Preparation and characterization of capric-stearic acid/montmorillonite/graphene composite phase change material for thermal energy storage in buildings

A novel composite phase change material (PCM) of capric-stearic acid/montmorillonite (CA-SA/MMT) with thermal conductivity enhanced by graphene (GR) was prepared. It was characterized by FT-IR, XRD, SEM, DSC and thermal conductivity tests. The temperature response of CA-SA/MMT/GR was evaluated by heating and freezing the composite PCMs in tinfoil cups. The phase change mortar containing CA-SA/MMT/2 wt%GR was also prepared, and its mechanical strength and thermal behavior were tested. The adsorption rate experiment results show that the mass ratio of CA-SA to MMT is 35:65, which can effectively prevent the leakage of PCM. The FT-IR, XRD and SEM results demonstrate that the prepared CA-SA/MMT/GR has good chemical compatibility and stability. The DSC results reveal that the CA-SA/MMT/GR has suitable phase change temperature and high latent heat, and it can retain the phase change behavior after 300 thermal cycles. The thermal conductivity of CA-SA/MMT/2 wt%GR increases by 156.4% compared with CA-SA/MMT. The heat transfer efficiency of CA-SA/MMT gradually increases with the increase of GR. The mechanical strength and thermal behavior results of phase change mortar demonstrate that the flexural strength and compressive strength decrease and the heat storage capacity increases with increasing the percentage of CA-SA/MMT/2 wt%GR.