Synthesis and properties of nanoencapsulated D-mannitol for medium temperature thermal energy storage

Sugar alcohols with high latent heat have great potential for medium temperature thermal energy storage. Micro/nano-encapsulation can effectively improve the performance of phase change materials (PCMs), such as avoiding leakage and enhancing thermophysical properties. However, only a few work have been reported on the microencapsulation of sugar alcohol, and the reported methods showed some drawbacks such as requiring strictly controlled reactions or resulting in disability for the capsules to solidify. This paper reports for the first time the synthesis and properties of nanocapsules of a sugar alcohol D-mannitol (DM) by a facile sol-gel method. The nanoencapsulation was confirmed by various characterization using Fourier transformation infrared spectroscope (FT-IR), X-ray diffractometer (XRD), and transmission electron microscope (TEM). Uniform size distribution of the nanoencapsulated DM (NEDM) in 100-200 nm was observed by scanning electron microscope (SEM). The phase change performance of the NEDMs were investigated by differential scanning calorimeter (DSC). The results show that the NEDMs with a melting temperature of 166.2 degrees C, a melting enthalpy of 220.3 J/g, and an encapsulation ratio of 76.5% were obtained. The thermal reliability of the NEDMs was demonstrated by thermal cycling experiments. The thermal stability of the NEDMs was enhanced compared to DM as investigated by thermogravimetric analyzer (TGA). The NEDMs exhibited great potential for applications in medium temperature thermal energy storage and transfer.