Synthesis of Fe3Al@Al2O3 flakes showing improved microwave absorption performance after servicing at high temperatures

Abstract

Most magnetic loss-type absorbers exhibit very poor microwave absorption performance at high temperatures. Herein, we developed a thermal treatment and controlled oxygen partial pressure process to design a Fe3Al@Al2O3 core-shell structure by inducing the in situ oxidation of Al elements in the Fe3Al particles. Owing to the in situ growth of the dense and thin Al2O3 layer on the Fe3Al surface, the oxidation issue at high temeratures can be effectively alleviated. Compared to the Fe3Al counterpart without a Al2O3 shell that tends to be oxidized at high temperatures, the Fe3Al@Al2O3 absorber keeps good microwave attenuation properties and impedance matching ratios even at a temperature of 400 ℃, with the minimum reflection loss of −52.4 dB at 5.8 GHz. Moreover, the effective absorption bandwidth is 4.9 GHz. The new findings demonstrated in this work provides a possible approach for the exploration of efficient microwave absorption materials used at high temperatures.