Crystallohydrate Loaded Halloysite Nanocontainers for Thermal Energy Storage

The mixture of crystallohydrate phase change materials (PCMs) Na2HPO4 center dot 12H(2)O and Na2SO4 center dot 10H(2)O is loaded into halloysite nanotubes (HNTs) by water bath sonication and impregnation under vacuum at 40 degrees C. It is the first time HNTs are applied as nanocontainers for crystallohydrate PCMs for thermal energy storage. The PCM retains well in the nanocontainers over the solid-liquid phase change, due to the electrostatic interaction between PCM and the inner space of HNTs as well as the nanoconfinement effect. No new covalent bonding is formed between PCM and HNTs in the composite. The crystal structure of the hydrated salts mixture does not change after loading into HNTs. With 67 wt% effective loading of Na2HPO4 center dot 12H(2)O and Na2SO4 center dot 10H(2)O in 1:1 mass ratio, the nanocontainer composite exhibits the melting temperature of 35.8 degrees C and the melting enthalpy of 142 J g(-1). During the thermal cycling tests, it shows no phase separation and the thermal stability is well kept for 50 cycles. The PCM/HNTs nanocontainers can be considered as efficient nanoscaled energy storage units with great potential in practical applications.