• Journal of the Korean Crystal Growth and Crystal Technology
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• v.1 no.1
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• pp.107-116
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• 1991

Fine $PbTiO_3$ Particles were synthesized from the $Pb(NO_3)_2$and $TiO(NO_3)_2$ solution by the spray pyrolysis method using the ultrasonic vibrator as a mist generator. The obtained particles were characterized. The mechanisms of particle formation were discussed in comparison with those if other particles, such as $BaTiO_3$, $ZnO_2$, ZnO ....., in the same spray pyrolysis process.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.05a
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• pp.151-152
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• 2009

We coated $TiO_2$ thin films on particles by a rotating cylindrical plasma chemical vapor deposition (PCVD) process and investigated the effects of various process variables on the morphology and growth of thin films. The polypropylene (PP) particles were rotated with the cylindrical PCVD reactor and they were coated with $TiO_2$ thin films uniformly by the deposition of thin mm precursors in the gas phase. The $TiO_2$ thin films were coated on the PP particles uniformly and the thickness of thin films almost proportional to the deposition time. The $TiO_2$ thin films grew more quickly on the PP particles with increasing rotation speed of the reactor. This study shows that a rotating cylindrical PCVD reactor can be a good method to coat high-quality $TiO_2$ thin films uniformly on particles.

• Journal of the Korean Ceramic Society
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• v.55 no.2
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• pp.140-144
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• 2018

$ZnO/TiO_2$ nanocomposites were synthesized via a modified sol-gel technique by incorporating 30 and 70 wt% $TiO_2$ nanopowder into a ZnO sol-gel matrix. Zinc acetate dihydrate was used as the ZnO precursor and de-ionized water as the solvent, while titanium oxysulfate was employed for the synthesis of $TiO_2$ nanopowder. The synthesized $ZnO/TiO_2$ nanocomposites were characterized by x-ray diffraction, UV-vis spectroscopy, scanning electron microscopy, and transmission electron microscopy. The $ZnO/TiO_2$ nanocomposites showed both the ZnO (wurtzite) and $TiO_2$ (anatase) phases. The average ZnO crystallite size of the $ZnO/TiO_2$ nanocomposites was found to be about 26.3 nm. The TEM results confirmed that spherical $TiO_2$ particles were embedded in the ZnO matrix. $TiO_2$ particles attached onto the rod-like ZnO particles were also observed. The $ZnO/TiO_2$ nanocomposites exhibited optical absorption properties superior to those of pure ZnO and $TiO_2$.

• Journal of Industrial Technology
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• v.21 no.B
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• pp.21-26
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• 2001

In this study, the effects of crystalinity, composition and particle size of $TiO_2$ catalysts on the degradations of humic acid in aqueous solution was assessed using the commercially avaliable $TiO_2$ particles. Photocatalytic oxidations of humic acid (HA, Aldrich Co.) solution were carried out in case of adding different types of $TiO_2$ catalysts and their decomposition efficiencies were analyzed with respect to pH, DOC and UV absorbances values for the HA solutions and compared one another. The experimental results showed that $TiO_2$ particles(Degussa P-25) mixed with anataze and rutile gave the highest degradation efficiencies, respectively and much lower degradation efficiency in $TiO_2$ paticles of rutile only type. In comparing among ST series of anataze types, it was observed that the degradation efficiencies generally were increased with increasing $TiO_2$ contents and surface area of the particles. Higher degradation efficiency of HA was also found in zeolite type(D-TZ) of $TiO_2$ paticles compared with hydroxyapatite type (D-TH) of $TiO_2$ particles.

• Tribology and Lubricants
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• v.39 no.2
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• pp.72-75
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• 2023

Silicon carbide (SiC) is used as a substrate material for power semiconductors; however, SiC chemical mechanical polishing (CMP) requires considerable time owing to its chemical stability and high hardness. Therefore, researchers are attempting to increase the material removal rate (MRR) of SiC CMP using various methods. Mixed-abrasive CMP (MAS CMP) is one method of increasing the material removal efficiency of CMP by mixing two or more particles. The aim of this research is to study the mathematical modeling of the MRR of MAS CMP of SiC with SiO₂ and TiO₂ particles. With a total particle concentration of 32 wt, using 80-nm SiO₂ particles and 25-nm TiO₂ particles maximizes the MRR at 8 wt of the TiO₂ particle concentration. In the case of 5 nm TiO₂ particles, the MRR tends to increase with an increase in TiO₂ concentration. In the case of particle size 10-25 nm TiO₂, as the particle concentration increases, the MRR increases to a certain level and then decreases again. TiO₂ particles of 25 nm or more continuously decreased MRR as the particle concentration increased. In the model proposed in this study, the MRR of MAS CMP of SiC increases linearly with changes in pressure and relative speed, which shows the same result as the Preston's equation. These results can contribute to the future design of MAS; however, the model needs to be verified and improved in future experiments.

