• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.5
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• pp.791-799
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• 1997

The wear characteristics and wear mechanisms of plasma sprayed Al/sub 2/ O/sub 3/-40%TiO/sub 2/ and Cr/sub 2/O/sub 3/ deposited on casting aluminum alloy(AC4C) were investigated. Specimens were processed for various coating thicknesses. Ball on disk type wear tester was used for wear test. The scratch test on plasma sprayed coating surface showed that critical load to break the coating layer was greater than 40 N. The critical load increase with the increase of coating thickness of specimens. The friction coefficient of Cr/sub 2/O/sub 3/ coating layer was less than that of Al/sub 2/O/sub 3/-40%TiO/sub 2/ coating layer. The wear resistance of Cr/sub 2/O/sub 3/ coating layer was greater than that of Al/sub 2/O/sub 3/-40%TiO/sub 2/ coating layer. Microscopic observation of worn surfaces was made by SEM. SEM observation showed that the main mechanism of wear for Al/sub 2/O/sub 3/-40%TiO/sub 2/ coating layer was abrasive wear under 50 N. For the case of Al/sub 2/O/sub 3/-40%TiO/sub 2/ coating layer, as the surface cracks perpendicular to sliding direction propagated, the wear debris was generated in wear track. However, the main mechanism of wear for Cr/sub 2/O/sub 3/ coating layer was brittle fracture under 150 N.

• Journal of Environmental Science International
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• v.29 no.12
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• pp.1213-1222
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• 2020

In the current study, a Cu2O/TiO2 photoinduced nanocomposite materials prepared by ultrasonification method was evaluated the photocatalytic oxidation efficiency of volatile organic compounds (BTEX) under visible-light irradiation. The results of XRD confirmed the successful preparation of photoinduced nanocomposite materials. However, diffraction peaks belonging to TiO2 were not confirmed for the Cu2O/TiO2. The possible reason for the absence of Cu2O peak is their low content and small particle size. The result of uv-vis spectra exhibited that the fabricated Cu2O/TiO2 can be activated under visible light irradiation. The FE-SEM/EDS and TEM showed the formation of synthesized nanocomposites and componential analysis in the undoped TiO2 and Cu2O/TiO2. The photocatalytic oxidation efficiencies of benzene, toluene, ethylbenzene, and o-xylene with Cu2O/TiO2 were higher than undoped TiO2. According to light sources, the average oxidation efficiencies for BTEX by Cu2OT-0.5 were exhibited in the orer of 8 W day light > violet LEDs > white LEDs. However, the photocatalytic oxidation efficiencies normalized to supplied electric power were calculated to be in the following order of violet LEDs > white LEDs > 8 W day light, indicating that the LEDs could be a much more energy efficient light source for the photo-oxidation of gaseous BTEX using Cu2O/TiO2.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.5
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• pp.397-403
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• 2003

Microwave dielectric properties of (1-x)ZnW $O_4$-xTi $O_2$ ceramic systems were investigated with calcination temperatures and Ti $O_2$ contents. The ZnW $O_4$ ceramic could be suitably sintered at 1075$^{\circ}C$ and showed the dielectric constant of 13.6, quality factor(Q$\times$ $f_{O}$value) of 22,000 and temperature coefficient of resonant frequency($\tau$$_{f}$) of -65$\pm$2ppm/$^{\circ}C$. Increasing the amount of Ti $O_2$ in the range of 0.25 to 0.45 mol, the dielectric constant and $\tau$$_{f}$ increased due to the role of Ti $O_2$ but the quality factor decreased due to the increase of phase boundaries. The 0.7ZnW $O_4$-0.3Ti $O_2$ ceramic showed the dielectric constant of 19.8, qualify factor(Q$\times$ $f_{0}$) of 20,000 and $\tau$$_{f}$ of -3$\pm$1ppm/$^{\circ}C$.>.EX>.>.>.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.323-324
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• 2023

The properties of cement mortar mixed with manganese-doped titanium dioxide nanowires (TiO₂(Mn)-NWs) were investigated in this study. The TiO₂(Mn)-NWs were synthesized using solvo-thermal synthesis and electro-spinning techniques. The TiO₂(Mn)-NWs at weights of 1%, ₂%, and 3% of the cement were respectively mixed into the cement mortar. The results showed that as the amount of TiO₂(Mn)-NWs increased, the flow value of the cement mortar was decreased and the setting time of cement mortar was accelerated. Moreover, as the amount of TiO₂(Mn)-NWs increased, the compressive strength of cement mortar was increased and the efficiency of acetaldehyde removal was improved.

• Journal of Industrial Technology
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• v.20 no.A
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• pp.51-56
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• 2000

The Photocatalytic decolorization and degradation of commercial dyes were studied using a batch reactor. Degussa P25 titanium dioxide and $H_2O_2$ were used as the photocatalyst and proved to be effective for dyes degradation when they were irradiated with UV light. The light source was a 20W low pressure mercury lamp. Three different kinds of dyes, such as direct dye(congo red), acid dye (acid black) and disperse dye(disperse blue) were tested. Extending the UV only treatment up to 120min, direct dye was decolorized to 60% and degraded to 30% as COD. On the other side, acid and disperse dyes were eliminated less than 10% as color and COD. But, color and COD were eliminated about 90% for all of the three dyes by $UV/H_2O_2$ system. And then the most effective decolorization was done for direct dye with 96% removal efficiency by $UV/TiO_2$ system at 120min with 500mg/L of $TiO_2$.

