• Journal of the Korean Ceramic Society
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• v.49 no.5
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• pp.417-422
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• 2012

Copper nano particles have been considered as the materials for conductive ink due to its good thermal, electrical conductivity and low cost. However, copper nanoparticles oxidize easily, decreasing dispersion stability and electrical conductivity. Therefore, it is important to develop a method to minimize oxidation of copper nano particles to improve its dispersion stability property in copper nano ink. In this study, copper nano particles were coated with 1-Octanethiol VSAM(Vaporized Self Assembled Multilayers) to prevent oxidation and coated copper powders were dispersed in conductive ink successfully by studying its relationship of different chain length of solvents to 1-Octanethiol coating layer to fabricate nano ink. Various alcohol solvents, such as 1-Hexanol, 1-Octanol, and 1-Decanol were used. The coating layer was observed using FESEM and TEM. Furthermore, dispersion of copper nano particles in nano inks, was characterized using Turbiscan analyzer, viscometer, and contact angle measurement tool.

• Journal of Welding and Joining
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• v.15 no.4
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• pp.109-115
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• 1997

Laser cladding is a technique for modification of metal surface. In this laser cladding experiment a metal powder feeding system was developed for more efficient laser cladding. This system can reduce processing time and be used simpler than the conventional method. The feeding of metal powder has given a rise to the process for sequential buildup of bulk rapidly solidified materials in the form of fine powder stream to the laser cladding process. The parameters of laser cladding have been investigated using this experimental equipment. Bronze on aluminum alloy and copper on aluminum alloy were experimented by using defocused beam, powder feeding system, and gas shielding. Good cladding was achieved in the range of beam travel speed of 2.25m/min. In the case of copper/aluminum and bronze/aluminum substrate, the absorption of laser beam was too high to produce low diluted clad. In the case of copper/1050 aluminum, the optimal laser cladding condition was of laser power of 2.8kW, powder feed rate of 0.31g/s and beam travel speed of 2.25m/min. In the case of bronze/aluminum the optimal condition is of laser power of 2.5kW, powder feed rate of 0.31g/s, and beam travel speed of 2.36m/min.

• Journal of Hydrogen and New Energy
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• v.28 no.1
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• pp.70-76
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• 2017

To synthesize copper nanoparticle a thermal decomposition was adopted. And to solve the problem of surface oxidation of the synthesized copper powder an electroless Ag plating method was used. The size and shape of synthesized Cu nanoparticle were affected by the size of copper oxalate used as a precursor, reaction solvent, reaction temperature and amount of reducing agent. Especially reaction solvent is dominant factor to control shape of Cu nano-particle which can have the shapes of sphere, polygon and rod. In case of glycerol, it produced spherical shape of about 500 nm in size. Poly ethylene produced uniform polygonal shape in about 700 nm and ethylene glycol produced both of polygon and rod having size range between 500 and 1500 nm. The silver coated copper powder showed a high electrical conductivity.

• Korean Journal of Materials Research
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• v.16 no.5
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• pp.285-291
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• 2006

Copper powders have been widely used in electrically conductive coatings, electrode materials et al. and are very prospective since they are cheaper than noble metal powders such as silver or palladium. In this study, copper powders for metal filler of EMI shielding have been prepared using a solvothermal process from $CuSO_4$, NaOH, Glucose, mixed solvent ($H_2O$: Ethanol) and hydrazine which was used as a reducing agent at various reaction conditions. The prepared copper powders showed finely dispersed spherical shape without agglomerate, uniform morphology, narrow size distribution, high purity and were about 400-700 nm in size. The prepared powders were characterized using XRD, SEM, TGA, XPS, particle size measurement and EMI shielding efficiency.

