Journal of Powder Materials

Myung-Jin Suk

5 Articles

Freeze Drying for Porous Mo with Sublimable Vehicles of Eutectic System: Gyu-Tae Lee, Han Gil Seo, Myung-Jin Suk, Sung-Tag Oh; J Powder Mater. 2013;20(4):253-257.; DOI: https://doi.org/10.4150/KPMI.2013.20.4.253

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Freeze drying for porous Mo was accomplished by using MoO_3 powder as the source and camphor-naphthalene eutectic system as the sublimable material. Eutectic composition of camphor-naphthalene slurries with the initial MoO_3 content of 5 vol%, prepared by milling at 55°C with a small amount of oligomeric dispersant, was frozen at -25°C. The addition of dispersant showed improvement of dispersion stability in slurries. Pores were generated subsequently by sublimation of the camphor-naphthalene during drying in air for 48 h. To convert the MoO_3 to metallic Mo, the green body was hydrogen-reduced at 750°C, and sintered at 1100°C for 2 h. The sintered samples, frozen by heated Teflon cylinder, showed large pores with the size of about 40 µm which were aligned parallel to the sublimable vehicles growth direction. The formation of unidirectionally aligned pores is explained by the rejection and accumulation of solid particles in the serrated solid-liquid interface.

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Interaction of Solid Particles with the Solidifying Front in the Liquid-Particle Mixture
Ho-Suk Lee, Kyu-Hee Lee, Sung-Tag Oh, Young Do Kim, Myung-Jin Suk
Journal of Korean Powder Metallurgy Institute.2018; 25(4): 336. CrossRef
Freeze drying for porous Mo with different sublimable vehicle compositions in the camphor-naphthalene system
Sung-Tag Oh, Young Do Kim, Myung-Jin Suk
Materials Letters.2015; 139: 268. CrossRef

Fabrication of Porous Cu by Freeze-Drying Method of CuO-Camphene Slurry: Min-Soo Kim, Sung-Tag Oh, Si-Young Chang, Myung-Jin Suk; J Korean Powder Metall Inst. 2011;18(4):327-331.; DOI: https://doi.org/10.4150/KPMI.2011.18.4.327

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In order to fabricate the porous metal with controlled pore characteristics, unique processing by using metal oxide powder as the source and camphene as the sublimable material is introduced. CuO powder was selected as the source for the formation of Cu metal via hydrogen reduction. Camphene-based CuO slurry, prepared by milling at 47°C with a small amount of dispersant, was frozen at -25°C. Pores were generated subsequently by sublimation of the camphene. The green body was hydrogen-reduced at 200°C for 30 min, and sintered at 500-700°C for 1 h. Microstructural analysis revealed that the sintered Cu showed aligned large pore channels parallel to the camphene growth direction, and fine pores are formed around the large pore. Also, it showed that the pore size was controllable by the slurry concentration.

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Freeze drying for porous Mo with different sublimable vehicle compositions in the camphor-naphthalene system
Sung-Tag Oh, Young Do Kim, Myung-Jin Suk
Materials Letters.2015; 139: 268. CrossRef
Effect of Solidification Condition of Sublimable Vehicles on the Pore Characteristics in Freeze Drying Process
Myung-Jin Suk, Ji Soon Kim, Sung-Tag Oh
Journal of Korean Powder Metallurgy Institute.2014; 21(5): 366. CrossRef
Synthesis and Microstructure of Porous Al2O3 with Nano-Sized Cu Dispersions
호석 유, 창용 현, 안기 김
Korean Journal of Materials Research.2013; 23(1): 67~71. CrossRef
Effect of Powder Characteristic and Freeze Condition on the Pore Characteristics of Porous W
Na-Yeon Kwon, Sung-Tag Oh
Journal of Korean Powder Metallurgy Institute.2012; 19(4): 259. CrossRef
Fabrication of Porous Mo by Freeze-Drying and Hydrogen Reduction of MoO3/Camphene Slurry
Wonsuk Lee, Sung-Tag Oh
Journal of Korean Powder Metallurgy Institute.2012; 19(6): 446. CrossRef
Fabrication and Properties of Porous Tungsten by Freeze-Drying Process
영숙 이, 승탁 오
Korean Journal of Materials Research.2011; 21(9): 520~524. CrossRef

Fabrication of Ultra Fine Grained Molybdenum and Mechanical Properties: Se-Hoon Kim, Young-Ik Seo, Dae-Gun Kim, Myung-Jin Suk, Young-Do Kim; J Korean Powder Metall Inst. 2010;17(3):235-241.; DOI: https://doi.org/10.4150/KPMI.2010.17.3.235

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Abstract PDF: Mo nanopowder was synthesized by ball-milling and subsequent hydrogen-reduction of MoO_3 powder. To fabricate ultra fine grained molybdenum, two-step sintering and spark plasma sintering process were employed. The grain size of specimen by two-step sintering and spark plasma sintering was around 0.6;µm and 0.4;µm, respectively. Mechanical properties of ultra fine grained Mo with relative density of above 90% were significantly improved at room and high temperatures comparing to commercial bulk Mo of 99% relative density. This result was mainly explained by the grain size refinement due to diffusion-controlled sintering.

Warm Compaction of Fe-Si/Fe Powder Mixture and its Magnetic Property: Se-Hoon Kim, Myung-Jin Suk, Young-Do Kim; J Korean Powder Metall Inst. 2009;16(4):249-253.; DOI: https://doi.org/10.4150/KPMI.2009.16.4.249

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Abstract PDF: 3-D shape soft magnetic composite parts can be formed by general compaction method of powder metallurgy. In this study, the results on the high density nanostructured Fe-Si/Fe composite prepared by a warm compaction method were presented. Ball-milled Fe-25 wt.%Si powder, pure Fe powder and Si-polymer were mixed and then the powder mixture was compacted at various temperatures and pressures. Pore free density of samples up to 95% theoretical value has been obtained. The warm compacted sample prepared at 650 MPa and 240°C had highest compaction properties in comparison with other compacts prepared at 300, 400 MPa and room temperature and 120°C. The magnetic properties such as core loss, magnetization saturation and coercivity were measured by B-H curve analyzer and vibration sample magnetometer.

Sintering Behavior and Mechanical Property of Mo Nanopowders: Hai-Gon Kim, Gil-Su Kim, Sung-Tag Oh, Myung-Jin Suk, Young-Do Kim; J Korean Powder Metall Inst. 2007;14(6):386-390.; DOI: https://doi.org/10.4150/KPMI.2007.14.6.386

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Abstract PDF: The sintering behavior and mechanical property of Mo nanopowder was investigated as a function of various sintering condition. Mo oxide nanopowders were milled using a high energy ball-milling process. After the ball milling for 20h, the crystalline size of MoO_3 was about 20 nm. The MoO_3 nanopowders were reduced at the temperature of 800°C without holding time in H_2 atmosphere. The sinterability of Mo nanopowder and commercial Mo powder was investigated by dilatometric analysis. Mo nanopowder and commercial Mo powder were sintered at 1200°C for 1 hand 1500°C for 3 h, respectively. In both specimens the measured relative density was about 95%. But the measured hardness values were 2.34 GPa for nanopowder and 1.87 GPa for commercial powder. Probably due to finer grain size of the sintered body prepared from Mo nanopowder than that prepared using commercial Mo powder. The mean grain sizes were measured to be about 1.4 mm and 6.2 mm, respectively.

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