Journal of Powder Materials

Volume 16(4); August 2009

Fabrication and Characterization of Carbon-Coated Cu Nanopowders by Pulsed Wire Evaporation Method: H.M. Lee, J.H. Park, S.M. Hong, Y.R. Uhm, C.K. Rhee; J Korean Powder Metall Inst. 2009;16(4):243-248.; DOI: https://doi.org/10.4150/KPMI.2009.16.4.243

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Carbon-coated Cu nanopowders with core/shell structure have been successfully fabricated by pulsed wire evaporation (PWE) method, in which a mixed gas of Ar/CH_4 (10 vol.%) was used as an ambient gas. The characterization of the samples was carried out using x-ray diffraction (XRD), scanning electron microscope (SEM), and high resolution transmission electron microscope (HRTEM). It was found that the nanoparticles show a spherical morphology with the size ranging of 10-40 nm and are covered with graphite layers of 2-4 nm. When oxygen-passivated Cu nanopowders were annealed under flowing argon gas (600 and 800°C), the crystallinity of Cu_2O phase and the particle size gradually increased. On the other hand, carbon-coated Cu nanopowders remained similar to as-prepared case with no additional oxide or carbide phases even after the annealing, indicating that the metal nanoparticles are well protected by the carbon-coating layers.

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Improved oxidation stability of carbon-coated Ni nanoparticles synthesized by one-step electrical wire explosion
Jun-Hyeok Lee, Byung-Hoon Kim, Gyoung-Ja Lee
Materials Chemistry and Physics.2022; 276: 125410. 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
A Study on Thermal Properties of Ethylene Glycol Containing Copper Oxide Nanoparticles
Chang-Kyu Kim, Gyoung-Ja Lee, Chang-Kyu Rhee
Journal of Korean Powder Metallurgy Institute.2010; 17(4): 276. CrossRef
Synthesis and Characterization of Cu Nanofluid Prepared by Pulsed Wire Evaporation Method
Chang-Kyu Kim, Gyoung-Ja Lee, Chang-Kyu Rhee
Journal of Korean Powder Metallurgy Institute.2010; 17(4): 270. CrossRef
Synthesis of Core/shell Structured Ag/C Nano Particles and Properties on Annealing Conditions
S.H. Jun, Y.R. Uhm, C.K. Rhee
Journal of Korean Powder Metallurgy Institute.2010; 17(4): 295. CrossRef
Synthesis and Characterization of Glold Nanofluid Prepared by the Solution Plasma Processing
Yong-Kang Heo, Sang-Yul Lee
Journal of Korean Powder Metallurgy Institute.2010; 17(4): 342. CrossRef

Warm Compaction of Fe-Si/Fe Powder Mixture and its Magnetic Property: Se-Hoon Kim, Myung-Jin Suk, Young-Do Kim; J Korean Powder Metall Inst. 2009;16(4):249-253.; DOI: https://doi.org/10.4150/KPMI.2009.16.4.249

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Abstract PDF: 3-D shape soft magnetic composite parts can be formed by general compaction method of powder metallurgy. In this study, the results on the high density nanostructured Fe-Si/Fe composite prepared by a warm compaction method were presented. Ball-milled Fe-25 wt.%Si powder, pure Fe powder and Si-polymer were mixed and then the powder mixture was compacted at various temperatures and pressures. Pore free density of samples up to 95% theoretical value has been obtained. The warm compacted sample prepared at 650 MPa and 240°C had highest compaction properties in comparison with other compacts prepared at 300, 400 MPa and room temperature and 120°C. The magnetic properties such as core loss, magnetization saturation and coercivity were measured by B-H curve analyzer and vibration sample magnetometer.

Effects of Process Parameters on the Powder Characteristics of Uranium Oxide Kernel Prepared by Sol-gel Process: Yeon-Ku Kim, Kyung-Chai Jeong, Seung-Chul Oh, Dong-Soo Suhr, Moon-Sung Cho; J Korean Powder Metall Inst. 2009;16(4):254-261.; DOI: https://doi.org/10.4150/KPMI.2009.16.4.254

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Abstract PDF: In this study, we investigated the unit process parameters in spherical UO_2 kernel preparation. Nearly perfect spherical UO_3 microspheres were obtained from the 0.6M of U-concentration in the broth solution, and the microstructure of the UO_2 kernel appeared the good results in the calcining, reducing, and sintering processes. For good sphericity, high density, suitable microstructure, and no-crack final UO_2 microspheres, the temperature control range in calcination process was 300sim450°C, and the microstructure, the pore structure, and the density of UO_2 kernel could be controlled in this temperature range. Also, the concentration changes of the ageing solution in aging step were not effective factor in the gelation of the liquid droplets, but the temperature change of the ageing solution was very sensitive for the final ADU gel particles.

