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1.
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   

2.
The kinetics of photodegradation of methylene blue (MB) dye by titanium dioxide (TiO2) powder were investigated using elementary reactions. TiO2 powders were prepared by a selective leaching method consisted of processes of CaHPO4 precipitation, heat treatment, and acid leaching to obtain high crystalline anatase. The obtained TiO2 samples had wide ranges of specific surface areas (5–23 m2/g) and densities of Ti3+ defects (90–480×1012spin/g) without a significant change in the anatase phase ratio ranging 0.86–0.91 in mass ratio. The MB photodegradation rate was expressed as functions of specific surface area and density of Ti3+ defects under the experimental condition that the photodegradation rate was proportional to UV irradiation intensity and the adsorbed MB amount was proportional to specific surface area. A proposed equation for calculation of photodegradation ate demonstrated greater effect of specific surface area than density of Ti3+ defects for MB photodegradation.  相似文献   

3.
In this work, a one-step solid-phase sintering process via TiO2 and Li2CO3 under an argon atmosphere, with ultra-fine titanium powder as the modifying agent, was used to prepare a nano-sized Li4Ti5O12/Ti composite (denoted as LTO–Ti) at 800 °C. The introduction of ultra-fine metal titanium powder played an important role. First, X-ray photoelectron spectroscopy demonstrates that Ti4+ was partially changed into Ti3+, through the reduction of the ultra-fine metal titanium powder. Second, X-ray diffraction revealed that the ultra-fine metal titanium powder did not react with the bulk structure of Li4Ti5O12, while some pure titanium peaks could be seen. Additionally, the size of LTO–Ti particles could be significantly reduced from micro-scale to nano-scale. The structure and morphology of LTO–Ti were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. Electrochemical tests showed a charge/discharge current of 0.5, 1, 5, and 10 C; the discharge capacity of the LTO–Ti electrode was 170, 161, 140, and 111 mAh g?1. It is believed that the designed LTO–Ti composite makes full use of both components, thus offering a large contact area between the electrolyte and electrode, high electrical conductivity, and lithium-ion diffusion coefficient during electrochemical processes. Furthermore, ultra-fine titanium powder, as the modifying agent, is amenable to large-scale production.  相似文献   

4.
Nanocrystalline TiO2 powder is synthesized using a novel reactive plasma process in which the precursor TiH2 powder is oxidized through thermal plasma in-flight route to generate nanocrystalline TiO2 powder. The synthesized powder consists of nano-sized TiO2 particles, both anatase and rutile phases, in which anatase is the predominant phase. An additional feature of the plasma synthesized TiO2 powder is the higher surface concentration of Ti3+ state and hydroxyl group that enhance its photocatalytic activity. The photocatalytic inactivation of Gram-positive Enterococcus and Gram-negative Klebsiella bacteria is studied using the plasma synthesized TiO2 nanopowder with 365 nm ultraviolet (UV) light. The mechanism behind the photocatalytic disinfection of bacteria is discussed. The plasma synthesized TiO2 nanopowder catalyst is found effective in killing Enterococcus and Klebsiella. The results corroborated that the plasma synthesized TiO2 powder can be used for waste water treatment and water purification.  相似文献   

5.
铁钛共掺强韧化蓝宝石晶体的研究   总被引:1,自引:0,他引:1       下载免费PDF全文
研究了铁钛共掺蓝宝石(Fe, Ti: Sapphire)晶体的常温力学性能. 采用泡生法技术生长了尺寸为ø180 × 280 mm3质量为30 kg的 Fe, Ti: Sapphire晶体. 实验发现, 在蓝宝石晶体中掺入Fe2O3和TiO2以及相应的热处理可以显著提高晶体常温断裂强度、表面硬度和断裂韧性, 而不损害晶体的可见和近红外透过性能; 掺入的Fe2O3其Fe3+对Al3+ 的取代作用导致晶体内应力的增加, 掺入的TiO2其Ti4+ 热处理时结晶出的第二相针状晶体的韧化效应, 均对Fe, Ti: Sapphire晶体的力学性能的提高具有重要作用. 研究对我国实现高强蓝宝石晶体应用材料具有重要现实意义. 关键词: 蓝宝石晶体 力学性能 铁钛共掺 热处理  相似文献   

