• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.04a
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• pp.74-75
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• 2007

최근에는 휴대성과 유연성이 뛰어난 다목적 디스플레이의 연구가 활발히 진행되고 있는데, 이러한 기술의 핵심 능동소자로서 저비용, 대면적의 응용, 휘어짐 등의 장점을 가지는 유기박막 트랜지스터(Organic Thin Film Transistors)가 널리 연구되고 있다. 본 연구에서는 기존에 문제시 되는 유기 절연체의 저유전상수와 높은 누설전류를 보완하기 위하여 나노복합 (nanocomposite) 게이트 절연체에 대한 연구를 수행하였다. 기존의 유기물 절연체가 가지는 문제점인 높은 누설전류 특성을 보완하기 위하여 높은 전기적 절연성과 고유전상수를 가지는 알루미나 ($Al_2O_3$)의 나노입자와 유기절연체의 나노복합체 박막을 형성시키고 이를 적용한 결과 게이트 누설전류를 억제시키어 소자의 특성을 향상시킬 수 있었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.111-111
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• 2010

최근 전자 소자의 집적기술은 기존의 2차원에서 System on package (SOP) 개념에 기반을 둔 3차원 집적 기술로 발전 되어가고 있다. 소자의 3차원 실장을 실현시키는 과정에서 세라믹의 여러 유용성이 언급되어져 왔지만, 취성이 매우 크다는 등의 단점이 있었다. 이러한 이유로 연성을 가지는 폴리머와 세라믹을 합성한 복합체 기판에 대하여 많은 연구가 되고 있다. 그러나 세라믹 제작을 위해서는 높은 공정온도가 요구되고 있고 이러한 높은 공정상에서의 온도는 3차원 실장에 있어서 문제점이 되고 있다. 이러한 문제점을 극복하기 위하여 상온에서 치밀한 세라믹 후막을 제작할 수 있는 공정인 Aerosol Deposition Method (ADM)방법으로 세라믹-폴리머 후막의 제조를 시도하였다. 일반적으로 ADM은 수백 나노의 출발 파우더를 사용하여 치밀한 세라믹 막을 형성하는데 사용된다. 본 연구에서는 ADM으로 100 nm미만의 나노 세라믹 파우더를 사용하여 다공성의 세라믹 후막을 제조한 후 resin을 함침시키는 방법으로 세라믹-폴리머 후막의 제조를 시도하였다. 그 결과 운송가스, aerosol 농도 등의 공정조건을 변화시켜 다공성의 $Al_2O_3$ 후막을 제조하였고, 이 다공성 후막은 반투명의 특성을 보이며 고충전율로 형성되었다. 이렇게 제조된 나노 다공성 $Al_2O_3$ 후막에 cyanate ester resin을 함침시키는 방법을 사용하여 $Al_2O_3$-cyanate ester 복합체 후막을 제조하였으며, 이의 비유전율 및 품질계수는 각각 1 MHz에서 6.7, 1000으로 우수한 유전특성을 보임이 확인되었다.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.537-544
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• 2020

The interfacial transition zone(ITZ) which is the boundary layer between cement composites and aggregates is considered to be the region of gradual transition, heterogeneous, and the weakest part of concrete. For the development of lightweight high strength concrete, it is essential to evaluate the mechanical properties of ITZ between high strength concrete with low water-binder ratio and lightweight aggregates. However, the mechanical properties of ITZ are not well established due to its high porosity and complex structure. Furthermore, the properties of ITZ in concrete using lightweight aggregates are dominated by more various variations (e.g. water-binder ratio, water absorption capacity of aggregate, curing conditions) than normal-weight aggregate concrete. This study aims to elucidate the mechanical properties of ITZ in lightweight high-strength cement composites according to the types of aggregates and the aggregate sizes. Nanoindentation analysis was used to evaluate the elastic modulus of ITZ between high strength cement composites with the water-binder ratio of 0.2 and normal sand, lightweight aggregate with different aggregate siz es of 2mm and 5mm in this study.