Fabrication and Characterization of Porous Nickel Membrane for High Precision Gas Filter by In-situ Reduction/Sintering Process: Nam-Hoon Kim, Han-Bok Song, Sung-Churl Choi, Yong-Ho Choa; J Korean Powder Metall Inst. 2009;16(4):262-267.; DOI: https://doi.org/10.4150/KPMI.2009.16.4.262

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Disk type porous nickel membrane was fabricated by in-situ reduction/sintering process using compacted NiO/PMMA (PMMA; Polymethyl methacrylate) mixture at 800°C in hydrogen atmosphere. The porosity (49sim58%) of these membrane was investigated as an amount of PMMA additive. The thermal decomposition and reduction behavior of NiO/PMMA were analyzed by TG/DTA in hydrogen atmosphere and the activation energy for the hydrogen reduction of NiO and thermal degradation of PMMA was calculated as 61.1 kJ/mol, evaluated by Kissinger method. Finally, the filtering performance and pressure drop were measured by particle counting system.

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Fabrication of Porous Ni by Freeze Drying and Hydrogen Reduction of NiO/Camphene Slurry
Jae-Hun Jeong, Sung-Tag Oh, Chang-Yong Hyun
Journal of Korean Powder Metallurgy Institute.2019; 26(1): 6. CrossRef
Fabrication of Porous W by Heat Treatment of Pore Forming Agent of PMMA and WO3 Powder Compacts
Ki Cheol Jeon, Young Do Kim, Myung-Jin Suk, Sung-Tag Oh
Journal of Korean Powder Metallurgy Institute.2015; 22(2): 129. CrossRef
Fabrication of Porous Cu by Freeze-drying Process of Camphene Slurry with CuO-coated Cu Powders
Su-Ryong Bang, Sung-Tag Oh
Journal of Korean Powder Metallurgy Institute.2014; 21(3): 191. CrossRef
Fabrication of Porous Ti by Freeze-Drying and Heat Treatment of TiH2/Camphene Slurries
한길 서, 명진 석, 영도 김, 승탁 오
Korean Journal of Materials Research.2013; 23(6): 339~343. CrossRef
Freeze Drying for Porous Mo with Sublimable Vehicles of Eutectic System
Gyu-Tae Lee, Han Gil Seo, Myung-Jin Suk, Sung-Tag Oh
Journal of Korean Powder Metallurgy Institute.2013; 20(4): 253. CrossRef

A Basic Study on the Fabrication of W-M(M=Cu, Sn, Ni) System High Density Composite (I): Tak-Soon Jang, Jun-Hee Hong, Tae-Haeng Lee, Jar-Myung Koo, Chang-Bin Song; J Korean Powder Metall Inst. 2009;16(4):268-274.; DOI: https://doi.org/10.4150/KPMI.2009.16.4.268

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For the purpose of obtaining basic information on the development of lead-free materials, a high density composites (a) W-Cu, (b) W-Sn (c)W-Cu-Sn and (d) W-Cu-Ni were fabricated by the P/M method. The particle size of used metal powders were under 325 mesh, inner size of compaction mould was phi8 mm, and compaction pressure was 400 MPa. A High density composite samples were sintered at a temperature between 140°C and 1050°C for 1 hour under Ar atmosphere. The microstructure, phase transformation and physical properties of the sintered samples were investigated. As the results, the highest relative density of 95.86% (10.87 g/cm3) was obtained particularly in the sintered W-Cu-Sn ternary system sample sintered at 450 for 1hr. And, Rockwell hardness (HRB) of 70.0 was obtained in this system.

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Fabrication and Performance Analysis of Environment Friendly Double Core Bullets for Small Arms
Jun-Hee Hong, Tak-Soon Jang, Chang-Bin Song, Dae-Wha Kang
Journal of the Korea Institute of Military Science and Technology.2011; 14(3): 345. CrossRef
Design and Performance Analysis of Environment Friendly Double Core Bullets for Small Arms
Jun-Hee Hong, Tak-Soon Jang, Chang-Bin Song, Byung-In Kim
Journal of the Korea Institute of Military Science and Technology.2011; 14(2): 264. CrossRef

The Aging Characteristics of Mg-6 wt.% Al-1 wt.% Zn Alloy Prepared by Gas Atomization: Du-Hyung Lee, Bo-Sik Kim, Si-Young Chang; J Korean Powder Metall Inst. 2009;16(4):275-279.; DOI: https://doi.org/10.4150/KPMI.2009.16.4.275

