• Bulletin of the Korean Chemical Society
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• v.33 no.9
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• pp.2966-2970
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• 2012

Fullerene/polystyrene ($C_{60}$/PS) nano particle was prepared by using emulsion polymerization. Styrene and fullerene were emulsified in aqueous media in the presence of poly(N-vinyl pyridine) as an emulsion stabilizer, and polymerization was initiated by water soluble radical initiator, potassium persulfate. The obtained nano particles have an average diameter in the range of 400-500 nm. The fullerene contents in the nano particle can be controlled up to 15 wt % by varying the feed ratio, which was confirmed by themogravimetric analysis (TGA) and elemental analysis (EA). The structure and morphologies of the $C_{60}$/PS nano particles were examined by various analytical techniques such as dynamic light scattering (DLS), scanning electron microscope (SEM), transmission electron microscope (TEM), electron diffraction (ED) pattern, X-ray powder diffraction (XRD), and UV spectroscopy. Unlike conventional $C_{60}$/PS particles initiated by organic free radical initiators, in which the fullerene is copolymerized forming a covalent bond with styrene monomer, the prepared $C_{60}$/PS nano particles contain pristine fullerene as secondary particles homogeneously distributed in the polystyrene matrix.

• Journal of the Korean Ceramic Society
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• v.53 no.4
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• pp.450-455
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• 2016

Color change in single-crystal, yellow, red, purple, and colorless cubic zirconias (CZs) was investigated as a function of annealing in vacuum and air atmosphere at $800-1400^{\circ}C$ for 30 min, for development of a damascene process of plugging a precious metal paste at the elevated temperature. Coloring-element contents of the CZs were evaluated using WD-XRF, and the color change determined visually by naked eye, and using a digital camera and UV-Vis-NIR color analyzer. WD-XRF showed that all of the CZs had cubic-phase stabilizer elements and coloring elements. All CZs that underwent vacuum annealing exhibited a slight color change at $<900^{\circ}C$, while their colors began to change to black at $1100^{\circ}C$, and became opaque black at $1400^{\circ}C$. After air annealing, there was almost no color change up to $1400^{\circ}C$. Since red and purple CZs showed greater color difference (CD) values than the others, the degree of CD is likely to depend on the original color of the CZ due to the different stabilities of their coloring elements during annealing. Based on our results, it is suggested that annealing in air at $<900^{\circ}C$ is advantageous, and assorted colored CZs can be used for precious metal damascene.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.427-434
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• 2000

Hydraulic conductivity of soil-cement was measured as a function of some selected construction variables that are often encountered in practice. They are initial (or compaction) water content, delayed compaction after mixing, and repeated freezing and thawing. Sandy and clayey soils were used. The hardening agent used was a cement based soil stabilizer consisting of 80% of ordinary Portland cement and 20% of a combination of supplementary materials. Hydraulic conductivity of soil-cement with varying initial water content was, in trend, similar to that of compacted clay. Hydraulic conductivity of soil-cement decreased with increasing initial water content and reached its minimum when compacted wet of optimum water content. Pore size distributions of soil cement at different initial water contents were analyzed using mercury intrusion porosimetry. The analysis showed that dryer condition led to the formation of larger pores with lesser total pore volume; smaller pores with larger total pore volume at wetter condition. Hydraulic conductivity of soil-cement increased by orders in magnitude when specimen underwent delayed compaction of longer than 4 hours after mixing and repeated freezing and thawing.

• Transactions on Electrical and Electronic Materials
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• v.4 no.2
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• pp.1-4
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• 2003

The purpose of this study was to investigate the characteristics of slurry including phosphoric acid for chemical-mechanical planarization of copper and tantalum nitride. In general, the slurry for copper CMP consists of alumina or colloidal silica as an abrasive, organic acid as a complexing agent, an oxidizing agent, a film forming agent, a pH control agent and additives. Hydrogen peroxide (H$_2$O$_2$) is the material that is used as an oxidizing agent in copper CMP. But, the hydrogen peroxide needs some stabilizers to prevent decomposition. We evaluated phosphoric acid (H$_3$PO$_4$) as a stabilizer of the hydrogen peroxide as well as an accelerator of the tantalum nitride CMP process. We also estimated dispersion stability and zeta potential of the abrasive with the contents of phosphoric acid. An acceleration of the tantalum nitride CMP was verified through the electrochemical test. This approach may be useful for the development of the 2$\^$nd/ step copper CMP slurry and hydrogen peroxide stability.

• Journal of the Korean Applied Science and Technology
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• v.22 no.4
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• pp.332-338
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• 2005

This study was conducted to prepare acrylic removable protective coatings by emulsion polymerization. Monomers used were n-butyl acrylate, acrylonitrile, butyl methacrylate. Emulsifiers used were sodium lauryl sulfate and polyoxyethylene lauryl ether, which are an anionic emulsifier and a nonionic emulsifier respectively. Potassium persulfate was used as an initiator and polyvinyl alcohol was used as a stabilizer. Emulsion polymerization was carried out in a semi-batch reactor at $70^{\circ}C$ and agitation speed was 200 rpm. Tensile strength, extension, peel strength, viscosity, and solid contents of the synthesized coatings were examined. The coatings prepared with BA:AN = 60:20 (in weight ratio) satisfied the standard for automobile in terms of extension and peel strength. When the concentration of BMA was in a range of $18{\sim}23$ wt%, the prepared coatings satisfied the standard for automobile in terms of peel strength and water resistance.

