• Corrosion Science and Technology
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• v.18 no.6
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• pp.232-242
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• 2019

In this study, hydrophobically modified fumed silica was added to the PVDF coating to improve corrosion protection performance. Two types of silane modifiers, trimethylchlorosilane (TMCS) and hexamethyldisilazane (HMDZ), were used for hydrophobic modification of the fumed silica. The composition of modified fumed silica was analyzed by Fourier transform infrared, X-ray photoelectron spectroscopy, and elemental analysis. The dispersion of modified fumed silica in the PVDF coating was observed by the transmission electron microscopy, and the hydrophobicity of PVDF coating was analyzed by the water contact angle. Surface properties were examined by the field emission scanning electron microscopy and scanning probe microscopy. Potentiodynamic polarization was conducted to confirm corrosion protection performance of PVDF coating in terms of hydrophobically-modified fumed silica contents. As a result, the average surface roughness and the water contact angle of the PVDF coating increased with modifier contents. The results of the potentiodynamic polarization test showed an increase of the E_corr values with increase of the hydrophobicity of PVDF coating. Thus, it clearly indicates that the corrosion protection performance of PVDF coating improved with the addition of the hydrophobic-modified fumed silica that prevents the penetration of moisture into the PVDF coating.

• Korean Chemical Engineering Research
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• v.55 no.6
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• pp.754-761
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• 2017

UV-curable hydrophilic coating solutions were prepared by mixing colloidal silica dispersed in alcohol with an acrylic monomer, pentaerythritol triacrylate (PETA). Hydrophilic coating films were also prepared by spin coating the hydrophilic coating solutions on PC substrates and UV curing for 10 minutes subsequently. The effect of the amount of colloidal silica in the coating solutions, which was varied from 10 g to 50 g, was investigated on the hydrophilic properties of UV-cured coating films. The results showed that the amount of colloidal silica had a great influence on the hydrophilic properties of UV-cured coating films and the coating film prepared with 30 g of colloidal silica showed a lowest contact angle of $37^{\circ}$ and an excellent pencil hardness of H.

• Journal of Dental Rehabilitation and Applied Science
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• v.29 no.1
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• pp.69-79
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• 2013

The aim of this study was to evaluate the effect of surface conditioning on the shear bond strength of zirconium-oxide ceramic to resin cement. A total of 120 disk-shaped zirconium-oxide ceramic blocks(3-TZP, Kyoritsu, Tokyo, Japan) were treated as follows: (1) no treatment; (2) sandblasting with 110 ${\mu}m$ aluminum-oxide(Al2O3); (3) particles tribochemical silica coating(RocatecTM, 3M ESPE). Then zirconium-oxide ceramic blocks were divided into six groups(10 for each group) and bonded with resin cement(Rely X U-200, 3M ESPE). (1) No treatment / No treatment (2) No treatment / Sandblasting with 110 ${\mu}m$ aluminum-oxide particles (3) No treatment / Silica coating (4) Sandblasting with 110 ${\mu}m$ aluminum-oxide particles / Sandblasting with 110 ${\mu}m$ aluminum-oxide particles (5) Sandblasting with 110 ${\mu}m$ aluminum-oxide particles / Silica coating (6) Silica coating / Silica coating. Each group was tested in shear bond strengths by UTM. Data analysis included one-way analysis of variance(ANOVA) and the Tukey Honestly Significant Difference test (P=0.05). Group that bonded two silica coated specimen showed a highest bond strength(P<0.05). Two silica coated surface conditioning group and air-abrasion and silica coated surface conditioning group showed significantly difference with other groups(P<0.05). Other groups had no significantly difference each other. Within the limitation of this study, Surface conditioning with Rocatec treatment to each side of specimen provided the highest bond strength.

• Transactions of the Society of Information Storage Systems
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• v.6 no.2
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• pp.68-73
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• 2010

The interest in acquiring high efficiency solar cells has been steadily increasing due to various advantages such as low-cost installation, pollution free and everlasting energy generation. In order to raise the cell efficiency, there has been a lot of effort to develop effective anti-reflection coatings. In this work, the main objective was to investigate the effects of particle size and annealing temperature of silica anti-reflection coatings to maximize the cell efficiency as well as reliability. It was shown that the light transmittance could be increased by a few percent over a certain range of wavelength using the silica coating. Also, the tribological properties of the coating could be improved through the annealing process, which led to better reliability of the coating.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.535-540
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• 2011

Organic-inorganic hybrid coating solutions were prepared starting from colloidal silica, lanthanum nitrate and ${\gamma}$-glycidoxypropyl trimethoxysilane by the sol-gel method. Also, spiropyran-doped hard coating solutions were prepared by mixing the spiropyran solution, obtained after dissolving spiropyran dye into tetrahydrofuran solvent, with the organic-inorgnic hybrid coating solutions. The spiropyran-doped hard coating solutions were applied as a thin layer to polycarbonate sheets, and their photochromic properties were investigated. The effect of amount of colloidal silica added into the coating solutions was investigated on the photochromic properties of coating films. Both decoloration rate and pencil hardness of the coating films were increased with increasing the amounts of colloidal silica.

