Microencapsulating n-docosane phase change material into CaCO3/Fe3O4 composites for high-efficient utilization of solar photothermal energy

Microencapsulating phase-change materials (PCMs) into CaCO3 shell is considered as an effective way to resolve the leakage problem of the microcapsule system and enhance its heat transfer. Herein, we designed and fabricated a type of phase-change microcapsule system based on an n-docosane core and CaCO3/Fe3O4 composite shell using a nonaqueous emulsion-templated self-assembly technology for enhancing solar photothermal energy absorption, conversion and storage performance. The type and addition amount of templating agent and the mass ratio of PCM core to wall material play key roles in the formation of microcapsules with a controllable spherical or rhombohedral morphology and a perfect core-shell microstructure. The resultant phase-change microcapsules show a satisfactory latent heat-storage capacity of around 140 J/g, high encapsulation ratio of over 59%, high thermal conductivity of 0.795 W m−1 K−1, excellent leakage prevention capability and good thermal cycle stability when synthesized under the optimum synthetic condition. More importantly, the phase-change microcapsules exhibit a significant enhancement in solar photothermal conversion and storage performance due to the presence of Fe3O4 nanoparticles in their shell, and their photothermal conversion efficiency was improved by 47.9% compared to the corresponding microcapsules without Fe3O4. In conclusion, the phase-change microcapsules developed in this work show considerable potential in high-efficient solar energy utilization.