Journal of Powder Materials

Dong-Hwan Kim

6 Articles

Effect of Cu Content on Microstructural and Magnetic Properties of a Nd-Fe-B Strip Cast: Song-E Park, Tae-Hoon Kim, Seong-Rae Lee, Dong-Hwan Kim, Seok NamKung, Tae-Suk Jang; J Korean Powder Metall Inst. 2011;18(1):24-28.; DOI: https://doi.org/10.4150/KPMI.2011.18.1.024

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Effect of Cu content on microstructural and magnetic properties of a (Nd_26.06,Dy_6.51)Fe_bal. Cu_xB_0.97(wt.%), (x = 0.2, 0.3, 0.4, 0.5) strip-cast was studied. The average inter-lamellar spacing in the free surface and wheel side of the strip cast increased as the Cu content increases. The grain uniformity, the grain alignment, and (00L) texture of the strip cast increased with Cu contents up to 0.4 wt.%. These microstructural changes were attributed to the decrease of the effective cooling rate of the melted alloy caused by the decrease of the melting temperature of resulting from Cu addition. Coercivity and remanence were increased because of the grain alignment and (00L) texture improvement with Cu contents up to 0.4 wt.%.

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Microstructure and magnetic properties of (Nd,Dy)FeB and (Nd,Pr)FeB strips
Seung-Yeon Park, Jin-Ho Kim, Kyoung-Mook Lim, Sung-Yong Ahn, Kang Ryong Choi, Chul-Sung Kim
Journal of the Korean Physical Society.2015; 66(11): 1755. CrossRef
Effects of the cooling rate on the microstructure of Nd-Fe-B alloys fabricated by strip casting
Kyoung-Mook Lim, Seung-Yeon Park, Sung-Yong Ahn, Chul-Sung Kim
Journal of the Korean Physical Society.2013; 63(6): 1203. CrossRef

A study on Magnetic Properties of BaFe₁₂O₁₉ Fabricated by Ultrasonic Spray-pyrolysis Process Using Self-Assembly Method: Moon-Hee Choi, Ji-Hun Yu, Dong-Hwan Kim, Kook-Chae Chung, Yang-Do Kim; J Korean Powder Metall Inst. 2010;17(4):263-269.; DOI: https://doi.org/10.4150/KPMI.2010.17.4.263

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Hexagonal barium ferrite (BaFe_12O_19) nano-particles have been successfully fabricated by spraypylorysis process. BaFe_12O_19 precursor solutions were synthesized by self-assembly method. Diethyleneamine (DEA) surfactant was used to fabricate the micelle structure of Ba-DEA complex under various DEA concentrations. BaFe_12O_19 powders were synthesized with addition of Fe ions to Ba-DEA complex and then fabricated BaFe_12O_19 powders by spray-pyrolysis process at the temperature range of 800sim1000°C. The molar ratio of Ba/DEA and heat-treatment temperatures significantly affected the magnetic properties and morphology of BaFe_12O_19 powders. BaFe_12O_19 powders synthesized with Ba/DEA molar ratio of 1 and heat-treated at 900°C showed the coercive forces (iHc) of 4.2 kOe with average crystal size of about 100 nm.

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Synthesize of Nd₂Fe₁₄B Powders from 1-D Nd₂Fe₁₄B Wires using Electrospinning Process
Nu Si A Eom, Su Noh, Muhammad Aneeq Haq, Bum Sung Kim
Journal of Korean Powder Metallurgy Institute.2019; 26(6): 477. CrossRef

The Present Issues of Rare Earth Magnetic Powder for Bonded Magnets: Dong-Hwan Kim, Ji-Hun Yu; J Korean Powder Metall Inst. 2010;17(2):81-87.; DOI: https://doi.org/10.4150/KPMI.2010.17.2.081

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Preparation of Highly Efficient Nd-Fe-B Magnetic Powders by Reduction/Diffusion Process
Dongsoo Kim, Chunqiang Chen, Younkyoung Baek, Chuljin Choi
Journal of Korean Powder Metallurgy Institute.2013; 20(3): 197. CrossRef

A Study on Magnetic Properties of BaFe₁₂O_₁₉ Fabricated by Self-assembly Method: Moon-Hee Choi, Ji-Hun Yu, Dong-Hwan Kim, Hye-Mum Lee, Su-Min Kim, Yang-Do Kim; J Korean Powder Metall Inst. 2009;16(6):410-415.; DOI: https://doi.org/10.4150/KPMI.2009.16.6.410

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Hexagonal barium ferrite (BaFe_12O_19) nano-particles have been successfully synthesised using selfassembly method. Diethyleneamine (DEA) surfactant was used to fabricate the micelle structure of Ba-DEA complex under various DEA concentrations. BaFe_12O_19 powders were synthesized with addition Fe ions to Ba-DEA complex and then heat treated at temperature range of 800-1000°C. The molar ratio of Ba/DEA and heat-treatment temperature significantly affected the magnetic properties and morphology of BaFe_12O_19 powders. BaFe_12O_19 powders synthesized with Ba/DEA molar ratio of 1 and heat-treated at 1000°C for 1 hour showed the coercive forces (iHc) of 4.84 kOe with average crystal size of about 200 nm.

