• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05b
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• pp.33-36
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• 2005

Colloidal Silica(CS)/silane sol solutions were prepared in variation with synthesizing parameters such as ratio of CS to silane and reaction time. In the case of LHSA CS/tetramethoxysilane(TMOS)/methyltrimethoxysilane(MTMS) CS/silane sol, coating film had stable contact angle with increasing reaction time excepting for 48hours. Also, the LHSA CS/TMOS/MTMS coating film had more enhanced flat surface with increasing the amount of MTMS and increasing reaction time. In the case of thermal stability, thermal dissociation of LHSA CS/MTMS sol did not occur up to $550^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.230-231
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• 2006

We synthesized sol according to kinds(particle size/stabilized ion) of colloidal silica(CS), content ratio of alkoxysilane versus CS and reaction degree in sol solution and studied the surface property of coated gel materials. The contact angle of the thin films prepared from LHSA/N1030 CS/tetramethoxysilane(TMOS)/methyltrimethoxysilane(MTMS) sol-gel reaction system showed a little good relationship with content ratio of TMOS/MTMS silanes. The surface roughness of LHSA CS/TMOS/MTMS reaction system showed flatter than that of LHSA/N1030 CS. The thermal degradation of LHSA CS/TMOS/MTMS coating flim occurred at $550^{\circ}C$.

• Macromolecular Research
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• v.10 no.3
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• pp.174-177
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• 2002

Proton-conducting hybrid materials composed of silica and Nafion polymer were prepared from the sol-gel synthesis of silica in aqueous Nafion solution. The compositions of hybrid proton conductors were adjusted with the changing ratios of tetraethyl orthosilicate to Nafion. The thermal analysis, FTIR, SEM, and X-ray diffraction studies have proved the formation of Nafion/silica hybrid materials and no remarkable phase separation was observed, which led to an assumption that the macromolecular chain of silica and Nafion was homogeneously interlaned.

• Journal of the Korean Ceramic Society
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• v.39 no.11
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• pp.1063-1068
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• 2002

Polyimide/silica(PI/silica) hybrid materials having physical or chemical bonds between the PI and silica network were prepared using sol-gel process through hydrolysis and polycondensation of tetraethoxysilane with the polyamic Acid(PAA) or end-capped PAA solution. PAA solution was synthesized by ring opening reaction of pyromellitic dianhydride and oxydianiline monomers in dimethyl acetamide solution. End-capped PAA solution was synthesized by the addition of 3-aminopropyltriethoxysilane in PAA solution. PI/silica hybrid samples were characterized by infrared spectroscopy, differential thermogravimetry, X-ray diffractometry, scanning electron microscopy, and tensile tester. It has been demonstrated that the properties of hybrid samples were affected by the silica content and the bond type between PI and silica.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.1
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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.

• Journal of the Korean Applied Science and Technology
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• v.28 no.2
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• pp.185-195
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• 2011

Carbon nanotube(CNT) plays an essential role in various fields of nano based science and technology. Recently, silica coated CNT composites are interested because they are useful for the optical, magnetical, and catalytic applications. In this report, carboxyl groups were introduced on the MWCNT using nitric acid. In order to maximize the silica encapsulation efficiency, carboxyl groups of MWCNT reacted with a silane coupling agent were used to prepare silica coated MWCNT. Due to their strong interaction between modified MWCNT and TEOS. Silica layer with a controllable thickness was achieved. Silica coated MWCNT were further utilized as the template for the synthesis of hollow silica nanotubes after $800^{\circ}C$ calcination.

• Journal of Ceramic Processing Research
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• v.20 no.1
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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.

• Korean Chemical Engineering Research
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• v.51 no.5
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• pp.622-627
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• 2013

Colloidal silica is used in various industrial products such as chemical mechanical polishing slurry for planarization of silicon and sapphire wafer, organic-inorganic hybrid coatings, binder of investment casting, etc. An accurate determination of particle size and dispersion stability of silica sol is demanded because it has a strong influence on surface of wafer, film of coatings or bulks having mechanical, chemical and optical properties. The study herein is discussed on the effect of measurement results of average particle size, sol viscosity and electrophoretic mobility of particle according to the volume fraction of eight types of silica sol with different size and surface properties of silica particles which are presented by the manufacturer. The measured particle size and the mobility of these sol were changed by volume fraction or particle size due to highly active surface of silica particle and change of concentration of counter ion by dilution of silica sol. While in case the measured sizes of small particles less than 60 nm are increased with increasing volume fraction, the measured sizes of larger particles than 60 nm are slightly decreased. The mobility of small particle such as 12 nm are decreased with increase of viscosity. However, the mobility of 100 nm particles under 0.048 volume fraction are increased with increasing volume fraction and then decreased over higher volume fraction.

• 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.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.505-505
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• 2011

The control of wettability of thin films is of great importance and its success surely brings us huge applications such as self-cleaning, antifogging and bio-passive treatments. Usually, the control is accomplished by modifying either surface energy or surface topography of films. In general, hydrophobic surface can be produced by coating low surface energy materials such as fluoropolymer or by increasing surface roughness. In contrast, to enhance the hydrophillicity of solid surfaces, high surface energy and smoothness are required. Silica (SiO2) is environmentally safe, harmless to human body and excellently inert to most chemicals. Also its chemical composition is made up of the most abundant elements on the earth's crest, which means that SiO2 is inherently economical in synthesis. Moreover, modification in chemistry of SiO2 into various inorganic-organic hybrid materials and synthesis of films are easily undertaken with the sol-gel process. The contact angle of water on a flat silica surface on which the Young's equation operates shows ~50o. This is a slightly hydrophilic surface. Many attempts have been made to enhance hydrophilicity of silica surfaces. In recent years, superhydrophilic and antireflective coatings of silica were fabricated from silica nanoparticles and polyelectrolytes via a layer-by-layer assembly and postcalcination treatment. This coating layer has a high transmittance value of 97.1% and a short water spread time to flat of <0.5 s, indicating that both antireflective and superhydrophilic functions were realized on the silica surfaces. In this study, we assessed hydrophillicity and hydrophobicity of silica coating layers that were synthesized using the sol-gel process. Systematic changes of processing parameters greatly influence their surface properties.