• 비파괴검사학회지
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• 제23권3호
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• pp.205-211
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• 2003

구조물의 안전성평가와 관련하여 비파괴평가 방법 중에서 음향방출 (acoustic emission, AE)기법에 의한 비파괴적 결함 발생 검출 기법은 다른 기법에 비해 비교적 새로운 평가기술로서 구조물의 이상 유무를 조기에 진단하고 주기적으로 감시할 수 있는 온-라인 모니터링에 적합하다. 그러나 한편, 국내에서는 아직까지 이에 대한 체계적인 연구가 미비한 실정이며, 대부분 값비싼 외국 시스템을 도입하여 사용하고 있는 실정이다 뿐 만 아니라 기존의 음향방출 시스템은 장치의 특성상 시스템이 매우 복잡하고 가격이 고가인 관계로 다양한 산업분야에서 실제 현장에 적용하기가 쉽지 않다. 따라서 본 연구에서는 기존의 음향방출 시스템이 가지고 있던 불필요한 낭비적인 요소들을 제거하고 실제 산업현장에 부합하는 위치표정 시스템을 개발하고자 하였다. 한편, 기존의 AE 시스템들은 위치표정을 위한 신호분석이 난해할 뿐만 아니라 박판 구조물의 경우는 위치표정이 매우 어렵다. 본 연구에서는 시간-주파수 해석에 널리 사용되고 있는 웨이블릿 기법을 이용하여 보다 정확한 위치표정을 진단하는 기법을 수행하였다.

• Smart Structures and Systems
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• 제18권3호
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• pp.471-484
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• 2016

Optical fiber sensors have been proven that they have the potential to detect high-frequency ultrasonic signals, in structural health monitoring field which generally refers to acoustic emission signals from active structural damages and guided waves excited by ultrasonic actuators and propagating in waveguide. In this work, the sensing properties of optical fiber sensors based on Mach-Zehnder interferometer were investigated in the metal plate. Analytical formulas were conducted first to explore the parameters affecting its sensing performances. Due to the simple and definable frequency component, the Lamb wave excited by the piezoelectric wafer was employed to study the sensitivity of the proposed optical fiber sensors with respect to the frequency, rather than the acoustic emission signals. In the experiments, according to above investigations, spiral shape optical fiber sensors with different size were selected to increase their sensitivity. Lamb waves were excited by a circular piezoelectric wafer, while another piezoelectric wafer was used to compare their voltage responses. Furthermore, by changing the excitation frequency, the tuning frequency characteristic of the proposed optical fiber sensor was also investigated experimentally.

• Carbon letters
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• 제14권4호
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• pp.255-258
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• 2013

Flexible transparent conducting films (TCFs) were fabricated by dip-coating single-wall carbon nanotubes (SWCNTs) onto a flexible polyethylene terephthalate (PET) film. The amount of coated SWCNTs was controlled simply by dipping number. Because the performance of SWCNT-based TCFs is influenced by both electrical conductance and optical transmittance, we evaluated the film performance by introducing a film property factor using both the number of interconnected SWCNT bundles at intersection points, and the coverage of SWCNTs on the PET substrate, in field emission scanning electron microscopic images. The microscopic film property factor was in an excellent agreement with the macroscopic one determined from electrical conductance and optical transmittance measurements, especially for a small number of dippings. Therefore, the most crucial factor governing the performance of the SWCNT-based TCFs is a SWCNT-network structure with a large number of intersection points for a minimum amount of deposited SWCNTs.

• Corrosion Science and Technology
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• 제20권5호
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• pp.256-265
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• 2021

Titanium is applied in various industries due to its valuable properties and abundant reserves. Generally, if a highly uniform oxide structure and a high-density oxide film is formed on the surface through anodization treatment, the utility value such as color appearance and corrosion inhibition efficiency is further increased. The objective of this study was to determine improvement of water-repellent property by controlling titanium oxide parameters such as pore size and inter-pore distance to improve corrosion resistance. Oxide film structures of different shapes were prepared by controlling the anodization processing time and voltage. These oxide structures were then analyzed using a Field Emission Scanning Electron Microscope (FE-SEM). Afterwards, a Self-Assembled Monolayer (SAM) coating was performed for the oxide structure. The contact angle was measured to determine the relationship between the shape of the oxide film and the water-repellency. The smaller the solid fraction of the surface, the higher the water-repellent effect. The surface with excellent hydrophobic properties showed improved corrosion resistance. Such water-repellent surface has various applications. It is not only useful for corrosion prevention, but also useful for self-cleaning. In addition, a hydrophobic titanium may open up a new world of biomaterials to remove bacteria from the surface.

• Corrosion Science and Technology
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• 제22권2호
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• pp.99-107
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• 2023

Layered silicate clay montmorillonite (MMT) has been used in nanocomposite coating to improve corrosion protection by reinforcing the barrier property. The better dispersion of MMT in the coating produces a higher barrier effect. Pretreatment with MMT could favor the delamination of clay platelets, facilitating MMT dispersion in the coating. In the present work, a montmorillonite/silica (MMT/Si) composite was prepared by the in situ sol-gel method. x-ray diffraction measurements and field-emission scanning electron microscopy observations showed silica crystal formation and increased basal spacing between the MMT platelets. Composite MMT/Si particles were introduced in an epoxy resin to reinforce the corrosion protection of the coating applied on the AA2024 surface. Electrochemical impedance spectroscopy (EIS) was performed to characterize the protective property of the coating. The results demonstrated the high barrier effect of the coating containing 5 wt% of MMT/Si. Adhesion evaluation after a salt spray test exhibited a high adherence to the epoxy coating containing MMT/Si.

