Constructing honeycomb-like hierarchical foam via electromagnetic cooperation strategy for broadband microwave absorption.

The application of wireless electronic devices inevitably leads to electromagnetic pollution. Three-dimensional porous foam structures have been shown to be an effective strategy to construct high-performance microwave absorbers. Herein, the honeycomb-like hierarchical foams were fabricated via melamine-formaldehyde (MF) foam as substrate coupled with flaky carbonyl iron (CI)-MXene lamellae. Inside the synthesized composite foam, flaky CI is interlaced into MXene nanosheets to form hierarchical structures, which effectively alleviates the originally self-stacking phenomenon and provides numerous heterogeneous interfaces, resulting in the optimization of impedance matching. In addition, owing to the construction of consecutive electromagnetic networks, the CI-MXene/MF foams exhibit significant dielectric loss and magnetic loss capability. Moreover, the honeycomb-like structure offers multiple reflections/scattering for electromagnetic waves, which effectively prolongs the transmission paths, further improving the microwave attenuation ability. Hence, the synthesized composite foam exhibits superior microwave absorption performance with a minimum refection loss of −61.4 dB and a maximum effective absorption band of 7.18 GHz. The construction of unique microstructure and regulation of electromagnetic components is demonstrated to be feasible strategies for the design of efficient microwave absorbers in future. [Display omitted] • The hierarchical structure formed by flaky carbonyl iron (CI)-MXene lamellae effectively alleviates the self-stacking phenomenon. • The honeycomb-like coherent electromagnetic network is conducive to optimizing impedance matching and enhancing microwave dissipation capability. • The ultralight composite foams achieve superior microwave absorption performance with broad effective absorption bands. [ABSTRACT FROM AUTHOR]