Journal of Powder Materials

Principle and Applications of EELS Spectroscopy in Material Characterizations: Sang-Won Yoon, Kyou-Hyun Kim, Jae-Pyoung Ahn, Jong-Ku Park; J Korean Powder Metall Inst. 2007;14(3):157-164.; DOI: https://doi.org/10.4150/KPMI.2007.14.3.157

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Abstract PDF: An electron energy loss spectroscopy (EELS) instrument attached on transmission electron microscopy (TEM) becomes a powerful and analytical tool for extracting the noble information of materials using the enhancement of TEM images, elemental analysis, elemental or chemical mapping images, electron energy loss near edge structure (ELNES), and extended energy-loss fine structure (EXELFS). In this review, the principle and applications of EELS which is widely used in material, life, and electronic sciences were introduced.

Sintering Characteristics of Au and Ag Nanoparticles Prepared by Inert Gas Condensation: Seung-Hyun Lee, Dong-Ryoul Min, Kwang-Min Lee; J Korean Powder Metall Inst. 2007;14(3):165-172.; DOI: https://doi.org/10.4150/KPMI.2007.14.3.165

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Abstract PDF: The purpose of this study was to analyze the sintering characteristics of gold and silver nanoparticles. In this study, gold and silver nanoparticles were prepared by using Inert Gas Cndensation (IGC). The sintering temperatures for gold and silver nanoparticles were 100sim1000°C;and'100sim500°C, respectively. The sintering characteristics of gold and silver nanoparticles prepared by IGC were evaluated by X-ray diffraction(XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Gold and silver nanoparticles with the size of 1sim100;nm;and;10sim100;nm, respectively, were obtained. The size of sintered gold and silver nanoparticles increased with an increase in the sintering temperature. XRD data showed that silver nanoparticles were similar with polycrystal single-phase.

Characteristics of Tantalum Powder Manufactured by the MR and EMR Process: Hyeoung-Ho Park, Jae-Sik Yoon, In-Sung Bae, Yang-Soo Kim, Dong-Ju Yoon, Dae-Hee Won, Byung-Il Kim; J Korean Powder Metall Inst. 2007;14(3):173-179.; DOI: https://doi.org/10.4150/KPMI.2007.14.3.173

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Abstract PDF: In the metallothermic reduction (MR) process used to obtain tantalum powder in one batch, it is difficult to control the morphology and location of the tantalum deposits. On the other hand, an electronically mediated reaction (EMR) process is capable of overcoming this difficulty. The effect of using K_2TaF_7 as the raw material and sodium as the reducting agent on the characteristics of tantalum powder are investigated. As the temperature of the reduction varied from 1023K to 1223K, the powder particles obtained with MR were relatively large (sim34µm), while those prepared via EMR were of uniform (13µm). In the MR process, the Ta powder recovery rate increased from 37% to 83% at 1123K in constrat with EMR process.

Synthesis of Multiferroic Nanocomposites by a Polyol Method: In-Bo Shim, Jeffrey Pyun, Yong-Wook Park, Young-Rang Uhm, Chul-Sung Kim; J Korean Powder Metall Inst. 2007;14(3):180-184.; DOI: https://doi.org/10.4150/KPMI.2007.14.3.180

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The material design and synthesis are of important to modem science and technology. Here, we report the synthesis of multifunctional nanomaterials with different properties: feroelecties YMnO_3 and multiferroic materials such as CoFe_2O_4-YMnO_3,;Fe_3O_4-YMnO_3,;CoFe_2O_4-Cd_0.85Zn_0.15S,;and;Fe_3O_4-Cd_0.85Zn_0.15S nano-composites by using a chemical synthesis process. These results provide a simple and convenient synthesis process to produce multifunctional nanocomposites.

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Structure, morphology, infra-red and dielectric investigations in Er+3doped nano phased lithium-barium-strontium-sodium niobates
S Bheemeswara Rao, P Viswarupachary, D M Potukuchi
Materials Research Express.2019; 6(6): 066562. CrossRef

Compaction Properties of Fe Powder Fabricated by Warm Compaction: Se-Hoon Kim, Young-Jung Lee, Jea-Sung Lee, Young-Do Kim; J Korean Powder Metall Inst. 2007;14(3):185-189.; DOI: https://doi.org/10.4150/KPMI.2007.14.3.185

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Abstract PDF: Various approaches have been proposed to increase the green density. Warm compaction method has been used for the reduction of residual stress, the improvement of magnetic properties and the higher densities. In this work, the effect of warm compaction on green density of Fe powder was investigated. After ball-milling of Fe oxide powder for 30 hours, Fe oxide powder was reduced through the hydrogen reduction process. The pure Fe powder and polymer binder were mixed by 3-D tubular mixer. And then the mixed powder was warm-compacted with various compaction pressure and binder contents. The green density of specimen was added polyvinyl binder was higher than any other specimens.

