Multifunctional metastructure for low-frequency ultra wideband absorption, radar cross section reduction and thermal insulation based on the lightweight microwave absorption materials

The lightweight microwave absorbing materials(MAMs) have always been a research hot topics in the field of electromagnetic waves(EMWs) absorption. In this work, the pineapple peel (PA) was used as a carbon source and combined with Co alloys. The hollow porous carbon of the PA after pyrolysis provides advantage for becoming the lightweight MAMs. When the soaking time of PA-800 in the solution of CoCl₂•6H₂O achieves at 60 h, PA-800-60 was successfully prepared which the RL_min of −24.8 dB and the EAB reach 5.8 GHz (12.2–18 GHz) at the thickness of only 1.3 mm. In order to improve the effects of impedance matching, the height of 9 mm frustum metastructure based on PA-800-60 was designed and used for improving microwave absorption in the low-frequency range. The EAB has been expanded from 5.8 GHz to 13.5 GHz (3.5–18 GHz) which covers the C, X and Ku band and the RL_min reached −17.5 dB at the frequency of 7.44 GHz. Meanwhile, the RCS value of PA-800-60 layer is less than −10 dB m² cover the range of −60°–60° and the maximum scattering intensity is only −10 dB m² at the thickness of 2 mm. In addition to, the PA-800-60 exhibits superb thermal insulation performance due to abundant air with lower thermal conductivity take place of solid phase with higher thermal conductivity. This work provides a new direction for the research and development of multifunctional electromagnetic metastructures based on the lightweight MAMs.