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A study on Magnetic Properties of BaFe12O19Fabricated by Ultrasonic Spray-pyrolysis Process Using Self-Assembly Method
Moon-Hee Choi, Ji-Hun Yu, Dong-Hwan Kim, Kook-Chae Chung, Yang-Do Kim
Journal of Korean Powder Metallurgy Institute.2010; 17(4): 263. CrossRef

Microstructure Control and Magnetic Property of Nd-Fe-B Sintered Magnets After Cyclic Heat Treatment: Se-Hoon Kim, Hoon-Sup Kim, Dong-Hwan Kim, Young-Do Kim; J Korean Powder Metall Inst. 2008;15(6):471-476.; DOI: https://doi.org/10.4150/KPMI.2008.15.6.471

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Sintered Nd-Fe-B magnets have been widely used due to their excellent magnetic properties, especially for driving motors of hybrid and electric vehicles. The microstructure of Nd-Fe-B magnets strongly affects their magnetic properties, in particular the coercivity. Therefore, a post-sintering process like heat-treatment is required for improving the magnetic properties of Nd-Fe-B sintered magnets. In this study, cyclic heat treatment was performed at temperatures between 350°C and 450°C up to 16 cycles in order to control microstructures such as size and shape of the Nd-rich phase without grain growth of the Nd_2Fe_14B phase. The 2 cycles specimen at this temperature range showed more homogeneous microstructure which leads to higher coercivity of 35 kOe than as-sintered one.

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Magnetic Properties and Sintering Behavior of (Nd,Dy)-Fe-B Permanent Magnet by Spark Plasma Sintering
Sun-Yong Song, Jin-Woo Kim, Se-Hoon Kim, Young-Do Kim
Journal of Korean Powder Metallurgy Institute.2012; 19(2): 105. CrossRef
Pt and Polymer Electrolyte Membrane Fuel Cell
Hye-Sook Joo, Jung-Yeul Yun, Han-Shin Choi
Journal of Korean Powder Metallurgy Institute.2011; 18(1): 1. CrossRef
The Coercivity Enhancement of (Nd,Dy)-Fe-B Sintered Magnet by Microstructure Control
Jin-Woo Kim, Se-Hoon Kim, Young-Do Kim
Journal of Korean Powder Metallurgy Institute.2011; 18(1): 18. CrossRef
Magnetic properties of high coercivity Nd23Dy10Fe64TM2B1 sintered magnets by a convergent heat treatment
Hoon-sup Kim, Se Hoon Kim, Jin Woo Kim, Young Jung Lee, Dae-Gun Kim, Young Do Kim
Research on Chemical Intermediates.2010; 36(6-7): 859. CrossRef
Coercivity Enhancement of Nd23Dy10Fe64TM2B1Sintered Magnet by Convergent Heat Treatment
Hoon-Sup Kim, Se-Hoon Kim, Jin-Woo Kim, Young-Do Kim
Journal of Korean Powder Metallurgy Institute.2010; 17(1): 1. CrossRef
Effects of thermal stress induced by cyclic heat treatment on sintered (Nd, Dy)-Fe-B magnets
Se Hoon Kim, Hoon-sup Kim, Young Jung Lee, Dae-Gun Kim, Young Do Kim
Metals and Materials International.2010; 16(6): 959. CrossRef

Fabrication of High-performance Carbon Counter Electrode for Dye-sensitized Solar Cells: Yeon-Ik Jang, Seung-Yong Lee, Dong-Hwan Kim, Jong-Ku Park; J Korean Powder Metall Inst. 2007;14(1):44-49.; DOI: https://doi.org/10.4150/KPMI.2007.14.1.044

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Abstract PDF: In the fabrication of dye-sensitized solar cells (DSSCs), carbon counter electrode has been tested for replacing the platinum counter electrode which has two drawbacks: limited surface area and high material cost. Poor mechanical stability of carbon layer due to weak bonding strength to electrically conductive TCO (transparent conducting oxide) glass substrate is a crucial barrier for practical application of carbon counter electrode. In the present study a carbon counter electrode with high conversion efficiency, comparable to Pt counter electrode, could be fabricated by adaption of a bonding layer between particulate carbon material and TCO substrate.

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