Journal of Powder Materials

[Korean]
Interfacial Reaction between Spark Plasma Sintered High-entropy Alloys and Cast Aluminum: Min-Sang Kim, Hansol Son, Cha Hee Jung, Juyeon Han, Jung Joon Kim, Young-Do Kim, Hyunjoo Choi, Se Hoon Kim; J Powder Mater. 2022;29(3):213-218. Published online June 1, 2022; DOI: https://doi.org/10.4150/KPMI.2022.29.3.213

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This study investigates the interfacial reaction between powder-metallurgy high-entropy alloys (HEAs) and cast aluminum. HEA pellets are produced by the spark plasma sintering of Al_0.5CoCrCu_0.5FeNi HEA powder. These sintered pellets are then placed in molten Al, and the phases formed at the interface between the HEA pellets and cast Al are analyzed. First, Kirkendall voids are observed due to the difference in the diffusion rates between the liquid Al and solid HEA phases. In addition, although Co, Fe, and Ni atoms, which have low mixing enthalpies with Al, diffuse toward Al, Cu atoms, which have a high mixing enthalpy with Al, tend to form Al–Cu intermetallic compounds. These results provide guidelines for designing Al matrix composites containing high-entropy phases.

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Simultaneous enhancement of strength and ductility of Al matrix composites enabled by submicron-sized high-entropy alloy phases
Chahee Jung, Seungin Nam, Hansol Son, Juyeon Han, Jaewon Jeong, Hyokyung Sung, Hyoung Seop Kim, Seok Su Sohn, Hyunjoo Choi
Journal of Materials Research and Technology.2024; 33: 1470. CrossRef

[Korean]
Fabrication of Porous Al₂O₃ Film by Freeze Tape Casting: Ran-Hee Shin, Jun-Mo Koo, Young-Do Kim, Yoon-Soo Han; J Korean Powder Metall Inst. 2015;22(6):438-442. Published online December 1, 2015; DOI: https://doi.org/10.4150/KPMI.2015.22.6.438

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Abstract PDF: Porous thick film of alumina which is fabricated by freeze tape casting using a camphene-camphor-acrylate vehicle. Alumina slurry is mixed above the melting point of the camphene-camphor solvent. Upon cooling, the camphene-camphor crystallizes from the solution as particle-free dendrites, with the Al₂O₃ powder and acrylate liquid in the interdendritic spaces. Subsequently, the acrylate liquid is solidified by photopolymerization to offer mechanical properties for handling. The microstructure of the porous alumina film is characterized for systems with different cooling rate around the melting temperature of camphor-camphene. The structure of the dendritic porosity is compared as a function of ratio of camphene-camphor solvent and acrylate content, and Al₂O₃ powder volume fraction in acrylate in terms of the dendrite arm width.

[Korean]
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; J Korean Powder Metall Inst. 2012;19(2):105-109.; DOI: https://doi.org/10.4150/KPMI.2012.19.2.105

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Magnetic properties and the microstructures of magnets prepared by spark plasma sintering were investigated in order to enhance magnetic properties by grain size control. Nd-Fe-B magnets were fabricated by the spark plasma sintering under 30 MPa at various temperatures. The grain size was effectively controlled by the spark plasma sintering and it was possible to make Nd-Fe-B magnets with grain size of 5.9 µm.

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Development of Fe-Mn-based Hybrid Materials Containing Nano-scale Oxides by a Powder Metallurgical Route
Jonggyu Jeon, Jungjoon Kim, Hyunjoo Choi
Journal of Korean Powder Metallurgy Institute.2020; 27(3): 203. CrossRef

[Korean]
Synthesis of Platinum Nanoparticles by Liquid Phase Reduction: Jin-Ho Lee, Se-Hoon Kim, Jin-Woo Kim, Min-Ha Lee, Young-Do Kim; J Korean Powder Metall Inst. 2012;19(1):60-66.; DOI: https://doi.org/10.4150/KPMI.2012.19.1.060

