Enhanced Magnetic Microwave Absorption at Low‐Frequency Band by Ferrite Assembled Microspheres with Controlled Components and Morphologies
Mengqiu Huang, Xue‐Feng Yu, Lei Wang, Ji‐Wei Liu, Wenbin You, Min Wang, Renchao Che
Abstract
Because of the frequency‐dispersion characteristic, electromagnetic wave energy dissipation depends mainly on the magnetic loss at low frequency (S‐band, 2–4 GHz). Herein, a strong magnetic microsphere is constructed via a simple spray drying and subsequent calcination process. With the reaction temperature increasing, the microparticles are forcibly assembled by different contents of ferrite crystallites and Fe metal (mainly containing Fe 2 O 3 , Fe 5 O 12 , FeO, and Fe), accompanying morphology evolution. Attributed to the component and microstructure controlling, the permeability parameters of the heterogeneous ferrite composite microspheres (HFCOMP) can be considerably promoted, contributing to the optimized impedance matching in S‐band. As expected, the maximum reflection loss (RL max ) of HFCOMP is enhanced to −41 dB in S‐band, and the effective absorption bandwidth (EAB) is widened to 1.52 GHz (equivalent to 75% of the S‐band). The HFCOMP can achieve an RL max of −53.5 dB at only 2 mm in X‐band. Observed by electron holography, the series of HFCOMP composites show the visual magnetic coupling effect, which boost the magnetic responding ability. Therefore, this study provides a guideline value for microstructure design in low‐frequency absorption.