• Korean Journal of Optics and Photonics
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• v.17 no.1
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• pp.104-109
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• 2006

Cu-doped $TiO_2$ thin films were prepared by RF magnetron co-sputtering, and their structural, optical and photodegradation. properties were examined as a function of calcination temperature. XRD results showed that the crystallite size of Cu/$TiO_2$ thin films was bigger than that of the pure $TiO_2$ thin films. SEM results revealed that the agglomerated particle size of the Cu/$TiO_2$ films was more uniform and smaller than that of pure $TiO_2$ films. The absorption edge of thin films calcined at $900^{\circ}C$ was red shifted, resulting from the phase transformation from anatase to rutile phase, and the transmittance of the thin film rapidly decreased due to an increase in particle size. The photodegradation properties of the Cu/$TiO_2$ thin films were superior to those of the pure $TiO_2$ thin films.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.439-440
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• 2008

• Proceedings of the Materials Research Society of Korea Conference
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• 2005.05a
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• pp.295-295
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• 2005

• Proceedings of the Korean Ceranic Society Conference
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• 2003.10a
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• pp.176.2-176
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• 2003

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1997.04a
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• pp.8-8
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• 1997

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.6
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• pp.559-566
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• 2013

The effects of solid surface roughness on the contact angle of a nanofluid droplet were experimentally investigated. The experiments were conducted using the solid surface of a 10 mm cubic copper block and the nanofluid of water mixed with CuO nanoparticles. The experimental results showed that the contact angles of nanofluid droplets were lower than those of water droplets and that the contact angle of the nanofluid droplet increased with the solid surface roughness. Furthermore, it was found that the contact angles of water droplets on the solid surface quenched by both water and the nanofluid were lower than those of water droplets on the pure solid surface. However, significant differences were not observed between the contact angles on the solid surfaces quenched by water and the nanofluid.

• Journal of Power System Engineering
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• v.14 no.4
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• pp.50-55
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• 2010

In order to investigate tribological effects of nano copper particles impregnated(CuN) on surface polytetrafluoroethylene(PTFE) on sealing wear and an experimental study was carried out to determine the wear behavior of copper nano-particles impregnation two kind thickness in super critical $CO_2$ liquid. Experimental results showed that the friction coefficients of CuN PTFE at the low sliding speed(0.44m/s) and the oil temperature ($60^{\circ}C$) were higher than that of virgin PTFE. And a thin nano copper particles impreganated thickness was formed on the surface in the PTFE and the specimen with this treatment has much better friction properties than the original one. Fortunately, at the high load(80 N) and the oil temperature, the friction coefficient of CuN PTFE was lower than that of virgin PTFE. This evidenced the load carrying capacity of CuN PTFE was much better than that of virgin PTFE under the high load condition(80 N) specially. Therefore, it can be concluded that the friction coefficient variation of CuN PTFE is very small but its wear rate decreases greatly with increase in sliding speed.

• Solar Energy
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• v.14 no.2
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• pp.91-101
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• 1994

Heat release characteristics of a CaO packed bed reactor which is used for a chemical heat storage device has been studied. We employed Cu-plate fins to release the heat of reaction of the CaO packed bed inside the reactor fast and effectively. Two-dimensional analysis of unsteady state heat flow inside the bed was performed as a function of time and under various conditions of the Cu-plates. It is noted that the time required to release the heat of reaction with Cu fins is reduced more than twice fast compared to that without Cu fins. That was largely dependent upon the number of Cu-plate, as well.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.3
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• pp.51-56
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• 2016

To fabricate a copper (Cu)-based fine conductive filler having antioxidation property, submicron silver (Ag)-coated Cu particles were fabricated and their antioxidation property was evaluated. After synthesizing the Cu particles of $0.705{\mu}m$ in average diameter by a wet-reduction process, Ag-coated Cu particles were fabricated by successive Ag plating using ethylene grycol solvent. Main process parameters in the Ag plating were the concentration of reductant (ascorbic acid), the injection rate of Ag precursor solution, and the stirring rate in mixed solution. Thus, Ag plating characteristics and the formation of separate fine pure Ag phase were observed with different combinations of process parameters. As a result, formation of the separate pure Ag phase and aggregation between Ag-coated Cu particles could be suppressed by optimization of the process parameters. The Ag-coated Cu particles which were fabricated using optimal conditions showed slight aggregation, but excellent antioxidation property. For example, the particles indicated the weight gain not exceeding 0.1% until $225^{\circ}C$ when they were heated in air at the rate of $10^{\circ}C/min$ and no weight gain until 75 min when they were heated in air at $150^{\circ}C$.

• Journal of Adhesion and Interface
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• v.20 no.1
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• pp.23-28
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• 2019

In this study, the micro- and nano-particles were used and their shapes were transferred into the polydimethylsiloxane (PDMS) film to fabricate the dry adhesives and their properties were investigated. The Cu nanoparticles of the sizes of 20 nm, 40 nm and 70 nm and the polymethylmethacrylate (PMMA) beads of the size of $5{\mu}m$ were used to transfer their images and the resultant properties of the dry adhesives were compared. The effects of particle size and materials on the mechanical property, tensile adhesion strength, light transmittance, surface morphology, water contact angle were studied. The dry adhesives obtained from the transfer process of Cu nanoparticles with the size of 20 nm resulted in the enhancement of tensile adhesion strength more than 300% compared to that of the bare PDMS. The formation of nanostructure of large surface area on the surface of the PDMS film by the Cu nanoparticles may responsible for the improvement. This study suggests that the use of nanoparticles during the fabrication of PDMS dry adhesives is easy and effective and could be applied to the fabrication of the medical patch.