• Title, Summary, Keyword: $TiO_2$

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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.

Structural and Morphological Behavior of TiO2 Rutile Obtained by Hydrolysis Reaction of Na2Ti3O7

  • Lee, Seoung-Soo;Byeon, Song-Ho
    • Bulletin of the Korean Chemical Society
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    • v.25 no.7
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    • pp.1051-1054
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    • 2004
  • The structural transformation behavior of $Na_2Ti_3O_7$ by hydrolysis was investigated in mild and strong acidic aqueous medium. Compared with $K_2Ti_4O_9,\;Na_2Ti_3O_7$ exhibits quite different structural and morphological transformation behavior despite their similar layered structural characteristics. $TiO_2(B)$ obtained by heat treatment of $H_2Ti_3O_7\;at\;350^{\circ}C$ transforms to rutile $H_2Ti_3O_7\;at\;900^{\circ}C$. This temperature is much lower than $1200{\circ}C$, the temperature for anatase to rutile transition when $K_2Ti_4O_9$ is used as a starting titanate. A rectangular rod shape and size of $TiO_2(B)$ particles obtained from $Na_2Ti_3O_7$ is also different from a fibrous structure of $TiO_2(B)$ prepared using $K_2Ti_4O_9$. Rutile crystals of 100 nm diameter with a corn-like morphology and large surface area are directly obtained when the hydrolysis of $Na_2Ti_3O_7$ is carried out at $100^{\circ}C$ in a strong acid solution. The structure of starting titanates and the hydrolysis conditions are an important factor to decide the particle size and morphology of $TiO_2(B)\;and\;TiO_2$.

Photocatalayst and Decomposition Properties of TiO2 and TiO2-CdS Powders Prepared by Supercritical Fluid Method (초임계 유체법으로 제조한 TiO2 및 TiO2-CdS계 광촉매의 분해물성 연구)

  • 전일수;황수현;박상준;길현식;조승범;전명석;임대영
    • Journal of the Korean Ceramic Society
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    • v.41 no.6
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    • pp.481-484
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    • 2004
  • TiO$_2$ and TiO$_2$-CdS powders which were expected to be highly activated photocatalysts were prepared using supercritical fluid method (SCF). The prepared photocatalyst TiO$_2$ powders were crystalline of anatase and ultrafine spherical powders with large specific surface area. When photodecompositoion reaction was done with TiO$_2$ powders prepared by SCF as a photocatalyst in DCA (Dichloroactic Acid) solution, a hazardous organic compound, the photocatlyst, properties of TiO$_2$ powders prepared by SCF were better than that of commercial TiO$_2$ powders.

Investigation on the Preparation Method of TiO2-mayenite for NOx Removal (질소산화물 제거를 위한 TiO2-mayenite 제조 방법에 관한 연구)

  • Park, Ji Hye;Park, Jung Jun;Park, Hee Ju;Yi, Kwang Bok
    • Clean Technology
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    • v.26 no.4
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    • pp.304-310
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    • 2020
  • In order to apply a photocatalyst (TiO2) to various building materials, TiO2-mayenite was prepared in this study. The TiO2 was synthesized using the sol-gel method by fixing titanium isopropoxide (TTIP) and urea at a ratio of 1 : 1. Later, they were calcined in a temperature range of 400-700 ℃ to analyze the properties according to temperature. BET, TGA, and XRD were used to analyze the physical and chemical properties of TiO2. The nitrogen oxide removal test was confirmed by measuring the change in the concentration of NO for 1 h according to KS L ISO 22197-1. The prepared TiO2 samples exhibited an anatase crystal structure below 600 ℃, and TiO2 (urea)-400 showed the highest nitrogen oxide removal rate at 2.35 µmol h-1. TiO2-mayenite was prepared using two methods: spraying TiO2 dispersion solution (s/s) and sol-gel solution (g/s). Through BET and XRD analysis, it was found that 5-TiO2 (g/s) prepared by spraying a sol-gel solution has maintained its crystallinity even after heat treatment. Also, 5-TiO2 (g/s)-500 showed the highest removal rate of 0.55 µmol h-1 in the nitrogen oxide removal test. To prepare TiO2-mayenite, it was confirmed that mayenite should be blended with TiO2 in a sol-gel state to maintain the crystal structure and exhibit a high nitrogen oxide removal rate.

Photoelectrical Conductivity and Photodegradation Properties of $TiO_2$ and Ag Sputtered $TiO_2$ Plasma Spraying Coatings ($TiO_2$ 및 Ag 스퍼터링-$TiO_2$ 플라즈마 용사피막의 광전류 및 광분해 특성)

  • Kang, Tae-Gu;Jang, Yong-Ho;Park, Kyeung-Chae
    • Journal of Welding and Joining
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    • v.27 no.2
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    • pp.38-43
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    • 2009
  • In this study, we investigated photocatalytic ability of plasma sprayed $TiO_2$ and Ag sputtering $TiO_2$(Ag-$TiO_2$) coatings. A sputtering processes were adopted to coat the surface of $TiO_2$ with Ag(99.99%). Ag was sputtered at 10mA, 450V for $1{\sim}11$ seconds. $TiO_2$ and Ag-$TiO_2$ coatings were heat-treated at 250, 300, 350, $400^{\circ}C$ for $0{\sim}240$seconds. Photoelectrical conductivity was measured by four-point probe, and photodegradation was calculated by UV-V is spectrometer. Microstructure observation of $TiO_2$ and Ag-$TiO_2$ coatings were investigated by SEM. Crystal structure of $TiO_2$ and Ag-$TiO_2$ coatings were investigated by XRD. Qualitative analyses of $TiO_2$ and Ag-$TiO_2$ coatings were conducted by EDX. When $TiO_2$ coatings were heat-treated at $350^{\circ}C$ for 30 sec, photoelectrical conductivity and photodegradation were best. And in XRD analysis result, (101)/(110) relative intensity ratio of $TiO_2$(rutile) was comparably changed with photoelectrical conductivity. When Ag-$TiO_2$ coatings were heat-treated at $350^{\circ}C$ for 30 [sec] after sputtering Ag for 7 sec, Photoelectrical conductivity and photodegradation are best. Surface of coatings in such condition has very small and uniform Ag particles.

