Journal of Powder Materials

In-Shup Ahn

7 Articles

Synthesis of Cathode Material-Nickel Sulfides by Mechanical Alloying for Sodium Batteries: Xiaojing Liu, Hyo-Jun Ahn, In-Shup Ahn; J Korean Powder Metall Inst. 2012;19(3):182-188.; DOI: https://doi.org/10.4150/KPMI.2012.19.3.182

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Abstract PDF: In this study, fine cathode materials Ni_3S_2 and NiS_2 were synthesized using the simple, convenient process of mechanical alloying (MA). In order to improve the cell properties, wet milling processes were conducted using low-energy ball milling to decrease the mean particle size of both materials. The cells of Na/Ni_3S_2 and Na/NiS_2 show a high initial discharge capacity of 425 mAh/g and 577 mAh/g respectively using wet milled powder particles, which is much larger than commercial ones, providing some potential as new cathode materials for rechargeable sodium-ion batteries.

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.

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.

Synthesis of Titanium Carbide Nano Particles by the Mechano Chemical Process: In-Shup Ahn, Dong-Kyu Park, Yong-Hee Lee; J Korean Powder Metall Inst. 2009;16(1):43-49.; DOI: https://doi.org/10.4150/KPMI.2009.16.1.043

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Titanium carbides are widely used for cutting tools and grinding wheels, because of their superior physical properties such as high melting temperature, high hardness, high wear resistance, good thermal conductivity and excellent thermal shock resistance. The common synthesizing method for the titanium carbide powders is carbo-thermal reduction from the mixtures of titanium oxide(TiO_2) and carbon black. The purpose of the present research is to fabricate nano TiC powders using titanium salt and titanium hydride by the mechanochemical process(MCP). The initial elements used in this experiment are liquid TiCl_4(99.9%), TiH_2(99.9%) and active carbon(<32µm, 99.9%). Mg powders were added to the TiCl_4 solution in order to induce the reaction with Cl-. The weight ratios of the carbon and Mg powders were theoretically calculated. The TiC and MgCl_2 powders were milled in the planetary milling jar for 10 hours. The 40 nm TiC powders were fabricated by wet milling for 4 hours from the TiCl_4+C+Mg solution, and 300 nm TiC particles were obtained by using titanium hydride.

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Quantitative Study on the Refinement Behaviors of TiC Powders Produced by Mechanical Milling Under Different Impact Energy
Sung-Mo Hong, Eun-Kwang Park, Kyeong-Yeol Kim, Jin-Ju Park, Min-Ku Lee, Chang-Kyu Rhee, Jin-Kyu Lee, Young-Soon Kwon
Journal of Korean Powder Metallurgy Institute.2012; 19(1): 32. CrossRef

The Phase Analysis of MgB₂ Fabricated by Spark Plasma Sintering after Ball Milling: Deuk-Kyun Kang, Sung-Hyun Choi, In-Shup Ahn; J Korean Powder Metall Inst. 2008;15(5):371-377.; DOI: https://doi.org/10.4150/KPMI.2008.15.5.371

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Abstract PDF: This paper deals with the phase analysis of MgB_2 bulk using spark plasma sintering process after ball milling. Mg and amorphous B powders were used as raw materials, and milled by planetary-mill for 9 hours at argon atmosphere. In order to confirm formation of MgB_2 phase, DTA and XRD were used. The milled powders were fabricated to MgB_2 bulk at the various temperatures by Spark Plasma Sintering. The fabricated MgB_2 bulk was evaluated with XRD, EDS, FE-SEM and PPMS. In the DTA result, reaction on formation of MgB_2 phase started at 340°C. This means that ball milling process improves reactivity on formation of MgB_2 phase. The MgB_2 MgO and FeB phases were characterized from XRD result. MgO and FeB were undesirable phases which affect formation of MgB_2 phase, and it's distribution could be confirmed from EDS mapping result. Spark Plasma Sintered sample for 5 min at 700°C was relatively densified and it's density and transition temperature showing super conducting property were 1.87;g/cm3 and 21K.

The Densification Properties of Distaloy AE-TiC Cermet by Spark Plasma Sintering: Ho-Jung Cho, In-Shup Ahn, Young-Hee Lee, Dong-Kyu Park; J Korean Powder Metall Inst. 2007;14(4):230-237.; DOI: https://doi.org/10.4150/KPMI.2007.14.4.230

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Abstract PDF: The fabrication of Fe alloy-40 wt.%TiC composite materials using spark plasma sintering process after ball-milling was studied. Raw powders to fabricate Fe alloy-TiC composite were Fe alloy, TiH_2 and activated carbon. Fe alloy powder was Distaloy AE (4%Ni-1%Cu-0.5%Mo-0.01%C-bal.%Fe) made by Hoeganes company with better toughness and lower melting point. These powders were ball-milled in horizontal attrition ball mill at a ball-to-powder weight ratio of 30 : 1. After that, these mixture powders were sintered by using spark plasma sintering apparatus for 5 min at 1200-1275°C in vacuum atmosphere under 10-3 torr. DistaloyAE-40 wt.%TiC composite was directly synthesized by dehydrogenation and carburization reaction during sintering process. The phase transformation of as-milled powders and sintered materials was confirmed using X-ray diffraction (XRD) and transmission electron microscope (TEM). The density and harness materials was measured in order to confirm the densification behavior. In case of DistaloyAE-40 wt.%TiC composite retained for 5 min at 1275°C, it has the relative density of about 96% through the influence of rapid densification and fine TiC particle reinforced Fe-based composites materials.

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