• Title/Summary/Keyword: $TiO_2/TiOF_2$

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Behaviors of Abnormal Expansion in $Ba_2Ti_9O_{20}$ Ceramics during Calcination Process ($Ba_2Ti_9O_{20}$ 요업체의 하소공정중 이상팽창 거동)

  • 성제홍;김정주;김남경;조상희
    • Journal of the Korean Ceramic Society
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    • v.36 no.12
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    • pp.1327-1334
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    • 1999
  • Behaviors of abnormal expansion during calcination process of Ba2Ti9O20 ceramics and its related effects on the sintering characteristics were investigated as a function of precursors. When BaCO3 and TiO2 powders were used as starting materials. BaTi4O9 phase which has relatively large molar volume was formed drastically with abnormal ex-pansion during the calcination at 95$0^{\circ}C$ to 115$0^{\circ}C$ ON the contrary using BaTiO3 and TiO2 powders as starting materials led to retardation of the formation of BaTi4O9 phase and concurrently suppressed the abnormal expansion during cal-cination process. Especially the calcined powder of BaTiO3 and TiO2 had advantages in the densification and formation of Ba2Ti9O20 single phase in the sintering process.

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Evaluation of Visible-light activation of Cu2O-TiO2 (P-N type) Semiconductor Nanomaterials prepared by Ultrasonic-assisted Synthesis (초음파 합성 적용 Cu2O-TiO2 (P-N 타입) 반도체 나노물질의 가시광 활성 평가)

  • Shin, Seung-ho;Choi, Jeong-Hak;Kim, Ji-hoon;Lee, Joon Yeob
    • Journal of Environmental Science International
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    • v.28 no.11
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    • pp.971-981
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    • 2019
  • This study evaluated the photocatalytic oxidation efficiency of volatile organic compounds by $Cu_2O-TiO_2$ under visible-light irradiation. $Cu_2O-TiO_2$ was synthesized by an ultrasonic-assisted method. The XRD result indicated successful p-n type photocatalysts. However, no diffraction peaks belonging to $TiO_2$ were observed for the $Cu_2O-TiO_2$. The Uv-vis spectra result revealed that the synthesized $Cu_2O-TiO_2$ can be activated under visible-light irradiation. The FE-TEM/EDS result showed the formation of synthesized nanocomposites in the commercial P25 $TiO_2$, the undoped $TiO_2$, and $Cu_2O-TiO_2$ and componential analysis in the undoped $TiO_2$ and $Cu_2O-TiO_2$. The photocatalytic oxidation efficiencies of benzene, toluene, ethylbenzene, and o-xylene with $Cu_2O-TiO_2$ were higher than those of P25 $TiO_2$ and undoped $TiO_2$. These results indicate that the prepared $Cu_2O-TiO_2$ photocatalyst can be applied effectively to control gaseous BTEX.

Aging Effect on the Antimicrobial Activity of Nanometal (Au, Ag)-Titanium Dioxide Nanocomposites (Aging 효과에 따른 나노메탈(Au, Ag)-이산화티탄 복합체의 항균 활성도)

  • Park, Hye-Rim;Lee, Sang-Wha;Yoo, In-Sang
    • Applied Chemistry for Engineering
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    • v.23 no.3
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    • pp.293-296
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    • 2012
  • Nanocomposites were fabricated as titanium dioxide ($TiO_2$) doped with nanometals (Au, Ag) by sonochemical reduction method and sol-gel method in order to investigate their antimicrobial activities. Then, the antimicrobial activity of the resulting samples was compared by the measurement of colony numbers survived on the agar plate incubated for 24 h after the loading E. coli on the solid-state media with the nanocomposites. The initial antimicrobial activity of the metal (Au, Ag)-doped $TiO_2$ was higher than that of the pristine $TiO_2$. Afterwards the nanocomposite samples were kept at $4^{\circ}C$ for a long time and the aged samples exhibited the different antimicrobial activity. With the elapse of aging times, Ag-doped $TiO_2$ with $TiO_2$ coating ($Ag-TiO_2$@$TiO_x$) exhibited the higher antimicrobial activity than those of $Ag-TiO_2$and $Au-TiO_2$. The $TiO_2$ coating on the $Ag-TiO_2$ may prevent the oxidation of Ag nanometals and stabilize colloidal nanocomposites.

