In situ construction of continuous porous AlN skeletons towards enhanced thermal conductivity of epoxy composites

Abstract

Aluminum nitride (AlN) has great potential as a filler in thermally conductive composites due to its extremely high thermal conductivity (TC) (∼320 W m⁻¹ K⁻¹). However, AlN suffers from drawbacks such as high cost and easy hydrolysis. Meanwhile, the traditional random mixing methods significantly increase the filler–polymer interface in composites, thus hindering the TC improvement. To address this issue, a three-dimensional (3D) porous AlN skeleton was successfully constructed through an in situ reaction strategy based on the carbothermal reduction nitriding (CRN) process, using inexpensive alumina as the raw material and polyurethane (PU) sponge as a hard template. The in situ grown AlN grains were tightly sintered together after a high-temperature reaction and connected to form a continuous 3D network, significantly increasing the thermally conductive pathways. Subsequently, the porous AlN skeleton was further used as a reinforcement to combine with epoxy (EP) to prepare thermally conductive composites. The AlN/EP composites achieved a TC of 1.84 W m⁻¹ K⁻¹ at the AlN filling fraction of 42.3 vol%, which was 10.22 times higher than that of pure EP and 4.27 times higher than that of composites with randomly dispersed AlN particles. In addition, the continuous porous AlN skeleton also provides excellent thermal stability and mechanical performance for composites. This work provides a low-cost and simple approach for the continued development of 3D inorganic skeleton/polymer composites, which is of great significance in the preparation of thermal management materials.