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In this study, Platinum(Pt) nanoparticles were synthesized by using polyol process which is one of the liquid phase reduction methods. Dihydrogen hexachloroplatinate (IV) hexahydrate (H_2PtCl_6cdot6H_2O), as a precursor, was dissolved in ethylene glycol and silver nitrate (AgNO_3) was added as metal salt for shape control of Pt particle. Also, polyvinylpyrrolidone (PVP), as capping agent, was added to reduce the size of particle and to separate the particles. The size of Pt nanoparticles was evaluated particle size analyzer (PSA). The size and morphology of Pt nanoparticles were observed by transmission electron microscopy (TEM) and high resolution TEM (HRTEM). Synthesized Pt nanoparticles were studied with varying time and temperature of polyol process. Pt nanoparticles have been successfully synthesized with controlled sizes in the range 5-10 and 20-40 nm with cube and multiple-cube shapes.

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Facile Strategy for Mass Production of Pt Catalysts for Polymer Electrolyte Membrane Fuel Cells Using Low-Energy Electron Beam
Jongmin Shin, Jiho Min, Youngjin Kim, Jin Hee Lee, Geunseok Chai, Namgee Jung
Nanomaterials.2020; 10(11): 2216. CrossRef
Synthesis of Nanosized Nickel Particle from Spent Cathodic Material Containing Lithium
Jei-Pil Wang
Journal of Korean Powder Metallurgy Institute.2019; 26(4): 340. CrossRef
Fabrication and Characterization of Ag Particles by Polyol Process and Wet Chemical Process
Juyeon Yoo, Hyosung Jang, Kun-Jae Lee
Journal of Korean Powder Metallurgy Institute.2016; 23(4): 297. CrossRef

[Korean]
Densification and Microstructure of Ultrafine-sized AlN Powder Prepared by a High Energy Ball Milling Process: Hae-Ryong Park, Young-Do Kim, Sung-Soo Ryu; J Korean Powder Metall Inst. 2012;19(1):25-31.; DOI: https://doi.org/10.4150/KPMI.2012.19.1.025

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Abstract PDF: In this study, a high energy ball milling process was employed in order to improve the densification of direct nitrided AlN powder. The densification behavior and the sintered microstructure of the milled AlN powder were investigated. Mixture of AlN powder doped with 5 wt.% Y_2O_3 as a sintering additive was pulverized and dispersed up to 50 min in a bead mill with very small ZrO_2 beads. Ultrafine AlN powder with a particle size of 600 nm and a specific surface area of 9.54 m2/g was prepared after milling for 50 min. The milled powders were pressureless-sintered at 1700°C-1800°C for 4 h under N_2 atmosphere. This powder showed excellent sinterability leading to full densification after sintering at 1700°C for 4 h. However, the sintered microstructure revealed that the fraction of yitttium aluminate increased with milling time and sintering temperature and the newly-secondary phase of ZrN was observed due to the reaction of AlN with the ZrO_2 impurity.

[Korean]
Fabrication of Gradient Porous Al-Cu Sintered Body: Jong-Min Byun, Se-Hoon Kim, Jin-Woo Kim, Young-Moon Kim, Young-Do Kim; J Korean Powder Metall Inst. 2011;18(4):365-371.; DOI: https://doi.org/10.4150/KPMI.2011.18.4.365

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Abstract PDF: In this study, gradient porous Al-Cu sintered body was fabricated by powder metallurgy processing. Al-Cu powder mixtures were prepared by low energy ball milling with various milling time. After ball milling for 3h, the shape of powder mixtures changed to spherical type with size of 100~500 µm. Subsequently, Al-Cu powder mixtures were classified (under 150, 150~300 and over 300 µm) and compacted (20, 50 and 100 MPa). Then, they were sintered at 600°C for various holding time (10, 30, 60 and 120 min) in N_2 atmosphere. The sintered bodies had 32~45% of porosity. As a result, the optimum holding time was determined to be 60 min at 600°C and sintered bodies with various porosity were obtained by controlling the compacting pressure.

