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1.
K. V. Stepanova N. M. Yakovleva A. N. Kokatev H. Pettersson 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2016,10(5):933-941
Oxide films obtained during anodization of Ti?40% Al sintered powder samples in fluorine-containing electrolytes are investigated. With scanning electron microscopy and X-ray phase analysis, it is demonstrated that an X-ray amorphous nanoporous anodic oxide film is formed on the surface of the powder microparticles under optimal anodization conditions. After annealing at T = 1093 K in air and vacuum (10?2 Pa), the oxide films are revealed to crystallize with its regular porous structure retained. The composition of the polycrystalline anodic-oxide films annealed in air is a mixture involving TiO2 (anatase and rutile) and α- and γ-Al2O3 phases and Ti2O3 and Al2TiO5 traces. The vacuum annealing process makes it possible to identify TiO2, in which anatase is the main phase, α- and γ-Al2O3, and Ti2O3 and TiO traces. However, rutile is not revealed. The presented results indicate that the application of the anodic nanostructuring of Ti?40% Al powders is promising for the obtainment of new photocatalytic active nanomaterials. 相似文献
2.
The effect of low pressure radio frequency (rf) plasma treatment on TiO2 surface states has been studied using X-ray photoelectron spectroscopy. Three different oxidation states of oxygen in untreated TiO2 powder were observed, which suggests the existence of adsorbed water and carbon on the surface. The ratio of oxygen to titanium (O/Ti) was decreased for the low ion dose plasma treated samples due to desorption of water from the surface. In the case of Ti 2p about 20% of surface states were converted to Ti3+ 2p3/2 state after plasma treatment with a very good stability, whereas untreated TiO2 remained mostly as Ti4+ state. A rapid decrease in the ratio of carbon to titanium (C/Ti) at TiO2 surface was also observed after plasma treatment and more than 90% of carbon atoms were removed from the surface. Therefore, the plasma treatment of TiO2 has advantages to surface carbon cleaning, increasing O− and Ti3+ surface states, hence improving the activity of TiO2 for different environmental, energy and biological applications. 相似文献
3.
The influences of microwave heating on the phase transformation of titania slag were systematically investigated. The thermal stability, surface chemical functional groups and microstructure of the titania slag before and after microwave heating, at a temperature of 950?°C for 60 min, were also analyzed using thermogravimetry and differential thermal analysis (TG-DSC), Fourier transform infrared spectroscopy (FT-IR) spectrum and scanning electron microscope (SEM), respectively. The TG-DSC analysis revealed that the phase transformation of the titania slag from anatase TiO2 to rutile TiO2 occurred between 750 and 1000 °C. The FT-IR rustles demonstrate that the banding form of Ti4+, Ti3+ and Ti2+ ions and the methyl groups on the surface of the titania slag has changed and a new chemical bond Ti–OH was formed. The results of SEM showed that a large number of regulation rutile TiO2 crystals were found on the surface of the microwave-treated samples and the synthetic rutile has been synthesized successfully using microwave heating. 相似文献
4.
通过高分辨的扫描隧道显微术研究并比较了金红石型TiO2(110)-(1×1)和锐钛矿型TiO2(001)-(1×4)两种表面的活性位点. 在金红石型TiO2(110)-(1×1)表面, 观察到氧空位缺陷是O2和CO2分子的活性吸附位点,而五配位的Ti原子是水分子和甲醇分子的光催化反应活性位点.在锐钛矿型TiO2(001)-(1×4)表面,观察到完全氧化的表面,Ti原子更可能是六配位的,H2O和O2分子均不易在这些Ti原子上吸附.经还原后表面出现富Ti的缺陷位点, 这些缺陷位点对H2O和O2分子表现出明显的活性. 锐钛矿型TiO2(001)-(1×4)表面的吸附和反应活性并不具有很高的活性,某种程度上其表现出的活性似乎低于金红石型TiO2(110)-(1×1)表面. 相似文献
5.
