• Journal of Powder Materials
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• v.1 no.2
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• pp.181-189
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• 1994

The compacts of pure and phosphorus-coated iron powder with 0~0.8%C were sintered at $1100^{\circ}C$ for 40 min. in cracked ammonia gas atmosphere. The tensile and impact strengths were measured and the relationship of the results with carbon content, phosphorus, quenching and tempering was investigated. The results obtained can be summarized as follows : (1) The tensile strength of sintered compacts increased slowly with carbon content. Increase in tensile strength by heat treatment was evident especially in the low carbon specimen. The specimen with phosphorus showed higher strength compared to pure iron compacts value. (2) No inflection point of elasticplastic deformation on stress-strain curve was observed in sintered steel. The elastic modulus of sintered steel had the same tendency as tensile strength. But the elongation showed the opposite tendency. (3) The impact absorption energy of sintered steel without addition of phosphorus decreased successively with carbon content and by quenching and tempering. On the contrary, addition of phosphorus resulted in an increase of the impact absorption energy. Quenching and tempering did not affect the impact energy especially in high carbon content. (4) The main fracture source was pore in specimen and the propagation of crack occured mostly along the grain boundaries. But the intragranular fracture was also observed in high carbon, quenched and tempered specimen, and especially in the specimen with phosphorus.

• Journal of Powder Materials
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• v.23 no.4
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• pp.317-324
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• 2016

Tin is one of the most promising anode materials for next-generation lithium-ion batteries with a high energy density. However, the commercialization of tin-based anodes is still hindered due to the large volume change (over 260%) upon lithiation/delithiation cycling. To solve the problem, many efforts have been focused on enhancing structural stability of tin particles in electrodes. In this work, we synthesize tin nano-powders with an amorphous carbon layer on the surface and surroundings of the powder by electrical wire explosion in alcohol-based liquid media at room temperature. The morphology and microstructures of the powders are characterized by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. The electrochemical properties of the powder for use as an anode material for lithium-ion battery are evaluated by cyclic voltammetry and a galvanometric discharge-charge method. It is shown that the carbon-coated tin nano-powders prepared in hexanol media exhibit a high initial charge specific capacity of 902 mAh/g and a high capacity retention of 89% after 50 cycles.

• Progress in Superconductivity and Cryogenics
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• v.4 no.2
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• pp.16-20
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• 2002

Bi-axially textured Ni tapes for YBCO coated conductors were Prepared by cold rolling and heat treatment of Ni Powder compacts. The Ni powder used in this study was 5 urn in particle size and 99.99 % in purity. The process of this study consists of filling of hi powder into a rubber mold, cold-isostatically Pressing and sintering of the powder compacts at 110$0^{\circ}C$ for 6h in 96 % Ar - 4 % H$_2$ atmosphere. The sintered compacts were cold rolled with a 5 % step reduction ratio into a 100 micron-thick tapes and then heat-treated at 100$0^{\circ}C$ for various time periods. The (200) texture of Ni tape was successfully developed through the recrystallization heat treatment of the cold rolled Ni tapes. At 100$0^{\circ}C$, the degree of texture of the heat-treated Ni tapes seems not to be significantly affected by the heat-treatment time. The short heat treatment of S min was sufficient to develop the complete (200) cube texture. The degree of in-Plane and out-of-plane texture of the prepared Ni tapes was 8-10$^{\circ}$. The heat treated Ni tapes consisted of equiaxed grains with a size 50-70 microns. and the AFM sol-face roughness was as smooth as 3 nm.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1076-1077
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• 2006

Conductive pastes consist of conductive fillers( Au, Ag, Ni, Cu etc.), organic binders, solvents and additives. Meanwhile, there are some metal powders such as copper, nickel etc that are used for pastes which have serious surface corrosion problems. This problem leads to change of the color and decrease in conductivity and affect storage stability of conductive pastes. By using silane coupling agent and dispersion agent, we can ensure both the corrosion stability and long term storage stability, and enhance the high performance electrical and mechanical properties of EMI shielding silicone sealant.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.429-430
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• 2002

