• Title/Summary/Keyword: Anatase and rutile phase

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Phase stability of TiO2 synthesized by Sol-gel Method at various pH and calcination temperatures (졸-겔 방법으로 합성된 TiO2 상안정성에 대한 pH 및 열처리 온도의 영향)

  • Lee, Jae-Yeon;Kim, Yong-Jin;Kim, Dae-Sung;Shin, Hyo-Soon;Nahm, Sahn;Chun, Myoung-Pyo
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.31 no.4
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    • pp.166-173
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    • 2021
  • The rutile phase of TiO2 forms a stable phase at high temperatures compared to anatase phase, but the stable temperature range of anatase changes depending on the synthesis conditions. In this study, nano-sized TiO2 was synthesized by the Sol-gel method using TiOSO4 and a mixed solvent of ethanol and distilled water, and the phase change of anatase and rutile according to pH and heat treatment temperature was investigated. Changes in the ratio of anatase and rutile were observed by changing the pH (3, 5, 7, 9) and heat treatment temperature (500, 600, 700, 800, 900℃) conditions of the prepared TiO2. As a result of observing these changes through XRD and FE-SEM analysis, anatase TiO2 at 500℃ and rutile TiO2 at 900℃ were observed. According to the pH, at these intermediate temperatures of 600, 700 and 800℃, the ratio of anatase and rutile changes. At 700℃, it was concluded that pH = 3~5 had a larger ratio of anatase TiO2, and pH = 7~9 had a larger ratio of rutile TiO2.

HRTEM Study of Phase Transformation from Anatase to Rutile in Nanocrystalline $TiO_2$ Particles

  • Kim, Kyou-Hyun;Park, Hoon;Ahn, Jae-Pyoung;Lee, Jae-Chul;Park, Jong-Ku
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09a
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    • pp.466-467
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    • 2006
  • The anatase particle was facetted at the free surface and a neck formation between the anatase particles prior to the phase transformation occured. This resulted in the severe lattice distortion at the region of the interface near the neck and this can act as the nucleation sites for the phase transformation. The grain growth of rutile particles after the phase transformation grew very fast by the sweeping phenomena of grain boundary. Therfore, It leaded to the microstructure without the rutile phase located in anatase particle.

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Characterisation of $TiO_2$ film synthesized using titaniumtetrachlo precusor ($TiCl_3$를 이용해서 합성된 $TiO_2$ 박막의 특성)

  • 김강혁;이창근;이규환;김인수
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2003.11a
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    • pp.111-111
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    • 2003
  • The peroxo titanic acid solution was successfully prepared using titanium trichloride as a precursor. The basic properties of the TiO2 film prepared by the solution were investigated in view of phase change, bandgap energy, crystalline size etc. The film displayed amorphous TiO$_2$ at room temperature, anatase above 281$^{\circ}C$ and a mixture of anatase and rutile at 99$0^{\circ}C$, The crystalline size increases with annealing temperatures, while the bandgap energies decrease due to the quantum size effect and the formation of rutile phase which has low bandgap energy. As a result of TG-DTA, it was found that annealing treatment at 99$0^{\circ}C$ for 2h formed a mixtures of anatase and rutile through three steps: (1) the removal of physically adsorbed water (2) the decomposition of peroxo group (3) amorphous-anatase or anatase-rutile phase transformation.

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Crystal Structure and Superhydrophilic Property of $TiO_2$ Thin Film Coated on Si(100) Wafer (Si(100) 기판 위에 코팅된 $TiO_2$박막의 결정구조와 초친수 특성)

  • 김사라;조운조;박재관;이용철
    • Korean Journal of Crystallography
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    • v.12 no.3
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    • pp.177-181
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    • 2001
  • We have studied superhydrophilic properties of TiO₂thin films in relation with those crystal structures due to the heat treatments. Thin films were fabricated on Si (100) wafers using a conventional Sol-Gel method. Following drying and sintering processes, TiO₂film had an anatase phase with additional heat treatment at 500℃, an rutile phase at 1000℃, and a mixture of anatase and rutile phase at 750℃. All these films got hydrophilic even without any UV illumination. Especially the sample treated at 750℃ had a superhydrophilic contact angle of 5°. We suggested that the superhydrophilic films should have a mixture of anatase and rutile phase for the best performance. The hydrophilic TiO₂films were slowly degraded into the hydrophobic state in the dark room but quickly recovered back with les than 1 hour of UV illumination.

