• Title/Summary/Keyword: $TiO_{2-x}$

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Low Temperature Preparation and Photocatalytic Activity of TiO{2-x}Nx (TiO{2-x}Nx의 저온제조 및 광화학적 특성)

  • Jung, Dong-Woon
    • Journal of the Korean Chemical Society
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    • v.54 no.1
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    • pp.120-124
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    • 2010
  • $TiO_2$ and N-substituted $TiO_{2-x}N_x$ were synthesized by using precipitation method. $TiO_{2-x}N_x$ compound absorbed whole UV light as well as long wavelength of visible light (400 - 700 nm) because of the change of band gap from 3.2 eV to 1.77 eV. Results obtained revealed that $TiO_{2-x}N_x$ showed higher activity than pure $TiO_2$ or P-25 for visible-photocatalytic degradation of 1,4-dichlorobenzene.

Microwave Dielectric Properties of the $(1-x)Mg_4Ta_2O_9-x(TiO_2,\;CaTiO_3,\;SrTiO_3)$ Ceramics ($(1-x)Mg_4Ta_2O_9-x(TiO_2,\;CaTiO_3,\;SrTiO_3)$ 세라믹스의 마이크로파 유전 특성)

  • Kim, Jae-Sik;Choi, Eui-Sun;Bae, Seon-Gi;Lee, Young-Hie
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.55 no.7
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    • pp.344-348
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    • 2006
  • The effect of x on microwave dielectric properties of the $(1-x)Mg_4Ta_2O_9-x(TiO_2,\;CaTiO_3,\;SrTiO_3)$ ceramics for microwave components were investigated. All spcecimens prepared by the conventional mixed oxied method and sintered at $1450^{\circ}C$. Microwave dielectric properties of the $(1-x)Mg_4Ta_2O_9-xTiO_2$ ceramics were influenced by $MgTi_2O_5$ phase. Also the microwave dielectric properties of the $(1-x)Mg_4Ta_2O_9-x(TiO_2,\;CaTiO_3,\;SrTiO_3)$ ceramics were dominated with an addition of $CaTiO_3\;and\;SrTiO_3$. The dielectric constant $(\varepsilon_r)$, quality factor $(Q{\times}f_r)$ and temperature coefficient of the resonant frequency $(TCRF,\;\tau_f)$ of the $(1-x)Mg_4Ta_2O_9-x(TiO_2,\;CaTiO_3,\;SrTiO_3)$ ceramics were $12.96\sim70.98,\;5,132\sim186,410GHZ$ and $-35.82\sim+75.96ppm/^{\circ}C$, respectively, and depend on x and addition materials.

Photocatalytic and Antipathogenic Effects of TiO2/CuxO (1 (TiO2/CuxO (1)

  • Cho, Sungwoo;Lee, Yong-Im;Kim, Lee-Han;Jung, Dongwoon
    • Journal of the Korean Chemical Society
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    • v.57 no.4
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    • pp.483-488
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    • 2013
  • Copper oxide (CuO) was synthesized from $CuCl_2$ by solution method. Anatase $TiO_2$ particle was dispersed into the solution before preparing CuO, so that $TiO_2$/CuO heterojunction was created through the nucleation of CuO onto the $TiO_2$ surface. Some amount of CuO was reduced to $Cu_2O$ by treating glucose into the solution, thereby preparing $TiO_2/Cu_xO$ complex. The obtained $TiO_2/Cu_xO$ complex showed advanced phtocatalytic activity under the sun light compared with the P-25 sample. In addition, the the $TiO_2/Cu_xO$ complex showed excellent antipathogenic effect.

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.

Steam Reforming of Hydrothermal Liquefaction Liquid from Macro Algae over Ni-K2TixOy Catalysts (Ni-K2TixOy 촉매를 이용한 해조류 유래 수열 액화 원료의 수증기 개질 반응 연구)

