• Title, Summary, Keyword: $TiO_2$

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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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Fabrication of Photocatalytic TiO2 thin Film Using Aerosol Deposition Method and its Filtration Characteristics (에어로졸 증착법을 이용한 광촉매 TiO2 박막 제조 및 박막의 여과 특성)

  • Choi, Wonyoul;Lee, Jinwoo;Kim, Shijun;Kim, Jongoh
    • Journal of the Korean GEO-environmental Society
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    • v.11 no.1
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    • pp.5-11
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    • 2010
  • The objective of this study is to evaluate the effect of operational parameters such as rotation speed and vibrating milling time for the fabrication of photocatalytic $TiO_2$ thin film using aerosol deposition methods. $TiO_2$ powders produced in the range of 1,000-3,000 rpm of rotation speed of centrifugal separator are ineffective on the fabrication of $TiO_2$ thin film by aerosol deposition due to the problem of nozzle powder jam. $TiO_2$ powders controlled by vibrating milling had about 420 nm of average diameter after 2 hr of vibrating milling time. The result of XRD analysis indicated that $TiO_2$ powders had a anatase phase. Vibrating milling methods was considered to be an effective pre-treatment process for $TiO_2$ powder control. Consequently $TiO_2$ photocatalytic thin film with dispersion of anatase crystallites controled by vibrating milling was successfully fabricated by aerosol deposition. The permeation flux of $TiO_2$ photocatalytic thin film with the immobilized $TiO_2$ powder was higher than that of suspended $TiO_2$ powder. Therefore, $TiO_2$ photocatalytic thin film promises to be one of the effective methods for enhancing filtration performance for the treatment of organic pollutants.

The effects of TiO2 interlayer phase transition on structural and electrical properties of PLZT Thin Films (TiO2 Interlayer의 상변화에 따른 PLZT 박막의 구조 및 전기적 특성)

  • Lee, Chul-Su;Yoon, Ji-Eon;Hwang, Dong-Hyun;Cha, Won-Hyo;Sona, Young-Gook
    • Journal of the Korean Vacuum Society
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    • v.16 no.6
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    • pp.446-452
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    • 2007
  • [ $(Pb_{1.1},La_{0.08})(Zr_{0.65}.Ti_{0.35})O_3$ ] thin films on the $Pt/Ti/SiO_2/Si$, $TiO_2(interlayer)/Pt/Ti/SiO_2/Si$ substrate were fabricated by the R.F. magnetron-sputtering method and considered their characteristics depending on $TiO_2$ interlayer. Changing the deposition conditions of $TiO_2$ interlayer, we obtained $TiO_2$ anatase single phase and rutile single phase. PLZT was deposited on these substrates and analyzed by x-ray diffraction(XRD) for there crystallinity and orientation. To investigate $PLZT-TiO_2$, $TiO_2-Pt$ interface, glow discharge spectrometer(GDS) analysis was carried out and we performed electrical measurements for dielectric properties of PLZT thin films. The PLZT thin film on $TiO_2$ anatase interlayer was found to have (110)-preferred orientation and 12.6 ${\mu}C/cm^2$ remaining polarization value.

Evaluation of Microwave Dielectric Properties of MgO-TiO2 System by Dielectric Mixing Rules

  • Kim, Eung-Soo;Seo, Seock-No
    • Journal of the Korean Ceramic Society
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    • v.47 no.2
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    • pp.163-168
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    • 2010
  • Effects of compositions on the microwave dielectric properties of the MgO-$TiO_2$ system were investigated as a function of the molar ratio of MgO to $TiO_2$ ($0.9{\leq}MgO/TiO_2\;(x){\leq}1.2$). With the compositional changes, secondary phases of $MgTi_2O_5$ and $Mg_2TiO_4$ were also detected along with $MgTiO_3$. Microwave dielectric properties of the specimens were dependent on the types of phases developed in the sintered specimens. A single phase of $MgTiO_3$ showed a dielectric constant (K) of 18.2, a quality factor (Qf) of 198,000 GHz, and a temperature coefficient of resonant frequency (TCF) of $-51\;ppm/^{\circ}C$. However, the dielectric properties of the specimens with a secondary phase of $MgTi_2O_5$ (K=19.9, Qf=48,000 GHz) and/or $Mg_2TiO_4$ (K=15.6, Qf=56,000 GHz) were worsened. Dependence of the microwave dielectric properties on the secondary phase of the MgO-$TiO_2$ system was also discussed in terms of dielectric mixing rules.

