Journal of Powder Materials

Kwon-Koo Cho

7 Articles

A Study on the Sintering Behavior of T42 High Speed Steel by Powder Injection Molding (PIM) Process: Dong-Wook Park, Hye-Seong Kim, Young-Sam Kwon, Kwon-Koo Cho, Su-Gun Lim, In-Shup Ahn; J Korean Powder Metall Inst. 2012;19(2):117-121.; DOI: https://doi.org/10.4150/KPMI.2012.19.2.117

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Tool steels serve a large range of applications including hot and cold workings of metals and injection mouldings of plastics or light alloys. The high speed steels (HSS) are specifically used as cutting tools and wear parts because it has high strength, wear resistance and hardness along with appreciable toughness and fatigue resistance. From the view of HSS microstructure, it can be described as metallic matrix composites formed by a ferrous with a dispersion of hard and wear resistant carbides. The experimental specimens were manufactured using the PIM with T42 powders (50~80 vol.%) and polymer (20~50 vol.%). The green parts were debinded in n-hexane solution at 60°C for 8 hours and thermal debinded at an N_2-H_2 mixed gas atmosphere for 8 hours. Specimens were sintered in high vacuum (10-5 Torr) and various temperatures.

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Effects Of Process Parameters On Cu Powder Synthesis Yield And Particle Size In A Wet-Chemical Process
Y.M. Shin, J.-H. Lee
Archives of Metallurgy and Materials.2015; 60(2): 1247. CrossRef

The Characteristic Changes of Sintered WC-10Co Fabricated by PIM Method with Different Carbon Content: Sang-Dae Kang, Dong-Wook Park, Young-Sam Kwon, Kwon-Koo Cho, In-Shup Ahn; J Korean Powder Metall Inst. 2011;18(3):262-268.; DOI: https://doi.org/10.4150/KPMI.2011.18.3.262

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Abstract PDF: In order to investigate the microstructure and mechanical properties of WC-10 wt% Co insert tool alloy fabricated by PIM (Powder Injection Molding) process, the feedstock of WC-10 wt% and wax used as a kind of binder were mixed together by two blade mixer. After injection molding, the debinding process was carried out by two-steps. First, solvent extraction, in which the binder was eliminated by putting the specimen into normal hexane for 24 hrs at 60°C, and subsequently thermal debinding which was conducted at 260°C and 480°C for 6 hrs in the mixed gas of H_2/N_2, respectively. Meantime, in order to compensate the decarburization due to hydrogen, 1.2~1.8% of carbon was added to ensure the integrity of the phase. Finally, the specimens were sintered in vacuum under different temperatures, and the relative density of 99.8% and hardness of 2100 Hv can be achieved when sintered at 1380°C, even the TRS is lower than the conventional sintering process.

Fabrication and Growth of Ni Nanowires by using Anodic Aluminum Oxide(AAO) Template via Electrochemical Deposition: Seong-Ju Sim, Kwon-Koo Cho, Yoo-Young Kim; J Korean Powder Metall Inst. 2011;18(1):49-55.; DOI: https://doi.org/10.4150/KPMI.2011.18.1.049

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Ni nanowires were fabricated using anodic aluminum oxide (AAO) membrane as a template by electrochemical deposition. The nanowires were formed within the walls of AAO template with 200 nm in pore diameter. After researching proper voltage and temperature for electrochemical deposition, the length of Ni nanowires was controlled by deposition time and the supply of electrolyte. The morphology and microstructure of Ni nanowires were investigated by field emission scanning electron microscope (FE-SE), X-ray diffraction (XRD) and transmission electron microscope (TEM).

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Electrocrystallization of Metals in Channels of Porous Films of Anodic Aluminum Oxide: The Real Template Structure and the Quantitative Model of Electrodeposition
A. A. Noyan, I. V. Kolesnik, A. P. Leont’ev, K. S. Napol’skii
Russian Journal of Electrochemistry.2023; 59(7): 489. CrossRef
Electrocrystallization of Metals in Channels of Porous Films of Anodic Aluminum Oxide: The Real Template Structure and the Quantitative Model of Electrodeposition
A. A. Noyan, I. V. Kolesnik, A. P. Leont’ev, K. S. Napol’skii
Электрохимия.2023; 59(7): 378. CrossRef
Synthesis and Characterization of Nickel Nanowires by an Anodic Aluminum Oxide Template-Based Electrodeposition
Hyo-Ryoung Lim, Yong-Ho Choa, Young-In Lee
Journal of Korean Powder Metallurgy Institute.2015; 22(3): 216. CrossRef
Synthesis and Characterization of Cu Nanowires Using Anodic Alumina Template Based Electrochemical Deposition Method
Young-In Lee, Yong-Ho Choa
Journal of Korean Powder Metallurgy Institute.2012; 19(5): 367. CrossRef

Fabrication and Growth Behavior of TiO₂ Nanotube Arrays by Anodic Oxidation Method: Seon-Min Kim, Ki-Won Kim, Kwang-Sun Ryu, Yoo-Young Kim, Kwon-Koo Cho; J Korean Powder Metall Inst. 2011;18(1):56-63.; DOI: https://doi.org/10.4150/KPMI.2011.18.1.056

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Abstract PDF: Recently, TiO_2 nanotubes have considerably researched because of their novel application about photocatalysis, dye-sensitized solar cells (DSSCs), lithium ion battery, etc. In this work, self-standing TiO_2 nanotube arrays were fabricated by anodic oxidation method using pure Ti foil as a working electrode in ethylene glycole with 0.3M NH_4F + 2%H_2O. Growth behavior of TiO_2 nanotube arrays was compared according to temperature, voltage and time. The morphology, structure and crystalline of anodized TiO_2 nanotube arrays were observed by FE-SEM (field emission scanning electron microscope) and XRD (X-ray diffraction).

