Journal of Powder Materials

Synthesis and Characterization of CuInS₂ Semiconductor Nanoparticles and Evolution of Optical Properties via Surface Modification: Hee-Seung Yang, Yoo-Jin Kim; J Korean Powder Metall Inst. 2012;19(3):177-181.; DOI: https://doi.org/10.4150/KPMI.2012.19.3.177

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Copper composite materials have attracted wide attention for energy applications. Especially CuInS_2 has a desirable direct band gap of 1.5 eV, which is well matched with the solar spectrum. CuInS_2 nanoparticles could make it possible to develop color-tunable CuInS_2 nanoparticle emitter in the near-infrared region (NIR) for energy application and bio imaging sensors. In this paper, CuInS_2 nanoparticles were successfully synthesized by thermo-decomposition methods. Surface modification of CuInS_2 nanoparticles were carried out with various semiconductor materials (CdS, ZnS) for enhanced optical properties. Surface modification and silica coating of hydrophobic nanoparticles could be dispersed in polar solvent for potential applications. Their optical properties were characterized by UV-vis spectroscopy and photoluminescence spectroscopy (PL). The structures of silica coated CuInS_2 were observed by transmission electron microscopy (TEM).

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Surface Treatment Method for Long-term Stability of CdSe/ZnS Quantum Dots
Hyun-Su Park, Da-Woon Jeong, Bum-Sung Kim, So-Yeong Joo, Chan-Gi Lee, Woo-Byoung Kim
Journal of Korean Powder Metallurgy Institute.2017; 24(1): 1. CrossRef
Effect of Carboxylic Acid on Optical Properties of CuInS2/ZnS Semiconductor Nanocrystals
Si-Hyun Ahn, Gyu-Che Choi, Yeun-Kyung Beak, Young-Kuk Kim, Yang-Do Kim
Journal of Korean Powder Metallurgy Institute.2012; 19(5): 362. CrossRef

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.

Mechanical Properties of Surface Densified PM Gears: Ki-Jung Kim, Ki-Bum Kim, Doo-Hwan Lee, Jong-Kwan Park, Dong-Guk Jeong; J Korean Powder Metall Inst. 2012;19(3):189-195.; DOI: https://doi.org/10.4150/KPMI.2012.19.3.189

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A novel PM (powder metallurgy) steel for automotive power-train gear components was developed to reduce manufacturing cost, while meeting application requirements. The high-density PM steel was manufactured by mixing using special Cr-Mo atomized iron powders, high-pressure compaction, and sintering. Tensile strength, charpy impact, bending fatigue, and contact fatigue tests for the PM steel were carried out and compared to conventional forged steel. Pinion gears for auto-transmission were also manufactured by helical pressing, sintering, and surface densification process. In order to evaluate the durability of the PM parts, auto-transmission durability tests were performed using dynamometer tests. Results showed that the PM steel fulfilled the requirements for pinion gears indicating suitable tensile, bending fatigue, contact fatigue strengths and improved gear tooth profile. The PM gears also showed good performance during the transmission durability tests. As a result, the PM gears showed significant potential to replace the conventional forged steel gears manufactured by tooth machining (hobbing, shaving, and grinding) processes.

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Thermal Properties and Microstructural Changes of Fe-Co System Valve Seat Alloy by High Densification Process
In-Shup Ahn, Dong-Kyu Park, Kwang-Bok Ahn, Seoung-Mok Shin
Journal of Korean Powder Metallurgy Institute.2019; 26(2): 112. CrossRef

Influence of MAO Conditions on TiO₂ Microstructure and Its Photocatalytic Activity: Jeong-Gon Kim, In-Cheol Kang; J Korean Powder Metall Inst. 2012;19(3):196-203.; DOI: https://doi.org/10.4150/KPMI.2012.19.3.196

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TiO_2 was successfully formed on a Ti specimen by MAO (Micro-Arc-Oxidation) method treated in Na_3PO_4 electrolyte. This study deals with the influence of voltage and working time on the change of surface microstructure and phase composition. Voltage affected the forming rate of the oxidized layer and surface microstructure where, a low voltage led to a high surface roughness, more holes and a thin oxidized layer. On the other hand, a high voltage led to more dense surface structure, wider surface holes, a thick layer and fewer holes. Higher voltage increases photocatalytic activity because of better crystallization of the oxidized layer and good phase composition with anatase and rutile TiO_2, which is able to effectively separate excited electrons and holes at the surface.

