Journal of Powder Materials

Synthesis of Nano-sized Tungsten Carbide Powders by Vapor Phase Reaction of Tungsten Ethoxide: J Korean Powder Metall Inst. 2003;10(1):1-5.; DOI: https://doi.org/10.4150/KPMI.2003.10.1.001

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Nano-sized WC powders were synthesized by vapor phase reaction using the precusor of tungsten ethoxide under helium and hydrogen atmosphere. The phases of the powder were varied with reaction Bone and gas flow rate. The powder size was about 30nm in diameter, and the tungsten carbide powder was coated by carbon layer. The synthesis of nano-sized WC powders was promoted as the hydrogen gas flow rate became higher. Inversely, tungsten oxide was formed by increasing the flow rate of helium gas. The synthesized powders were analyzed by XRD, FE-SEM, carbon analyzer etc.

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Synthesis of WC Nanosized Powder by the Plasma Arc Discharge Process
Seoung Soo Lee, Dong Won Joo, Yeon Gil Jung, Chul Jin Choi
Key Engineering Materials.2007; 336-338: 2086. CrossRef

Debinding Process Using Supercritical Fluids in Metal Powder Injection Molding: J Korean Powder Metall Inst. 2003;10(1):6-14.; DOI: https://doi.org/10.4150/KPMI.2003.10.1.006

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Abstract PDF: The purpose of the present study is to investigate the method decreasing debinding time as well as lowering operation condition than pure supercritical CO_2 debinding by using cosolvent or binary mixture of propane + CO_2. First method is to add cosolvent, such as n-hexane, DCM, methanol, 1-butanol, in supercritical CO_2. In case of adding cosolvent, we were found the addition of non-polar cosolvent (n-hexane) improves dramatically the binder removal rate (more than 2 times) compared with pure supercritical CO_2 debinding, second method is to use mixture of supercritical propane + CO_2, as solvent. In case of using mixture of supercritical propane + CO_2, the rate of debinding speeded up with increasing of pressure and concentration of propane at 348.15 K. It was found that addition of cosolvent (e.g., n-hexane, DCM) and binary mixture propane + CO_2 for supercritical solvent remarkably improved binder removal rate for the paraffin wax-based binder system, in comparison with using pure supercritical CO_2.

Microstructure of the Hybrid Al₂O₃-TiC/Al Composite by Rapid Solidification and Stone Mill Process.: J Korean Powder Metall Inst. 2003;10(1):15-20.; DOI: https://doi.org/10.4150/KPMI.2003.10.1.015

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Abstract PDF: Hybrid A1_2O_3-TiC ceramic particle reinforced 6061 and 5083 Al composite powders were prepared by the combination of twin rolling and stone mill crushing process, followed by consolidating processes of cold compaction, degassing and hot extrusion. The composite bar consists of lamellar structure of ceramic particle rich area and matrix area, in which the hybrid was decomposed into each TiC of about 3-4mutextrmm and AI_2O_3 particles of about 1-2mutextrmm in diameter. It also found that fine Mg_2Si precipitates of about 30 nm were embedded in the matrix, which have grains of about 3 mutextrmm. Higher UTS was measured at the 5083 composite bar compared to the conventionally fabricated composite, due to again refinement effect by the rapid solidification. No particle was shown to form in the interface between the matrix and reinforcement, whereas carbon was diffused into the matrix.

Electrochemical Properties of Tin-Encapsulated Graphite as Anode in Lithium-Ion Batteries: X. G.; J Korean Powder Metall Inst. 2003;10(1):21-25.; DOI: https://doi.org/10.4150/KPMI.2003.10.1.021

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Abstract PDF: The Sn - graphite composites were prepared by chemical encapsulation method for anode materials in Li-ion batteries. EDS and XRD analysis confirmed the presence of Sn in the graphite structure. Cyclic voltammometry (CV) measurement shows extra reduction and oxidation peaks, which might to be related to the formations of Li_xSn alloy compounds. Graphite-tin composite electrodes demonstrated higher Lithium storage capacities than graphite electrodes. Due to the nature of fine Sn particles on graphite surface, the graphite-tin composite electrodes have shown a good cycle properties.

