Controllable construction design of Co@C@MWCNTs interpenetrating composite with tunable enhanced electromagnetic wave absorption

Lightweight absorbers with strong broadband microwave absorption are highly desired in military and civil fields. In this work, a 3D interpenetrating network formed from a Co@C@ MWCNTs composite was synthesized via a combined wet chemical and pyrolysis route. Because of strengthening interfacial polarization, suitable impedance matching and synergistic effects, the Co@C@MWCNTs hierarchical composite exhibited outstanding microwave absorption properties. An optimal reflection loss reached − 55.7 dB at 8.7 GHz and its effective bandwidth ( R L  < − 10 dB) achieved 4 GHz (7.4–11.4 GHz) at an absorber thickness of 3 mm with a low filler content of 10 wt%. Furthermore, an effective bandwidth of 12.4 GHz (4.5–16.9 GHz) was obtained by varying the thickness from 2 to 4.5 mm. The superior microwave absorption performance originated from the enhanced interfacial polarization, multiple reflections, conductive network, synergistic effects and an improved impedance matching between Co–C and MWCNTs. This work provides a strategy to rationally design novel lightweight absorbers with strong microwave absorption.