Bi-directionally high thermal conductive phase change composites with radially aligned aluminum nitride skeletons prepared by freeze casting combined with combustion synthesis

Phase change materials (PCMs) have been widely applied in thermal energy storage and thermal management due to their high energy storage density, and good temperature stability during phase transitions. To address the critical problems of low thermal conductivity and leakage tendency of organic solid–liquid PCMs, this paper reports a simple, rapid and low energy input route for preparing porous AlN with bi-directional structure by freeze-casting combined with combustion synthesis, which are used as highly thermal conductive skeletons to support paraffin PCM. The highly porous AlN skeletons can avoid the leakage of melted paraffin, and when the AlN mass load was 56.74 wt% in the phase change composite (PCC), the thermal conductivity in horizontal and axial directions reach 15.63 and 11.72 W m−1 K−1, respectively, which are 78.2 and 58.6 times higher than that of paraffin. Meanwhile, the PCC exhibits a good enthalpy of 82.3 J g−1, which remains stable after long-term cycles of reversible phase changes. The bi-directional heat transfer enhancement provides the PCC with significant potential for applications in the thermal storage and thermal management.