Abstract
The aerospace and fifth-generation (5G) networks have put forward higher requirements for broadband and high-efficiency of microwave absorbing materials. Herein, an ultralight and unidirectional honeycomb-like structural graphene/multiwalled carbon nanotube aerogel (GCA) with a wide microwave absorption bandwidth is fabricated through a simple directional freezing process followed by an annealing treatment. An absorption bandwidth of less than −10 dB is 13.32 GHz in the frequency range of 2–18 GHz. The bandwidth of reflection loss less than −20 dB reaches up to 13.5 GHz, covering the whole Ka-band (26.5–40 GHz) in the existing 5G millimeter-wave communication technology. Notably, a specific microwave absorption performance of 39654.63 dB cm2 g−1 is obtained with a density as low as 3.34 mg cm−3 and thickness of 2 mm. Total carbon content and its reduction degree are the primary means to achieve the impendence matching-attenuation balance. The collective macroscopic arrangement of dipoles caused by the highly directional structures further modifies the interaction with electromagnetic waves. This work provides new inspiration and insight for ultralight and broadband microwave absorbers.
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