• Applied Chemistry for Engineering
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• v.18 no.2
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• pp.183-187
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• 2007

$SiO_2/TiO_2$ core-shell particles with controlled shell thickness were prepared using large silica particles. The thickness of titania coating layer was varied from 8 nm to 38 nm depending on the number of coating steps from 1 to 3 times. After titania coating, the core-shell particles showed textured surface due to the titania coating layer, resulting in 3~25 times increase of specific surface areas. The properties of titania coated silica particles were characterized by FE-SEM, Zeta potential meter, BET, and XRD.

• Journal of Welding and Joining
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• v.27 no.2
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• pp.38-43
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• 2009

In this study, we investigated photocatalytic ability of plasma sprayed $TiO_2$ and Ag sputtering $TiO_2$(Ag-$TiO_2$) coatings. A sputtering processes were adopted to coat the surface of $TiO_2$ with Ag(99.99%). Ag was sputtered at 10mA, 450V for $1{\sim}11$ seconds. $TiO_2$ and Ag-$TiO_2$ coatings were heat-treated at 250, 300, 350, $400^{\circ}C$ for $0{\sim}240$seconds. Photoelectrical conductivity was measured by four-point probe, and photodegradation was calculated by UV-V is spectrometer. Microstructure observation of $TiO_2$ and Ag-$TiO_2$ coatings were investigated by SEM. Crystal structure of $TiO_2$ and Ag-$TiO_2$ coatings were investigated by XRD. Qualitative analyses of $TiO_2$ and Ag-$TiO_2$ coatings were conducted by EDX. When $TiO_2$ coatings were heat-treated at $350^{\circ}C$ for 30 sec, photoelectrical conductivity and photodegradation were best. And in XRD analysis result, (101)/(110) relative intensity ratio of $TiO_2$(rutile) was comparably changed with photoelectrical conductivity. When Ag-$TiO_2$ coatings were heat-treated at $350^{\circ}C$ for 30 [sec] after sputtering Ag for 7 sec, Photoelectrical conductivity and photodegradation are best. Surface of coatings in such condition has very small and uniform Ag particles.

• Corrosion Science and Technology
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• v.5 no.2
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• pp.45-51
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• 2006

Properties of the anode for cathodic protection need low overvoltage for oxygen evolution and high corrosion resistance. It is well known that DSA (Dimensionally Stable Anode) has been the best anode ever since. DSA is mainly composed of $RuO_2$, $IrO_2$, $ZrO_2$, $Co_2O_3$, and also $Ta_2O_5$, $TiO_2$, $MnO_2$ are added to DSA for better corrosion resistance. The lifetime of DSA for cathodic protection is also one of the very important factors. $RuO_2$, $IrO_2$, $RhO_2$, $ZrO_2$ are well used for life extension, and many researches are focused on life extension by lowering oxygen evolution potential and minimizing dissolution of oxide coatings. This work aims to evaluate the influence of constituents of MMO and coating cycles and $ZrO_2$ coating on the electrochemical properties and lifetime of DSA electrodes. From the results of lifetime assessment in the anodes coated with single component, $RuO_2$ coating was more effective and showed longer lifetime than $IrO_2$ coating. Also, an increased coating cycle and an electrochemically coated $ZrO_2$ could enhance the lifetime of a DSA.

• Journal of Electrochemical Science and Technology
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• v.10 no.2
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• pp.148-158
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• 2019

The corrosion protection of AA2024 PPy coated samples doping with nanosized metal oxides, including $TiO_2$ and $CeO_2$ nanoparticles and $Nd_2O_3$ nanorods, during exposure to the solutions of 0.1 M $H_2SO_4$ and 3.5% NaCl was evaluated by electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) techniques. The nanorods of $Nd_2O_3$ were synthesized by cathodic pulse electrochemical deposition technique. The barrier properties of the different PPy coatings containing nanosized metal oxides immersed in $H_2SO_4$ solution were ranked as follows: $Nd_2O_3$ > $TiO_2$ > $CeO_2$. Therefore, the $Nd_2O_3$ coating sample provided the highest corrosion protection at any time of immersion up to 72 hours after immersing in $H_2SO_4$ solution. On the other hand, the $CeO_2$ coating sample displayed the best anticorrosive properties among the other coating samples after immersion in NaCl solution up to 28 days. This is due to the inhibition effect of cerium ions on aluminum alloys at near-neutral solutions.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2005.09a
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• pp.201-212
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• 2005

