Designing 3D hierarchical assembled Co/CNT structures through in-situ growth of carbon nanotube arrays on coral-like Co for enhanced electromagnetic wave absorption

Material consist of carbon nanotube (CNT) and magnetic nanoparticles could enhance its electromagnetic (EM) wave absorption performance by integrating the characteristics of relevant materials, showing notable potential in EM wave loss. In this study, an innovative H₂-free, low-temperature CVD strategy is developed to rationally design 3D hierarchical assembled Co/CNT structures as high-performance EM wave absorbers, utilizing ethanol (C₂H₅OH) as carbon source and urchin-like Co(CO₃)₀.₅(OH)·₀.₁₁H₂O nanoparticles as the catalytic precursor. Significantly, in 3D hierarchical assembled Co/CNT structures, Co nanospheres-encapsulating CNTs are in-situ grown on coral-like Co in an array arrangement, which not only facilitates electron transport between the two components but also generates numerous heterointerfaces, thereby enhancing conductive loss, which greatly amplifies EM wave attenuation. Owing to the advantages of special 3D hierarchical assembled structure, abundant heterogeneous interfaces, hybrid of dielectric/magnetic components and coral-like Co-CNT array conductive network, multiple loss modes are manifested in the EM wave absorption process, involving conductive loss, dipole polarization, interface polarization, multiple scattering, magnetic loss, and good impedance matching, boosting EM wave absorption. The graphitization degree of CNTs and the crystallinity of Co are controlled by varying the CVD temperature of 3D hierarchical assembled Co/CNT structure, thereby effectively regulating the EM parameters and EM wave dissipation properties. At a synthesis temperature of 650 °C, an EM wave absorption of −31.65 dB and an effective bandwidth of 3.91 GHz are achieved with filler loading of 15 wt%. The preparation of this 3D hierarchical assembled Co/CNT structures just requires a low temperature, obviating the requirement for H₂ and nanoscale catalysts. Furthermore, it possesses a distinctive layered assembly configuration and demonstrates superior EM wave absorption performance even under low-loading conditions. Such characteristics render it applicable in the aerospace domain, including scenarios like the absorbing coatings on aircraft surfaces and the absorbents utilized for honeycomb impregnation.