• Membrane Journal
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• v.21 no.3
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• pp.229-235
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• 2011

In this study, mesoporous titania/alumina membranes were prepared by sol-gel method. Pore structure and phase composition of titania/alumina membranes could be changed by calcination temperature. The addition of alumina into titania membranes retarded anatase-to-rutile phase transformation, resulting in stabilization of pore structures. The 5 time dip-coated membrane calcined at $450^{\circ}C$ is about $10.3{\mu}m$ in thickness with an average pore size of 5 nm. Hydrogen and nitrogen permeances through the membrane were $17.1{\times}10^{-7}mol/m^2{\cdot}s{\cdot}Pa$ and $4.7{\times}10^{-7}mol/m^2{\cdot}s{\cdot}Pa$, respectively. These data were explained by the Knudsen diffusion mechanism.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.215-215
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• 2012

급속한 산업의 발달은 심각한 환경오염 및 에너지 문제를 가져왔다. 이를 해결하기 위한 방안으로 수소에너지에 대한 관심이 증가하고 있으며, 수소에너지를 생산하는 방법 중 하나로 태양에너지를 원천으로 하는 광촉매(photocatalyst)에 대한 연구가 점차적으로 증가하고 있는 추세이다. 현재 광촉매로 가장 많이 사용되는 $TiO_2$의 경우, 뛰어난 광활성과 저렴한 가격, 광 안정성, 화학적 안정성을 가짐에도 불구하고, 3.2 eV라는 넓은 band gap을 가지기 때문에 385 nm 이상의 긴 파장을 갖는 가시광선은 흡수할 수 없다. 또한, 광촉매 반응과정 중 recombination으로 인한 효율의 손실이 크기 때문에 이러한 문제들을 해결하기 위해 많은 연구가 진행되어 왔다. 본 연구에서는 ICP-assisted DC magnetron sputtering 방법을 이용하여 높은 결정성을 갖는 $TiO_2$ 박막을 제조하였다. 제작된 $TiO_2$ 박막은 높은 광촉매 특성을 나타냈으며, 또한 $TiO_2$의 anatase phase와 rutile phase의 bilayer structure를 통하여 recombination을 감소시킴으로써 높은 효율을 갖는 광촉매를 제작하였다. 박막의 chemical state와 crystallinity를 확인하기 위하여 X-ray photoelectron spectroscopy와 X-ray diffractometer를 이용하여 분석을 수행하였으며, 물 분해 장치(water splitting device)를 제작하여 수소와 산소 생성시 흐르는 전류를 측정하여 광촉매 특성을 평가하였다.

• Journal of the Korean Ceramic Society
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• v.36 no.7
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• pp.691-697
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• 1999

TiO2 powder was adsorbed on the surface of mica using the heterocoagulation method in water TiO2 powder was prepared from hydrolysis of titanium-iso propoxide in a mixed solvent of anhydrous ethanol and water. When the molar ratio of water to titanium iso-propoxide was 0.25 monodispersed spherical TiO2 particles were obtained. The prepared TiO2 powder showed anatase phase after heat treatment at 50$0^{\circ}C$ for 2 h and then transformed to rutile phase after heat treatment at 100$0^{\circ}C$ for 2h. The iso-electric points of TiO2 and Mica were pH 3.9 and pH 3.25 respectively which were measured by the Z-potential analysis in water base. The maximum Z-potential difference between two powders was observed in the range of pH 3.6~3.7 TiO2 powder was adsorbed on the surface of mica by heterocoagulation method in pH 3.6~3,7 The properties of prepared TiO2 powder was haracterized by TG-DTA, XRD and SEM The morphology and thermal properties of TiO2-adsorbed mica were examined.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.489-494
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• 2013

Nano-sized titanium oxide powders were synthesized by a polymer matrix technique using pulp and Titanium tetraisopropoxide (TTIP) as starting materials. The synthesized powders were characterized by XRD and FE-SEM. The particle size of the powders was controlled by preparation conditions, such as heat treatment temperature and time. After investigating various drying and heat treatment conditions, 50-100 nm sized homogeneous titanium oxide particles were obtained by treating at $600^{\circ}C$ for 1 h. The crystallization and rapid growth of particles was accelerated by increasing heat treatment temperature and time. Anatase phase generated below $600^{\circ}C$ transformed to the rutile phase with increasing heat treatment temperature. Moreover, above $800^{\circ}C$, heat treatment time had a very large influence on particle growth, and changing the heating condition also had a large influence on crystal growth.

