Understanding the efficient microwave absorption for Fe Co@ZnO flakes at elevated temperatures a combined experimental and theoretical approach

Considerable microwave absorption performance at elevated temperatures is highly demanded in both civil and military fields.Single dielectric or magnetic absorbers are difficult to attain efficient and broadband microwave absorption at the high temperature range of 373 K-573 K,and the evolution mechanism of the microwave absorption is still unclear especially for the magnetic absorbers.Herein,ZnO coated flaky-FeCo composite is proposed to break through the bottleneck,which possesses microwave absorption(RL<-10 dB)that covering the whole X band(8.2 GHz-12.4 GHz)at the temperature range of 298 K-573 K with a thickness of only~2 mm.Moreover,attenuation mechanism and evolution of the microwave absorption properties for the FeCo@ZnO flaky material at elevated temperature has been clearly disclosed by the composition and microstructure characterizations,electromagnetic performance measurements and first principles calculations for the first time.Moreover,the Poynting vector,volume loss density,magnetic field(H)and electric field(E)are simulated by HFSS to understand the interaction between EM waves and the samples at different temperatures,further elaborating the attenuation mechanism in high-temperature environment.This study provides guidance in designing and developing high-temperature microwave absorbers for the next generation.