• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.292-299
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• 2012

We made 8 wt% silica dispersion system with fumed silica and photo curable acrylic monomer by beads mill process. These dispersions could be applied in organic/inorganic hybrid coating systems. These dispersions could be applied in organic/inorganic hybrid coating systems. The 4 species of photo curable acrylic monomer which was presence of hydroxyl group, different solubility parameter, and different molecular size were used in the silica dispersions. Stability of polar solvent, isopropyl alcohol, in silica dispersions was investigated. We investigated the stability of silica dispersions by using steady-state and dynamic rheology. As the monomer has hydroxyl group increased in mono and binary monomer silica dispersions, they showed non flocculated stable sol (loss modulus (G")> storage modulus (G')). When polar solvent IPA was added into slightly flocculated silica dispersions, they changed to non flocculated stable sol.

• Journal of Adhesion and Interface
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• v.23 no.3
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• pp.94-99
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• 2022

Ternary phased graphene/silica/EVOH nanocomposite coating materials were prepared via sol-gel process and solution blending process. From both SEM observations and XRD analysis, the exfoliated structure and dispersion state of graphene nanosheets and silica particles in the nanocomposites as well as the intercalated and exfoliated structure of the prepared graphene oxide were confirmed. The incorporation of GrO and silica at appropriate content resulted in remarkable improvement in oxygen barrier property of the ternary phased nanocompoiste-coated BOPP films, compared with that of binary(silica/EVOH) phased nanocomposite coating films, however, at excess amount of GrO and silica, very slight variation was observed due to incomplete exfoliation, dispersion of graphene tactoids, and formation of micro cracks in the silica clusters. In addition, the transparency of nanocomposite-coated film was investigated by measuring the light transmittance as a function of GrO contents, suggesting the possibility for the application of food packaging films.

• Journal of the Korean Applied Science and Technology
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• v.27 no.3
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• pp.282-289
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• 2010

In preparation of silica aerogel-based hybrid coating materials, the combination of hydrophobic aerogel with organic polar binder material is shown to be very limited due to dissimilar surface property between two materials. Accordingly, the surface modification of the aerogel would be required to obtain compatibilized hybrid coating sols with homogeneous dispersion. In this study, the surface of silica aerogel particles was modified by using both surfactant adsorption and heat treatment methods. Four types of surfactants with different molecular weights and HLB values were used to examine the effect of chain length and hydrophilicity. The surface property of the modified aerogel was evaluated in terms of visible observation for aerogel dispersion in water, water contact angle measurement, and FT-IR analysis. In surface modification using surfactants, the effects of surfactant type and content, and mixing time as process parameter on the degree of hydrophilicity for the modified aerogel. In addition, the temperature condition in modification process via heat treatment was revealed to be significant factor to prepare aerogel with highly hydrophilic property.

• Journal of Adhesion and Interface
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• v.13 no.4
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• pp.151-155
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• 2012

In the present study, we synthesized mesoporous silica hollow spheres with different wall thickness using polystyrene (PS) spheres as a structure template, tetraethoxysilane (TEOS) as a silica source, cetyltrimethylammonium bromide (CTAB) as a template. Particle size and dispersion of PS spheres were strongly depended on the concentration of surfactant in the aqueous solutions. The size of PS spheres was increased with decreasing concentration of surfactants. Dispersion of PS particle was improved when the surfactant concentration was lower than 0.5 g of surfactant.

• Corrosion Science and Technology
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• v.22 no.2
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• pp.99-107
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• 2023

Layered silicate clay montmorillonite (MMT) has been used in nanocomposite coating to improve corrosion protection by reinforcing the barrier property. The better dispersion of MMT in the coating produces a higher barrier effect. Pretreatment with MMT could favor the delamination of clay platelets, facilitating MMT dispersion in the coating. In the present work, a montmorillonite/silica (MMT/Si) composite was prepared by the in situ sol-gel method. x-ray diffraction measurements and field-emission scanning electron microscopy observations showed silica crystal formation and increased basal spacing between the MMT platelets. Composite MMT/Si particles were introduced in an epoxy resin to reinforce the corrosion protection of the coating applied on the AA2024 surface. Electrochemical impedance spectroscopy (EIS) was performed to characterize the protective property of the coating. The results demonstrated the high barrier effect of the coating containing 5 wt% of MMT/Si. Adhesion evaluation after a salt spray test exhibited a high adherence to the epoxy coating containing MMT/Si.

