Journal of Powder Materials

Volume 17(4); August 2010

A study on Magnetic Properties of BaFe₁₂O₁₉ Fabricated by Ultrasonic Spray-pyrolysis Process Using Self-Assembly Method: Moon-Hee Choi, Ji-Hun Yu, Dong-Hwan Kim, Kook-Chae Chung, Yang-Do Kim; J Korean Powder Metall Inst. 2010;17(4):263-269.; DOI: https://doi.org/10.4150/KPMI.2010.17.4.263

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Hexagonal barium ferrite (BaFe_12O_19) nano-particles have been successfully fabricated by spraypylorysis process. BaFe_12O_19 precursor solutions were synthesized by self-assembly method. Diethyleneamine (DEA) surfactant was used to fabricate the micelle structure of Ba-DEA complex under various DEA concentrations. BaFe_12O_19 powders were synthesized with addition of Fe ions to Ba-DEA complex and then fabricated BaFe_12O_19 powders by spray-pyrolysis process at the temperature range of 800sim1000°C. The molar ratio of Ba/DEA and heat-treatment temperatures significantly affected the magnetic properties and morphology of BaFe_12O_19 powders. BaFe_12O_19 powders synthesized with Ba/DEA molar ratio of 1 and heat-treated at 900°C showed the coercive forces (iHc) of 4.2 kOe with average crystal size of about 100 nm.

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Synthesize of Nd₂Fe₁₄B Powders from 1-D Nd₂Fe₁₄B Wires using Electrospinning Process
Nu Si A Eom, Su Noh, Muhammad Aneeq Haq, Bum Sung Kim
Journal of Korean Powder Metallurgy Institute.2019; 26(6): 477. CrossRef

Synthesis and Characterization of Cu Nanofluid Prepared by Pulsed Wire Evaporation Method: Chang-Kyu Kim, Gyoung-Ja Lee, Chang-Kyu Rhee; J Korean Powder Metall Inst. 2010;17(4):270-275.; DOI: https://doi.org/10.4150/KPMI.2010.17.4.270

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Ethylene glycol-based Cu nanofluids were prepared by pulsed wire evaporation (PWE) method. The structural properties of Cu nanoparticles were studied by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). The average diameter and Brunauer Emmett Teller (BET) surface area of Cu nanoparticles were about 100 nm and 7.46;m2/g, respectively. The thermal conductivity and viscosity of copper nanofluid were measured as functions of Cu concentration and temperature. As the volume fraction of Cu nanoparticles increased, both the enhanced ratios of thermal conductivity and viscosity of Cu nanofluids increased. As the temperature increased, the enhanced ratio of thermal conductivity increased, but that ratio of viscosity decreased.

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Characterization of Classification of Synthesized Ni Nanopowders by Pulsed Wire Evaporation Method
Joong-Hark Park, Geon-Hong Kim, Dong-Jin Lee, Soon-Jik Hong
Journal of Korean Powder Metallurgy Institute.2017; 24(5): 389. CrossRef
Effect of Electrical Parameters and Surrounding Gas on the Electroexplosive Tungsten Nanopowders Characteristics
Young-Soon Kwon, Jin-Chun Kim, Alexander P. Ilyin, Olga B. Nazarenko, Dmitry V. Tikhonov
Journal of Korean Powder Metallurgy Institute.2012; 19(1): 49. CrossRef
Thermal conductivity enhancement of ZnO nanofluid using a one-step physical method
Gyoung-Ja Lee, Chang Kyu Kim, Min Ku Lee, Chang Kyu Rhee, Seokwon Kim, Chongyoup Kim
Thermochimica Acta.2012; 542: 24. CrossRef

A Study on Thermal Properties of Ethylene Glycol Containing Copper Oxide Nanoparticles: Chang-Kyu Kim, Gyoung-Ja Lee, Chang-Kyu Rhee; J Korean Powder Metall Inst. 2010;17(4):276-280.; DOI: https://doi.org/10.4150/KPMI.2010.17.4.276

