High-temperature thermal stability and thermal conductivity of Al/AlN-C core-shell microencapsulated phase change material

Abstract

Core-shell phase change materials with high thermal storage and thermal conductivity have attracted significant attention in the development of solar thermal utilization technology. The selection and construction of shell materials are crucial for ensuring their excellent performance. In this study, Al/AlN-C composite shell microencapsulated phase change materials (MEPCMs) were prepared using metal Al as the phase change material, supplemented with melamine as a nitrogen and carbon source through low-temperature nitriding. During the reaction process, the melamine was pyrolyzed at different temperature stages to produce ammonia, carbon, and carbon-nitrogen compounds. Pyrolyzed ammonia facilitated the formation of an AlN shell while carbon and carbon-nitrogen compounds coated the surface of the core material to form an AlN-C composite shell. The Al@AlN-C exhibited excellent thermal energy storage capacity (293.68 J g⁻¹) when prepared at 800 °C. After 100 melting-freezing cycles, the latent heat value of microcapsules decreases only 5.40 %, reaching 277.80 J g⁻¹, indicating excellent thermal cycle stability. In addition, the microcapsules possess high thermal conductivity (25 °C, 7.45 W/(m·k)), showcasing their significant potential for utilization in high-temperature heat storage systems.