• 한국분말재료학회지
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• 제24권4호
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• pp.308-314
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• 2017

$Fe_3O_4$/Fe/graphene nanocomposite powder is synthesized by electrical wire explosion of Fe wire and dispersed graphene in deionized water at room temperature. The structural and electrochemical characteristics of the powder are characterized by the field-emission scanning electron microscopy, X-ray diffraction, Raman spectroscopy, field-emission transmission electron microscopy, cyclic voltammetry, and galvanometric discharge-charge method. For comparison, $Fe_3O_4$/Fe nanocomposites are fabricated under the same conditions. The $Fe_3O_4$/Fe nanocomposite particles, around 15-30 nm in size, are highly encapsulated in a graphene matrix. The $Fe_3O_4$/Fe/graphene nanocomposite powder exhibits a high initial charge specific capacity of 878 mA/g and a high capacity retention of 91% (798 mA/g) after 50 cycles. The good electrochemical performance of the $Fe_3O_4$/Fe/graphene nanocomposite powder is clearly established by comparison of the results with those obtained for $Fe_3O_4$/Fe nanocomposite powder and is attributed to alleviation of volume change, good distribution of electrode active materials, and improved electrical conductivity upon the addition of graphene.

• 한국진공학회지
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• 제18권1호
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• pp.73-78
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• 2009

본 연구에서는 metal oxide chemical vapor deposition (MOCVD)을 이용하여 p형 실리콘(100) 기판 위에 30 nm 두께의 산화 아연 완충층을 $500^{\circ}C$ 에서 증착 시킨 후, 그 위에 산화 아연 나노로드를 수열합성법을 이용하여 성장시켰다. 그리고 산화아연 나노로드 성장 시 0.02몰${\sim}$0.5몰의 다양한 농도의 전구체를 사용함으로써 그에 따라 변화되는 산화 아연 나노로드의 배열상태, 구조적, 그리고 광학적 특성 평가를 실시하였다. 특성 평가는 FE-SEM(field emission scanning electron microscopy), XRD(X-ray diffraction), 그리고 PL(photoluminescence) 등의 분석 방법들을 통해 이루어졌다 본 연구를 통하여 전구체의 농도가 증가할수록 나노로드의 직경과 길이가 길어지며 0.3몰의 농도에서 뛰어난 광학 특성이 나타나는 것을 발견할 수 있었다.

• 전기전자학회논문지
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• 제23권3호
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• pp.904-909
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• 2019

$100^{\circ}C$에 소성한 인듐 아연 산화막 (IZO)을 이온빔 처리하여, 균일할 수평 액정 배향을 구현하였다. 유리 기판 위에 코팅된 IZO 박막을 $100^{\circ}C$에 소성하고 액정 배향 기술로 이온빔을 사용하였다. 이것을 이용하여 얻어진 액정 배향의 특성을 분석하기 위해서, 편광 현미경과 결정 회전법을 사용하였다. 또한 이온빔 처리된 IZO 박막을 이용하여 만든 액정 셀이 높은 품질의 액정 소자에 충분한 열적 안정성을 가진다는 것을 확인할 수 있었다. 그리고 전계방출 주사 전자 현미경을 이용하여 이온빔의 IZO 박막의 표면에 미치는 영향을 분석하였다. 이것을 통하여 이온빔이 IZO 박막 표면의 거칠기를 변화시키고, 액정 배향에 영향을 준다는 것을 확인할 수 있었다. 마지막으로 IZO 박막으로 제작한 액정 셀의 전기-광학 특성을 측정하였다. 그리고 이것이 기존에 사용되는 러빙법 처리된 폴리이미드 박막으로 제작한 액정 셀보다 뛰어난 특성을 가진다는 것을 확인하였다. 또한 액정 고정 에너지를 측정하여 이것이 균일한 액정 배향을 구현하기 위한 적합한 특성을 가진다는 것을 확인하였다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.465-467
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• 2004

We presented a systematic investigation on the growth of CNTs including SWNTs on nano-catalyst-embedded particles by PECVD. For CNTs growth, the mixture of $C_2H_2$ and $NH_3$ was used. The total pressure and temperature were kept at 3.25 Torr and 650 $^{\circ}C$, respectively. Finally, we measured the field emission property from CNTs grown from nano-catalyst embedded zeolite particles in vacuum chamber (<$10^{-7}$ Torr).

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 춘계학술대회 논문집 센서 박막재료연구회 및 광주 전남지부
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• pp.73-74
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• 2008

In this paper, we have investigated dispersibility, volume resistivity of nano-composite by solution mixing method. Dispersibility measured by FE-SEM(Field Emission Scanning Electron Microscope. And volume resistivity measured by ASTM D991. To expect interaction used dual filler system. But, dual filler system had influence on polymer complex. So, polymer chain mobility doesn't resist.