• Title, Summary, Keyword: $TiO_2$

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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.

Preparation of hydroxyapatite/$TiO_2$ biocomposite powders by wet chemical method (습식화학법에 의한 수산화아파타이트/$TiO_2$ 생체용 복합분말의 제조)

  • 정항철;이종국
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.14 no.3
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    • pp.83-89
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    • 2004
  • In this work, HA/$TiO_2$ biocomposite to get high mechanical properties with biocompatibility were prepared. HA/$TiO_2$ biocomposite powders were prepared by mixing $TiO_2$ and HA powders which were synthesized through sol-gel, precipitation and hydrothermal methods. The mixing ratio was fixed at 1:1 ratio (HA/$TiO_2$, wt%). HA/$TiO_2$ biocomposite powders showed different microstructures depending on their particle size and shape. The smaller particles were coated on the surface of larger particles, whereas they were well mixed and dispersed when both $TiO_2$ and HA were nanocrystallites. HA/$TiO_2$ biocomposite powders with homogeneous microstructure showed high sintered density and good mechanical properties.

Highly Ordered TiO2 nanotubes on pattered Si substrate for sensor applications

  • Kim, Do-Hong;Shim, Young-Seok;Moon, Hi-Gyu;Yoon, Seok-Jin;Ju, Byeong-Kwon;Jang, Ho-Won
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.66-66
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    • 2011
  • Anodic titanium dioxide (TiO2) nanotubes are very attractive materials for gas sensors due to its large surface to volume ratios. The most widely known method for fabrication of TiO2 nanotubes is anodic oxidation of metallic Ti foil. Since the remaining Ti substrate is a metallic conductor, TiO2 nanotube arrays on Ti are not appropriate for gas sensor applications. Detachment of the TiO2 nanotube arrays from the Ti Substrate or the formation of electrodes onto the TiO2 nanotube arrays have been used to demonstrate gas sensors based on TiO2 nanotubes. But the sensitivity was much lower than those of TiO2 gas sensors based on conventional TiO2 nanoparticle films. In this study, Ti thin films were deposited onto a SiO2/Si substrate by electron beam evaporation. Samples were anodized in ethylene glycol solution and ammonium fluoride (NH4F) with 0.1wt%, 0.2wt%, 0.3wt% and potentials ranging from 30 to 60V respectively. After anodization, the samples were annealed at $600^{\circ}C$ in air for 1 hours, leading to porous TiO2 films with TiO2 nanotubes. With changing temperature and CO concentration, gas sensor performance of the TiO2 nanotube gas sensors were measured, demonstrating the potential advantages of the porous TiO2 films for gas sensor applications. The details on the fabrication and gas sensing performance of TiO2 nanotube sensors will be presented.

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The Complexing Effect of $BaTiO_3\;for\;Bi_4Ti_3O_{12}$ on Layered Perovskite $Bi_4Ti_3O_{12}{\cdot}nBaTiO_3(n=1&2)$ Thin Films ($Bi_4Ti_3O_{12}{\cdot}nBaTiO_3(n=1&2)$ 박막에서 $Bi_4Ti_3O_{12}$ 에 대한 $BaTiO_3$의 복합효과)

  • 신정묵;고태경
    • Journal of the Korean Ceramic Society
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    • v.35 no.11
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    • pp.1130-1140
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    • 1998
  • Thin films of $Bi_4Ti_3O_{12}\;nBaTiO_3(n=1&2)$ were prepared using sols erived Ba-Bi-Ti complex alkoxides. The sols were spin-cast onto $Pt/Ti/SiO_2/Si$ substrates and followed by pyrolysis for 1 hr at $620^{\circ}C,\;700^{\circ}C\;and\;750^{\circ}C$ In the thin films a pyrochlore phase seemed to be formed at a lower temperature and then tran-formed to the layered perovskite phase as the heating temperature increased. In the thin films pyrolyzed at formed to the layered perovskte phase as the heating temperature increased. In the films pyrolyzed at $750^{\circ}C$ the amount of $Bi_4Ti_3O_{12}{\cdot}BaTiO_3$ reached to 94% while $Bi_4Ti_3O_{12}{\cdot}BaTiO_3$ was 77% in composition. This result shows that the formation of the layered pervoskite phase becomes difficult as the amount of complexing $BaTiO_3$ increases. The microstructures and the electrical properties of the thin films were gen-erally improved with the incease of the heating temperature. However the presence of the pyrochlore phase could not be removed effectively. Our study showed that the electrical properties of $Bi_4Ti_3O_{12}{\cdot}BaTiO_3$ were pronouncedly improved with complexing with BaTiO3 when compared to those of $Bi_4Ti_3O_{12}$ while the presence of the pyrochlore phase was detrimental to the those of $Bi_4Ti_3O_{12}{\cdot}2BaTiO_3$.

