Journal of Powder Materials

Application of Carbon Nanotube Powders to Energy Storage: J Korean Powder Metall Inst. 2004;11(4):279-287.; DOI: https://doi.org/10.4150/KPMI.2004.11.4.279

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Fabrication and Permeability of Stainless Steel Filter by using Filler Metal: J Korean Powder Metall Inst. 2004;11(4):288-293.; DOI: https://doi.org/10.4150/KPMI.2004.11.4.288

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Abstract PDF: The application concept of using a fail safety filter on the filtering system is to prevent the particle leakage when the main filter element is broken at high temperature. In this study, the metal filters were fabricated by pressureless sintering method. The mixture of stainless steel powders and filler metal binder solved in the water solutions of 5% PVA was compacted to form the cylindrical filter without pressure. The compacted filter were sintered in the vacuum sintering furnace at 1200°C for 1 hour. The metal filter(produced with powder of 640-840 µm size) having more than above 50% porosity, 500µm pore size, and permeability of 7.3times10-11m2 plugged within 2.5 minute to prevent the leakage of maximum slip particle size of less than 3µm.

AlN preparation by Self-propagation High-temperature Synthesis (SHS) in Al-N₂ and Al-N₂-AIN system: J Korean Powder Metall Inst. 2004;11(4):294-300.; DOI: https://doi.org/10.4150/KPMI.2004.11.4.294

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Abstract PDF: This study for preparation of aluminum nitride (AlN) with high purity was carried out by self-propagating high-temperature synthesis method in two different systems, Al-N_2 and Al-N_2-AlN, with the change of nitrogen gas pressure and dilution factor. On the occasion of Al-N_2 system, unreacted aluminum was detected in the product in spite of high nitrogen pressure, 10 MPa, This may be caused by obstructing nitrogen gas flow to inner part of molten and agglomerate of aluminum, formed in pre-heating zone. In Al-N_2-AlN system, AlN with a purity of 95% or ever can be prepared in the condition of f_Dilgeq0.5, P_N_2geq 1 MPa, and the purity can be elevated to 98% over in the condition of f_Dil = 0.7 and P_N_2 = 10 MPa.

A Model on the Densification of Agglomerates of Powders: J Korean Powder Metall Inst. 2004;11(4):301-307.; DOI: https://doi.org/10.4150/KPMI.2004.11.4.301

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Successful implementation of the powder forming process requires a detailed understanding of several interacting phenomena. The aim is to better control the process variables and to optimize the design parameters. A number of studies were carried out using various constitutive models that take the density change during powder forming into account. Most of them were developed for powders and sintered porous metals, but few of them can describe powder agglomerates, whose behaviour is different from that of uniformly arranged powders. The modification is needed to account for the effect of agglomeration on densification behaviour. Incorporating powder agglomeration into a constitutive model is of considerable importance, as it provides a possibility of relating the powder densification response to microstructural characteristics of powder particles, especially in case of nano powders. In this paper, we proposed a new powder agglomerate model in order to describe the unique densification behaviour of nano powders. The proposed model was applied to the densification of powder agglomerates during cold isostatic pressing.

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Compressibility of hierarchic-architectured agglomerates of hydrogen-reduced copper nanopowders
Dong-Hyun Ahn, Wooyeol Kim, Eun Yoo Yoon, Hyoung Seop Kim
Journal of Materials Science.2016; 51(1): 82. CrossRef
Effect of Core-Shell Structure on Compaction Behavior of Harmonic Powder
Soo-Hyun Joo, Hyo Wook Park, Soo Young Kang, Eon Sik Lee, Hee-Soo Kang, Hyong Seop Kim
Journal of Korean Powder Metallurgy Institute.2015; 22(2): 105. CrossRef

Kinetic and Thermodynamic Features of Combustion of Superfine Aluminum Powders in Air: Young-Soon Kwon, Pyuck-Pa Park, Ji-Soon Kim, Alexander Gromov, Chang-Kyu Rhee; J Korean Powder Metall Inst. 2004;11(4):308-313.; DOI: https://doi.org/10.4150/KPMI.2004.11.4.308

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Abstract PDF: An experimental study on the combustion of superfine aluminum powders (average particle diameter, a_s: ∼0.1 µtextrmm) in air is reported. The formation of aluminum nitride during the combustion of aluminum in air and the influence of the combustion scenario on the structures and compositions of the final products are in the focus of this study. The experiments were conducted in an air (pressure: 1 atm). Superfine aluminum powders were produced by the wire electrical explosion method. Such superfine aluminum powder is stable in air but once ignited it can burn in a self-sustaining way due to its low bulk: density (∼0.1 g/㎤) and a low thermal conductivity. During combustion, the temperature and radiation were measured and the actual burning process was recorded by a video camera. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and chemical analysis were performed on the both initial powders and final products. It was found that the powders, ignited by local heating, burned in a two-stage self-propagating regime. The products of the first stage consisted of unreacted aluminum (-70 mass %) and amorphous oxides with traces of AlN. After the second stage the AlN content exceeded 50 mass % and the residual Al content decreased to ∼10 mass %. A qualitative discussion is given on the kinetic limitation for AlN oxidation due to rapid condensation and encapsulation of gaseous AlN.N.

