The new insight into the microscopic enhancement mechanism of microwave absorption based on the electromagnetic heterogeneous interface of carbon nanocavity.

Reasonable microstructure design is an effective strategy to obtain high-efficiency microwave absorbers. The current explanation for the mechanism of microwave absorption enhancement by microstructures is limited to impedance matching and attenuation constant variation, which lacks a more intuitive understanding. To investigate the microwave absorption enhancement mechanisms arising from hollow structural features and heterointerfaces, a N-doped carbon framework with hollow cavities (H-NC) and embedded iron nanoparticles (H-NC/Fe) was strategically designed and synthesized. Notably, the optimized H-NC/Fe-2 composite demonstrates an extended effective absorption bandwidth (EAB) of 7.1 GHz (10.9-18.0 GHz). Experimental results and numerical simulations demonstrate that the enhancement of the effective medium and the establishment of the inhomogeneous interface caused by the cavity structure promote electron migration. The heterogeneous interface caused by magnetic particle loading effectively regulates the electron transport efficiency in the composite material, and changes the induced electric field strength and displacement current density in the composite material. This study integrates numerical simulations with experimental validation, establishing a coherent physical model that bridges critical theoretical gaps in conventional electromagnetic composites, and put new insight into the impact of micro-cavity structure and heterogeneous interface on the microwave response mechanism.