Characteristics of Tantalum Powder on the Location of Reductant by MR and EMR Combination Process: Hyeoung-Ho Park, Jae-Sik Yoon, In-Sung Bae, Yang-Soo Kim, Dong-Ju Yoon, Dae-Hee Won, Byung-Il Kim; J Korean Powder Metall Inst. 2007;14(3):190-196.; DOI: https://doi.org/10.4150/KPMI.2007.14.3.190

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Abstract PDF: A process known as the MR and EMR combination process is able to overcome the shortcomings of the MR (metallothermic reduction) and EMR (electronically mediated reaction) process. The effects of K_2TaF_7 as the raw material, sodium as the reducing agent and KCl/KF as the diluent on the characteristics of tantalum powder are investigated. In this study, a MR-EMR combination process has been employed to tantalum powder on the location of reductant. The excess of reductant were varied from 25, 50 to 75 wt%. The total charge and external circuit decreases as the amount of reductant increases. The average particle size increases with increasing the amount of reductant.

Fabrication of Bulk Metallic Glass Composites by Mechanical Milling with Subsequent Spark Plasma Sintering Process: Jin-Kyu Lee, Taek-Soo Kim, Jeong-Gon Kim; J Korean Powder Metall Inst. 2007;14(3):197-201.; DOI: https://doi.org/10.4150/KPMI.2007.14.3.197

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Bulk metallic glass (BMG) composite was fabricated by consolidation of milled metallic glass composite powders. The metallic glass composite powder was synthesized by a controlled milling process using the Cu-based metallic glass powder blended with 30 vol% Zr-based metallic glass powders. The milled composite powders showed a layered structure with three metallic phases, which is formed as a result of mechanical milling. By spark plasma sintering of milled metallic glass powders in the supercooled liquid region, a fully dense BMG composite was successfully synthesized.

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Powder Sintering Characteristics of Carbon Nanotubes Reinforced SKD11 Tool Steel Sintered by Spark Plasma Sintering
Je-Se Moon, Sung-Sil Jung, Dae-Yeol Lee, Young-Keun Jeong, Myung Chang Kang, Chun-Dal Park, Kook-Tae Youn
Journal of Korean Powder Metallurgy Institute.2015; 22(3): 157. CrossRef

Fabrication of Micro Component of Metallic Nano Powder Using Polymer Mold: Woo-Seok Lee, Sang-Phil Kim, Hye-Moon Lee, Dong-Sik Bae, Chul-Jin Choi; J Korean Powder Metall Inst. 2007;14(3):202-207.; DOI: https://doi.org/10.4150/KPMI.2007.14.3.202

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Abstract PDF: Novel polymer mold process for fabrication of microcomponents using metal nanopowders was developed and experimentally optimized. Polymer mold for forming green components was produced by using a hard master mold and polydimethylsiloxane (PDMS). In the preparation of metallic powder premix for the green components without any defect, 90 wt.% 17-4PH statinless steel nanopowders and 10 wt.% organic binder were mixed by a ball milling process. The green components with very clear gear shape were formed by filling the powder premix into the PDMS soft mold in surrounding at about 100°C. Cold isostatic pressing (CIP) was very potent process to decrease a porosity in the sintered microcomponent. The microgear fabricated by the improved process showed a good dimension tolerance of about 1.2%.

Effect of Metallic Binder Composition on Microstructure and Hardness of (W,Ti)C Cemented Carbides: Walid M. Daoush, Kyong-H. Lee, Hee-S. Park, Jong-J. Jang, Soon-H. Hong; J Korean Powder Metall Inst. 2007;14(3):208-214.; DOI: https://doi.org/10.4150/KPMI.2007.14.3.208

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The microstructure and hardness of (W,Ti)C cemented carbides with a different metallic binder composition of Ni and Co fabricated by powder technology were investigated. The densifications of the prepared materials were accomplished by using vacuum sintering at 1450°C. Nearly full dense (W,Ti)C cemented carbides were obtained with a relative density of up to 99.7% with 30 wt.% Co and 99.9% with 30 wt.% Ni as a metallic binder. The average grain size of the (W,Ti)C-Co and the (W,Ti)C-Ni was decreased by increasing the metallic binder content. The hardness of the dense (W,Ti)C-15 wt%Co and (W,Ti)C-15 wt%Ni, was greater than that of the other related cemented carbides; in addition, the cobalt-based cemented carbides had greater hardness values than the nickel-based cemented carbides.

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Performance Evaluation on the Endmill of High Speed Machining for Selection of Tungsten Carbide (WC-Co) Material
Dong-Hee Kwon, Jeong-Suk Kim, Min-Wook Kim, Young-Keun Jeong, Myung-Chang Kang
Journal of Korean Powder Metallurgy Institute.2008; 15(5): 359. CrossRef

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