Due to the rapid development of high-temperature thermal energy storage (TES) applications such as industrial waste heat recovery and solar thermal utilization, it is urgent to develop reliable phase change materials (PCMs) used in high-temperature energy systems. High-temperature PCMs based on molten salts suffer from inherent low thermal conductivity and large undercooling. Metals are perfectly suitable as the high-temperature PCMs because of their high thermal conductivity and high heat storage density. However, due to the volume expansion of metals during high temperature phase change, the packing of metallic PCMs to resolve their leakage and high corrosive problems has not been completely solved. This study reports that Cu@Al₂O₃ high-temperature macro-encapsulated PCMs over 1000 ℃ are fabricated successfully. Copper powders are used as raw material which are spherulitized to millimeter-sized core balls with the help of binder, subsequently the surface of the porous core balls is cladded with alumina shell. Cu@Al₂O₃ macrocapsules with voids are prepared by high temperature sintering at 1200 ℃. The raw core balls consisted of Cu powders are not densified which contained many gaps and pores, acting as the buffer spaces to the volume expansion during high-temperature sintering and melting of Cu. The melting temperature and latent heat of the core metallic PCM are 1063 ℃ and 205 J/g, respectively. After the melting and solidification cycling test, the intact capsules could be well retained without crack or leakage, and the thermal performance of the core nearly remains equivalent after the cycle. The results demonstrate that the as-prepared Cu@Al₂O₃ macrocapsules are applicable as high-temperature PCMs which can accelerate high-temperature thermal energy storage systems.

thermal energy storage, phase change capsule, phase change material, thermal management