Melinda VargováGustav Plesch Ulrich F. Vogt Miroslav ZahoranMichal Gorbár Karol Jesenák 《Applied Surface Science》2011,257(10):4678-4684
TiO2 thick films deposited on macroporous reticulated Al2O3 foams with pore size of 10 ppi and 15 ppi were prepared using dip coating from slurries of Aeroxide® P25 nanopowder and precipitated titania. All prepared films have sufficiently good adhesion to the surface of the substrate also in case of strongly cracked films. No measurable release of deposited TiO2 after repeated photocatalytic cycles was observed. The photocatalytic activity was characterized as the rate of mineralization of aqueous phenol solution under irradiation of UVA light by TOC technique. The best activity was obtained with Aeroxide® P25 coated Al2O3 foam with the pore size of 10 ppi, annealed at 600 °C. The optimal annealing temperature for preparation of films from precipitated titania could be determined at 700 °C. Films prepared by sol-gel deposition technique were considerably thinner compared to coatings made of suspensions and their photocatalytic activity was significantly smaller. 相似文献
6.
I. A. Kurzina N. A. Popova E. L. Nikonenko M. P. Kalashnikov K. P. Savkin Yu. P. Sharkeev E. V. Kozlov 《Bulletin of the Russian Academy of Sciences: Physics》2012,76(1):64-68
The results from microstructure and phase composition investigations of titanium in different structural states (with average
grain sizes of 0.3 μm, 1.5 μm, and 17 μm) are presented following Al ion implantation using the Mevva-V.RU source (irradiating
dose, 1018 ion/cm2). The implanted multiphase layers are found to form on the base of α-Ti grains. The size, shape, and localization of the
formed phases (TiO2, Ti2O, TiC, Ti3Al, Al3Ti) depend strongly on the grain size of titanium target. It is shown that the nanostructural particles of TiO2 phase are located mainly on dislocations in the body of target grains. A Ti2O surface layer is found to arise in titanium with a grain size of 17 μm. It is established that an ordered Ti3Al phase is located at a depth of more than 200 nm in the implanted layer along the bounaries of the titanium grains. 相似文献
7.
The preparation and characterization of nanoparticle TiO2/Ti films and their photocatalytic activity
《Journal of Physics and Chemistry of Solids》2003,64(4):615-623
Nanoparticle TiO2/Ti films were prepared by a sol–gel process using Ti(OBu)4 as raw material, the as-prepared film samples were also characterized by TG-DTA, XRD, TEM, SEM, XPS, DRS, PL, SPS and EFISPS testing techniques. TiO2 nanoparticles experienced two processes of phase transition, i.e. amorphous to anatase and anatase to rutile at the calcining temperature range from 450 to 700 °C. TiO2 nanoparticles calcined at 600 °C had similar composition, structure, morphology and particle size with the internationally commercial P-25 TiO2 particles. Thus, the conclusion that 600 °C might be the most appropriate calcining temperature during the preparation process of nanoparticle TiO2/Ti film photocatalysts could be made by considering the main factors such as the properties of TiO2 nanoparticles, the adhesion of nanoparticle TiO2 film to Ti substrate, the effects of calcining temperature on Ti substrate and the surface characteristics and morphology of nanoparticle TiO2/Ti film for the practice view. The Ti element mainly existed on the nanoparticle TiO2/Ti(3) film calcined at 600 °C as the chemical state of Ti4+, while O element mainly existed as three kinds of chemical states, i.e. crystal lattice oxygen, hydroxyl oxygen and adsorbed oxygen with increasing band energy. Its photoluminescence (PL) spectra with a peak at about 380 nm could be observed using 260 nm excitation, possibly resulting from the electron transition from the bottom of conduction band to the top of valence band. The PL peak position was nearly the same as the onset of its diffuse reflection spectra (DRS) and surface photovoltage spectroscopy (SPS), demonstrating that the effects of the quantum size on optical property were greater than that of the Coulomb and surface polarization. The PL spectra with two peaks related to the anatase and rutile, respectively, could be observed using the excited wavelength of 310 nm. Weak PL spectra could be observed using the excited wavelength of 450 nm, resulting from surface states. In addition, during the experimental process of the photocatalytic degradation phenol, the photocatalytic activity of nanoparticle TiO2/Ti film with three layers calcined at 600 °C was the highest. 相似文献
8.
