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1.
Synthesis of highly-active single-crystalline TiO2 nanorods and its application in environmental photocatalysis 总被引:1,自引:0,他引:1
Hoda S. Hafez 《Materials Letters》2009,63(17):1471-1474
Highly-active anatase TiO2 nanorods have been successfully synthesized via a simple two-step method, hydrothermal treatment of anatase/rutile titanium dioxide nanoparticle powder in a composite-hydroxide eutectic system of 1:1 M KOH/NaOH, followed by acid post-treatment. The morphology and crystalline structure of the obtained nanorods were characterized using XRD, TEM, SEM/EDX and BET surface area analyzer. The obtained TiO2 nanorods have a good crystallinity and a size distribution (about 4-16 nm); with the dimensions of 200-300 nm length and of 30-50 nm diameter. Compared with its precursor anatase/rutile TiO2 nanoparticles and the titanate nanotubes, the pure anatase TiO2 nanorods have a large specific surface area with a mesoporous structure. The photocatalytic performance of the prepared nanorods was tested in the degradation of the commercial Cibacrown Red (FN-R) textile dye, under UV irradiation. Single-crystalline anatase TiO2 nanorods are more efficient for the dye removal. 相似文献
2.
Zhenyao Wang Dingguo Xia Ge Chen Tao Yang Yu Chen 《Materials Chemistry and Physics》2008,111(2-3):313-316
Titania of different crystalline structures and morphology was prepared by the low temperature dissolution–reprecipitation process (LTDRP) of amorphous precursors in various acidic mediums at 70 °C for 8 h. The effects of different acids on the crystalline and morphology of titania nanostructures were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Results showed that HCl, HNO3 and their mixture favored the formation of rod-like rutile TiO2, while H2SO4 and its mixture with HCl or HNO3 retarded the formation of rutile but favored the formation of the anatase phase of with an irregular shape. The mechanism of the formation of various titania nanostructures was also discussed. 相似文献
3.
The optical and photocatalytic properties of TiO2 are closely related to crystalline structures, such as rutile and anatase. In this paper, TiO2 films were produced by inductively coupled plasma (ICP) assisted chemical vapor deposition (CVD) without extra heating of the substrate, and the effect of H2 addition on the structure and optical properties of the films was investigated. After increasing the partial pressure of H2, the structure of the TiO2 films changed from anatase to rutile, which usually appears at high temperatures (> 600 °C). The light transmittance decreased with increasing the H2 flow rate due to the increased surface roughness. The photocatalytic activity of the anatase TiO2 film was better than that of the rutile TiO2 film. 相似文献
4.
The influence of the concentration of aqueous TiCl4 solution on the phase formation, morphology and particle size of the titanium dioxide hydrolysis product was investigated by XRD and TEM. Significant features, observed in the Raman spectra of the TiCl4 solutions with a concentration >3 M, demonstrated that the TiCl4 had hydrolysed. As the formal concentration of TiCl4 decreased from 4.98 to 1 M, the Raman spectra changed qualitatively. Despite the changes in the Raman spectra of these precursor solutions, the TiO2 product was mainly rutile in all cases. However, at low TiCl4 concentrations small amounts of anatase were also observed. Electron microscopy suggested that the anatase particles were significantly smaller than the rutile and also indicated increasing aggregation of the product from the more dilute TiCl4 solutions. The optical properties and photoactivities of the TiO2 powders prepared at different concentrations were also investigated. The powder synthesized from 5 M TiCl4 showed the highest UV extinction. The photoactivity of the product, determined by the photocatalytic oxidation of propan-2-ol (isopropanol) to propanone (acetone), was not significantly modified by changes in the concentration of the starting TiCl4. The possibility that the relatively low area of most rutiles contributes to the reported photocatalytic activity of rutile being lower than that of anatase is discussed. 相似文献
5.
