• Applied Chemistry for Engineering
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• v.25 no.3
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• pp.286-291
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• 2014

In this study, nanosized TPA-silicalite-1 was synthesized with a suitable molar composition of TPAOH: $SiO_2$: $H_2O$ for the development of zeolite ceramic membranes to utilize as gas separation. As silica sources, TEOS, LUDOX AS-40 and CAB-O-SIL were used with the starting material of TPAOH. $NaH_2PO_4$, and a variety of acids and bases were used as promoters after TPAOH, $SiO_2$, $H_2O$ gel synthesis. To decrease synthesis time, a two step temperature change method was applied to the synthesis of TPA-silicalite-1 at a low temperature. TPA-silicalite-1 synthesized was analyzed with XRD, SEM, BET and TGA. As a result, TPA-silicalite-1 powders with a particle size of 100 nm and a specific surface area of $416m^2/g$ were obtained as optimum synthesis conditions when the two stage temperature change method was used with $NaH_2PO_4$ as promoter.

• Journal of the Korean Ceramic Society
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• v.26 no.4
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• pp.471-478
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• 1989

In this study we investigated the gelation time of sol which containing mixtures of TEOS with H2O, ethanol, HCl in the preparation of monolithic silica glass through Sol-Gel method. In this case apparent activation energies were observed by Arrhenius equation. We investigated the conversion from gel to glass in drying and heat treatment stages using DT-TG, FT-IR, XRD analysis and dried gel conversed to glass by heat treatment up to 85$0^{\circ}C$. The results of this experiment showed that the gelation time of solutions were promoted when increasing the amount of addition of H2O and HCl catalyst for TEOS and high reaction temperature of solution.

• Applied Chemistry for Engineering
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• v.7 no.5
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• pp.823-831
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• 1996

At the ratio [$H_2O$]/[TEOS]=1.7, the silica sol was synthesized by partial hydrolysis in the presence of acid catalyst. After stabilizing the silica sol by trimethylsilylation, the molecular weight and viscosity of the sol obtained at various reaction times were examined to determine a best spinnability of the sol. Gel fibers were prepared from the sol solution after removing solvent in the solution, and the gel fibers were heated at $1,000^{\circ}C$. The prepared silica fibers were in the shape of circular cross-section and their tensile strength and $SiO_2$ purity were $83{\pm}20kg/mm^2$ and about 99.997%, respectively.

• Journal of the Korean Ceramic Society
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• v.29 no.5
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• pp.357-366
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• 1992

Residual organics were considered as impurity in Sol-Gel method. The purpose of this study was to find the conditions to contain as much residual organics as possible in silica gel prepared from TEOS(tetraethylortho-silicate) by Sol-Gel method. Residual organics are to be expected to have reduction effect on synthesizing Si3N4 from silica gel. The results of this study are follows: 1) The maximum content of entrapped carbon was 19.8 wt.%(C/SiO2=0.25 wt.ratio) in silica gel synthesized under the conditions 1.5 fold mole water for incomplete hydrolysis, 2.5 fold mole phenol as a solvent and 0.1 fold mole HCl as a catalyst to TEOS. 2) Silica gel with organics entrapped by Sol-Gel method had a positive effect on the formation of Si3N4 compared with commercial silica gel. 3) Sintered body of synthesized $\alpha$-Si3N4 with Y2O3 and Al2O3 as additives at 175$0^{\circ}C$ in N2 atmosphere showed bending strength, 602$\pm$20 MPa and frature toughness 4.45$\pm$0.15 MPa.m1/2.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.68-69
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• 2005

BTO ($BaTiO_3$) thin film is one of the high dielectric materials for high-density dynamic random access memories (DRAMs) due to its relatively high dielectric constant. It is generally known that BTO film is difficult to be etched by plasma etching, but high etch rate with good selectivity to pattern mask was required. The problem of sidewall angle also still remained to be solved in plasma etching of BTO thin film. In this study, we first examined the patterning possibility of BTO film by chemical mechanical polishing (CMP) process instead of plasma etching. The sputtered BTO film on TEOS film as a stopper layer was polished by CMP process with the self-developed $BaTiO_3$- and $TiO_2$-mixed abrasives slurries (MAS), respectively. The removal rate of BTO thin film using the$ BaTiO_3$-mixed abrasive slurry ($BaTiO_3$-MAS) was higher than that using the $TiO_2$-mixed abrasive slurry ($TiO_2$-MAS) in the same concentrations. The maximum removal rate of BTO thin film was 848 nm/min with an addition of $BaTiO_3$ abrasive at the concentration of 3 wt%. The sufficient within-wafer non-uniformity (WIWNU%)below 5% was obtained in each abrasive at all concentrations. The surface morphology of polished BTO thin film was investigated by atomic force microscopy (AFM).

• Korean Journal of Optics and Photonics
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• v.6 no.3
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• pp.233-238
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• 1995

'#65279;We made $P_2O_5-SiO_2$ films on silicon for integrated optics application by low pressure chemical vapor deposition using TEOS(tetraethylorthosilicate), TMPite(trimethylphosphite) and phosphine($PH_3$). And We studied and compared between TMPite and PH, as a dopant of P in PSG films in the aspect of the de,position characteristics. Deposition rate of TMPate-PSG films was $55 \AA/min$ which was smaller than 90 A/min , that of $PH_3-PSG$ films. Thickness deviation of TMPate-PSG films was 2% and that of PH3-PSG was 4.5%. So TMPate-PSG films had a good quality in thickness uniformity. The range of refractive index was controlled from 1.445 to 1.468 at 633 nm in TMPate-PSG films and it was controlled from 1.456 to 1.476 in $PH_3-PSG$ films.