• Journal of Powder Materials
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• v.21 no.1
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• pp.21-27
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• 2014

In this study, diatomite based materials were investigated as a support filter for silica particle coating. The silica sol for coating was synthesized by a st$\ddot{o}$ber process. The diatomite support was dry-pressed at 10 MPa and sintered at $1200^{\circ}C$ for 1 hour. The coating sol was prepared as a mixture of EtOH and silica sol. The diatomite support was coated by a dip-coating process. Silica coated diatomite filter was sintered at $1000{\sim}1200^{\circ}C$ for 1 hour. The largest pore size was decreased with increasing concentration ratio of coating sol. The gas and water permeability of silica coated diatomite decreased with increasing of concentration ratio of the coating sol.

• Journal of Powder Materials
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• v.25 no.5
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• pp.379-383
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• 2018

Silica is used in shell materials to minimize oxidation and aggregation of nanoparticles. Particularly, porous silica has gained attention because of its performance in adsorption, catalysis, and medical applications. In this study, to investigate the effect of the density of the silica coating layer on the color of the pigment, we arbitrarily change the structure of a silica layer using an etchant. We use NaOH or $NH_4OH$ to etch the silica coating layer. First, we synthesize ${\alpha}-FeOOH$ for a length of 400 nm and coat it with TEOS to fabricate particles with a 50 nm coating layer. The coating thickness is then adjusted to 30-40 nm by etching the silica layer for 5 h. Four different shapes of ${\alpha}-FeOOH$ with different colors are measured using UV-vis light. From the color changes of the four different shapes of ${\alpha}-FeOOH$ features during coating or etching, the $L^*$ value is observed to increase and brighten the overall color, and the $b^*$ value increases to impart a clear yellow color to the pigment. The brightest yellow color was that coated with silica; if the sample is etched with NaOH or $NH_4OH$, the $b^*$ value can be controlled to study the yellow colors.

• Applied Chemistry for Engineering
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• v.19 no.1
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• pp.45-50
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• 2008

The self assembled silver process and silver coating process after surface reforming for silica particle, were investigated to coat the silver to colloidal silica. The effects of silver amounts and reductant amounts on silver coating efficiencies were investigated. The silver coating process after surface reforming for silica particle using MPTS (3-Mercaptopropyl trimethoxysilane) and APTS (3-Aminopropyl trimethoxysilane), showed the higher coating efficiency and better antibacterial effect than the self assembled silver process.

• The korean journal of orthodontics
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• v.40 no.3
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• pp.184-194
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• 2010

Objective: The purpose of this study was to investigate the effect of tribochemical silica coating on the shear bond strength (SBS) of rebonded ceramic brackets using nano-filled flowable composite resin. Methods: A total of 60 premolars were prepared and divided into 4 equal groups as follows: Tribochemical silica coating (TC) + Transbond XT (XT), TC + Transbond supreme LV (LV), Sandblast treatment (SA) + XT, SA + LV. Treated ceramic brackets were rebonded on the premolars using each adhesive. All samples were tested in shear mode on a universal testing machine. Results: SBS of silica coated groups were high enough for clinical usage (TCLV: 10.82 $\pm$ 1.82 MPa, TCXT: 11.50 $\pm$ 1.72 MPa). But, SBS of the sandblast treated groups had significantly lower values than the tribochemical silica coated groups (SALV, 1.23 $\pm$ 1.16 MPa; SAXT, 1.76 $\pm$ 1.39 MPa; p < 0.05). There was no difference between the shear bond strength by type of adhesive. In the silica coated groups, 77% of the samples showed bonding failure in the adhesive. In the sandblast treated group, all bonding failures occurred at the bracket-adhesive interface. Conclusions: The result of this study suggest that newly introduced nano-filled flowable composite resin and tribochemical silica coating application on debonded ceramic bracket bases can produce appropriate bond strengths for orthodontic bonding.

• Korean Chemical Engineering Research
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• v.55 no.6
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• pp.830-836
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• 2017

Hydrophilic coating solutions were prepared by reacting a silane coupling agent, GPTMS (3-glycidoxypropyl trimethoxysilane) with colloidal silica. Hydrophilic coating films were also obtained by depositing the hydrophilic coating solutions on polycarbonate substrates by spin-coating and subsequently by thermal curing at $120^{\circ}C$. During this process, the effect of average particle sizes of colloidal silica was studied on the properties of coating films. As a result, coating film, prepared from colloidal silica with average particle size of 25 nm, showed a low contact angle of $20^{\circ}$ and a good pencil hardness of H. On the other hand, coating films, prepared from colloidal silica with average particle sizes of 15 nm and 45 nm, exhibited high contact angles of $27^{\circ}$ and $36^{\circ}$ and pencil hardness of H and B, respectively.