Enhancement of low-frequency electromagnetic wave absorption in inverse opal carbon microspheres by constructing magnetic carbon nanotube networks within uniform pores

Enhancing the low-frequency electromagnetic wave absorption performance of carbon microspheres with a uniform aperture inverse opal structure is both challenging and practically valuable. This study integrates opal-structured assembly technology with a metal-organic framework (MOF) derivation strategy to fabricate carbon microspheres featuring magnetic particles/magnetic carbon nanotubes confined growth within anti-opal pore cavities (denoted as CSC@ZCN). Using carboxyl-modified inverse opal-like porous carbon spheres (C-CSC) as the substrate, in situ growth of nanoscale MOFs is achieved. By combining a self-catalyzed vapor deposition process with controlled Oswald ripening of metal particles, we achieve the in situ growth of carbon nanotubes (CNTs) encapsulating magnetic metal particles at their tips within uniform vesicles. Controllably woven magnetic CNTs within the vesicles form a network that enhances heterogeneous interfaces, improving porosity and impedance matching. The surface-grown magnetic CNTs extend outward, acting as “bridges” interconnecting the carbon sphere to facilitate the formation of a three-dimensional continuous conductive network. These structural features effectively enhance the low-frequency electromagnetic wave absorption performance of the inverse opal-structured carbon microspheres. Notably, the CSC@ZCN-800-2 microspheres, obtained after vacuum carbonization at 800 °C for 2 h, exhibit outstanding performance at a 30% filler loading, achieving an effective absorption bandwidth of 4.00 GHz (at a matched thickness of 1.6 mm) and a minimum reflection loss of −45.73 dB@4.28 GHz@4.8 mm. The magnetic CNT bridging strategy proposed in this study offers a novel approach for improving the electromagnetic wave absorption performance of macropore carbon materials (such as aerogels and carbon foams).