• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.2
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• pp.67-70
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• 2001

Nanosize $SiO_2$composite particles have been synthesized within reverse micelle via metal alkoxide hydrolysis and condensation. The size of the particles can be controlled by manipulating the relative rates of the hydrolysis and condensation reactions of tetraethoxysilane (TEOS) within the microemulsion. The average size of synthesized particles was about in the size range 14~30nm. The effects of synthesis parameters, such as the molar ratio of water to TEOS, the molar ratio of water to surfactant, and the amount of base catalyst, are discussed.

• Journal of Environmental Science International
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• v.12 no.4
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• pp.481-485
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• 2003

Two types of polyimide/silica composite films were prepared using sol-gel method through hydrolysis and polycondensation of tetraethoxysilane (TEOS) with the polyamic acid (PAA) and end-capped PAA solution. Samples were characterized by the means of differential thermogravimetry, X-ray diffractometry, scanning electron microscopy, universal test, impedance analyzer, chemical resistance test, etc. All of the PAA/silanol solutions heat-treated at 300$^{\circ}C$ for 6h were transformed to polyimide/silica composites. It has been demonstrated that the properties of polyimide/silica composites were affected by the amount of silica addition and the bend type existed between polyimide and silica.

• Carbon letters
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• v.7 no.3
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• pp.166-170
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• 2006

Silicon carbide whiskers ($SiC_w$) having the diameter in the range of 20-80 nm were synthesised from coconut fibres through sol-gel process. The coconut fibres were impregnated with tetraethoxysilane and methyltriethoxysilane derived sol and pyrolyzed at $1400^{\circ}C$ in argon. X-ray of the pyrolyzed samples showed the formation of ${\beta}$-SiC.

• Journal of the Korean Ceramic Society
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• v.42 no.2 s.273
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• pp.77-80
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• 2005

A series of proton conductive composite membranes based on poly(vinyl alcohol) and phosphosilicate gels powders were successfully prepared. The proton conductivity of these composite was attributed to the phosphosilicate gel, which derived from tetraethoxysilane and phosphoric acid by sol-gel process at a molar ratio of P/Si = 1.5. The proton conductivity increased with increasing both the content of phosphosilicate gel and relative humidity. Temperature dependence of conductivity showed a Vogel-Tamman-Fulcher type behavior, indicating that proton was transferred through a liquidlike phase formed in micropores of phosphosilicate gel. The high conductivity of 0.065 S/cm with a membrane containing 60 wt$\%$ of the gel was obtained at $60^{\circ}C$ at $90\%$ relative humidity.

• Journal of the Korean Society of Safety
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• v.13 no.1
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• pp.85-91
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• 1998

Sol-gel derived silica films were prepared by dip-coating onto polymethylmethacylate with Tetraethoxysilane(TEOS) as starting materials. Film properties such as viscosity and thickness were investigated as a function of dip speed, waterprecursor ratio, sol aging time. IR spectra of the gel films prepared from TEOS at various R are given. At small values of R the absorption peaks assignable to C-H vibration in $-OC_2H_5$ groups are observed around 3000 and 1500-1300 $cm^{-1}$. These bands indicate that the -$-OC_2H_5$ groups are retained in the gel at small values of R because of incomplete hydrolysis of TEOS. Film behaviour was interpreted in terms of the dependence of hydrolysis and condensation rates on the interplay between sol pH and waterprecursor ratio. Film thickness was found to increase by approximately a factor of two as waterprecursor ratio increased from two to six. Film thickness also increased with sol prepolymerization time. Surface quality was correlated with processing conditions.

• Macromolecular Research
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• v.16 no.5
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• pp.399-403
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• 2008

Monodisperse, micron-sized, hybrid particles having a core-shell structure were prepared by coating the surface of poly(methyl methacrylate)(PMMA) microspheres with silica and by copolymerizing acrylamide (AAm) to supply the hydrogen bonding effect by means of the amide groups. Tetraethoxysilane (TEOS) was then slowly dropped onto the medium under certain conditions. Because of the hydrogen bonding between the amide of the PMMA particles and the hydroxyl group of the hydrolyzed silanol, a silica shell was generated on the PMMA core particles. The morphology of the hybrid particles was investigated with transmission (TEM) and scanning (SEM) electron microscopy as a function of the medium conditions and the amount of TEOS. Improved thermal properties were observed by TGA analysis.