[ $Epoxy/BaTiO_3$ ] composite embedded capacitor films (ECFs) were newly designed fur high dielectric constant and low tolerance (less than ${\pm}15\%$) embedded capacitor fabrication for organic substrates. In terms of material formulation, ECFs are composed of specially formulated epoxy resin and latent curing agent, and in terms of coating process, a comma roll coating method is used for uniform film thickness in large area. Dielectric constant of $BaTiO_3\;&\;SrTiO_3$ composite ECF is measured with MIM capacitor at 100 kHz using LCR meter. Dielectric constant of $BaTiO_3$ ECF is bigger than that of $SrTiO_3$ ECF, and it is due to difference of permittivity of $BaTiO_3\;and\;SrTiO_3$ particles. Dielectric constant of $BaTiO_3\;&\;SrTiO_3$ ECF in high frequency range $(0.5\~10GHz)$ is measured using cavity resonance method. In order to estimate dielectric constant, the reflection coefficient is measured with a network analyzer. Dielectric constant is calculated by observing the frequencies of the resonant cavity modes. About both powders, calculated dielectric constants in this frequency range are about 3/4 of the dielectric constants at 1 MHz. This difference is due to the decrease of the dielectric constant of epoxy matrix. For $BaTiO_3$ ECF, there is the dielectric relaxation at $5\~9GHz$. It is due to changing of polarization mode of $BaTiO_3$ powder. In the case of $SrTiO_3$ ECF, there is no relaxation up to 10GHz. Alternative material for embedded capacitor fabrication is $epoxy/BaTiO_3$ composite embedded capacitor paste (ECP). It uses similar materials formulation like ECF and a screen printing method for film coating. The screen printing method has the advantage of forming capacitor partially in desired part. But the screen printing makes surface irregularity during mask peel-off, Surface flatness is significantly improved by adding some additives and by applying pressure during curing. As a result, dielectric layer with improved thickness uniformity is successfully demonstrated. Using $epoxy/BaTiO_3$ composite ECP, dielectric constant of 63 and specific capacitance of 5.1nF/cm2 were achieved.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.425.2-425.2
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• 2014

$TiO_2$ possesses great photocatalytic properties but absorbs only UV light owing to high band gap energy (Eg = 3.2 eV). By narrowing the band gap through doping a metal ion, the photocatalytic activity can be enhanced in condition of the light of a higher than 365 nm wavelength. Main purpose for this study is to evaluate the activities of metal doped $TiO_2$ for degrading the volatile organic compounds (VOCs); p-xylene is chosen in the VOC removal test. Vanadium is selected in this study because an ionic radius of vanadium is almost the same as titanium ion and vanadium can be easily doped into $TiO_2$. V-doped $TiO_2$ was synthesized by sol-gel methods and compared with pure $TiO_2$. Pure TiO2 powder and V-doped $TiO_2$ powder were coated on glasses by spray coating method. UV-Visible spectrophotometer was used for the measurement of the band gap changes. VOC concentration degradation level was tested with using various UV light sources in an enclosed chamber. Catalytic activities of prepared samples were evaluated based on the experimental results and compared with coated pure $TiO_2$ sample.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.6
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• pp.418-424
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• 2000