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Microwave Dielectric Properties of $0.95MgTiO_3-0.05SrTiO_3$ Ceramics with $V_2O_5$ ($V_2O_5$ 첨가에 따른 $0.95MgTiO_3-0.05SrTiO_3$ 세라믹스의 마이크로파 유전특성)

  • Nam, Gyu-Bin;Kim, Kang;Park, In-Gil;Ryu, Ki-Won;Lee, Young-Hie
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.112-116
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    • 2002
  • The $0.95MgTiO_3-0.05SrTiO_3$ ceramics with $V_2O_5$(10wt%) were prepared by the conventional mixed oxide method. The structural properties were investigated with sintering temperatue by XRD. According to the X-ray diffraction pattern of the $0.95MgTiO_3-0.05SrTiO_3$ ceramics with $V_2O_5$(10wt%), the ilmenite $MgTiO_3$ and perovskite $SrTiO_3$ structures were coexisted and secondary phase $MgTi_2O_5$ were appeared. In the case of $0.95MgTiO_3-0.05SrTiO_3$ ceramics with $V_2O_5$(10wt%), dielectric constant, quality factor and temperature coefficient of resonant frequency were 15.84~18.28, 12627~23138GHz, -21.414~1.568$ppm/^{\circ}C$, respectively.

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Effects of Oxygen on Preparation of TiO2 Thin Films by MOCVD (MOCVD법에 의한 TiO2 박막의 제조에 미치는 산소의 영향)

  • Yu, Seong-Uk;Park, Byeong-Ok;Jo, Sang-Hui
    • Korean Journal of Crystallography
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    • v.6 no.2
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    • pp.111-117
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    • 1995
  • TiO2 thin films were prepared on a (100)silicon wafer using a chemical vapor deposition(CVD) method. The deposition experiments were performed using the TTIP in the deposition temperature ransing from 200 content. The deposition rate of TiO2 was increased with the substrate temperature and the oxygen content. The thickness of the deposited thin film and the compositional analysis of this thin films with theoxygen content were measured using Ellipsometry, SEM and ESCA, respectively. The deposited thin film was composed of a bilayer, external TiO2 and internal Ti. Carbon as a residual impurity was found to remain when zero sccm O2 was purged into a reaction chamber and the composition of the deposited thin film was found to change Ti into TiO in a deeper layer. However, when 600sccm O2 was supplied to a reaction chamber, it has been found to reside less carbon content than without O2. Finally, in the condition of 1200sccm O2, no impurity level of carbon was observed and a deeper layer consisted of the Ti composite, even though the deposited surface was composed of TiO2.

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Photo-degradation of Phenol and Toluene by Using the TiO2-coated Polyethylene Particles (TiO2가 코팅된 Polyethylene 입자를 이용한 페놀과 톨루엔의 광분해)

  • Kim, Dong-Joo;Choi, Sang-Keun;Cho, Jun-Hyung;Kim, Kyo-Seon
    • Journal of Industrial Technology
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    • v.24 no.B
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    • pp.133-138
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    • 2004
  • The photodegradation of phenol and toluene with the $TiO_2$-coated polyethylene (PE) particles were investigated in the slurry type photocatalytic reactor, changing the $TiO_2$ particle sizes, initial phenol and toluene concentrations, and the oxygen flow rate. The nano-sized $TiO_2$ photocatalyst particles were prepared by the diffusion flame reactor and they were coated onto PE particles by using the hybridization system for the efficient recollection of $TiO_2$-coated particles after photodegradation experiments. The degradation efficiencies of phenol and toluene with the $TiO_2$-coated PE particles were more than 90% after photodegradation of 80 minutes for most cases. The efficiencies of photodegradation with the $TiO_2$-coated PE particles were found to be lower than those by the pure $TiO_2$ particles by 50%, because of the decrease in specific surface area of $TiO_2$ particles in PE particles.