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In the present work, ethylene glycol-based (EG) copper oxide nanofluids were synthesized by pulsed wire evaporation method. In order to explode the pure copper wire, high voltage of 23 kV was applied to the both ends of wire and argon/oxygen gas mixture was used as reactant gas. EG-based copper oxide nanofluids with different volume fraction were prepared by controlling explosion number of copper wire. From the transmission electron microscope (TEM) image, it was found that the copper oxide nanoparticles exhibited an average diameter about 100 nm with the oxide layer of 2~3 nm. The synthesized copper oxide consists of CuO/Cu_2O phases and the Brunauer Emmett Teller (BET) surface area was estimated to be 6.86;m2;g-1. From the analyses of thermal properties, it is suggested that viscosity and thermal conductivity of EG-based copper oxide nanofluids do not show temperature-dependent behavior over the range of 20 to 90°C. On the other hand, the viscosity and thermal conductivity of EG-based copper oxide nanofluids increase with volume fraction due to the active Brownian motion of the nanoparticles, i.e., nanoconvection.

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Thermal conductivity enhancement of ZnO nanofluid using a one-step physical method
Gyoung-Ja Lee, Chang Kyu Kim, Min Ku Lee, Chang Kyu Rhee, Seokwon Kim, Chongyoup Kim
Thermochimica Acta.2012; 542: 24. CrossRef
Fabrication of Ni-free Fe-based Alloy Nano Powder by Pulsed Wire Evaporation in Liquid: Part I. Effect of Wire Diameter and Applied Voltage
Ho-Jin Ryu, Yong-Heui Lee, Kwang-Ug Son, Young-Min Kong, Jin-Chun Kim, Byoung-Kee Kim, Jung-Yeul Yun
Journal of Korean Powder Metallurgy Institute.2011; 18(2): 105. CrossRef
Fabrication of Ni-free Fe-based Alloy Nano Powder by Pulsed Wire Evaporation in Liquid: Part 2. Effect of Solvent and Comparison of Fabricated Powder owing to Fabrication Method
Ho-Jin Ryu, Yong-Heui Lee, Kwang-Ug Son, Young-Min Kong, Jin-Chun Kim, Byoung-Kee Kim, Jung-Yeul Yun
Journal of Korean Powder Metallurgy Institute.2011; 18(2): 112. CrossRef
Synthesis and Characterization of (AgSbTe2)15(GeTe)85Thermoelectric Powder by Gas Atomization Process
Hyo-Seob Kim, Jin-Kyu Lee, Jar-Myung Koo, Byong-Sun Chun, Soon-Jik Hong
Journal of Korean Powder Metallurgy Institute.2011; 18(5): 449. CrossRef

Preparation of C Doped TiO₂ Photocatalyst Activating to Visible Irradiation and Investigation of Its Photocatalytic Activity: In-Chul Yeo, In-Cheol Kang; J Korean Powder Metall Inst. 2010;17(4):281-288.; DOI: https://doi.org/10.4150/KPMI.2010.17.4.281

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Abstract PDF: A carbon doped TiO_2 (C-TiO_2) photocatalyst, which shows good photocatalytic activity to Ultraviolet irradiation and visible irradiation, was successfully prepared by co-grinding of TiO_2 with ethanol or Activated Carbon(C), followed by heat treatment at 200°C in air for 60 min. Ethanol and C were used as a representative agent of liquid and solid for carbon doping. Their influence on improving photocatalytic ability and carbon doping degree was studied with degradation of methyl orange and XPS analysis. The product prepared by co-grinding of TiO_2 with Ethanol had Ti-C and C-O chemical bonds and showed higher photocatalytic activity than the product prepared by co-grinding of TiO_2 with C, where just C-O chemical bond existed. As a result, mechanochemical route is useful to prepare a carbon doped TiO_2 photocatalyst activating to visible irradiation, where the solid-liquid operation is more effective than solid-solid operation to obtain a carbon doped TiO_2.

