• 한국재료학회지
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• 제19권8호
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• pp.432-436
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• 2009

A Cu-Fe-P copper alloy was processed by accumulative roll-bonding (ARB) for ultra grain refinement and high strengthening. Two 1mm thick copper sheets, 30 mm wide and 300 mm long, were first degreased and wire-brushed for sound bonding. The sheets were then stacked on top of each other and roll-bonded by about 50% reduction rolling without lubrication at ambient temperature. The bonded sheet was then cut into two pieces of the same dimensions and the same procedure was repeated for the sheets up to eight cycles. Microstructural evolution of the copper alloy with the number of the ARB cycles was investigated by optical microscopy (OM), transmission electron microscopy(TEM), and electron back scatter diffraction(EBSD). The grain size decreased gradually with the number of ARB cycles, and was reduced to 290 nm after eight cycles. The boundaries above 60% of ultrafine grains formed exhibited high angle boundaries above 15 degrees. In addition, the average misorientation angle of ultrafine grains was 30 degrees.

• 한국태양에너지학회 논문집
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• 제23권3호
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• pp.15-22
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• 2003

This study deals with the collection of solar energy and its storage in evacuated tubular collector systems for different types of header design, flow passage and heat transfer devices. In order to elicit the most efficient combination of header design, flow passage, heat transfer hardware and operating conditions, a series of tests were done for the four different types of solar collectors utilizing vacuum tubes. The systems studied here either has the evacuated collector tubes with a metal cap on one end or the all-glass evacuated solar collector tubes These evacuated tubular collectors are known to be more efficient than the flat-plate ones in both direct and diffuse solar radiation. Test results show that the system comprised of the all-glass evacuated tubes with U-shaped copper pipes inside outperforms the other configurations. Especially, a rolled copper sheet tightly placed along the inner surface of each inner tube enhances heat transfer between the heated collector surface and the water contained in the U-shaped copper pipe.

• 대한금속재료학회지
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• 제48권10호
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• pp.942-950
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• 2010

The microstructure and mechanical properties of a Cu-Fe-P copper alloy processed by differential speed rolling (DSR) were investigated in detail. The copper alloy, with a thickness of 3 mm, was rolled to 50% reduction at ambient temperature without lubrication with a differential speed ratio of 2.0:1 and then annealed for 0.5h at various temperatures ranging from 100 to $800^{\circ}C$. Conventional rolling was performed under the same rolling conditions for comparison. The shear strain introduced by the conventional rolling process showed positive values at the positions of the upper roll side and negative values at the positions of the lower roll side. However, the result was zero or positive values at all positions for samples rolled by DSR. The effects of DSR on the microstructure and mechanical properties of the as-rolled and subsequently annealed samples are discussed.

• 대한금속재료학회지
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• 제48권1호
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• pp.77-84
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• 2010

Annealing characteristics of an oxygen free copper (OFC) processed by differential speed rolling (DSR) were investigated in detail. An OFC sample with a thickness of hum was rolled to 35% reduction at ambient temperature without lubrication, varying the differential speed ratio from 1.0:1 to 2.2:1, and then annealed for 0.5h at various temperatures from 100 to $400^{\circ}C$. Different recrystallization behavior was observed depending on the differential speed ratio, especially in the case of annealing at $200^{\circ}C$ Complete recrystallization occurred in the specimens annealed at temperatures above $250^{\circ}C$ regardless of the differential ratios. The hardness distribution in the thickness direction of the rolled OFC sheets varied depending on the differential speed ratios. These annealing characteristics were explained by the magnitude of shear strain introduced during rolling.

• 대한금속재료학회지
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• 제47권11호
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• pp.740-747
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• 2009

The purpose of this study is to identify the effect of electrolyte compositions on electrodeposited copper foil. First of all, the polyimide substrate was pretreated with plasma. Finally, copper foil was deposited on a Cu/Ni/Polyimide substrate using the electroplating technique. As the quantity of Cu increased, preferred orientations changed into (111). Increasing sulfuric acid, on the other hand, brought down the preferred orientation of (111). The lowest sheet resistance, surface roughness, and fine adhesion were detected when the ratio of $Cu^{2+}$ and $H_2SO_4$ is 50:50(g/l).

• 대한금속재료학회지
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• 제47권2호
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• pp.121-128
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• 2009

The strain, microstructure and mechanical properties through thickness of an oxygen free copper(OFC) processed by differential speed rolling(DSR) were investigated in detail. The OFC sample with thickness of 1 mm was rolled to 35% reduction at ambient temperature without lubrication changing the differential speed ratio from 1.0:1 to 2.2:1. The shear strain introduced by the conventional rolling showed positive values at positions of upper roll side and negative values at positions of lower roll side. However, it showed zero or positive values at all positions for the samples rolled by the DSR. The effects of strain distribution through thickness of the coper sheets on microstructure, texture and mechanical properties are discussed in the present study.

