• 한국분말재료학회지
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• 제11권2호
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• pp.143-148
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• 2004

In the present study, $TiO_2$ imbedded composite powders have been successfully prepared from the (Cu. Zn)/$TiO_2$ composite salt solution. The composite (Cu, Zn)/$TiO_2$ powders were formed by drying the solution at 200~$600^{\circ}C$ in the hydrogen atmosphere. Photocatalytic characteristics was evaluated by detecting the decomposition ratio of aniline blue with UV-visible spectrophotometer(Shimazu Co., UV-1601). Phase analysis of (Cu, Zn)/$TiO_2$ composite powders was carried out by XRD and DSC, and powder size was measured with TEM. The mean particle size of composite powders was about 100mm. As the reduction temperature increases, a few zinc sulfide and oxide phases was formed and copper oxide phase was reduced. The decomposition ratio of aniline blue was about 80％ under the UV irradiation by the TiO$_2$ phase in the composite (Cu, Zn)/$TiO_2$ powders and similar decomposition ratio of 80％ was obtained at the UV lightless condition by virtue of Cu and Zn compounds.

• Journal of Welding and Joining
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• 제21권4호
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• pp.46-55
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• 2003

TiO$_2$-WO$_3$(8.2wt%) coatings were prepared by the APS (Atmospheric Plasma Spraying) process to clarify the relationship between the process parameters(H$_2$ gas flow rate of plasma 2nd gas and spraying distance) of the APS coating and photo-decomposition efficiency kinetics of the MB(methylene blue) aqueous solution decomposition and to understand the effect of addition of WO$_3$ on photocatalytic properties of TiO$_2$ sprayed coating. Further, the temperature and velocity of flying particles were measured by DPV-2000 to investigate the relationship between microstructure of coatings and process parameters. Properties of coatins were investigated by XRD, SEM, XPS, RAMAN, UV/VIS spectrometer. In case of the TiO$_2$-WO$_3$(8.2wt%) coating, it had a lower anatase fraction than that of pure-TiO$_2$ coatings because of flying in the higher temperature plasma plume by the heavy weight of TiO$_2$, WO$_3$. And, when WO$_3$ added powders were spayed, the doping effects of W ions substituted into the Ti ion sites was not occured during melting and solidification cycles of spraying. It was found that the addition of WO$_3$ was ineffective effective on increasing photo-decomposition efficiency of TiO$_2$ sprayed coating.

• 대한금속재료학회지
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• 제56권12호
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• pp.900-909
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• 2018

A $ZnO/TiO_2$ photocatalyst decorated with PbS quantum dots (QDs) was synthesized to achieve high photocatalytic efficiency for the decomposition of dye in aqueous media. A $TiO_2$ porous layer, as a precursor photocatalyst, was fabricated using micro-arc oxidation, and exhibited irregular porous cells with anatase and rutile crystalline structures. Then, a ZnO-deposited $TiO_2$ catalyst was fabricated using a zinc acetate solution, and PbS QDs were uniformly deposited on the surface of the $ZnO/TiO_2$ photocatalyst using the successive ionic layer adsorption and reaction (SILAR) technique. For the PbS $QDs/ZnO/TiO_2$ photocatalyst, ZnO and PbS nanoparticles are uniformly precipitated on the $TiO_2$ surface. However, the diameters of the PbS particles were very fine, and their shape and distribution were relatively more homogeneous compared to the ZnO particles on the $TiO_2$ surface. The PbS QDs on the $TiO_2$ surface can induce changes in band gap energy due to the quantum confinement effect. The effective band gap of the PbS QDs was calculated to be 1.43 eV. To evaluate their photocatalytic properties, Aniline blue decomposition tests were performed. The presence of ZnO and PbS nanoparticles on the $TiO_2$ catalysts enhanced photoactivity by improving the absorption of visible light. The PbS $QDs/ZnO/TiO_2$ heterojunction photocatalyst showed a higher Aniline blue decomposition rate and photocatalytic activity, due to the quantum size effect of the PbS nanoparticles, and the more efficient transport of charge carriers.

