Bioinspired moth-eye multi-mechanism composite ultra-wideband microwave absorber based on the graphite powder

Broadband electromagnetic wave absorbers are of great significance in military and civil fields. Absorbent coatings, although highly conformal, suffer from a narrow absorption band and a single absorption mechanism. In this work, inspired by the idea of bionics, we extracted the structural model of the moth-eye and designed the structure size by using electromagnetic simulation. Conductive graphite powder was selected as the wave absorbing agent due to its good dielectric and conductivity losses, and the final products were prepared according to the structural parameters obtained from the simulation. The result shows that the frequency bandwidth with absorption rate above 90% (reflection loss < -10 dB) of the products could reach 13 GHz, including C, X and Ku bands. The equivalent electromagnetic parameters of the bionic structure absorber were extracted by the inversion method, and its impedance gradient absorption mechanism was revealed by combining with the transmission line theory. In order to optimize low frequency (S-band) absorption, the introduction of Salisbury screen and bionic structure absorber combinations to form a composite absorber, the low-frequency absorption performance is effectively improved. The work shows that the combination of two absorption mechanisms, impedance gradient and interference, could effectively improve the absorption bandwidth of electromagnetic waves, providing a good idea for the design of the carbon-based broadband absorber.