Elastic Modulus Measurement of a Dry Process Fuel Pellet by Resonant Ultrasound Spectroscopy: J Korean Powder Metall Inst. 2004;11(4):314-321.; DOI: https://doi.org/10.4150/KPMI.2004.11.4.314

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The elastic moduli of simulated dry process fuels with varying composition and density were measured in order to analyze the mechanical properties of a dry process fuel pellet. Resonant ultrasound spectroscopy(RUS) which can determine all elastic moduli with one set of measurements for a rectangular parallelepiped sample was used to measure the elastic moduli of UO_2 and simulated dry process fuel. The simulated dry process fuel showed a higher value of Young's modulus than UO_2 due to the presence of metallic precipitates and solid solution elements in the UO_2 matrix. The correlation between Young's modulus and porosity(P) of simulated dry process fuel was found to be 231.4-651.8 P (GPa) at room temperature. Dry process fuel with a higher burnup showed higher Young's modulus because total content of fission product element was increased.

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Irradiation tests and post-irradiation examinations of DUPIC fuel
Chang Je Park, Kweon Ho Kang, Ho Jin Ryu, Cheol Yong Lee, In Ha Jung, Je Sun Moon, Joo Hwan Park, Sang Ho Na, Kee Chan Song
Annals of Nuclear Energy.2008; 35(10): 1805. CrossRef
Progress of the DUPIC Fuel Compatibility Analysis - IV: Fuel Performance
Hangbok Choi, Ho Jin Ryu, Gyuhong Roh, Chang Joon Jeong, Chang Je Park, Kee Chan Song, Jung Won Lee, Myung Seung Yang
Nuclear Technology.2007; 157(1): 1. CrossRef

Synthesis and kinetic of ultrafine titanium carbide particles by Mg-thermal reduction of liquid metal chlorides: J Korean Powder Metall Inst. 2004;11(4):322-327.; DOI: https://doi.org/10.4150/KPMI.2004.11.4.322

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Abstract PDF: Ultrafine titanium carbide particles were synthesized by the reaction of liquid-magnesium and vaporized TiCl_4+C_xCl_4(x = 1 and 2) solution. Fine titanium carbide particles with about 50 nm were successfully produced by combining Ti and C atoms released by chloride reduction of magnesium, and vacuum was then used to remove the residual phases of MgCl_2 and excess Mg. Small amounts of impurities such as O, Fe, Mg and Cl were detected in the product, but such problem can be solved by more precise process control. The lattice parameter of the product was 0.43267 nm, near the standard value. With respect to the reaction kinetics, the activation energy for the reactions of TiCl_4+C_2Cl_4and Mg was found to 69 kJ/mole, which was about half value against the use of TiCl_4+CCl_4, and such higher reactivity of the former contributed to increase the stoichiometry until the level of TiC_0.96 and decrease the free carbon content below 0.3 wt.%.

Effect of Chamber Pressure on the Microstructure of Fe Nano Powders Synthesized by Plasma Arc Discharge Process: J Korean Powder Metall Inst. 2004;11(4):328-332.; DOI: https://doi.org/10.4150/KPMI.2004.11.4.328

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Fe nanopowders were successfully synthesized by plasma arc discharge (PAD) process using Fe rod. The influence of chamber pressure on the microstructure was investigated by means of X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FE-SEM), Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). The prepared particles had nearly spherical shapes and consisted of metallic cores (a-Fe) and oxide shells (Fe_3O_4), The powder size increased with increasing chamber pressure due to the higher dissolution and ejection rate of H_2 and gas density in the molten metal.

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Characteristics and Sintering Behavior of Oxide Coated Iron Nanopowder Synthesized by Plasma Arc Discharge Process
Ji-Hun Yu, Cheol-Su Youn, Byoung-Kee Kim, Jai-Sung Lee, Chul-Jin Choi
MATERIALS TRANSACTIONS.2005; 46(6): 1436. CrossRef

Characteristics of Powder with Amount of Reductant Excess in Production of Tantalum Powder by MR-EMR Combination Process: J Korean Powder Metall Inst. 2004;11(4):333-340.; DOI: https://doi.org/10.4150/KPMI.2004.11.4.333

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Abstract PDF: In this study, tantalum powder has been producted by MR-EMR combination process. MR-EMR combination process is a method that is able to improve demerits of MR(metallothermic reduction) and EMR(electronically mediated reaction) process. This study examined the characteristics of powder with the amount of reductant excess using K_2TaF_7 as feed materials, Na as a reductant and KCl/KF as a diluent. In addition, this study examined acid treatment that affect the high purification of powder. The impurities contained in powder was removed in various conditions of acid treatment. The total charge passed through external circuit and average particle size(FSSS) were increased with increasing amount of sodium excess. The proportion of fine particle(-325mesh) was decreased with increasing amount of sodium excess. The yield was improved from 70％ to 76% with increasing amount of sodium excess. Considering the impurities, charge, morphology, particle size and yield, an amount of sodium excess of 10wt% were found to be optimum conditions for MR-EMR combination process.s.

Analysis of Densification Behavior of Nano Cu Powders during Cold Isostatic Pressing: J Korean Powder Metall Inst. 2004;11(4):341-347.; DOI: https://doi.org/10.4150/KPMI.2004.11.4.341

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Abstract PDF: In the study, a hybrid constitutive model for densification of metallic powders was applied to cold isostatic pressing. The model is based on a pressure-dependent plasticity model for porous materials combined with a dislocation density-based viscoplastic constitutive model considering microstructural features such as grain size and inter-particle spacing. Comparison of experiment and calculated results of microscale and nanoscale Cu powders was made. This theoretical approach is useful for powder densification analysis of various powder sizes, deformation routes and powder processing methods.

Fe계 나노결정 연자성코아의 개발동향: J Korean Powder Metall Inst. 2004;11(4):348-350.; DOI: https://doi.org/10.4150/KPMI.2004.11.4.348

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