The Microstructural Properties Change Owing to the Sintering Condition of T42 High Speed Steel Produced by Powder Injection Molding Process: Kyoung-Rok Do, Sung-Hyun Choi, Young-Sam Kwon, Kwon-Koo Cho, In-Shup Ahn; J Korean Powder Metall Inst. 2010;17(4):312-318.; DOI: https://doi.org/10.4150/KPMI.2010.17.4.312

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Abstract PDF: High speed steels (HSS) were used as cutting tools and wear parts, because of high strength, wear resistance, and hardness together with an appreciable toughness and fatigue resistance. Conventional manufacturing process for production of components with HSS was used by casting. The powder metallurgy techniques were currently developed due to second phase segregation of conventional process. The powder injection molding method (PIM) was received attention owing to shape without additional processes. The experimental specimens were manufactured with T42 HSS powders (59 vol%) and polymer (41 vol%). The metal powders were prealloyed water-atomised T42 HSS. The green parts were solvent debinded in normal n-Hexane at 60°C for 24 hours and thermal debinded at N_2-H_2 mixed gas atmosphere for 14 hours. Specimens were sintered in N_2, H_2 gas atmosphere and vacuum condition between 1200 and 1320°C. In result, polymer degradation temperatures about optimum conditions were found at 250°C and 480°C. After sintering at N_2 gas atmosphere, maximum hardness of 310Hv was observed at 1280°C. Fine and well dispersed carbide were observed at this condition. But relative density was under 90%. When sintering at H_2 gas atmosphere, relative density was observed to 94.5% at 1200°C. However, the low hardness was obtained due to decarbonization by hydrogen. In case of sintering at the vacuum of 10-5 torr at temperature of 1240°C, full density and 550Hv hardness were obtained without precipitation of MC and M_6C in grain boundary.

Fabrication of Iron-Molybdenum Alloyed Nanoparticle and Nanowire using Chemical Vapor Condensation(CVC): Jong-Keun Ha, Kwon-Koo Cho, Ki-Won Kim, Kwang-Sun Ryu; J Korean Powder Metall Inst. 2010;17(3):223-229.; DOI: https://doi.org/10.4150/KPMI.2010.17.3.223

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Abstract PDF: Iron(Fe)-Molybdenum(Mo) alloyed nanoparticles and nanowires were produced by the chemical vapor condensation(CVC) process using the pyrolysis of iron pentacarbonyl(Fe(CO)_5) and Molybdenum hexacarbonyl(Mo(CO)_6). The influence of CVC parameter on the formation of nanoparticle, nanowire and size control was studied. The size of Fe-Mo alloyed nanoparticles can be controlled by quantity of gas flow. Also, Fe-Mo alloyed nanowires were produced by control of the work chamber pressure. Moreover, we investigated close correlation of size and morphology of Fe-Mo nanoparticles and nanowires with atomic quantity of inflow precursor into the electric furnace as the quantitative analysis. Obtained nanoparticles and nanowires were investigated by field emission scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction.

Fabrication of TiO₂ Nanotube Arrays by Anodic Oxidation Method and its Photoelectrochemical Properties: Seon-Min Kim, Kwon-Koo Cho, Yeong-Jin Choe, Ki-Won Kim, Kwang-Sun Ryu; J Korean Powder Metall Inst. 2010;17(3):216-222.; DOI: https://doi.org/10.4150/KPMI.2010.17.3.216

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Self-standing TiO_2 nanotube arrays were fabricated by potentiostatic anodic oxidation method using pure Ti foil as a working electrode and ethylene glycol solution as electrolytes with small addition of NH_4F and H_2O. The influences of anodization temperature and time on the morphology and formation of TiO_2 nanotube arrays were investigated. The fabricated TiO_2 nanotube arrays were applied as a photoelectrode to dye-sensitized solar cells. Regardless of anodizing temperature and time, the average diameter and wall thickness of TiO_2 nanotube show a similar value, whereas the thickness show a different trend with reaction temperature. The thickness of TiO_2 nanotube arrays anodized at 20°C and 30°C was time-dependent, but on the other hand its at 10°C are independent of anodization time. The conversion efficiency is low, which is due to a morphology breaking of the TiO_2 nanotube arrays in manufacturing process of photoelectrode.

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The growth and morphology of copper phthalocyanine on TiO2 nanotube arrays
Sung Ha Ju, Sanghyun Han, Jeong Soo Kim
Journal of Industrial and Engineering Chemistry.2013; 19(1): 272. CrossRef
Characteristics of Porous Titanium Fabricated by Space-holder Method using NaCl
Byoung-Hwi Son, Jae-Geun Hong, Yong-Taek Hyun, Seung-Eon Kim, Seok-Choun Bae
Journal of Korean Powder Metallurgy Institute.2011; 18(6): 488. CrossRef
Investigation About Surface Microstructure of Aluminum with Change of Voltage, a Period of Treatment and Density of Electrolyte in Micro-Arc Oxidation Treatment
In-Chul Yeo, In-Cheol Kang
Journal of Korean Powder Metallurgy Institute.2011; 18(6): 575. CrossRef

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