• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.166-169
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• 2003

In this study, we evaluated the characteristics by the addition of 3 different kinds of nonionic surfactant to improve the dispersion stability of slurries. Slurry stability is an issue in any industry in which settling of particles can result in poor performance. So we observed the variation of particle size and settling rate when the concentration and addition time of surfactant are changed. When the surfactant is added after milling process, the particle size and pH became low. It is supposed that the particle agglomeration was disturbed by adsorption of surfactant on alumina abrasive. The settling rate was relatively stable when nonionic surfactant is added about 0.1~1.0 wt%. When molecular weight(MW) is too small like Brij 35, it was appeared low effect on dispersion stability. Because it can't prevent coagulation and subsequent settling with too small MW. The proper quality of MW for slurry stability was presented about 500,000. Consequently, the addition of nonionic surfactant to alumina slurry has been shown to have very good effect on slurry stabilization. If we apply this results to copper CMP process, it is thought that we will be able to obtain better yield.

• Korea-Australia Rheology Journal
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• v.12 no.3_4
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• pp.143-149
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• 2000

In this article, we considered shear-induced microstructure and rheological behavior of micellar solutions of cationic surfactant, cetylpyridinium chloride (CPC) in the presence of a structure-forming additive, sodium salicylate (NaSal). Shear viscosity, shear moduli and flow birefringence were measured as functions of the surfactant and additive concentrations. In the presence of NaSal, the micellar solution exhibited the non-linear rheological behavior due to the formation of supramolecular structures when the molar ratio of NaSal to CPC exceeded a certain threshold value. Flow birefringence probed the change in micelle alignment under shear flow. At low shear rates, the flow birefringence increased as the shear rate increased. On the other hand, fluctuation of flow birefringence appeared from the shear rate near the onset of shear thickening, which was caused by shear-induced coagulation or aggregation. These results were confirmed by the SEM images of in situ gelified micelle structure through sol-gel route.

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.2
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• pp.145-148
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• 2008

Cationic surfactant can be used as cosmetics and chemical dispersants. The variation of critical micelle concentration (CMC) with temperature over the range $40^{\circ}C$ to $60^{\circ}C$ for N-octadecyl pyridinium bromide was measured by drop methods. Thermodynamic quantities such as free energy, enthalpy, entropy and heat capacity for micellization of N-octadecyl pyridinium bromide in water were calculated by fourth-degree polynominal equation In the result, free energy change was decreased generally by the increment of temperature.

• Journal of Industrial and Engineering Chemistry
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• v.67
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• pp.123-131
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• 2018

Using mixed nonionic surfactants Span/Tween, we investigated the effects of HLB value on the O/W emulsion stability and rheological behaviors. In this study, MS-01 (Span 60 & Tween 60) and MS-02 (Span 80 & Tween 80) was used as mixed nonionic surfactants. We considered required HLB value 10.85 and selected corresponding HLB value range 8-13. The droplet size distributions, droplet morphology, rheological properties, zeta-potential and creaming index of the emulsion samples were obtained to understand the mechanism and interaction of droplets in O/W emulsion. The results indicated that optimal HLB number for O/W emulsions was 10.8 and 10.7, while using MS-01 surfactant and MS-02 surfactant respectively. MS-01 (HLB = 10.8) sample and MS-02 (HLB = 10.7) sample showed smallest droplet size and highest zeta-potential value. Rheological properties are measured to understand rheological behaviors of emulsion samples. All emulsion samples showed no phase separation until 30 days storage time at $25^{\circ}C$.

• Journal of Soil and Groundwater Environment
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• v.13 no.1
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• pp.32-42
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• 2008

A surfactant recovery and reuse process by selective adsorption with activated carbon was proposed to reduce surfactant cost in a soil washing process. Mathematical model simulation was performed for the whole process, which consists of soil washing, soil recovery, and soil re-washing. The optimal range of surfactant dosage was $6{\sim}10$-fold critical micelle concentration in soil. The efficiency of surfactant reuse process was decreased with increasing the dosage of activated carbon. Effectiveness factor for activated carbon significantly altered the efficiency of the reuse process unlike effectiveness factor for soil. Total requirement of surfactant was reduced to 20-30% with the reuse process compared to the conventional soil washing process. The contamination of wastewater after soil washing was reduced with the reuse process. This mathematical model can be used to estimate performance of the whole process of soil washing including surfactant recovery and to obtain optimal ranges of operating conditions without extra labor-intensive experimental works.