[Korean]
Fabrication and Dynamic Consolidation Behaviors of Rapidly Solidified Mg Alloy Powders: Hong-Jun Chae, Young-Do Kim, Taek-Soo Kim; J Korean Powder Metall Inst. 2011;18(4):340-346.; DOI: https://doi.org/10.4150/KPMI.2011.18.4.340

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Abstract PDF: In order to improve the weak mechanical properties of cast Mg alloys, Mg-Zn_1Y_2 (at%) alloy powders were synthesized using gas atomization, a typical rapid solidification process. The powders consist of fine dendrite structures less than 3 µm in arm spacing. In order to fabricate a bulk form, the Mg powders were compacted using magnetic pulse compaction (MPC) under various processing parameters of pressure and temperature. The effects of the processing parameters on the microstructure and mechanical properties were systematically investigated.

[Korean]
The Coercivity Enhancement of (Nd,Dy)-Fe-B Sintered Magnet by Microstructure Control: Jin-Woo Kim, Se-Hoon Kim, Young-Do Kim; J Korean Powder Metall Inst. 2011;18(1):18-23.; DOI: https://doi.org/10.4150/KPMI.2011.18.1.018

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Sintered Nd-Fe-B magnets are widely used in many fields such as motors, generators, actuators, microwaves and so on due to their excellent magnetic properties. Many researchers have shown that the Nd-rich phase was essentially important for high magnet properties. In this study, we focused on controlling of the Nd-rich phase to enhance magnetic properties by the cyclic sintering process. Nd-Fe-B based sintered magnets were prepared by isothermal sintering and cyclic sintering processes. Magnetic properties and microstructure of the magnets were investigated. The coercivity was enhanced from 21.2 kOe to 23.27 kOe after 10 cycles of the sintering. The Nd-rich phase was effectively penetrated into the grain boundary between the Nd_2Fe_14B grains by the cyclic sintering.

Citations

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Effect of cyclic sintering process for NdFeB magnet on microstructure and magnetic properties
Jin Woo Kim, Sun Yong Song, Young Do Kim
Journal of Alloys and Compounds.2012; 540: 141. CrossRef
Transmission electron microscopy studies of sintered Nd-Fe-B magnets prepared by cyclic sintering
Jin Woo Kim, Se Hoon Kim, Sun Yong Song, Young Do Kim
Journal of Applied Physics.2012;[Epub] CrossRef
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

[Korean]
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.

[Korean]
Sintering Behavior and Phase Analysis of (Nd, Dy)-Fe-B Powder: Se-Hoon Kim, Jin-Woo Kim, Young-Do Kim; J Korean Powder Metall Inst. 2010;17(2):154-159.; DOI: https://doi.org/10.4150/KPMI.2010.17.2.154

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In this study, the sintering behavior of (Nd, Dy)-Fe-B powder which fabricated by strip-casting was investigated with various sintering temperatures and holding times. The relative density over 99% could be obtained by both sintering at 1070°C for 1h and sintering at 970°C for 20h. The grain growth was observed in sintered specimen at 1050°C compared to one at 970°C. The isothermal sintering process below 1000°C led to suppress grain growth showing the improved magnetic properties. The phase transformation of Nd-rich was confirmed by X-ray diffraction pattern.

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Crystallographic and Mössbauer studies of sintered Nd-Fe-B magnet
Yong Hui Li, Jung Tae Lim, Chul Sung Kim, Sung Yong An, Kang Ryong Choi, Moonhee Choi
Journal of the Korean Physical Society.2013; 62(11): 1641. CrossRef
Mechanical properties of (Nd,Dy)–Fe–B magnets sintered via cyclic sintering
Jin Woo Kim, Se Hoon Kim, Young Do Kim
Materials Science and Engineering: A.2012; 535: 325. CrossRef
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
High coercive Nd–Fe–B magnets fabricated via two-step sintering
Se Hoon Kim, Jin Woo Kim, Tae Sun Jo, Young Do Kim
Journal of Magnetism and Magnetic Materials.2011; 323(22): 2851. 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

[Korean]
Coercivity Enhancement of Nd₂₃Dy₁₀Fe₆₄TM₂B₁ Sintered Magnet by Convergent Heat Treatment: Hoon-Sup Kim, Se-Hoon Kim, Jin-Woo Kim, Young-Do Kim; J Korean Powder Metall Inst. 2010;17(1):1-6.; DOI: https://doi.org/10.4150/KPMI.2010.17.1.001

