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1.
Pure anatase TiO2 nanoparticles were synthesized by microwave assisted sol–gel method and further characterized by powder X-ray diffraction (XRD), energy dispersive x-ray analysis (EDAX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–Visible spectrophotometer, SEM images showed that TiO2 nanoparticles were porous structure. The XRD patterns indicated that TiO2 after annealed at 300 °C for 3 h was mainly pure anatase phase. The crystallite size was in the range of 20–25 nm, which is consistent with the results obtained from TEM images. Microwave heating offers several potential advantages over conventional heating for inducing or enhancing chemical reactions.  相似文献   

2.
Rutile TiO2 nanorod films have been successfully prepared on titanium substrate via a hydrothermal method using Tetra-n-butyl titanate as Ti source in the presence of concentrated hydrochloric acid. The effect of Ti substrate annealing treatment and adding of additional alkali metal chlorides in hydrothermal solution on the growth of TiO2 nanorod films has been studied using scanning electron microscopy (SEM), Raman spectroscopy, X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and water contact angle measurement. The growth mechanism of the TiO2 nanorods on Ti substrate has also been discussed. It has shown that the initial rutile film transformed from anatase promotes the nucleation and epitaxial growth of rutile TiO2 nanorods. The superior wettabilities of the TiO2 nanorods resulted from treatments of vacuum and ultraviolet show great potential for applications in orthopaedic, dental implants, and possible photocatalysis.  相似文献   

3.
4.
TiO2 anatase phase-mounted carbon aerogels (CAs) were synthesized via the sol–gel polymerization of a mixture of resorcinol, formaldehyde, and tetrabutyl orthotitanate, followed by gelation, supercritical drying, and carbonization in N2 atmosphere. Ethanol was selected as the solvent in the sol–gel polymerization process. The morphology and microstructural characteristics of the TiO2-mounted carbon aerogel sample were obtained using thermogravimetry, transmission electron microscopy, scanning electron microscopy, N2 adsorption–desorption, and X-ray diffraction methods. The total pore volume and average pore sizes increased with TiO2 addition. Titania phase in anatase form was found to be more homogeneously distributed in the CAs at 900 °C. The anatase–rutile transformation did not take place at carbonization temperatures from 500 to 1100 °C and cyclic voltammetry measurements showed that the TiO2-mounted CAs exhibit good reversibility and high specific capacity as electrode materials, and the anatase in the carbon structure were not involved in the redox reactions. Electrochemical impedance spectroscopy demonstrated that the CA electrode behaves as an excellent capacitor with low resistance.  相似文献   

5.
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   

6.
In this paper, we report on a nonaqueous synthesis of single crystalline anatase TiO2 nanorods by reaction between TiCl4 and benzyl alcohol at a low temperature of 80 °C. The resulting samples were characterized with X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy, nitrogen adsorption, X-ray photoelectron spectrometry and UV-vis diffuse reflectance spectroscopy. We proposed that the TiO2 nanorods were formed through an oriented attachment mechanism. More importantly, these single crystalline anatase TiO2 nanorods exhibited significantly higher photocatalytic activities than commercial photocatalyst P25. This study provides an environmentally friendly and economic approach to produce highly active TiO2 photocatalyst.  相似文献   

7.
This report aimed to study the effect of CdS doping in TiO2 on the phase transformation of TiO2 from anatase to rutile using X-ray diffraction (XRD) and Raman spectroscopy. CdS-doped TiO2 nanocomposites have been prepared and characterized using Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). We have observed that contrary to bare TiO2, phase transformation of TiO2 from anatase to rutile is hindered when doped with CdS at high temperature. Raman spectroscopy is found to be more sensitive for detection of the surface of TiO2 as compared to XRD.  相似文献   

8.
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   

9.
Hemisphere-like F-doped anatase TiO2 has been synthesized by hydrothermal treatment of TiF4 aqueous solution in the presence of starch at 130 °C for 10 h, and then calcined at 450 °C for 2.5 h in air. The as-synthesized product has been investigated by photocatalytic reaction test and characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray photoelectron spectroscopy (XPS), and UV–Vis diffuse reflectance spectra (DRS). The results showed that fluorine was successfully doped into the TiO2 hemispheres. The F-doped TiO2 hemispheres showed high visible light activity in degradation of acid orange II, which could be attributed to the creation of oxygen vacancies and good crystallinity.  相似文献   