  • Park, Yong Beom;Lim, Hankwon;Woo, Hee-Chul
    • Clean Technology
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    • v.23 no.1
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    • pp.104-112
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    • 2017
  • Hydrogen production via steam reforming of liquefaction liquid from marine algae over hydrothermal liquefaction was carried out at 873 ~ 1073 K with a commercial catalyst and Ni based $K_2Ti_xO_y$ added catalysts. Liquefaction liquid obtained by hydrothermal liquefaction (503 K, 2 h) was used as a reactant and comparison studies for catalytic activity over different catalysts (FCR-4-02, $Ni/K_2Ti_xO_y-Al_2O_3$, $Ni/K_2Ti_xO_y-SiO_2$, $Ni/K_2Ti_xO_y-ZrO_2/CeO_2$ and Ni/$K_2Ti_xO_y$-MgO), reaction temperature were performed. Experimental results showed Ni/$K_2Ti_xO_y$ based catalysts ($Ni/K_2Ti_xO_y-Al_2O_3$, $Ni/K_2Ti_xO_y-SiO_2$, Ni/$K_2Ti_xO_y-ZrO_2$/ $CeO_2$ and Ni/$K_2Ti_xO_y$-MgO) have a higher activity than commercial catalyst (FCR-4-02) and In particular, a product composition was different depending on support materials. An acidic support ($Al_2O_3$) and a basic support (MgO) led to a higher selectivity for CO while a neutral support ($SiO_2$) and a reducing support ($ZrO_2/CeO_2$) resulted in a higher $CO_2$ selectivity due to water gas shift reaction.

Stable Defect Structure of La2O3-Modified BaTiO3 (La$_2O_3$-변형 BaTi$O_3$의 안정한 결함구조)

  • Kim, Jeong Su;Park, Hyu Beom;An, Tae Ho;Kim, Si Jung
    • Journal of the Korean Chemical Society
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    • v.38 no.4
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    • pp.309-318
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    • 1994
  • The stable defect structure and the single phase region of La$_2O_3$-modified BaTi$O_3$ have been studied by X-ray diffractometer and scanning electron microscope. The stable defect structure of La$_2O_3$-modified BaTi$O_3$ has been identified as [($Ba^x_{Ba})_{1-2x}(La{\cdot}_{Ba})_{2x}][Ti^x_{Ti})_{1-x/2}(V""_{Ti})_{x/2}]O_3$ which consists of La$^{3+}$ ion substitution for Ba$^{3+}$ ion in the lattice structure and the formation of Ti vacancies for the charge compensation. When 3 mol% of La$_2O_3{\cdot}3/2TiO_3$ was added to BaTi$O_3$, the unit cell structure was transformed from tetragonal to cubic and the solubility limit was about 14 mol%. When La$_2O_3{\cdot}3/2TiO_2$ was added above this solubility limit, the second phase, La$_4Ba_2Ti_5O_{18}$, was formed. In the La$_2O_3$-modified BaTi$O_3$, it was found by the liquid phase sintering process that the sinterability was decreased by excess BaO but increased by excess Ti$O_2$.

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UV Absorption of Nano-thick $TiO_2$ Prepared Using an ALD (ALD 방법으로 제조된 나노급 $TiO_2$에 의한 자외선 차단효과 연구)

  • Han, Jeung-Jo;Song, Oh-Sung;Ryu, Ji-Ho;Yoon, Ki-Jeong
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.8 no.4
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    • pp.726-732
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    • 2007
  • We fabricated UV absorption functional $10{\sim}50nm-TiO_{2-x}/quartz$ structures layer using ALD (atomic layer deposition) method. We deposited $10nm-TiO_{2-x}$ layer on quartz substrate using ALD, and film thickness was determined by an ellipsometer. The others specimen thickness was controlled by ALD time lineally. We characterized controlling phase UV and visible optical property using an X-ray difractometer, a UV-VIS-IR spectrometer and a digital camera. $ALD-TiO_{2-x}$ layers were non-stoichiometric $TiO_{2-x}$ form and amorphous phases comparing with bulk $TiO_2$. While the conventional bulk $TiO_2$ had band gap of $3.0{\sim}3.2eV$ resulting in absorption edges at 380 nm and 415 nm, $ALD-TiO_{2-x}$ layers showed absorption edges at 197 nm and 250 nm. Therefore, our nano-thick $ALD-TiO_{2-x}$ was able to absorb shorter UV region and showed excellent transmittance in visible region. Our result implies that our newly proposed nano-thick $TiO_{2-x}$ using ALD process may improve transmittance in visible rays and be able to absorb shorter UV light effectively.

