Nanoencapsulation of Binary Sugar Alcohols at Neutral pH Conditions

Nanoencapsulation can effectively protect phase change material (PCM) from the ambient. Sugar alcohols have great potential for thermal energy storage. However, base or acid used in the most popular encapsulation methods may damage the PCM core. In this study, binary sugar alcohols of D-mannitol (DM) and inositol (IN) were first nanoencapsulated at neutral pH conditions. Nanocapsules with silica as the shell and different DM/IN ratios of 4.0:1, 4.6:1 and 5.5:1 were synthesized at different precursor ratios of tetraethoxysilane to triethoxysilane of 8:6, 9:5, and 10:4. The nanoencapsulation was demonstrated by scanning electron microscope (SEM), transmission electron microscope, energy-dispersive X-ray spectrometry, and Fourier transform infrared spectrometer. The phase change characteristics, thermal energy storage-release performance and thermal stability of the nanocapsules were studied by differential scanning calorimeter, thermal energy storage-release experiments, SEM, thermo-gravimetric analyzer (TGA) and thermal cycling tests. Results show that the phase change characteristics and thermal energy storage-release performance of the nanocapsules varied with the DM/IN mixing ratio and ratios of precursors. The DM/IN-4.6:1-9:5@SiO 2 nanocapsules exhibited the best phase change characteristics and thermal energy storage-release performance. Thermal stability of the nanocapsules was improved compared to pure binary sugar alcohols.