Microwave absorption of multi-component CoxNiyOz decorated 3D-honeycomb ordered mesoporous carbon nanospheres enhanced by impedance matching

Abstract

Microwave absorbing materials are essential for mitigating electromagnetic pollution. This study presents novel nitrogen-doped 3D-honeycomb-like ordered mesoporous carbon nanospheres (MCN) synthesized via aniline polymerization on silica templates, followed by the fabrication of multinary-Co_xNi_yO_z–MCN composites through ultrasonic assisted impregnation and high-temperature reduction. The multi-Co_xNi_yO_z–MCN shows remarkable low-frequency absorption with a minimum reflection loss (RL_min) of −44.46 dB at 7.2 GHz and an effective absorption bandwidth (EAB) of 5.28 GHz at 4.4 mm thickness. It also maintains excellent high-frequency performance, reaching −34.5 dB at 12.8 GHz with 2.4 mm thickness and −35.9 dB at 11.9 GHz with 2.6 mm thickness. The multi-Co_xNi_yO_z–MCN 's magnetic components (Co, Ni, CoO, CoNiO₂) synergistically enhance microwave absorption by combining magnetic loss, conductive networks, impedance matching, and interfacial polarization for broadband performance. Furthermore, the open mesostructure of MCN improves impedance matching via enhanced air contact efficiency and enables multi-path electromagnetic (EM) wave reflection/scattering. The composite demonstrates excellent broadband (2–18 GHz) microwave absorption performance, offering an effective approach for lightweight, broadband carbon-based absorbers.