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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Development of Pd/TiO2 Catalysts with La2O3 Addition and Study on the Performance Improvement of H2 Oxidation at Room Temperature (La2O3가 첨가된 Pd/TiO2 촉매의 개발 및 H2 상온산화 반응에서의 성능 향상 연구)

  • Lee, Dong Yoon;Kim, Sung Chul;Lee, Sang Moon;Kim, Sung Su
    • Applied Chemistry for Engineering
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    • v.31 no.6
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    • pp.674-678
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    • 2020
  • In this study, a Pd/TiO2 catalyst which oxidized H2 at room temperature without an additional energy source was prepared. And a specific surface area of TiO2 as a support was not proportional to H2 oxidation reaction performance of Pd/TiO2 catalyst. In addition La2O3 was added to Pd/TiO2 catalyst in order to evaluate the performance effect due to the change of catalysts physical properties. A Pd/La2O3-TiO2 was prepared by adding different amounts of La2O3 to TiO2 and CO chemisorption analysis was performed. Compared to the conversion rate (14% at 0.5% H2) of the Pd/TiO2(G) catalyst, the Pd/La2O3-TiO2 catalyst showed 74% which was improved by more than five times. It was found that the larger the metal dispersion of Pd as an active metal is, the more favorable to H2 oxidation reaction is. However, when the added La2O3 amount exceeded 10%, the catalyst performance decreased again. Finally, it was concluded that the physical properties of the Pd/La2O3-TiO2 catalyst have a dominant influence on the catalytic activity until 0.3~0.5% of injected H2 concentrations and the catalyst reaction rate was controlled by substance transfer from 1% or more concentrations of H2.

Synthesis of TiO2-xNx Using Thermal Plasma and Comparison of Photocatalytic Characteristics (열플라즈마에 의한 TiO2-xNx의 합성 및 광촉매 특성 비교)

  • Kim, Min-Hee;Park, Dong-Wha
    • Applied Chemistry for Engineering
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    • v.19 no.3
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    • pp.270-276
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    • 2008
  • $N_2$ doped $TiO_2$ nano-sized powder was prepared using a DC arc plasma jet and investigated with XRD, BET, SEM, TEM, and photo-catalytic decomposition. Recently the research interest about the nano-sized $TiO_2$ powder has been increased to improve its photo-catalytic activity for the removal of environmental pollutants. Nitrogen gas, reacting gas, and titanium tetrachloride ($TiCl_4$) were used as the raw materials and injected into the plasma reactor to synthesize the $N_2$ doped $TiO_2$ power. The particle size and XRD peaks of the synthesized powder were analyzed as a function of the flow rate of the nitrogen gas. Also, the characteristics of the photo-catalytic decomposition using the prepared powder were studied. For comparing the photo-catalytic decomposition performance of $TiO_2$ powder with that of $TiO_2$ coating, $TiO_2$ thin films were prepared by the spin coating and the pulsed laser deposition. For the results of the acetaldehyde decomposition, the photo-catalytic activity of $TiO_{2-x}N_x$ powder was higher than that of the pure $TiO_2$ powder in the visible light region. For the methylene blue decomposition, the decomposition efficiency of $TiO_2$ powder was also higher than that of $TiO_2$ film.

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.

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 of $BaTi_4O_9, Ba_2Ti_9O_{20}$ and $BaTi_5O_{11}$ Compounds by Coprecipitation Method and Their Electrical and Thermal Properties (공침법에 의한 $BaTi_4O_9, Ba_2Ti_9O_{20}$$BaTi_5O_{11}$화합물의 합성 및 그의 전기적, 열적 특성)

  • 김종옥;손우창;전성용;이경희;이병하
    • Journal of the Korean Ceramic Society
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    • v.31 no.9
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    • pp.1005-1011
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    • 1994
  • The three different composition of BaTi4O9, Ba2Ti9O20 and BaTi5O11 were prepared by coprecipitation process, and then the dielectric properties of these compounds were measured at low microwave frequencies. The powder showing high level of purity was synthesised by the coprecipition reaction of BaCl2 and TiCl4 where (NH4)2CO3 and NH4OH were used as a deflocculent. Followings are the result of this study: 1. The sintering temperature increased with increasing TiO2 content. 2. BaTi4O9 powder were synthesized as a single phase by this processing technique, but the resultant Ba2Ti9O20 and BaTi5O11 phase existed with Ba2Ti9O20 and BaTi5O11 phases. 3. Single phase BaTi4O9 showed high dielectric constant value of 35, high Q value of 8100.

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