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Doped TiO2와 coupled TiO2 제조 및 다양한 광원하의 유기물 분해 특성 평가

  • Lee, Gyu-Sang;Mun, Ji-Yeon;Kim, Seon-Min
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.227.1-227.1
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    • 2015
  • 산업이 발달하면서 다양한 화학물질이 배출되고 이로 인하여 환경이 오염되고 있으며, 특히, 대부분의 유기 화합물은 대기오염에 많은 영향을 주는 물질로 알려져 있다. 최근 유기 화합물을 제거하기 위해서 UV와 가시광에서 반응하는 광촉매 연구가 진행되고 있다. 본 연구에서는 밴드갭에 변화를 주는 doped $TiO_2$와 가시광에서 반응하는 조촉매를 이용하여 광촉매의 특성을 향상시키는 coupled $TiO_2$를 제조하였다. Doped $TiO_2$를 제조하기 위해서 비금속 물질인 질소(nitrogen)을 사용하였고, coupled $TiO_2$는 graphine oxide(GO)를 환원하여 $TiO_2$-RGO 촉매를 제조하였다. N-$TiO_2$$TiO_2$-RGO의 광학 특성을 평가하기 위해서 UV/Vis 분광광도계를 사용하였다. Methylene blue(MB)와 methyl orange(MO)가 분해되는 반응을 통해서 N-$TiO_2$$TiO_2$-RGO의 광촉매 특성을 평가하였다. 또한, MB와 MO 분해 테스트에 395 nm long pass filter를 이용하여 가시광에서의 광촉매 활성을 평가하였다.

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Fabrication of dye-sensitized solar cells using a both-ends-opened TiO2 nanotube/nanoparticle hetero-nanostructure

  • Hossain, Md Ashraf;Oh, Sehyun;Lim, Sangwoo
    • Journal of Industrial and Engineering Chemistry
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    • v.51
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    • pp.122-128
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    • 2017
  • We fabricated a hetero-structure photoanode with both-ends-opened $TiO_2$ nanotubes and $TiO_2$ nanoparticles for dye-sensitized solar cells (DSSCs). Two-step anodization and selective etching process were used to obtain the both-ends-opened $TiO_2$ nanotubes. A heat treatment was employed to obtain anatase crystal-structured nanotubes. The effect of the both-ends-opened $TiO_2$ nanotubes on the photoelectric conversion efficiency (PCE) of the DSSCs was evaluated by positioning the $TiO_2$ nanotubes on $TiO_2$ nanoparticle layers and by sandwiching them between the $TiO_2$ nanoparticles. It is suggested that both-ends-opened $TiO_2$ nanotubes serve as incident light scattering layers that lead to superior light harvesting efficiency of DSSCs. This increases the electron lifetime and results in the recycling of more light by dye molecules, thus increasing the photocurrent density. Consequently, a high PCE of 7.74% was obtained when the $TiO_2$ nanotubes were placed on the $TiO_2$ nanoparticles and a PCE of 8.56% was obtained when the $TiO_2$ nanotubes were placed between the $TiO_2$ nanoparticles.

Fabrication and Photocatalytic Properties of SiO2-TiO2 Composite Nanofibers (SiO2-TiO2계 복합 나노섬유의 제조 및 광활성 연구)

  • Hyun, Dong Ho;Lim, Tae-Ho;Lee, Sung Wook
    • Applied Chemistry for Engineering
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    • v.19 no.5
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    • pp.554-558
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    • 2008
  • $(1-x)SiO_2-(x)TiO_2$ composite fibers with various compositions of $TiO_2$ were prepared by electrospinning their sol-gel precursors of titanium (IV) iso-propoxide (TiP), and tetraethyl orthosilicate (TEOS). The surface morphology and structure of sintered composite fibers were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), simultaneous thermogravimetric analysis-differential scanning calorimetry (TGA-DSC) and Fourier transform infrared spectroscopy (FT-IR). As the content of $TiO_2$ in $(1-x)SiO_2-(x)TiO_2$ system was increased the average diameter of composite fibers was proportionally increased. Also, the transformation of $TiO_2$ from anatase to rutile form was inhibited by the highly dispersed $TiO_2$ around $SiO_2$ particles up to $0.6SiO_2-0.4TiO_2$ composite fibers even after calcination at $1000^{\circ}C$. The photocatalytic activity of $SiO_2-TiO_2$ composite fibers was examined for the methylene blue (MB) decomposition which was confirmed using UV-vis/DRS spectra. The experiments demonstrated that the MB in aqueous solution was successfully photodegraded using $SiO_2-TiO_2$ composite nanofibers under UV-visible light irradiation.