Sintering and Microwave Dielectric Properties of Bi₁₈(Ca_0.725Zn_0.275)₈Nb₁₂O₆₅ [BCZN] Dielectrics with V₂O₅ Addition: Young-Jong Lee, Sung-Soo Kim; J Korean Powder Metall Inst. 2010;17(4):289-294.; DOI: https://doi.org/10.4150/KPMI.2010.17.4.289

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Abstract PDF: For the aim of low-temperature co-fired ceramic microwave components, sintering behavior and microwave properties (dielectric constant varepsilon_r, quality factor Q, and temperature coefficient of resonant frequency tau_f) are investigated in Bi_18O(Ca_0.725Zn_0.275)_8Nb_12O_65 [BCZN] ceramics with addition of V_2O_5. The specimens are prepared by conventional ceramic processing technique. As the main result, it is demonstrated that the additives (V_2O_5) show the effect of lowering of sintering temperature and improvement of microwave properties at the optimum additive content. The addition of 0.25 wt% V_2O_5 lowers the sintering temperature to 890°C utilizing liquidphase sintering and show the microwave dielectric properties (dielectric constant varepsilon_r = 75, quality factor Qtimesf = 572 GHz, temperature coefficient of resonance frequency tau_f;=;-10;ppm/°C). The estimated microwave dielectric properties with V_2O_5 addition (increase of varepsilon_r, decrease of Qtimesf, shift of tau_f to negative values) can be explained by the observed microstrucure (sintered density, abnormal grain structure) and possibly high-permittivity Bi_18Zn_8Nb_12O_65 (BZN) phase determined by X-ray diffraction.

Synthesis of Core/shell Structured Ag/C Nano Particles and Properties on Annealing Conditions: S.H. Jun, Y.R. Uhm, C.K. Rhee; J Korean Powder Metall Inst. 2010;17(4):295-301.; DOI: https://doi.org/10.4150/KPMI.2010.17.4.295

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Multi shell graphite coated Ag nano particles with core/shell structure were successfully synthesized by pulsed wire evaporation (PWE) method. Ar and CH_4 (10 vol.%) gases were mixed in chamber, which played a role of carrier gas and reaction gas, respectively. Graphite layers on the surface of silver nano particles were coated indiscretely. However, the graphite layers are detached, when the particles are heated up to 250°C in the air atmosphere. In contrast, the graphite coated layer was stable under Ar and N_2 atmosphere, though the core/shell structured particles were heated up to 800°C. The presence of graphite coated layer prevent agglomeration of nanoparticles during heat treatment. The dispersion stability of the carbon coated Ag nanoparticles was higher than those of pure Ag nanoparticles.

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Fabrication of Carbon-coated Tin Nano-powders by Electrical Wire Explosion in Liquid Media and its Electrochemical Properties
Yoo-Young Kim, Ju-Suck Song, Kwon-Koo Cho
Journal of Korean Powder Metallurgy Institute.2016; 23(4): 317. CrossRef
Study of Mössbauer Spectroscopy for Iron Oxides Synthesized by Pulsed Wire Evaporation (PEW)
Young Rang Uhm
Journal of the Korean Magnetics Society.2014; 24(5): 135. CrossRef

Refinement Behavior of Coarse Magnesium Powder by High Energy Ball Milling (HEBM): Joon-Woo Song, Hyo-Seob Kim, Hong-Moule Kim, Taek-Soo Kim, Soon-Jik Hong; J Korean Powder Metall Inst. 2010;17(4):302-311.; DOI: https://doi.org/10.4150/KPMI.2010.17.4.302

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In this research, the refinement behavior of the coarse magnesium powders fabricated by gas atomization was investigated as a function of milling time using a short duration high-energy ball milling equipment, which produces fine powders by means of an ultra high-energy within a short duration. The microstructure, hardness, and formability of the powders were investigated as a function of milling time using X-ray diffraction, scanning electron microscopy, Vickers micro-hardness tester and magnetic pulsed compaction. The particle morphology of Mg powders changed from spherical particles of feed metals to irregular oval particles, then platetype particles, with increasing milling time. Due to having HCP structure, deformation occurs due to the existence of the easily breakable C-axis perpendicular to the base, resulting in producing plate-type powders. With increasing milling time, the particle size increased until 5 minutes, then decreased gradually reaching a uniform size of about 50 micrometer after 20 minutes. The relative density of the initial power was 98% before milling, and mechanically milled powder was 92~94% with increase milling time (1~5 min) then it increased to 99% after milling for 20 minutes because of the change in particle shapes.

