Journal of Powder Materials

Volume 15(5); October 2008

Consolidation of p-type Fe(Mn)Si₂ Thermoelectric Powder and Microstructure: J.S. Shim, S.J. Hong, B.S. Chun; J Korean Powder Metall Inst. 2008;15(5):345-351.; DOI: https://doi.org/10.4150/KPMI.2008.15.5.345

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Abstract PDF: The effects of the dopant (Mn) ratio on the microstructure and thermoelectric properties of FeSi_2 alloy were studied in this research. The alloy was fabricated by a combination process of ball milling and high pressure pressing. Structural behavior of the sintered bulks were systematically investigated by XRD, SEM, and optical microscopy. With increasing dopan (Mn) ratio, the density and varepsilon-FeSi phase of the sintered bulks increased and maximum density of 94% was obtained in the 0.07% Mn-doped alloy. The sintered bulks showed fine microstructure of alpha-Fe_2Si_5, varepsilon-FeSi and beta-FeSi_2 phase. The semiconducting phase of beta-FeSi_2 was transformed from alpha-Fe_2Si_5+varepsilon-FeSi phase by annealing.

Synthesis of Bi-Sb-Te Thermoelectric Nanopowder by the Plasma Arc Discharge Process: Gil-Geun Lee, Dong-Youl Lee, Gook-Hyun Ha; J Korean Powder Metall Inst. 2008;15(5):352-358.; DOI: https://doi.org/10.4150/KPMI.2008.15.5.352

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The present study focused on the synthesis of a bismuth-antimony-tellurium-based thermoelectric nanopowders using plasma arc discharge process. The chemical composition, phase structure, particle size of the synthesized powders under various synthesis conditions were analyzed using XRF, XRD and SEM. The powders as synthesized were sintered by the plasma activated sintering. The thermoelectric properties of sintered body were analyzed by measuring Seebeck coefficient, specific electric resistivity and thermal conductivity. The chemical composition of the synthesized Bi-Sb-Te-based powders approached that of the raw material with an increasing DC current of the are plasma. The synthesized Bi-Sb-Te-based powder consist of a mixed phase structure of the Bi_0.5Sb_1.5Te_3, Bi_2Te_3 and Sb_2Te_3 phases. This powder has homogeneous mixing state of two different particles in an average particle size; about 100nm and about 500nm. The figure of merit of the sintered body of the synthesized 18.75 wt.%Bi-24.68 wt.%Sb-56.57 wt.%Te nanopowder showed higher value than one of the sintered body of the mechanically milled 12.64 wt.%Bi-29.47 wt.%Sb-57.89 wt.%Te powder.

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Synthesis of N-type Bi2Te2.7Se0.3 Compounds through Oxide-Reduction Process and Related Thermoelectric Transport Properties
Young Soo Lim, Bae Gun Park, Gil-Geun Lee
Korean Journal of Metals and Materials.2022; 60(6): 463. CrossRef
Thermoelectric Properties of Bi2Te2.7Se0.3Powder Synthesized by an Oxide-Reduction Process
Bae-Gun Park, Gil-Geun Lee, Woo-Yeol Kim, Gook-Hyun Ha
Journal of Korean Powder Metallurgy Institute.2011; 18(5): 437. CrossRef
Synthesis of Bi-Sb-Te-based Thermoelectric Powder by an Oxide-reduction Process
Gil-Geun Lee, Sung-Hyun Kim, Gook-Hyun Ha, Kyung-Tae Kim
Journal of Korean Powder Metallurgy Institute.2010; 17(4): 336. CrossRef

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; J Korean Powder Metall Inst. 2008;15(5):359-364.; DOI: https://doi.org/10.4150/KPMI.2008.15.5.359

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To satisfy the demand of higher cutting performance, mechanical properties with tungsten carbide (WC-Co) tool materials were investigated. Hardness and transverse rupture strength with WC grain size, Co content and density were measured. Compared to H, K, and S manufacture maker as tungsten carbide (WC-Co) tool materials were used for high-speed machining of end-milling operation. The three tungsten carbide (WC-Co) tool materials were evaluated by cutting of STD 11 cold-worked die steel (HRC25) under high-speed cutting condition. Also, tool life was obtained from measuring flank wear by CCD wear measuring system. Tool dynamometer was used to measure cutting force. The cutting force and tool wear are discussed along with tool material characteristics. Consequently, the end-mill of K, H manufacture maker showed higher wear-resistance due to its higher hardness, while the S maker endmill tool showed better performance for high metal removal.

