• Applied Chemistry for Engineering
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• v.20 no.4
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• pp.402-406
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• 2009

$TiO_2$ thin films were surface-modified with atmospheric plasma and their photocatalytic activities were evaluated. The films were deposited on glass plates by dip-coating in a $TiO_2$ sol-gel solution and sintered at various temperatures for various times. Nitrogen plasma was used for the modification and the experiments were carried out varying operational parameters such as discharge power and treatment time. Photocatalytic activity was evaluated based on the degradation efficiency of methylene blue (MB) under irradiation of UV-A and fluorescent light. According to XPS analysis, a little amount of nitrogen was found to be doped in the film surface after the modification. As a result, photocatalytic activity increased under irradiation of UV-A and fluorescent light, especially fluorescent light.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.6
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• pp.457-460
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• 2005

Nano-sized titanium oxide and zirconium oxide powders were synthesized by hydrolysis of titanium isopropoxide $[Ti(OC_3H7)_4]$ and zirconium tetrachloride ($ZrC1_4$) via a sol-gel technique. Lead titanate powders were prepared by mixing $TiO_2$ precursors with PbO slurry made with dilute $NH_4OH$. Lead zirconate titanate powders were, then, synthesized by mixing $PbTiO_3$ with $ZrO_2$ powders. The goal of this research was to obtain the $PbZrTiO_3(PZT)$ powders and sintering these powders at low temperature. The $PbTiO_3$ and PZT powders after firing were analyzed by X-ray diffraction(XRD) and transmission electron microscopy(TEM) was utilized to observe the shape and size of the synthesized nano-particles. In the XRD pattern, the well-crystallized PZT phase could be obtained in consequence of firing at $900^{\circ}C$. SEM micrographs also showed that grains of PZT were relatively well grown with the size of the range of $2{\~}4{\mu}m$. The densified perovskite structure of $PbZrTiO_3$ could be obtained by sintering at temperature as low as $900^{\circ}C$. Characterization of the samples showed improved piezoelectric properties.

• Journal of the Korean Applied Science and Technology
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• v.29 no.3
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• pp.377-392
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• 2012

It has been known that small solid particles act as a stabilizer in pickering emulsion system. In this study, we successfully prepared stable pickering emulsion in n-hexylalcohol and water system with $TiO_2$ whose surface was treated by alkylsilane. The optimum condition to prepare pickering emulsion stabilized by $TiO_2$ particles was determined by amount of $TiO_2$ particles and ratio of water and oil phase. The type of pickering emulsion was dependent on wettability of particles for water and n-hexylalcohol. When the amount of $TiO_2$ particles increased up to 5.00 wt%, the stability of pickering emulsion was showed to be improved. The most stable pickering emulsion was prepared in the case of W/O type which has the ratio of oil and water phase (3 : 7). We tried to prepare porous $SiO_2-TiO_2$ composite pigments using a pickering emulsion as template at the optimal condition. Porous pigments were synthesized with Ludox HS-30 as an inorganic material by sol-gel process. The characteristics and shape of porous pigments were measured by optical microscope, SEM, BET, XRD and EDS.

• Journal of the Korean Ceramic Society
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• v.39 no.6
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• pp.582-588
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• 2002

IrO$_2$-RuO$_2$ films were deposited on plasma sprayed TiO$_2$ buffer layer above Ti metal by sol-gel and dip-coating method. Organic vehicle (ethyl cellulose and $\alpha$-terpineol) and glass frit were added to improve adherence of the coatings. Taguchi method and L$_{18}$ (2$^1$$\times$3$^{7}$ ) orthogonal arrays were evalvated in terms of current density to determine the optimal combination of levels of factors that best satisfy the bigger is better quality characteristic. The observed conditions were as fellows: ethyl cellulose (100 cp), drying temperature and time (17$0^{\circ}C$,20 min), heat treatment temperature and time (75$0^{\circ}C$,10 min), the weight ratio of IrO$_2$-RuO/powders to glass frit (99:5), final heat treatment time (120 min) and flow rate of air (5 sccm), respectively. ANOVA analysis suggested that the influence of the factors within $\alpha$= 0.1 was significant with a 90% confidence level.

• Clean Technology
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• v.28 no.1
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• pp.18-23
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• 2022

Using air as an insulator due to its low heat transfer coefficient has been studied and has been widely commercialized to save energy in the field of thermal insulation technology. In this study, we analyzed the heat insulating effect of hollow silica nanoparticles mixed in non-uniform size, and the maximum heat insulating efficiency of these particles given the limited number of particles that can be mixed with a medium such as paint. The hollow silica nanoparticles were synthesized via a sol-gel process using a polystyrene template in order to produce an air layer inside of the particles. After synthesis, the particles were analyzed for their insulation effect according to the size of the air layer by adding 5 wt % of the particles to paint and investigating the thermal insulation performance by a heat transfer experiment. When mixing the particles with white paint, the insulation efficiency was 15% or higher. Furthermore, the large particles, which had a large internal air layer, showed a 5% higher insulation performance than the small particles. By observing the difference in the insulation effect according to the internal air layer size of hollow silica nanoparticles, this research suggests that when using hollow particles as a paint additive, the particle size needs to be considered in order to maximize the air layer in the paint.

• Applied Chemistry for Engineering
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• v.34 no.1
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• pp.36-44
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• 2023

Core-shell TiO₂/Ag nanoparticles were synthesized by a modified sol-gel process and the reverse micelle method using acetoxime as a reducing agent in water/dodecylbenzenesulfonic acid (DDBA)/cyclohexane. The structure, shape, and size of the TiO₂/Ag nanoparticles were investigated using X-ray diffraction (XRD), UV-visible spectroscopy, scanning electron microscope (SEM), transmission electron microscope (TEM), and thermogravimetric analysis (TGA). The size of TiO₂/Ag nanoparticles could be controlled by changing the [water]/[DDBA] molar ratio values. The size and the polydispersity of TiO₂/Ag nanoparticles increased when the [water]/[DDBA] molar ratio rose. The resultant Ag nanoparticles over the anatase crystal TiO₂ nanoparticles exhibited a strong surface plasmon resonance (SPR) peak at about 430 nm. The SPR peak shifted to the red side with the increase in nanoparticle size. Conductive pastes with 70 wt% TiO₂/Ag nanoparticles were prepared, and the pastes were coated on the PET films using a screen-printing method. The printed paste films of the TiO₂/Ag nanoparticles demonstrated greater surface resistance than conventional Ag paste in the range of 405~630 μΩ/sq.