• Journal of the Korean GEO-environmental Society
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• v.17 no.2
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• pp.5-11
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• 2016

$MWCNT-TiO_2$ nano composites and $Ag-MWCNT-TiO_2$ nano composites were prepared from Multi-Walled Carbon NanoTube (MWCNT), titanium (IV) butoxide (TNB) solution and silver nitrate ($AgNO_3$) by the sol-gel method. The dispersion and structure of Ag in the synthesized composites was observed by Scanning Electron Microscopy (SEM) and Field Emission Transmission Electron Microscopy (FE-TEM). X-Ray Diffraction (XRD) patterns of the composites showed that the composites contained an anatase phase. The Energy Dispersive X-ray spectroscopy (EDX) showed the presence of C, O, Ti and Ag peaks. The $TiO_2$ particles were distributed uniformly in the MWCNT network, and Ag particles were virtually fixed on the surface of the tubes. Also decomposition of the methylene blue was investigated according to UV radiation times for study photocatalytic activity. $Ag-MWCNT-TiO_2$ nano composites show high photodegradation than $MWCNT-TiO_2$ nano composites. The results indicate that the high conductivity of Ag improved the photoactivity of the $MWCNT-TiO_2$ composite.

• Polymer(Korea)
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• v.37 no.3
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• pp.308-315
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• 2013

In this study, we performed surface modification of silica nanoparticles with bis[3-(triethoxysilylpropyl)]tetrasulfide (TESPT) silane coupling agent to study the effects of treatment temperature, treatment time, and amount of TESPT used on the silanization degree with Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), elemental analysis (EA) and solid state $^{13}C$ and $^{29}Si$ cross-polarization magic angle spinning (CP/MAS) nuclear magnetic resonance spectroscopy (NMR). We found peak area of isolated silanol groups at $3747cm^{-1}$ decreased, but peak area of $-CH_2$ asymmetric stretching of TESPT at $2938cm^{-1}$ increased with the amount of TESPT from FTIR measurements. We also used universal testing machine (UTM) to study mechanical properties of styrene butadiene rubber (SBR) nanocomposites with 20 phr (parts per hundred of rubber) of pristine and TESPT modified silicas, respectively. The tensile strength and 100% modulus of modified silica/SBR nanocomposite were enhanced from 5.65 to 9.38MPa, from 1.62 to 2.73 MPa, respectively, compared to those of pristine silica/SBR nanocomposite.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.412-412
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• 2016

염료감응 태양전지(dye-sensitized solar cells, DSSCs)는 식물의 광합성원리와 매우 유사한 작동원리를 갖고 있는 전지이며, 간단한 구조, 저렴한 제조단가, 친환경성 등의 등의 장점으로 인하여 많은 관심을 모으고 있다. 이러한 염료감응 태양전지는 빛을 받아들인 염료분자가 전자-홀 쌍을 생성하며 전자는 반도체 산화물을 통해 이동되고 전해질의 산화환원 과정을 통해 염료 분자가 다시 환원되는 순환메커니즘을 따르고 있다. 일반적으로 염료감응 태양전지는 밴드 갭 에너지가 큰 반도체 산화물을 포함하는 작업전극, 산화환원 반응을 통해 전자를 염료로 보내는 전해질, 환원 촉매역할을 하는 상대전극으로 구성되어 있다. 특히, 상대전극으로는 우수한 촉매특성과 높은 전도성을 갖는 백금이 가장 많이 이용되고 있지만 가격이 비싸고 요오드에 취약하기 때문에 상용화에 큰 장애물이다. 따라서, 백금을 대체하기 위해 저가의 탄소나 고분자에 대한 연구가 활발히 진행되고 있고, 그 중 탄소나노섬유(carbon nanofiber, CNFs)는 높은 표면적과 뛰어난 화학적 안정성으로 촉매효율을 증대시킬 수 있어 촉매물질로서 관심이 높아지고 있다. 본 연구에서는 상대전극에 탄소나노섬유기반 복합체를 합성하였고, 성공적으로 저가격 및 고성능의 염료감응 태양전지를 제작하였다. 이때, 지지체인 탄소나노섬유는 전기방사법을 통해 합성하였으며, 수열합성법을 이용하여 금속산화물을 담지하였다. 이렇게 제작된 탄소나노섬유-Fe2O3 복합체는 scanning electron microscopy, transmission electron microscopy, X-ray diffraction, 그리고 X-ray photoelectron spectroscopy 통해 구조적, 화학적 특성을 평가하였으며 전기화학적 특성 및 광전변환 효율을 분석하기 위해 cyclic voltammetry, electrochemical impedance spectroscopy, 그리고 solar simulator를 사용하였다. 본 학회에서 위와 관련된 더 자세한 사항에 대해 논의할 것이다.

