Journal of Powder Materials

Jai-Sung Lee

10 Articles

Microstructural Feature of Full-densified W-Cu Nanocomposites Containing Low Cu Content: Jai-Sung Lee, Sung-Soo Jung, Joon-Phil Choi, Geon-Yong Lee; J Powder Mater. 2013;20(2):138-141.; DOI: https://doi.org/10.4150/KPMI.2013.20.2.138

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The microstructure evolution during sintering of the W-5 wt.%Cu nanocomposite powders was investigated for the purpose of developing a high density W-Cu alloy. The W-5 wt.%Cu nanopowder compact, fully-densified during sintering at 1623 K, revealed a homogeneous microstructure that consists of high contiguity structures of W-W grains and an interconnected Cu phase located along the edges of the W grains. The Vickers hardness of the sintered W-5 wt.%Cu specimen was 427pm22 Hv much higher than that (276pm19 Hv) of the conventional heavy alloy. This result is mostly due to the higher contiguity microstructure of the W grains compared to the conventional W heavy alloy.

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Evolution of microstructure and wear-friction behavior of W-30 wt.% Cu nanocomposite produced via a mechanochemical synthesis route
K. Zangeneh-madar, H. Abbaszadeh, E. Salahshour-rad, S. Seyyedin, M. Ahangarkani
International Journal of Materials Research.2020; 111(6): 491. CrossRef
In-situ synthesis of tungsten nanoparticle attached spherical tungsten micro-powder by inductively coupled thermal plasma process
Chulwoong Han, Hyunwoong Na, Yonghwan Kim, Hanshin Choi
International Journal of Refractory Metals and Hard Materials.2015; 53: 7. CrossRef

Consolidation of Iron Nanopowder by Nanopowder-Agglomerate Sintering at Elevated Temperature: Jai-Sung Lee, Joon-Chul Yun, Joon-Phil Choi, Geon-Yong Lee; J Powder Mater. 2013;20(1):1-6.; DOI: https://doi.org/10.4150/KPMI.2013.20.1.001

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The key concept of nanopowder agglomerate sintering (NAS) is to enhance material transport by controlling the powder interface volume of nanopowder agglomerates. Using this concept, we developed a new approach to full density processing for the fabrication of pure iron nanomaterial using Fe nanopowder agglomerates from oxide powders. Full density processing of pure iron nanopowders was introduced in which the powder interface volume is manipulated in order to control the densification process and its corresponding microstructures. The full density sintering behavior of Fe nanopowders optimally size-controlled by wet-milling treatment was discussed in terms of densification process and microstructures.

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Influence of the initial powder characteristic on the densified tungsten microstructure by spark plasma sintering and hot isostatic pressing
Ji Young Kim, Eui Seon Lee, Youn Ji Heo, Young-In Lee, Jongmin Byun, Sung-Tag Oh
Powder Metallurgy.2023; 66(5): 644. CrossRef
Sintering behavior of bimodal iron nanopowder agglomerates
Jun‐ll Song, Geon‐Yong Lee, Eui‐Jin Hong, Carolline S. Lee, Jai‐Sung Lee
Journal of the American Ceramic Society.2019; 102(6): 3791. CrossRef
Fabrication of YAG : Er3+powders for the single crystal growth according to the synthetic temperature and flux concentration
Cheol Woo Park, Suk Hyun Kang, Jae Hwa Park, Hyun Mi Kim, Jae Sang Choi, Hyo Sang Kang, Kwang Bo Shim
Journal of the Korean Crystal Growth and Crystal Technology.2015; 25(4): 166. CrossRef
Consolidation of Hierarchy-Structured Nanopowder Agglomerates and Its Application to Net-Shaping Nanopowder Materials
Jai-Sung Lee, Joon-Phil Choi, Geon-Yong Lee
Materials.2013; 6(9): 4046. CrossRef

