Breaking bandwidth limit: All-medium metamaterial absorber engineered from heterostructure-anchored N-doped hollow carbon spheres

The composition and structural characteristics of materials significantly influence their ability to absorb electromagnetic waves (EMW). In this research, iron-based heterostructure particles were effectively attached to N-doped hollow carbon spheres (NHCS) through straightforward electrostatic assembly and heat treatment processes, creating a novel composite material (denoted as NHCS@Fe/Fe₃O₄). For samples treated at different annealing temperatures, we use suffixes (e.g., NHCS@Fe/Fe₃O₄-700) to distinguish the specific conditions. This method notably improves the impedance matching characteristics of the as-prepared composites so as to enhance theirs EMW absorption capacity. The effect of NHCS diameter on EMW absorption performance was systematically investigated, and the product, NHCS@Fe/Fe₃O₄-700, with a diameter of 200 nm, exhibited exceptional EMW absorption properties, achieving a minimum reflection loss (RL) of −55.06 dB at 15.12 GHz and an effective absorption bandwidth (EAB) of 6.59 GHz at a matching thickness of 2.37 mm. Additionally, density functional theory (DFT) calculations were conducted to study the electronic properties and polarization behaviors within the NHCS. And an all-medium metamaterial absorber, made up of multi-layered open-ring configuration, was realized through CST simulations, successfully expanding the effective absorption frequency range. Radar cross-section (RCS) simulations further confirmed the application potential of as-prepared composite in real-world. This investigation provides a meaningful perspective and paves a fast route for developing high-performance EMW absorption materials.