Liangbin Xiong Fan Yang Nannan Yan Mingqiang Qiu 《Journal of Physics and Chemistry of Solids》2011,72(9):1104-1109
Photocatalytic experiment results under visible light demonstrate that both TiO2 and Cu2O have low activity for brilliant red X-3B degradation and neither can produce H2 from water splitting. In comparison, TiO2/Cu2O composite can do the both efficiently. Further investigation shows that the formation of Ti3+ under visible light has great contribution. The mechanism of photocatalytic reaction is proposed based on energy band theory and experimental results. The photogenerated electrons from Cu2O were captured by Ti4+ ions in TiO2 and Ti4+ ions were further reduced to Ti3+ ions. Thus, the photogenerated electrons were stored in Ti3+ ions as the form of energy. These electrons trapped in Ti3+ can be released if a suitable electron acceptor is present. So, the electrons can be transferred to the interface between the composite and solution to participate in photocatalytic reaction. XPS spectra of TiO2/Cu2O composite before and after visible light irradiation were carried out and provided evidence for the presence of Ti3+. The image of high-resolution transmission electron microscopy demonstrates that TiO2 combines with Cu2O tightly. So, the photogenerated electrons can be transferred from Cu2O to TiO2. 相似文献
9.
A novel method of synthesizing Ti3+-doped TiO2 was proposed. Ti3+-doped TiO2 hollow spheres were prepared with different thickness of carbon shell by using atmospheric pressure plasma jet generated by dual-frequency power sources. The as-synthesized Ti3+-doped TiO2 hollow microspheres were characterized by X-ray diffraction (XRD) pattern, scanning electron microscope (SEM) images, high-resolution transmission electron microscopy (HRTEM) images, Raman spectra, X-ray photoelectron spectroscopy (XPS), and UV–vis spectra. These results indicated that these samples had mixed phases of anatase and rutile and the structure of hollow sphere varied with different thickness of carbon shell. The Ti-O-C chemical bond was the connection between the TiO2 hollow sphere and carbon layer. Amount of Ti3+ ions were found, which were accompanied with the formation of oxygen vacancies. Meantime, the as-synthesized catalysts also display strong absorption in the visible light region and have a narrow band energy gap. Optical emission spectroscopy (OES) was used to observe different excited species in the discharge area. These results showed that the oxygen content had a significant impact on the number of oxygen vacancies. Finally, the photocatalytic activities of as-prepared samples were evaluated by decomposition of rhodamine B aqueous solution, which showed better photocatalytic activity under UV–vis light irradiation. 相似文献
10.
In the present study, a two-step method was applied to synthesise Cu2+-modified TiO2 nanorod array thin films for photocatalytic processes. TiO2 nanorod array thin films were synthesised by a hydrothermal method and then modified with an ultrasonic-assisted sequential cation adsorption method. The samples were characterised by X-ray diffraction (XRD), UV–vis diffuse reflectance spectra (DRS), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy and inductively coupled plasma mass spectroscopy (ICP-MS) analysis. The photoelectrochemical properties of the samples were evaluated by linear sweep voltammetry and Mott–Schottky analysis; photocatalytic activities were tested by methylene blue degradation under visible light. The photocurrent density of the TiO2/FTO sample modified with 50 mM Cu2+ solution was 26 times higher than that of the unmodified TiO2/FTO sample. Additionally, methylene blue degradation efficiency under visible light was increased 40% with respect to the efficiency of the unmodified sample. The mechanism of the photocatalytic activity enhancement of Cu2+-modified TiO2 nanorod films was discussed. 相似文献
11.
12.
《Surface science》1988,197(3):L281-L286
Angular resolved XPS measurements were performed on platinum particles deposited on the TiO2 (100) surface. High temperature reduction at 733 K in hydrogen at atmospheric pressure caused the appearance of lower binding energy states in the titanium 2p region. These states corresponded to the formation of Ti2+ and Ti3+ ions on the surface. From the angular dependencies of the relative intensities of the Ti 2p and Pt 4f peaks, it appeared that the reduced Ti species were located in the outermost surface region, on the surface of the Pt particles. 相似文献
13.
