Journal of Powder Materials

Mi-Rae Kim

4 Articles

The Characteristic Changes of Electromagnetic Wave Absorption in Fe-based Nanocrystalline P/M Sheets Mixed with Ball-Milled Carbon Nanotubes: Sun-I Kim, Mi-Rae Kim, Keun-Yong Sohn, Won-Wook Park; J Korean Powder Metall Inst. 2009;16(6):424-430.; DOI: https://doi.org/10.4150/KPMI.2009.16.6.424

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Electromagnetic wave energies are consumed in the form of thermal energy, which is mainly caused by magnetic loss, dielectric loss and conductive loss. In this study, CNT was added to the nanocrystalline soft magnetic materials inducing a high magnetic loss, in order to improve the dielectric loss of the EM wave absorption sheet. Generally, the aspect ratio and the dispersion state of CNT can be changed by the pre-ball milling process, which affects the absorbing properties. After the various ball-milling processes, 1wt% of CNTs were mixed with the nanocrystalline Fe_73Si_16B_7Nb_3Cu_1 base powder, and then further processed to make EM absorption sheets. As a result, the addition of CNT to Fe-based nanocrystalline materials improved the absorption properties. However, the increase of ball-milling time for more than 1h was not desirable for the powder mixture, because the ballmilling caused the shortening of CNT length and the agglomeration of the CNT flakes.

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Annealing effect on microstructure and magnetic properties of flake-shaped agglomerates of Ni–20wt%Fe nanopowder
Geon-Yong Lee, Sang-Kyun Kwon, Jai-Sung Lee
Journal of Alloys and Compounds.2014; 613: 164. CrossRef

Electromagnetic Wave Absorption Properties of Fe₇₃Si₁₆B₇Nb₃Cu₁-Based Nanocrystalline Soft Magnetic Powder Composite Mixed with Charcoal Powder: Sun-I Kim, Mi-Rae Kim, Keun-Yong Sohn, Won-Wook Park; J Korean Powder Metall Inst. 2009;16(4):291-295.; DOI: https://doi.org/10.4150/KPMI.2009.16.4.291

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The electromagnetic wave absorption sheets were fabricated by mixing of Fe_73Si_16B_7Nb_3Cu_1 nanocrystalline soft magnetic powder, charcoal powder and polymer based binder. The complex permittivity, complex permeability, and scattering parameter have been measured using a network analyzer in the frequency range of 10 MHzsim10 GHz. The results showed that complex permittivity of sheets was largely dependent on the frequency and the amount of charcoal powder : The permittivity was improved up to 100 MHz, however the value was decreased above 1 GHz. The power loss of electromagnetic wave absorption data showed almost the same tendency as the results of complex permittivity. However, the complex permeability was not largely affected by the frequency, and the values were decreased with the addition of charcoal powder. Based on the results, it can be summarized that the addition of charcoal powder was very effective to improve the EM wave absorption in the frequency range of 10 MHzsim1 GHz.

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The Characteristic Changes of Electromagnetic Wave Absorption in Fe-based Nanocrystalline P/M Sheets Mixed with Ball-Milled Carbon Nanotubes
Sun-I Kim, Mi-Rae Kim, Keun-Yong Sohn, Won-Wook Park
Journal of Korean Powder Metallurgy Institute.2009; 16(6): 424. CrossRef

Electromagnetic Wave Absorption Properties in Fe-based Nanocrystalline P/M Sheets with Carbon Black and BaTiO₃ Additives: Mi-Rae Kim, Won-Wook Park; J Korean Powder Metall Inst. 2009;16(1):33-36.; DOI: https://doi.org/10.4150/KPMI.2009.16.1.033

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In order to increase the magnetic loss for electromagnetic(EM) wave absorption, the soft magnetic Fe_73Si_16B_7Nb_3Cu_1(at%) alloy strip was used as the basic material in this study. The melt-spun strip was pulverized using an attrition mill, and the pulverized flake-shaped powder was crystallized at 540°C for 1h to obtain the optimum grain size. The Fe-based powder was mixed with 2 wt% BaTiO_3, 0.3sim0.6 wt% carbon black, and polymer-based binders for the improvement of electromagnetic wave absorption properties. The mixture powders were tape-cast and dried to form the absorption sheets. After drying at 100°C for 1h, the sheets of 0.5 mm in thickness were made by rolling at 60°C, and cut into toroidal shape to measure the absorption properties of samples. The characteristics including permittivity, permeability and power loss were measured using a Network Analyzer(N5230A). Consequently, the properties of electromagnetic wave absorber were improved with the addition of both BaTiO_3 and carbon black powder, which was caused by the increased dielectric loss of the additive powders.

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Synthesis of Fe(Ni) nanoparticles by calcination and hydrogen reduction of metal nitrate powders
Sung-Tag Oh, Min-Hee Joo, Yong-Ho Choa, Ki Hyeon Kim, Sang-Kwan Lee
Physica Scripta.2010; T139: 014050. CrossRef
Synthesis and Properties of Fe-Ni Nano-sized Powders using Metal Nitrates
Min-Hee Joo, Sung-Tag Oh
Journal of Korean Powder Metallurgy Institute.2009; 16(3): 191. CrossRef

The Characteristic Changes of Electromagnetic Wave Absorption in Fe-based Nanocrystalline P/M Sheet by the Additions of BaTiO₃ Powder and Dispersant: Mi-Rae Kim, Hyeon-Jeong Cho, Won-Wook Park; J Korean Powder Metall Inst. 2008;15(1):53-57.; DOI: https://doi.org/10.4150/KPMI.2008.15.1.053

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The amorphous Fe_73Si_16B_7Nb_3Cu_1(at%) alloy strip was pulverized using a jet mill and an attrition mill to get flake-shaped powder. The flake powder was mixed with dielectric BaTiO_3 powder and its dispersant to increase the permittivity. The powders covered with dielectric powders and its dispersant were mixed with a binder and a solvent and then tape-cast to form sheets. The absorbing properties of the sheets were measured to investigate the roles of the dielectric powder and its dispersant. The results showed that the addition of BaTiO_3 powders and its dispersant improved the absorbing properties of the sheets noticeably. The powder sheet mixed with 5 wt% of BaTiO_3 powder and 1 wt% of dispersant showed the best electromagnetic wave absorption rate because of the increase of the permittivity and the electrical resistance.

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Effects of various barium titanate additives on the electromagnetic wave absorbing behavior of FeSiBNbCu P/M sheets
S J Woo, S I Kim, M R Kim, K Y Sohn, Y S Song, W W Park
Journal of Physics: Conference Series.2009; 144: 012061. CrossRef
The Effect of Carbon Black Additions on Electromagnetic Wave Absorption of Fe73Si16B7Nb3Cu1 Base P/M Sheets
Sun-I Kim, K. Y. Sohn, W. W. Park
MRS Proceedings.2008;[Epub] CrossRef

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