• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.3
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• pp.454-460
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• 2015

The present study is undertaken to evaluate the effect of volume fraction on the results of Charpy impact test for the rubber matrix filled with nano sized silica particles composites. The Charpy impact tests are conducted in the temperature range $0^{\circ}C$ and $-10^{\circ}C$. The range of volume fraction of silica particles tested are between 11% to 25%. The critical energy release rate $G_{IC}$ of the rubber matrix composites filled with nano sized silica particles is affected by silica volume fraction and it is shown that the value of $G_{IC}$ decreases as volume fraction increases. In regions close to the initial crack tip, fracture processes such as matrix deformation, silica particle debonding and delamination, and/or pull out between particles and matrix which is ascertained by SEM photographs of Charpy impact fracture surfaces.

• Journal of the Korean Ceramic Society
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• v.49 no.4
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• pp.347-351
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• 2012

Vermiculite-silica composites with a layered structure were fabricated by adding cellulose fibers as a pore former and by a simple uniaxial pressing and subsequent sintering process. Three different combinations of additives were used and their effects on the compressive strength and thermal conductivity of the composites were investigated. Both compressive strengths (42-128 MPa) and thermal conductivities (0.75-1.48 $W/m{\cdot}K$) in the direction perpendicular to the pressing direction (T) were higher than those (19-81 MPa and 0.32-1.04 $W/m{\cdot}K$) in the direction parallel to the pressing direction (S) in all samples. The anisotropy in both properties was attributed to the microstructural anisotropy, which was caused by the layered structure developed in the composites.

• Elastomers and Composites
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• v.55 no.3
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• pp.167-175
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• 2020

Various studies have been conducted to improve silica dispersion of silica filled tire tread compounds; among them, silica wet masterbatch (WMB) technology is known to be suitable for manufacturing silica filled compounds that have high silica content and high dispersibility. Till now, the WMB study is focused on the natural rubber (NR) or emulsion styrene-butadiene rubber (ESBR) that does not have a silica-affinity functional group, and a study of NR or ESBR having a silica-affinity functional group is still not well known. Unlike the dry masterbatch technology, the WMB technology can solve the problems associated with the high Mooney viscosity when applied to silica-friendly rubber. However, a coagulant suitable for each functional group has not yet been determined. Therefore, in this study, different coagulant applied silica WMB was prepared by applying calcium chloride, sulfuric acid, acetic acid, and propionic acid by using a carboxyl group functionalized reversible addition fragmentation chain transfer ESBR. The evaluation of the WMB compounds revealed that the calcium chloride added WMB compound showed excellent silica dispersion, abrasion resistance, and rolling resistance.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.9
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• pp.1181-1188
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• 2018

In order to develop new insulating materials for GIS Spacer using environmentally friendly insulating gas, three kinds of dispersed liquid nano composites of solid epoxy /nano layered silicate filled material were prepared. And the epoxy/nano/micro silica composite was prepared by mixing epoxy/nano 3 phr dispersion/4 kinds of filler contents(40,50,60, 70wt%). The electrical insulation breakdown strengths of the nano and nano/micro mixed composites were evaluated by using 8 kinds of samples including the original epoxy. The mechanical tensile strength of the epoxy / nano / micro silica composite were evaluated, also. The TEM was measured to evaluate the internal structure of nano/micro composites. As a result, it was confirmed that the layered silicate nano particles was exfoliated through the process of inserting epoxy resin between silicate layers and the layers. In addition, dispersion of nano / micro silica resulted in improvement of electrical insulation breakdown strength with increase of filling amount of dense tissue with nanoparticles inserted between microparticles. In addition, the tensile strength showed a similar tendency, and as the content of microsilica filler increased, the mechanical improvement was further increased.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.10
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• pp.6816-6822
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• 2015

In this study, silica aerogel-glass wool composites were developed for improvement of thermal conductivity and overcoming the water adsorption of glass wool boards. Silica aerogel-glass wool composites were prepared by glass wool and silica aerogel with liquid binder. Mixtures with binder were composed of CMC (carboxymethyl cellulose) and silica aerogel for glass wool board. Silica aerogel-glass wool composite boards were had $0.065g/cm^3$ density by impregnation silica aerogel where from origin glass wool board at $0.048g/cm^3$ density. Thermal conductivity of silica aerogel-glass wool composites were 0.0315 W/mK (up to 7.4% thermal resistance) and fire penetration time came to 362 seconds (up to 2.7 times stronger than origin glass wool board). In addition, hydrophobic aerogel characteristics prevented the adsorption of water onto silica aerogel-glass wool composite boards that was good for lightweight.

