• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.1
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• pp.215-225
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• 2011

Metakaolin is a dehydroxylated form of the clay mineral kaolinite. Rocks that are rich in kaolinite are known as china clay or kaolin, traditionally used in the manufacture of porcelain. The particle size of metakaolin is smaller than cement particles, but not as fine as silica fume. This paper investigates the effect of the concrete containing metakaolin as a mineral admixture on the compressive strength and resistance properties to chloride ion penetration. In this study, the experiment was carried out to investigate and analyze the influence of replacement ratio of metakaolin and micro silica fume on the compressive strength and chlorine ion penetration resistance of concrete. All levels were water/binder ratio 30%, replacement ratio of metakaolin and silica fume were 0, 5, 10, 15, 20% respectively. The compressive strength of concrete using metakaolin tends to increase, as the replacement ratio increases but the chlorine ion penetration resistance was not so as lager as silica fume concrete. Therefore, the optimum mixing ratio of metakaoline to satisfy a properties of compressive strength and chlorine ion penetration resistance was was approximately10%.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.5
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• pp.212-217
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• 2021

The applicability of the white LED from the blue LED of the coating film as a binder for surface and curved coatings were confirmed. The particle size of YAG is D₅₀: 9~10 ㎛, and the crystal structure is garnet (Y₃Al₅O₁₂), cubic. The coating film had no cracks, at the same time, the silica sol was uniformly coated with YAG phosphor, and the YAG content and thickness in the coating film showed a tendency to increase up to 40 ㎛ in proportion to the increase in the amount added. Furthermore, as the YAG content increased, the PL emission intensity increased and the color coordinate shift toward the end of the chromatic locus curve was confirmed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.487-487
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• 2009

One of the critical consumables in chemical mechanical polishing (CMP) is a specialized solution or slurry, which typically contains both abrasives and chemicals acting together to planarize films. In single abrasive slurry (SAS), the solid phase consists of only one type of abrasive particle. On the other hand, mixed abrasive slurry (MAS) consists of a mixture of at least two types of abrasive particles. In this paper, we have studied the CMP characteristics of mixed abrasive slurry (MAS) retreated by adding of $CeO_2$ abrasives within 1:10 diluted silica slurry (DSS). The slurry designed for optimal performance should produce reasonable removal rates, acceptable polishing selectivity with respect to the underlying layer, low surface defects after polishing, and good slurry stability. The modified abrasives in 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 with original silica slurry in the viewpoint of high removal rate and low non-uniformity.

• Journal of the Korean Ceramic Society
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• v.39 no.10
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• pp.981-987
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• 2002

Monodispersed colloidal silica was prepared by Stober process. We have synthesized monodispersed colloidal silica of carious sizes (100 nm, 200 nm, 300 nm) by controlling volume ratios of TEOS(Tetraethylorthosilicate), $NH_4OH$, Ethanol and D. I. water. Shape and monodispersity of the synthesized colloidal particles were observed by Scanning Electron Microscopy(SEM) and laser light scattering particle analyzer. Self-assembled monolayer of monodispersed colloids was achieved by dipping Si substrate into a well-dispersed silica suspension. It was determined that uniformity and spatial extent of the self-assemble monolayer of monodispersed colloids are significantly influenced by the experimental parameters such as concentration, pH and surface tension of the colloidal suspension. We have observed a hexagonally well-ordered packing colloidal monolayer in a relatively large area (1.5 mm ${\times}$ 1.5 mm) as confirmed by SEM.

• Journal of the Korean Ceramic Society
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• v.42 no.3 s.274
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• pp.205-210
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• 2005

Nanoscale silica powder was synthesized from $SiO_2$ precursor solution using Tetraethyl Orthosilicate (TEOS) by polyacrylamide gel method. This process was of simplicity and provided ultrafine powders at relatively low calcination temperatures because polymer network could inhibit aggregation of $SiO_2$ powder. The particle size of Si02 powder was affected by the concentration of ammonium persulphate and N, N'-methylene-bis-acrylamide(BIS) in the gel precursor. The particle size decreased with increasing ammonium persulphate and was mininum size of 10 nm at 0.01 M. Also, the size decreased with increasing BIS concentration and was 5 nm at its concentration of 0.05 M.