• Korean Chemical Engineering Research
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• v.49 no.6
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• pp.739-744
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• 2011

Activated carbon SCR(CSCR) catalyst that is used to remove $NO_x$ in exhaust gas including boron discharged from the production process of liquid crystal display(LCD) shows deactivation when boron is deposited to block the pores within the catalyst or to cover its active sites. The spent carbon catalyst is regenerated by washing with various surfactants, drying and calcination. For comparison of the physical and chemical properties before and after the regeneration with the variables, type of surfactants and calcination condition, element analysis by ICP, $N_{2}$ adsorption were conducted. $DeNO_{x}$ in SCR with $NH_3$ was carried out in a fixed bed reactor at $120^{\circ}C$. The activated carbon catalyst regenerated through washing with a non-ionic surfactant in $H_{2}O$ at $90^{\circ}C$ and calcination under $N_{2}$ gas at $550^{\circ}C$ shows similar level of surface area and $NO_x$ removal efficiency with those of fresh catalyst.

• Journal of Powder Materials
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• v.20 no.6
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• pp.479-486
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• 2013

In the present work, physicochemical treatments were introduced for de-aggregation and stable dispersion of detonation nanodiamonds (DND) in polar solvents. The DNDs in water exhibited a particle size of 138 nm and high dispersion stability without particular treatment. However, the DNDs in ethanol were severely aggregated to several micrometers in size and showed poor dispersion stability with time. To break down aggregates of DNDs and enhance the dispersion stability of them in ethanol, mechanical force and chemical surfactant were introduced as functions of zirconia ball size, kind of surfactant and amount of surfactant added. From the analyses of average particle size and Turbiscan results, it was suggested that the size of DNDs in ethanol can be reduced by only mechanical force; however, the DNDs were re-aggregated due to high surface activity. The long-term dispersion stability can be achieved by applying mechanical force to break down the aggregates of DNDs and by preventing re-aggregation of them using proper surfactant.

• Clean Technology
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• v.10 no.3
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• pp.149-158
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• 2004

Supercritical carbon dioxide is often promoted as an environmentally friendly solvent having useful properties for a wide range of technical and chemical processes. But the limited ability of $CO_2$ to dissolve polar or non-volatile compounds represents a major drawback in many processes, because the key components will often fail to form homogeneous solution under practical conditions. The design of $CO_2$ soluble ($CO_2$-philic) surfactant to aid this process is therefore paramount in these areas, which has advanced the "greening" of demanding yet important applications in dyeing, cleaning of fibers and texiles, polymerization and polymer processing, photoresist removal, electroplating, and chemical synthesis.

• Applied Chemistry for Engineering
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• v.10 no.4
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• pp.537-542
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• 1999

Removal of sulfur compounds in the petroleum products is essential for the prevention of sulfur oxides. However, conventional methods involving catalytic reactions are found to have some limitations in complete removal of harmful sulfur compounds and to require relatively high cost. Recently, desulfurization process using microorganisms is known to be promising in terms of excellent sulfur removal efficiency and reasonably low treatment cost. For the biodesulfurization process to be effective, the solubilization of sulfur compounds into aqueous solution is a prerequisite. In this study, polyoxyethylene nonionic surfactants were used in order to enhance the solubilization of sulfur spectrophotometer. The solubilization of sulfur compounds was found to increase with temperature and to bo abruptly increased at above 1 wt % surfactant solutions. It was also observed that the longer the hydrophobic chain of the surfactant molecule, the higher solubilizing power of a nonionic surfactant. It was found that the Tergitol series surfactants showed higher solubilizing capacity than Neodol series presumably due to the disruption of the regular packing in the hydrocarbon region of the surfactant aggregates.

• Korean Chemical Engineering Research
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• v.43 no.1
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• pp.53-59
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• 2005

In this study, the supercritical electroplating was investigated by forming macroemulsion of electroplating solution using surfactant in supercritical $CO_2$. The fluorinated analogous AOT surfactant, sodium salt of bis (2,2,3,3,4,4,5,5-octafluoro-1-pentanol) sulfosuccinate which has both '$CO_2$ philic' chains and 'hydrophilic' head group was used as a surfactant, and Ni plate and Cu plate were used as the anode and the cathode, respectively. Electroplating was carried out in the conventional method and the supercritical macroemulsion and both results were compared. The supercritical electroplating was carried out in various concentration of surfactant such as 2, 4, 7 wt%, the volume ratio of Ni-plating solution to $CO_2$ was varied in the range of 10-70 vol%, and propane was used as a supercritical fluid instead of $CO_2$. According to the experimental results, the plated surface of Ni on Cu plate performed in supercritical macroemulsion was better than that, in conventional state. In the image of Ni surface plated on Cu plate in supercritical state, there were fewer pin-holes and pits comparing with that in the conventional process. The current and conductivity was increased as the volume ratio of Ni-plating solution to $CO_2$ was increased and the current and the amount of Ni plated on Cu plate were decreased as the concentration of surfactant become higher. In addition, in case of the continuous phase, using $CO_2$ was more effective than using $CO_2$.