• Journal of the Korean Ceramic Society
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• v.42 no.9 s.280
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• pp.607-612
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• 2005

The effect of MgO diluents in combustion synthesis of $TiB_2$ nano particles was investigated. The reaction $TiO_2\;+\;B_2O_3\;+\;xMg\;{\rightarrow}\;TiB_2\;+\;5MgO$ was used to synthesize $TiB_2$ nano particles. The combustion velocity was measured to examine the relation between the reaction temperature and the morphologies of particles. The diluent MgO did not react with the reactants and played a role to decrease combustion temperature. As the MgO diluents contents increased, the particles with the smaller size and the narrower size distribution were synthesized. At the condition of 6 mole of MgO, the combustion wave velocity was about 5 cm/see and the synthesized particles showed the size of 60 nm with narrow size distribution.

• Journal of Industrial Technology
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• v.22 no.A
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• pp.255-260
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• 2002

We prepared the nano-sized $TiO_2$ particles by the diffusion flame reactor and investigated the effects of several process variables on the generation and transport properties of $TiO_2$ particle. As the length from the tip of diffusion flame reactor increases, the size of $TiO_2$ particle increases by the coagulation between particles. The structure of $TiO_2$ particles prepared is almost found to be anatase. It was found that the $TiO_2$ particle size depends more largely on the change of reactor temperature than on the change of inlet $TiCl_4$ concentration.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.6
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• pp.495-500
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• 2009

The ceramic($BaTiO_3$)-polymer(epoxy) composites have been widely investigated as dielectric materials for embedded capacitors in printed circuit boards (PCBs). The dielectric properties of $BaTiO_3$/epoxy composites prepared using the agglomerated $BaTiO_3$ particles were investigated in the present study. The dielectric constants of the composites prepared using the agglomerated $BaTiO_3$ particles were about 2 times higher than those of the composites with the dispersed $BaTiO_3$ particles. The insulation resistance of the composites prepared using the agglomerated $BaTiO_3$ particles were lower than those of the composites with dispersed $BaTiO_3$ particles. As a result, there is tradeoff between high dielectric constant and insulation resistance in the $BaTiO_3$/epoxy composites. So it is important to select proper agglomerated or dispersed $BaTiO_3$ particles in accordance with needs.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.568-571
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• 2008

A novel self-humidifying composite membrane for the proton exchange membrane fuel cell (PEMFC) at low humidity condition was developed. The Pt/$TiO_2$ catalyst particles were synthesized via supercritical impregnation methods. Pt precursor was dissolved in supercritical carbon dioxide and impregnated onto $TiO_2$ particles. Pt precursors were platinum(II) acetylacetonate, Dimethyl(1,5-cyclooctadiene) platinum(II) and we controlled the ratio of Pt to $TiO_2$. The impregnated Pt precursor was converted to $TiO_2$ supported Pt nanoparticle under various reducing conditions. Pt/$TiO_2$ catalyst particles were dispersed uniformly into the Nafion solution, and then Pt/$TiO_2$/Nafion composite membrane was prepared using solution-cast method. The self-humidifying composite membrane could minimize membrane conductivity loss under dry conditions due to the presence of catalyst and hydrophilic Pt/$TiO_2$ particles. To optimize the performance of MEA, amount of ionomer loading was controlled. And mixed catalysts were used. The cell performance of MEA was obviously improved under dry conditions at $65^{\circ}C$.

• Environmental Analysis Health and Toxicology
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• v.22 no.3
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• pp.189-196
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• 2007

[ $TiO_2$ ] is widely used because it is non-toxic. Recently, however, nanometer size $TiO_2$ particles (P-25) have been produced and used to increase the photo catalysis efficiency. Nanometer-sized $TiO_2$ is efficient, but due to its small size ($20{\sim}30\;nm$), it can flow into ecosystems and into cells. Thus, it may affect human health. Additionally, $TiO_2$ can produce a second contaminant, OH-radical, which is a health risk for all living organisms during photo degradation reaction. Hence, when nanometer-sized $TiO_2$ flows into natural streams and attaches to living organisms, it will create health risks. We investigated the biological toxicity of this condition in zebrafish embryos. We observed abnormal morphology, hatching rate, and measured the catalase activity to determine anti-oxidation at 100 post fertilization hours. Zebrafish were somewhat affected by $TiO_2$ nanometer sized particles under UV-A (a condition similar to sunlight). Powdered $TiO_2$ is toxic to the zebrafish fly. Even without light, $TiO_2$ particles attached to embryos and flies, having an effect on both.