《Advanced Powder Technology》2019,30(12):3040-3049
The effect of dry-type surface modification of a fumed TiO2 and the thermal treatment were studied to synthesize the new fumed TiO2 having a high content of rutile structure and high dispersibility. The fumed TiO2 was modified with various metallic alkoxides to prepare precursors and next the resulted precursors were thermally-treated by the novel natural dropping method with a very short heating time, less than 1 s. The focus of this investigation was on the metallic alkoxide species as a surface modification agent and morphologies of both the precursor and thermally-treated fumed TiO2. The morphologies and nanostructures of the obtained fumed TiO2 were characterized. The carbon content and agglomerate of the precursor influenced on the transformation ratio from anatase to rutile structure. It was confirmed that the dry-type surface modification with tetraethoxysilane (TEOS) and titanium tetra-isopropoxide (TTIP) at room temperature is very effective method to prepare precursors for the next thermal treatment. The thermally-treated fumed TiO2 modified with TTIP showed 100% rutile structure with pure TiO2 composition at 1400 °C. The thermally-treated fumed TiO2 modified with small quantities of TEOS exhibited both 100% rutile structure and excellent dispersibility. This high dispersibility caused from a sponge-like structural characteristic of the agglomerate and static electricity repellence by coated SiO2 layer. The thermally-treated fumed TiO2 modified with TEOS and TTIP showed the color tone shift can be attributed to rutile structure. It was revealed that the combination of dry-type surface modification and natural dropping thermal treatment is an attractive method to prepare the new fumed TiO2 with 100% rutile structure maintaining the high dispersiblity. 相似文献
6.
Photocatalytic degradation of dyes and organic contaminants in water using nanocrystalline anatase and rutile TiO2 总被引:1,自引:0,他引:1
Rajesh J. Tayade Praveen K. Surolia Ramchandra G. Kulkarni Raksh V. Jasra 《Science and Technology of Advanced Materials》2007,8(6):455-462
Nanocrystalline TiO2 was synthesized by controlled hydrolysis of titanium tetraisopropoxide. The anatase phase was converted to rutile phase by thermal treatment at 1023 K for 11 h. The catalysts were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), Fourier-transform infrared absorption spectrophotometry (FT-IR) and N2 adsorption (BET) at 77 K. This study compare the photocatalytic activity of the anatase and rutile phases of nanocrystalline TiO2 for the degradation of acetophenone, nitrobenzene, methylene blue and malachite green present in aqueous solutions. The initial rate of degradation was calculated to compare the photocatalytic activity of anatase and rutile nanocrystalline TiO2 for the degradation of different substances under ultraviolet light irradiation. The higher photocatalytic activity was obtained in anatase phase TiO2 for the degradation of all substances as compared with rutile phase. It is concluded that the higher photocatalytic activity in anatase TiO2 is due to parameters like band-gap, number of hydroxyl groups, surface area and porosity of the catalyst. 相似文献
7.
Dorian A. H. Hanaor Mohammed H. N. Assadi Sean Li Aibing Yu Charles C. Sorrell 《Computational Mechanics》2012,50(2):185-194
Ab initio density functional theory calculations of the relative stability of the anatase and rutile polymorphs of TiO2 were carried out using all-electron atomic orbitals methods with local density approximation. The rutile phase exhibited a moderate margin of stability of ~ 3 meV relative to the anatase phase in pristine material. From computational analysis of the formation energies of Si, Al, Fe and F dopants of various charge states across different Fermi level energies in anatase and in rutile, it was found that the cationic dopants are most stable in Ti substitutional lattice positions while formation energy is minimised for F? doping in interstitial positions. All dopants were found to considerably stabilise anatase relative to the rutile phase, suggesting the anatase to rutile phase transformation is inhibited in such systems with the dopants ranked F?>?Si?>?Fe?>?Al in order of anatase stabilisation strength. Al and Fe dopants were found to act as shallow acceptors with charge compensation achieved through the formation of mobile carriers rather than the formation of anion vacancies. 相似文献
8.
