Lightweight carbon fiber aerogel@hollow carbon/Co3O4 microsphere for broadband electromagnetic wave absorption in X and Ku bands

The increasing proliferation of modern communications, radar systems, and military equipment operating in the X and Ku bands (8–18 GHz) has exacerbated the issue of electromagnetic wave (EMW) pollution, highlighting the urgent need for lightweight, broadband EMW-absorbing materials. In this paper, the lightweight carbon fiber aerogel@hollow carbon/Co 3 O 4 microsphere (CFA@H–C/Co 3 O 4 ) were composed by ZIF-67 derived hollow carbon/Co 3 O 4 microsphere and bamboo cellulose fiber derived carbon fiber aerogels and constructed by in-situ chemical deposition, dopamine treatment and pyrolysis. Carbon fiber aerogels form a lightweight three-dimensional (3D) interconnected conductive network, which expands the multiple reflection and absorption paths of EMW and increases the dielectric loss. The hollow carbon/Co 3 O 4 microsphere inhibits the collapse of the structure by forming a polydopamine shell through the self-polymerization effect of dopamine on the surface of ZIF-67 during pyrolysis, showing dipole polarization loss, interface polarization loss and magnetic loss, which plays an important role in improving EMW polarization loss and optimizing impedance matching. The minimum reflection loss (RL min ) of CFA@H–C/Co 3 O 4 reaches −43.5 dB at frequency of 12.88 GHz with thickness of 3.0 mm and the effective absorption bandwidth (EAB) of CFA@H–C/Co 3 O 4 reaches 7.84 GHz (10.08–17.92 GHz) with thickness of 3.0 mm, covering most of X and Ku bands at a low filling ratio of 15 wt%. The radar cross-section (RCS) value of CFA@H–C/Co 3 O 4 is 22.68 dB m 2 lower than the perfect electrical conductor (PEC). This study provides valuable insights into materials that can improve the absorption bandwidth of electromagnetic waves in the X and KU bands.