• Macromolecular Research
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• v.9 no.2
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• pp.92-99
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• 2001

Silica-filled rubber compounds have slower cure characteristics than carbon black-filled ones due to the adsorption of curatives on the silica surface. Fatty acid was used as a cure activator along with zinc oxide in a sulfur cure system. Poly(ethylene glycol), PEG, was used in silica-filled rubber compounds to prevent adsorption of the curatives on the silica surface. In this study, influence of the size of fatty acid and PEG on properties of silica-filled NR compounds was investigated. It was found that the size of fatty acid and PEG affected the curt: characteristics and physical properties. The cure rate becomes faster as the PEG size increases. By increasing the size of fatty acid or PEG, the delta torque of the compound decreases while the Mooney viscosity increases. The modulus of the vulcanizate decreases with increasing the molecular weight of fatty acid or PEG. The experimental results were explained by the filler dispersion and by the prevention of the curative-adsorption on the silica surface.

• Transactions on Electrical and Electronic Materials
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• v.12 no.3
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• pp.98-101
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• 2011

A 10 nm nano-silica was introduced to a conventional 3 ${\mu}M$ micro-silica composite to develop an eco-friendly new electric insulation material for heavy electric equipment. Thermal and mechanical properties, such as glass transition temperature (Tg), dynamic mechanical analysis, tensile and flexural strength, were studied. The mechanical results were estimated by comparing scale and shape parameters in Weibull statistical analysis. The thermal and mechanical properties of conventional epoxy/micro-silica composite were improved by the addition of nano-silica. This was due to the increment of the compaction via the even dispersion of the nano-silica among the micro-silica particles.

• Elastomers and Composites
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• v.52 no.4
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• pp.242-248
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• 2017

Wet masterbatch (WMB) technology is studied to develop high-content and highly disperse silica-filled compounds. This technology refers to the solidification of surface-modified silica with a rubber solution or latex. Until now, researchs based on styrene butadiene rubber (SBR)/silica WMB has been mainly performed. However, the blending of SBR/silica WMB and BR is not known and is currently under research and development. Therefore, in this study, the BR blending method suitable for emulsion (ESBR)/silica WMB is investigated by measuring their cure characteristics and the mechanical and dynamic viscoelastic properties. As a result, it was confirmed that the blending of ESBR/silica WMB and BR/silica dry masterbatch is most appropriate. However, it showed a disadvantage compared with the conventional mixing method, which was due to the surfactant remained and the sulfuric acid used as the coagulant.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.3
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• pp.272-277
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• 2004

The primary aim of this study is to investigate new semi-abrasive free slurry including acid colloidal silica and hydrogen peroxide for copper chemical-mechanical planarization (CMP). In general, slurry for copper CMP consists of colloidal silica as an abrasive, organic acid as a complex-forming agent, hydrogen peroxide as an oxidizing agent, a film forming agent, a pH control agent and several additives. We developed new semi-abrasive free slurry (SAFS) including below 0.5％ acid colloidal silica. We evaluated additives as stabilizers for hydrogen peroxide as well as accelerators in tantalum nitride CMP process. We also estimated dispersion stability and Zeta potential of the acid colloidal silica with additives. The extent of enhancement in tantalum nitride CMP was verified through anelectrochemical test. This approach may be useful for the application of single and first step copper CMP slurry with one package system.

• Transactions on Electrical and Electronic Materials
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• v.14 no.2
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• pp.101-104
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• 2013

The effect of the mixing ratio of spherical silica on the electrical insulation breakdown strength in an epoxy/silica composite was studied. Spherical silicas with two average particle sizes of $5{\mu}m$ and $20{\mu}m$ were mixed in different mixing ratios, and their total filling content was fixed at 60 wt%. In order to observe the dispersion of the silicas and the interfacial morphology between silica and epoxy matrix, scanning electron microscopy (SEM) was used. The electrical insulation breakdown strength was estimated in sphere-sphere electrodes with different insulation thicknesses of 1, 2, and 3 mm. Electrical insulation breakdown strength decreased with increasing mixing ratio of $5/20{\mu}m$ and the thickness dependence of the breakdown strength was also observed.