Ordered bi-phase TiO2 nanowire arrays were simply obtained by heat treating TiO2 nanotube arrays prepared by a two-step anodization method. The nanowire arrays are composed of anatase and rutile phases with uniform diameters around 50 nm. The photocatalysis activities of TiO2 nanowire arrays were characterized by quantifying the degradation of methyl orange solution. And the results indicated that the bi-phase nanowire arrays, especially obtained at 700 °C, showed much higher activity than that of P25 film or anatase TiO2 nanotube array. 相似文献
9.
Mi-Seo Park 《Materials Letters》2008,62(2):183-187
This study examined hydrogen production over Ag-TiO2 photocatalysts containing AgxO, a conducting component. X-ray photon spectroscopy (XPS) confirmed that the Ag and Ag2O components were dominant in the Ag-TiO2 photocatalysts treated at 500 and 800 °C, respectively. The Ti2p bands in Ag-TiO2 were shifted to lower binding energies, which were assigned to Ti3+, compared to pure TiO2, and the shift was greater in the rutile structure than in the anatase. The measured full widths at half maximum (FWHM) of the Ag3d and Ti2p peaks were larger in the anatase structure than in the rutile structure in both TiO2 and Ag-TiO2. The H2 production from methanol photodecomposition was greater over the rutile structure than over the anatase structure of TiO2. Moreover, the amount of hydrogen was enhanced over Ag-TiO2 compared to pure TiO2; the production reached 17,124 μmol after 24 h over rutile Ag-TiO2. After methanol photodecomposition, the amount of Ag component in the Ag-TiO2 photocatalysts increased, while the Ag2O component decreased. 相似文献
10.
High density TiO2 nanotube film with hexagonal shape and narrow size distribution was fabricated by templating ZnO nanorod array film and sol-gel process. Well-aligned ZnO nanorod array films obtained by aqueous solution method were used as template to synthesize ZnO/TiO2 core-shell structure through sol-gel process. Subsequently, TiO2 nanotube array films survived by removing the ZnO nanorod cores using wet-chemical etching. Polycrystalline anatase TiO2 nanotube films were ∼ 1.5 μm long and ∼ 100 nm in inter diameter with a wall thickness of ∼ 10 nm. 相似文献
11.
Jeng-Shin Ma Ming-Chang Wen Chung-Hsin Lu 《Journal of Materials Science: Materials in Electronics》2013,24(7):2506-2512
The kinetic mechanism of the phase transformation of TiO2 from the anatase phase to the rutile phase was investigated. TiO2 powders were prepared with different pH value of the starting solution via the thermal hydrolysis method in this study. The pH values of the starting solutions have significant effects on the phase transformation temperatures of the thermal hydrolysis reaction. As the reaction temperatures were raised, the conversion from the anatase phase to the rutile phase was increased. A core–shell morphology of the prepared TiO2 samples was suggested via the signals of the anatase phase and the rutile phase in UV–vis spectrum analysis. Through the isothermal heating process of the reaction kinetics, the controlling reaction in the phase transformation process from the anatase phase to the rutile phase was determined to be the three-dimensional phase boundary controlled process. The activation energy of the phase transformation was increased with an increase in the pH value of the starting solution. 相似文献
12.
A gel was formed when a mixture of TiOCl2 and tartaric acid was heated on a water bath. Ultrafine powders of TiO2 in the anatase phase were formed, when the gel was decomposed at 623 K and the mole ratio of tartaric acid to titanium was
2. The anatase phase was converted into rutile phase on annealing at higher temperatures, > 773 K. When initial ratio of titanium
to tartaric acid was < 2, the decomposition of gel leads to the formation of mixed phases of rutile and anatase. However,
pure rutile phase was not formed by the decomposition of gel for any ratio of tartaric acid and titanium. These powders were
characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and surface area measurements. The average
particle size obtained for anatase phase was 3 nm whereas it was 30 nm for rutile phase. Raman scattering experiments were
also performed to confirm both anatase and rutile phases. 相似文献
13.
