• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.377-378
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• 2006

Thermal management technology is a critical element in all new chip generations, caused by a power multiplication combined with a size reduction. A heat sink, mounted on a base plate, requires the use of special materials possessing both high thermal conductivity (TC) and a coefficient of thermal expansion (CTE) that matches semiconductor materials as well as certain packaging ceramics. In this study, nano tungsten coated copper powder has been developed with a wide range of compositions, 90W-10Cu to 10W-90Cu. Powder technologies were used to make samples to evaluate density, TC, and CTE. Measured TC lies among theoretical values predicted by several existing models.

• Journal of Welding and Joining
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• v.31 no.3
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• pp.49-53
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• 2013

Recently, studies about application of magnesium alloy sheet to automotive bodies are on the increase. For application to automotive bodies, researches about characteristics of resistance spot welding of magnesium alloy sheet are essential. Electrode life of resistance spot welding of magnesium alloy is very short due to sticking of magnesium alloy to copper alloy electrode. To increase electrode life, most effective method is inserting cover plate between electrode and magnesium sheet. But application of cover plate to actual process is difficult and decreases welding productivity. Process tape supplied automatically as cover plate can minimize lose of productivity and increase welding quality. In this study, resistance spot welding of magnesium alloy is carried out with applying process tape. Acceptable welding current region according to electrode force and welding time is determined.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.7
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• pp.701-708
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• 2011

Natural convection heat transfers on inclined flat plates were measured for Grashof numbers of $8.06{\times}10^7$ and $3.45{\times}10^9$ by using a copper sulfate electroplating system. The inclinations of the plates were varied from upward-facing horizontal to downward-facing horizontal. Test results for the downward-facing plate agree well with the existing theory that the Nusselt number can be calculated by replacing gravitational acceleration, g with g $cos{\theta}$ in the heat transfer correlation for the vertical plate. The natural convection flows for the upward-facing plate follow two distinct flow regimes: boundary layer regime and flow separation regime. The copper plating pattern for the upward-facing plates clearly reveals the flow separation points.

• Korean Journal of Materials Research
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• v.25 no.4
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• pp.202-208
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• 2015

Alumina dispersion strengthening copper(ADSC) alloy has great potential for use in many industrial applications such as contact supports, frictional break parts, electrode materials for lead wires, and spot welding with relatively high strength and good conductivity. In this study, we investigated the oxidation behavior of ADSC alloys. These alloys were fabricated in forms of plate and round type samples by surface oxidation reaction using Cu-0.8Al, Cu-0.4Al-0.4Ti, and Cu-0.6Al-0.4Ti(wt%) alloys. The alloys were oxidized at $980^{\circ}C$ for 1 h, 2 h, and 4 h in ambient atmosphere. The microstructure was observed with an optical microscope(OM) and a scanning electron microscope(SEM) equipped with energy-dispersive X-ray spectroscopy(EDS). Characterization of alumina was carried out using a 200 kV field-emission transmission electron microscope(TEM). As a result, various oxides including Ti were formed in the oxidation layer, in addition to ${\gamma}$-alumina. The thickness of the oxidation layer increased with Ti addition to the Cu-Al alloy and with the oxidation time. The corrected diffusion equation for the plate and round type samples showed different oxidation layer thickness under the same conditions. Diffusion length of the round type specimen had a value higher than that of its plate counterpart because the oxygen concentration per unit area of the round type specimen was higher than that of the plate type specimen at the same diffusion depth.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.3
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• pp.506-511
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• 2006

Silver is one of the most appropriate Jewelry materials for Jewelry casting and bench working. The technique known as 'Mokumegane' is good for making silver jewelry with natural patterns, such as wood grain patterns, but the process is not easy for silversmithing because it requires complicated and heavy labour. Instead of using conventional Mokumegane technique, we propose a new modified silver-copper casting process that enables a similar surface effect with good metal bonding strength between silver and copper. Simply pouring the molten silver into pre-aligned copper granules or 0.5 mm to 1.5 mm-thick copper sheets leads to well embedded copper silver ingots. The rolled silver plates from those ingots show excellent bonding interface even after the silver plate rolled ten times. We successfully fabricated prototype rings with copper embedded silver plates. Our result implies that our newly proposed process nay be a simpler way to fabricate silver jewelry with a pseudo-Mokumegane effect.

• Korean Journal of Materials Research
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• v.11 no.10
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• pp.820-832
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• 2001

In order to obtain the basic data on the optimum conditions of electroforming process for fabricating the micro wiring pattern for plate type micro- motor core, characteristics of plating bath and properties of deposits were studied with various copper plating baths which contain sulfate, fluoborate, pyrophosphate and cyanide salt, respectively. Cathodic polarization, throwing power, internal stress, texture and surface morphology of deposits were observed. Throwing power of plating solution is deeply related to the polarization curves and the values are in the range of +20∼20%. The order of values ate as follows- pyrophosphate, cyanide, sulfate and fluoborate bath. Internal stresses of deposits are tensile in all of the copper plating bath. Thickness of the deposits plated at the center of holes has the highest value in the pyrophosphate bath and K factor, ratio of height and width of deposit, is 1.44. It was confirmed that the pyrophosphate bath was the best one for the electroforming of wire pattern.

