Preparation of Microencapsulated Low‐Melting‐Point Sn–Bi Alloy for Latent Heat Storage

Low‐melting‐point SnBi alloy is a good phase change material (PCM) with high thermal conductivity and good stability for heat storage over 100 °C, which can be used for waste heat recovery and solar thermal storage. To solve the critical leakage problem and increase the heat transfer area of PCM, the fabrication of microcapsules of SnBi that are encapsulated by the stable SnO 2 oxide shell is reported. The microcapsules are prepared by a two‐step method, in which the SnBi alloy microspheres are first treated by hot water or vapor and second heat treated under an oxygen atmosphere. The SnBi@SnO 2 microcapsules are well sealed, and can endure a melting–solidification thermal cycle over 100 cycles with good stability. The microcapsules have a melting point of around 139 °C and an enthalpy of around 43 J g −1 , similar to the theoretical values of SnBi. The simple preparation method and good thermal properties of the microcapsules ensures their application in heat storage and thermal management.