• The Journal of Advanced Prosthodontics
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• v.9 no.2
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• pp.130-137
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• 2017

PURPOSE. The purpose of this study was to evaluate the effect of nano-structured alumina surface coating on shear bond strength between Y-TZP ceramic and various dual-cured resin cements. MATERIALS AND METHODS. A total of 90 disk-shaped zirconia specimens (HASS CO., Gangneung, Korea) were divided into three groups by surface treatment method: (1) airborne particle abrasion, (2) tribochemicalsilica coating, and (3) nano-structured alumina coating. Each group was categorized into three subgroups of ten specimens and bonded with three different types of dual-cured resin cements. After thermocycling, shear bond strength was measured and failure modes were observed through FE-SEM. Two-way ANOVA and the Tukey's HSD test were performed to determine the effects of surface treatment method and type of cement on bond strength (P<.05). To confirm the correlation of surface treatment and failure mode, the Chi-square test was used. RESULTS. Groups treated with the nano-structured alumina coating showed significantly higher shear bond strength compared to other groups treated with airborne particle abrasion or tribochemical silica coating. Clearfil SA Luting showed a significantly higher shear bond strength compared to RelyX ARC and RelyX Unicem. The cohesive failure mode was observed to be dominant in the groups treated with nano-structured alumina coating, while the adhesive failure mode was prevalent in the groups treated with either airborne particle abrasion or tribochemical silica coating. CONCLUSION. Nano-structured alumina coating is an effective zirconia surface treatment method for enhancing the bond strength between Y-TZP ceramic and various dual-cured resin cements.

• Journal of the korean society of oceanography
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• v.38 no.1
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• pp.1-10
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• 2003

A time-series sediment trap was deployed at a depth of 1034 m in the eastern Bransfield Strait from December 25, 1998 to December 24, 1999. Particle fluxes showed large seasonal variation; about 99% of the annual total mass flux (49 g m/sup -2/) was collected during the austral summer and fall (January-March). Settling particles consisted primarily of biogenic silica, organic carbon, calcium carbonate, and lithogenic material. Biogenic silica and lithogenic material predominated settling particles, comprising 36% and 30% of the total mass flux, respectively, followed by organic carbon, 11% and calcium carbonate, merely 0.6%. The annual organic carbon flux was 5.4 g C m/sup -2/ at 1000 m in the eastern Bransfield Strait, which is greater than the central Strait flux. The relatively lower flux of organic carbon in the central Bransfield Strait may be caused by a stronger surface current in this region. Organic carbon flux estimates in the eastern Bransfield Strait are the highest in the Southern Ocean, perhaps because of the fast sinking of fecal pellets, which leads to less decomposition of organic material in the water column. Approximately 5.8% of the organic carbon produced on the surface in the eastern Bransfield Strait is exported down to 1000 m; this percentage exceeds the maximum EF/sub 1000/ values observed in the Atlantic and Southern Oceans. The eastern Bransfield Strait appears to be the most important site of organic carbon export to the deep sea in the Southern Ocean.

• Applied Chemistry for Engineering
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• v.24 no.4
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• pp.357-362
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• 2013

Monodispersed polystyrene latex spheres (PLS) and PS-MPS/silica composite nanospheres were used to test high efficiency particulate air (HEPA) filters. Prior to filter tests, all nanospheres used in this work were characterized by measuring their average particle diameters and coefficients of variation (CV) for assessing them as artificial dusts. The average particle sizes of PLS and composite nanospheres could be well controlled in the range of 100~300 nm well by changing reaction temperature and the amount of a stabilizer during emulsion polymerization. The CV of all nanospheres were also in the range of 3~7%, lower than 15% that is the criterion for monodispersed particle distributions. Furthermore the results of HEPA filter tests show that all nanospheres used were quite proper as artificial dusts for testing air filters.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.1 no.1
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• pp.92-99
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• 1991

The reaction obtaining $SiO_2$ fine particle from $ Si(OC_2H_5)_4$consists of two steps, that is, hydrolysis and polycondensation. Polycondensation is the first order with respect to the concentration of $Si(OC_2H_5)_4$As the concentration of water, ammonia reaction temperature are increased, the reaction rate constant of polycondensation is increased.Silica particles formed are spherical and very uniformly dispersed. The diameters of them are be-tween 0.06 and $0.27\mu\textrm{m}$. As the initial concentration of $Si(OC_2H_5)_4$is decreased and the reaction temper-ature is increased, the diameters of silica particles are reduced. The rate of particles growth derived from time vs, conversion data, is represented as follows; d=a.ln(Xa)+b, where d is the diameter of silica and a, b are constant. The final diameter of silica approaches to the value of b.