An Electrochemical Reduction of TiO2 Pellet in Molten Calcium Chloride (CaCl2 용융염에서 TiO2 펠렛의 전기화학적 환원반응 특성)

  • Ji, Hyun-Sub;Ryu, Hyo-Yeol;Jeong, Ha-Myung;Jeong, Kwang-Ho;Jeong, Sang-Mun
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.10 no.2
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    • pp.97-104
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    • 2012
  • A porous $TiO_2$ pellet was electrochemically converted to the metallic titanium by using a $CaCl_2$ molten salt system at $850^{\circ}C$. Ni-$TiO_2$ and graphite electrodes were used as cathode and anode, respectively. The electrochemical behaviour of $TiO_2$ pellet was determined by a constant voltage control electrolysis. Various reaction intermediates such as $CaTiO_3$, $Ti_2O$ and $Ti_6O$ were observed by XRD analysis during electrolysis of the pellet. Once $TiO_2$ pellet was converted to a porous metallic structure, the porous structure disappeared by sintering and shrinking with increasing the reaction time at high temperature.

Enhanced Photoelectrochemical Reaction of MoS2 Nanosheets Vertically Grown on TiO2 Nanowires (MoS2 나노시트의 TiO2 나노선에 수직 성장을 통한 광전기화학반응 향상)

  • Seo, Dong-Bum;Kim, Eui-Tae
    • Korean Journal of Materials Research
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    • v.31 no.2
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    • pp.92-96
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    • 2021
  • We report the growth and enhanced photoelectrochemcial (PEC) water-splitting reactivity of few-layer MoS2 nanosheets on TiO2 nanowires. TiO2 nanowires with lengths of ~1.5 ~ 2.0 ㎛ and widths of ~50~300 nm are synthesized on fluorine-doped tin oxide substrates at 180 ℃ using hydrothermal methods with Ti(C4H9O)4. Few-layer MoS2 nanosheets with heights of ~250 ~ 300 nm are vertically grown on TiO2 nanowires at a moderate growth temperature of 300 ℃ using metalorganic chemical vapor deposition. The MoS2 nanosheets on TiO2 nanowires exhibit typical Raman and ultraviolet-visible light absorption spectra corresponding to few-layer thick MoS2. The PEC performance of the MoS2 nanosheet/TiO2 nanowire heterostructure is superior to that of bare TiO2 nanowires. MoS2/TiO2 heterostructure shows three times higher photocurrent than that of bare TiO2 nanowires at 0.6 V. The enhanced PEC photocurrent is attributed to improved light absorption of MoS2 nanosheets and efficient charge separation through the heterojunction. The photoelectrode of the MoS2/TiO2 heterostructure is stably sustained during on-off switching PEC cycle.

Modification of Graphite Surface By the Hydrothermal Coating of $TiO_2$ ($TiO_2$ 수열코팅에 의한 흑연의 표면 개질)

  • 최승도;박병규
    • Korean Journal of Crystallography
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    • v.8 no.2
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    • pp.154-159
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    • 1997
  • Hydorthemal coating technique has been sucessfully applied to improve oxidation resistance of graphite by forming rutile-TiO2 layer. Hydrothermal treatment of graphite in 0.2M TiCl4 aquous solution at 35℃ resulted in improved water wettability due to the formation of surface-modifying TiO2. The amount of TiO2 increased with temperature. In the presence of surface TiO2 layer, weight loss was reduced by 30%, while the initiation temperature of oxidation was lowered by 30℃.

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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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The microwave dielectric characteristics of $(Li_{1/2}Nd_{1/2})TiO_3$ ceramics by the addition of $TiO_2$ (과잉 $TiO_2$ 첨가에 의한 $(Li_{1/2}Nd_{1/2})TiO_3$ 세라믹스의 고주파 유전특성)

  • 박종목;이응상
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.7 no.2
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    • pp.301-308
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    • 1997
  • The LNT ceramics which has the large negative temperature coefficient of resonant frequency ($\tau_1$) were manufactured by varying the $TiO_2$ contents. The effects of secondary phase $TiO_2$ which was caused by excess $TiO_2$ on the microstructure, phase transformations and microwave dielectric properties in ($Li_{1/2}Nd_{1/2}$)$TiO_3$ binary system were studied by X-ray and SEM. In case of adding up to 5 mol% $TiO_2$ on LNT, the liquid phase $TiO_2$which was created in the grain boundary of LNT not only increased the bulk density but also caused the nonhomogeneous structure of LNT which reduced the microwave dielectric characteristics. But the temperature coefficient of resonant frequency was improved by the 10 mol% addition of $TiO_2$.

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Preparation and photocatalytic effect of MWCNT/TiO2 composites (MWCNT/TiO2 복합체의 제조 및 광촉매 특성)

  • Chen, Ming-Liang;Oh, Won-Chun
    • Analytical Science and Technology
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    • v.21 no.3
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    • pp.229-236
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    • 2008
  • $C/TiO_2$ composites were prepared with surface modified MWCNT sequentially after HCl treatment and TNB as titanium source. There is a single crystal structure which is anatase in all of the samples from the data of XRD. The SEM microphotographs of $C/TiO_2$ composites show that the $TiO_2$ particles were well mixed with the CNT. There are C, O and Al with strong Ti peaks in all samples from EDX results, and it also shows that the sample CT has much more amount of C and Ti content than that of sample HCT. Finally, the photocatalytic activities for the $C/TiO_2$ composites have more effective than that of pristine $TiO_2$.