Chemical Binding States of Ti and O Elements in Anodic Ti Oxide Films (Ti 양극산화 피막에서 Ti 및 O원소의 화학결합 상태)

  • 유창우;오한준;이종호;장재명;지충수
    • Journal of the Korean institute of surface engineering
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    • v.35 no.6
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    • pp.383-390
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    • 2002
  • To investigate behaviors of Ti and O elements and microstructures of anodic titanium oxide films, the films were prepared by anodizing pure titanium in $H_2$S $O_4$, $H_3$P $O_4$, and $H_2O$$_2$ mixed solution at 180V. The microstructures and chemical states of the elements were analyzed using SEM, X-ray mapping, AFM, XRD, XPS (depth profile). The films formed on a titanium substrate showed porous layers which were composed of pore and wall, And with increasing anodizing time a hexagonal shape of cell structures were dominant and solace roughness increased. From the XRD result the structure of the Ti $O_2$ layer was anatase type of crystal on the whole. In the XPS spectra it was found that Ti and O were chemically binded in forms of Ti $O_2$, TiOH, $Ti_2$ $O_3$ at Ti 2p, and Ti $O_2$, $Ti_2$ $O_3$, $P_2$ $O_{5}$, S $O_4^{2-}$ at O ls respectively. Concentration of Ti $O_2$ decreased as the depth increased from the surface of the oxide film towards the substrate, but to the contrary concentrations of TiOH and $Ti_2$ $O_3$ increased.d.

Preparation of $BaTiO_3$ powder in solid reaction and basic study on dielectrics of $CeAIO_3-BaTiO_3$system ($BaTiO_3$ 분말합성조건 및 $CeAIO_3-BaTiO_3$계 유전체의 기초적 연구)

  • Lim, Dae-Young;Kim, Jong-Ock;Lee, Chae-hyun;Park, Won-Kyu
    • The Journal of Natural Sciences
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    • v.8 no.1
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    • pp.61-69
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    • 1995
  • It is hard to synthesize pure $BaTiO_3$ from $BaCO_3$ and $TiO_2$ in solid reaction for the activity of BaO and secondary phase. For this reason, the wet chemical techniques have been studied. Starting material which was used in these methods were expensive and the properties of powder which was synthesized in same defined. So, some process have been studying again to improve soild reaction method. This study which was one of those was to defin the forming mechanism of $Ba_2TiO_4$ and to control some condition of $Ba_2TiO_4$. The synthesis temperature of $BaTiO_3$ in solid reaction was near $1120^{\circ}C$. The quantity and forming temperature of $Ba_2TiO_4$ could be controlled by atmosphere heat treatment. $Ba_2TiO_4$ was related to expansion in Ba-rich region of $BaTiO_3$. $BaTiO_2O_5$ and $BaTiO_3O_7$ was reason to expand in Ti-rich region. The dielectrics of $CeAIO_3$ which was synthesized and sintered in reduction atmosphere and $BaTiO_3$ system were affected by $CeO_2$ which was formed for the decomposition of $CeAIO_3$ heat treatment in air.

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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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A Study on the Preparation of Lead Dioxide Electrode with High Oxygen Overvoltage and Durability (높은 산소과전압과 내구성의 이산화납전극 제조에 관한 연구)

  • Kim, Jae Kwan;Choi, Byun Sun;Nam, Chong Woo
    • Applied Chemistry for Engineering
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    • v.7 no.6
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    • pp.1105-1114
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    • 1996
  • The characteristic and performance of ${\beta}-PbO_2$ layer electrodeposited on ${\alpha}-PbO_2/IrO_2-TiO_2/Ti$ substrate by adding sodium lauryl sulfate and $TiO_2$ powder in lead nitrate solution were investigated by using XRD, SEM, cyclic voltammograms, and macro-elctrolysis. Results of XRD analysis ascertain that ${\beta}-PbO_2$ layers electrodeposited in the presence of sodium lauryl sulfate and $TiO_2$, powder on ${\alpha}-PbO_2/IrO_2-TiO_2/Ti$ substrate have the same tetragonal structure as pure ${\beta}-PbO_2$ layers. The SEM results show that sodium lauryl sulfate tend to diminish crystal size of the deposited layer. The ${\beta}-PbO_2$ electrode electrodeposited in the presence of sodium lauryl sulfate and $TiO_2$ powder gives significantly improved oxygen overvoltage and durability for anodic oxidation in KOH and $HClO_4$ supporting electrolyte. Electrode performance and durability for the evolution of ozone in perchloric acid solution have been investigated by using ${\beta}-PbO_2$ electrodes electrodeposited on Titanium $madras^{(R)}$. It was ascertained that the $PbO_2$ electrode electrodeposited on ${\alpha}-PbO_2/IrO_2-TiO_2/Ti$ $madras^{(R)}$ by adding sodium lauryl sulfate and $TiO_2$ powder in $HClO_4$ supporting electrolyte had the highest current efficiency and durability.

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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.