• Membrane and Water Treatment
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• v.14 no.2
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• pp.85-93
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• 2023

Membrane separation is widely used for several applications such as water treatment, membrane reactors and climate change. Cross-linked organic-inorganic hybrid polyvinylidene fluoride (PVDF) / Tetraethyl orthosilicate (TEOS) was adopted for the preparation of optimized hollow membrane (HFM) for membrane distillation or other low pressure separators for mechanical properties and permeability under varying pretreatment schemes. HFMs were prepared on semi-pilot membrane fabrication system. Novel adopted post-treatment schemes involved soaking in glycerol, magnesium sulphate (MgSO₄), sodium hypochlorite (NaOCl), and isopropanol for different durations. All fibers were characterized for morphology using a scanning electron microscope (SEM), surface roughness using atomic force microscope (AFM), elemental composition by examining Energy Dispersive Spectroscopy (EDS), water contact angle (CA°) and porosity. The performance of the fibers was evaluated for pure water permeation flux (PWF). Post-treatment with MgSO₄ gave the highest both tensile modulus and flux. Assessment of properties and performance revealed comparable results with other organic-inorganic separators, HF or flat. In spite of few reported data on post treatment using MgSO₄ in presence of TEOS, this proves the potential of low cost treatment without negative impact on other membrane properties. The flux is also comparable with hypochlorite which manifests substantial precaution requirements in actual industrial use.The relatively high values of flux/bar for sample treated with TEOS, post treated with MgSO₄ and hypochlorite are 88 and 82 LMH/bar respectively.

• Advances in nano research
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• v.1 no.3
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• pp.159-169
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• 2013

A preparation method for gadolinium compound (GdC) nanoparticles coated with silica ($GdC/SiO_2$) is proposed. GdC nanoparticles were prepared with a homogeneous precipitation method at $80^{\circ}C$ using $1.0{\times}10^{-3}$ M $Gd(NO_3)_3$, 0.5 M urea and $0-3.0{\times}10^{-4}$ M ethylenediarinnetetraacetic acid disodium salt dihydrate (ETDA) in water. As a result of preparation at various EDTA concentrations, GdC nanoparticles with a size as small as $40.5{\pm}6.2$ nm, which were colloidally stable, were prepared at an EDTA concentration of $2.0{\times}10^{-4}$ M. Silica-coating of the GdC nanoparticles was performed by a St$\ddot{o}$ber method at $35^{\circ}C$ using $1.0-10.0{\times}10^{-3}$ M tetraethylorthosilicate (TEOS), 11 M $H_2O$ and $1.5{\times}10^{-3}$ M NaOH in ethanol in the presence of $1.0{\times}10^{-3}$ M GdC nanoparticles. Performance of preparation at various TEOS concentrations resulted in production of $GdC/SiO_2$ particles with an average size of $106.1{\pm}11.2$ nm at a TEOS concentration of $5.0{\times}10^{-3}$ M. The gadolinium (Gd) concentration of $1.0{\times}10^{-3}$ M in the as-prepared $GdC/SiO_2$ particle colloid solution was increased up to a Gd concentration of 0.2 M by concentrating with centrifugation. The core-shell structure of $GdC/SiO_2$ particles was undamaged, and the colloid solution was still colloidally stable, even after the concentrating process. The concentrated $GdC/SiO_2$ colloid solution showed images of X-ray and magnetic resonance with contrast as high as commercial Gd complex contrast agents.

• Journal of the Korean Ceramic Society
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• v.29 no.9
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• pp.719-728
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• 1992

ZrO2/Al2O3-Mullite composites were prepared by infiltration of the silica sol to the porous ZrO2/Al2O3 bodies. The porous ZrO2/Al2O3 bodies for infiltration were fabricated using ZrO2 (20wt%)/Al2O3 composite powders synthesized by the emulsion-hot kerosene drying method. The preparation of silica sols was conducted by the hydrolysis-peptization of an alcoholic TEOS solution. When ZrO2/Al2O3-Mullite and ZrO2/Al2O3 composites were sintered at 1$650^{\circ}C$ for 4 hrs, both of them showed an excellent sinterability. As the amount of mullite added in the composites increased, the ratio of the tetragonal phase of zirconia to the monoclinic phase at the room temperature became higher. It was known that values of the fracture toughness of the ZrO2/Al2O3-Mullite composites were about 5.48 MPa.m1/2 much larger than that of the ZrO2/Al2O3 system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.319-320
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• 2008

본 연구에서는 대기압하에서 고품질의 산화막 증착을 목적으로 TEOS(Tetraethyl Orthosilicate)를 이용하여 APCVD법(Atmospheric Pressure CVD)으로 실리콘 산화막을 증착하고 하였으며, 특성 비교를 위하여 ICP-CVD를 이용하여 $SiH_4$ 와 $N_2O$ source gas를 이용하여 산화막을 증착하였다. 트랜지스터 제작후 Semiconductor measurement system을 이용하여 TFT의 전기적 특성을 측정 하였으며, 결과적으로 유기 사일렌을 사용한 경우 보다 우수한 전기적 특성을 확인할 수 있었다.