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Study on thermal behavior of Ammonium Hexafluofide Titanate for Synthesis of TiO2 Powders
Duk-Hee Lee, Jae-Ryang Park, Chan-Gi Lee, Kyung-Soo Park, Hyeon-Mo Kim
Journal of Korean Powder Metallurgy Institute.2016; 23(5): 353. CrossRef
Control of Nano-Scaled Surface Microstructure of Al Sample for Improving Heat Release Ability
In-Chul Yeo, In-Cheol Kang
Journal of Korean Powder Metallurgy Institute.2015; 22(1): 21. CrossRef

Ultrafine Grained Cu-diamond Composites using High Pressure Torsion: Eun-Yoo Yoon, Dong-Jun Lee, Taek-Soo Kim, Hyoung-Seop Kim; J Korean Powder Metall Inst. 2012;19(3):204-209.; DOI: https://doi.org/10.4150/KPMI.2012.19.3.204

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In this work, powder metallurgy and severe plastic deformation by high-pressure torsion (HPT) approaches were combined to achieve both full density and grain refinement at the same time. Pure Cu powders were mixed with 5 and 10 vol% diamonds and consolidated into disc-shaped samples at room temperature by HPT at 1.25 GPa and 1 turn, resulting in ultrafine grained metallic matrices embedded with diamonds. Neither heating nor additional sintering was required with the HPT process so that in situ consolidation was successfully achieved at ambient temperature. Significantly refined grain structures of Cu metallic matrices with increasing diamond volume fractions were observed by electron backscatter diffraction (EBSD), which enhanced the microhardness of the Cu-diamond composites.

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Effect of a nano-sized TiC particle addition on the flow-assisted corrosion resistance of SA 106B carbon steel
Jin-Ju Park, Eun-Kwang Park, Gyoung-Ja Lee, Chang-Kyu Rhee, Min-Ku Lee
Applied Surface Science.2017; 415: 143. CrossRef
Analyses of Densification and Consolidation of Copper Powders during High-Pressure Torsion Process Using Finite Element Method
Dong Jun Lee, Eun Yoo Yoon
Journal of Korean Powder Metallurgy Institute.2015; 22(1): 6. CrossRef
Trend in Research of Powder Consolidation Using Severe Plastic Deformation
Eun Yoo Yoon, Dong Jun Lee, Dong-Hyun Ahn, Hyuk Jae Jeong, Hyoung Seop Kim
Journal of Korean Powder Metallurgy Institute.2013; 20(2): 148. CrossRef
Microstructure Evolution and Mechanical Properties of Al-1080 Processed by a Combination of Equal Channel Angular Pressing and High Pressure Torsion
Mohamed Ibrahim Abd El Aal, Eun Yoo Yoon, Hyoung Seop Kim
Metallurgical and Materials Transactions A.2013; 44(6): 2581. CrossRef
Grinding Behaviour of Aluminum Powder for Al/CNTs Nano Composites Fabrication by Dry Grinding Process Using a High Speed Planetary Ball Mill
Heekyu Choi, Jehyun Lee, Seongsoo Kim, Gyungpil Choi, Daehyung Bae, Sungbak Lee, Woong Lee
Korean Journal of Materials Research.2013; 23(2): 89. CrossRef
Densification of Copper Powders using High-pressure Torsion Process
Dong-Jun Lee, Eun-Yoo Yoon, Soo-Young Kang, Jung-Hwan Lee, Hyoung-Seop Kim
Journal of Korean Powder Metallurgy Institute.2012; 19(5): 333. CrossRef

Synthesis and Electrochemical Performance of Li₂MnSiO₄ for Lithium Ion Battery Prepared by Amorphous Silica Precusor: Yun-Ho Jin, Kun-Jae Lee, Lee-Seung Kang, Hang-Chul Jung, Hyun-Seon Hong; J Korean Powder Metall Inst. 2012;19(3):210-214.; DOI: https://doi.org/10.4150/KPMI.2012.19.3.210

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Abstract PDF: Mass production-capable Li_2MnSiO_4 powder was synthesized for use as cathode material in state-of-the-art lithium-ion batteries. These batteries are main powder sources for high tech-end digital electronic equipments and electric vehicles in the near future and they must possess high specific capacity and durable charge-discharge characteristics. Amorphous silicone was quite superior to crystalline one as starting material to fabricate silicone oxide with high reactivity between precursors of sol-gel type reaction intermediates. The amorphous silicone starting material also has beneficial effect of efficiently controlling secondary phases, most notably Li_xSiO_x. Lastly, carbon was coated on Li_2MnSiO_4 powders by using sucrose to afford some improved electrical conductivity. The carbon-coated Li_2MnSiO_4 cathode material was further characterized using SEM, XRD, and galvanostatic charge/discharge test method for morphological and electrochemical examinations. Coin cell was subject to 1.5-4.8 V at C/20, where 74 mAh/g was observed during primary discharge cycle.

