Tunable Electromagnetic Response Behaviors via Cross‐Scale Morphological Structural Engineering for Ultra‐wideband Microwave Absorption^†

Comprehensive Summary The design of cross‐scale morphological structures has emerged as a fundamental strategy to tune electromagnetic response behaviors. However, challenges remain in precisely regulating the morphological structures of absorbers. Herein, the VN@hierarchical porous carbon/cobalt@carbon nanotubes composites were synthesized through sol‐gel self‐propagation method. By adjusting the Co element proportion, the evolution of the carbon nanotube on the surface of microstructure can be regulated. The sample with a molar ratio of 3 : 7 (Co : V) attained a reflection loss value < −20 dB across a wide frequency range (3.68–16.48 GHz) at varying thicknesses. The excellent performance is imputed to the synergistic effect of hierarchical nano/micro‐structure in the samples. Furthermore, the coating resulting from the macroscopic metamaterial design achieved an ultra‐wide effective absorption bandwidth of 12.55 GHz with a minimum reflection loss of −62.37 dB at an equivalent thickness of 2.77 mm, and the maximum radar cross‐section reduction value reached 40.74 dB·m 2 . This work not only provided a novel strategy for developing electromagnetic wave absorbing composites with multi‐band response capabilities, but also emphasized the potential of morphological structural engineering for designing ultra‐wideband absorbers in practical applications.