AlN-based aerogel thermo-cooler enabled by enhanced phonon conduction and unconstrained liquid capillarity

Transpiration cooling is a thermal management technique that utilizes the phase change of liquid coolant to effectively dissipate heat. Porous ceramic media play a crucial role in this cooling process by facilitating liquid transport and heat exchange; however, their intermittent capillary action and inter-grain phonon scattering significantly hinder rapid cooling. Here, we propose a strategy to create AlN-based nanofiber aerogel as a transpiration thermo-cooler, featuring vertically aligned channels and monocrystalline nanofibers by combining nanoengineering and multiscale structural assembly techniques. Benefiting from the unconstrained capillarity of aerogel channels, our thermo-coolers exhibit a fast liquid transport rate of up to 8.33 ± 0.026 mm s−1, surpassing that of state-of-the-art porous media by one to two orders of magnitude. In addition, the enhanced phonon conduction properties of single-crystal AlN nanofibers enables thermo-coolers to achieve a fast cooling rate of 156.8 °C s−1, outperforming advanced cooling materials by a factor of five and making them ideal for various thermal management applications. Cooling failure in porous ceramics under extreme heat flux is tackled by assembling monocrystalline AlN nanofibers into vertical channels, creating fiber aerogel thermo-coolers that enable rapid liquid transfer and efficient heat exchange.