• Transactions on Electrical and Electronic Materials
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• v.7 no.4
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• pp.167-172
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• 2006

Submicron colloidal silica coated with ceria were prepared by mixing of silica and nano ceria particles and modified by hydrothermal reaction. The polishing efficiency of the ceria coated silica slurry was tested over oxide film on silicon wafer. By changing the polishing pressure in the range of $140{\sim}420g/cm^2$ with the ceria coated silica slurries in $100{\sim}300nm$, rates, WIWNU and friction force were measured. The removal rate was in the order of 200, 100, and 300 nm size silica coated with ceria. It was known that the smaller particle size gives the higher removal rate with higher contact area in Cu slurry. In the case of oxide film, the indentation volume as well as contact area gives effect on the removal rate depending on the size of abrasives. The indentation volume increase with the size of abrasive particles, which results to higher removal rate. The highest removal rate in 200 nm silica core coated with ceria is discussed as proper combination of indentation and contact area effect.

• Clean Technology
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• v.16 no.2
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• pp.140-144
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• 2010

Titania-silica composite materials were obtained by sol-gel method from TiCl4 and TEOS precusors, and they were applied to anode materials of lithium ion battery. Uniformly distributed composite materials can be manufactured by sol-gel method. The composite materials were heat treated by microwave to obtain materials with new properties. The experimental variables were composition of the material, heat treatment temperature, and microwave exposure. The structure and surface properties of the materials were analyzed by XRD, SEM, and the electrochemical capacity was measured with charge/discharge cycler.

• Transactions on Electrical and Electronic Materials
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• v.13 no.3
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• pp.153-156
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• 2012

In order to develop electrical insulation materials, epoxy/micro-silica composite (EMC) and epoxy/micro-silica/nano-silicate composite (EMNC) were prepared, and their tensile and flexural strength, AC insulation breakdown strength and thermal conductivity and thermal expansion coefficient were compared. Nano-silicate was prepared in an epoxy matrix by our AC electric field process. All properties of the neat epoxy were improved by the addition of micro-silica, which was improved much further by the addition of nano-silicate to the EMC system.

• Journal of Biomedical Engineering Research
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• v.18 no.1
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• pp.1-8
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• 1997

This study was performed to evaluate the effect of resin and filler type on the compressive strength of light-activated composite resins. Experimental composite resins containing either amorphous spherical silica or crushed quartz in two matrix resins of BisGMA/TEGDMA and UTMA/TEGDMA were prepared and the specimens of 3 m in diameter and 6m in length were made. Compressive test was subjected to a crosshead speed of 0.5 mm/min, and the fracture surFaces were examined by SEM. The compressive strength of UTMA-based composite resin was higher than that of BisGMA-based composite resin. The loading rate of spherical silica was higher than that of crushed silica when the size dis- tribution of fillers was same. Strength decrease of Bis-GMA-based composite resin was severer than that of UTMA-based composite resin in a $37^{\circ}$c water environment. Fracture surface showed that the composite resin failure developed along the matrix resin and the filler/resin interface region.

• Applied Chemistry for Engineering
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• v.29 no.4
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• pp.425-431
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• 2018

Composite particles of porous silica and cerium oxide nanoparticles blocking UV/blue light were prepared through a dry coating process. Various composite particles were prepared by varying conditions such as the mixing ratio of cerium oxide and silica, and the chamber rotating speed of mechano fusion system. The surface morphology of the composite particles was observed with SEM and the composition was analyzed using X-ray fluorescence (XRF). When the cerium oxide/silica composite particles were dispersed in water, the transparency and dispersion stability of the colloidal solution were improved. In addition, the fluidity and spreadability of the particle powder were enhanced by making composite particles. These results show that cerium oxide/silica composite particles can be used as functional cosmetic ingredients for UV/blue light protection.

• Korean Journal of Materials Research
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• v.15 no.12
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• pp.818-823
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• 2005

Sub-micron colloidal silica particles coated with nano-sized ceria were prepared by mixing of its silica and cerium salts hydrolysis, and modified by hydrothermal reaction. By using the slurries with and without hydrothermal modification containing above particles, oxide film coated on silicon wafer was polished. The modified slurries had higher polish rate due to increase of ceria fraction to silica through hydrothermal reaction. They revealed higher stability in wide range of pH $2\~10$ than ceria coated silica slurries without its modification.