Chin Wei Lai 《Journal of Experimental Nanoscience》2014,9(3):230-239
The effect of electrolyte pH and annealing temperature on the formation of TiO2 nanotube arrays in connection with the photoelectrochemical response was investigated in this article. Well-aligned TiO2 nanotube arrays were fabricated by anodisation of Ti foil in an electrolyte consisting of 1?M of glycerol (85?wt% of glycerol and 15?wt% of water) with 0.5?wt% of NH4F at 30?V for 30?min. The pH of the electrolyte was varied from pH 1 to 7. With the increase of electrolyte pH to neutral condition, the length of the nanotube arrays was increased from ~320 to 1100?nm. As-anodised TiO2 nanotube arrays were amorphous in nature. However, anatase phase was observed after annealing at 400°C and polycrystalline anatase and rutile phase could be observed by heating up to 500°C in air atmosphere. Based on the results obtained, the length and crystalline phases of TiO2 nanotube arrays affect the performance of photoelectrochemical response and photoconversion efficiency significantly. 相似文献
14.
Bojan A. Marinkovic Yann C. Fredholm Edisson Morgado Paula M. Jardim Fernando Rizzo 《Materials Characterization》2010,61(10):1009-1017
Sodium containing one-dimensional nanostructured layered titanates (1-D NSLT) were produced both from commercial anatase powder and Brazilian natural rutile mineral sands by alkali hydrothermal process. The 1-D NSLT were chemically modified with proton, cobalt or iron via ionic exchange and all products were additionally submitted to intensive inorganic acid aging (pH = 0.5) for 28 days. The morphology and crystal structure transformations of chemically modified 1-D NSLT were followed by transmission electron microscopy, powder X-ray diffraction, selected area electron diffraction and energy dispersive spectroscopy. It was found that the original sodium rich 1-D NSLT and cobalt substituted 1-D NSLT were completely converted to rutile nanoparticles, while the protonated form was transformed in a 70%–30% (by weight) anatase–rutile nanoparticles mixture, very similar to that of the well-known TiO2-photocatalyst P25 (Degussa). The iron substituted 1-D NSLT presented better acid resistance as 13% of the original structure and morphology remained, the rest being converted in rutile. A significant amount of remaining 1-D NSLT was also observed after the acid treatment of the product obtained from rutile sand. The results showed that phase transformation of NSLT into titanium dioxide polymorph in inorganic acid conditions were controllable by varying the exchanged cations.Finally, the possibility to transform, through acid aging, 1-D NSLT obtained from Brazilian natural rutile sand into TiO2-polymorphs was demonstrated for the first time to the best of authors' knowledge, opening path for producing TiO2-nanoproducts with different morphologies through a simple process and from a low cost precursor. 相似文献
15.
Jorge Medina-Valtierra Claudio Frausto-ReyesMartín Ortiz-Morales 《Materials Letters》2012,66(1):172-175
Anatase (TiO2) thin films were obtained by immersion of glass plates into a titanium sol-gel precursor followed by calcination at 450 °C for 3 h. The Raman results for the CO2 laser irradiated TiO2 films show that laser radiation is able to promote favorable changes of anatase phase in anatase/rutile mixtures. Nevertheless, the transformation process level depends on laser characteristics and scan speed of the radiation treatment. 相似文献
16.
Nano-sized homogeneously distributed TiO2-20, -40, -60 wt.% SrO composite powders were successfully synthesized by a sol-gel method. The as-received amorphous TiO2—20 wt.% SrO composite powders were crystallized with anatase TiO2 at around 750 °C. As calcination temperatures increased, the anatase TiO2 crystalline phase was transformed to rutile TiO2 at about 900 °C, whereas nano-sized, squarish SrTiO3 phase was detected. The peaks obtained after calcining at 1050 °C mainly exhibited the rutile TiO2 and SrTiO3 phases. However, a small number of SrO2 peaks were also detected. For the comparison of photocatalytic activity depending on light sources, TiO2-SrO composite powders were tested in phenol degradation. TiO2-60 wt.% SrO composite powder showed good visible light photoactivity for the photo-oxidation of phenol. 相似文献
17.
