Programmable dielectric loss in gradient carbon nanostructures with built-in electric field boosting dual-band electromagnetic wave absorption

Carbon nanotubes are promising electromagnetic wave (EMW) absorption materials due to their excellent conduction loss and multiple polarization relaxations. However, their high electrical conductivity often causes severe impedance mismatch and small skin depth, leading to strong reflection rather than efficient absorption. Herein, a gradient carbon engineering strategy is proposed to enhance dielectric loss for broadband EMW absorption. Density functional theory calculations confirm that built-in electric fields (BIEFs) synergistically couple with the gradient carbon nanostructure to promote polarization relaxation. Notably, BIEFs facilitate electron transfer and modulate charge distribution, thereby substantially boosting interfacial polarization. With balanced dielectric loss and impedance matching, the resultant composite exhibits dual-band EMW absorption, achieving a minimum reflection loss of −42.3 dB at 5.3 GHz and an effective absorption bandwidth of 3.1 GHz across the C and Ku bands. In addition, the polydimethylsiloxane‑blended composite also shows good thermal conductivity. This work demonstrates the effectiveness of gradient carbon engineering in tailoring dielectric loss and provides a new strategy for designing high-performance EMW absorption materials via BIEFs.