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Tool Wear Characteristics of Tungsten Carbide Implanted with Plasma Source Nitrogen Ions in High-speed Machining
Sung-Ho Park, Duck Hyun Wang
Journal of the Korean Society of Manufacturing Process Engineers.2022; 21(5): 34. CrossRef

Analysis of Densification Behavior during Powder Equal Channel Angular Pressing using Critical Relative Density Model: Cheon-Hee Bok, Ji-Hoon Yoo, Seung-Chae Yoon, Taek-Soo Kim, Byong-Sun Chun, Hyoung-Seop Kim; J Korean Powder Metall Inst. 2008;15(5):365-370.; DOI: https://doi.org/10.4150/KPMI.2008.15.5.365

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In this study, bottom-up powder processing and top-down severe plastic deformation processing approaches were combined in order to achieve both full density and grain refinement with least grain growth. The numerical modeling of the powder process requires the appropriate constitutive model for densification of the powder materials. The present research investigates the effect of representative powder yield function of the Shima-Oyane model and the critical relative density model. It was found that the critical relative density model is better than the Shima-Oyane model for powder densification behavior, especially for initial stage.

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Analysis of Densification Behavior of Magnesium Powders in Extrusion using the Critical Relative Density Model
Seung-Chae Yoon, Hong-Jun Chae, Taek-Soo Kim, Hyoung-Seop Kim
Journal of Korean Powder Metallurgy Institute.2009; 16(1): 50. 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.

Consolidation of Segment Powder for Diamond Tool by Magnetic Pulsed Compaction: J.S. Yun, J.G. Lee, M.K. Lee, C.K. Rhee, M.S. Park, S.J. Hong; J Korean Powder Metall Inst. 2008;15(5):378-385.; DOI: https://doi.org/10.4150/KPMI.2008.15.5.378

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This article presents the successful consolidation of the mixed Co and Diamond powders for a drilling segment by the combined application of magnetic pulsed compaction (MPC) and subsequent sintering, and their properties were analyzed. Homogeneous hardness (Hv 220) and density (97%) of sintered bulks fabricated by MPC were obtained by the new technique, where higher pressure has been employed for short period of time than that of general process. A fine microstructure and homogeneous hardness in the consolidated bulk were observed without cracks. Relatively higher drilling speed of 9.61 cm/min and life time of 6.55 m were found to the MPCed specimens, whereas the value of the specimens fabricated by general process was 11.71 cm/min and 7.96 m, respectively. A substantial improvement of mechanical properties of segment was achieved through this study.

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Machining Characteristics of Micro Structure using Single-Crystal Diamond Tool on Cu-plated Mold
Chang-Eui Kim, Eun-chae Jeon, Tae-Jin Je, Myung Chang Kang
Journal of Korean Powder Metallurgy Institute.2015; 22(3): 169. CrossRef
Comparison of Micro Trench Machining Characteristics with Nonferrous Metal and Polymer using Single Diamond Cutting Tool
Hwan-Jin Choi, Eun-Chae Jeon, Doo-Sun Choi, Tae-Jin Je, Myung-Chang Kang
Journal of Korean Powder Metallurgy Institute.2013; 20(5): 355. CrossRef
Comparison of Machinability Between PCD Tool and SCD Tool for Large Area Mirror Surface Machining Using Multi-tool by Planer
Chang-Eui Kim, Hwan-Jin Choi, Eun-Chae Jeon, Tae-Jin Je, Myung-Chang Kang
Journal of Korean Powder Metallurgy Institute.2013; 20(4): 297. CrossRef
Consolidation of mixed diamond and cobalt granule powders by magnetic pulsed compaction
Jung G. Lee, M.K. Lee, S.J. Hong, H.W. Lee, S.P. Pyun, C.K. Rhee
Materials Letters.2010; 64(1): 35. CrossRef

Synthesis of Silver Nano-particles by Homogeneous Precipitation: Won-Mo Kang, Ho-Kun Kim; J Korean Powder Metall Inst. 2008;15(5):386-392.; DOI: https://doi.org/10.4150/KPMI.2008.15.5.386

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Abstract PDF: Silver particles were synthesized from silver nitrate by homogeneous precipitation and chemical reduction methods involving the intermediate silver cyanate. The obtained silver particles were characterized by XRD, SEM, TEM, and BET. Urea which could prevent the agglomeration of the reduced silver particles was used as a homogeneous precipitator. The spherical silver particles with average particle diameter of 100 nm were obtained under the optimum reaction conditions. The optimum synthetic conditions were found as follows: reaction temperature 100°C, reaction time 60 min, concentration of silver nitrate 1times10-2 mol, urea 5times10-3 mol, and sodium citrate 8.5times10-4 mol. The phase of obtained silver particles was crystalline state and the silver particles were relatively dense, which had the surface area of 0.7571;m2/g.