Particle Refinement and Nano-structure Formation of Gas Atomized Al-14wt.%Ni-14 wt.%Mm Alloy Powder by Mechanical Milling: J Korean Powder Metall Inst. 2003;10(1):26-33.; DOI: https://doi.org/10.4150/KPMI.2003.10.1.026

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Abstract PDF: Al-l4wt.%Ni-l4wt.% Mm(Mm=misch metal) alloy powders rapidly solidified by the gas atomization method were subjected to mechanical milling(MM). The morphology, microstructure and hardness of the powders were investigated as a function of milling time using scanning electron microscopy(SEM), transmission electron microscopy(TEM) and Vickers microhardness tester. Microstructural evolution in gas-atomized Al-l4wt.%Ni-l4wt.% Mm(Mm=misch metal) alloy powders was studied during mechanical milling. It was noted that the as-solidified particle size of 200mutextrmm decreases during the first 48 hours and then increases up to 72 hours of milling due to cold bonding and subsequently there was continuous refinement to 20mutextrmm on milling to 200 hours. Two microstructurally different zones, Zone A, which is fine microstructure area and Zone B, which has the structure of the as-solidified powder, were observed. The average thickness of the Zone A layer increased from about 10 to 15mutextrmm in the powder milled for 24 hours. Increasing the milling time to 72 hours resulted in the formation of a thicker and more uniform Zone A layer, whose thickness increased to about 30~50mutextrmm. The TEM micrograph of ball milled powder for 200 hours shows formation of nano-particles, less than 20 nm in size, embedded in an Al matrix.

Pore Structure and Mechanic:11 Property of Porous TiNi Biomaterial Produced by Self-Propagating High-Temperature Synthesis: J Korean Powder Metall Inst. 2003;10(1):34-39.; DOI: https://doi.org/10.4150/KPMI.2003.10.1.034

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Abstract PDF: Porous TiNi bodies were produced by Self-propagating High-temperature Synthesis (SHS) method from a powder mixture of Ti and Ni. Porosity, pore size and structure, mechanical property, and transformation temperature of TiNi product were investigated. The average porosity and pore size of produced porous TiNi body are 63% and 216mutextrmm, respectively. XRD analysis showed that the major phase of produced TiNi body is B2 phase. Its average fracture strength and elastic modulus measured under dry condition were 22pm2 MPa and 0.18pm0.01GPa, respectively. It could be strained up to 7.3 %. The transformation temperatures determined by DSC showed the M_s temperature of 67°C and A_f temperature of 99°C.

Sintering Behavior of 2xxx Series Al alloys with Variation of Sintering Temperature: J Korean Powder Metall Inst. 2003;10(1):40-45.; DOI: https://doi.org/10.4150/KPMI.2003.10.1.040

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Sintering behavior of 2xxx series Al alloy was investigated to obtain full densification and sound microstructure. The commercial 2xxx series Al alloy powder. AMB2712, was used as a starting powder. The mixing powder was characterized by using particle size analyzer, SEM and XRD. The optimum compacting pressure was 200 MPa, which was the starting point of the "homogeneous deformation" stage. The powder compacts were sintered at 550~630°C after burn-off process at 400°C. Swelling phenomenon caused by transient liquid phase sintering was observed below 590°C of sintering temperature. At 610°C, sintering density was increased by effect of remained liquid phase. Further densification was not observed above 610°C. Therefore, it was determined that the optimum sintering temperature of AMB2712 powder was 610°C.C.

