Regional Segregated Architecture Strategy for High-Efficiency Microwave Absorption of Polyimide Foam

Polyimide (PI) microwave absorption (MA) foam characterized by its superior electromagnetic protection performance and adjustable mechanical properties, is considered a quintessential structure-function integrated material. Currently, the expressed low compressive strength (∼kPa) of PI MA foam matrix limits application as a direct load-bearing component, despite potential enhancements through chemical modification and process optimization. Herein, leveraging the higher compressive strength of aramid honeycomb, a foam precursor solution with a more controllable foaming process is integrated into the aramid honeycomb framework to confine foam growth, thereby achieving excellent conformality between the PI foam and honeycomb. The confined growth of foam within the honeycomb cells mitigates the interfacial defects between cell walls and foam, synergistically coordinating the respective advantages of foam and honeycomb to achieve a mechanically reinforced composite foam structure. Experimental and simulation findings manifest that the optimized structural parameters of the wave-transparent phase (honeycomb), electromagnetic characteristics and topological configuration of the periodic foam units within the constructed regional segregated architecture positively influence MA performance. Ultimately, the optimized CNT/PI/Honeycomb composite foam is endowed with the effective absorption bandwidth (EAB), completely covering the entire X-band under flexible matching thicknesses (2.0-5.0 mm), which highlights potential application in electromagnetic protection functional and load-bearing integrated structure.