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1.
G.Q. Wang W. Lan G.J. HanY. Wang Q. SuX.Q. Liu 《Journal of Alloys and Compounds》2011,509(10):4150-4153
Various content Nb-doped TiO2 thin films were prepared by sol-gel process. XRD analysis shows that the existence of crystalline TiO2 in anatase and rutile form depends on the Nb content in the examined samples. It is observed that Nb promotes the anatase to rutile phase transition but has a depression effect on the anatase grain growth. It is found that incorporation of about 4 at.% of Nb completely transforms anatase TiO2 to the rutile form at a calcination temperature as high as 900 °C. The mechanism is proposed. Optical analyses show that the films have an average of 60% transmission in visible region. The energy gap values using Tauc's formula have also been estimated. The band gap of rutile Ti1−xNbxO2 solid solutions increases with increasing x. 相似文献
2.
随着海洋开发的逐步推进,海洋工程中的金属防腐蚀问题显得愈加重要。目前,可利用半导体的光电效应实现对金属的光生阴极保护,为改善常用的TiO2光电极材料的弱光吸收和低转换效率问题,文中利用水热法在FTO导电玻璃表面构建一维有序TiO2纳米棒阵列,并通过氢化处理提高TiO2对太阳光的吸收和光电流密度。考察了氢化TiO2纳米棒阵列在海水环境下对Q235碳钢的光生阴极保护特性,结果表明氢化TiO2纳米棒的光电流密度达到了2.12 mA/cm2,且稳定性良好;当Q235碳钢耦连于模拟太阳光照下的氢化TiO2纳米棒电极时,其界面反应电阻变小,电极电位较原先的腐蚀电位降低约349 mV,说明氢化TiO2纳米棒阵列能够对碳钢产生良好的光生阴极保护效应,且该效应在无光条件下能保持至少7 h。 相似文献
3.
The photoelectrochemical characteristics of plasma-sprayed porous TiO2, TiO2-5%ZnO, and TiO2-10%ZnO electrodes in 0.1 N NaOH solution were studied through a three-electrode cell system. The microstructure, morphology,
and composition of the electrodes were analyzed using an electron probe surface roughness analyzer (ERA-8800FE), scanning
electron microscopy, and x-ray diffraction. The results indicate that the sprayed electrodes have a porous microstructure,
which is affected by the plasma spray parameters and composition of the powders. The TiO2-ZnO electrodes consist of anatase TiO2, rutile TiO2, and Zn2Ti3O8 phase. The photoresponse characteristics of the plasma-sprayed electrodes are comparable to those of single-crystal TiO2, but the breakdown voltage is close to 0.5 V (versus that of a saturated calomel electrode). The short-circuit photocurrent
density (J
SC) increases with a decrease of donor concentration, which was calculated according to the Gartner-Butler model. For the lowest
donor concentration of a TiO2-5%ZnO electrode sprayed under an arc current of 600 A, the short-circuit J
SC is approximately 0.4 mA/cm2 higher than that of the TiO2 electrodes under 30 mW/cm2 xenon light irradiation. The J
SC increases linearly with light intensity.
The original version of this paper was published as part of the DVS Proceedings: “Thermal Spray Solutions: Advances in Technology
and Application,” International Thermal Spray Conference, Osaka, Japan, 10–12 May 2004, CD-Rom, DVS-Verlag GmbH, Düsseldorf,
Germany. 相似文献
4.
The isothermal oxidation behavior of Ti-45Al-8Nb and Ti-52Al-8Nb alloys at 900 °C in air was investigated. The early oxidation behaviors were studied by using XPS and AES. And the microstructure and the composition of the oxidation scale were studied by using XRD and SEM. The results show that the oxidation behavior of TiAl alloy is significantly improved by Nb addition. Nb substitutes for Ti in TiO2 as a cation with valence 5, and thus to suppress TiO2 growth. The (Ti,Nb)O2-rich layer is a dense and chemically uniform which is more protective than the TiO2 layer. Nb addition also lowers the critical Al content to form an external alumina. Nb2Al phase is formed in the metallic matrix at the oxide–metal interface on the high Nb containing TiAl alloys. 相似文献
5.
