• Tribology and Lubricants
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• v.25 no.6
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• pp.404-408
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• 2009

In this paper, the relationship between the material removal rate and the interfacial mechanical properties at particle-surface contact situation, which can be seen in an abrasive machining process using micro/nano-sized particles, was discussed. Friction and stiffnesses were measured experimentally on an atomic force microscope (AFM) by using colloidal probes which have a silica colloid particle in place of tip to simulate a particle-flat surface contact in an abrasive machining process. From the experimental investigation and theoretical contact analysis, the interfacial contact properties such as lateral stiffness of contact, friction, the material removal rate were presented with respect to some of material surfaces and the relationship between the properties as well.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.5
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• pp.803-807
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• 2008

A making process of DSC(dye sensitized solar cell) was presented. In general, Photo electrodes of DSC was made by using colloid paste of nano $TiO_2$ and processing of Doctor-blade printing and high temperature sintering for porous structure. These methods lead to cracks on $TiO_2$ surface and ununiform of $TiO_2$ thickness. This phenomenon is one factor that makes low efficiency to cells. After $TiO_2$ printing on TCO glass, a physical vibration was adapted for reducing ununiform of $TiO_2$ thickness. And a thermal treatment at low temperature(under $75^{\circ}C$) was adapted for reducing cracks on $TiO_2$ surface. In this paper, we have designed and manufactured an ultrasonic circuit (100W, frequency and duty variable) and a thermal equipment. Then, we have optimized forcing time, frequency and duty of ultrasonic irradiation and thermal heating for surface treatment of photo-electrode of DSC. In I-V characteristic test of DSC, ultrasonic and thermal treated DSC shows 19% improved its efficiency against monolithic DSC. And it shows stability of light-harvesting from drastically change of light irradiation test.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.538-541
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• 2008

The carbon laden suspensions in water with no surfactants have poor stability caused by the hydrophobic layer of particles. In this study, the water-based carbon nano colloide(CNC) was successfully produced using electro-chemical one-step method without agent. The properties of CNC were characterized by using various techniques such as particle size analyzer, TEM, FT-IR, turbidity meter, viscometer, and transient hot-wire method. The average size of the suspended in the CNC was 15 nm in diameter. The thermal conductivity of CNC compared with water was increased up to 14% with 4.2wt% concentration. The CNC was stable over 600hr. The enhanced colloidal stability of CNC may be caused by the chemical structures, such as, hydroxide and carboxyl groups formed in outer atomic layer of carbon, which (i) made the carbon nanofparticles hydrophilic and (ii) prevented the aggregation among nanoparticles.

• Proceedings of the KIEE Conference
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• 2007.11a
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• pp.98-99
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• 2007

This study has successfully demonstrated the direct fabrication of polymer resistors using ink-jet printing technology as an alternative patterning to traditional photolithography. The polymer resistors were fabricated just by two layer processes using a ink-jet printer (DMP-2800, Fujifilm Dimatix). First, resistive materials was patterned by a ink-jet printing with the desired width and length. Next, resistor fabrication was completed by printing metal contact pads on the both sides of the polymer resistor. We used poly (3,4-ethylene dioxythiophene) poly(styrenesulfonate)(PEDOT:PSS) for the resistor material and a nano-sized silver colloid for the metal contact pads. We characterized the electrical properties of PEDOT:PSS by measuring sheet resistance and specific resistance on a glass substrate. From analysis of the measured resistances, the electrical resistances of the polymer resistors linearly increased as a function of printed width and length of resistors. The accuracy of the fabricated polymer resistor showed about $0.6{\sim}2.5%$ error for the same dimensions.

• Analytical Science and Technology
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• v.21 no.3
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• pp.237-243
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• 2008

Nano core shell structures of $TiO_2$ particles coated on surface of ZnO nanoparticles were prepared by the polymerized complex and sol-gel method. The average particle size of ZnO by the polymerized complex method showed 100 nm and the average particle size of $TiO_2$ by the sol-gel method showed below 10 nm. The average particle size of $ZnO@TiO_2$ nano core shell struture represented about 150 nm. The agglomeration between the ZnO particles using the polymerized complex method was highly controlled by the uniform absorption of $TiO_2$ colloid on the spherical ZnO surfaces. The driving force of heterogeneous bonding between ZnO and $TiO_2$ was induced by the Coulomb force. The ZnO and $TiO_2$ particles electrified with + and - charges, respectively, resulted in strong bonding by the difference of iso-electric point (IEP) when they laid neutrality pH area, depending on the heterogeneous surface electron electrified by the different zeta potential on the pH values.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.772-779
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• 2016

Silver nanoparticles were prepared by reacting silver nitrate and trisodium citrate in an aqueous solution. Their size and shape were investigated by scanning electron microscopy (SEM). The synthesis was carried with different silver nitrate concentration, addition of TSC, solvent, surfactant, ultrasonication, and dispersing agent. With higher concentration of silver nitrate or TSC, the particles became large or agglomerated. The SEM results showed that the nanoparticles have spherical and pseudospherical shape with a narrow size distribution. The hydrophobic solvent did not affect the dispersibility, but the hydrophilic solvent enhanced it. The addition of HPMC surfactant caused the size to increase (50-100 nm) with non-uniform shapes and partial agglomeration. The dispersibility was significantly improved by ultrasonication for over 3 hours after the addition of a dispersing agent. Complete dispersion was achieved by adding the dispersant, and the nanoparticle sizes were as follows: 30-40 nm (BYK-182) < 42-78 nm (BYK-192) < 51-113 nm (BYK-142). The nanoparticles were 38.45-46.28 nm after the addition of 2-4 wt% TSC in 0.002 M silver nitrate solution.