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Structural Properties of TiO₂ Films Grown by Pulsed Laser Deposition

  • 윤하섭;김성규;임훙선
    • Bulletin of the Korean Chemical Society
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    • v.18 no.6
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    • pp.640-643
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    • 1997
  • Pure titanium dioxide $(TiO_2)$ films were prepared by pulsed laser deposition on a single crystal Si(100) substrate. We have investigated the growth of crystalline titanium dioxide films with respect to substrate temperature and ambient oxygen pressure. The structural properties of the films were analyzed by X-ray diffraction. We found that the anatase as well as the rutile phases could be formed from the original rutile phase of the target $TiO_2$. At 0.75 torr of ambient oxygen pressure, the structure of $TiO_2$ film was amorphous at room temperature, anatase between 300 and 600 ℃, a mixture of anatase and rutile between 700 and 800 ℃, and only rutile at 900 ℃ and above. However, at a low ambient oxygen pressure, the rutile phase became dominant; the only rutile phase was obtained at the ambient oxygen pressure of 0.01 torr and the substrate temperature of 800 ℃. Therefore, the film structures were largely influenced by substrate temperature and ambient oxygen pressure.

Effect on TENG Performance by Phase Control of TiOx Nanoparticles

  • Huynh, Nghia Dinh;Park, Hyun-Woo;Chung, Kwun-Bum;Choi, Dukhyun
    • Composites Research
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    • v.31 no.6
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    • pp.365-370
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    • 2018
  • One of the critical parameters to improve the output power for triboelectric nanogenerators (TENGs) is the surface charge density. In this work, we modify the tribo-material of TENG by introducing the $TiO_x$ embedded Polydimethylsiloxane (PDMS) in anatase and rutile phase. The effect of dielectric constant and electronic structure of the $TiO_x$ on the capacitance of TENG and the output power as well are discussed. The surface charge density is increased as the control of the dielectric constant in difference weight percent of $TiO_x$ and PDMS. As the results of that, the 5% $TiO_x$ rutile phase and 7% $TiO_x$ anatase phase embedded PDMS exhibit the highest TENG output. The peak value of voltage/current obtained from $TiO_x$ rutile and anatase phase are ${\sim}180V/8.2{\mu}A$ and $211.6V/8.7{\mu}A$, respectively, at the external force of 5 N and working frequency of 5 Hz, which gives over 12-fold and 15-fold power enhancement compared with the TENG based on the pristine PDMS film. This study provides a better understanding for TENG performance enhancement from the materials view.

Physicochemical properties of different phases of titanium dioxide nanoparticles

  • Dong, Vu Phuong;Yoo, Hoon
    • International Journal of Oral Biology
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    • v.46 no.3
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    • pp.105-110
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    • 2021
  • The physicochemical properties of crystalline titanium dioxide nanoparticles (TiO2 NPs) were investigated by comparing amorphous (amTiO2), anatase (aTiO2), metaphase of anatase-rutile (arTiO2), and rutile (rTiO2) NPs, which were prepared at various calcination temperatures (100℃, 400℃, 600℃, and 900℃). X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses confirmed that the phase-transformed TiO2 had the characteristic features of crystallinity and average size. The surface chemical properties of the crystalline phases were different in the spectral analysis. As anatase transformed to the rutile phase, the band of the hydroxyl group at 3,600-3,100 cm-1 decreased gradually, as assessed using Fourier transform infrared spectroscopy (FT-IR). For ultraviolet-visible (UV-Vis) spectra, the maximum absorbance of anatase TiO2 NPs at 309 nm was blue-shifted to 290 nm at the rutile phase with reduced absorbance. Under the electric field of capillary electrophoresis (CE), TiO2 NPs in anatase migrated and detected as a broaden peak, whereas the rutile NPs did not. In addition, anatase showed the highest photocatalytic activity in an UV-irradiated dye degradation assay in the following order: aTiO2 > arTiO2 > rTiO2. Overall, the phases of TiO2 NPs showed characteristic physicochemical properties regarding size, surface chemical properties, UV absorbance, CE migration, and photocatalytic activity.

