-octadecane with titanium dioxide (TiO2) shell was prepared by a sol-gel method in a nonaqueous oil-in-water (o/w) emulsion using a green solvent as the dispersion medium. The morphology, chemical structure, and crystalloid phase of the resultant microcapsules were determined by scanning electronic microscope (SEM), Fourier transformation infrared spectroscope (FT-IR), and X-ray diffractometer (XRD), respectively. The differential scanning calorimeter (DSC) and the thermogravimetric analyzer (TGA) were used to investigate the thermal properties and thermal stabilities of the samples. The resulting microcapsules presented spherical shape with average size of 2-5 μm. The results of FT-IR and XRD showed that n-octadecane was well microencapsulated in TiO2 shell. DSC and TGA results indicated that the samples exhibited good performance of storing and releasing the latent heat during phase-change cycles and high thermal reliability. The microencapsulation process in this study is simple, high-efficiency, and environmentally friendly. The microencapsulated n-octadecane with TiO2 shell will be a potential candidate material for thermal energy storage applied in the fields of solar energy storage, building energy conservation, air-conditioning systems, and waste heat recovery.