Physical Fields Coupling Freeze‐Drying Process of Carbon‐Based Composite Aerogels for Microwave Absorption and Electromagnetic Interference Shielding

Abstract Inspired by physical field freezing technology from frozen food engineering, the ultrasonic field and static magnetic field are integrated simultaneously into the freeze‐drying process to prepare aerogel for the first time. Taking polyimide(PI)‐derived carbon composite aerogels as an example, it is demonstrated that the ultrasonic field and magnetic field are capable of regulating the ice crystal size by affecting the liquid cooling phase and the phase transition phase, respectively. The aerogel structure with small pore size and narrow pore size distribution is obtained. Thus leading to the formation of an abundant conductive network and heterogeneous interface, so as to realize the regulation of the porous structure of aerogels. Secondly, the coupling of ultrasound and magnetic fields addresses the agglomeration and realizes the orientation alignment of nanofillers. The charge storage capacity and conductivity of the system are improved. Therefore, the electrical conductivity, conductive loss, polarization loss, and multiple reflections of the composite aerogel are enhanced to obtain improved electromagnetic shielding performance microwave absorption property. The present work provides a scalable reactive processing pathway for the structural modulation of aerogels.