• Bulletin of the Korean Chemical Society
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• v.26 no.8
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• pp.1214-1218
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• 2005

Ti-HMS samples in which titanium species exist in various forms of isolated tetrahedral state, finely dispersed $TiO_2$ cluster, and some in extra-framework anatase phase were prepared via a direct synthesis route using dodecylamine (DDS) as a structure directing agent by systematically varying the titanium loadings between 2 and 50 mol% Ti/(Ti+Si) in substrate composition. Physicochemical properties of the materials were evaluated using XRD, SEM/TEM, N2 adsorption, UV-vis and XANES spectroscopies. Catalytic properties of Ti-HMS in cyclohexene and 2,6-di-tert-butyl phenol (2,6-DTBP) oxidation using aqueous $H_2O_2$, and vapor phase photocatalytic degradation of acetaldehyde were evaluated. High $H_2O_2$ selectivity was obtained in cyclohexene oxidation, and cyclohexene conversion was found primarily dependent on the amount of tetrahedrally coordinated Ti sites. For bulky 2,6-DTBP oxidation and photocatalytic oxidation of acetaldehyde, on the other hand, conversions were found dependent on the total amount of Ti sites and maintaining an uniform mesoporous structure in the catalysts was not critical for efficient catalysis.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.4
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• pp.173-177
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• 2010

Thermal stabilizing effect of $Yb^{3+},\;Er^{3+}$ codoping into $TiO_2$ powder prepared by sol-gel method and its upconversion characteristics were analyzed. The effect of $TiO_2:Yb^{3+},\;Er^{3+}$ ions on crystallinity and phase transition was studied by X-ray diffraction (XRD). The change of band-gap energy induced from Yb and Er codoping was analyzed by UV-Vis. The band-gap energy of $TiO_2$ have been slightly narrowed by $Yb^{3+},\;Er^{3+}$ codoping, which indicated that the $Yb^{3+},\;Er^{3+}$ ions can enhance the photo-catalytic property of $TiO_2$. green and red up-conversions of $Yb^{3+}$ and $Er^{3+}$ co-doped $Y_2O_3:Yb^{3+},\;Er^{3+}$ phosphor were analyzed by PL equipped with 980 nm laser.

• Journal of the Korean Ceramic Society
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• v.46 no.3
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• pp.234-241
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• 2009

In this study, CNT/$TiO_2$ composites derived from various titanium alkoxides and multiwalled carbon nanotubes (MWCNTs) were synthesized and characterized. Surface areas and pore volumes of the CNT/$TiO_2$ samples showed catastrophic decrease due to deposition of titanium compounds. Scanning electron microscopy (SEM) results indicated that the MWCNTs were homogenously decorated and well-dispersed onto/into the composites without apparent agglomeration of $TiO_2$ particles. In the X-ray diffraction (XRD) patterns, peaks of anatase and rutile phase were observed. The energy dispersive X-ray spectroscopy (EDX) spectra revealed the presence of major elements such as C and O with strong Ti peaks. According to the photocatalytic results, MB removal by a treatment with CNT/$TiO_2$ composites seems to have an excellent removal effect as order of CTIP, CTNB and CTPP composites due to a photolysis of the supported $TiO_2$, the radical reaction and the adsorptivity and absorptivity of the MWCNTs.

• Applied Science and Convergence Technology
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• v.24 no.4
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• pp.96-101
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• 2015

Quantitative evaluation of photocatalytic activity of oxide nanoparticles in aqueous solution is quite challenging in that the kinetic reaction rate is determined by a complicated interplay among various limiting factors such as light scattering and absorption, diffusion and adsorption of reactants in condensed liquid phase, photoexcited charge separation and recombination rate, and the exact nature of active sites determined by detailed morphology and crystallinity of nanocrystals. Here, we present our simple experimental results showing that the kinetic regime of a typical photocatalytic degradation experiment over UV-irradiated $TiO_2$ nanoparticles in aqueous solution is in that dominated by the photoactivity of $TiO_2$ and its concentration. This result lays a firm ground of using the measured kinetic reaction rate in evaluating photocatalytic efficiency of oxide nanocrystals under evaluation.

• Journal of Korean Society for Atmospheric Environment
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• v.19 no.1
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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.

• Journal of the Korean Applied Science and Technology
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• v.26 no.4
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• pp.473-482
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• 2009

Titanium dioxide particles are used as cosmetics, pigments, photocatalysts, adsorbents, catalytic supports, and sensors. The $TiO_2$ particles were prepared by the precipitation in TTIP/Solvent mixtures and calcined at different temperatures. The resulting materials were characterized by XRD and SEM testing techniques. The $TiO_2$ particles phase composition was determined by XRD ranging from amorphous to crystalline anatase and rutile largely proportional to the calcination temperature.