A Feasibility Study on the Surface Hardening of Sintered Iron Nanopowder by Plasma Ion Nitriding: Joon-Chul Yun, Jai-Sung Lee; J Korean Powder Metall Inst. 2012;19(1):13-18.; DOI: https://doi.org/10.4150/KPMI.2012.19.1.013

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This study has been performed on the full density sintering of Fe nanopowder and the surface hardening by plasma ion nitriding. The Fe sintered part was fabricated by pressureless sintering of the Fe nanopowder at 700°C in which the nanopowder agglomerates were controlled to have 0.5-5 µm sized agglomerates with 150 nm Fe nanopowders. The green compact with 46% theoretical density(T.D.) showed a homogeneous microstructure with fine pores below 1 µm. After sintering, the powder compact underwent full densification process with above 98%T.D. and uniform nanoscale microstructure. This enhanced sintering is thought to be basically due to the homogeneous microstructure in the green compact in which the large pores are removed by wet-milling. Plasma ion nitriding of the sintered part resulted in the formation of gamma'-Fe_4N equilibrium phase with about 12 µm thickness, leading to the surface hardening of the sintered Fe part. The surface hardness was remarkably increased from 176 H_v for the matrix to 365 H_v.

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Sintering behavior of bimodal iron nanopowder agglomerates
Jun‐ll Song, Geon‐Yong Lee, Eui‐Jin Hong, Carolline S. Lee, Jai‐Sung Lee
Journal of the American Ceramic Society.2019; 102(6): 3791. CrossRef
Densification and microstructural development during sintering of powder injection molded Fe micro–nanopowder
Joon-Phil Choi, Hyun-Gon Lyu, Won-Sik Lee, Jai-Sung Lee
Powder Technology.2014; 253: 596. CrossRef

Surface Roughness and Sintering Characteristics of Fe-8 wt%Ni Component Fabricated by PIM: Berm-Ha Cha, Jai-Sung Lee; J Korean Powder Metall Inst. 2009;16(5):342-350.; DOI: https://doi.org/10.4150/KPMI.2009.16.5.342

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Development of nanoparticulate materials technology is essential to processing of highly functional nanoparticulate materials and components with small and complex shape. In this paper, the effect of particle size on surface roughness and shrinkage of sintered Fe-8 wt%Ni nanopowder components fabricated by PIM were investigated. The Fe-8 wt%Ni nanopowder was prepared by hydrogen reduction of ball-milled Fe_2O_3-NiO powder. Feedstock of nanopowder prepared with the wet-milled powder was injection molded into double gear shaped part at 120°C. After sintering, the sintered part showed near full densified microstructure having apparently no porosity (98%T.D.). Surface roughness of sintered bulk using nanopowder was less than 815 nm and it was about seven times lower than 7 mum that is typically obtainable from a sintered part produced from PIM.

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Opportunity and Challenges of Iron Powders for Metal Injection Molding
Abhijeet Premkumar Moon, Srinivas Dwarapudi, Kameswara Srikar Sista, Deepak Kumar, Gourav Ranjan Sinha
ISIJ International.2021; 61(7): 2015. CrossRef
Densification and microstructural development during sintering of powder injection molded Fe micro–nanopowder
Joon-Phil Choi, Hyun-Gon Lyu, Won-Sik Lee, Jai-Sung Lee
Powder Technology.2014; 253: 596. CrossRef
Consolidation of Hierarchy-Structured Nanopowder Agglomerates and Its Application to Net-Shaping Nanopowder Materials
Jai-Sung Lee, Joon-Phil Choi, Geon-Yong Lee
Materials.2013; 6(9): 4046. CrossRef
Consolidation of Iron Nanopowder by Nanopowder-Agglomerate Sintering at Elevated Temperature
Jai-Sung Lee, Joon-Chul Yun, Joon-Phil Choi, Geon-Yong Lee
Journal of Korean Powder Metallurgy Institute.2013; 20(1): 1. CrossRef
Manufacturing of Micro Gas Bearing by Fe-Ni Nanopowder and Metal Mold Using LIGA
Soo-Jung Son, Young-Sang Cho, Dae-Jung Kim, Jong-Hyun Kim, Suk-Sang Chang, Chul-Jin Choi
Journal of Korean Powder Metallurgy Institute.2012; 19(2): 140. CrossRef

