Carbon microspheres/carbon sheets as efficient electromagnetic wave absorbers

To address the issue of weak absorption intensity and narrow frequency band in pure dielectric electromagnetic wave (EMW) absorbing materials, this study adopts a simple method to successfully prepare a pure dielectric EMW absorption material by modifying acrylonitrile–methylmethacrylate copolymer carbon microspheres (co-AN-MMA@CS) with capsaicin-like 3,5-dimethylphenol derivative (DMPD). The introduction of DMPD into the carbon microspheres increases the heteroatoms (N, O) in the carbon material, thus resulting in functional groups (-C-N, –NO, and C–O) that enable energy loss through dipole polarization. Additionally, the special morphology of carbon microspheres attached or embedded in carbon sheets derived from DMPD increases the inhomogeneous interfaces, thereby increasing the interface polarization relaxation and further attenuating EMWs. The resulting carbon material with the optimal structure (denoted as CNO-2) exhibits superior EMW absorption properties. At a thickness of 2.50 mm, the minimum reflection loss (RLmin) reaches −63.10 dB at 13.14 GHz, whereas the maximum effective absorption bandwidth (EABmax) reaches 6.81 GHz (8.95–15.76 GHz). CNO-2 has excellent EMW absorption capabilities due to the controllable complex dielectric constant and multiple attenuation mechanisms, including interfacial polarization, dipole polarization, and conduction loss. The CNO absorbers prepared in this study can be used as efficient microwave absorbers for electromagnetic protection applications.