Evaluation of Creep Reliability of Powder Metallurgy and Cast-type Ni-based Superalloy by Using Ultrasonic Wave: Chan-Yang Choi, Jin-Hun Song, Se-Ung Oh, Chung-Seok Kim, Sook-In Kwun, Sung-Tag Oh, Chang-Yong Hyun, Jai-Won Byeon; J Korean Powder Metall Inst. 2012;19(3):215-219.; DOI: https://doi.org/10.4150/KPMI.2012.19.3.215

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Abstract PDF: An attempt was made to evaluate creep reliability of two commercial Ni-based superalloys by using ultrasonic wave. The materials include fine-grained PM alloy fabricated by mechanical alloying and subsequent hot isostatic pressing, and IN738LC cast alloy with a grain size of a few cm. Microstructural parameters (fraction of creep cavity and size of gammaprime precipitates) and ultrasonic parameters (velocity, attenuation) were measured to try to find relationships between them. Ultrasonic velocity decreased with creep cavity formation in PM alloy. On the other hand, no distinct changing trend of ultrasonic velocity was observed for IN738LC alloy. Ultrasonic attenuation was found to have a linear correlation with the size of gammaprime precipitates and was suggested as a potential parameter for monitoring creep reliability of IN738LC alloy.

Effect of Solution Properties on Luminance Characteristics of YAG:Ce Phosphors Prepared by Spray Pyrolysis: You-Mi Lee, Tae-Won Kang, Kyeong-Youl Jung; J Korean Powder Metall Inst. 2012;19(3):220-225.; DOI: https://doi.org/10.4150/KPMI.2012.19.3.220

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Abstract PDF: YAG:Ce yellow phosphor particles were synthesized by spray pyrolysis with changing the solution properties and their luminous properties, crystal structure, and morphological changes were studied by using PL measurement, XRD, and SEM analysis. It was clear that the solution properties significantly affected the crystal phase, crystallite size, the PL intensity, and the morphology of YAG:Ce particles. At low calcination temperature, the addition of urea only to the spray solution was helpful to form a pure YAG phase without any impurity phases, as the result, the highest luminescence intensity was achieved at the calcination temperature of 900°C. When the calcination temperatures were larger than 1300°C, however, the YAG particles prepared without any additive showed the highest luminescent intensity. Regardless of the solution conditions, the emission intensity of YAG:Ce particles prepared by spray pyrolysis showed a linear relation with the crystallite size. In terms of the morphology of YAG:Ce particles, the addition of both DCCA and NH_4OH to the spray solution was effective to prepare a spherical and dense structured YAG particles.

Fabrication of Fe coated Mg Based Desulfurization Powder by Mechanical Alloying Process: Joon-Woo Song, Otaduy Guillermo, Byong-Sun Chun, Soon-Jik Hong; J Korean Powder Metall Inst. 2012;19(3):226-231.; DOI: https://doi.org/10.4150/KPMI.2012.19.3.226

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Abstract PDF: In this research, the coating behavior of Mg and Fe desulfurization powder fabricated by low energy and conventional planetary mill equipment was investigated as a function of milling time, which produces uniform Fe coated powders due to milling energy. Since high energy ball milling results in breaking the Fe coated Mg powders into coarse particles, low energy ball milling was considered appropriate for this study, and can be implemented in desulfurization industry widely. XRD and FE-SEM analyses were carried out to investigate the microstructure and distribution of the coating material. The thickness of the Fe coating layer reaches a maximum of 14 µm at 20 milling hours. The BCC structures of Fe particles are deformed due to the slip system of Fe coated Mg particles.

Recycling Technology and Status of Tellurium Materials: Hyo-Seob Kim, Soon-Jik Hong; J Korean Powder Metall Inst. 2012;19(3):232-238.; DOI: https://doi.org/10.4150/KPMI.2012.19.3.232

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