Surface Activation and Al2O3 Fluidized Wet-coating of Flaky Magnetic Absorbents

XIONG Yuling; ZHANG Zhe; HU Yuchen; CHEN Zhihong; LIU Jili

doi:10.19554/j.cnki.1001-3563.2025.17.003

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Packaging Engineering ›› 2025, Vol. 46 ›› Issue (17) : 19-29. DOI: 10.19554/j.cnki.1001-3563.2025.17.003

Special Topic on Lightweight Broadband Electromagnetic Composite Materials

Surface Activation and Al₂O₃ Fluidized Wet-coating of Flaky Magnetic Absorbents

XIONG Yuling^a, ZHANG Zhe^a, HU Yuchen^b, CHEN Zhihong^b, LIU Jili^b,*

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Abstract

The work aims to adopt a hydrogen peroxide (H₂O₂) activation strategy to enhance the fluidized wet-coating of Al₂O₃ on flaky FeSiAlCr magnetic absorbents, to reduce dielectric constant, improve impedance matching, and boost low-frequency absorption performance. The optimum conditions for activating absorbents with H₂O₂ were explored by changing the reaction time. The aluminum isopropoxide (AIP) was deposited on the surface of alloy powder via atomization in a wet-coating fluidized bed, followed by hydrolysis and calcination to prepare FeSiAlCr@Al₂O₃ composite absorbents. After being activated by H₂O₂, the absorbents were oxidized, with hydrophilicity enhanced. After the surface was coated with AIP, the powder resistivity increased by three orders of magnitude compared with the original powder, and the real part of the dielectric constant decreased by 30% at 2 GHz. After calcination, the powder achieved five-order-of-magnitude resistivity improvement with 42% dielectric constant reduction while maintaining permeability. After activation, modification and calcination, when the thickness of the composite was 2 mm, the low-frequency absorption performance was significantly enhanced, and the reflectivity was lower than -5 dB in the frequency band of 1.4-3.4 GHz, and the peak reflectivity increased from -6.79 dB to -8.64 dB. Through activation of absorbents with H₂O₂, the effect of dynamic wet-coating of Al₂O₃ with alloy powder is improved by increasing the active sites and defects on the surface of the absorbent, which can effectively reduce the dielectric constant, broaden the low-frequency absorption bandwidth and enhance the low-frequency absorption strength.

Key words

H₂O₂ activation / wet-coating fluidized bed / aluminum isopropoxide / Al₂O₃ coating / dielectric constant

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XIONG Yuling, ZHANG Zhe, HU Yuchen, CHEN Zhihong, LIU Jili. Surface Activation and Al₂O₃ Fluidized Wet-coating of Flaky Magnetic Absorbents[J]. Packaging Engineering. 2025, 46(17): 19-29 https://doi.org/10.19554/j.cnki.1001-3563.2025.17.003

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