• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.476-476
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• 2011

Introduction of CNTs into a metal matrix has been considered to improve the mechanical properties of the metal matrix. However, the binding energy between metals and pristine CNTs wall is known to be so small that the interfacial slip between CNTs and the matrix occurs at a relatively low external stress. The interfacial strength between CNT and metal matrix is thus one of the key factors for successful development of the CNT/metal composites. Defective or functionalized CNT has been considered to enhance the interfacial strength of nanocomposites. In the present work, we design the various realistic hybrid structures of the single wall CNT/Cu complexes and characterize the interaction between single wall CNTs and Cu nano-particle and Cu13 cluster using first principle calculations. The characteristics of functionalized CNTs with various surface functional groups, such as -COOH, -OH, and -O interacting with Cu are investigated. We found that the binding energy can be enhanced by the surface functional group including oxygen since the oxygen atom can mediate and reinforce the interaction between carbon and Cu. These results strongly support the recent experimental work which suggested the oxygen on the interface playing an important role in the excellent mechanical properties of the CNT/Cu composite.

• Nuclear Engineering and Technology
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• 제32권2호
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• pp.142-156
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• 2000

An experimental study of steam condensation on a subcooled thick water layer (0.018 ~0.032 m) in a countercurrent stratified flow has been performed using a nearly horizontal circular pipe. A total of 103 average interfacial condensation heat transfer coefficients were obtained and parametric effects of steam and water flow rates and the degree of subcooling on condensation heat transfer were examined. The measured local temperature and velocity distributions in the thick water layer revealed that there was a thermal stratification due to the lack of full turbulent thermal mixing in the lower region of the water layer Two empirical Nusselt number correlations, one in terms of average steam and water Reynolds numbers, and the water Prandtl number, and the other in terms of the Jakob number in place of the Prandtl number, which agree with most of the data within $\pm$ 25%, were developed based on the bulk flow properties. Comparisons of the present data with existing correlations showed that the present data were significantly lower than the values predicted by existing correlations.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
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• pp.1622-1624
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• 2006

We introduce a modified UV-imprint lithography, a resin transfer from the template to the substrate. We analyzed this method by considering the surface and interfacial free energies of the template-resinsubstrate system. This technique is purely fast and applicable to large area patterning.

• 전기화학회지
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• 제7권4호
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• pp.211-219
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• 2004

A classical Lippmann equation valid for liquid electrodes can not describe the interfacial properties of solid electrodes due to the elastic surface strain on solid electrodes. Although there have been many attempts to derive the thermodynamic equations for solid electrodes Outing the past few decades, their validity has been still questioned by many researchers. In practice, although there are various experimental techniques to measure surface energy of solid electrodes, the results obtained by each technique are rather inconsistent due to the complexity of the surface strain on solid electrodes. This article covers these controversial issues in surface energy of solid electrodes. After giving brief summaries of the definition of the important thermodynamic parameters and the derivation of the thermodynamic equations for solid electrodes, the several experimental methods were introduced for the measurement of surface energy of solid electrodes. And then we discussed in detail the inconsistent results in the measurement of the potential of zero charge (pac) and the potential of electrocapillary maximum (ecm).

• Composites Research
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• 제30권3호
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• pp.169-174
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• 2017

유리섬유(GF) 강화 복합재료는 금속에 비해 경량화의 장점으로 인해 기체 부품 산업의 높은 성장률과 방산 산업의 발전으로 수요는 증가되고 있으며 제품의 형태를 다양하게 제작할 수 있는 RTM 공정으로 산업적으로 이용되고 있다. 본 연구에서는 경화제의 분자량에 의한 가교 밀도 차이에 따라 변화되는 RTM의 성형성과 복합재료의 기계적 물성 및 계면 물성의 차이를 관찰하고자 하였다. 이를 위해 동일한 에폭시를 사용하였으며 유사한 화학 구조의 경화제를 이용하였다. 시편은 RTM 공법으로 제작하였으며 기지의 특성을 알아보기 위해 점도 측정 및 기지 주입시간을 측정하였다. 유리 섬유/에폭시 복합재료의 기계적 물성을 실험하여 굴곡 강도를 측정하였으며 계면 물성을 평가하기 위해 층간전단강도(ILSS)와 계면전단강도(IFSS)를 측정하였다. RTM 공정 시 기지의 점도에 의해 섬유의 함침정도에 따라 복합재료의 섬유 무게 분율(wt %)은 변화되고 이에 따라 유리섬유/에폭시 복합재료의 기계적 물성의 차이가 확인되었다.

