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.
Latent heat storage performance of a layered perovskite-type compound, 1-C 14 H 29 NH 3 ) 2 ZnCl 4 (C 14 Zn), embedded in a series of silica gel (SG) with pore sizes of d = 15–200 nm is investigated using differential scanning calorimetry (DSC), and powder X-ray diffractions (XRD). C 14 Zn in the nanopores of silica gel shows size-dependent phase transition temperature, enthalpy change and supercooling. They have a stable transition temperature and heat capacity at each size in a short-term thermal cycling. Similar X-ray diffraction patterns are observed for the nano-sized and the bulk C 14 Zn. The encapsulation of a phase change material in nanopores is a new way of tuning its thermal energy storage properties for a wider range of temperature regulation.
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