Enhancement of thermal conductivity by graphene as additive in lauric-stearic acid/treated diatomite composite phase change materials for heat storage in building envelope

The composite phase change materials (PCMs) of lauric-stearic acid/treated diatomite/graphene (LA-SA/ Dt/GR) for heat storage in building envelope were prepared. It was characterized by Fourier transform infrared spectrum (FT-IR), X-ray diffraction (XRD), scanning electronic microscope (SEM), thermogravimetric analysis (TG), differential scanning calorimeter (DSC) and thermal conductivity tests. The thermal performance was tested by heating and cooling the composite PCMs in tinfoil cups. The FT-IR, XRD and SEM results show that there is no chemical reaction among LA-SA, Dt and GR, and the prepared LA-SA/Dt/ GR can keep its chemical stability after 1000 thermal cycles. The TG results demonstrate that the prepared LA-SA/Dt/GR has good thermal stability. The DSC results manifest that the prepared LA-SA/Dt/ GR has proper temperature and high latent heat, and can keep its thermal properties after 1000 thermal cycles. The thermal conductivity results demonstrate that GR can significantly enhance the thermal conductivity of LA-SA/Dt and the thermal conductivity of LA-SA/Dt/2wt%GR has increased by 274% compared with that of LA-SA/Dt. The thermal performance results reveal that the heat transfer efficiency of LA-SA/ Dt/GR increases gradually with the increasing percentage of GR. Furthermore, the phase change mortar was prepared, and the mechanical strength and thermal performance were tested. The results testify that the mechanical strength decreases with the increasing percentage of LA-SA/Dt/GR, and GR can significantly enhance the heat storage efficiency of phase change mortar. (c) 2021 Elsevier B.V. All rights reserved.