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Phase Relation and Microwave Dielectric Properties of $BaO-(Nd, Sm)_2O_3-TiO_2$ Ceramic System ($BaO-(Nd, Sm)_2O_3-TiO_2$계 세라믹스의 상관계 및 마이크로파 유전특성)

  • 김희도;김진호;조상희
    • Journal of the Korean Ceramic Society
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    • v.31 no.9
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    • pp.995-1004
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    • 1994
  • Phase relation and microwave dielectric properties of the system BaO.(Nd1-xSmx)2O3.TiO2 (n=4, 5) were studied. With n=5 (1 : 1 : 5), Ba2Ti9O20 and TiO2 formed in case of X$\leq$0.7, and Ba2Ti9O20 and Sm2Ti2O7 formed at X=1.0 as the second phases dispersed in fine-grained orthorhombic matrix phase. With n=4 (1 : 1 : 4). on the contrary, only fine grains of an ortho-rhombic phase were observed irrespective of Nd/Sm ratio. The compositions of these two stable orthorombic phases having distinct lattic constants even with the same Nd/Sm ratio were estimated as 4BaO.5(Nd1-xSmx)2O3.18TiO2 and BaO.(Nd1-xSmx)2O3.4TiO2 with n=5 and n=4 in the system BaO.(Nd1-xSmx)2O3.TiO2, respectively. Consequently the composition BaO.(Nd1-xSmx)2O3.5TiO2 lies in the compatible triangle of 4BaO.5(Nd1-xSmx)2O3.18TiO2 and the second phases mentioned above. The microwave dielectric properties (~4 GHz) of BaO.(Nd1-xSmx)2O3.5TiO2 can be controlled effectively by adjusting Sm content : with increasing X from 0 to 0.7, both dielectric constant and the temperature coefficient of resonant frequency decreased monotonically from 82 to 65 and from 91 (ppm/$^{\circ}C$) to -19(ppm/$^{\circ}C$), respectively, while unloaded Q(Qo) remained constant at about 2,600.

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WOx Doped TiO2 Photocatalyst Nano Powder Produced by Sonochemistry Method (초음파 화학 반응을 이용한 WOx 도핑 TiO2 광촉매 나노 분말의 합성)

  • Cho, Sung-Hun;Lee, Soo-Wohn
    • Korean Journal of Materials Research
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    • v.21 no.2
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    • pp.83-88
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    • 2011
  • Nano-technology is a super microscopic technology to deal with structures of 100 nm or smaller. This technology also involves the developing of $TiO_2$ materials or $TiO_2$ devices within that size. The aim of the present paper is to synthesize $WO_x$ doped nano-$TiO_2$ by the Sonochemistry method and to evaluate the effect of different percentages (0.5-5 wt%) of tungsten oxide load on $TiO_2$ in methylene blue (MB) elimination. The samples were characterized using such different techniques as X-ray diffraction (XRD), TEM, SEM, and UV-VIS absorption spectra. The photo-catalytic activity of tungsten oxide doped $TiO_2$ was evaluated through the elimination of methylene blue using UV-irradiation (315-400nm). The best result was found with 5 wt% $WO_x$ doped $TiO_2$. It has been confirmed that $WO_x-TiO_2$ could be excited by visible light (E<3.2 eV) and that the recombination rate of electrons/holes in $WO_x-TiO_2$ declined due to the existence of $WO_x$ doped in $TiO_2$.

The Effect of $WO_3$ Addition on Microwave Dielectric Properties in $BaTiO_3-3{(1-x)TiO_2-xWO_3}$ System ($WO_3$ 첨가량 변화에 따른 $BaTiO_3-3{(1-x)TiO_2-xWO_3}$ 계의 고주파 유전특성)

  • 박찬식;변재동;김왕섭;김경용
    • Journal of the Korean Ceramic Society
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    • v.32 no.4
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    • pp.448-454
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    • 1995
  • The effect of WO3 addition on microwave dielectric properties of BaTiO3-3{(1-x)TiO2-xWO3} system was studied. Addition of WO3 to this system resulted in the formation of BaWO4 and Ba2Ti9O20 phases. Both the dielectric constant (K) and the temperature coefficientof resonant frequency (Tf) were decreased with the amount of WO3 addition. The value of Q$\times$f0 was increased as the amount of WO3 was increased up to x=0.0275, and then decreased when x exceeded 0.03. At x=0.0275, this ceramic showed excellent microwave proprties of K=34-35, Q$\times$f0=50,000-53,000, and near zero ppm/$^{\circ}C$ of Tf.

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