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Ultra-broadband electromagnetic absorption has become a critical issue competing with the advanced broad-band electromagnetic detection systems. In this study, a novel metamaterial with periodic square frustums was designed and prepared, based on the carbonyl iron powder/carbon fiber/Resin composites. The electromagnetic parameters for each component of the meta-structure were determined by the addition content of carbonyl iron powder and carbon fiber, and the prepared metamaterial with optimized electromagnetic and structural parameters realized efficient EM absorption (>90%) in the frequency band of 3.5–40 GHz. Additionally, the electromagnetic absorption mechanism is believed to be attributed to the synergic result of the multiple electromagnetic loss modes and the improved impedance matching caused by the multi-scale structure. Therefore, the proposed metamaterial absorber realizes an ultra-broadband electromagnetic absorption with a coordinated optimization of electromagnetic parameters and meta-structure, which could be served as electromagnetic wave absorbing devices for broadband absorption applications. • A novel metamaterial with periodic square frustums was designed and prepared. • Efficient EM absorption (>90%) in frequency band of 3.5–40 GHz was realized. • The design strategy for this ultra-broadband metamaterial was verified. • The electromagnetic wave absorption mechanism was specified. [ABSTRACT FROM AUTHOR]

Ultra-broadband electromagnetic absorption has become a critical issue competing with advanced broadband electromagnetic detection systems. In this study, an innovative strategy for the broadband absorption is proposed via combining periodic patterns and the hierarchical structure with gradient electromagnetic performance, which introduces an abnormal electromagnetic response for improved maneuverability in impedance matching and multiple electromagnetic loss mechanisms. The electromagnetic parameters for each layer were determined by the fixing content of multi-walled carbon nanotubes (MWCNTs) in gypsum, and the periodic stepped meta-structure was optimized via the finite element simulation. The optimized hierarchical MWCNTs/gypsum metamaterial with a thickness of 8.0 mm realized an average absorption intensity of −21.6 dB (>99.3% absorption) in the frequency band of 4–40 GHz. Particularly, broadband EM absorption for reflection loss less than −10 dB and −15 dB was achieved in the ranges of 4.2–40 GHz and 5.6–40 GHz, respectively. The ultra-broadband and strong electromagnetic absorption properties of the proposed metamaterial should be the synergic result of the excellent impedance matching and the multiple EM wave loss caused by the multi-scale integrated structure. Therefore, the proposed MWCNTs/gypsum metamaterial with the innovative strategy of combining the hierarchical structure and periodic patterns, could provide an insight for achieving high-performance absorption materials. [Display omitted] • An innovative strategy combining periodic patterns and the hierarchical structure is proposed for broadband EM absorption. • The effective absorption bandwidths for reflection loss less than −10 dB and −15 dB are 4.2–40 GHz, 5.6–40 GHz, respectively. • The synergy of the impedance matching and the multiple electromagnetic wave loss is discussed with the multi-scale structure. [ABSTRACT FROM AUTHOR]