10.
High surface area titanium glycolate microporous multi-faceted nanorods were synthesized from the reaction of titanium alkoxides (Ti(OEt)4, Ti(O i Pr)4, or Ti(O n Bu)4) with ethylene glycol, using a sol–gel reflux method. The specific surface area of the as-synthesized titanium glycolate nanorods obtained from Ti(OEt)4 is ~480 m2/g. A hot water treatment at 90 °C for 1 h transformed the titanium glycolate microporous nanorods into mesoporous anatase TiO2 nanorods. The shape of the nanorods was conserved after hot water treatment and the microporous to mesoporous transformation took place without significant change in the surface area (477 m2/g). Micro Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, solid state NMR, and nitrogen adsorption/desorption were used to characterize the samples. As a demonstration of potential applications, the thus formed mesoporous anatase TiO2 nanorods were tested for their photocatalytic efficiency in the degradation of crystal violet, and a photodegradation mechanism is proposed.  相似文献   

11.
Nanocrystalline titanium oxide thin films have been deposited by spin coating technique and then have been analyzed to test their application in NH3 gas-sensing technology. In particular, spectrophotometric and conductivity measurements have been performed in order to determine the optical and electrical properties of titanium oxide thin films. The structure and the morphology of such material have been investigated by X ray diffraction, Scanning microscopy, high resolution electron microscopy and selected area electron diffraction. The X-ray diffraction measurements confirmed that the films grown by this technique have good crystalline tetragonal mixed anatase and rutile phase structure. The HRTEM image of TiO2 thin film showed grains of about 50–60 nm in size with aggregation of 10–15 nm crystallites. Selected area electron diffraction pattern shows that the TiO2 films exhibited tetragonal structure. The surface morphology (SEM) of the TiO2 film showed that the nanoparticles are fine with an average grain size of about 50–60 nm. The optical band gap of TiO2 film is 3.26 eV. Gas sensing properties showed that TiO2 films were sensitive as well as fast in responding to NH3. A high sensitivity for ammonia indicates that the TiO2 films are selective for this gas.  相似文献   

12.
In this work, wood materials with UV-resistant ability were successfully fabricated by depositing submicrometer-sized rutile TiO2 spheres on wood surface using a facile and one-pot hydrothermal method. The prepared samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and attenuated total reflectance-Fourier transformation infrared (ATR-FTIR) techniques. ATR-FTIR spectra demonstrated that chemical bonds were formed at the interfaces between rutile TiO2 and wood owing to the presence of hydroxyl groups. Accelerated aging was used to measure the UV resistance of the original wood (OW), anatase TiO2/wood (ATW) and rutile TiO2/wood (RTW). Comparison with OW and ATW samples, RTW exhibited more UV-resistant ability due to high UV light absorption capability, superior light scattering property and high recombination of the photogenerated electron and hole of the submicrometer-sized rutile TiO2 spheres on the wood surface.  相似文献   

13.
Mesoporous anatase TiO2 nanopowder was synthesized by hydrothermal method at 130 °C for 12 h. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), HRTEM, and Brunauer-Emmett-Teller (BET) surface area. The as-synthesized sample with narrow pore size distribution had average pore diameter about 3-4 nm. The specific BET surface area of the as-synthesized sample was about 193 m2/g. Mesoporous anatase TiO2 nanopowders (prepared by this study) showed higher photocatalytic activity than the nanorods TiO2, nanofibers TiO2 mesoporous TiO2, and commercial TiO2 nanoparticles (P-25, JRC-01, and JRC-03). The solar energy conversion efficiency (η) of the cell using the mesoporous anatase TiO2 was about 6.30% with the short-circuit current density (Jsc) of 13.28 mA/cm2, the open-circuit voltage (Voc) of 0.702 V and the fill factor (ff) of 0.676; while η of the cell using P-25 reached 5.82% with Jsc of 12.74 mA/cm2, Voc of 0.704 V and ff of 0.649.  相似文献   

14.
Large-scale fan-shaped rutile TiO2 nanostructures have been synthesized by means of a simple hydrothermal method using only TiCl4 as titanium source and chloroform/water as solvents. The physicochemical features of the fan-shaped TiO2 nanostructures are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), nitrogen absorption-desorption, diffuse reflectance ultraviolet-visible spectroscopy (UV-vis) and Fourier transform infrared spectroscopy (FTIR). Structural characterization indicates that the fan-shaped TiO2 nanostructures are composed of several TiO2 nanorods with diameters of about 5 nm and lengths of 300-350 nm. The average pore size and BET surface area of the fan-shaped TiO2 nanostructures are 6.2 nm and 59 m2/g, respectively. Optical adsorption investigation shows that the fan-shaped TiO2 nanostructures possess optical band gap energy of 3.11 eV.  相似文献   

