Preparation of porous silicon nitride as supporting skeletons to phase change material with improved anti-leakage and heat conduction performance

The employment of thermally conductive porous ceramic skeletons to adsorb the organic phase change materials (PCMs) is an effective method to address the problems of their low thermal conductivity and easy leakage. In this study, Si powders are used to form porous frameworks through the ice-templated shaping, and are subsequently transformed to Si₃N₄ skeletons by the direct nitridation reaction. Phase change composites (PCCs) were prepared by filling the porous skeletons with paraffin wax (PW) by vacuum impregnation. The layer directional structure of the ceramic skeletons constructs a continuous thermal conductive path, significantly enhancing the thermal conductivity of PCCs. The results demonstrate that when the proportion of Si₃N₄ skeleton reaches 53.3 wt%, the thermal conductivity of PCC in the axial direction was as high as 2.99 W m⁻¹ K⁻¹, which is 14.95 times that of PW. The PCC could maintain an enthalpy of 85.8 J g⁻¹ and a good cycling stability. Additionally, the porous Si₃N₄ skeletons also enable the composites with good shape-stability to avoid the leakage of PW. The enhancement of heat transfer and anti-leakage performance ensures the PCCs in this study with broad application prospects in the fields of heat storage and thermal management.