Emerging mineral-coupled composite phase change materials for thermal energy storage

Abstract

A mineral-coupled support, flake graphite-carbon nanofiber-modified bentonite, was used to stabilize stearic acid for constructing form-stable phase change material composites. In order to achieve a synergistic improvement of thermal conductivity and loading space, the supporting material was prepared by growing carbon nanofiber on flake graphite surface through chemical vapor deposition technique and then chemically bonding with modified bentonite. The effect of coupling behavior on interfacial thermal resistance was investigated and results show that the thermal conductivity of the coupled supporting material (4.595 W m−1 K−1) is higher than that of non-coupled support (4.291 W m−1 K−1), proving chemical bonding can decrease interface thermal resistance at a certain extent. The performances of composites were further explored, which indicates the obtained composite base on coupled support possesses good chemical compatibility, and great thermal stability under 180 °C. It also shows that this composite with 41.90% loading capability has latent heat value of 79.13 J g−1 for melting and 79.13 J g−1 for freezing, respectively. After 50 heating-cooling cycles, the variation of melting latent heat was within 0.05%, exhibiting a great thermal reliability. Besides, thermal conductivity of this composite is 10.50 times higher than that of pure phase change material, resulting in more rapid heat transfer efficiency, and excellent transient temperature response recorded by thermal infrared images. In all, the composite is a potential candidate for thermal storage applications due to larger latent heat capability and considerable thermal conductivity.