• 마이크로전자및패키징학회지
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• 제23권1호
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• pp.35-39
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• 2016

The flexible and superhydrophobic properties of silica aerogels are extremely important material for thermal insulation and oil spill cleanup applications for their long-term use. Flexible silica aerogels were synthesized by using a two-step sol-gel process with precursors, methyltrimethoxysilane (MTMS) followed by supercritical drying. Silica aerogels were prepared at different molar ratio of methanol to MTMS (M). It was observed that the silica aerogels prepared at M=28 were monolithic but inelastic in nature, however, for M=35, the obtained aerogels were monolithic, elastic in nature with less shrinkage. The microstructural studies were carried out using scanning electron microscopy and surface area measurements. The hydrophobicity was confirmed by Fourier transform Infrared spectroscopy and water contact angle measurements. The detailed insight mechanism for flexible nature of silica aerogels and hydrophobic behavior were studied.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.183-183
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• 2012

최근 환경오염과 천연자원의 고갈로 태양광을 이용한 수소와 산소를 제조하는 광전기화학적 물분해 반응이 많은 관심을 받고 있다. 본 연구에서는 란타늄 알루미네이트 단결정 기판 위에 니오븀을 도핑한 이산화 티타늄을 증착 시킨 후 two-step sol-gel법을 이용하여 아나타제 이산화티탄늄 나노막대를 성장시켰다. 성장시킨 아나타제 티타늄산화 막대는 구조적인 특징과 모양, 크기를 전구체 용액의 수소이온화지수(pH)를 조절함으로써 변화 시킬 수 있다. 니오븀을 도핑한 이산화 티타늄 기판 위에 높은 수소이온화지수(pH 10 이상)을 이용하여 우선 배향된 아나타제 나노 막대를 성장 시킬 수 있으며, 주사전자현고해상도 투과전자현미경, x선 회절 분석기를 통해 구조적 특성을 평가하였다. 또한 수소이온화지수를 조절(pH 9)하여 만든 다결정질 아나타제 나노구형과 우선배향된 나노막대의 전하이동특성을 분석하기 위하여 기체 색층분석법(GC), 광전기화학법(PEC), 임피던스를 측정하였다.

• 한국표면공학회지
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• 제41권4호
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• pp.169-173
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• 2008

The objective of this study is to coat the $SiO_2$ layer uniformly on the ZnS:Cu phosphors by using Sol-Gel method. From results of SEM micrographs observation, XRD and XPS analysis, it could be confirmed that $SiO_2$ layer was relatively well coated on ZnS:Cu particles. $Ag_2S$ was used as a decoding chemical to analyze the dense and uniform coating performance of $SiO_2$ layer on phosphor particles. It could be concluded that phosphors synthesized from our two step replacement method showed strong blue peak comparing to other method and rather weak green peak also. Obtained particle size of phosphors were about 20m diameter. Luminescence properties of the phosphors were examined by photoluminescence spectra at the excitation wavelength of 270 nm.

• Journal of Ceramic Processing Research
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• 제20권1호
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• pp.30-34
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• 2019

Copper (Cu)-incorporated silica aerogel was synthesized by a sol-gel process with two-step drying process for color modification. The microstructure of the silica aerogel was not affected significantly by the Cu concentration and an amorphous structure was maintained without any crystalline impurity phases. The textural properties of the silica aerogels investigated by using N2 adsorption-desorption isotherms exhibited the typical features of mesoporous materials. The pore size and porosity were not changed significantly even with the incorporation of Cu up to 1.5 M, which indicates negligible variation of thermal insulating properties. However, the color of the aerogel changed from white and light greenish to dark greenish with increasing Cu content. The color change of the silica aerogel was due to the modification of the electron energy band structure of silica by the Cu atomic levels. Therefore, the color of the silica aerogel powders could be manipulated by incorporating Cu without degrading the thermal insulating properties.

• Current Photovoltaic Research
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• 제3권1호
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• pp.5-9
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• 2015

Absorption and luminescence characteristics of disperse red-19 (DR-19) and $TiO_2$ composite have been investigated with various poling electric field strengths. Two step synthetic processes were employed to employ the DR-19 to the $TiO_2$ sol-gel. Firstly, urethane bond formation between DR-19 (-OH) and 3-isocyanatopropyl triethoxysilane (ICPTES, -N=C=O) performed (ICPDR) prior incorporation to the $TiO_2$ sol-gel. Secondary, the hydrolysis of the ethoxy group from the ICPTES and condensation reaction between silanol groups from ICPTES and $TiO_2$ sol-gel were performed. The ICPDR and $TiO_2$ sol-gel ($DRTiO_2$) were mixed and stirred for several days. The composite was coated to the ITO coated glass substrate. Corona poling were performed before drying the composite with various electric field strengths. The absorption intensity decreased with the increase of the poling field strength, which resulted in the increase of poling efficiency. The photoluminescence also decreased as the poling field strength increased. There is long luminescence tail for the poled $DRTiO_2$ film compared with unpoled $DRTiO_2$ film. The luminescence long tail indicates that the self-trapped excitons and polarons were generated when the $DRTiO_2$ film was poled with electric field.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.136-136
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• 2003