• Journal of the Korean Ceramic Society
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• v.35 no.12
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• pp.1294-1300
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• 1998

Yttria-stabilized zirconia ceramics with irregular grain shapes and curved grain boundaries was prepared by ceria doping. The amount of ceria doped into zirconia compacts by a dipping method were at range of 2 to 20 mol% Irregular grain shapes and curved grain boundaries were formed only inspecimens doped with more than 8mol% cerial. Ceria-doped specimens showed large grain size and low sintered density compared with pure yttria-stabilized zirconia which was due to the increase in the contents of stabilizer and cubic phase. The amount of doped ceria was larger on the surface than the inside regions and therefore mi-crostructure and phase on the surface were different from those in the inside regions. Transgranular frac-ture mode was observed ion ceria doped specimens due to irregular large grain sizes.

• Geomechanics and Engineering
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• v.10 no.5
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• pp.689-707
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• 2016

Soil stabilization is one of the useful method of ground improvement for soil with low bearing capacity and high settlement and unrequired swelling potential. Generally, the stabilization is carried out by adding some solid materials. The main objective of this research was to investigate the feasibility of stabilization of organic soils and sewage sludge to obtain low cost alternative embankment material by the addition of two different slags. Slags were used as a replacement for weak soil at ratios of 0%, 25%, 50%, 75% and 100%, where sewage sludge and organic soil were blended with slags separately. The maximum dry unit weights and the optimum water contents for all soil mixtures were determined. In order to investigate the influence of the slags on the strength of sewage sludge and organic soil, and to obtain the optimal mix design; compaction tests, the California bearing ratio (CBR) test, unconfined compressive strength (UCS) test, hydraulic conductivity test (HCT) and pH tests were carried out on slag-soil specimens. Unconfined compressive tests were performed on non-cured samples and those cured at 7 days. The test results obtained from untreated specimens were compared to tests results obtained from soil samples treated with slag. Laboratory tests results indicated that blending slags with organic soil or sewage sludge improved the engineering properties of organic or sewage sludge. Therefore, it is concluded that slag can be potentially used as a stabilizer to improve the properties of organic soils and sewage sludge.

• Elastomers and Composites
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• v.54 no.1
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• pp.7-13
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• 2019

Recycling of waste polyvinyl chloride plastics has attracted much attention due to environmental problems, but the poor mechanical properties, low thermal stability, frequent breakage of strands, and melt cracking of the waste plastics have limited their widespread use. To overcome these disadvantages of waste PVC (W-PVC), recycled PVC powder blend was prepared by adding high-density polyethylene (HDPE) and ethylene vinyl acetate (EVA) as a heat stabilizer and compatibilizer, respectively. An intermeshing co-rotating twin screw extruder was used to prepare the blend, and the characteristics of the blend were analyzed by SEM and TGA, and by using a UTM and Izod impact tester. The impact strength was improved as the EVA content increased for the W-PVC/HDPE (80/20 wt%) blend. As the HDPE and EVA contents increased in the W-PVC/HDPE/EVA blend, the impact strength increased. SEM observations also revealed the improved interfacial adhesion for the EVA-containing blend.

• Textile Coloration and Finishing
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• v.35 no.3
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• pp.151-158
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• 2023

In this study, we investigated the durability properties of the recycled leather using shaving scrap with antioxidant. Recycled leather sheets were manufactured by mixing shaving scrap and NB latex as a binder. HALS(Hindered Amine Light Stabilizer) and UVA(UV absorbers) were used as antioxidant. Mechanical properties such as hardness, tensile strength, elongation, tear strength and abrasion resistance were measured. Light aging resistance was evaluated using UV lamp and the degree of discoloration of the recycled leather sheets using a gray scale. In addition, to evaluate heat aging and UV aging, the degree of discoloration of the recycled leather sheets over time was measured using colorimeter. Washing fastness was evaluated on the degree of dyeing of recycled leather sheets for six type of multi-fiber woven fabrics (Acetate, Cotton, Nylon-66, Polyester, Acryl, Wool). To determine whether hazardous substances were detected in recycled leather sheets, the contents of arylamine and Cr 6⁺ were evaluated. As a result, when used in combination with antioxidant, the heat aging and light aging of recycled leather were improved and hazardous substance were not detected.

• Korean Chemical Engineering Research
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• v.50 no.6
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• pp.1076-1081
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• 2012

For the purpose of development of the latex suitable for latex modified concrete, experimental researches on the preparation of carboxylated styrene butadiene latex by the method of the two-step emulsion polymerization and application to concrete were performed. Sodium dodecylbenzene sulfonate and sodium salt of lauryl sulfonate were selected as anionic emulsifiers, and nonylphenoxy poly(ethyleneoxy) ethanols (n=10, 20, 40) as latex stabilizer. Potassium persulfate and sodium bisulfite were used as redox initiator, besides $Na_2HPO_4$ and $K_2CO_3$ as electrolytes. Polymerization recipe of latex suitable for latex modified concrete were suggested from the experimental researches on the effects of anionic emulsifiers and their concentration on the polymerization stability, and the effect of electrolytes concentration on the particle size of latex. Physical properties, such as slump, air contents, compressive and flexural strength, of latex prepared by suggested polymerization recipe were examined. The experimental results showed that latex modified concrete satisfied the quality standards in slump and air contents. Furthermore, it was turned out that the compressive and the flexural strength of latex modified concrete with 28 days curing time showed appreciably improvements.