• Journal of Environmental Health Sciences
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• v.36 no.6
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• pp.496-501
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• 2010

Fish pathogenic bacteria are a considerable danger of farmed fish and a source of economic loss in the fish farming industry. In this study, $Nanoxil^{(R)}$ was compared to hydrogen peroxide and a silver colloid in terms of disinfection efficacy against E. tarda, V. anguillarum and S. iniae. A bactericidal efficacy test conducted by a broth dilution method was used to determine the lowest effective dilution of the disinfectant following exposure to test bacteria for 30 min at $4^{\circ}C$. $Nanoxil^{(R)}$ and test bacteria were diluted with distilled water (DW), hard water (HW) or an organic matter suspension (OM) according to the treatment condition. Under the OM condition, the bactericidal activity of $Nanoxil^{(R)}$ against E. tarda exhibited a lowered efficacy compared to that under the DW and HW conditions. $Nanoxil^{(R)}$ at 500 fold (dilutions on) under all of the conditions demonstrated a high bactericidal efficacy against S. iniae. As $Nanoxil^{(R)}$ possess bactericidal efficacy against fish pathogenic bacteria such as E. tarda, V. anguillarum and S. iniae, this disinfectant solution can be used to limit the spread of fish bacterial diseases.

• Advances in nano research
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• v.3 no.2
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• pp.97-109
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• 2015

Citrate ion is a commonly used reductant in metal colloid synthesis, undergoes strong surface interaction with silver nanocrystallites. The slow crystal growth observed as a result of the interaction between the silver surface and the citrate ion makes this reduction process unique compared to other chemical and radiolytic synthetic methods. The antimicrobial effects of silver (Ag) ion or salts are well known, but the effects of citrate coated Ag nanoparticles (CAgNPs) are scant. Herein, we have isolated biofilm causative bacteria and fungi from drinking water PVC pipe lines. Stable CAgNPs were prepared and the formation of CAgNPs was confirmed by UV-visible spectroscopic analysis and recorded the localized surface plasmon resonance of CAgNPs at 430 nm. Fourier transform infrared spectroscopic analysis revealed C=O and O-H bending vibrations due to organic capping of silver responsible for the reduction and stabilization of the CAgNPs. X-ray diffraction micrograph indicated the face centered cubic structure of the formed CAgNPs, and morphological studies including size (average size 50 nm) were carried out using transmission electron microscopy. The hydrodynamic diameter (60.7 nm) and zeta potential (-27.6 mV) were measured using the dynamic light scattering technique. The antimicrobial activity of CAgNPs was evaluated (in vitro) against the isolated fungi, Gram-negative and Gram-positive bacteria using disc diffusion method and results revealed that CAgNPs with 170ppm concentration are having significant antimicrobial effects against an array of microbes tested.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.304-304
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• 2010

The study on the catalytic oxidation of carbon monoxide (CO) to carbon dioxide ($CO_2$) using the noble metals has long been the interest subject and the recent progress in nanoscience provides the opportunity to develop new model systems of catalysts in this field. Of the noble metal catalysts, we selected ruthenium (Ru) as metal catalyst due to its unusual catalytic behavior. The size of colloid Ru NPs was controlled by the concentration of Ru precursor and the final reduction temperatures. For catalytic activity of CO oxidation, it was found that the trend is dependent on the size of Ru NPs. In order to explain this trend, the surface oxide layer surrounding the metal core has been suggested as the catalytically active species through several studies. In this poster, we show the influence of surface oxide on Ru NPs on the catalytic activity of CO oxidation using chemical treatments including oxidation, reduction and UV-Ozone surface treatment. The changes occurring to UV-Ozone surface treatment will be characterized with XPS and SEM. The catalytic activity before and after the chemical modification were measured. We discuss the trend of catalytic activity in light of the formation of core-shell type oxide on nanoparticles surfaces.

• Journal of the Korean Ceramic Society
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• v.38 no.9
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• pp.853-859
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• 2001

The dispersion stability of nano $Y_2O_3-CeO_2$ system was investigated using colloid surface chemistry. Green body of $Y_2O_3$ doped $CeO_2$ was prepared by slip casting in and aqueous system. The dispersion stability of suspension between powders and organic additive was accomplished through electrokinetic behavior of suspension, which was done by ESA apparatus. The dynamic mobility of particles was enhanced when the anionic dispersant of the amount of 1wt% was added. The dissolution of $Y^{3+}$ ion in suspension occurred in the acidic region so that pH value in slurries did not move to below 7.0. In the $CeO_2-Y_2O_3$ system, optimal preparation of suspension was made after adding the anionic dispersant as the amount of 1wt% and pH value of 11.0, and then slip-cast and sintered at 1400$^{\circ}$C, 2 hrs. It appeared relative density of >98% and homogeneous distribution of Y element in depth direction as well as in the microstructure of surface.