• Bulletin of the Korean Chemical Society
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• 제18권8호
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• pp.886-889
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• 1997

The crystal structure and optical properties of copper nanoparticles, prepared in fused silica by ion-implantation and subsequent heat-treatment, were characterized by X-ray, TEM, linear absorption, and degenerate four-wave mixing (DFWM) technique. The X-ray data show fcc lattice structure of the nanocrystals and their size was measured as 8-20 nanometer by high resolution TEM. Using DFWM, the third-order nonlinear optical coefficient of the Cu-SiO2 thin films was measured as 0.4-1.1×10-8 esu in the surface plasmon resonance absorption region (540-570 nm).

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.165-165
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• 2013

Nickel oxide was deposited on mesoporous silica by atomic layer deposition (ALD) consisting of sequential exposures to Ni(cp)2 and $H_2O$. NiO/silica samples were characterized by inductively coupled plasma-mass spectroscopy (ICP-MS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), etc. The flow-type reactor was used to measure activity of NiO/silica catalyst for catalytic combustion of toluene. The activity of NiO/silica catalyst was evaluated in terms of toluene removal efficiency and selectivity to $CO_2$ and compared with those of bare nickel oxide nanoparticles. In order to investigate influence of reaction temperature on combustion aspect, the catalytic combustion experiments were carried out at various temperatures. We show that both bare and supported NiO can be efficient catalysts for total oxidation of toluene at a temperature as low as $250^{\circ}C$.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.77.2-77.2
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• 2013

In this talk, I will briefly review recent results of my group related to application of atomic layer deposition (ALD) for fabricating environmental catalysts and organic solar cells. ALD was used for preparing thin films of TiO2 and NiO on mesporous silica with a mean pore size of 15 nm. Upon depositing TiO2 thin films of TiO2 using ALD, the mesoporous structure of the silica substrate was preserved to some extent. We show that efficiency for removing toluene by adsorption and catalytic oxidation is dependent of mean thickness of TiO2 deposited on silica, i.e., fine tuning of the thickness of thin film using ALD can be beneficial for preparing high-performing adsorbents and oxidation catalysts of volatile organic compound. NiO/silica system prepared by ALD was used for catalysts of chemical conversion of CO2. Here, NiO nanoparticles are well dispersed on silica and confiend in the pore, showing high catalytic activity and stability at 800oC for CO2 reforming of methane reaction. We also used ALD for surface modulation of buffer layers of organic solar cell. TiO2 and ZnO thin films were deposited on wet-chemically prepared ZnO ripple structures, and thin films with mean thickness of ~2 nm showed highest power conversion efficiency of organic solar cell. Moreover, performance of ALD-prepared organic solar cells were shown to be more stable than those without ALD. Thin films of oxides deposited on ZnO ripple buffer layer could heal defect sites of ZnO, which can act as recombination center of electrons and holes.

• Advances in nano research
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• 제13권1호
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• pp.97-111
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• 2022

In the present article, silica nanoparticles (SNPs) were exploited to improve the tribological and mechanical properties of vinyl ester/glass fiber composites. To the best of our knowledge, there hasn't been any prior study on the wear properties of glass fiber reinforced vinyl ester SiO₂ nanocomposites. The wear resistance is a critical concern in many industries which needs to be managed effectively to reduce high costs. To examine the influence of SNPs on the mechanical properties, seven different weight percentages of vinyl ester/nano-silica composites were initially fabricated. Afterward, based on the tensile testing results of the silica nanocomposites, four wt% of SNPs were selected to fabricate a ternary composite composed of vinyl ester/glass fiber/nano-silica using vacuum-assisted resin transfer molding. At the next stage, the tensile, three-point flexural, Charpy impact, and pin-on-disk wear tests were performed on the ternary composites. The fractured surfaces were analyzed by scanning electron microscopy (SEM) images after conducting previous tests. The most important and interesting result of this study was the development of a nanocomposite that exhibited a 52.2% decrease in the mean coefficient of friction (COF) by augmenting the SNPs, which is beneficial for the fabrication/repair of composite/steel energy pipelines as well as hydraulic and pneumatic pipe systems conveying abrasive materials. Moreover, the weight loss due to wearing the ternary composite containing one wt% of SNPs was significantly reduced by 70%. Such enhanced property of the fabricated nanocomposite may also be an important design factor for marine structures, bridges, and transportation of wind turbine blades.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.17-18
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• 2011