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Liquid phase sintering of the commercial 2xxx series Al blended powder
Kyung Ho Min, Shin Pil Kang, Baek-Hee Lee, Jeong-Keun Lee, Young Do Kim
Journal of Alloys and Compounds.2006; 419(1-2): 290. CrossRef

Mechanical Alloying Effect in Immiscible Cu₃₀Mo₇₀ Powders: J Korean Powder Metall Inst. 2003;10(1):46-50.; DOI: https://doi.org/10.4150/KPMI.2003.10.1.046

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Abstract PDF: Lee et al. reported that a mixture of Cu and Ta, the combination of which is characterized by a positive heat of mixing, DeltaH_mix of +2 kJ/㏖, can be amorphized by mechanical alloying(MA). It is our aim to investigate to what extent the MA is capable of producing a non-equilibrium phase with increasing the heat of mixing. The system chosen is the binary Cu_30Mo_70 with DeltaH_mix=+19 kJ/㏖. The mechanical alloying was carried out using a Fritsch P-5 planetary mill under Ar gas atmosphere. The vial and balls are made of Cu containing 1.8-2.0 wt.%Be to avoid contaminations arising mainly from Fe when steel balls and vial are used. The MA powders were characterized by the X-ray diffraction, EXAFS and thermal analysis. We conclude that two phase mixture of nanocrystalline fcc-Cu and bcc-Mo with grain size of 10 nm is formed by the ball-milling for a 3:7 mixture of pure Cu and Mo, the evidence for which has been deduced from the thermodynamic and structural analysis based on the DSC, X-ray diffraction and EXAFS spectra.

Effect of the Process Parameters on the Fe Nano Powder Formation in the Plasma Arc Discharge Process: J Korean Powder Metall Inst. 2003;10(1):51-56.; DOI: https://doi.org/10.4150/KPMI.2003.10.1.051

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To investigate the effect of the parameters of the plasma arc discharge process on the particle formation and particle characteristics of the iron nano powder, the chamber pressure, input current and the hydrogen volume fraction in the powder synthesis atmosphere were changed. The particle size and phase structure of the synthesized iron powder were studied using the FE-SEM, FE-TEM and XRD. The synthesized iron powder particle had a core-shell structure composed of the crystalline alpha-Fe in the core and the crystalline Fe_3O_4 in the shell. The powder generation rate and particle size mainly depended on the hydrogen volume fraction in the powder synthesis atmosphere. The particle size increased simultaneously with increasing the hydrogen volume fraction from 10% to 50%, and it ranged from about 45nm to 130 nm.

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Effect of Chamber Pressure on the Microstructure of Fe Nano Powders Synthesized by Plasma Arc Discharge Process

Journal of Korean Powder Metallurgy Institute.2004; 11(4): 328. CrossRef

Effect Of Bedding on the Microstructure of Si₃N₄ with Ultrafine SiC: J Korean Powder Metall Inst. 2003;10(1):57-62.; DOI: https://doi.org/10.4150/KPMI.2003.10.1.057

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Abstract PDF: The effect of bedding on the microstructure of Si_3N_4 added with ultra-fine SiC was investigated. The bedding and the addition of ultra-fine SiC effectively inhibited grain growth of Si_3N_4 matrix grain. The microstructures of the specimens sintered with bedding powder consisted of fine-grains as compared with the specimens sintered without bedding powder. In addition, the grain size and the difference of grain size between the specimens sintered with bedding and without bedding was reduced with increasing SiC content. Some ultra-fine SiC particles were trapped in the Si_3N_4 grains growed. The number of SiC particles trapped in the Si_3N_4 grains increased with increasing the grain growth. When ultra-fine SiC particles were added in the Si_3N_4 ceramics, the strength was improved but the toughness was decreased, which was considered to be resulted from the decrease of the grain size.

최근 금속나노분말의 응용: J Korean Powder Metall Inst. 2003;10(1):63-66.; DOI: https://doi.org/10.4150/KPMI.2003.10.1.063

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NANO기술을 이용한 환경신소재 전문기업: J Korean Powder Metall Inst. 2003;10(1):67-69.; DOI: https://doi.org/10.4150/KPMI.2003.10.1.067

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