• 대한화학회지
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• 제56권4호
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• pp.478-483
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• 2012

We successfully synthesized $Fe_3O_4/SiO_2$ nanoparticles with ultrathin silica layer of $1.0{\pm}0.5$ nm that was fine controlled by changing concentration of $Fe_3O_4$. Among various reaction conditions for silica coating, increasing concentration of $Fe_3O_4$ was more effective approach to decrease silica thickness compared to water-to-surfactant ratio control. Moreover, we found that concentration of the 1-octanol is also important factor to produce the homogeneous $Fe_3O_4/SiO_2$ nanoparticles. The present approach could be available to apply on preparation of other core/shell nanoparticles with ultrathin silica layer.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.96-96
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• 2010

Monodispersed spherical silica-coated ceria nanoparticles were prepared through a sol-gel process using tetraethylorthosilicate (TEOS) and ceria fine particles. In this process, ceria fine particles were also prepared from cerium nitrate. The mean size of ceria particles was 300nm. Silica nanoparticles with narrow particle size distribution were prepared by controlled hydrolysis of TEOS solution. The silica sols were obtained by peptization, the process of redispersing a coagulated colloid, and were coated on ceria particles by the control of the weight ratio of silica/ceria and the pH of the mixture in aqueous solution. The morphologies of particles were characterized with scaning electron microscopy(SEM), transmission electron microscopy(TEM) and atomic force microscopy(AFM). The coating thickness of silica particles obtained by using this method was controlled in the range of 30 - 70nm.

• 한국결정학회지
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• 제8권2호
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• pp.89-96
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• 1997

본 연구는 fine ceramics의 합성법을 traditional ceramics의 합성에 적용하는 연구의 일환으로 내화재료용 mullite합성법을 개발하고자 한다. 출발원료로는 알루미나 함량이 높은 하동 kaolin 과 boehmite를 사용하였으며 합성법은 gel coating법을 사용하였다. 그 결과 1350℃에서 미반응 silica와 corundum이 존재하지 않는 단일상의 mullite를 합성할 수 있었으며 1700℃로 소성한 분말의 경우 mullite 생성율은 80%로 나타났다. 이 때 부피비중은 2.56, 흡수율은 1.9%, 상온꺽임강도는 169 MPa의 값을 나타내어 우수한 내화재료로의 활용이 가능하다고 생각된다.

• Corrosion Science and Technology
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• 제19권1호
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• pp.8-15
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• 2020

In this paper, the efficiency and the inhibition mechanisms of cobalt salts (cobalt nitrate and cobalt-exchange silica Co/Si) for the corrosion protection of AA2024 were investigated in a neutral aqueous solution by using the electrochemical impedance spectroscopy (EIS) and polarization curves. The experimental measurements suggest that cobalt cation plays a role as a cathodic inhibitor. The efficiency of cobalt cation was important at the concentration range from 0.001 to 0.01 M. The formation of precipitates of oxides/hydroxides of cobalt on the surface at low inhibitor concentration was confirmed by the Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy (SEM/EDS) analysis. EIS measurements were also conducted for the AA2024 surface covered by water-based epoxy coating comprising Co/Si salt. The results obtained from exposure in the electrolyte demonstrated the improvement of the barrier and inhibition properties of the coating exposed in the electrolyte solution for a lengthy time. The SEM/EDS analysis in artificial scribes of the coating after salt spray testing revealed the release of cobalt cations in the coating defect to induce the barrier layer on the exposed AA2024 substrate.

• Bulletin of the Korean Chemical Society
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• 제9권3호
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• pp.137-143
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• 1988

We have investigated the infrared spectra for carbon monoxide chemisorbed on silica supported ruthenium with and without potassium coating within the frequency range of 1800-2200 $cm^{-1}$ at various ruthenium concentrations and CO pressures. For the system without potassium coating, three bands were observed in the infrared spectra when CO was adsorbed on both the reduced and oxidized form of supported ruthenium. However, the relative intensities of these three bands were found to have no interdependence. Therefore, we have assigned each of these bands as arising from the CO stretching vibration for carbon monoxide molecules adsorbed on the Ru sites of different nature. On coating with potassium, the 2030 $cm^{-1}$ band observed for the system without potassium coating was found to suffer red shift by 10-30 $cm^{-1}$ and we conclude that this bathochromic shift is caused by enhancement in the capability of back donation of electrons from the metal atom to the antibonding ${\pi}{\ast}$ orbitals of CO due to the presence of potassium.