Plasma in liquid phase has attracted great attention in the last few years by the wide domain of applications in material processing, decomposition of organic and inorganic chemical compounds and sterilization of water. The plasma in liquid is characterized by three main regions which interact each - other during the plasma operation: the liquid phase, which supply the plasma gas phase with various chemical compounds and ions, the plasma in the gas phase at atmospheric pressure and the interface between these two regions. The most complex region, but extremely interesting from the fundamental, chemical and physical processes which occur here, is the boundary between the liquid phase and the plasma gas phase. In our laboratory, plasma in liquid which behaves as a glow discharge type, is generated by using a bipolar pulsed power supply, with variable pulse width, in the range of 0.5~10 ${\mu}s$ and 10 to 30 kHz repetition rate. Plasma in water and other different solutions was characterized by electrical and optical measurements. Strong emissions of OH and H radicals dominate the optical spectra. Generally water with 500 ${\mu}S/cm$ conductivity has a breakdown voltage around 2 kV, depending on the pulse width and the repetition rate of the power supply. The characteristics of the plasma initiated in ultrapure water between pairs of different materials used for electrodes (W and Ta) were investigated by the time-resolved optical emission and the broad-band absorption spectroscopy. The deexcitation processes of the reactive species formed in the water plasma depend on the electrode material, but have been independent on the polarity of the applied voltage pulses. Recently, Coherent anti-Stokes Raman Spectroscopy method was employed to investigate the chemistry in the liquid phase and at the interface between the gas and the liquid phases of the solution plasma system. The use of the solution plasma allows rapid fabrication of the metal nanoparticles without being necessary the addition of different reducing agents, because plasma in the liquid phase provides a reaction field with a highly excited energy radicals. We successfully synthesized gold nanoparticles using a glow discharge in aqueous solution. Nanoparticles with an average size of less than 10 nm were obtained using chlorauric acid solutions as the metal source. Carbon/Pt hybrid nanostructures have been obtained by treating carbon balls, synthesized in a CVD chamber, with hexachloro- platinum acid in a solution plasma system. The solution plasma was successfully used to remove the template remained after the mesoporous silica synthesis. Surface functionalization of the carbon structures and the silica surface with different chemical groups and nanoparticles, was also performed by processing these materials in the liquid plasma.

• Korean Chemical Engineering Research
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• 제53권1호
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• pp.78-82
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• 2015

유기주형(organic template) 입자를 이용하여 소디움실리케이트(sodium silicate)로부터 중공형 실리카(hollow silica) 입자를 제조하였다. 유기주형 입자로는 스티렌 단량체(styrene monomer)로부터 분산중합(dispersion polymerization)에 의해 제조된 폴리스티렌 라텍스(polystyrene latex, PSL) 입자를 사용하였다. 유기주형 입자 제조 시 중합개시제인 2,2'-azobisisobutyronitrile(AIBN)의 주입량을 조절하여 $1{\sim}3{\mu}m$의 크기를 가진 입자를 제조하였다. 생성된 유기주형 입자 표면에 졸-겔(sol-gel)법에 의해 소디움실리케이트로부터 생성된 실리카($SiO_2$) 나노 입자를 코팅하여 PSL/$SiO_2$ 코어-쉘 형태의 입자를 제조하였다. 유기용매인 테트라하이드로푸란(tetrahydrofuran, THF)을 이용하여 코어-쉘 입자 내부의 유기주형을 제거 하였다. 코어-쉘 입자 제조 시 용매의 종류 및 pH의 변화에 따라 생성되는 중공형 실리카 입자의 형상을 조사하였다. PSL/$SiO_2$ 코어-쉘 입자 제조 시 용매를 에탄올에서 물로 변경했을 때 중공형 실리카 입자가 성공적으로 제조되었으며 낮은 pH 값을 갖는 용매에서 쉘 두께가 균일한 중공형 실리카 입자가 형성되었다. 중공형 실리카 입자의 반사도를 측정한 결과 상용 제품(Insuladd)보다 높은 반사 특성을 보여주었다.

• 멤브레인
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• 제30권5호
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• pp.307-318
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• 2020