• Journal of the Korea Concrete Institute
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• v.27 no.3
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• pp.273-281
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• 2015

In this paper, the performance of alkali-activated slag cement (AASC) is assessed in terms of compressive strength and drying shrinkage, using three different types of silica sand and river sand. The sand type has an important influence on the properties of AASC mortar. Three silica sands (SS1, SS2 and SS3) and river sand (RS) were considered. Three series of blended sands have been tested. A first series (S1) with RS and SS1, a second series (S2) with RS and SS2 and third series (S3) with RS and SS3 with a different blended ratios. The result shows a very significant influence of the blended sand on the AASC mortar properties. The compressive strength and drying shrinkage related with the particle sizes and blended ratios of sands are investigated considering blended sand properties like fineness modulus (FM) and relative specific surface. The type and blended ratio of sand seems to have very significant and important consequences for the mix design of the AASC mortar.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.3
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• pp.17-22
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• 2003

This paper presents an experimental investigation of a reversible colloidal seismic damper, which is statically loaded, The porous matrix is composed from silica gel (labyrinth or central-cavity architecture), coated by organo-silicones substances, in order to achieve a hydrophobic surface. Water is considered as associated lyophobic liquid. Reversible colloidal damper static test rig and the measuring technique of the static hysteresis are described. Influence of the pare and particle diameters, particle architecture and length of the grafted molecule upon the reversible colloidal damper hysteresis is investigated, for distinctive types and mixtures of porous matrices, Variation of the reversible colloidal damper dissipated energy and efficiency with temperature, pressure, is illustrated.

• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3641-3649
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• 2022

A simple solvothermal reaction was used to prepare a 3-aminopropyl-functionalized silica-gel-based adsorbent for adsorbing Pd(II) from the nitric acid solution. Scanning electron microscopy, fourier transform infrared spectroscopy, and thermogravimetry analysis were performed on the as-synthesized adsorbent to demonstrate the successful introduction of Schiff base groups. Batch experiments were used to investigate the effects of contact time, nitric acid concentration, solution temperature, and adsorption capacity. It is worth noting that the prepared adsorbent exhibited a higher affinity toward Pd(II) with the uptake approximately 100% even in a 2 M HNO₃ solution. At an equilibrium time of 5 h, the maximum adsorption capacity of Pd(II) was estimated to be 0.452 mmol/g. The adsorbed Pd(II) could be completely eluted by dissolving 0.2 M thiourea solution in 0.1 M HNO₃. Using a combination of particle-induced X-ray emission analysis and an X-ray photoelectron spectrometer, the adsorbed Pd was found to be uniformly distributed on the surface of the prepared adsorbent and the existing species were Pd(II) and zero-valent Pd(0). Due to the desirable performances, facile preparation method, and abundant raw material source, the prepared adsorbent demonstrated a high application potential in the recovery of Pd(II) from simulated high-level liquid waste treatment.

• Tuberculosis and Respiratory Diseases
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• v.41 no.5
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• pp.513-520
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• 1994

Background: The pathogenesis of silicosis has been focused on the interaction between alveolar macrophages and silica particle. Although fibrosis in silicosis has been studied extensively, the mechanism is still not fully understood. There is increasing evidence that monokines and arachidonic acid metabolites macrophage are involved in pathogenesis of silicosis. Recently, it was reported that prostaglandin E2 produced from macrophage counteracts the stimulatory effects of other monokines on fibroblast proliferation or collagen production. Until now, it was remained uncertain by which mechanism silica particle may activate alveolar macrophage to an enhanced release of prostaglandin E2. Methods: In order to investigate the relationship between the activity of alveolar macrophage and the production of $PGE_2$ from activated alveolar macrophage, the authors measured hydrogen peroxide and $PGE_2$ from alveolar macrophages activated by silica in vitro and from alveolar macrophages in the silicotic nodules from rat. Experimental silicosis was induced by intratracheal infusion of silica($SiO_2$) suspended in saline(50 mg/ml) in Sprague-Dawley rats. Results: produced by 1) The silicotic nodules with fibrosis were seen from the sections of rat lung at 60 days after intratracheal injection with 50 mg aqueous suspension of silica(Fig. 1). 2) In vitro, silica caused the dose dependent increase of hydrogen peroxide(p<0.05, Fig. 2A) and $PGE_2$(p>0.05, Fig. 2B) release from alveolar macrophages. Alveolar macrophages from rat with silicotic nodules released more hydrogen peroxide and $PGE_2$ than those of control group(p<0.05, Fig. 3). Conclusion: These results suggest that silica particle could activate macrophage directly and enhanced the release of $PGE_2$ and hydrogen peroxide from the alveolar macrophage.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.1
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• pp.86-92
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• 2009

We fabricated the charged particle type display using opposite-charged two toner particles. The particles were composed of polymer, colorant($TiO_2$, carbon black) and external additives(nano-sized silica and so on). In fabrication process we controlled the putting layers of this toner particles on the inner panel. To get the effect of number of layers ($1{\sim}3$), we measured the threshold, driving and breakdown voltages, reflectivity, viewing angle, and color characteristics using RT-300 anisotropic scattering system. We ascertained that these voltages are increased with increasing of layers of particles. Cell gap between electrodes must be enlarged with increment of layers and the size of particles. The lumping phenomena of particles at near of the rib observed by optical system with same CIE values.