- Effect of the Surface Oxidation on the Electromagnetic Wave Absorption Behavior of a Fe-based Nanocrystalline Alloy
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S.K. Koo, S.J. Woo, B.G. Moon, Y.S. Song, W.W. Park, K.Y. Sohn
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J Korean Powder Metall Inst. 2007;14(5):303-308.
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DOI: https://doi.org/10.4150/KPMI.2007.14.5.303
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 Abstract
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- The oxidation of Fe_73Si_16B_7Nb_3Cu_1 nanocrystalline powder has been conducted to investigate its influence on the electromagnetic wave absorption characteristics of the soft magnetic material. Oxidation occurred primarily on the surface of nanocrystals. Oxidation reduced the real part of complex permeability due to the reduction of the relative volume of the powder, which otherwise contributes to the permeability. Oxidation reduced the absorption efficiency of the sheet at frequencies over 1GHz, indicating that the relative contribution of skin depth increments to the absorption was not significant. The pulverization and milling process lowered the optimum crystallization temperature of the material by 40sim50°C because of the internal energy accumulated during the fragmentation and powder thinning processes.
- Electromagnetic Wave Absorption Properties of Fe-based Nanocrystalline P/M sheets with Al2O3 additive
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S.J. Woo, E.K. Cho, H.J. Cho, J.J. Lee, K.Y. Sohn, W.W. Park
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J Korean Powder Metall Inst. 2007;14(4):265-271.
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DOI: https://doi.org/10.4150/KPMI.2007.14.4.265
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Abstract
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- Electromagnetic wave absorbing materials have been developed to reduce electromagnetic interference (EMI) for electronic devices in recent years. In this study, Fe-Si-B-Nb-Cu base amorphous strip was pulverized using a jet mill and an attritor and heat-treated to get flake-shaped nanocrystalline powders, and then the powders were mixed, cast and dried with dielectric Al_2O_3 powders and binders. As a result, the addition of Al_2O_3 powders improved the absorbing properties of the sheets noticeably compared with those of the sheets without dielectric materials. The sheet mixed with 2 wt% Al_2O_3 powder showed the best electromagnetic wave absorption, which was caused by the increase of the permittivity and the electric resistance due to the dielectric materials finely dispersed on the Fe-based powder.
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