A ZrO₂-wrapped FeSiAl composite with a cotton-like structure for broadband electromagnetic wave absorption

In addition to enhancing impedance matching characteristics, rational structural design can facilitate the absorption of broadband electromagnetic (EM) waves. In this work, ZrO₂@FeSiAl composites with a cotton-like structure were prepared through chemical precipitation and heat treatment. With increasing ZrOCl₂ content, the chain-like structure gradually evolves into a cotton-like morphology, which not only enhances impedance matching but also enhances dielectric losses due to the introduction of nano-heterogeneous interfaces and defects. At a ZrOCl₂ content of 4 wt%, the ZrO₂@FeSiAl composites demonstrated a minimum reflection loss (RL_min) of -19.4 dB at 1.85 mm and a maximum effective absorption bandwidth (EAB) of 9.4 GHz, spanning the C-band (5.1–8 GHz) and the X and Ku-bands (11.5–18 GHz). This outstanding broadband EM wave absorption performance arises from the combined effects of dielectric losses and magnetic losses. This achievement sets the stage for the development of FeSiAl-based composites with broadband EM wave absorption capabilities.