Preparation and characteristics of microencapsulated palmitic acid with TiO2 shell as shape-stabilized thermal energy storage materials

Microencapsulated palmitic acid (PA) with titanium dioxide (TiO2) shell as shape-stabilized thermal energy storage material was synthesized through a sol-gel process. Scanning electron microscope (SEM), Fourier transformation infrared spectroscope (FT-IR), X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS) were used to determine the morphology, chemical structure, crystalloid phase and chemical state of the microcapsules, respectively. The thermal properties and thermal stability were investigated by a differential scanning calorimeter (DSC) and a thermogravimetric analyzer (TGA). The microcapsules have relatively spherical shape and average size of 200-400 nm. The FT-IR, XRD and XPS results showed that the PA was well encapsulated in the TiO2 shell. The DSC results indicated that the typical microcapsules melt at 61.7 degrees C with a latent heat of 63.3 kJ/kg and solidify at 56.7 degrees C with a latent heat of 47.1 kJ/kg. The TGA results confirmed that the microcapsules have good thermal stability, resulting from the TiO2 shells. Based on all results, it can be concluded that the prepared microcapsules have good energy storage potential due to their non-inflammability, nontoxicity and good thermal stability. (C) 2014 Elsevier B.V. All rights reserved,