Al-Microcapsules with a Self-Sacrificial Oxidation Method for High-Temperature Thermal Energy Storage

Traditional high-temperature energy utilization systems employ conventional solid sensible heat storage (SHS) for energy storage. Latent heat storage (LHS) serves as a surrogate for energy storage as opposed to the SHS system due to the presence of phase-change materials (PCMs). In this paper, we report the production and characterization of Al microencapsulated PCM (MEPCM) through a simple one-step self-sacrificial oxidation fabrication process, where the core-shell type microencapsulated with Al microsphere (mean diameter 35 μm, melting temperature 669 °C) acted as the core (PCM) and Al₂O₃ as the shell. During the oxidation process, the surface layer of the Al microparticle was sacrificed to form a stable Al₂O₃ shell, which was only about 50 nm thick presented by means of a focused ion beam (FIB). In terms of the analyses of FIB and X-ray photoelectron spectroscopy (XPS), it is apparent that Al₂O₃ is successfully formed on the surface of Al microparticles, which can keep a stable solid shell structure during solid-liquid phase transitions. The latent heat of MEPCM was 310.4 kJ/kg, and the melting temperature was 668 °C. Thus, the one-step self-sacrificial heat-oxidation technique can lead to better commercialization and environmental friendliness of next-generation LHS-based high-temperature thermal energy storage materials.