Enhancement of the Light Harvesting of Dye-sensitized Solar Cell by Inserting Scattering Layer: Jung-Gyu Nam, Bum-Sung Kim, Jai-Sung Lee; J Korean Powder Metall Inst. 2009;16(5):305-309.; DOI: https://doi.org/10.4150/KPMI.2009.16.5.305

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Abstract PDF: The effect of light scattering layers (400 nm, TiO_2 particle) of 4 mum thickness on the dye-sensitized solar cell has been investigated with a 12 mum thickness of photo-anode (20 nm, TiO_2 particle). Two different structures of scattering layers (separated and back) were applied to investigate the light transmitting behaviors and solar cell properties. The light transmittance and cell efficiency significantly improved with inserting scattering layers. The back scattering layer structure had more effective transmitting behavior, but separated scattering layer (center: 2 mum, back: 2 mum) structure (9.83% of efficiency) showing higher efficiency (0.6%), short circuit current density (0.26 mA/cm2) and fill factor (0.02). The inserting separating two scattering layers improved the light harvesting, and relatively thin back scattering layer (2 mum of thickness) minimized interruption of ion diffusion in liquid electrolyte.

Trend in Research and Development Related to Sm-Fe-N Bonded Magnets: Jung-Goo Lee, Hun Kwak, Chul-Jin Choi, Joon-Chul Yun, Jai-Sung Lee; J Korean Powder Metall Inst. 2009;16(1):1-8.; DOI: https://doi.org/10.4150/KPMI.2009.16.1.001

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Advanced Magnetic Actuation: Harnessing the Dynamics of Sm2Fe17–xCuxN3 Composites
Kangmo Koo, Young-Tae Kwon, Ji Young Park, Yong-Ho Choa
ACS Applied Materials & Interfaces.2024; 16(9): 11872. CrossRef

Sintering Behavior of Fe Nanopowder Agglomerates Prepared by Pressureless Compaction: Woo-Kyung You, Sung-Soo Jung, Jai-Sung Lee; J Korean Powder Metall Inst. 2008;15(4):271-278.; DOI: https://doi.org/10.4150/KPMI.2008.15.4.271

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Sintering behavior of iron nanopowder agglomerate compact prepared by slurry compaction method was investigated. The Fe nanopowder agglomerates were prepared by hydrogen reduction of spray dried agglomerates of ball-milled Fe_2O_3 nanopowder at various reduction temperatures of 450°C, 500°C and 550°C, respectively. It was found that the Fe nanopowder agglomerates produced at higher reduction temperature have a higher green density compact which consists of more densified nanopowder agglomerates with coarsed nanopowders. The sintering behavior of the Fe nanopowder agglomerates strongly depended on the powder packing density in the compact and microstructure of the agglomerated nanopowder. It was discussed in terms of two sintering factors affecting the entire densification process of the compact.

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A Feasibility Study on the Surface Hardening of Sintered Iron Nanopowder by Plasma Ion Nitriding
Joon-Chul Yun, Jai-Sung Lee
Journal of Korean Powder Metallurgy Institute.2012; 19(1): 13. CrossRef
Low temperature powder injection molding of iron micro-nano powder mixture
Woo-Kyung You, Joon-Phil Choi, Su-Min Yoon, Jai-Sung Lee
Powder Technology.2012; 228: 199. CrossRef

Synthesis of Tungsten Heavy alloy Nanocomposite Powder by Ultrasonic-milling Process: Seung-Chul Lee, Chang-Woo Lee, Sung-Soo Jung, Berm-Ha Cha, Jai-Sung Lee; J Korean Powder Metall Inst. 2007;14(2):101-107.; DOI: https://doi.org/10.4150/KPMI.2007.14.2.101

