• Title, Summary, Keyword: $TiO_2$

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Photocatalytic Degradation of a Congo red Using ZnO/rutile-$TiO_2$, ZnO, rutile-$TiO_2$ and CdS (ZnO/rutile-$TiO_2$, ZnO, rutile-$TiO_2$, CdS를 이용한 Congo red의 광 촉매 분해반응)

  • Kim, Chang Suk;Ryu, Hae-Ill
    • Analytical Science and Technology
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    • v.14 no.3
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    • pp.259-265
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    • 2001
  • Photocatalytic degradation of Congo red was performed using various semiconductors as ZnO, CdS, rutile-$TiO_2$ or mixed rutile-$TiO_2$/ZnO. The change of degradation of the dye was investigated by UV-visible spectrophotometric method. The photocatalytic action of CdS was greater than ZnO and rutile-$TiO_2$ in account of low band gap energy of CdS. The rate of photocatalytic degradation reaction increased drastically in according to increasing ratio of ZnO on mixed rutile-$TiO_2$/ZnO. These photocatalytic effect of rutile-$TiO_2$ was suppressed by more stable rutile-$TiO_2$, doping the hydrolysis product with $Zn^{2+}$ prior to calcination onto the rutile-$TiO_2$ surface.

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Synthesis and Characterization of Transition Metal Doped $TiO_2$ Thin Films: $Fe_xTi_{1-x}O_2$ (전이금속이 도핑된 $TiO_2$ 박막의 제조와 특성 규명: $Fe_xTi_{1-x}O_2$)

    • Journal of the Korean Vacuum Society
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    • v.11 no.4
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    • pp.240-248
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    • 2002
  • $Fe_xTi_{l-x}O_2$ films (x=0.07 and 0.16) were grown by oxygen-plasma-assisted molecular beam epitaxy on rutile $TiO_2$(110). The same growth conditions were applied for both films in order to determine surface characteristics of grown films as a function of Fe composition. The films were characterized by several surface analysis techniques. The oxidation states of Ti and Fe in $Fe_xTi_{l-x}O_2$ films were found to be +4 and a mixture of +2 and +3, respectively. More $Fe^{3+}$ species exist in higher Fe doped film of $Fe_{0.16}Ti_{0.84}O_2$. The morphology of $Fe_{0.07}Ti_{0.93}O_2$ film shows tall rectangular and cylinderical islands growth on flat substrate-like surface. On the other hand, $Fe_{0.16}Ti_{0.84}O_2$ film consists of round shaped small islands showing somewhat rougher surface compared to the surface of $Fe_{0.16}Ti_{0.84}O_2$ film.

Correlation between Physicochemical Properties of Various Commercial TiO2 Supports and NH3-SCR Activities of Ce/Ti Catalysts (다양한 상용 TiO2 담체의 물리화학적 특성과 Ce/Ti 촉매의 SCR 반응활성과의 상관성 연구)

  • Kwon, Dong Wook;Hong, Sung Chang
    • Applied Chemistry for Engineering
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    • v.26 no.2
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    • pp.193-198
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    • 2015
  • Ceria supported on various commercial $TiO_2$ catalysts were prepared by wet-impregnation method. We confirmed that the correlation between physicochemical properties of $TiO_2$ supports and SCR activities. Physicochemical properties of the various $TiO_2$ were evaluated using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area, X-ray photoelectron spectroscopy (XPS), and pH analysis. Ce/Ti catalyst exhibited different SCR activities with respect to physicochemical properties of $TiO_2$. An excellent activity was obtained as the surface area of $TiO_2$ increased. In the case of CeOx surface density, the excellent activity in a range of $2.5{\sim}14.5CeOx/nm^2$ was achieved and the activity tended to decrease above $14.5CeOx/nm^2$. The O/Ti mole ratio of $TiO_2$ in the range of 1.32 to 1.79 showed an excellent SCR activity. It was also confirmed that the pH of the $TiO_2$ has no effects on the SCR activity. In order to achieve excellent SCR activities, ceria oxide should be supported on $TiO_2$ possessing a high specific surface area and certain O/Ti mole ratio. In addition, the catalyst with the low CeOx surface density resulted from the high dispersed ceria oxide should be prepared.

Influence of Nitrogen Doping and Surface Modification on Photocatalytic Activity of $TiO_2$ Under Visible Light

  • Jeong, Bora;Park, Eun Ji;Jeong, Myung-Geun;Yoon, Hye Soo;Kim, Young Dok
    • Proceedings of the Korean Vacuum Society Conference
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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.