• Journal of Institute of Convergence Technology
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• v.8 no.1
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• pp.27-31
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• 2018

The age of electric vehicle is coming. One of the most important problems to be solved for popularization of electric vehicle is fuel economy. To increase fuel economy of electric vehicles, it is necessary to improve the performance of the battery or the car body should be lighter than now. To solve the problem of the car body, change the car body's material to carbon fiber reinforced composites can be an excellent answer. However, the part made from carbon fiber reinforced composites is vulnerable to accidents due to their high brittleness. In this study, ductile silica fume was added into the carbon fiber composites to enhance toughness. To examine this, various amounts and sizes of silica fume were considered and the toughness enhancement was examined by performing tensile tests.

• Magazine of the Korea Concrete Institute
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• v.6 no.5
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• pp.158-170
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• 1994

The results of an experimental study on the manufacture and the mechanical properties of carbon fiber rekforced silica fume . cement composites and light weight fly ash . cement composites are presented in this paper. 11s the test results show, the flexural strength, fracture toughness and ductility of CF reinforced silica fume . cement composites were remarkably increased by the increase of carbon fiber contents. And the workability of the fly ash . cement composites were improved, but the compressive and flexural strength and bulk specific gravity of them are decreased by increasing the ratio of fly ash to cement. And the compressive and flexural strength of the fly ash cement composites by cured under the hot water were improved than those by mositure cured. Also, the manufacturing process technology of lightweight fly ash . cement composites in replacement of general autoclaved lightweight concrete was developed and its optimum mix proportions were proposed.

• Magazine of the Korea Concrete Institute
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• v.6 no.4
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• pp.141-152
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• 1994

The results of an experimental study on the development and the evaluation of lightweight and high strength composites utilizing by-products and calcium silicates for construction materials are presented in this paper. The composites using early strength portland cement, by-Products( f1y ash, silica fume), silica powder, quick lime, gypsum, A1 powder and fibers(PAN-derived CF, alkali-resistance GF) were prepared using various mixing conditions. As the test results show, PAN-derived CF and alkali-resistance GF were suitable for rein-forcing fiber of the composites. And the mechanical properties,such as compressive tensile flexural strength, and toughness of Lt. Wt. fiber reinforced calcium silicates cement comp-osites were improved by increasing the fly ash and silica fume contents, and fiber contents, especially by increasing fiber contents the toughness of the composites were remarkably in-creased. Also, compressive tensile flexural strength,and toughness of the composites rein-forcing PAN-derived CF were higher than those of the composites reinforcing alkali-resistance GF..

• Journal of the Korean Ceramic Society
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• v.29 no.11
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• pp.893-899
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• 1992

Composite specimens, which are composed MDF cement of HAC-PVA system were prepared by adding carbon fiber, hydrated silica and SiC powder, and we studied effect of additives on the flexural strength of the composites. All of additives is effective in the improvement of flexural strength of the composite specimens. The size of average pore diameter in the specimens which have high flexural strength property was small. Specimen mixed with hydrated silica was effective in the particle compact property. Flexural strength of carbon fiber reinforced MDF cement composites were improved because of crack deflection of carbon fiber in cementitious matrix.

• Polymer(Korea)
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• v.27 no.2
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• pp.91-97
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• 2003

The effect of fluorination of nanoscaled silicas on mechanical interfacial properties and thermal stabilities of the silica/polyurethane composites was investigated. The surface properties of the silica were studied in X-ray photoelectron spectroscopy and contact angle measurements. Their mechanical interfacial properties and thermal stabilities of the composites were characterized by tearing energy and decomposition activation energy, respectively. As experimental results, the London dispersive component of surface free energy and fluorine functional groups of silica surfaces were increased as a function of fluorination temperature resulting in improving the trearing energy ($G_{IIIC}$) of the composites. Also, the thermal stabilities of the composites were increased as the treatment temperature increases. These results could be explained that the fluorine functional groups on silica surfaces played an important role in improving the intermolecular interactions at interfaces between silicas and polyurethane matrix in a composite system.