Aligned Al2O3@ carbon ultrafine-fibers@ graphitic carbon nitride composite with thermal conductivity and electromagnetic attenuation in the C-band

Abstract The rapid advancement of electronic devices toward miniaturization and lightweight design has intensified the challenges of electromagnetic interference and thermal management. The Al 2 O 3 @CUF@g-C₃N₄ composite synergistically integrates broadband microwave absorption and high thermal conductivity to address this challenge. The aligned CUF network offers a high attenuation constant at low frequency and continuous 3D pathways for electron/phonon transport. The g-C₃N₄ coating further enhances performance by introducing abundant interfaces and leveraging its intrinsic thermal conductivity. The optimized composite achieves an effective absorption bandwidth (EAB) of 4.00 GHz (4.00 ~ 8.00 GHz), fully covering the n79 band (4.4 ~ 5.0 GHz) for 5G communications. At 3.10 mm thickness, the EAB extends to 7.8 GHz. Additionally, the in-plane thermal conductivity (λ ∥ ) of the composite reaches 2.77 W·m⁻¹·K⁻¹, representing an 18-fold enhancement over random CUF (0.147 W·m⁻¹·K⁻¹). This integrated design coupling of 0D particles, 1D fibers, and 2D sheets, enables the formation of multiple thermal conduction and microwave attenuation pathways.