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Photocatalysis and Adsorption of Reactive Black 5(RB5) by HAP/TiO2 Media (HAP/TiO2 여재를 이용한 Reactive Black 5(RB5)의 광촉매 반응과 흡착)

  • Chun, Sukyoung;Chang, Soonwoong
    • Journal of the Korean GEO-environmental Society
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    • v.12 no.11
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    • pp.31-37
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    • 2011
  • This study investigated on the adsorption and photocatalysis of Reactive Black 5(RB5) by the hydroxyapatite(HAP)/Titanium dioxide($TiO_{2}$) media. The adsorption of RB5 on $TiO_{2}$, HAP and $TiO_{2}$/HAP was investigated during a series of batch adsorption experiments. The amounts adsorbed at equilibrium were measured. Langmuir and Freundlich isotherm models were tested for their applicability. The result of equilibrium studies of $TiO_{2}$, HAP and $TiO_{2}$/HAP adsorbent were found to follow Langmuir isotherm model. The adsorbed amounts(Qmax) were found to be 5.28mg/g on single $TiO_{2}$, 12.45mg/g on single HAP and 9.03mg/g on $TiO_{2}$/HAP, respectively. The experimental data were analysed using the pseudo-first-order adsorption and photocatalysis kinetic models. According to these models, RB5 degradation by $TiO_{2}$/HAP was affected by interaction effect of photocatalysis and adsorption.

The effect of Zn2TiO4 on willemite crystalline glaze (Zn2TiO4가 아연결정유약에 미치는 효과)

  • Lee, Chi-Youn;Lee, Hyun-Soo;Shin, Kyung-Hyun
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.24 no.2
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    • pp.70-76
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    • 2014
  • $Zn_2TiO_4$, using an anatase form of $TiO_2$ on zinc crystalline glaze, was shown as effective nuclear agent. Thus the effects on glaze were studied with synthesized $Zn_2TiO_4$ at low temperature. First, the chromophore elements were employed in synthesized $Zn_2TiO_4$ then add them in the zinc crystalline glaze. Crystal creation and development of color by $Zn_2TiO_4$ addition on the zinc crystalline glaze were more effective. Addition of $Zn_2TiO_4$, which is developed in low range temperature, is effected as zinc crystalline nuclear in the willemite glaze. When 5 wt% of synthesized $Zn_2TiO_4$ was added to the willemite glaze, nuclear creation increases and steadily retains. Therefore addition of respectively doped $Zn_2TiO_4$ with CoO, NiO, and CuO would increase doped effects in the glaze, various color willemite crystal were obtained.

A Study on Solid Reaction of BaCO3-TiO2 System (BaCO3-TiO2계의 고상반응에 관한 연구)

  • 이응상;황성연;임대영
    • Journal of the Korean Ceramic Society
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    • v.24 no.5
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    • pp.484-490
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    • 1987
  • Diffusion coupling experiment was done to study expansion of body and soild reaction in BaCO3-TiO2 system. Specimen of BaCO3 and TiO2 was formed with Pt-mark's method. Each specimen was fired at interval of 25℃ from 900℃ to 1000℃ for 2hrs. After that, specimen was fixed with resin and polished. Product layers of specimen were observed with SEM and EDS. The result were following; 1. Diffusion component is Ba2+, which diffuse toward TiO2. 2. Large crack between layer of BaCO3 and Ba2TiO4 was generated because of difference of thermal expansion coefficient. 3. Ba2TiO4 is formed to TiO2 body by the reaction of BaTiO3 and BaO and its structure is very porous. 4. BaTiO3 changes immediately to Ba2TiO4 by the reaction of BaO. But BaTiO3 which formed by the reaction of TiO2 and Ba2TiO4 exsists as layer because the diffusion distance of Ba2+ is far.