6.
Excess electrons play a key role in many of the properties of Titanium dioxide (TiO2). Understanding their behaviour is important for improving the performance of TiO2 in energy-related applications. Here, we describe a DFT + U study of the locations of the unpaired electron (UPE) on rutile TiO2(110) (R-TiO2(110)) surface and H2O/R-TiO2(110) surface. Our results show that the subsurface are preferred with R-TiO2(110) surface. In contrast to previous studies, we find that the UPE tends to migrate to the surface H2O-Ti5c (the five-coordinated titanium (Ti5c) at surface with H2O adsorption) with the increasing of H2O coverage and UPE concentration. In addition, we have shown that the UPE plays an important role in the O-H bond dissociation and other important elementary reactions in photo-catalytic H2O dissociation on R-TiO2(110) such as H, OH and H2 desorption. Specifically, it enhances the O-H bond dissociation, as well as H and H2 desorption from bridging hydroxyl and Ti5c-OH (the Ti5c with OH adsorption), but hinders the OH and H desorption from Ti5c. We believe our results afford a further understanding of the adsorbent dependent UPE migration, and the role of UPE in the surface reactions.  相似文献   

7.
The sonocatalytic degradation of EDTA (C0 = 5 10−3 M) in aqueous solutions was studied under 345 kHz (Pac = 0.25 W mL−1) ultrasound at 22–51 °C, Ar/20%O2, Ar or air, and in the presence of metallic titanium (Ti0) or core-shell Ti@TiO2 nanoparticles (NPs). Ti@TiO2 NPs have been obtained using simultaneous action of hydrothermal conditions (100–214 °C, autogenic pressure P = 1.0–19.0 bar) and 20 kHz ultrasound, called sonohydrothermal (SHT) treatment, on Ti0 NPs in pure water. Ti0 is composed of quasi-spherical particles (30–150 nm) of metallic titanium coated with a metastable titanium suboxide Ti3O. SHT treatment at 150–214 °C leads to the oxidation of Ti3O and partial oxidation of Ti0 and formation of nanocrystalline shell (10–20 nm) composed of TiO2 anatase. It was found that Ti0 NPs do not exhibit catalytic activity in the absence of ultrasound. Moreover, Ti0 NPs remain inactive under ultrasound in the absence of oxygen. However, significant acceleration of EDTA degradation was achieved during sonication in the presence of Ti0 NPs and Ar/20%O2 gas mixture. Coating of Ti0 with TiO2 nanocrystalline shell reduces sonocatalytic activity. Pristine TiO2 anatase nanoparticles do not show a sonocatalytic activity in studied system. Suggested mechanism of EDTA sonocatalytic degradation involves two reaction pathways: (i) sonochemical oxidation of EDTA by OH/HO2 radicals in solution and (ii) EDTA oxidation at the surface of Ti0 NPs in the presence of oxygen activated by cavitation event. Ultrasonic activation most probably occurs due to the local heating of Ti0/O2 species at cavitation bubble/solution interface.  相似文献   

8.
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   

9.
About one monolayer of Ti3+ species is detectable at the surface of reduced SrTiO3(111) single crystals by XPS and UPS. O2, H2 and H2O have been adsorbed in the dark and the decrease on the concentration of the Ti3+ species has been monitored as a function of the gas exposures. Subsequent band gap illumination partially restores the Ti3+ initial concentration in the cases of O2 and H2 exposures but not in the case of H2O. The Ti3+ photogeneration on the oxygen covered surface is associated with oxygen photodesorption as indicated by XPS and UPS. UPS measurements give evidence for surface hydroxylation resulting from water and hydrogen adsorption. The activity of the stoichiometric SrTiO3(111) crystal face for O2 and H2 adsorption is very low when compared with the reduced SrTiO3 samples.  相似文献   

10.
观察到还原SrTiO3表面三价Ti离子引起的表面态的存在。分析了它在太阳光分解水中所起作用,以及光照在恢复活性中的作用。 关键词:  相似文献   

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