Enhanced electromagnetic wave absorption performance in carbon fiber via continuous surface modification with layered double oxides

Carbon fiber (CF) is highly prized for its lightweight and excellent electrical conductivity as an electromagnetic wave (EMW) absorbing material. However, impedance mismatch caused by its high conductivity is criticized in electromagnetic wave absorption, thus necessitating the incorporation of magnetic materials to enhance wave absorption performance. This study introduces a novel and efficient continuous hydrothermal approach for the direct synthesis of three distinct two-dimensional layered double hydroxides (LDHs) on the surface of activated carbon fiber (ACF). This method facilitates precise control over the morphology and composition of the LDHs, while simultaneously enabling the scalable and continuous production of fiber samples, thereby significantly enhancing the practical applicability of CF in advanced microwave absorbing materials. On the fiber surface, NiFe-LDH and NiZn-LDH exhibit nanosheet morphologies, while NiCo-LDH forms nanorods. To enhance magnetism, LDHs are calcined into layered double oxides (LDOs), with the surface morphology of ACF@LDOs remaining stable under precise thermal treatment conditions.The results demonstrate that ACF@NiZn-LDO exhibits the most efficient electromagnetic wave absorption (EWA) performance, achieving a remarkable minimum reflection loss (RL min ) of −68.39 dB at a thickness of 1.56 mm and a maximum effective absorption bandwidth (EAB) of 4.13 GHz. From a morphological perspective, the thinner and more compact laminated structure significantly enhances multiple reflections and scattering of microwaves. From a structural design standpoint, its superior impedance matching, coupled with the synergistic effects of multiple polarization mechanisms (e.g., dipole polarization and interfacial polarization) and loss mechanisms (e.g., conduction loss and magnetic loss), collectively contribute to its exceptional microwave absorption capability. This study successfully realizes the continuous preparation of CF-based electromagnetic wave absorbers, offering significant potential for the integrated development of CF in both structural and functional applications.