• 소성∙가공
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• 제21권6호
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• pp.348-353
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• 2012

Micro-drawn parts have received wider acceptance as products become smaller and more precise. The subject of this study was the deformation characteristics of ultra thin sheet metal in micro drawing of a rectangular shaped part. The influence of drawing speed and blank holding force on the product quality was investigated in micro-drawing of ultra thin sheet of beryllium copper (C1720) alloy. The specimen had a diameter of 4.8 mm and a thickness of $50{\mu}m$. Experiments were carried out in which, different blank holding force and drawing speed were considered. The product quality was evaluated by measuring the thickness and hardness along two specified directions, namely, the side and diagonal directions. The distribution of the thickness strain showed severe thinning especially around the punch radius in both directions. In the diagonal direction, thickening occurred in the flange area due to the axi-symmetric drawing mode. The increase of blank holding force and/or drawing speed was found to cause severe thinning around the punch radius. The blank holding force had a greater effect on thinning of the product than the drawing speed.

• Journal of Welding and Joining
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• 제31권6호
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• pp.27-31
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• 2013

Magnesium alloy is used on parts of aircraft and electronic equipment because of the highest specific strength among the common metal materials. Recently, studies about appling magnesium alloy sheet to automotive bodies are on the increase rapidly. For application to automotive bodies, researches about characteristics of resistance spot welding of magnesium alloy sheet are essential. Magnesium alloy has low boiling point, so getting sound bead shape is difficult when appling varies welding processes. Resistance spot welding is also particular about setting optimum welding conditions because of spatter generation, pores and cracks occurrence in nugget. And life of electrodes is very short because of alloying with copper that main material of electrodes. This requires frequent dressing and replacement of electrodes and decrease in productivity of resistance spot welding on magnesium alloy. Therefore in this study, for effective analysis of changes in tensile shear load and nugget size during electrode life test, evaluate detail characteristics of resistance spot welding on magnesium alloy sheet using dome type electrode.

• 한국광학회지
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• 제32권3호
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• pp.114-119
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• 2021

산업용으로 이용하는 대면적 그래핀 시트는 주로 Cu foil 위에서 화학증기증착법(chemical vapor deposition, CVD)을 이용하여 성장된다. 그러나 모든 면적에서 균일하게 성장되는 것은 아니므로, 품질이 불만족스러운 그래핀 필름을 제외시키는 과정이 필수적으로 요구된다. 비침습적인 반사형 광학적인 방법을 사용하면, 그래핀의 성장프로세스 도중이나 성장 후에 빠르고 편리하게 분류할 수 있다. 본 논문에서는 국소적인 그래핀 필름의 파장별 반사 대비율(reflectance contrast)이 그래핀의 품질과 밀접한 관련이 있어 품질이 불만족스러운 그래핀 필름을 제외시키는 데에 효과적인 데이터로 이용될 수 있음을 밝혔다. 파장별 반사 대비율을 계산하기 위해서, 화학적 퍼텐셜(chemical potential)과 전자간 널뛰기(hopping) 에너지, 그리고 온도 등의 요소가 성장된 그래핀의 광학적 반사 대비율에 어떠한 영향을 미치는지 조사하였다.

• 마이크로전자및패키징학회지
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• 제10권4호
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• pp.29-33
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• 2003

n-형 탄화규소 반도체에 대한 구리금속을 이용하여 오옴성 접촉 구조를 제작하였다. 제작된 구리접촉에 대해 후속열처리 조건과 금속접촉 구조에 따른 재료적, 전기적 성질의 변화를 조사하였다. 금속접촉의 오옴성 성질은 금속박막의 구조 뿐 아니라 열처리조건에 대해서도 크게 좌우됨을 알 수 있었다. 열처리는 급속열처리 장치를 이용한 진공상태 및 환원 분위기에서 2단계 열처리방식을 통하여 시행하였다. 접촉비저항의 측정을 위해 TLM 구조를 만들었으며 면저항 ($R_{s}$), 접합저항 ($R_{c}$), 이동거리 ($L_{T}$), 패드간거리 (d), 전체저항 ($R_{T}$) 값을 구하여 알려진 계산식에 의해 접촉비저항 ($p_{c}$) 값을 추정하였다. 진공보다 환원분위기에서 후속 열처리를 수행한 시편이 양호한 전기적 성질을 가짐을 알 수 있었다. 가장 양호한 결과는 Cu/Si/Cu 구조를 가진 금속접촉 결과이었으며 접촉비저항 ($p_{c}$)은 $1.2\times 10^{-6} \Omega \textrm{cm}^2$의 낮은 값을 얻을 수 있었다. 재료적 성질은 XRD를 이용하여 분석하였고 SiC 계면 상에 구리와 실리콘이 결합한 구리 실리사이드가 형성됨을 알 수 있었다.