• 한국분말재료학회지
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• 제24권6호
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• pp.483-488
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• 2017

Transition-metal oxide semiconductors have various band gaps. Therefore, many studies have been conducted in various application fields. Among these, methods for the adsorption of organic dyes and utilization of photocatalytic properties have been developed using various metal oxides. In this study, the adsorption and photocatalytic effects of $WO_3$ nanomaterials prepared by hydrothermal synthesis are investigated, with citric acid added in the hydrothermal process as a structure-directing agent. The nanostructures of $WO_3$ are studied using transmission electron microscopy and scanning electron microscopy images. The crystal structure is investigated using X-ray diffraction patterns, and the changes in the dye concentrations adsorbed on $WO_3$ nanorods are measured with a UV-visible absorption spectrophotometer based on Beer-Lambert's law. The methylene blue (MB) dye solution is subjected to acid or base conditions to monitor the change in the maximum adsorption amount in relation to the pH. The maximum adsorption capacity is observed at pH 3. In addition to the dye adsorption, UV irradiation is carried out to investigate the decomposition of the MB dye as a result of photocatalytic effects. Significant photocatalytic properties are observed and compared with the adsorption effects for dye removal.

• Bulletin of the Korean Chemical Society
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• 제30권3호
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• pp.675-678
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• 2009

$Fe_2O_3,\;Ag_2O,\;CaWO_4$ and $Gd_2O_2S$:Tb loaded on titanium dioxide photocatalysts (P25, Degussa) were prepared by a calcination. Their composite films containing water-born polyurethane used as a material for immobilization were obtained by spray coating technique. The photocatalytic activity of the titanium dioxide films was characterized by decrease of UV-vis absorption spectra for methylene blue and gas chromatography for photocatalytic decomposition of formaldehyde diluted in water. It was shown that the $Gd_2O_2S$:Tb modified titanium dioxide films had good photocatalytic properties and followed the first-order kinetic model with regard to photocatalytic decoloration of methylene blue. Especially in formaldehyde photodegradation experiment, decrease rate of concentration of the titanium dioxide films with $Gd_2O_2S$:Tb modifying was about 35% larger than that of the unloaded titanium dioxide film.

• Bulletin of the Korean Chemical Society
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• 제31권2호
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• pp.344-350
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• 2010

The improved photocatalytic performance of a carbon/$TiO_2$ composite was studied for the Bisphenol A (BPA) decomposition. Titanium tetraisopropoxide (TTIP) and a rice husk from Korea were heterogeneously mixed as the titanium and carbon sources, respectively, for 3 h at room temperature, and then thermally treated at $600^{\circ}C$ for 1 h in $H_2$ gas. The transmission electron microscopy (TEM) images revealed that the bulk carbon partially covered the $TiO_2$ particles, and the amount that was covered increased with the addition of the rice husk. The acquired carbon/$TiO_2$ composite exhibited an anatase structure and a novel peak at $2{\theta}=32^{\circ}$, which was assigned to bulk carbon. The specific surface area was significantly enhanced to 123~164 $m^2/g$ in the carbon/$TiO_2$ composite, compared to $32.43m^2/g$ for the pure $TiO_2$. The X-ray photoelectron spectroscopy (XPS) results showed that the Ti-O bond was weaker in the carbon/$TiO_2$ composite than in the pure $TiO_2$, resulting in an easier electron transition from the Ti valence band to the conduction band. The carbon/$TiO_2$ composite absorbed over the whole UV-visible range, whereas the absorption band in the pure$TiO_2$ was only observed in the UV range. These results agreed well with an electrostatic force microscopy (EFM) study that showed that the electrons were rapidly transferred to the surface of the carbon/$TiO_2$ composite compared to the pure $TiO_2$. The photocatalytic performance of the BPA removal was optimized at a Ti:C ratio of 9.5:0.5, and this photocatalytic composite completely decomposed 10.0 ppm BPA after 210 min, whereas the pure $TiO_2$ achieved no more than 50% decomposition under any conditions.