Silver nanorods with average diameters of 120-230 nm and aspect ratio of 1.7-5.0 were deposited on the surface of TiO2 films by photoelectrochemical reduction of Ag+ to Ag under UV light. The composite films prepared on soda-lime glass substrates were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results show that the TiO2 film after UV irradiation in AgNO3 solution is composed of anatase phase TiO2 and metallic silver with face centered cubic structure. Other compounds cannot be found in the final films. The maximum deposition content of silver particles on the surface of TiO2 film was obtained with the AgNO3 concentration of 0.1 M. The kinetic growth rates of silver particles can be controlled by photocatalytic activity of TiO2 films. The studies suggest that the growth rates of silver particles increase with the enhancement of photocatalytic activity of TiO2 films. The maximum growth rate of silver particles loaded on TiO2 films can be up to 0.353 nm min−1 among samples 1#, 2# and 3#, while the corresponding apparent rate constant of TiO2 is 1.751 × 10−3 min−1. 相似文献
14.
Nanostructured sol-gel TiO2 thin films spin coated on silicate glass plates are subjected to excimer (KrF*) pulsed laser irradiation in order to tailor their structure and photocatalytic properties. The surface morphology of virgin and laser-processed films are followed applying electron optical imaging and atomic force microscopy. The evolution of the surface roughness and pore formation are shown to be accompanied by optical absorption edge shift to infrared wavelength range. Conventional X-ray diffraction analysis and high-resolution transmission electron imaging are applied in order to obtain information on the phase composition. Co-existence of amorphous and anatase TiO2 phases in nonirradiated sol-gel films is found. It is established that after laser processing the most intense XRD anatase peak is shifted to lower 2θ range. The analysis of high-resolution transmission electron images of film profiles evidences for the laser induced phase transitions. Formation of rutile and brookite TiO2 accompanied by evolution of oxygen deficient TinO2n−1 phases are identified in the subsurface region. The contribution of laser processing for increasing the photocatalytic efficiency of laser-modified films toward the oxidation of methylene blue water solution is demonstrated. The results obtained reveal a novel-processing route for designing sol-gel titania films with improved photocatalytical activity. 相似文献
15.
Shalendra Kumar S. GautamG.W. Kim Faheem AhmedM.S. Anwar K.H. ChaeH.K. Choi H. ChungB.H. Koo 《Applied Surface Science》2011,257(24):10557-10561
We report structural, magnetic and electronic structure study of Mn doped TiO2 thin films grown using pulsed laser deposition method. The films were characterized using X-ray diffraction (XRD), dc magnetization, X-ray magnetic circular dichroism (XMCD) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy measurements. XRD results indicate that films exhibit single phase nature with rutile structure and exclude the secondary phase related to Mn metal cluster or any oxide phase of Mn. Magnetization studies reveal that both the films (3% and 5% Mn doped TiO2) exhibit room temperature ferromagnetism and saturation magnetization increases with increase in concentration of Mn doping. The spectral features of XMCD at Mn L3,2 edge show that Mn2+ ions contribute to the ferromagnetism. NEXAFS spectra measured at O K edge show a strong hybridization between Mn, Ti 3d and O 2p orbitals. NEXAFS spectra measured at Mn and Ti L3,2 edge show that Mn exist in +2 valence state, whereas, Ti is in +4 state in Mn doped TiO2 films. 相似文献
16.
D. Leinen A. Fernández J. P. Espinós A. R. González-Elipe 《Applied Physics A: Materials Science & Processing》1996,63(3):237-242
Compositional and chemical changes in TiO2 and Ph, Ni, Al and Ba titanates induced by bombardment with Ar+ and O
2
+
ons of different energies have been studied quantitatively by XPS. An increase of preferential loss of oxygen and, in case of PbTiO3, of lead has been observed when increasing the Ar+ ion energy from 3.5 to 10 keV. Because of oxygen loss, Ti4+ species reduce to Ti3+ and Ti2+. In addition, the loss of oxygen from PbTiO3 and NiTiO3 leads to the metallic state of nickel and lead, whereas aluminium and barium in Al2TiO5 and BaTiO3 maintain their chemical state (i.e., Al3+ and Ba2+). Bombardment with OZ ions of PbTiO3 and NiTiO3 leads to a partial reduction of Pb and Ni. This metallization and the preferential loss of lead are more efficient at higher ion energies for both, O
2
+
and Ar+ bombardment. The results are discussed in terms of chemical stabilities and the possibility of oxygen diffusion in the bombarded oxides. 相似文献
17.
