Core-shell Al2O3@carbonyl iron powders (CIPs) were prepared by ball-milling-in-situ oxidation method. The phase composition, mass change and micromorphology of Al2O3@CIPs were analyzed by X-ray diffraction, thermogravimetric analyzer and scanning electron microscopy. The effects of various oxidation temperature on electromagnetic properties and absorbing performance of Al2O3@CIPs were studied. The results show that, as the oxidation temperature increases, the shell of Al2O3@CIPs is damaged to some extent and accompanied by the formation of iron oxides, its permittivity rises first and then declines, while permeability shows a downward trend. Compared with CIPs, Al2O3@CIPs obtained by in-situ oxidation at 400℃ achieve excellent electromagnetic wave absorption performance.The real part of the permittivity is about 15, and the imaginary part is 2.8-4.3. The effective absorption band (< -10 dB) of 3.4 GHz can be obtained under the thickness of 1.8 mm in the X-band, while the Al2O3@CIPs obtained by in-situ oxidation at 450℃ achieve the maximum reflection loss of -30 dB at 11.1 GHz.
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