• 공업화학
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• 제26권6호
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• pp.714-718
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• 2015

$PbMoO_4$ 및 $PbMo_{1-x}Cr_xO_4$ 산화물을 수열합성법으로 합성하여 XRD, DRS, Raman, SEM 및 PL 등에 의해 특성분석을 하였고, 자외선 및 가시광 조사 하에서 rhodamine B의 광분해 반응에서의 활성을 조사하였다. XRD 및 Raman의 분석 결과로부터 대부분의 촉매들은 크롬이온의 첨가와 무관하게 잘 결정화된 $PbMoO_4$ 구조를 가지고 있었으며 51에서 59 nm의 크기를 나타내었다. $PbMo_{1-x}Cr_xO_4$ 산화물의 DRS 곡선은 가시광 영역으로 강한 흡수선을 나타내었다. $PbMoO_4$ 산화물은 가시광 조사 하에서 낮은 광촉매 활성을 나타내었으나 크롬이온의 첨가량이 증가할수록 활성이 증가하였다. 모든 촉매들은 540-580 nm 부근에서 강하고 넓은 PL 흡수밴드가 나타났으며, 이 피크의 세기가 커질수록 광분해 활성이 증가하는 것으로 나타났다.

• 한국환경과학회지
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• 제12권3호
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• pp.319-324
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• 2003

The characteristics of photocatalytic decomposition of dye waste water by titanium dioxide was studied in a batch reactor under constant strength of ultra-violet ray. The decomposition rate of methyl orange by TiO$_2$ was pseudo-first order, anatase type TiO$_2$ was more effective than rutile type below the dosage of 5g. The decomposition rate was increased with decreasing initial pH, increasing reaction temperature and oxidant concentration. The decomposition rate of water soluble dyes was decreased in order of rhodamine B>eosin Y>methyl orange.

• 한국대기환경학회지
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• 제19권1호
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• pp.85-92
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• 2003

A new type of catalytic filers has been developed in this work. A porous photocatalytic filter was prepared by coating the titania (anatase phase) powder onto the woven metal mesh. The coating sol was prepared with unique cera-mic binder, and would assist drying condition and enhance the mechanical strength of the final ceramic filers. As a result of the test for acetone decomposition, it was found to be quite effective for the photocatalytic reaction as good at conventional glass reactors which were coated inside. The present filter type reactor is expected as one of plausible devices for the simultaneous treatment of gas - particulate materials.

• Korean Chemical Engineering Research
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• 제46권6호
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• pp.1063-1068
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• 2008

화학기상증착법으로 제조된 $TiO_2$ 광촉매 볼을 이용하여 마이크로웨이브와 자외선을 동시에 조사시켜 메틸렌블루 수용액의 광촉매 분해실험을 하였다. 광촉매반응에 마이크로웨이브와 자외선을 같이 사용하기 위하여 마이크로웨이브에 의해 방전되는 무전극자외선램프를 개발하였다. 실험결과 마이크로웨이브의 강도, 반응수용액의 순환유속 그리고 산화보조제의 첨가량이 증가할수록 광촉매분해속도가 증가하였다. 특히 과산화수소를 첨가한 광촉매반응에 마이크로웨이브를 부가한 실험의 반응속도상수는 $0.0197min^{-1}$이고 광촉매반응에 과산화수소만을 첨가한 경우의 속도상수는 $0.0061min^{-1}$로 약 3배정도 높은 값을 나타내었다. 본 연구의 결과로부터 광촉매반응에 마이크로웨이브가 미치는 영향을 정량적으로 평가하기는 어렵지만, 과산화수소가 첨가되는 광촉매반응에 마이크로웨이브의 조사가 매우 중요한 인자인 것을 알 수 있었다.