• Composites Research
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• 제29권5호
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• pp.249-255
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• 2016

섬유금속적층판은 우수한 피로특성, 내부식성, 충격저항 등으로 인하여 항공우주산업에서 널리 사용되고 있다. 본 논문에서는 다구찌 기법을 사용하여 섬유금속적층판의 내부 에너지 해방률을 향상시킬 수 있는 공정 조건을 도출하는 절차에 대해 실험적 연구가 수행되었다. 내부 접착력 향상을 위한 제조공정을 도출하기 위해서, 표면처리, 접착필름의 용융점 유지시간 및 초기 압력이 서로 다르다는 조건하에서 제작한 시편들에 대해서 Double cantilever beam과 End-notched flexure 시험을 수행하였다. 시험으로부터 모드 I과 모드 II의 에너지 해방률을 측정한 후, 다구찌 기법의 망대특성에 의한 신호 잡음비를 비교하여 효율적인 제조공정을 도출하였다.

• 마이크로전자및패키징학회지
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• 제10권3호
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• pp.37-42
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• 2003

전자 패키징에 사용되는 솔더합금에 납을 함유됨으로써 인하여 야기되는 환경적 문제와 인체 유해성 때문에 Pb-Sn 합금계를 대체할 수 있는 새로운 무연 솔더 재료의 필요성이 대두되고 있다. 새로운 솔더합금의 개발에 있어서 솔더 조인트의 신뢰성이 가장 중요한 문제라고 할 수 있는데, 솔더 조인트의 신뢰성은 솔더와 기판 사이의 계면 반응 형태와 그 정도에 의해서 크게 영향을 받기 때문에 솔더와 기판 사이의 계면 현상에 관한 더 깊은 이해가 필요하게 된다 솔더링 동안 기판/솔더 계면에서 가장 먼저 생성되는 금속간 화합물의 상을 예측하기 위한 열역학적인 방법이 제안되었다. 계면 에너지와 석출 구동력의 함수로 표현되는 각각의 금속간 화합물에 대한 핵생성 활성화 에너지를 비교함으로써 활성화 에너지가 가장 낮은 금속간 화합물이 가장 먼저 생성된다고 예측하였다. 거기에 더해 에너지를 기반으로 한 계산을 통하여 솔더 조인트에서 금속간 화합물의 입자 형상을 설명하였다. 울퉁불퉁한 계면을 가진 금속간 화합물의 Jackson의 parameter 값은 2보다 작은 반면 평평한 입자의 경우 2보다 크게 된다.

• Journal of Welding and Joining
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• 제31권3호
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• pp.31-38
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• 2013

The transition of serrated grain boundary and its effect on liquation behavior in the simulated weld heat-affected zone (HAZ) have been investigated in a wrought Ni-based superalloy Alloy 263. Recently, the present authors have found that grain boundary serration occurs in the absence of adjacent coarse ${\gamma}^{\prime}$ particles or $M_{23}C_6$ carbides when a specimen is direct-aged with a combination of slow cooling from solution treatment temperature to aging temperature. The present study was initiated to determine the interdependence of the serration and HAZ property with a consideration of this serration as a potential for the use of a hot-cracking resistant microstructure. A crystallographic study indicated that the serration led to a change in grain boundary character as special boundary with a lower interfacial energy as those terminated by low-index {111} boundary planes. It was found that the serrated grain boundaries are highly resistant to boron enrichment, and suppress effectively grain coarsening in HAZ. Furthermore, the serrated grain boundaries showed a higher resistance to susceptibility of liquation cracking. These results was discussed in terms of a significant decrease in interfacial energy of grain boundary by the serration.

• 대한기계학회논문집
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• 제18권3호
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• pp.540-547
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• 1994

Contact and frictional locking conditions and the effect of shielding due to contact at the facet, which could be represented by the difference in energy release rate, as a function of phase angle of loading are analyzed in this study for the case of interfacial cracks by assuming single crack-kink model. The analysis of contact effects on interfacial fracture resistance shows that relative shielding increases as the shear component was increased, which indicates a qualitative agreement with the previous experimental results.

• 한국전기전자재료학회논문지
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• 제33권4호
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• pp.255-262
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• 2020

Grain boundaries play a major role in determining device performance, particularly of polysilicon-based photodetectors. Through the post-annealing of as-deposited polysilicon and then, the analysis of electric behavior for a metal-polysilicon-metal (MSM) photodetector, we were able to identify the influence of grain boundaries. A modified model of polysilicon grain boundaries in the MSM structure is presented, which uses a crystalline-interfacial layer-SiO_x layer- interfacial layer-crystalline system that is similar to the Si-SiO₂ system in MOS device. Hydrogen passivation was achieved through a hydrogen ion implantation process and was used to passivate the defects at both interfacial layers. The thin SiO_x layer at the grain boundary can enhance the photosensitivity of an MSM photodetector by decreasing the dark current and increasing the light absorption.