Pure $TiO_2$and 10 mol % Pb-doped $TiO_2(Pb_xTi_{1-x}O_2$(x = 0.1)) powder and thin films have been prepared by the sol-gel method. Titanium isopropoxide and ethanol are used for pure $TiO_2$, lead acetate trihydrate and titanium triisopropoxide monoacethylacetonate are used for Pb-doped $TiO_2$, respectively. Films are coated on p-type Si(100) wafer and ITO glass substrates by the sol-gel spin-coating method. The powder and multi-coated films are annealed at different temperature (400~$800^{\circ}C$) for phase formation and crystallization. TGA/DTA, XRD analysis, SEM and UV-visible transmission spectroscopy have been used to study the characteristics of the powder and films. XRD results show that the films are polycrystalline, anatase type and oriented predominantly to the A(101) plane. A slight shift in the d-spacing for the Pb-doped film indicates the incorporation of the Pb into $TiO_2$lattice. A shift of the absorption wavelength in the transmission spectrum towards longer wavelength has been observed about $Pb_xT_{1-x}O_2$(x = 0.1) thin film, which indicates a decrease in the bandgap of $TiO_2$upon Pb-doping.

• Journal of Aerospace System Engineering
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• v.13 no.2
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• pp.43-50
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• 2019

Satellite and aircraft components are greatly affected by the possibility for missions and safety due to temperature effects. In the field of fuel cells, research is actively carried out for UAV. For the efficiency and stability of the fuel cells, the temperature for operations must be confirmed. In this paper, a smart paint was fabricated with $BaTiO_3$ and $SrTiO_3$ ceramics in order to take advantage of the rapid characteristics of the PTC thermistor, which is the resistance changes abruptly above the Curie point. A coating agent was prepared to prevent the paint from peeling off the samples and the coated models were checked for resistance changes. Moreover, the resistance change of the $BaTiO_3$ and $SrTiO_3$ with temperature conditions was measured before and after coating.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.130.1-130.1
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• 2013

We made attempts to improve photocatalytic activity of $TiO_2$ nanoparticles under visible light exposure by combining two additional treatments. N-doping of $TiO_2$ by ammonia gas treatment at $600^{\circ}C$ increased absorbance of visible light. By coating thin film of polydimethylsiloxane (PDMS), and subsequent vacuum-annealing at $800^{\circ}C$, $TiO_2$, became more hydrophilic, thereby enhancing photocatalytic activity of $TiO_2$. Four types of $TiO_2$ samples were prepared, bare-$TiO_2$, hydrophilic-modified $TiO_2$ ($h-PDMS/TiO_2$), N-doped $TiO_2$ ($N/TiO_2$) and hydrophilic-modified and N-doped $TiO_2$ ($h-PDMS/N/TiO_2$). Adsorption capability was evaluated under dark condition and photocatalytic activity of $TiO_2$ was evaluated by photodegradation of MB under blue LED (400 nm< ${\lambda}$) irradiation. N-doping on $TiO_2$ was characterized using XPS and hydrophilic modification of $TiO_2$ surface was analyzed by FT-IR spectrometer. It was found that N-doping and hydrophilic modification both had positive effect on enhancing adsorption capability and photocatalytic activity of $TiO_2$ at the same time. Particularly, N-doping enhanced visible light absorption of $TiO_2$, whereas hydrophilic surface modification increased MB adsorption capacity. By combining these two strategies, photocatalytic acitivity under visible light irradiation became the sum of individual effects of N-doping and hydrophilic modification.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.615-616
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• 2005

Carbon Nanotubes (CNT) on flexible indium tin oxide (ITO) PET films were prepared for dye-sensitized solar cell (DSSC). These CNTs were prepared by spray coating method for various amount of light transparency. Also, Pt counter electrode was prepared by electro deposition method. All $TiO_2$ electrodes were deposited on ITO-PET films by spray coating method. Micro structural images show that CNT counter electrodes prepared by spray-coating have more dense structure with increasing spraying time (0 to 60 seconds). DSSC consisting of $TiO_2$ electrode and CNT counter electrode was fabricated with various amount of light absorption. DSSC have higher light energy conversion efficiency with increasing the thickness of CNT counter electrode. CNT counter electrode is at least compatible to that of CNT counter electrode.