Synthesis and Characterization of Robust SiO₂-Phase Change Materials (PCM) Microcapsules

Inorganic SiO2 microencapsulated phase change materials (MEPCMs) have been developed via polymerization reaction and electrostatic interaction in an emulsion system. The resultant microcapsules were systematically characterized in terms of morphology, composition, thermal stability, durability and mechanical property. The energy storage capacity of the obtained microcapsules ranges from 190.5 J/g to 225.5 J/g (pure octadecane: 250.6 J/g) when the core material is octadecane at different sizes. SiO2-PCM microcapsules showed improved energy storage efficiency in terms of shorter melting and freezing durations attributed by the higher thermal conductivity of inorganic silica shell compared with that of polymer shell encapsulated PCM. Repeatable melting and freezing processes after 150 cycles revealed excellent shell tightness and thermal stability of the resultant microcapsules. The high apparent compressive strength of individual SiO2-PCM microcapsule indicated good survivability in further materials processing for energy storage. The robust SiO2-PCM microcapsules obtained from a facile fabrication approach in this study have great potential applications for developing energy efficient materials.