• Journal of the Korean Society for Nondestructive Testing
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• v.16 no.4
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• pp.241-250
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• 1997

The velocity dispersion of surface acoustical wave(SAW) of Si layer/mesh Au/Si substrate was measured by the frequency analysis technique of backward radiation at liquid/solid interface. The difference of backward radiation patterns depending on used transducers (2, 5, 10MHz) confirmed that the backward radiation phenomenon was caused by the energy radiation from SAW generated in surface region. An ultrasonic goniometer was constructed to measure continuously the angular dependence of backscattered intensity. The angular dependences of backward radiation(5MHz) were measured for Ni layer/Al substrate specimens that were bonded by epoxy involving different content of Cu powder. It was known that the width and pattern of backward radiation had informations such as the velocity dispersion, bonding quality and structure of surface region.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.7
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• pp.647-653
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• 2013

The evaporation characteristics of nanofluid droplets on a heated solid surface were experimentally investigated. The experiments were conducted using pure water and a nanofluid of water mixed with CuO nanoparticles, and the solid surface was made of a copper block heated by a nine cartridge heater. The experimental results showed that the evaporation rate of the nanofluid droplet was higher than that of the pure water droplet on the heated solid surface because nanoparticles increased the thermal conductivity of the nanofluid. Furthermore, it was found that the evaporation rate of the nanofluid droplet increased with the solid surface roughness. This may be because the actual area of the liquid-solid interface increased with the solid surface roughness.

• Journal of Surface Science and Engineering
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• v.49 no.5
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• pp.416-422
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• 2016

We have investigated the effects of applied potential, deposition time and electrolyte types on shapes and physical properties of Cu dendrites by potentiostatic electrodeposition. Finer shape of dendrites was observed at less cathodic potential by 100mV than at the limiting current, due to 'effective overpotential'. The shape of copper dendrite is related to the deposition time, too. The dendrite depositing for 10 min showed the finest shape. The finer dendrite has the less apparent density and the larger specific surface area. Dendrite from chloride solution has the lowest density and the largest surface area among three plating solutions, sulfate, chloride and pyrophosphate.

• Journal of the Korean Magnetics Society
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• v.5 no.3
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• pp.171-174
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• 1995

We have studied the paramagnetic $CuF_{2}$ using the techniques of pulsed nuclear magnetic resonance(NMR). The powder sample revealed two well-separated lines from the distinct $^{19}F$ sites at room temperature and at 77 K. The distinct frequency shifts of the two lines appear to arise from electron transfers. Furthermore, the two sites have very short spin-lattice relaxation times ($T_{1}$). The frequency-shifted site has the shorter $T_{1}$ than the unshifted one, reflecting the difference of the electron environments of the two sites.

• Transactions of Materials Processing
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• v.31 no.4
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• pp.240-245
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• 2022

In this study, to achieve good electrical conductivity of a charging terminal component in electric vehicles, we investigated the microstructure evolution of pure-Cu subjected to metal injection molding by controlling the sintering variables, such as temperature and time. Thus, three samples were sintered at temperatures ranging from 1000 ℃ to 1050 ℃ near to the melting temperature of 1085 ℃ for 1 and 10 h after thermal evaporation of binder at 730 ℃. Both procedures were made using a unified furnace under Ar+H₂ gas with high purity. The structural observation displayed that the grain size as well as the compactness (a reciprocal of porosity) increased simultaneously as temperature and time increased. This gave rise to high thermal conductivity of 90% IACS together with high density, which was mainly attributed to decrease in fractions of grain boundaries and micro-pores working as effective scattering center for electron movement.

• Journal of Conservation Science
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• v.31 no.3
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• pp.309-318
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• 2015

The staff given with chair to Yi Gyeong-seok, senior official over 70 years old by King Hyeonjong of Joseon Dynasty is representative handcraft of Joseon Dynasty. Results of analysis on the metallic decoration show that the metallic ornament of the end part which is connected to the spade was made by rolling of iron plate and brass plating. The plated part is limited to the ornament of the end part connected to the spade and the plating was not applied to the spade. Brass including 20% zinc was used for the connecting part of guard while brass gilded iron was used for the spade. This suggests that the tone of the connecting part of the guard and the spade was not different for reason of visual harmonization. Potential applied plating method can be amalgam, dippping in molten brass, and brushing but the analysis result suggests that dipping in molten brass method is the most likely accepted method. The brass guard of knife was joined by tin-lead solder. Rivet used to fix the blade was made by pure iron as an optimum material which satisfies flexibility and strength.