• Journal of Conservation Science
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• v.31 no.3
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• pp.193-214
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• 2015

The green pigments of shamanic paintings (83 items) in the 19~20th century were analyzed with X-ray fluorescent spectrometer(XRF), scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (ATR-FTIR). In 60 items, copper and arsenic were detected in green pigments of the paintings by XRF spectra. Cu $K{\alpha}$/As $K{\beta}$ (peak intensity ratio of copper and arsenic) of shamanic paintings of Bokgaedang (shrine), solemn paintings (romance of three kingdoms) of Donggwanwangmyo and unknown enshrined place were 5.93~12.04 and higher compared to 5.67-6.26 of standard emerald greens and 4.01~7.89 of remaining shamanic paintings. The SEM images of crystal forms of copper-arsenic green pigments were various. Crystal forms were divided into oval and round spherulite with intersecting plate crystals and spherulite with agglomerate plate crystals. The crystals of the latter were found in shamanic paintings of Bokgaedang (shrine), solemn paintings (romance of three kingdoms) of Donggwanwangmyo and unknown enshrined place and the former were found in the rest of shamanic paintings. Copper-arsenic green pigments of shamanic paintings were identified as Scheele's green from shamanic paintings of Bokgaedang (shrine) and romance of three kingdoms. Emerald green from the rest of shamanic paintings by ATR-FTIR. From analytical results, it is confirmed that Scheele's green of shamanic paintings of Bokgaedang and romance of three kingdoms was used in the 1850s~1870s and emerald green had been widely used from late 19th century to 1970 in the rest of shamanic paintings.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.1
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• pp.1-7
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• 2017

As a part of studies to lower the infrared (IR) emissivity from the surface of exhaust nozzle in the turbo jet engine, stainless steel plate was coated with copper particle/meta-aramid resin composites and the IR emissivity of the plate were investigated. Binders of filler particles based on synthetic polymers generally undergo thermal decomposition before $300^{\circ}C$. It was found that the meta aramid resin was thermally stable after the test at $320^{\circ}C$, confirming the excellent thermal stability. Contents of copper particles in the composites were varied from 0 to 70% by volume. It was observed that the copper particle/meta aramid resin composites showed good adhesion after the tests at $320^{\circ}C$. The specimen coated with the composite containing 50 vol% of copper particles showed the lowest IR emissivity, 0.6, at $320^{\circ}C$.

• Journal of Environmental Health Sciences
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• v.27 no.3
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• pp.99-106
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• 2001

A laboratory experiment was performed to investigate phosphorus and nitrogen removal from synthetic wastewater by intermittently activated sludge process packed with aluminium plate. Three continuous experimental systems, I. e. an intermittently activated sludge process(Run A), an intermittently activated sludge process with an aluminium plate packed into the reactor(Run B), and a reactor post stage(Run C) were compared. In the batch experiments, the phosphorus removal time in the reactor packed with copper and aluminium plate simultaneously was faster than that of the reactor packed with only an aluminium plates. However, the reactor packed with only an aluminium plate could be used for phosphorus removal. Move phosphorus was removed with an increase of surface area of aluminium plate and electrolysis(NaCl) concentration. The efficiency of COD and nitrogen removal was not affected in Run B. However, the phosphrus removal efficiency decreased because of reaction products and activated sludge which gradually covered gradually the surface of the aluminium plate. The efficiency of phosphorus removal in Run C was 86.3% at the HRT of 3.2 hours. Especially, the efficiency of phosphorus removal in Run C was higher than that in Run B.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.1
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• pp.45-50
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• 2012

The plate fin and tube type of heat exchanger is widely used in air conditioner, and the heat exchanger is assembled by the mechanical expansion of copper tubes and fastening the aluminum fin. The objective of the present study is to investigate how the mechanical expansion of copper tube affects on the heat transfer performance of a plate fin and tube type heat exchanger. This study has been performed by experimental and numerical methods. The numerical and experimental results show that the tube expansion ratio has a influence on the heat transfer performance. Within the tested expansion ratio, the contact pressure shows the peak value and it decreases as the expansion ratio increases. Air-side heat transfer coefficient increases until the expansion ratio reaches 1.23, and then decreases with the similar pattern to the contact pressure. Also, contact heat transfer coefficient shows the maximum when the contact pressure is highest as well as the air-side heat transfer coefficient.