A Study on Detection Characteristics of Cadmium and Lead for Bi Nanopowder-Labeled Electrode: Gyeoung-Ja Lee, Hyoun-Jin Kim, Hi-Min Lee, Sang-Hoon Lee, Min-Ku Lee, Chang-Kyu Lee; J Korean Powder Metall Inst. 2008;15(5):393-398.; DOI: https://doi.org/10.4150/KPMI.2008.15.5.393

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Abstract PDF: Trace analysis of Cd and Pb at surface modified thick film graphite electrode with Bi nanopowder has been carried out using square-wave anodic stripping voltammetry (SWASV) technique. Bi nanopowder synthesized by gas condensation (GC) method showed the size of 50sim100 nm with BET surface area, A_BET=6.8m2g-l. For a strong adhesion of the Bi nanopowder onto the screen printed carbon paste electrode, nafion solution was added into Bi-containing suspension. From the SWASV, it was found that the Bi nanopowder electrode exhibited a well-defined responses relating to the oxidations of Cd and Pb. The current peak intensity increased with increasing concentration of Cd and Pb. From the linear relationship between Cd/Pb concentrations and peak current, the sensitivity of the Bi nanopowder electrode was quantitatively estimated. The detection limit of the electrode was estimated to be 0.15µg/l and 0.07µg/l for Cd and Pb, respectively, on the basis of the signal-to-noise characteristics (S/N=3) of the response for the 1.0µg/l solution under a 10 min accumulation.

Optimization of VUV Characteristics of M₃MgSi₂O₈:Eu²⁺ (M=Ca, Sr, Ba) Phosphor by Spray Pyrolysis: You-Ri Jung, Kyeong-Youl Jung; J Korean Powder Metall Inst. 2008;15(5):399-404.; DOI: https://doi.org/10.4150/KPMI.2008.15.5.399

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Abstract PDF: Spray pyrolysis was applied to prepare M_3MgSi_2O_8:Eu2+ (M=Ca, Sr, Ba) blue phosphor powder. The library of a Ca-Sr-Ba ternary system was obtained by a combinatorial method combined with the spray pyrolysis in order to optimize the luminescent property under vacuum ultraviolet (VUV) excitation. 10 potential compositions were chosen from the first screening. The emission shifted to longer wavelength as Ca became a dominant element and the emission intensity was greatly reduced in the composition region at which Ba is dominant element. On the base of the first screening result, the second fine tuning was carried out in order to optimize the luminescence intensity under VUV excitation. The optimal composition for the highest luminescence intensity was (Ca_1.7,;Sr_0.3,;Ba_1.0)Si_2O_8:Eu2+ which had the color coordinate of (0.152, 0.072) and about 64% emission intensity of BaMgAl_10O_17 (BAM) phosphor.

Evaluation of Ni-YSZ Anode fabricated by Spark Plasma Sintering for SOFC Application: Se-Hun Chang, Jung-Chul Choi, Se-Weon Choi, Ho-Sung Kim, Ik-Hyun Oh; J Korean Powder Metall Inst. 2008;15(5):405-410.; DOI: https://doi.org/10.4150/KPMI.2008.15.5.405

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Abstract PDF: SOFC (Solid Oxide Fuel Cell) Ni-YSZ anode was fabricated by the spark plasma sintering (SPS) process and its microstructure and electrical properties were investigated in this study. The spark plasma sintering process was carried out at 800sim1000°C for holding time of 5 min under 40 MPa. To fabricate Ni-YSZ anode, the SPS processed specimens were reduced at 800°C under H_2 atmosphere. The reduced specimens showed relative density of 48.4sim64.8% according to sintering temperature. And also, the electrical conductivity of reduced specimens after sintering at 900 and 1000°C showed 480sim600 (S/cm) values at the measuring range of 600sim900°C.

High Pressure Liquid Jet Technology for Nano Particles Production: Marian Mazurkiewicz, Chang-Kyu Rhee, Bogumil Weglinski; J Korean Powder Metall Inst. 2008;15(5):411-421.; DOI: https://doi.org/10.4150/KPMI.2008.15.5.411

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Abstract PDF: Principles and historical background of high pressure liquid jet (HPLJ) technology is presented in the paper. This technology can be applied, among others, for production of nano particles. This target can be achieved in various type of disintegration systems developed and designed on the base of this technology. The paper describes principles of two examples of such systems: HPLJ-reactor, called also a linear comminuting system, HPLJ- centrifugal comminuting system, which prototypes have been manufactured. A linear mill, being high energy liquid jet reactor, has been developed and tested for micronization of various types of materials. The results achieved so far, and presented in the paper, show its potential for further improvement toward nano-size particle production. Flexibility of adjustment of the reactors and the mechanism of the process allows for the creation of particles with unprecedented rheology. The reactor can be especially suitable to micronize, mix and densify materials with a wide range of mechanical properties for various industrial needs. Presented prototypes of comminution systems generate interesting potentials toward production of nano particles. Their performance, based on up today research, confirms expected high efficiency of materials disintegration, which opens a new challenge for industrial applications. The paper points out benefits and area of possible applications of presented technology.

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