• Korea-Australia Rheology Journal
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• 제17권2호
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• pp.35-40
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• 2005

Nanofluid is a novel heat transfer fluid prepared by dispersing nanometer-sized solid particles in traditional heat transfer fluid to increase thermal conductivity and heat transfer performance. In this research we have considered the rheological properties of nanofluids made of CuO particles of 10-30nm in length and ethylene glycol in conjunction with the thermal conductivity enhancement. When examined using TEM, individual CuO particles have the shape of prolate spheroid of the aspect ratio of 3 and most of the particles are under aggregated states even after sonication for a prolonged period. From the rheological property it has been found that the volume fraction at the dilute limit is 0.002, which is much smaller than the value based on the shape and size of individual particles due to aggregation of particles. At the semi-dilute regime, the zero shear viscosity follows the Doi-Edwards theory on rodlike particles. The thermal conductivity measurement shows that substantial enhancement in thermal conductivity with respect to particle concentration is attainable only when particle concentration is below the dilute limit.

• 한국분말재료학회지
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• 제23권3호
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• pp.228-234
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• 2016

Copper nanoparticles attract much attention as substitutes of noble metals such as silver and can help reduce the manufacturing cost of electronic products due to their lower cost and good conductivity. In the present work, the chemical reduction is examined to optimize the synthesis of nano-sized copper particles from copper sulfate. Sodium borohydride and ascorbic acid are used as reducing and antioxidant agents, respectively. Polyethylene glycol (PEG) is used as a size-control and capping agent. An appropriate dose of PEG inhibits the abnormal growth of copper nanoparticles, maintaining chemical stability. The addition of ascorbic acid prevents the oxidation of nanoparticles during synthesis and storage. Transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR) are used to investigate the size of the synthesized nanoparticles and the coordination between copper nanoparticles and PEG. For chemical reduction, copper nanoparticles less than 100 nm in size without oxidized layers are successfully obtained by the present method.

• 자원리싸이클링
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• 제23권6호
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• pp.30-39
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• 2014

코로나 방전 정전선별기 내에서 인쇄회로기판(Printed Circuit Board, PCB) 분쇄 입자의 이동궤도를 전산 모사하였다. 여기서 PCB입자는 전자부품 분리된 기판을 파쇄한 것으로, 대부분 구리와 FR-4(Flame Retardant Level-4)로 이루어져있다. 우선 입자가 선별기내 회전전극으로부터 탈착 지점을 계산하였으며, 중력, 원심력, 정전기력의 평형으로부터 유도되었다. 한편 탈착 후 이동궤도는 입자의 운동방정식으로부터 구한 가속도를 시간 적분하여 계산하였다. 시뮬레이션 변수는 입자의 크기, 공급전압의 세기, 회전전극속도 및 유도전극 각도로 하였다. 입자 이동궤도에 미치는 영향은 구리 입자의 경우에는 회전속도가 주요 변수였으나, 반면 FR-4 입자의 경우에는 상기 모든 변수에 영향을 받는 것으로 나타났다.

• 한국분말재료학회지
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• 제10권6호
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• pp.443-447
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• 2003

Nano-sized $TiB_2$ was in situ synthesized in copper matrix through self-propagating high temperature synthesis (SHS) with high-energy ball milled Ti-B-Cu elemental mixtures as powder precursors. The size of $TiB_2$ particles in the product of SHS reaction decreases with time of preliminary mechanical treatment ranging from 1 in untreated mixture to 0.1 in mixtures milled for 3 min. Subsequent mechanical treatment of the product of SHS reaction allowed the $TiB_2$ particles to be reduced down to 30-50 nm. Microstructural change of $TiB_2$-Cu nanocomposite during spark plasma sintering (SPS) was also investigated. Under simultaneous action of pressure, temperature and electric current, titanium diboride nanoparticles distributed in copper matrix move, agglomerate and form a interpenetrating phase composite with a fine-grained skeleton.

• 폴리머
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• 제34권1호
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• pp.84-87
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• 2010

구리, 인디움, 셀레늄 이온을 포함한 혼합물을 전기화학적으로 환원하는 1회 반응으로 CIS 입자를 합성하였다. 합성된 입자를 폴리(옥틸티오펜/풀러렌으로 구성된 벌크이종접합에 블렌딩하거나 박막층으로 삽입하여 여러 가지 광기전셀을 제조하였다. CIS의 함량이 증가할수록 개방전압과 단락전류의 급격한 감소가 일어났다. 이러한 광기전성의 감소현상을 블렌드의 구조, 조성, 모폴로지를 분석 해석하였다.