• Journal of the Korean Ceramic Society
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• v.41 no.10 s.269
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• pp.766-770
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• 2004

High-transmittance film was coated by using spherical silica nano colloids. Silica colloid sol was preservred between two inclined slide glasses by capillary force, and particles were stacked to form a film onto the substrate as the upper glass was sliding. As the sliding speed increased, the thickness of the film decreased and light transmittance varied. The microstructure observed by SEM showed that silica particles were nearly close packed, which enabled the calculation of the effective refractive index of the film. The film thickness calculated from the wavelength of maximum transmittance and the effective refractive index was well coincided with the thickness observed by SEM and measured by profiler. The maximum transmittance of $94.7\%$ was obtained. This means that $97.4\%$ of transmittance or $1.3\%$ of reflectance can be achieved by simple process if both sides of the substrate are coated.

• Korean Chemical Engineering Research
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• v.54 no.3
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• pp.293-298
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• 2016

A hydrogel electrolyte consisting of 6 M KOH aqueous solution, potassium polyacrylate (PAAK, 3 wt.%), and a hydrophilic silica OX50 (1 wt.%) was prepared to use as an electrolyte medium coated on a Scimat separator of activated carbon supercapacitor. The silica particle distributed homogeneously on surface pores of the separator to increase ionic conductivity and electrochemical stability of the hydrogel electrolyte. The silica addition also involved superior specific capacitance even at higher scan rates due to decrease in interfacial resistance between hydrogel electrolyte and activated carbon electrode.

• Journal of the Korean Ceramic Society
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• v.34 no.2
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• pp.188-194
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• 1997

Wet gel with surface modification by TMCS was redispersed in EtOH and redispersed silica sol for coat-ing was prepared. After spin coating of redispersed sol was conducted on silicon substrate, processes of drying(8$0^{\circ}C$) and heat treatment(>25$0^{\circ}C$) were, followed at ambient pressure. The influence of heat treat-ment of properties of film was observed, changing temperature at heat treatment. The optimum redisp-ersion condition for stable silica sol was wet gel:EtOH=1g:110$m\ell$ and the concentration and viscosity of redispersed silica sol with average particle size of 30nm were 0.11 M, 2.0-2.2 cP respectively. Crack-free thin film with the refractive index of 1.14 and thickness of 400 nm was obtained through drying at 8$0^{\circ}C$ and subsequent heat treatment at 45$0^{\circ}C$ for 2 hrs respectively after spin coating of 1500rpm, 10 times.

• Journal of IKEEE
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• v.23 no.4
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• pp.1175-1181
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• 2019

In this paper, we have studied the chemical mechanical polishing(CMP) characteristics of mixed abrasive silica slurry(MAS) retreated by adding of manganese oxide(MnO₂) abrasives within 1:10 diluted silica slurry. A slurry designed for optimal performance should produce high removal rates, acceptable polishing selectivity with respect to the underlying layer, low surface defects after polishing, and good slurry stability. The polishing performances of MnO₂ abrasive-added MAS are evaluated with respect to their particle size distribution, surface morphology, and CMP performances such as removal rate and non-uniformity. As an experimental result, we obtained the comparable slurry characteristics compared to original silica slurry in the view-point of high removal rate and low non-uniformity. Therefore, our proposed MnO₂-MAS can be useful to save on the high cost of slurry consumption since we used a 1:10 diluted silica slurry.

• Journal of the Korean Ceramic Society
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• v.41 no.7
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• pp.548-554
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• 2004

A sol-gel method was applied to coat TiO$_2$ on porous silica prepared using slurry foaming method from silica. from the results of XRD, SEM, and BET, the anatase phase was firstly observed at the coated supports with the heated of 50$0^{\circ}C$. The coated supports with the heated of $700^{\circ}C$ had the maximum anatase peak, and the particle size of coated TiO$_2$ was about 1 ${\mu}{\textrm}{m}$. Bending strength and gas permeability of the porous silica were measured for the feasibility as a catalytic supports. In case of the uncoated porous materials with the strength of 2.4 MPa, the strength increased to 3.9∼4.3 MPa after the coating process regardless of the heating temperature. On the other hand, the permeability of the uncoated porous materials decreased from 770${\times}$10$^{-13}$ $m^2$ to 363${\times}$10$^{-13}$ $m^2$ after the coating process, and it decreased with the increasing heating temperature.

• Membrane Journal
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• v.27 no.1
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• pp.77-83
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• 2017

Transient behavior of fouling resistance was observed with a laboratory-scaled, submerged microfiltration membrane system treating high-turbidity source water consisting of inorganic silica particles and humic acid. Fouling mitigation efficiency with inorganic silica particles caused by aeration was reduced significantly as both humic acid and calcium ion existed together. Scanning electron microscopic observations showed that humic acid was adsorbed onto the surface of inorganic silica particles in the presence of calcium. Turbidity removal was achieved almost completely by submerged MF system regardless of feed compositions. However, the $UV_{254}$ removal of humic acid was improved in the presence of both calcium and inorganic silica particles. Additionally, increasing air-flow rate tended to increase $UV_{254}$ removal efficiency higher than 80%. This may be caused by back-transport of humic acid enhanced by inorganic silica particles providing surface for organic adsorption in the presence of calcium.