For dye-sensitized solar cells application, in this study, we have synthesized TiO2 thin films at deposition temperature in the range of 300–750 °C by metalorganic chemical vapor deposition (MOCVD) method. Titanium(IV) isopropoxide, {TIP, Ti(OiPr)4} and Bis(dimethylamido)titanium diisopropoxide, {BTDIP, (Me2N)2Ti(OiPr)2} were used as single source precursors that contain Ti and O atoms in the same molecule, respectively. Crack-free, highly oriented TiO2 polycrystalline thin films with anatase phase were deposited on Si(1 0 0) with TIP at temperature as low as 450 °C. XRD and TED data showed that below 500 °C, the TiO2 thin films were dominantly grown in the [2 1 1] direction on Si(1 0 0), whereas with increasing the deposition temperature to 700 °C, the main film growth direction was changed to [2 0 0]. Above 700 °C, however, rutile phase TiO2 thin films have only been obtained. In the case of BTDIP, on the other hand, only amorphous film was grown on Si(1 0 0) below 450 °C while a highly oriented anatase TiO2 film in the [2 0 0] direction was obtained at 500 °C. With further increasing deposition temperatures over 600 °C, the main film growth direction shows a sequential change from rutile [1 0 1] to rutile [4 0 0], indicating a possibility of getting single crystalline TiO2 film with rutile phase. This means that the precursor together with deposition temperature can be one of important parameters to influence film growth direction, crystallinity as well as crystal structure. To investigate the CVD mechanism of both precursors in detail, temperature dependence of growth rate was also carried out, and we then obtained different activation energy of deposition to be 77.9 and 55.4 kJ/mol for TIP and BTDIP, respectively. Also, we are tested some TiO2 film synthesized with BTDIP precursor to apply dye-sensitized solar cell. 相似文献
18.
《Materials Letters》2007,61(8-9):1658-1661
Erbium doped TiO2 nanocrystals with the structures of anatase, pyrochlore Er2Ti2O7, and rutile, characterized by X-ray diffraction, have been obtained at different annealing temperatures from 300 °C to 900 °C. The nanocrystalline size for anatase TiO2 is reduced with increasing doped erbium concentration. Following ultraviolet 325 nm irradiation, the intensity of the green emission is the most intense for the TiO2:Er3+ nanocrystals with a structure of pyrochlore Er2Ti2O7, which evolves from the structure of anatase annealed at 800 °C. Moreover, following ultraviolet 325 nm and infrared 980 nm irradiation, the visible emission spectra for the nanocrystals annealed at 900 °C change drastically. Correspondingly, the structure of anatase disappears, while that of rutile becomes dominant, which indicates that phase transformation occurs. 相似文献
19.
Lin Dong Ying Ma Yuwei Wang Yongtao Tian Guotian Ye Xiaolin Jia Guoxi Cao 《Materials Letters》2009,63(18-19):1598-1600
Nitrogen-doped TiO2 nanotubes were synthesized by annealing of the anodized titania nanotubes with ammonia at the temperature of 500 °C. The ordered structure of titania nanotubes maintained after the nitrogen doping process, as is evidenced by SEM observations. Detailed structural analysis revealed that the phase transformation temperature of titania nanotube from anatase to rutile is decreased after nitrogen doping. The XRD patterns of nitrogen-doped titania exhibit an increased peak intensity and a decreased FWHM in the (110) peak of rutile in comparison with those of undoped titania under the same annealing conditions, indicating that nitrogen doping may have facilitated the phase transition at the annealing temperature of 500 °C, which is in consistence with the analysis of Raman spectra as the comparison of A1g and Eg Raman peaks of rutile in the nitrogen-doped and undoped titania. 相似文献