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

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·m². 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.