In fiber optic networks, system size and cost can be significantly reduced by development of optical components through planar optical waveguides. One important step to realize the compact optical devices is to develop planar optical amplifier to compensate the losses in splitter or other components. Planar amplifier provides optical gain in devices less than tens of centimeters long, as opposed to fiber amplifiers with lengths of typically tens of meters. To achieve the same amount of gain between the planar and fiber optical amplifier, much higher Er doping levels responsible for the gain than in the fiber amplifier are required due to the reduced path length. These doping must be done without the loss of homogeniety to minimize Er ion-ion interactions which reduce gain by co-operative upconversion. Sol-gel process has become a feasible method to allow the incorporation of Er ion concentrations higher than conventional glass melting methods. In this work, Er-doped $SiO_2$-A1$_2$ $O_3$ films were prepared by two different method via sol -Eel process. Tetraethylorthosilicate(TEOS)/aluminum secondary butoxide [Al (OC$_4$ $H_{9}$)$_3$], methacryloxypropylcnethoxysaane(MPTS)/aluminum secondary butofde [Al(OC$_4$ $H_{9}$)$_3$] systems were used as starting materials for hosting Er ions. Er-doped $SiO_2$-A1$_2$ $O_3$ films obtahed after heat-treating, coatings on Si substrate were characterized by X-ray din action, FT-IR, and N-IR fluorescence spectroscopy. The luminescence properties for two different processing procedure will be compared and discussed from peak intensity and life time.

• 한국세라믹학회지
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• 제55권6호
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• pp.562-569
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• 2018

We propose an economic and facile method for the preparation of silica nanoparticles through a two-step process utilizing chlorosilane residues. Mixed chlorosilane residue was alcoholized with absolute ethanol as a first step to form tetraethoxysilane (TEOS). The TEOS was then utilized as a silicon source to synthesize silica nanoparticles in a sol-gel method. The alcoholysis process was designed and optimized utilizing the Taguchi experimental design method and the yield of TEOS was as high as 82.2% under optimal synthetic conditions. Similarly, the Taguchi method was also utilized to study the effects of synthesis factors on the particle size of silica nanoparticles. The results of statistical analysis indicate that the concentration of ammonia has a greater influence on particle size compared to the mass fractions of TEOS and polyethylene glycol (4.6% and 9.7%). The purity of the silica particles synthesized in our experiments is high, but the specific surface area and pore volume are small.

• 센서학회지
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• 제16권6호
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• pp.395-400
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• 2007

Ambient drying sol-gel processing was used for monolithic silica ambigels in the temperature range of $130-250^{\circ}C$. A new method of mesopore ambigels, which mean the aerogels prepared by ambient pressure drying process synthesis, is suggested at first. This method includes two important approaches. The first point is that $SiO_{2}$ surface modification of wet gel was performed by trimethylchlorosilane in n-butanol solution. This procedure is provided the silica gel mesopore structure formation. The second point is a creation of the ternary azeotropic mixture water/n-butanol/octane as porous liquid, which is effectively provided removing of water such a low temperature by 2 step drying condition under ambient pressure. The silica aerogels, which were prepared by ambient pressure drying from azeotropic mixture of water/n-butanol/octane, are transparent, crack-free and mesoporous (pore size ${\sim}$ 5.6 nm) with surface area of ${\sim}$ $923{\;}m^2/g$, bulk density of $0.4{\;}g/cm^3$ and porosity of 85 %.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.202.1-202.1
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• 2013

ZnO nanostructure was fabricated on a Si substrate using two-step growth. The seed layer was grown on the Si substrate by a sol-gel spin-coating. In the first step, ZnO nanorods were grown by a hydrothermal method at $140^{\circ}C$ for 5 min. In the second step, a ZnO thin film was grown on the ZnO nanorods by spin-coating. After growth, these films were annealed at $800^{\circ}C$ for 10 min. Electrical and optical properties of ZnO nanostructures have modified by plasma-assisted molecular beam epitaxy (PA-MBE) regrowth. The carrier concentration and resistivity increased by PA-MBE regrowth. In the photoluminescence, the full width at half maximum and intensity were decreased and increased, respectively, by PA-MBE regrowth.

• 공업화학
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• 제17권4호
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• pp.420-425
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• 2006

Propylene oxide (PPO)를 gelation agent로 한 졸-겔법으로 입자가 균일하고 자기적 특성이 우수한 $MO{\cdot}Fe_{12}O_{18}$ (M/Ba and Sr)의 구조식을 가지는 M-type hexagonal ferrite를 제조하였다. 본 방법으로 얻은 졸-겔용액은 매우 안정적인 분산상태를 보이며, $Fe^{3+}$의 겔화가 진행되고, 생성된 $Fe_2O_3$의 표면에서 $Ba^{2+}$ 또는 $Sr^{2+}$의 겔화가 진행되는 것으로 설명될 수 있어서, +3가 이하의 금속이라도 +3가 이상의 금속 존재 하에는 겔화가 가능한 것을 확인하였다. 또한, 기존 방법과 비교하여 값싼 원료를 사용하며, 반응 시간도 1 min 이내로 짧아지는 장점이 있다. 본 제조법으로 얻어진 분말은 기왕에 발표된 문헌 값과 비교하면 $150^{\circ}C$ 이상 낮은 열처리 온도에서 최고의 자기적 특성을 나타냈으며, 향상된 자기적 특성을 보였다. Sr-ferrite의 경우 최대포화자화 값 74.4 emu/g, 보자력 값 6198 Oe을, Ba-ferrite의 경우도 최대포화자화 값 68.1 emu/g, 보자력 값 5155 Oe을 보였다. 이들은 기존에 발표된 문헌 값과 비교하면 각각 10%와 5% 이상 증가된 보자력 값을 나타내어, 고밀도 자기기록재료에 적합함을 확인하였다. 제조된 분말은 1차 건조 분말의 경우 3~5 nm의 입자들이 응집된 50 nm 정도의 구형입자가 생성되고, 열처리 후에는 500 nm 정도의 고른 크기를 가진 육각판상형 입자가 생성된다.