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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
Fabrication of Fe coated Mg Based Desulfurization Powder by Mechanical Alloying Process
Joon-Woo Song, Otaduy Guillermo, Byong-Sun Chun, Soon-Jik Hong
Journal of Korean Powder Metallurgy Institute.2012; 19(3): 226. CrossRef
Characteristics of Indium Dissolution of Waste LCD Panel Powders Fabricated by High Energy Ball Milling (HEBM) Process with Milling Time
Hyo-Seob Kim, Jun-Je Sung, Cheol-Hee Lee, Hyun-Seon Hong, Soon-Jik Hong
Journal of Korean Powder Metallurgy Institute.2011; 18(4): 378. CrossRef
Microstructure and Mechanical Properties of Nano-sized Ti-35%Nb-7%Zr-10%CPP Composite Fabricated by Pulse Current Activated Sintering
Kee-Do Woo, Duck-Soo Kang, Sang-Hyuk Kim, Sang-Hoon Park, Ji-Young Kim, Hye-Rim Ko
Journal of Korean Powder Metallurgy Institute.2011; 18(2): 188. CrossRef

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.

Characteristics of Micro EDM using Wire Electrical Discharge Grinding for Al₂O₃/CNTs Hybrid Materials: Hyun-Seok Tak, Jong-Hun Kim, Han-Suk Lim, Choon-Tae Lee, Young-Keun Jeong, Myung-Chang Kang; J Korean Powder Metall Inst. 2010;17(4):319-325.; DOI: https://doi.org/10.4150/KPMI.2010.17.4.319

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Electrical discharge machining (EDM) is an attractive machining technique but it requires electrically conductive ceramic materials. In this study, Alumina matrix composites reinforced with CNTs were fabricated through CNT purification, mixing, compaction and spark plasma sintering (SPS) processes. Al_2O_3 nanocomposites with the different CNT concentrations were synthesized. The mechanical and electrical characteristics of Al_2O_3/CNTs composites were examined in order to apply the materials to the EDM process. In addition, micro-EDM using wire electrical discharge grinding (WEDG) was conducted under the various EDM parameters to investigate the machining characteristics of machined hole by Field Emission Scanning Electron Microscope (FE-SEM). The results show that Al_2O_3/CNTs 10%Vol. was more suitable than the other materials because high conductivity and large discharge energy caused violent sparks resulting in bad machining accuracy and surface quality.

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Development of Vibration Assisted Hybrid Femtosecond Laser Ultra-precision Machining System and Cu-Zn alloy Application
Won-Suk Choi, Ji-Wook Yoon, Sung-Hak Cho, Myung-Chang Kang
Journal of Korean Powder Metallurgy Institute.2013; 20(4): 308. CrossRef
Machinability Evaluation of Hybrid Ti2Ceramic Composites with Conductivity in Micro Electrical Discharge Drilling Operation
Jae-Young Heo, Young-Keun Jeong, Myung-Chang Kang, Ahmed Busnaina
Journal of Korean Powder Metallurgy Institute.2013; 20(4): 285. CrossRef

The Effect of Electrical Characteristics and Electrode Shape on Alignment of Multi-walled Carbon Nanotubes: Se-Hun Kwon, Young-Keun Jeong, Chang-Sik Jung, Myung-Chang Kang, Hyung-Woo Lee; J Korean Powder Metall Inst. 2010;17(4):326-335.; DOI: https://doi.org/10.4150/KPMI.2010.17.4.326

