Journal of Powder Materials

M.K. Lee

4 Articles

Consolidation of Segment Powder for Diamond Tool by Magnetic Pulsed Compaction: J.S. Yun, J.G. Lee, M.K. Lee, C.K. Rhee, M.S. Park, S.J. Hong; J Korean Powder Metall Inst. 2008;15(5):378-385.; DOI: https://doi.org/10.4150/KPMI.2008.15.5.378

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This article presents the successful consolidation of the mixed Co and Diamond powders for a drilling segment by the combined application of magnetic pulsed compaction (MPC) and subsequent sintering, and their properties were analyzed. Homogeneous hardness (Hv 220) and density (97%) of sintered bulks fabricated by MPC were obtained by the new technique, where higher pressure has been employed for short period of time than that of general process. A fine microstructure and homogeneous hardness in the consolidated bulk were observed without cracks. Relatively higher drilling speed of 9.61 cm/min and life time of 6.55 m were found to the MPCed specimens, whereas the value of the specimens fabricated by general process was 11.71 cm/min and 7.96 m, respectively. A substantial improvement of mechanical properties of segment was achieved through this study.

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Machining Characteristics of Micro Structure using Single-Crystal Diamond Tool on Cu-plated Mold
Chang-Eui Kim, Eun-chae Jeon, Tae-Jin Je, Myung Chang Kang
Journal of Korean Powder Metallurgy Institute.2015; 22(3): 169. CrossRef
Comparison of Micro Trench Machining Characteristics with Nonferrous Metal and Polymer using Single Diamond Cutting Tool
Hwan-Jin Choi, Eun-Chae Jeon, Doo-Sun Choi, Tae-Jin Je, Myung-Chang Kang
Journal of Korean Powder Metallurgy Institute.2013; 20(5): 355. CrossRef
Comparison of Machinability Between PCD Tool and SCD Tool for Large Area Mirror Surface Machining Using Multi-tool by Planer
Chang-Eui Kim, Hwan-Jin Choi, Eun-Chae Jeon, Tae-Jin Je, Myung-Chang Kang
Journal of Korean Powder Metallurgy Institute.2013; 20(4): 297. CrossRef
Consolidation of mixed diamond and cobalt granule powders by magnetic pulsed compaction
Jung G. Lee, M.K. Lee, S.J. Hong, H.W. Lee, S.P. Pyun, C.K. Rhee
Materials Letters.2010; 64(1): 35. CrossRef

Densification of Al₂O₃ Nanopowder by Magnetic Pulsed Compaction and Their Properties: R.C. Kang, M.K. Lee, W.W. Kim, C.K. Rhee, S.J. Hong; J Korean Powder Metall Inst. 2008;15(1):37-45.; DOI: https://doi.org/10.4150/KPMI.2008.15.1.037

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This article presents the challenges toward the successful consolidation of Al_2O_3 nanopowder using magnetic pulsed compaction (MPC). In this research the ultrafine-structured Al_2O_3 bulks have been fabricated by the combined application of magnetic pulsed compaction (MPC) and subsequent sintering, and their properties were investigated. The obtained density of Al_2O_3 bulk prepared by the combined processes was increased with increasing MPC pressure from 0.5 to 1.25 GPa. Relatively higher hardness and fracture toughness in the MPCed specimen at 1.25 GPa were attributed to the retention of the nanostructure in the consolidated bulk without cracks. The higher fracture toughness could be attributed to the crack deflection by homogeneous distribution and the retention of nanostructure, regardless of the presence of porosities. In addition, the as consolidated Al_2O_3 bulk using magnetic pulsed compaction showed enhanced breakdown voltage.

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Microstructure and Characteristics of Ag-SnO2Contact Materials Prepared by Magnetic Pulsed Compaction
J.S. Park, Y.J. Kim, M.H. Lee, H.S. Lee, S.J. Hong, J.K. Lee
Journal of Korean Powder Metallurgy Institute.2011; 18(4): 372. CrossRef
The Effect of Ti Powder addition on Compaction Behavior of TiO2Nano Powder
Jin-Sub Park, Hyo-Seob Kim, Ki-Seok Lee, Jeong-Goo Lee, Chang-Kyu Rhee, Soon-Jik Hong
Journal of Korean Powder Metallurgy Institute.2009; 16(3): 223. CrossRef

An Investigation of Dispersion Behavior of Y₂O₃ Ceramic Particles in Hypo, Eutectic and Hyper Binary Al-Cu Cast Alloys: J.J. Park, G.H. Kim, S.M. Hong, S.H. Lee, M.K. Lee, C.K. Rhee; J Korean Powder Metall Inst. 2007;14(2):123-126.; DOI: https://doi.org/10.4150/KPMI.2007.14.2.123

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Abstract PDF: In this work, the dispersion behavior of Y_2O_3 particles in binary aluminum (Al)-copper (Cu) cast alloy was investigated with respect to Cu contents of 20 (hypoeutertic), 33 (eutectic) and 40 (hypereutectic) wt.%. In cases of hypo and hypereutectic compositions, SEM images revealed that the primary Al and theta phases were grown up at the beginning, respectively, and thereafter the eutectic phase was solidified. In addition, it was found that some of Y_2O_3 particles can be dispersed into the primary Al phase, but none of them are is observed inside the primary 6 phase. This different dispersion behavior of Y_2O_3 particles is probably due to the difference in the val- ues of specific gravity between Y_2O_3 particles and primary phases. At eutectic composition, Y_2O_3 particles were well dispersed in the matrix since there is few primary phases acting as an impediment site for particle dispersion during solidification. Based on the experimental results, it is concluded that Y_2O_3 particles are mostly dispersed into the eutectic phase in binary Al-Cu alloy system.

A study on the Particulate Properties of Ti-Ni alloy Nanopowders Prepared by Levitational Gas Condensation Method: B.S. Han, Y.R. Uhm, M.K. Lee, G.M. Kim, C.K. Rhee; J Korean Powder Metall Inst. 2006;13(6):396-400.; DOI: https://doi.org/10.4150/KPMI.2006.13.6.396

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Abstract PDF: The Ti-Ni alloy nanopowders were synthesized by a levitational gas condensation (LGC) by using a micron powder feeding system and their particulate properties were investigated by x-ray diffraction (XRD), transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) method. The starting Ti and Ni micron powders 150µm were incorporated into the micron powder feeding system. An ingot type of the Ti-Ni ahoy was used as a seed material for the levitation and evaporation reactions. The collected powders were finally passivated by oxidation. The x-ray diffraction experiments have shown that the synthesized powders were completely alloyed with Ti and Ni and comprised of two different cubic and monoclinic crystalline phases. The TEM results showed that the produced powders were very fine and uniform with a spherical particle size of 18 to 32nm. The typical thickness of a passivated oxide layer on the particle surface was about 2 to 3 nm. The specific surface area of the Ti-Ni alloy nanopowders was 60m2/g based on BET method.

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