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Abstract PDF: The aging characteristics of gas atomized Mg-6 wt.% Al-1 wt.% Zn alloy were investigated and compared to those of cast Mg-6 wt.% Al alloy. The gas atomized Mg-6 wt.% Al-1wt.% Zn alloy powders had spherical morphology between 1 and 100 mu m in diameter. After compaction under the pressure of 700 MPa at 320°C for 10 min, the Mg-6 wt.% Al-1 wt.% Zn alloy showed a grain size of approximately 40 mu m which is smaller than that of the cast Mg-6 wt.% Al alloy, and a relative compact density of approximately 93%. After ageing, the Mg-6 wt.% Al-1 wt.% Zn alloy showed much faster peak hardness than cast Mg-6 wt.% Al alloy. The Mg-6 wt.% Al-1 wt.% Zn alloy showed the new fine precipitations with ageing time, while the cast Mg-6 wt.% Al alloy was almost similar morphology.

Microstructure and Properties of Cu Dispersed Al₂O₃ Nanocomposites Prepared by Pressureless Sintering: Kyong-Hwan Lee, Sung-Tag Oh; J Korean Powder Metall Inst. 2009;16(4):280-284.; DOI: https://doi.org/10.4150/KPMI.2009.16.4.280

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Abstract PDF: The pressureless sintering behavior of Al_2O_3/Cu powder mixtures, prepared from Al_2O_3/CuO and Al_2O_3/Cu-nitrate, has been investigated. Microstructural observation revealed that Al_2O_3 powders with nano-sized Cu particles could be synthesized by hydrogen reduction method. The specimens, pressureless-sintered at 1400°C for 4 min using infrared heating furnace with the heating rate of 200°C/min, showed the relative density of above 90%. Maximum hardness of 16.1 GPa was obtained in Al_2O_3/MgO/Cu nanocomposites. The nanocomposites exhibited the enhanced fracture toughness of 4.3-5.7 MPacdotm1/2, compared with monolithic Al_2O_3. The mechanical properties were discussed in terms of microstructural characteristics.

Effect of Homogenization Treatment on Magnetic Properties of HDDR Treated Nd-Fe-Ga-Nb-B Alloy: J.H. Yu, S.H. Lee, D.H. Kim, D.W. Lee, B.K. Kim, M.H. Choi, Y.D. Kim; J Korean Powder Metall Inst. 2009;16(4):285-290.; DOI: https://doi.org/10.4150/KPMI.2009.16.4.285

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Abstract PDF: HDDR treated anisotropic Nd-Fe-B powders have been widely used, due to their excellent magnetic properties, especially for sheet motors and sunroof motors of hybrid and electric vehicles. Final microstructure and coercivity of such Nd-Fe-B powders depend on the state of starting mother alloys, so additional homogenization treatment is required for improving magnetic properties of them. In this study, a homogenization treatment was performed at 900sim1140°C in order to control the grain size and Nd-rich phase distribution, and at the same time to improve coercivity of the HDDR treated magnetic powders. FE-SEM was used for observing grain size of the HDDR treated powder and EPMA was employed to observe distribution of Nd-rich phase. Magnetic properties were analyzed with a vibrating sample magnetometer.

Electromagnetic Wave Absorption Properties of Fe₇₃Si₁₆B₇Nb₃Cu₁-Based Nanocrystalline Soft Magnetic Powder Composite Mixed with Charcoal Powder: Sun-I Kim, Mi-Rae Kim, Keun-Yong Sohn, Won-Wook Park; J Korean Powder Metall Inst. 2009;16(4):291-295.; DOI: https://doi.org/10.4150/KPMI.2009.16.4.291

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The electromagnetic wave absorption sheets were fabricated by mixing of Fe_73Si_16B_7Nb_3Cu_1 nanocrystalline soft magnetic powder, charcoal powder and polymer based binder. The complex permittivity, complex permeability, and scattering parameter have been measured using a network analyzer in the frequency range of 10 MHzsim10 GHz. The results showed that complex permittivity of sheets was largely dependent on the frequency and the amount of charcoal powder : The permittivity was improved up to 100 MHz, however the value was decreased above 1 GHz. The power loss of electromagnetic wave absorption data showed almost the same tendency as the results of complex permittivity. However, the complex permeability was not largely affected by the frequency, and the values were decreased with the addition of charcoal powder. Based on the results, it can be summarized that the addition of charcoal powder was very effective to improve the EM wave absorption in the frequency range of 10 MHzsim1 GHz.

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The Characteristic Changes of Electromagnetic Wave Absorption in Fe-based Nanocrystalline P/M Sheets Mixed with Ball-Milled Carbon Nanotubes
Sun-I Kim, Mi-Rae Kim, Keun-Yong Sohn, Won-Wook Park
Journal of Korean Powder Metallurgy Institute.2009; 16(6): 424. CrossRef

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