A novel form-stable phase change material based on halloysite nanotube for thermal energy storage

Halloysite nanotube (HNT), a natural and environmentally friendly low-cost material with significant reserves, has become one of promising candidates for preparation of form-stable composite PCM with satisfactory thermal properties owing to their hollow tubule structure and high surface area. The present work prepared the form-stable composite with HNTs and acid etching HNTs (A-HNTs) and compares the properties closely related to thermal energy storage application. Specifically, the micromorphology, thermal properties, shape-stabilized properties, as well as thermal conductivities of the composite materials were characterized by utilizing SEM, TEM, FTIR, DSC, BET, and Hot-disk wire methods, respectively. The results showed that the n-octadecane can both adhere on the inner lumen and the outer wall of HNTs and A-HNTs, while the A-HNTs possess significantly improved absorption thanks to the fact that the pore volume of A-HNTs was enlarged by 19.2% in comparison with HNT, which empowers the extra 5.8% phase transition enthalpy of n-octadecane@A-HNT. In addition, the composite PCMs have a good long-term thermal stability based on multi-cycle heat absorption and release further highlights the potentials in thermal storage application.