Structure Design, Surface Modification, and Application of CNT Microwave-Absorbing Composites

Electromagnetic (EM) contamination has now become a non-negligible problem. To solve the EM contamination problem, it is imperative to develop high-efficiency absorption materials with thin thickness, light weight, strong absorption properties, and broad absorption bands. Carbon nanotubes (CNTs) have a special helical structure and chirality, which will lead to special EM effects and therefore can absorb EM microwaves through magnetic polarization attenuation such as hysteresis loss, domain wall resonance, and aftereffect loss. Moreover, they have the characteristics of light weight, good compatibility, wide absorption frequency band, and high electrical loss angle tangent. In this paper, the different structures of CNT microwave-absorbing composites are reviewed and the effects of the composite structures on the microwave-absorbing properties are systematically discussed. The methods and mechanisms of surface modification of CNT absorber composites and the effects of modification on the absorber properties are summarized in detail. The progress of two specific CNT microwave-absorbing composites, namely flexible and high-temperature microwave-absorbing composites, is briefly described. The shortcomings and challenges in the application of CNT microwave-absorbing composites are described and future research directions for CNT microwave-absorbing composites are explored.