• Journal of Environmental Science International
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• v.21 no.11
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• pp.1321-1331
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• 2012

To date, carbon and nitrogen co-doped photocatalysts (CN-$TiO_2$) for environmental application focused mainly on the aqueous phase to investigate the decomposition of water pollutants. Accordingly, the present study explored the photocatalytic performance of CN-$TiO_2$ photocatalysts for the purification of indoor-level gas-phase aromatic species under different operational conditions. The characteristics of prepared photocatalysts were investigated using X-ray diffraction, scanning emission microscope, diffuse reflectance UV-VIS-NIR analysis, and Fourier transform infrared (FTIR) analysis. In most cases, the decomposition efficiency for the target compounds exhibited a decreasing trend as input concentration (IC) increased. Specifically, the average decomposition efficiencies for benzene, toluene, ethyl benzene, and xylene (BTEX) over a 3-h process decreased from 29% to close to zero, 80 to 5%, 95 to 19%, and 99 to 32%, respectively, as the IC increased from 0.1 to 2.0 ppm. The decomposition efficiencies obtained from the CN-$TiO_2$ photocatalytic system were higher than those of the $TiO_2$ system. As relative humidity (RH) increased from 20 to 95%, the decomposition efficiencies for BTEX decreased from 39 to 5%, 97 to 59%, 100 to 87%, and 100 to 92%, respectively. In addition, as the stream flow rates (SFRs) decreased from 3.0 to 1.0 L $min^{-1}$, the average efficiencies for BTEX increased from 0 to 58%, 63 to 100%, 69 to 100%, and 68 to 100%, respectively. Taken together, these findings suggest that three (IC, RH, and SFR) should be considered for better BTEX decomposition efficiencies when applying CN-$TiO_2$ photocatalytic technology to purification of indoor air BTEX.

• The Korean Journal of Ceramics
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• v.6 no.1
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• pp.47-52
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• 2000

Lanthanides such as La, Gd and Ce have recognized as elements of high level radioactive wastes immobilized by forming solid solution with $CaTiO_3$. For easy forming solid solution between $CaTiO_3$and lanthanides, the combustion synthesis process was applied and the powder characteristics and sinterability were investigated. The proper selection of the type and the composition of fuels are important to get the crystalline solid solution of $CaTiO_3$and lanthanides. When glycine or the mixtures of urea and citric acid with stoichiometric composition was used as a fuel, the solid solution of $CaTiO_3$with $La_2O_3$or $Gd_2O_3$or $CeO_2$was produced very well by the combustion process. The combustion synthesized powder seemed to have a good sinterability with the linear shrinkage of more than 25% up to $1500^{\circ}C$, while that of the solid state reacted powder was less than 10% at the same condition.

• Proceedings of the Korean Fiber Society Conference
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• 2007.11a
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• pp.261-262
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• 2007

• Journal of the Korean Ceramic Society
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• v.32 no.5
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• pp.567-574
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• 1995

The effect of MnO2 addition to 0.1mol% Sb2O3-doped BaTiO3 ceramics on microstructure and PTCR characteristics was studied. The PTCR characteristics was observed when 0.01 and 0.02 wt% MnO2 were added and sintered at 132$0^{\circ}C$ for 1 hour. The characteristics can be explained by the changes in the number and size of the abnormal grain growth due to the liquid phase during sintering. when the amount of MnO2 addition was 0.03 wt%, the sample showed NTCR characteristics with room-temperature resistivity over 109 Ωm regardless of the sintering temperature. This behavior can be described by the microstructure change due to the abnormal grain growth and charge compensation effect by MnO2 added. The room-temperature resistivity was increased as the amount of MnO2 was increased. And the specific resistivity ratio (pmax/pmin) showed maximum at 0.02wt% MnO2.

• Journal of Surface Science and Engineering
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• v.51 no.6
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• pp.365-371
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• 2018

1D core-shell nanostructures have attracted great attention due to their enhanced physical and chemical properties. Specifically, oriented single-crystalline $TiO_2$ nanorods or nanowires on a transparent conductive substrate would be more desirable as the building core backbone. However, a facile approach to produce such structure-based hybrids is highly demanded. In this study, a three-step hydrothermal method was developed to grow NiMn-layered double hydroxide-decorated $TiO_2$/carbon core-shell nanorod arrays on transparent conductive fluorine-doped tin oxide (FTO) substrates. XRD, SEM, TEM, XPS and Raman were used to analyze the obtained samples. The in-situ fabricated hybrid nanostructured materials are expected to be applicable for photoelectrode working in water splitting.

• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1128-1134
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• 2010

Nanocarbon supported Fe/$TiO_2$ composite catalysts were prepared using CNTs (carbon nanotubes) and $C_{60}$ (fullerene) as nanocarbon sources by a modified sol-gel method. The Fe/$TiO_2$-nanocarbon composites were characterized by the BET surface area, scanning electron microscope (SEM), Transmission Electron Microscope (TEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) and UV-vis spectra. In comparison with non-nanocarbon doped Fe/$TiO_2$ composites, the nanocarbon supported Fe/$TiO_2$ composites had higher absorption ability with a larger specific surface area, and showed higher photocatalytic activity during the degradation of methylene blue (MB) under visible light. The reasons for the obvious increase of photocatalytic activity indicated that the photoactivity not only benefits from nanocarbon introduced, but also relates to the cooperative effect of the Fe as a dopant.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.461-462
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• 2005

In order to improve the efficiency of dye-sensitized solar cell (DSC), $TiO_2$ electrode screen-printed on transparent conducting oxide (TCO) substrate was sintered in variation with different temperature(350 to $550^{\circ}C$). $TiO_2$ electrode on fluorine doped tin oxide (FTO) glass was assembled with Pt counter electrode on FTO glass. I-V properties of DSC were measured under solar simulator. Also, effect of sintering temperature on surface morphology of $TiO_2$ films was investigated to understand correlation between its surface morphology and sintering temperature. Such surface morphology was observed by atomic force microscopy (AFM). From the measurement results, at sintering temperature of $500^{\circ}C$, both efficiency and fill factor of DSC were mutually complementary, enhancing highest fill factor and efficiency. Consequently, it was considered that optimum sintering temperature of $\alpha$-terpinol included $TiO_2$ paste is at $500^{\circ}C$.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.110.1-110.1
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• 2012

Recently, advances in ZnO based oxide semiconductor materials have accelerated the development of thin-film transistors (TFTs), which are the building blocks for active matrix flat-panel displays including liquid crystal displays (LCD) and organic light-emitting diodes (OLED). However, the electrical performances of oxide semiconductors are significantly affected by interactions with the ambient atmosphere. Jeong et al. reported that the channel of the IGZO-TFT is very sensitive to water vapor adsorption. Thus, water vapor passivation layers are necessary for long-term current stability in the operation of the oxide-based TFTs. In the present work, $Al_2O_3$ and $TiO_2$ thin films were deposited on poly ether sulfon (PES) and $SnO_x$-based TFTs by electron cyclotron resonance atomic layer deposition (ECR-ALD). And enhancing the WVTR (water vapor transmission rate) characteristics, barrier layer structure was modified to $Al_2O_3/TiO_2$ layered structure. For example, $Al_2O_3$, $TiO_2$ single layer, $Al_2O_3/TiO_2$ double layer and $Al_2O_3/TiO_2/Al_2O_3/TiO_2$ multilayer were studied for enhancement of water vapor barrier properties. After thin film water vapor barrier deposited on PES substrate and $SnO_x$-based TFT, thin film permeation characteristics were three orders of magnitude smaller than that without water vapor barrier layer of PES substrate, stability of $SnO_x$-based TFT devices were significantly improved. Therefore, the results indicate that $Al_2O_3/TiO_2$ water vapor barrier layers are highly proper for use as a passivation layer in $SnO_x$-based TFT devices.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.3
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• pp.223-227
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• 2007

The effect of Eu contents on the ferroelectric properties of $Bi_{4-x}Eu_xTi_3 O_{12}$ (BET) thin films has been investigated. Bismuth Europium titanate thin films with a Eu contents were prepared on the $Pt/Ti/SiO_2/Si$ substrate by metal-organic decomposition technique. The structure and the morphology of the films were analyzed using X-ray diffraction (XRD) and field emission scanning microscopy (FE-SEM), respectively. From the XRD analysis, it was found that BET thin films have polycrystalline structure, and the layered-perovskite phase is obtained when the Eu contents exceeds 0.2 (x > 0.2). Also, the ferroelectric characteristics of the BET thin films were found to be dependent on the Eu content. Particularly, the BET films doped with x = 0.75 show better ferroelectric properties (remanent polarization 2Pr = 60.99 C/$cm^2$ and only a little polarization fatigue up to $3.5{\times}10^9$ bipolar switching cycling) than those doped with other Eu contents.

• Korean Journal of Materials Research
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• v.20 no.5
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• pp.246-251
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• 2010

The composite photocatalysts of a Fe-modified carbon nanotube (CNT)-$TiO_2$ were synthesized by a two-step sol-gel method at high temperature. Its chemical composition and surface properties were investigated by BET surface area, scanning electron microscope (SEM), Transmission Electron Microscope (TEM), X-ray diffraction (XRD) and ultraviolet-visible (UV-Vis) spectroscopy. The results showed that the BET surface area was improved by modification of Fe, which was related to the adsorption capacity for each composite. Interesting thin layer aggregates of nanosized $TiO_2$ were observed from TEM images, probably stabilized by the presence of CNT, and the surface and structural characterization of the samples was carried out. The XRD results showed that the Fe/CNT-$TiO_2$ composites contained a mix of anatase and rutile forms of $TiO_2$ particles when the precursor is $TiOSO_4{\cdot}xH_2O$ (TOS). An excellent photocatalytic activity of Fe/CNT-$TiO_2$ was obtained for the degradation of methylene blue (MB) under visible light irradiation. It was considered that Fe cation could be doped into the matrix of $TiO_2$, which could hinder the recombination rate of the excited electrons/holes. The photocatalytic activity of the composites was also found to depend on the presence of CNT. The synergistic effects among the Fe, CNT and $TiO_2$ components were responsible for improving the visible light photocatalytic activity.