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.

在军事和民用领域中非常需要具有强宽带微波吸收能力的轻质吸收剂。在这项工作中，通过结合的湿化学和热解路线合成了由Co @ C @ MWCNTs复合材料形成的3D互穿网络。由于增强了界面极化，合适的阻抗匹配和协同效应，Co @ C @ MWCNTs分层复合材料表现出出色的微波吸收性能。最佳反射损耗在8.7 GHz时达到− 55.7 dB，其有效带宽（R _L <− 10 dB）在3 mm的吸收体厚度下达到4 GHz（7.4-11.4 GHz），填料含量低至10 wt％。此外，通过将厚度从2毫米更改为4.5毫米，可获得有效带宽12.4 GHz（4.5-16.9 GHz）。优异的微波吸收性能源自增强的界面极化，多次反射，导电网络，协同效应以及Co–C与MWCNT之间的阻抗匹配的改善。这项工作为合理设计具有强微波吸收能力的新型轻质吸收体提供了一种策略。