• Journal of the Korean Applied Science and Technology
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• v.28 no.2
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• pp.240-246
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• 2011

UV-Curable hybrid coatings were synthesized to improve the surface properties of plastic film. Organic-inorganic coating solutions were prepared by the sol-gel method using urethane-acrylate oligomer, acrylate monomer, photo initiator and tetraethoxysilane (TEOS). Methacryloyloxypropyltrimethoxysilane(MPTMS) was used as a silane coupling agent to improve chemical interaction between inorganic phases and UV curable acrylate. In this study, the surface hardness and adhesive properties were improved with the use of inorganic component. The experimental results showed that UV-Curable hybrid films containing aliphatic urethane oligomer, hexanedioldiacrylate, trimethylolpropanetriacrylate, hydroxy dimethyl acetophenone exhibited good surface properties. Also, the optimum curing conditions were investigated.

• Macromolecular Research
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• v.13 no.4
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• pp.321-326
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• 2005

Photochromic diarylethene polymers (DPs) in which 1,2-bis(2-methylbenzo[b ]thiophene-3-yl)hexafluorocyclopentene (BTF6) were covalently grafted onto the polymer main chain as pendant photochromic units were newly synthesized and their photochromic properties were investigated using steady-state and picosecond timeresolved spectroscopies. Polysiloxanes substituted with BTF6 molecules were prepared by sol-gel process using a mixture of tetraethoxysilane (TEOS), a silylated BTF6, and an organically modified silane precursor in the presence of HCl. The polysiloxane film (DP1) prepared from $\omega-methoxy$ poly(ethylene glycol) 3-(triethoxysilyl) propylcarbainate (MPGSC) as the silane precursor showed a much lower glass transition temperature than that (DP2) from heptadecafluorodecyltrimethoxysilane (HDFTMS). The ring-closure quantum yields of DP1 and DP2 were determined to be 0.20 and 0.02, respectively. Such a large difference in the quantum yield was attributed to the polymer matrix environment of the free inner volume.

• Proceedings of the KAIS Fall Conference
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• 2004.06a
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• pp.96-99
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• 2004

A new proton conductive inorganic-organic hybrid membrane doped with $H_3PO_4$ was fabricated via sol-gel process wit 3- glycidoxypropyltrimethoxysilane(GPTMS), 3-aminopropyltriethoxysilane(APTES) and tetraethoxysilane(TEOS) asprecursors. Theproto conductivity of about 3.0$\times10^{-3}S/cm$ was obtained at $120^{\circ}C$ under $50\%$ relative humidity (R.H). DTA curves showed that the thermal stability of the membrane is significantly enhanced by the presence of $SiO_2$ framework up to $250^{\circ}C$. SEM and XRD revealed that the gel is microporou and amorphous. The addition of APTES improved the conductivity of the membranes and the effect of the APTES on the conductivity was also discussed in this paper.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.159-159
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• 2007

In order to reduce a signal delay in ULSI, low resistive metal and intermetal dielectric material of low dielectric constant are required. Ordered mesoporous silica film is proper to intermetal dielectric due to its low dielectric constant and superior mechanical properties. In this study, ordered mesoporous silica films was synthesized using TEOS (tetraethoxysilane) / MTES (methyltriethoxysilane) mixed silica precursor and Brij-$76^{(R)}$ surfactant. These films had the porosity of 40% and dielectric constant of 2.5. To lower dielectric constant, the ordered mesoporous silica films were surface-modified by HMDS (hexamethyldisilazane) treatment. HMDS substituted -OH groups on the surface of silica wall for -Si$(CH_3)_3$ groups. After the HMDS treatment, ordered mesoporous silica films were calcined at various calcination temperatures. Through the investigation, it was concluded that the proper calcination temperature is necessary as aspects of structural, electrical, and mechanical properties.