• Journal of Powder Materials
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• v.25 no.4
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• pp.309-315
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• 2018

In the present work, we synthesize nano-sized ZnO, $SnO_2$, and $TiO_2$ powders by hydrothermal reaction using metal chlorides. We also examine the energy-storage characteristics of the resulting materials to evaluate the potential application of these powders to dye-sensitized solar cells. The control of processing parameters such as pressure, temperature, and the concentration of aqueous solution results in the formation of a variety of powder morphologies with different sizes. Nano-rod, nano-flower, and spherical powders are easily formed with the present method. Heat treatment after the hydrothermal reaction usually increases the size of the powder. At temperatures above $1000^{\circ}C$, a complete collapse of the shape occurs. With regard to the capacity of DSSC materials, the hydrothermally synthesized $TiO_2$ results in the highest current density of $9.1mA/cm^2$ among the examined oxides. This is attributed to the fine particle size and morphology with large specific surface area.

• Journal of the Korean Ceramic Society
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• v.39 no.1
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• pp.38-44
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• 2002

Dispersion stability of nano-sized rutile TiO$_2$powder with acicular typed primary particle produced by homogeneous precipitation process at low temperatures was studied in aqueous and non-aqueous media in the presence of various electrolytes. The zeta potential measurements have shown that the addition of electrolytes to aqueous and non-aqueous dispersion media leads to charge reversal on TiO$_2$particle surface. The electrostatic repulsive forces acting on between TiO$_2$particles dispersed in non-aqueous media were found to be significantly greater than that in aqueous media, which relate closely to the physical properties of the organic solvents, such as viscosities and dielectric constants. The pH values, the concentration of electrolytes and the valence of the ions have changed greatly the surface potential of TiO$_2$ particles and have governed the dispersion behavior of TiO$_2$particles virtually.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.5
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• pp.251-255
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• 2009

Nanocomposites based on coupling $TiO_2$ matrix with nanosized noble metals (Pt,Au) particles exhibited promising photoelectrode properties. The $M/TiO_2$ (M=Pt,Au) nanocomposite thin films were deposited on quartz and ITO glass substrates using a co-sputtering method. $TiO_2$ in rutile form is the dominant crystalline phase for as-deposited nanocomposite films. Along with heat treatment up to $600^{\circ}C$, XRD peaks of the rutile phase as well as those of noble metal increased in intensity and decreased in width, indicating the growth of crystallites. The anodic photocurrents of $M/TiO_2$ (M=Au,Pt) thin films were observed not only in the UV range but also in the visible light range. The photocurrent of the nanocomnosite films extended to the visible light region by dispersion of nano-sized noble metal in the $TiO_2$ matrix.

• 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 Microelectronics and Packaging Society
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• v.18 no.2
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• pp.57-62
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• 2011

The energy conversion efficiency of DSSCs (Dye-Sensitized Solar Cells) is dependent on the powder size, the structure, and the morphology of $TiO_2$ electrode. The higher efficiency is obtained with high surface area of the nanoanatase-$TiO_2$ powder adsorbed onto a lot more of the dye. Also, the enhancement of light scattering increases the efficiency with high adsorption of the dye. Powder size, crystalline phase, and shape of $TiO_2$ obtained by hydrothermal method have 15-20 nm, anatase and round. $TiO_2$ electrode has fabricated with the mixture of scattering $TiO_2$ particle with 0.4 ${\mu}m$ in nano-sized powder. Conversion efficiency of series of DSSCs was measured with volume fraction of scattering particle. Photovoltaic characteristics of DSSCs with 10% scattering particles are 3.51 mA for Jsc (short circuit current), 0.79 V for Voc(open circuit potential), filling factor 0.619 and 6.86% for efficiency. Jsc was improved by 11% and enhancement of efficiency by 0.77% compared with that of no scattering particles. The confinement of inserted light by light scattering particles has more increase of the injection of exiton(electron-hole pair) and decrease of moving path in electron. Efficiencies of DSSCs with more than 10% for scattering particles have reduced with increasing the pore in the $TiO_2$ electrode.