Titanium dioxide (TiO2) films were fabricated by cosputtering titanium (Ti) target and SiO2 or Si slice with ion-beam-sputtering deposition (IBSD) technique and were postannealed at 450 °C for 6 h. The variations of oxygen bonding, which included high-binding-energy oxygen (HBO), bridging oxygen (BO), low-binding-energy oxygen (LBO), and three chemical states of titanium (Ti4+, Ti3+ and Ti2+) were analyzed by X-ray photoelectron spectroscopy (XPS). The enhancement of HBO and reduction of BO in O 1s spectra as functions of SiO2 or Si amount in cosputtered film imply the formation of Si-O-Ti linkage. Corresponding increase of Ti3+ in Ti 2p spectra further confirmed the property modification of the cosputtered film resulting from the variation of the chemical bonding. An observed correlation between the chemical structure and optical properties, refractive index and extinction coefficient, of the SiO2 or Si cosputtered films demonstrated that the change of chemical bonding in the film results in the modification of optical properties. Furthermore, it was found that the optical properties of the cosputtered films were strongly depended on the cosputtering targets. In case of the Si cosputtered films both the refractive indices and extinction coefficients were reduced after postannealing, however, the opposite trend was observed in SiO2 cosputtered films. 相似文献
18.
19.
The competitive growth of cubic domains in Ti1–xAlxN films studied by diffraction anomalous near‐edge structure spectroscopy
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Y. Pinot M.‐H. Tuilier M.‐J. Pac C. Rousselot D. Thiaudière 《Journal of synchrotron radiation》2015,22(6):1440-1449
Titanium and aluminium nitride films deposited by magnetron sputtering generally grow as columnar domains made of oriented nanocrystallites with cubic or hexagonal symmetry depending on Al content, which are embedded in more disordered grain boundaries. The substitution of Al atoms for Ti in the cubic lattice of the films improves their resistance to wear and oxidation, allowing their use as protective coatings. Ti K‐edge X‐ray absorption spectroscopy, which probes both crystallized and more disordered grain boundaries, and X‐ray diffraction anomalous fine structure, which is sensitive to short‐ and long‐range order within a given crystallized domain, are carried out on a set of Ti1–xAlxN films deposited by magnetron sputtering on Si substrates. Attention is paid to the shape of the pre‐edge region, which is sensitive to the symmetry of the site occupied by Ti atoms, either octahedral in face‐centred‐cubic Ti‐rich (TiN, Ti0.54Al0.46N) samples or tetrahedral in hexagonal‐close‐packed Al‐rich (Ti0.32Al0.68N) films. In order to obain information on the titanium environment in the well crystallized areas, subtraction of the smooth part of the energy‐dependent structure factor for the Bragg reflections is applied to the pre‐edge region of the diffraction anomalous data in order to restore their spectroscopic appearance. A flat pre‐edge is related to the typical octahedral environment of Ti atoms for cubic reflections. The difference observed between pre‐edge spectra associated with face‐centred‐cubic 200 and 111 Bragg reflections of Ti0.54Al0.46N is assigned to Ti enrichment of 111 large well ordered domains compared with the more disordered 200 ones. The sharp peak observed in the spectrum recorded from the hexagonal 002 peak of Ti0.32Al0.68N can be regarded as a standard for the pure tetrahedral Ti environment in hexagonal‐close‐packed nitride. 相似文献
20.
In the present work the influence of the OH groups on the photocatalytic activity and the photoinduced hydrophilicity of microwave assisted sol-gel TiO2 films was investigated. The prepared TiO2 films were characterized using XRD and AFM. Furthermore, the surface of the TiO2 films was examined by help of XPS in order to determine the amount of OH groups before and after UV irradiation at different humidities. The activity of the TiO2 films was determined using stearic acid as a model compound and the photoinduced superhydrophilicity was investigated through contact angle measurements.The results of this investigation showed that the microwave assisted sol-gel technique produces highly homogeneous and efficient TiO2 films without the need for heat treatment for crystallization. Based on the conducted experiments it is suggested that the amount of OH groups on the TiO2 surface highly influence the photocatalytic activity and the photoinduced superhydrophilicity and that the two mechanisms may be closely related. It is suggested that the superhydrophilicity is obtained through a combination of photocatalytic degradation of organic contaminants and surface structural changes in form of an increased amount of OH-groups. 相似文献