기존의 바나듐 레독스 흐름전지(vanadium redox flow battery, VRFB)에서 사용하고 있는 과불소계이오노머인 나피온(Nafion)은 전해질에 존재하는 바나듐 이온의 투과도가 높아, 바나듐 이온이 분리막을 투과하여 반대쪽 전해질로 교차 이동하는 문제를 갖고 있다. VRFB에서 바나듐 이온의 투과는 서로 다른 산화수를 갖는 바나듐 이온이 부반응을 일으켜 충전, 방전 용량의 감소를 야기하고, 장기적인 성능 감소를 일으키는 원인이 된다. 이러한 문제를 해결하기 위해 본 연구에서는 SiO₂에 3-aminopropyl group이 도입된 나노입자(fS)를 Nafion에 분산시켜 바나듐 이온의 투과를 감소시키고, VRFB의 장기적인 성능의 향상을 도모하고자 하였다. SiO₂에 붙어 있는 아민기(-NH₂)가 Nafion의 술폰산 음이온(SO₃^-)과 이온결합을 형성함과 동시에, 암모늄 양이온(-NH₃⁺)의 양전하가 바나듐 이온에 대해 Gibbs-Donnan 효과를 나타내어 낼 것이라고 기대하였다. fS를 섞은 Nafion 용액의 pH와 Nafion-fS 막의 IEC 측정을 통해 암모늄 양이온과 술폰산 음이온의 이온결합이 존재하는 것을 확인하였고, fS의 양이 많아질수록 바나듐 이온의 투과도가 감소하는 것을 확인하였다. VRFB 단위 전지에 제조한 복합막을 도입하였을 때, 150 mA/㎠의 전류밀도에서 충방전 사이클을 200회 반복 진행하여도 방전용량을 최대 80%까지 유지할 수 있었다.

• 폴리머
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• 제34권1호
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• pp.1-7
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• 2010

기체 분리막의 투과 특성을 향상시키기 위하여 불소계 폴리이미드(6FDA-6FpDA) 고분자 매트릭스에 실리카 나노입자를 첨가한 유기-실리카계 복합 소재 막을 제조하였다. 실리카 입자의 분산도를 높이기 위하여 먼저 $\gamma$-MPS를 이용한 표면처리 과정을 거친 후, 6FDA-6FpDA와 단일상을 이룰 수 있는 PMMA를 실리카 나노입자 표면에 도입하였다. PMMA-graft-silica와 비교해 보았을 때, 순수 실리카 입자의 경우 불규칙 분산성으로 인하여 투과도는 증가하나 기체에 대한 낮은 선택도를 가졌다. PMMA를 도입시킨 실리카 입자를 첨가한 복합막의 경우 실리카 입자의 함량에 따라 고분자 필름을 제조하여 He, $O_2$, $N_2$, $CO_2$의 기체투과도를 측정하였다. 실험 결과 실리카 입자의 함량이 높아 질수록 사슬 정렬 방해에 의한 자유 부피가 증가되어 투과도가 증가되나 1 wt% 이후에는 과량의 실리카 입자의 첨가로 인한 고분자 내의 유효면적 감소로 인해 투과도가 감소하는 결과를 보였다. 전체적으로 가스의 투과도 증가로 인해 선택도의 감소를 보였으나 이산화탄소의 경우 선택도의 증가를 보였으며 이는 실리카 나노입자와 고분자 매트릭스 사이의 상호 결합으로 인해 나타나는 크기 제어에 의한 선택도 향상이다.

• 한국방사선학회논문지
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• 제8권6호
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• pp.325-332
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• 2014

금속나노입자는 진단이나 치료를 포함한 의생명응용분야에 있어 매력적인 특징들을 갖고 있다. 양성자 빔 치료를 위한 방사선증감제로 사용하기 위해 가교덱스트란이 코팅된 산화철나노입자(SPIONs)와 실리카가 코팅된 산화가돌리늄나노입자(SPGONs)를 합성하였다. 덱스트란과 실리카는 각각 SPIONs와 SPGONs의 보호수단이다. 합성된 SPIONs와 SPGONs를 투과전자현미경(TEM)으로 분석한 결과 각각 평균 직경이 3~5 nm와 30~100 nm였다. 합성된 방사선 증감제의 효과를 평가하기 위해 세포생존곡선 측정과 Western blotting을 수행하였다. 측정된 세포생존곡선으로부터 계산된 90% 세포사멸 시 방사선증감비는 SPIONs와 SPGONs에 대하여 각각 1.23과 1.03이었다. Western blotting 결과 역시 Cytochrome C의 발현량이 SPIONs를 처리한 암세포에서 유의적으로 증가됨을 보였다.

• 한국분말재료학회지
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• 제18권6호
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• pp.532-537
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• 2011

Thermally stable $TiO_2$/Pt/$SiO_2$ core-shell nanocatalyst has been synthesized by chemical processes. Citrated capped Pt nanoparticles were deposited on amine functionalized silica produced by Stober process. Ultrathin layer of titania was coated on Pt/$SiO_2$ for preventing sintering of the metal nanoparticles at high temperatures. Thermal stability of the metal-oxide hybrid catalyst was demonstrated heating the sample up to $600^{\circ}C$ in air and by investigating the morphology and integrity of the structure by transmission electron spectroscopy. The surface analysis of the constituent elements was performed by X-ray photoemission spectroscopy. The catalytic activity of the hybrid catalysts was investigated by CO oxidation reaction with oxygen as a model reaction.