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Ultrasonic-milling of metal oxide nanopowders for the preparation of tungsten heavy alloys was investigated. Milling time was selected as a major process variable. XRD results of metal oxide nanopowders ultrasonic-milled for 50 h and 100 h showed that agglomerate size reduced with increasing milling time and there was no evidence of contamination or change of composition by impurities. It was found that nanocomposite powders reduced at 800°C in a hydrogen atmosphere showed a chemical composition of 93.1W-4.9Ni-2.0Fe from EDS analysis. Hardness of sintered part using 50 h and 100 h powder samples was 399 Hv and 463 Hv, respectively, which is higher than the that of commercial products (330-340 Hv).

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Grinding behavior of WO3, NiO, Fe2O3 by ultrasonic milling parameters control and preparation of nanocomposite powder
Keunhyuk Ryu, Kun-Jae Lee
Advanced Powder Technology.2020; 31(9): 3867. CrossRef
Investigation on Size Distribution of Tungsten-based Alloy Particles with Solvent Viscosity During Ultrasonic Ball Milling Process
KeunHyuk Ryu, HyeongSub So, JiSeok Yun, InHo Kim, Kun-Jae Lee
Journal of Korean Powder Metallurgy Institute.2019; 26(3): 201. CrossRef

Synthesis of γ-Fe₂O₃ Nanoparticles by Low-pressure Ultrasonic Spraying: Chang-Woo Lee, Soon-Gil Kim, Yong-Ho Choa, Jai-Sung Lee; J Korean Powder Metall Inst. 2007;14(1):19-25.; DOI: https://doi.org/10.4150/KPMI.2007.14.1.019

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Abstract PDF: This study was focused on the optimization of low-pressure ultrasonic spraying process for synthesis of pure gamma-Fe_2O_3 nanoparticles. As process variables, pressure in the reactor, precursor concentration, and reaction temperature were changed in order to control the chemical and microstructural properties of iron oxide nanoparticles including crystal phase, mean particle size and particle size distribution. X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies revealed that pure gamma-Fe_2O_3 nanoparticles with narrow particle size distribution of 5-15 nm were successfully synthesized from iron pentacarbonyl (Fe(CO)_5) in hexane under 30 mbar with precursor concentrations of 0.1M and 0.2M, at temperatures over 800°C. Also magnetic properties, coercivity (H_c) and saturation magnetization (M_s) were reported in terms of the microstructure of particles based on the results from vibration sampling magnetometer (VSM).

Processing of Nano-Sized Metal Alloy Dispersed Al_2O_3 Nanocomposites: Sung-Tag Oh, Namkung Seok, Jai-Sung Lee, Hyoung-Seop Kim, Sekino Tohru; J Korean Powder Metall Inst. 2001;8(3):157-162.

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Abstract PDF: An optimum route to fabricate the ferrous alloy dispersed Al_2O_3 nanocomposites such as Al_2O_3/Fe-Ni and Al_2O_3/Fe-Co with sound microstructure and desired properties was investigated. The composites were fabricated by the sintering of powder mixtures of Al_2O_3 and nano-sized ferrous alloy, in which the alloy was prepared by solution-chemistry routes using metal nitrates powders and a subsequent hydorgen reduction process. Microstructural observation of reduced powder mixture revealed that the Fe-Ni or Fe-Co alloy particles of about 20 nm in size homogeneously surrounded Al_2O_3, forming nanocomposite powder. The sintered Al_2O_3/Fe-Ni composite showed the formation of FeAl_2O_4 phase, while the reaction phases were not observed in Al_2O_3/Fe-Co composite. Hot-pressed Al_2O_3/Fe-Ni composite showed improved mechanical properties and magnetic response. The properties are discussed in terms of microstructural characteristics such as the distribution and size of alloy particles.

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