Carbon nanotubes (CNTs) are grown on the surface of activated carbon hollow porous fibers (ACHFs) by chemical vapor deposition. A multilayer‐like structure absorber ACHFs–CNTs–Fe3O4 is prepared when Fe3O4 nanoparticles/epoxy resin are injected into the hollow structure of ACHFs. Microwave reflection loss, permittivity, and permeability of ACHFs–CNTs–Fe3O4 in 2–18 GHz are measured. The results show that the minimum reflection loss of ACHFs–CNTs–Fe3O4 has reached to −46.828 dB at 14.4 GHz with the thickness of 2.5 mm, and the bandwidth below −10 dB can be as broad as 7.2 GHz. A wide effective absorbing bandwidth can be 13.54 GHz with the variation of the sample thickness from 1.5 to 5.0 mm. The low minimum reflection loss may result from electromagnetic coupling effect of ACHFs, CNTs, and Fe3O4 nanomagnetic particles. The broad absorbing bandwidth is ascribed to its special multilayer‐like structure.
A four-layer absorbing composite on millimeter scale is designed containing an absorbent with multilayer-like structure on the microscale. In this four-layer absorbing composite, epoxy resin acts as transparent layer, the multilayer-like structure absorbent serves as the main absorbing layer; graphene/Ni composite acts as an impedance matching layer; and Fe 3 O 4 nanoparticles serve as a magnetic-loss absorbing layer. The reflection loss of the composites is simulated with CST Microwave Studio, and the absorbency of the composites is discussed in detail when the thickness of each layer is changed. The results show that when the thicknesses of the transparent layer, main absorbing layer, impedance matching layer, and magnetic-loss absorbing layer are 2.5, 2, 1.5, and 2 mm, respectively, the minimum reflection loss of the composite is −51.7 dB, the bandwidth below −10 dB reaches 11.82 GHz, and the density of the composite is nearly 1.9 g cm −3 . Therefore, this new four-layer absorbing composite possesses strong absorbency, broad absorbing bandwidth, thin thickness, and light weight. Thus, a new way to the development of multilayer absorbing composites is presented.
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