• Advances in nano research
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• v.13 no.1
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• pp.13-28
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• 2022

The pumpability of the grouts is significant issue in concept of the rheological and workability properties during penetrating to voids and cracks. To improve the fluidity features of the grout mixes, the usage of Colloidal Nano Particular Powders (CNPPs) with mineral additives such as fly ash (FA) can contribute. Therefore, the main purpose of this study can be explained as investigating the usage effects of four types of Colloidal Nano Particular Powders (n-TiO₂, n-ZnO, n-Al₂O₃ and n-SiO₂) as nano additives on the rheological, workability and bleeding properties of cement-based grout incorporated with fly as. Test results showed that the usage of FA in the grout samples positively contribute to increase on the fluidity of the grout samples as expected. The dilatant behavior was observed from the results for all mixes. Observing the effect of nano-sized additives in such cement-based grout mixtures with high fluidity has presented remarkable effects in this study.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.99-99
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• 2010

Polymer nanocomposite has been attracting much attention as a new insulation material, since homogeneous dispersion of nm-sized inorganic fillers can improve various properties significantly. In this paper, various kinds of epoxy based nanocomposites were made and AC breakdown strength of Nano-TiO2 and micro-silica filler mixture of epoxy based composites were studied by sphere to sphere electrode. Moreover, nano- and micro-filler combinations were adopted as an approach toward practical application of nanocomposite insulation materials. Nano-TiO2 particle size is about 10nm and composites ratio was resin (100) : hardener (82) : accelerator (1.5). AC breakdown test was performed at room temperature (25 [$^{\circ}C$], 80 [$^{\circ}C$] and 100 [$^{\circ}C$] in the vicinity of Tg (90[$^{\circ}C$]). And thermal conductivity were measured by ASTM-D5470.

• Journal of Powder Materials
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• v.20 no.5
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• pp.376-381
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• 2013

Spherical Ti-6Al-4V powders in the size range of 250 and 300 ${\mu}m$ were uniformly doped with nano-sized hydroxyapatite (HAp) powders by Spex milling process. A single pulse of 0.75-2.0 kJ/0.7 g of the Ti-6Al-4V powders doped with HAp from 300 mF capacitor was applied to produce fully porous and porous-surfaced Ti-6Al-4V implant compact by electro-discharge-sintering (EDS). The solid core was automatically formed in the center of the compact after discharge and porous layer consisted of particles connected in three dimensions by necks. The solid core increased with an increase in input energy. The compressive yield strength was in a range of 41 to 215 MPa and significantly depended on input energy. X-ray photoelectron spectroscopy and energy dispersive x-ray spectrometer were used to investigate the surface characteristics of the Ti-6Al-4V compact. Ti and O were the main constituents, with smaller amount of Ca and P. It was thus concluded that the porous-surfaced Ti-6Al-4V implant compacts doped with HAp can be efficiently produced by manipulating the milling and electro-discharge-sintering processes.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.440-441
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• 2006

Several titanate powders ($Al_2TiO_5,\;SrTiO_3$, etc.) were synthesized by an ethylene glycol solution route. Titanium isopropoxide and nitrate salts were dissolved in stoichiometric proportions in liquid-type ethylene glycol without any precipitation. The parent precursor sols were dried to porous gels, and then the gels were calcined and crystallized. All synthesized titanate powders had stable crystallization behavior at low temperature and high specific surface area after a simple ball-milling process. A three-component PZT $(Pb(Zr_{0.52}{\cdot}Ti_{0.48})O_3)$ powder was also synthesized successfully by the ethylene glycol method. In this study, the characteristics of the multi-component titanate powders by the ethylene glycol method are examined.

• Environmental Analysis Health and Toxicology
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• v.26
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• pp.3.1-3.6
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• 2011

Objectives: Titanium dioxide ($TiO_2$), a common nanoparticle widely used in industrial production, is one of nano-sized materials. The purpose of this study was to determine the acute and chronic toxicity of $TiO_2$ using different size and various concentrations on Daphnia magna. Methods: In the acute toxicity test, four concentrations (0, 0.5, 4, and 8 mM) for $TiO_2$ with 250 or 500 nm and five concentrations (0, 0.25, 0.5, 0.75, and 1 mM) for $TiO_2$ with 21 nm were selected to analyze the toxic effect to three groups of ten daphnia neonates over 96 hours. In addition, to better understand their toxicity, chronic toxicity was examined over 21 days using 0, 1, and 10 mM for each type of $TiO_2$. Results: Our results showed that all organisms died before the reproduction time at a concentration of 10 mM of $TiO_2$. In addition, the exposure of anatase (21 nm) particles were more toxic to D. magna, comparing with that of anatase (250 nm) and rutile (500 nm) particles. Conclusions: This study indicated that $TiO_2$ had adverse impacts on the survival, growth and reproduction of D. magna after the 21days exposure. In addition, the number of test organisms that were able to reproduce neonates gradually were reduced as the size of $TiO_2$ tested was decreased.