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2003년도 추계총회 및 연구발표회 초록집
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• pp.231.1-231
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• 2003

• Korean Chemical Engineering Research
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• 제54권2호
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• pp.163-170
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• 2016

고분자 필름의 친수성을 향상시키기 위하여 우수한 친수성을 보이는 코팅 용액을 졸-겔법으로 합성하였다. 코팅 용액은 입자 직경이 15 nm 크기의 콜로이드 실리카에 다양한 실란커플링제인 아미노실란, 에폭시실란과 아크릴실란을 각각 반응시켜 제조하였다. 콜로이드 실리카에 아미노실란을 첨가한 코팅 용액은 바로 겔화가 진행되어 코팅 용액을 제조할 수 없었다. 반면에 에폭시실란을 첨가한 코팅 용액은 실란커플링제/콜로이드 실리카의 질량분율(R값)이 0.10~0.15에서 접촉각 $10{\sim}15^{\circ}$의 우수한 친수성을 나타내었다. 또한 아크릴실란을 첨가한 코팅 용액은 R값이 0.03~0.07에서 $5{\sim}10^{\circ}$의 접촉각을 나타내어 아미노실란과 에폭시실란을 사용했을 때 보다 우수한 친수성을 나타내었다.

• 한국구조물진단유지관리공학회 논문집
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• 제17권4호
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• pp.84-90
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• 2013

본 논문은 기존 순환골재 생산공장에서 새로운 설비투자나 복잡한 처리공정을 거치지 않고 비교적 용이하게 순환골재의 품질을 개선할 수 있는 효과적인 코팅처리방법을 도출하고, 도출한 코팅처리방법으로 순환골재를 코팅처리하여 그 품질개선 효과를 확인하였다. 연구목적을 달성하기 위하여 순환골재를 코팅하기 위하여 코팅처리용액중 하나인 실리케이트 용액을 경제성 있게 알맞은 농도로 희석하여 사용하였으며, 골재의 코팅방법을 달리하여 12가지 종류의 코팅골재에 대한 물성평가를 실시하였다. 또한 가장 좋은 물성을 나타낸 코팅골재를 사용하여 콘크리트를 제조하였다. 이상의 실험결과 골재를 코팅처리용액에 함침 및 건조를 반복하였을 때 골재의 품질이 가장 우수하게 나타났고, 다른 코팅방법 또한 물성이 코팅처리 전 골재보다는 향상되는 것으로 나타났으나, KS 기준에는 미치는 못하는 결과를 나타내었다. 또한, 가장 좋은 물성을 나타낸 골재를 가지고 콘크리트를 제조한 결과 설계기준강도를 만족시키는 압축강도가 측정되었으며, 설계기준강도 24MPa 이하의 도로시설물을 축조할 때 활용이 가능할 것으로 판단된다.

• 한국세라믹학회지
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• 제56권1호
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• pp.98-103
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• 2019

Optical filters to control light wavelength of displays or cameras are fabricated by multi-layer stacking process of low and high index thin films. The process of multi-layer stacking of thin films has received much attention as an optimal process for effective manufacturing in the optical filter industry. However, multi-layer processing has disadvantages of complicated thin film process, and difficulty of precise control of film morphology and material selection, all of which are critical for transmittance and coloring effect on filters. In this study, the composite $TiO_2$, which can be used to control of UV absorption, coated on nano hollow silica sol, was synthesized as a coating material for optical filters. Furthermore, systematic analysis of the process parameters during the chemical reaction, and of the structural properties of the coating solutions was performed using SEM, TEM, XRD and photo spectrometry. From the structural analysis, we found that the 85 nm nano hollow silica with 2.5 nm $TiO_2$ shell formation was successfully synthesized at proper pH control and titanium butoxide content. Photo luminescence characteristics, excited by UV irradiation, show that stable absorption of 350 nm-light, correlated with a 3.54 eV band gap, existed for the $TiO_2$ shell-nano hollow silica reacted with 8.8 mole titanium butoxide solution. Transmittance observed on substrate of the $TiO_2$ shell-nano hollow silica showed effective absorption of 200-300 nm UV light without deterioration of visible light transparency.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
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• pp.1158-1161
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• 2006

The toner type paper-like display (PLD) has been developed with two polymer particles having opposite polarity which is composed of polymer, colorant and external additives (nano-sized silica). Nano-sized silica with triboelectric charge was used for the charge control agent (CCA) and influenced on the electrostatic properties of the silica-coated polymer particles. The PLD cell using silica-coated particles (200 seconds) had shown a good white appearance and low driving voltage. The result could be explained in terms of the surface morphology and the cohesiveness depending on the silica coating time.