15.
We report the controlled hydrothermal growth of rutile TiO2 nanorods on Si wafers by using an anatase TiO2 nanodot film as an assisted growth layer. The anatase nanodot film was prepared on the wafer by phase-separation-induced self-assembly and subsequent heat-treatment at 500 °C. The nanodots on the wafer were then subjected to hydrothermal treatment to induce the growth of rutile TiO2 nanorod films. The size and dispersion density of the resulting TiO2 nanorods could be varied by adjusting the Ti ion concentration in the growth solution. The TiO2 nanorods were of the rutile phase and grew in the [001] direction. The growth mechanism reveals that the growth of the rutile nanorods was wholly dependent on the existence of rutile TiO2 seeds, which could be formed by the dissolution-reprecipitation of the anatase nanodots during hydrothermal treatment or under the high-temperature conditions of the subsequent heat-treatment of the as-prepared nanodots. In controlling the rutile nanorod growth, the anatase nanodots show more efficiency than a dense anatase film. Preliminary evaluations of the rutile nanorod films have demonstrated that the wettability changed from highly hydrophobic to superhydrophilic and that the photocatalytic activity was enhanced with increasing nanorod dispersion density.  相似文献   

16.
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   

17.
Nanostructured titanates with different morphologies such as nanoflakes, nanotubes, and nanofibers have been selectively synthesized by a simple solvothermal treatment of commercial anatase TiO2 using the mixed water–ethanol cosolvent at low alkaline concentration. The effects of solvothermal temperature, volume ratio of H2O to C2H5OH, amount of NaOH and solvents on the formation of titanate nanostructures have been systematically studied through X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). At low concentration of NaOH solution (the actual concentration of OH in the solution is only 0.58 M), different titanate nanostructures are achieved by simply changing the volume ratio of H2O to C2H5OH at 180 °C and titanate nanotubes can be synthesized between 100 and 180 °C. A probable formation mechanism is proposed based on XRD, SEM and TEM analysis. The influence of cosolvent on the transformation from anatase TiO2 to titanate is also investigated.  相似文献   

18.
The core/shell anatase TiO2 encapsulated poly(divinylbenzene) (PDVB@TiO2) hybrid microspheres were prepared by the two steps: (1) the copolymer particles (PDVB) were prepared by the radical precipitation copolymerization of divinylbenzene (DVB) and γ-[(methacryloxy)propyl]trimethoxysilane (KH-570); (2) tetrabutyl titanate (TBOT) was co-hydrolyzed with the trimethoxysilyl groups on the surfaces of the PDVB cores and then the amorphous TiO2 shell obtained was phase transformed to anatase TiO2 by acid peptization. The products were characterized by FT-IR, UV–vis, scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermal gravimetric analysis (TGA). Their photocatalytical activities were measured by the photo-degradation of methylene blue (MB). The polymer supported TiO2 photocatalysts prepared at low temperature, had better repetition because of the coupled action of KH-570 between the PDVB core and TiO2 shell. Furthermore, it could be easily separated from the solution by simple sedimentation.  相似文献   

19.
Nanopowders of TiO2 has been prepared using a microwave irradiation-assisted route, starting from a metalorganic precursor, bis(ethyl-3-oxo-butanoato)oxotitanium (IV), [TiO(etob)2]2. Polyvinylpyrrolidone (PVP) was used as a capping agent. The as-prepared amorphous powders crystallize into anatase phase, when calcined. At higher calcination temperature, the rutile phase is observed to form in increasing quantities as the calcination temperature is raised. The structural and physicochemical properties were measured using XRD, FT–IR, SEM, TEM and thermal analyses. The mechanisms of formation of nano-TiO2 from the metal–organic precursor and the irreversible phase transformation of nano TiO2 from anatase to rutile structure at higher temperatures have been discussed. It is suggested that a unique step of initiation of transformation takes place in Ti1/2O layers in anatase which propagates. This mechanism rationalizes several key observations associated with the anatase–rutile transformation.  相似文献   

20.
A liquid fuel high velocity oxy-fuel (HVOF) thermal spray process has been used to deposit TiO2 nanostructured coatings utilizing a commercially available nanopowder as the feedstock. The coatings were characterized by means of X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and transmission electron microscope (TEM), respectively. Photocatalytic activity was evaluated as a rate constant of decomposition reaction of methylene blue (MB) determined from the changes of relative concentration of MB with UV irradiation time. The results indicate that the sprayed TiO2 coatings were composed of both TiO2 phases viz. anatase and rutile, with different phase contents and crystallite sizes. A high anatase content of 80% by volume was achieved at 0·00015, fuel-to-oxygen ratio with nanostructure coating by grain size smaller than feedstock powder. Photocatalytic activity evaluation results indicated that all the TiO2 coatings are effective to degradation MB under UV radiation and their activities differ in different spray conditions. It is found that fuel flow rate strongly influenced on phase transformation of anatase to rutile and by optimizing the rate which can promote structural transformation and grain coarsening in coating and improving photocatalytic activity.  相似文献   

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