Preparation and thermophysical properties of a novel metallic microencapsulated phase change material/eutectic salt/ceramic composite

Abstract

The development of thermal storage material is crucial for the utilization of thermal energy. At present, eutectic salt/ceramic composite has been widely studied as latent heat storage material, however, its thermal conductivity is low and its latent heat per unit volume is still not ideal, despite its high latent heat per unit mass. Herein, a metallic microcapsule with high thermal conductivity and latent heat per unit volume is introduced to improve the above properties. Using MgO as the support material, metallic microcapsule (Sn@Void@SiO2) and eutectic salt (LiNO3-NaCl) with almost the same temperature range as phase change material, metallic microcapsule/eutectic salt/ceramic composite was prepared by cold-pressure sintering method. The result shows that the best performance of metallic microcapsule/eutectic salt/ceramic composite was achieved with the addition of 30 wt% Sn@Void@SiO2 instead of MgO, the latent heat per unit volume and per unit mass of the composite are 237.1 J/cm3 and 117.9 J/g, which are improved by 56.72 % and 15.48 % respectively. And the thermal conductivity of the composite was improved by 63.79 %, from 0.58 W/(m·K) to 0.95 W/(m·K). Further, the addition of a small amount of Sn to metallic microcapsule/eutectic salt/ceramic composite can not only increase its latent heat but also improve its thermal conductivity as Sn fills the pores inside the composite after melting. The result showed that the thermal conductivity of the composite was increased by 155.17 % than that of eutectic salt/ceramic composite when Sn was added at 5 wt%. Finally, thermal cycle results showed that composites have high thermal reliability and proved high thermal cycling stability of metallic microcapsule prepared by “double-layer coating, sacrificial inner layer” method.