Characterization of Thermal Spray Coating Layers of Nano Crystalline TiO2 for Photocatalyst (광촉매용 나노 TiO2 용사코팅층 특성)

  • Lee, Soo W.;Kim, Hak-Soo;Zeng, Yi;Hockey, Bernad
    • Korean Journal of Materials Research
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    • v.12 no.10
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    • pp.809-813
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    • 2002
  • Commercial nano crystalline $TiO_2$ powders were used to characterize photocatalyst, using thermal spray coating technique. The microstructure of coating layers were examined by SEM, FE-SEM and TEM. Also the cross sectional areas of TiO$_2$ coating layers were observed by SEM. The phases were analyzed by X-ray diffraction methed. Surface roughness and hardness were measured. It was found that phase transformation from anatase to rutile occurred, and the melted splats are all rutile, and unmeted nano particles were anatase. These unmelted anatase phase may enhance te play a role of photocatalyst.

Estimation of Phase Ratio for TiO2 Powders by XRD and XAS (XRD와 XAS에 의한 TiO2 분말의 상분율 결정)

  • Rha, Sa-Kyun;Lee, Youn Seoung
    • Journal of the Korean Ceramic Society
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    • v.49 no.5
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    • pp.469-474
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    • 2012
  • The crystallinity and phase ratio of anatase to rutile in $TiO_2$ were estimated by x-ray diffraction (XRD) and x-ray absorption spectroscopy (XAS). Traditionally, the structural characterization of $TiO_2$ powders has been carried out by XRD techniques, which are comparatively easy in use and analysis. However, materials with amorphous phase, nano-sized or nano-structured crystallinities cannot be fully characterized by XRD because XRD analysis has a limit for abnormal contributions of the nano-crystal such as the surface contribution. From the comparison with the experimental and calculated Ti K-edge XAS spectra, we found the possibility of efficient estimation in the crystalinites and the phase ratio of anatase to rutile for nano-sized $TiO_2$ mixture.

Phase Transitions In Nonstoichiometric Titanium Oxide Thin Films (비정량적 산화티타늄 박막의 상변태 특성)

  • Hong, Seong-Min;Lee, Pil-Hong;Go, Gyeong-Hyeon;An, Jae-Hwan;Lee, Sun-Il
    • Korean Journal of Materials Research
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    • v.8 no.3
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    • pp.224-228
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    • 1998
  • Phase transition kinetics of nonstoichiometric amorphous titanium oxide thin films deposited by reactive sputtering was investigated after cooling down with various rate followed by l0min.-3hrs. annealing at $500^{\circ}C$~$600^{\circ}C$ After short duration and fast cooling. Magneli was the only crystalline phase because the oxidation rates of $TiO_{2-x}$, could be relatively slower than that of crystallization. When the films were cooled slowly between $500^{\circ}C$~$300{\circ}C$, Magneli was transformed into an anatase and stabilized, but directly into a rutile under fast cooling. Because the rutile also prevailed after cooling from $600^{\circ}C$, it was concluded that the rutile phase could be formed directly from Magneli as well as converted from the anatase. Changes in volume and surface morphology were observed related to crystallization and oxidation processduring heat treatment.

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