Patterning of carbon nanotube film for effective microwave absorption over 2–18 GHz

Abstract

Highly conductive carbon nanotube (CNT) networks offer strong dielectric attenuation but often exhibit excessive permittivity and impedance mismatch, limiting broadband microwave absorption. Here, CNT film strips supported on polyethylene terephthalate nonwoven substrates were assembled into multilayer absorbers through multilevel structural regulation. Low-permittivity interlayers and repeating CNT-containing layers are first introduced to balance electromagnetic-wave entry and internal attenuation along the thickness direction. The CNT-covered area in the CNT layer is then reduced from 100% to approximately 67% and 50%. Full coverage of CNTs in such layers provides strong attenuation but unfavorable impedance matching, whereas 50% coverage improves wave entry but produces insufficient broadband dissipation. Among the investigated coverage levels, an intermediate CNT coverage of approximately 67% provided the most favorable compromise between the calculated input-impedance condition and dielectric attenuation. Two complementary patterns with the same fraction of coverage are subsequently alternately stacked to reduce the through-thickness alignment of CNT-free regions and redistribute the CNT-rich regions. The optimized absorber achieves reflection loss below −10 dB over the entire 2–18 GHz range, corresponding to a continuous effective absorption bandwidth of 16.0 GHz. These results demonstrate that broadband absorption in highly conductive CNT systems can be realized through macroscopic spatial engineering without altering the functional material composition.

Graphical abstract

Keywords

carbon nanotube film strips / CNT coverage regulation / staggered stacking / impedance matching / broadband microwave absorption

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