Pomb@Co3O4-based composites for ultra-wideband microwave absorption: A multi-scale perspective from micro-, meso- and meta-structure

At the micro-mesoscopic, the Pomb@Co 3 O 4 (0.1 g) composite materials achieved broadband absorption of 12.5–18 GHz. Through the designation in macroscale design, the metastructure not only reached ultra-wideband absorption of 2.89–18 GHz, but also reduced the Radar Cross Section from −60° to 60° effectively. • Biomass carbon materials are beneficial for increasing the secondary using of materials. • The combination of dielectric and magnetic loss materials will promote the absorption microwave performance and reduce the values of RCS. • A new perspective of multi-scale from micro-, meso- and macro-structure for the researching and desiging of high-performance microwave absorbing metastructure. Microwave absorbing materials (MAMs) are used to prevent electromagnetic pollution and enhance equipment stealth. However, their limited absorption intensity and narrow effective bandwidth restrict their applicability. MAMs with a single absorption mechanism, whether dielectric or magnetic, often exhibit poor impedance matching. This paper introduces a new multiscale approach—encompassing microstructures, mesostructures and macrostructures—for designing high-performance MAMs. At the microscopic–mesoscopic level, Pomb materials derived from pomegranate peel are combined with magnetic nanoparticles (Co 3 O 4 ) using a hydrothermal method. The microwave absorption properties of these composite materials were examined by varying the proportion of Pomb materials in the absorber. The effective absorption bandwidth (EAB) reached 5.5 GHz for a thickness of 2.3 mm. At the macroscopic level, a metastructure based on Pomb@Co 3 O 4 (0.1 g) was designed to achieve ultrabroadband absorption with an EAB of 15.56 GHz, a range of 2.24–18 GHz and a total thickness of 15 mm. Additionally, the radar cross-section value of Pomb@Co 3 O 4 (0.1 g) is below − 10 dB m 2 across the angle range of − 60° to 60°, with a maximum scattering intensity of only − 7.6 dB m 2 . This multiscale structure design offers a promising direction for future research and development in MAMs.