Carbon nanotubes (CNTs) incorporated polymeric composites have been extensively investigated for microwave absorption at target frequencies to meet the requirement of radar cross-section reduction. In this work, a strategy of efficient utilization of CNT in producing CNT incorporated aramid papers is demonstrated. The layer-by-layer self-assembly technique is used to coat the surfaces of meta-aramid fibers and fibrils with CNT, providing novel raw materials available for the large-scale papermaking. The hierarchical construction of CNT networks resolves the dilemma of increasing CNT content and avoiding the agglomeration of CNT, which is a frequent challenge for CNT incorporated polymeric composites. The composite paper, which contains abundant heterogeneous interfaces and long-range conductive networks, is capable of reaching a high permittivity and dielectric loss tangent at a low CNT loading, and its complex permittivity is, so far, adjustable in the range of (1.20 − j0.05) to (25.17 − j18.89) at 10 GHz. Some papers with optimal matching thicknesses achieve a high-efficiency microwave absorption with a reflection loss lower than −10 dB in the entire X-band.

Microwave absorbing materials (MAMs) has been intensively investigated in order to meet the requirement of electromagnetic radiation control, especially in S and C band. In this work, FeCo-based magnetic MAMs are hydrothermally synthesized via a magnetic-field-induced process. The composition and morphology of the MAMs are capable of being adjusted simultaneously by the atomic ratio of Fe²⁺ to Co²⁺ in the precursor. The hierarchical magnetic microchain, which has a core–shell structure of two-dimensional Fe_xCo_1−xOOH nanosheets anchored vertically on the surface of a one-dimensional (1D) Co microchain, shows significantly enhanced microwave absorption in C band, resulting in a reflection loss (R_L) of lower than −20 dB at frequencies ranging from 4.4 to 8.0 GHz under a suitable matching thickness. The magnetic coupling of Co microcrystals and the double-loss mechanisms out of the core-shell structure are considered to promote the microwave attenuation capability. The hierarchical design of 1D magnetic MAMs provides a feasible strategy to solve the electromagnetic pollution in C band.