Novel thermal-insulating and microwave-absorbing AlN/C aerogels prepared via solvent-free ambient pressure aging combined with carbothermal reduction nitridation technique

The rapid progress in aerospace development has created severe thermal and electromagnetic environmental challenges. There is a significant increase in the need for thermal protective materials that combine thermal insulation and electromagnetic wave absorption (EWA) capabilities. Herein, we developed an innovative solvent-free ambient pressure aging (SFAPA) method combined with carbothermal reduction nitridation (CRN) to synthesize novel aluminium nitride/carbon aerogels (ACs). The hydrogen-bonding network enables the Al 2 O 3 nanorods to adhere robustly to the resorcinol/formaldehyde (RF) intermediate, ensuring efficient RF entrapment throughout the SFAPA process. The SFAPA method eliminates the need for aging and replacement processes, significantly reducing production costs. Investigating the reaction mechanism of ACs revealed that the carbon layer effectively prevents the formation of α-Al 2 O 3 , improving reaction efficiency. Concurrently, the carbon layers undergo a progressive process of structural ordering toward graphitization. The support provided by the nanorods results in a low shrinkage rate of 3.68 % for the ACs. The as-prepared ACs are lightweight (0.037 g/cm 3 ) and have low thermal conductivity (0.0332 W·m −1 ·K −1 ). Besides, the carbon layer effectively shields the AlN, enabling the ACs to exhibit good oxidation resistance even after a 10-min exposure to 1300 °C butane flame, while maintaining a low backside temperature of 132.6 °C. AlN/C10 exhibits outstanding microwave absorption performance, achieving a minimum reflection loss (RL min ) of −60.37 dB (17.33 GHz, 1.62 mm) and an effective absorption bandwidth (EAB) of 5.55 GHz (12.45–18 GHz, 1.87 mm). The successful fabrication of the ACs pioneers a way for the design and manufacture of AlN-based aerogels for thermal insulation and microwave absorption.