In this study, three kinds of brake: discs including two coated brake discs and one steel disc were tested under the same experimental conditions on a reduced scale braking test bench. Plasma spray coating technique was used to coat ceramic powder on the discs. In the test, four commercial sintered brake pads were coupled with discs. Ceramic coated discs have shown good stability in friction coefficient at high speed and high energy braking conditions. However, ceramic coated discs caused more wear loss of pad mass than the steel disc. It was shown that thermal barrier effect in ceramic coated discs adjusted the thermal partition between pad and disc. Steel disc showed fluctuating friction coefficient at high speed but less wear loss of pad mass than ceramic coated discs.

• 한국초전도학회:학술대회논문집
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• v.13
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• pp.88-88
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• 2003

• Proceedings of the Korean Ceranic Society Conference
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• 2003.04a
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• pp.125.2-125
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• 2003

• Journal of Powder Materials
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• v.21 no.6
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• pp.434-440
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• 2014

Silicon carbide(SiC) layer is particularly important tri-isotropic (TRISO) coating layers because it acts as a miniature pressure vessel and a diffusion barrier to gaseous and metallic fission products in the TRISO coated particle. The high temperature deposition of SiC layer normally performed at $1500-1650^{\circ}C$ has a negative effect on the property of IPyC layer by increasing its anisotropy. To investigate the feasibility of lower temperature SiC deposition, the influence of deposition temperature on the property of SiC layer are examined in this study. While the SiC layer coated at $1500^{\circ}C$ obtains nearly stoichiometric composition, the composition of the SiC layer coated at $1300-1400^{\circ}C$ shows discrepancy from stoichiometric ratio(1:1). $3-7{\mu}m$ grain size of SiC layer coated at $1500^{\circ}C$ is decreased to sub-micrometer (< $1{\mu}m$) $-2{\mu}m$ grain size when coated at $1400^{\circ}C$, and further decreased to nano grain size when coated at $1300-1350^{\circ}C$. Moreover, the high density of SiC layer (${\geq}3.19g/cm^3$) which is easily obtained at $1500^{\circ}C$ coating is difficult to achieve at lower temperature owing to nano size pores. the density is remarkably decreased with decreasing SiC deposition temperature.

• Journal of Powder Materials
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• v.21 no.1
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• pp.21-27
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• 2014

In this study, diatomite based materials were investigated as a support filter for silica particle coating. The silica sol for coating was synthesized by a st$\ddot{o}$ber process. The diatomite support was dry-pressed at 10 MPa and sintered at $1200^{\circ}C$ for 1 hour. The coating sol was prepared as a mixture of EtOH and silica sol. The diatomite support was coated by a dip-coating process. Silica coated diatomite filter was sintered at $1000{\sim}1200^{\circ}C$ for 1 hour. The largest pore size was decreased with increasing concentration ratio of coating sol. The gas and water permeability of silica coated diatomite decreased with increasing of concentration ratio of the coating sol.

• Bulletin of the Korean Chemical Society
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• v.30 no.7
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• pp.1607-1610
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• 2009

The carbon-coated Si/Cu powder has been prepared by mechanical ball milling and hydrocarbon gas decomposition methods. The phase of Si/Cu powder was analyzed using X-ray diffraction (XRD), dispersive Raman spectroscopy, electron probe microanalysis (EPMA) and transmission electron microscope (TEM). The carbon-coated Si/Cu powders were used as anode active material for lithium-ion batteries. Their electrochemical properties were investigated by charge/discharge test using commercial LiCo$O_2$ cathode and lithium foil electrode, respectively. The surface phase of Si/Cu powders consisted of carbon phase like the carbon nanotubes (CNTs) with a spacing layer of 0.35 nm. The carbon-coated Si/Cu/graphite composite anode exhibited a higher capacity than commercial graphite anode. However, the cyclic efficiency and the capacity retention of the composite anode were lower compared with graphite anode as cycling proceeds. This effect may be attributed to some mass limitations in LiCo$O_2$ cathode materials during the cycling.