| Magnetic metal nanoparticles exhibit excellent microwave absorption properties. However, because of their extremely small particle size, they are easily suffered from agglomeration and oxidation, so their electromagnetic properties are weakened. In this paper, the nano-Fe/Al2O3 composite particles were prepared from the powder mixture of Al and Fe3O4 by mechanochemical method. Nano-Fe particles were homogeneously dispersed non-magnetic and insulated Al2O3 matrix.The ball milling parameters were determined according to pre-experiment. The phase constitutions of composite particles milled for different time were studied by X-ray diffraction. Then the physicochemical changes were discussed. Theα-Fe particle sizes of composite particles milled for different time were calculated by Scherrer equation.The composite particles were observed by TEM. The TEM results indicated that the Fe size was nano-class in which composite particles prepared by mechanochemical method. Thermogravity was employed to characterize the oxidation resistance of the composite particles under air atmosphere at room temperature. Based on the TG result, the content ofα-Fe phase involved in the core-shell structured composite particles was calculated. Size distribution of composite particles was characterized by using laser particle sizer and scanning electron microscope.Vibrating sample magnetometer was used to measure magnetic parameters of the composite particles milled for different time such as coercivity Hc, saturated magnetization Ms, squareness Mr/Ms, tec. The change tendency of magnetic properties as the change of milling time was studied from microstructure.The electromagnetic parameters of composite particles milled different time were measured by vector network analyzer. Then the microwave absorption parameters of samples were calculated. The microwave absorption properties change of composite particles milled different time was studied by VNA with XRD and TEM. The microwave absorption mechanism of composite particles with core-shell structure was discussed then.
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