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Abstract PDF: In this paper, the effect of electrical characteristics and electrode shape on the alignment and attachment of multi-walled carbon nanotubes (MWNTs) has been studied. The attraction and alignment of MWNTs between the gaps has been investigated by applying electric field which is called electrophoresis and dielectrophoresis. According to the frequency of electric field, positive or negative dielectrophoretic force can be determined. The concentration of MWNTs solution was 5;µg/ml, and a droplet of 1.0sim1.5;µl was dropped between two electrodes. Through the repeated experiments, the optimal electrical conditions for aligning and attaching MWNTs in the desired places were obtained. Since the frequency range of 100 kHz~10 MHz generated positive dielectrophoretic force, MWNTs were attracted and aligned between the gaps with this frequency range. For generating enough force to attract MWNTs, the appropriate voltage range was 0.3sim1.3;V_rms/µm. Furthermore, the effect of electrode shape on the alignment of MWNTs was investigated. A single MWNT attachment was accomplished on the round shaped with 70% yield.

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; J Korean Powder Metall Inst. 2010;17(4):336-341.; DOI: https://doi.org/10.4150/KPMI.2010.17.4.336

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The present study focused on the synthesis of Bi-Sb-Te-based thermoelectric powder by an oxidereduction process. The phase structure, particle size of the synthesized powders were analyzed using XRD and SEM. The synthesized powder was sintered by the spark plasma sintering method. The thermoelectric property of the sintered body was evaluated by measuring the Seebeck coefficient and specific electric resistivity. The Bi_0.5Sb_1.5Te_3 powder had been synthesized by a combination of mechanical milling, calcination and reduction processes using mixture of Bi_2O_3, Sb_2O_3 and TeO_2 powders. The sintered body of the Bi_0.5Sb_1.5Te_3 powder synthesized by an oxide-reduction process showed p-type thermoelectric characteristics, even though it had lower thermoelectric properties than the sintered body of the Bi_0.5Sb_1.5Te_3 thermoelectric powder synthesized by the conventional melting-crushing method.

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Fabrication of Bi2Te2.5Se0.5 by Combining Oxide-reduction and Compressive-forming Process and Its Thermoelectric Properties
Young Soo Lim, Gil-Geun Lee
journal of Korean Powder Metallurgy Institute.2024; 31(1): 50. CrossRef
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
The Electric and Thermal Properties of Spark Plasma Sintered Bi0.5Sb1.5Te3
Gil-Geun Lee, Young-Hoon Choi, Gook-Hyun Ha
Journal of Korean Powder Metallurgy Institute.2012; 19(4): 285. CrossRef
Synthesis and Characterization of (AgSbTe2)15(GeTe)85Thermoelectric Powder by Gas Atomization Process
Hyo-Seob Kim, Jin-Kyu Lee, Jar-Myung Koo, Byong-Sun Chun, Soon-Jik Hong
Journal of Korean Powder Metallurgy Institute.2011; 18(5): 449. 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 and Characterization of Glold Nanofluid Prepared by the Solution Plasma Processing: Yong-Kang Heo, Sang-Yul Lee; J Korean Powder Metall Inst. 2010;17(4):342-346.; DOI: https://doi.org/10.4150/KPMI.2010.17.4.342

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Abstract PDF: In the present work, water-based gold nanofluids were synthesized by the solution plasma processing (SPP). The size distribution and the shape of gold nanoparticles in the nanofluids were investigated using high resolution transmission electron microscopy (HR-TEM). The dispersion stability of gold nanofluids was characterized using zeta potential, as well. The thermal properties of gold nanofluids were measured by utilizing lambda measurement device. Nanofluids containing nanoparticles with 64.0pm42.1;nmsim18.10pm5.0;nm in diameter were successfully synthesized. As diameter of nanoparticles decreased, dispersion stability of nanofluids increased and the enhanced ratio of thermal conductivity increased. The nanofluid with nanoparticles of 18.10;pm;5.0;nm in diameter showed approximately 3% improvement in thermal conductivity measurement and this could be due to the enhanced Brownian movement.

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