AlN micro-honeycomb reinforced stearic acid-based phase-change composites with high thermal conductivity for solar-thermal-electric conversion

Phase-change materials (PCMs) for efficient thermal energy harvesting have promising prospects for thermal energy storage and thermal management. However, the low intrinsic thermal conductivity (TC) of PCMs is a long-standing drawback due to a lack of a thermally conductive network inside them. Herein, a cost-effective route for preparing thermal-conductive phase-change composites by freeze-casting and combustion synthesis to obtain micro-honeycomb aluminum nitride (MH-AlN) reinforcements followed by the impregnation with liquid stearic acid (SA) was presented. The as-prepared MH-AlN/SA composite at 44.46 vol% AlN loading exhibited a high TC of 13.95 W m⁻¹ K⁻¹ parallel to the pore channels, up to 53.49-fold higher compared with that of pure SA. The contact thermal resistance between AlN particles can be greatly lowered via constructing a three-dimensional MH-AlN network inside the SA matrix. Additionally, a typical solar thermoelectric generator was devised and photothermal-electric energy transformation was successfully realized. Real-time recorded maximum output voltage and current were 409.0 mV and 110.8 mA, respectively. The enhancement of the heat transfer gives MH-AlN/SA phase-change composites more application prospects in industrial waste heat utilization and effective solar energy harvesting.