Microencapsulation of n-octadecane phase change material with calcium carbonate shell for enhancement of thermal conductivity and serving durability: Synthesis, microstructure, and performance evaluation

A sort of new phase change material (PCM) microcapsules based on n-octadecane core and calcium carbonate (CaCO3) shell was synthesized through a self-assembly method to enhance the thermal conductivity and serving durability. Fourier transform infrared spectra confirmed that the CaCO3 wall material was successfully fabricated upon the n-octadecane core. Scanning electric micrographs demonstrated that the n-octadecane microcapsules presented a perfect spherical morphology and a well-defined core-shell microstructure. Wide-angle X-ray scattering patterns indicated that the CaCO3 shell was formed in the crystalline phase of vaterite while the n-octadecane core inside microcapsules still preserved good crystallinity. The microencapsulated n-octadecane also exhibited good phase-change performance and achieved a high thermal storage capability, and however, their encapsulation ratio and encapsulation efficiency were determined by the core/shell mass ratio. Thermogravimetric analysis showed that the microencapsulation of n-octadecane improved the thermal stability by upgrading the evaporating temperature of n-octadecane inside the CaCO3 shell. The thermal conductivity of n-octadecane microcapsules was significantly improved due to the fabrication of highly thermally conductive CaCO3 shell, and the anti-osmosis property and serving durability were also enhanced under the protection of compact CaCO3 shell. Owing to the easy availability and low cost of calcium carbonate, this synthetic technique indicates a high feasibility and a good prospect in industrial manufacture for the microencapsulated PCMs with inorganic shells.