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The Changes of CO Gas Sensing Properties of ZnO and $SnO_2$ with Addition $TiO_2$ ($TiO_2$첨가에 의한 ZnO와 $SnO_2$의 일산화탄소 감응특성 변화)

  • Kim, Tae-Won;Choi, U-Sung;Jun, Seon-Taek
    • Korean Journal of Materials Research
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    • v.8 no.4
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    • pp.312-316
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    • 1998
  • ZnO- TiO$_2$, and Sn0$_2$ - Ti0$_2$ ceramic composites doped with TiO$_2$ were prepared and their electrical and 1000ppm CO gas sensing properties were investigated. The phases of samples were analyzed by XRD, and the microsturctures of the fractured surface of samples were observed by SEM. A carbon monoxide gas sensitivity was de¬fined as the ratio of the resistance in dry air atmosphere(R$drt air$) to the resistance in 1000ppm CO gas atmosphere(R$_co$) The CO gas sensitivity of Smol% Ti0$_2$-added ZnO decreased about 1.7 times compared to that of pure ZnO. On the other hand, the maximum CO gas sensitivity of Ti0$_2$-added SnO$_2$ increased about 2.5 times compared to that of pure SnO$_2$. Therefore, the CO gas sensitivies of SnO$_2$-TiO$_2$ composite were better than those of ZnO- Ti0$_2$ and the temper¬ature range showing the maximum sensitivity for Sn0$_2$-TiO$_2$ composite was lower than that for ZnO- Ti0$_2$.

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Effects of $Nd_2O_3$ and $TiO_2$ Addition on the Microstructures and Microwave Dielectric Properties of $BaO-Nd_2O_3-TiO_2$ System

  • Kim, Tea-Hong;Park, Jung-Rae;Lee, Suk-Jin;Sung, Hee-Kyung;Lee, Sang-Seok;Choy, Tae-Goo
    • ETRI Journal
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    • v.18 no.1
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    • pp.15-27
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    • 1996
  • The effects of $Nd_2O_3$ and $TiO_2$ addition on the microstructures and microwave dielectic properties of $BaO-Nd_2O_3-TiO_2$ system were investigated. $BaNd_2Ti_4O_{12}$ or $BaNd_2Ti_{5}O_{14}$ phases were observed for compositions based on BaO/$Nd_2O_3$ = 1 ratio. The compositions deviated from $BaO/Nd_2O_3=1$ ratio were composed of major phases of $BaNd_2Ti_4O_{12}$ or $BaNd_2Ti_5O_{14}$, and the compound of $Nd_2O_3$ and $TiO_2(Nd_2Ti_2O_7)$ or that of BaO and $TiO_2(BaTi_4O_9)$. The microstructure of ceramic with $BaO{\cdot}Nd_2O_3{\cdot}4TiO_2$ composition varied from spherical grains to needlelike grains with increasing sintering temperature. With increasing $Nd_2O_3$, the optimum sintering temperature with maximum density increased, and the dielectric constant(${\varepsilon}_r$) and quality factor(Q) decreased due to the formation of secondary phases. With increasing $TiO_2$, the optimum sintering temperature and the dielectric constant decreased with increased Q value. And the temperature coefficient of resonant frequency, ${\tau}_f$ shifted toward positive direction. The dielectric ceramics with $BaO/Nd_2O_3=1$ showed Q values of above 2000 and dielectric constants of above 80 at 3GHz.

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The Dielectrical Properties of $(1-x)(Sr_a.Pb_b.Ca_c)TiO_3-xB_i2O_3.TiO_2$ system affected by $Bi_2O_3.3TiO_2$ amounts and $MnO_2$ ($(1-x)(Sr_a.Pb_b.Ca_c)TiO_3-xB_i2O_3.TiO_2$계에서의 $Bi_2O_3.3TiO_2$$MnO_2$첨가에 따른 유전특성에 관한 연구)

  • 박상도;이응상
    • Journal of the Korean Ceramic Society
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    • v.34 no.2
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    • pp.123-130
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    • 1997
  • In this study, (Sr.Pb.Ca)TiO3-Bi2O3.3TiO2(SPCT) systems were investigated to develop a new material which has a high dielectric constant, a low dielectric loss and a small TCC(Temperature Coefficient of Capa-citance), and are suitable for high voltage applications as a function of the additions of Bi2O3.3TiO2 from 5 mol.% to 9 mol.%. The result obtained from our investigation showed that up to 6 mol.% Bi2O3.3TiO ad-dition the dielectric constant increased and it deteriorated at higher concentrations with increasing amount of the acicular grains. As a result of some dopants (SiO2, Nb2O3, MnO2) addition to SPCT, the specimens with MnO2 showed good dielectric properties. The dielectric constant decreased, but the TCC was improved with the addition of MnO2 from 0.15 wt.% to 0.45 wt. %.

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