• Journal of Integrative Natural Science
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• v.9 no.1
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• pp.62-66
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• 2016

To manipulate the mechanical properties of acrylonitrile butadiene rubber (NBR), addition of nano-sized silica on rubber was performed and nano-silica NBR composite (NSR) materials were fabricated by press molding. The effect of volume fraction of silica in the NSR on the spectroscopic and mechanical properties has been studied.

• Applied Chemistry for Engineering
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• v.17 no.4
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• pp.403-408
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• 2006

To enhance the dental properties of polymeric dental restorative composite activated by visible-light, the surface of hydrophilic silica nanoparticle was hydrophobically treated using $\gamma$-methacryloxypropyltrimethoxysilane ($\gamma$-MPS) coupling agent. Structural properties and dispersity of silica in the composite was compared with the hydrophobicity of silica. Polymerization characteristic of the composite was also evaluated. Degree of hydrophobicity of silica nanoparticle was considerably improved with an increase of $\gamma$-MPS upto 40 wt% and converged asymptotically. Additionally, with an increase of the hydrophobicity of silica nanoparticle, the dispersity of silica was improved and the residual monomer in the composite was not detected from nuclear magnetic resonance experiment which indicated superior polymerization behavior.

• Membrane Journal
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• v.24 no.6
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• pp.491-497
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• 2014

PTMSP-silica composite membranes were prepared by addition of 0, 15, 20, and 30 wt% TEOS (tetraethoxysilane), TMOS (tetramethoxysilane), MTMOS (methyltrimethoxysilane), and PTMOS (phenyltrimethoxysilane) contents to PTMSP using sol-gel process. The gas permeability of the composite membranes for $H_2$, $N_2$ and ideal selectivity for $H_2$ over $N_2$ were investigated as a function of alkoxysilane content. The permeabilities for $H_2$ and $N_2$ increased in the range of alkoxysilane contents 0~20 wt%, however decrease the range of 20~30 wt%. The ideal selectivities for $H_2$ over $N_2$ decreased in the range of TEOS and PTMOS contents 0~15 wt%, but increased in the range of 15~30 wt%. When compared to the upper bound of Robeson, PTMSP-silica composite membranes with TEOS content of 30 wt%, MTMOS content of 20 wt% and PTMOS content of 30 wt% turned out to be a simultaneous improvement in ideal selectivity and permeability.

• Nano
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• v.13 no.12
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• pp.1850137.1-1850137.9
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• 2018

A series of silica surface-capped with hexamethyldisilazane (denoted as $H-SiO_2$) were prepared by liquid-phase in-situ surface-modification method. The as-obtained $H-SiO_2$ was incorporated into acrylic amino (AA) baking paint to obtain AA/$H-SiO_2$ composite extinction paints and/or coatings. $N_2$ adsorption-desorption tests were conducted to determine the specific surface area as well as pore size and pore volume of $H-SiO_2$. Moreover, the effects of $H-SiO_2$ matting agents on the physical properties of AA paint as well as the gloss and transmittance of AA-based composite extinction coatings were investigated. Results show that $H-SiO_2$ matting agents possess a large specific surface area and pore volume than previously reported silica obtained by liquid-phase method. Besides, they have better dispersibility in AA baking paint than the unmodified silica. Particularly, $H-SiO_2$ with a silica particle size of $6.7{\mu}m$ and the dosage of 4% (mass fraction) provides an extinction rate of 95.2% and a transmittance of 79.3% for the AA-based composite extinction coating, showing advantages over OK520, a conventional silica matting agent. Along with the increase in the silica particle size, $H-SiO_2$ matting agents cause a certain degree of increase in the viscosity of AA paint as well as a noticeable decrease in the gloss of the AA-based composite extinction coating, but they have insignificant effects on the hardness and adhesion to substrate of the AA-based composite coatings. This means that $H-SiO_2$ matting agents could be well applicable to preparing low-viscosity and low-gloss AA-based matte coatings.