• Journal of the Korea Safety Management & Science
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• v.19 no.4
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• pp.317-322
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• 2017

When the heat flux on the heating surface following changing heat condition in the boiling heat transfer system exceeds critical heat flux, the critical heat flux phenomenon is going over to immediately the film boiling area and then it is occurred the physical destruction phenomenon of various heat transfer systems. In order to maximize the safe operation and performance of the heat transfer system, it is essential to improve the CHF(Critical Heat Flux) of the system. Therefore, we have analysis the effect of improving CHF and characteristics of heat transfer following the nanoparticle coating thickness. As the results, copper nanocoating time are increased to CHF, and in case of nano-coatings are increased spray-deposited coating times more than in the fure water; copper nanopowder is increased up to 6.40%. The boiling heat transfer coefficients of the pure water are increased up to 5.79% respectively. Also, the contact angle is decreased and surface roughness is increased when nano-coating time is increasingly going up.

• Journal of the Korean institute of surface engineering
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• v.41 no.1
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• pp.23-27
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• 2008

The effect of solution agitation on the copper electroless deposition process of ULSI (ultra large scale integration) interconnections was investigated by using physical, electrochemical and electrical techniques. It was found that proper solution agitation was effective to obtain superconformal copper configuration within the trenches of $130{\sim}80nm$ width. The transition of open potential during electroless deposition process showed that solution agitation induced compact structure of copper deposits by suppressing mass transfer of cuprous ions toward substrate. Also, the specific resistivity of copper layers was lowered by increasing agitation speed, which made the deposited copper particles smaller. Considering both copper deposit configuration and electric property, around 500 rpm of solution agitation was the most suitable for the homogeneous electroless copper filling within the ultra-fine patterns.

• Journal of Magnetics
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• v.10 no.2
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• pp.48-51
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• 2005

The spin transfer induced magnetization switching has been reported to occur in magnetic multilayer structures whose scope usually consists of one stack of ferromagnetic / non-ferromagnetic / ferromagnetic (F / N / F) materials. In this work, it is shown that: 1) Copper used as a buffer layer between the free Co and the Au cap-layer can clearly increase the probability to get the spin transfer induced magnetization switching in a simple spin valve Co 11 / Cu 6/ Co 2 (nm); 2) Furthermore, when Ruthenium is simultaneously applied as a buffer layer on the Si-substrate, the critical switching currents can be reduced by $30\%$, and the absolute resistance change delta R $[{\Delta}R]$ of that stack can be enlarged by $35\%$. The enhancement of the spin transfer induced magnetization switching can be ascribed to a lower local stress in the thin Co layer caused by a better lattice match between Co and Cu and the smoothening effect of Ru on the thick Co layer.

• Bulletin of the Korean Chemical Society
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• v.34 no.9
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• pp.2645-2649
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• 2013

We have developed a one-step synthesis of benzofurans from o-iodophenol and various terminal alkynes, by using Pd catalyst supported on nano-sized carbon balls (NCB) under copper- and ligand free conditions. This recyclable catalyst could be reused more than 5 times in the same heteroannulation reaction. The results have demonstrated that diverse 2-substituted benzofurans with tolerant functional groups can be prepared simply and conveniently under these conditions.

• International Journal of Internet, Broadcasting and Communication
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• v.7 no.2
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• pp.161-167
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• 2015

The performance of high power LEDs highly depends on the junction temperature. Operating at high junction temperature causes elevation of the overall thermal resistance which causes degradation of light intensity and lifetime. Thus, appropriate thermal management is critical for LED packaging. The main goal of this research is to improve thermal resistance by optimizing and comparing nano-pore silicon-based thermal substrate to insulated metal substrate and direct bonded copper thermal substrate. The thermal resistance of the packages are evaluated using computation fluid dynamic approach for 1 W single chip LED module.

• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.715-720
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• 2014

A Cu(II) complex with an three nitrogens and one sulfur coordination environment was synthesized and characterized. Its redox potential was observed at 0.483 V vs. NHE, very similar to that of a Cu-containing fungal enzyme, galactose oxidase, which catalyzes the oxidation of alcohols to corresponding aldehydes with the concomitant reduction of molecular oxygen to water. The Cu(II) complex selectively oxidizes the benzylic alcohols using TEMPO/$O_2$ under mild reaction conditions to corresponding aldehydes without forming any over-oxidation product. Moreover, the catalyst can be recovered and reused multiple times for further oxidation reactions, thus minimizing the waste generation.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.60-60
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• 2014

By the pre-doping technique on graphene/copper foil, we obtained the pristine sheet resistance and optical transmittance of the chlorine doped-single layer graphene $245{\Omega}/sq$ and 97% at 550 nm wavelength, respectively. X-ray photoelectron spectroscopy revealed that an extremely high Cl coverage of 47.3% of monolayer graphene surface was achieved as the highest surface-coverage graphene doping material ever reported.

• Journal of Powder Materials
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• v.21 no.3
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• pp.207-214
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• 2014

In this study, nano-scale copper powders were reduction treated in a hydrogen atmosphere at the relatively high temperature of $350^{\circ}C$ in order to eliminate surface oxide layers, which are the main obstacles for fabricating a nano/ultrafine grained bulk parts from the nano-scale powders. The changes in composition and microstructure before and after the hydrogen reduction treatment were evaluated by analyzing X-ray diffraction (XRD) line profile patterns using the convolutional multiple whole profile (CMWP) procedure. In order to confirm the result from the XRD line profile analysis, transmitted electron microscope observations were performed on the specimen of the hydrogen reduction treated powders fabricated using a focused ion beam process. A quasi-statically compacted specimen from the nano-scale powders was produced and Vickers micro-hardness was measured to verify the potential of the powders as the basis for a bulk nano/ultrafine grained material. Although the bonding between particles and the growth in size of the particles occurred, crystallites retained their nano-scale size evaluated using the XRD results. The hardness results demonstrate the usefulness of the powders for a nano/ultrafine grained material, once a good consolidation of powders is achieved.

• Journal of the Optical Society of Korea
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• v.20 no.5
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• pp.601-606
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• 2016

In this study, in order to analyze the low-temperature sintering process of silver and copper nanoparticles, we calculate their melting temperatures and surface melting temperatures with respect to particle size. For this calculation, we introduce the concept of mean-squared displacement of the atom proposed by Shi (1994). Using a parameter defined by the vibrational component of melting entropy, we readily obtained the surface and bulk melting temperatures of copper and silver nanoparticles. We also calculated the absorption cross-section of nanoparticles for variation in the wavelength of light. By using the calculated absorption cross-section of the nanoparticles at the melting temperature, we obtained the laser threshold energy for the sintering process with respect to particle size and wavelength of laser. We found that the absorption cross-section of silver nanoparticles has a resonant peak at a wavelength of close to 350 nm, yielding the lowest threshold energy. We calculated the intensity distribution around the nanoparticles using the finite-difference time-domain method and confirmed the resonant excitation of silver nanoparticles near the wavelength of the resonant peak.

• Journal of the Korean Electrochemical Society
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• v.7 no.4
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• pp.173-178
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• 2004

Silicon thin film were synthesized from silane and argon gas mixture directly on copper foil by rf PECVD and then lithium ion batteries were prepared from them employed as the negative electrodes without any further treatment. In the present study, two different kinds of silicon thin films, amorphous silicon and copper silicide were prepared by changing deposition temperature. Amorphous silicon film was prepared below $200^{\circ}C$, but copper silicide film with granular shape was formed by the reaction between silicon radical and diffused copper ions under elevating temperature above $400^{\circ}C$. The amorphous silicon film gives higher capacity than copper silicide, but the capacity decreases sharply with charge-discharge cycling. This is possibly due to severe volume changes. The cyclability is improved, however, by employing the copper silicide as a negative electrode. The copper silicide plays an important role as an active material of the electrode, which mitigates volume change cause by the existence of silicon and copper chemical bonding and provides low electrical resistance as well.