Pomegranate-like phase-change microcapsules based on multichambered TiO2 shell engulfing multiple n-docosane cores for enhancing heat transfer and leakage prevention

Abstract

Conventional egg-like core–shell structured phase-change microcapsules present a limitation in thermal conductance and leakage prevention. Aiming at offering a solution to such two issues, we design a unique pomegranate-like structure for the TiO2@n-docosane phase-change microcapsules to enhance their heat transfer transfer and anti-leakage capabilities. The microcapsules were fabricated through a controllable hydrolysis reaction of titanic source in a nonaqueous emulsion-templating system, followed by the polycondensation of its hydrolysates. In the synthesis, the pomegranate-like structure was derived from a double-layered emulsion system based on the internal aggregated small-sized micelles and external large-sized spherical micelle employing a two-step emulsification technique with a nonionic surfactant template. The resultant microcapsules gained high phase-change enthalpies of over 170 J/g at a slow dropwise adding speed of deionized water as a catalyst, and their latent-heat capacity is superior to most of the TiO2-based phase-change microcapsules reported in the literature. Although the pomegranate-like TiO2@n-docosane microcapsules have a relatively lower latent-heat capacity than the conventional egg-like ones, their heat transfer, thermal response, and anti-leakage capability are improved significantly thanks to their unique pomegranate-like structure. Moreover, the pomegranate-like TiO2@n-docosane microcapsules obtained an increase in thermal conductivity by 471% in comparison with pure n-docosane, and their leakage rate decreased by 66.5% compared to the egg-like ones. With superior thermal performance, the novel pomegranate-like phase-change microcapsules developed in this study offer great potential in thermal energy storage and management applications.