• Applied Chemistry for Engineering
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• v.26 no.4
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• pp.515-519
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• 2015

Complexes composed of hydrogen tetrachloroaurate (III) trihydrate ($HAuCl_4{\cdot}3H_2O$) and DNA were first formed for the synthesis of gold nanoparticle using a DNA template, which were validated using UV-Vis spectroscopy. The morphology of complexes were also characterized by scanning electron microscopy (SEM). DNA-mediated gold nanoparticles were synthesized by the chemical reduction of DNA-Au(III) complexes using hydrazine ($N_2H_4$) and sodium borohydride ($NaBH_4$) as reducing agents. The effects of reducing agent types and their concentration on the formation of gold nanoparticles were investigated. The results showed that hydarazine was the most effective for the reduction of DNA-Au(III) complex. The DNA-mediated gold nanoparticles were characterized SEM, particle size analyzer (PSA), and transmission electron microscopy (TEM). Gold nanoparticles with 55~80 nm in diameter were formed by the aggregation of smaller gold nanoparticles (~nm), which was confirmed in the DNA matrix.

• Polymer(Korea)
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• v.31 no.5
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• pp.454-459
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• 2007

Gene therapy using low molecular weight water soluble chitosan (LMWSC) as polycationic polymer shows good biocompatibility, but low transfection efficiency. The mechanism of folic acid (FA) uptake in the cells to promote targeting and internalization could improve transfection rates. The objective of this study was to synthesize and characterize the WSCFA-DNA complex and evaluate their cytotoxicity, in vitro. In $^1H-NMR$ spectra, specific peaks appeared both of FA and LMWSC in $D_2O$. WSCFA nanoparticles have spherical shapes with particle size show below 110 nm. In the cell cytotoxicity test, the WSCFA-DNA complex showed high cell viability, in vitro. Gel electrophoresis showed condensed DNA within the carriers. hi vitro transfection efficiency was assayed by fluorescence spectroscopy WSCFA nanoparticles have less cytotoxicity, good DNA condensation and particle size around 110 nm, which makes them a promising candidate as a non-viral gene vector.

• Polymer(Korea)
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• v.36 no.4
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• pp.536-541
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• 2012

The effects of silica content were studied on UV curing characteristics and defect formations in imprinted patterns of hundreads nanometer size for the photo-curable imprinting composites with silica particles. An increase in elasticity and a decrease in shrinkage were observed with an increase in silica content in the imprinting resin which was UV cured at room temperature. However, the patterned nano-pillars were stuck together with neighboring nano-pillars if the amount of silica is more than 7 wt%. This can be ascribed to the increased viscosity of imperfectly cured resin due to the obstruction of the photo-reaction by silica particles. Addition of silica to the imprinting resin is useful in enhancing the strength of the cured resin although it is difficult to get good imprinted patterns for the resin with more than 7 wt% of silica due to the reduction of photo-reaction conversion.

• Applied Chemistry for Engineering
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• v.35 no.3
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• pp.260-265
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• 2024

To synthesize an antistatic material for use in semiconductor wafer transport trays, in-situ polymerization of poly(methyl methacrylate) (PMMA) and polyurethane (PU) incorporating carbon nanotubes was designed and conducted. The newly synthesized composites were evaluated for their thermal and electrical conductivity properties under conditions mimicking commercial device manufacturing processes. Comparative analysis of their respective performances revealed that both PMMA and PU containing carbon nanotubes exhibited enhanced thermal properties and superior electrical conductivity as the nanotube content increased. Morphology of the composites synthesized via in-situ polymerization was confirmed to be excellent through FE-SEM analysis, demonstrating good dispersibility. Both PMMA and PU incorporating carbon nanotubes showed outstanding surface resistance values of 10³ Ω/□, indicating their suitability as antistatic materials for semiconductor applications.