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In this study, a convergent heat treatment was performed in certain temperature regions in order to control the microstructures of Nd-rich phases and to reduce thermal stress on grain boundaries which could be caused during expansion and shrinkage of Nd-rich and Nd_2Fe_14B phases. The difference of thermal expansion coefficient between Nd_2Fe_14B and Nd-rich phases is the mechanism for convergent heat treatment. The Nd-rich phases which were located in junctions could penetrate into the grain boundaries between Nd_2Fe_14B phases due to the difference of thermal expansion coefficient. Through the convergent heat treatment, the microcracks that were observed in cyclic heat treatment were not observed and coercivity was increased to 34.05 kOe at 8 cycles.

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Sintering Behavior and Phase Analysis of (Nd, Dy)-Fe-B Powder
Se-Hoon Kim, Jin-Woo Kim, Young-Do Kim
Journal of Korean Powder Metallurgy Institute.2010; 17(2): 154. CrossRef

[Korean]
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.

[Korean]
Effect of Spark Plasma Sintering on the Materials Properties of Water Atomized Al-Zn-Mg Alloy: Sun-Mi Kim, Taek-Soo Kim, Young-Do Kim, Jeong-Gon Kim; J Korean Powder Metall Inst. 2009;16(1):63-67.; DOI: https://doi.org/10.4150/KPMI.2009.16.1.063

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In order to investigate the effect of rapid solidification on the microstructure and the mechanical properties of Al-Zn-Mg system alloys, water atomization was carried out, since the water atomization beared the highest solidification rate among the atomization processes. The as atomized alloy powders consisted of fine grains less than 4 µm in diameter, and the second particles were not detected on XRD. The microstructure as solidified was maintained even after the spark plasma sintering at the heating rate of 50 K/min. On the other hand, lower rate of 20 K/min induced a formation of MgZn_2 particles, resulting in strengthening of the matrix. The density was almost constant at the temperature above 698K. The sintering temperature above 698K had no effect on the strength of the sintered materials.

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Fabrication of Ultra Fine Grained Molybdenum and Mechanical Properties
Se-Hoon Kim, Young-Ik Seo, Dae-Gun Kim, Myung-Jin Suk, Young-Do Kim
Journal of Korean Powder Metallurgy Institute.2010; 17(3): 235. CrossRef

[Korean]
The Formation of Hybridized Porous Structure of Al Alloy by Alkali Surface Modification: Young-Ik Seo, Young-Moon Kim, Young-Jung Lee, Dae-Gun Kim, Kyu-Hwan Lee, Young-Do Kim; J Korean Powder Metall Inst. 2009;16(1):22-27.; DOI: https://doi.org/10.4150/KPMI.2009.16.1.022

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To improve the filtration efficiency of porous materials used in filters, an extensive specific surface area is required to serve as a site for adsorption of impurities. In this paper, a method for creating a hybridized porous alloy using a powder metallurgical technique to build macropores in an Al-4 wt.% Cu alloy and subsequent surface modification for a microporous surface with a considerably increased specific surface area is suggested. The macropore structure was controlled by granulation, compacting pressure, and sintering; the micropore structure was obtained by a surface modification using a dilute NaOH solution. The specific surface area of surface-modified specimen increased about 10 times compare to as-sintered specimen that comprised of the macropore structure. Also, the surface-modified specimens showed a remarkable increase in micropores larger than 10 nm. Such a hybridized porous structure has potential for application in water and air purification filters, as well as membrane pre-treatment and catalysis.

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Development of Vacuum Thin-Film-Forming Mold using Porous Aluminum
Hyung-Sun Kang, Sunghyun Lee
Journal of the Korean Society of Manufacturing Technology Engineers.2020; 29(6): 435. CrossRef
Phosphorus removal from wastewater by ionic exchange using a surface-modified Al alloy filter
Young Ik Seo, Ki Ho Hong, Se Hoon Kim, Duk Chang, Kyu Hwan Lee, Young Do Kim
Journal of Industrial and Engineering Chemistry.2013; 19(3): 744. CrossRef

[Korean]
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.

Citations

Citations to this article as recorded by

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

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