A Comparative Study of Transition Metal (Fe, Co, and Ni) Species Embedded in N-Doped Porous Carbon Nanostructures for Microwave Absorption

Transition metal-modified carbon composites have emerged as promising candidates for electromagnetic wave (EMW) absorption due to their tunable microstructure and tailorable electromagnetic properties. However, the influence of metal species configuration on dielectric loss at the atomic scale remains less understood. In this work, we fabricated three types of M-NC absorbers (M = Fe, Co, and Ni; NC = N-doped carbon) using a unified method that includes templating, pyrolysis, and acid etching. This approach produced samples with similar porous structures, which helped minimize structural differences and isolate the effect of the metal species. Among them, Ni-NC achieved a minimum reflection loss of −39.7 dB at 13.3 GHz with a matching thickness of only 2.0 mm, much better than Fe-NC (−22.5 dB) and Co-NC (−27.3 dB). This superior performance is attributed to the specific metal-N bonding structure, which governs both the interfacial polarization and the electronic structure. Meanwhile, the 3D carbon porous framework promotes impedance matching and extends the EMW propagation path through multiple scattering, collectively enabling superior absorption performance. Radar cross section simulation results confirm the effective EMW attenuation of these composites, particularly Ni-NC, highlighting their potential suitability for stealth applications. This work provides fundamental insights for the rational design of high-performance, lightweight EMW absorbers through precise chemical structure engineering.