• 한국재료학회지
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• 제11권5호
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• pp.413-418
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• 2001

황산구리 전해욕에 분산제인 콜리이달 실리카($SiO_2$현탁액)를 첨가시키는 분산도금의 방법을 이용하여 음극에 석출하는 전해 석출물의 결정구조, 표면형상, 결정방향 등의 변화를 검토하였고 내식성, 물리적 특성 또한 조사하였다. 콜로이달 실리카를 분산시킨 구리 전해욕의 석출피막의 특성에 대해서 조사한 결과, 다음과 같은 결론을 얻었다. 전해 석출피막의 결정입자가 미세화 되고, 균일하게 성장됨은 물론, 결정 수가 증가하였으며, 콜로이달 실리카의 분산 효과에 의해서 전해 석출피막의 경도가 대략 16%까지 상승하였다. 또한 콜로이달 실리카를 분산시킨 극리 전착층의 X-선 회절패턴이 (111)면, (200)면과 (311)면이 거의 소멸되어 우선 방위가 (111)에서 (110)면으로 변화되었다. 부식전위의 측면에서도 콜로이달 실리카의 흡착 효과에 의해서 구리 전착층의 전위가 귀하게 이동하는 효과를 얻을 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제23권4호
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• pp.563-566
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• 2002

Copper complexes have been directly incorporated into cellulose acetate (CA) and the resulting light blue colored homogeneous films of 5-20 wt.% copper acetate complex concentrations are found to be thermally stable up to 200 $^{\circ}C$. The reaction chem istry of Cu in CA has been investigated by reacting them with small gas molecules such as CO, H2, D2, O2, NO, and olefins in the temperature range of 25-160 $^{\circ}C$, and various Cu-hydride, -carbonyl, -nitrosyl, and olefin species coordinated to Cu sites in CA are characterized by IR and UV/Vis spectroscopic study. The reduction of Cu(II) complexes by reacting with H2 gas at the described conditions results in the formation of Cu2O and copper metal nanoparticles in CA, and their sizes in 30-120 nm range are found to be controlled by adjusting metal complex concentration in CA and/or the reduction reaction conditions. These small copper metal particles show various catalytic reactivity in hydrogenation of olefins and CH3CN; CO oxidation; and NO reduction reactions under relatively mild conditions.

• 한국표면공학회지
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• 제49권3호
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• pp.238-244
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• 2016

Copper electrodeposition on AZ91 Mg alloy was studied in views of preferential deposition on ${\alpha}$- or ${\beta}$- phases and how to achieve uniform deposition over the entire surface on ${\alpha}$- and ${\beta}$-phases in a cyanide solution. The inhomogeneous microstructure of AZ91 Mg alloy, particularly ${\alpha}$- and ${\beta}$-phases, was found to result in non-uniform deposition of zincate layer, preferential deposition of zincate on ${\beta}$-phases, which leads to non-uniform growth of copper layer during the following electrodeposition process. The preferential depositions of zincate can be attributed to higher cathodic polarizations on the ${\beta}$-phases. Pin-hole defects in the copper electrodeposit were observed at the center of large size ${\beta}$-phase particles which is ascribed to gas bubbles formed at the ${\beta}$-phases. The activation of AZ91 Mg alloy in hydrofluoric acid solution was used to obtain uniform growth of zincate layer on both the ${\alpha}$- and ${\beta}$-phases. By choosing an optimum activation time, a uniform zincate layer was obtained on the AZ91 Mg alloy surface and thereby uniform growth of copper was obtained in a cyanide copper electroplating solution.

• Tribology and Lubricants
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• 제34권6호
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• pp.226-234
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• 2018

Copper chemical mechanical planarization (CMP) has become a key process in integrated circuit (IC) technology. The results of copper CMP depend not only on the mechanical abrasion, but also on the slurry chemistry. The slurry used for Cu CMP is known to have greater chemical reactivity than mechanical material removal. The Cu CMP slurry is composed of abrasive particles, an oxidizing agent, a complexing agent, and a corrosion inhibitor. Citric acid can be used as the complexing agent in Cu CMP slurries, and is widely used for post-CMP cleaning. Although many studies have investigated the effect of citric acid on Cu CMP, no studies have yet been conducted on the interfacial friction characteristics and step height reduction in CMP patterns. In this study, the effect of citric acid on the friction characteristics and step height reduction in a copper wafer with varying pattern densities during CMP are investigated. The prepared slurry consists of citric acid ($C_6H_8O_7$), hydrogen peroxide ($H_2O_2$), and colloidal silica. The friction force is found to depend on the concentration of citric acid in the copper CMP slurry. The step heights of the patterns decrease rapidly with decreasing citric acid concentration in the copper CMP slurry. The step height of the copper pattern decreases more slowly in high-density regions than in low-density regions.

• 공업화학
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• 제35권2호
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• pp.96-99
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• 2024

구리 마이크로입자의 표면을 나노섬유형태의 포름산구리로 합성하고 포름산과 혼합하여 구리판을 접합할 수 있는 소결 페이스트를 합성하였다. 평균 10 ㎛의 구리 마이크로입자는 400 ℃ 이상에서 표면이 산화구리 나노섬유로 합성되고 포름산과 혼합하여 표면이 포름산화된 구리 마이크로입자가 합성된다. 포름산구리는 구리 벌크입자나 나노입자의 녹는점에 비해 낮은 온도인 210 ℃에서 구리로 분해되어 저온 소결로 구리판의 접합이 가능하다. 표면을 나노섬유 형태로 제어하여 표면적을 높여 포름산구리로의 반응속도, 응집에 필요한 접촉면적, 포름산구리의 분해속도 등이 증가하여 짧은 시간에 소결할 수 있도록 하였다.