Coaxial electrospun nitrogen-doped beaded graphene@carbon fibers for lightweight broadband microwave absorption and thermal insulation

The rapid development of aerospace electronics and electromagnetic protection technologies has created an urgent demand for lightweight, ultrathin, and broadband microwave absorbers. However, carbon-based absorbers face a long-standing paradox between strong electromagnetic attenuation and satisfactory impedance matching, severely limiting their practical application. Herein, we fabricate beaded reduced graphene oxide@carbon fibers (BRC) via coaxial electrospinning and further construct nitrogen-doped BRC (N-BRC) through nitrogen heteroatom engineering, to simultaneously inhibit graphene agglomeration and tailor the balance between impedance matching and electromagnetic loss. The pristine BRC exhibits an ultrahigh attenuation constant (α ≈ 780) but suffers from severe impedance mismatch (Z < 0.3), while nitrogen doping introduces abundant dipole polarization centers, homogenizes the beaded microstructure, and improves the impedance matching parameter (Z ≈ 0.4). The optimal N-BRC sample (GO:urea = 1:5) delivers a minimum reflection loss of −39.6 dB and an ultrawide effective absorption bandwidth of 5.1 GHz at an ultrathin thickness of 2.0 mm. Furthermore, the composite shows outstanding thermal insulation performance owing to its unique beaded fibrous structure. This work provides a feasible strategy of coupling structural design and compositional regulation for developing multifunctional lightweight microwave absorbers.