• Journal of Environmental Science International
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• v.17 no.11
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• pp.1273-1279
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• 2008

This study examined the catalytic destruction of 1,2-dichlorobenzene on ${V_2}{O_5}/TiO_2$ nanoparticles. The ${V_2}{O_5}/TiO_2$ nanoparticles were synthesized by the thermal decomposition of vanadium oxytripropoxide and titanium. The effects of the synthesis conditions, such as the synthesis temperature and precursor heating temperature, were investigated. The specific surface areas of ${V_2}{O_5}/TiO_2$ nanoparticles increased with increasing synthesis temperature and decreasing precursor heating temperature. In addition, the removal efficiency of 1,2-dichlorobenzene was promoted by a decrease in heating temperature. However, the removal efficiency of 1,2-dichlorobenzene was decreased by an anatase to rutile phase transformation at temperatures $1,300^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.5
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• pp.513-519
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• 2023

It was reported that a tetragonal phase can be stabilized with maintaining good piezoelectric properties when Na_0.5K_0.5NbO₃ (KNN) is modified with 0.06 mol SrTiO₃. However, such a high amount of SrTiO₃ leads not only to poor sinterability but low Curie temperature (T_C). To maintain high TC with good piezoelectric properties in KNN-based lead-free piezoelectric ceramics, this study investigates the effect of Li-doping on the dielectric and piezoelectric properties of 0.96Na_0.5K_0.5NbO₃-0.04SrTiO₃ (KNN-4ST) ceramics. As a result, the orthorhombic-tetragonal phase transition was observed at 2 mol% Li₂CO₃ modified KNN-4ST ceramics, whose T_C, d₃₃ and k_p values are 328℃, 165pC/N and 0.33, respectively.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.4
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• pp.154-161
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• 2017

$Zn_2TiO_4$, which is a progenitor of zinc crystallization, plays a significant role in controlling the crystallization of willemite ($Zn_2SiO_4$) in forming glaze at low temperatures. Thus, $Zn_2TiO_4$ was used to formulate stable willemite and to gain structural control. When synthesized 15 wt% of $Zn_2TiO_4$ is added to engobe and then applied, it can manipulate its crystallization and location. Additionally, when colorant is added to $Zn_2TiO_4$ and then applied to engobe, the mixture's colorant effect can be shown at crystallization. Certain characteristics of synthesized $Zn_2TiO_4$ enable various engobes to be applied to clay bodies. With a single glazing, the crystallization, location, and color of the crystals can be discretionarily regulated.

• Clean Technology
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• v.25 no.4
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• pp.296-301
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• 2019

This study was conducted to investigate the characteristics of CO oxidation by NO poisoning in Pt/TiO₂ catalyst prepared by wet impregnation method and calcined at 400 ℃. In order to confirm the NO poisoning effect of the Pt/TiO₂ catalyst, the change of reaction activity was observed when NO was injected during the CO+O₂ reaction where it was ascertained that the CO conversion rate rapidly decreased below 200 ℃. Also, CO conversion was not observed below 125 ℃. Recovery of initial CO conversion was not verified even if NO injection was blocked at 125 ℃. Accordingly, various analyses were performed according to NO injection. First, as a result of the TPD analysis, it was confirmed that NO pre-adsorption in catalyst inhibited CO adsorption and conversion desorption from adsorbed CO to CO₂. When NO was pre-adsorbed, it was confirmed through H₂-TPR analysis that the oxygen mobility of the catalyst was reduced. In addition, it was validated through FT-IR analysis that the redox cycle (Pt²⁺→Pt⁰→Pt²⁺) of the catalyst was inhibited. Therefore, the presence of NO in the Pt/TiO₂ catalyst was considered to be a poisoning factor in the CO oxidation reaction, and it was determined that the oxygen mobility of the catalyst is required to prevent NO poisoning.

• Bulletin of the Korean Chemical Society
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• v.25 no.4
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• pp.475-479
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• 2004

$TiO_2$ thin films were grown on Si (100) substrates by atomic layer deposition using $[Ti(OPr^i )_2(dmae)_2]$ and water as precursors. The thickness, chemical composition, crystalline structure, and morphology of the deposited films were investigated by transmission electron microscopy, UV spectrometry, X-ray photoelectron pectroscopy, X-ray diffraction, and atomic force microscopy. The results show that $TiO_2$ ALD using $[Ti(OPr^i )_2(dmae)_2]$ as a precursor is self-controlled at temperatures of 100-300$^{\circ}C$. At the growth temperatures below 300$^{\circ}C$, the surface morphology of the $TiO_2$ films is smooth and uniform. The $TiO_2$ film was grown with a preferred orientation toward the [101] direction at 400$^{\circ}C$.