Robust and multifunctional polyimide composite foams via microsphere foaming towards efficient thermal insulation and broadband microwave absorption

The development of efficient and multifunctional broadband microwave absorption (MA) materials is critical for military applications to cope with complex environments. Herein, polyimide (PI)/carbon nanotube (CNT) composite foams (PCCFs) were successfully fabricated by assembling CNT with PI via the microsphere foaming method, where gradient CNT allowed tunable electromagnetic parameters. Benefiting from the improved the impedance matching characteristics and microwave dissipation, PCCFs displayed a remarkable reflection loss value of −53.5 dB and an EAB that could be extended up to 13.5 GHz through thickness variation, encompassing almost all C, X and Ku bands. Furthermore, the composite foams exhibited outstanding mechanical property with a specific compressive strength up to 6.8 MPa/(g/cm 3 ), as well as low thermal conductivity (0.106 W/(m·K)) and excellent heat resistance, which are important references for the development of high-performance MA structural components for applications in extreme environments.