Preparation and characterization of microencapsulated phase change materials containing inorganic hydrated salt with silica shell for thermal energy storage

Inorganic hydrated salts have many advantages over organic phase change materials , such as high thermal storage density, low-cost and non-toxic. Herein, we microencapsulated sodium phosphate dodecahydrate (DSP) with silica through interfacial polymerization combined with sol-gel process and systematically investigated the effects of the reaction conditions on the morphology and encapsulation efficiency of the microcapsules. SEM and TEM were used to characterize the morphology and microstructure of the microcapsules, and the lattice fringes and crystal diffraction ring of DSP inside the microcapsules can be observed by high-resolution TEM and the selected area electron diffraction (SAED). The chemical composition and crystalline structure of the microcapsule were detected by Fourier transform infrared spectra (FTIR) and X-ray diffractometer (XRD), which demonstrated the presence of DSP. DSC results indicated that the microcapsule prepared at 40 °C for 8 h with the core/shell mass ratio of 4: 1 had the highest encapsulation efficiency of 75.3% with the melting enthalpy of 177.0 J/g. The good thermoregulating performance of the microcapsule was demonstrated by adding it to the building model and comparing its temperature variation with the model without any microcapsule. Owing to the facile preparation, large latent heat, good thermal reliability and excellent thermoregulating performance, the obtained microcapsules will have a good prospect in thermal energy storage application.