《Scripta materialia》2002,46(9):639-643
The oxidation behavior of Ti–Nb, Ti3Al–Nb and TiAl–Nb (Nb: 0–30 at.%) has been investigated at 1173 K in air. When Nb is in solid solution with TiO2, the addition of Nb can improve the oxidation resistance of the alloys by impeding mass transfer in TiO2. However, Nb decreases the oxidation resistance when the amount of Nb is too high and forms TiNb2O7 or AlNbO4 phases in the scale. 相似文献
6.
采用改进的溶胶-凝胶法,在以水为主要溶剂的反应体系中,控制钛酸四丁酯充分水解、缓慢聚合,在 常压、低温(70℃)的温和条件下制备出稳定的TiO2纳米晶溶胶,并利用TiO2纳米晶溶胶在膨润土表面负载,获得TiO2/膨润土复合光催化材料。采用 X 射线衍射、扫描电镜、比表面积测定等研究手段对样品的结构形貌进行了表征,并考察了其光催化活性。结果表明:较高的水用量有利于TiO2晶体形成,当去离子水:钛酸四丁酯摩尔比大于167:1时,在溶胶体系中出现了锐钛矿型TiO2纳米晶体;TiO2纳米晶主要负载于膨润土表面,并未嵌入到膨润土层间结构,但相对于单一膨润土,TiO2负载显著提高了材料比表面积;当去离子水:钛酸四丁酯摩尔比=192:1时,在紫外光照射下,复合光催化材料表现出最高的光催化活性,对亚甲基蓝的降解率达到93.8%。 相似文献
7.
《Intermetallics》2005,13(9):952-958
The oxidation behavior of gamma alloys was investigated in air and scale spallation was observed. The gamma alloys were superior in oxidation behavior to binary TiAl alloys in both isothermal and cyclic exposure. The mass gain of the alloy with high Nb content was smaller than low Nb alloys at 760 and 815 °C, the difference between them decreased at 870 °C. The improved oxidation resistance of the alloys is attributable to Nb addition resulting from reduced TiO2 growth through the so-called doping effect. Not only the alloys with low Nb but also the high Nb alloys suffered from scale spallation, especially after longer and/or higher temperature exposure. The density of the scale formed on the gamma alloys was found to be about one half of bulk oxide (Al2O3, TiO2) and was comparable to that formed on binary TiAl alloys. The coefficient of the thermal expansion (CTE) of the gamma alloys was larger than that of the oxides and the alloying addition reduced the CTE value of the alloys. Although the Nb addition suppressed the oxide growth and reduced the CTE difference between alloy and oxides, the prevention of the scale spallation could not be attained by single addition of Nb. 相似文献
8.
采用机械合金化+热压工艺制备了NbCr_2/Nb-XMo (X=0,2.5,5.0,7.5,10, at%)合金,研究了合金元素Mo对NbCr_2/Nb合金组织及性能的影响。结果表明:合金元素Mo主要存在于Nb基体中,对合金的物相不产生明显影响,合金仍由Nb固溶体和NbCr_2组成;Mo的添加使得NbCr_2/Nb的相界面处应力增加,导致NbCr_2颗粒中的层错/孪晶的密度增加,并促进了Nb基体中位错的运动,从而使得NbCr_2/Nb合金在保持高强度的同时,具有良好的塑性和韧性。 相似文献
9.
Na LiLi Zhu Wei-De Zhang Yu-Xiang YuWen-Hui Zhang Mei-Fang Hou 《Journal of Alloys and Compounds》2011,509(41):9770-9775
In this work, TiO2 nanorods were prepared by a hydrothermal process and then Bi2MoO6 nanoparticles were deposited onto the TiO2 nanorods by a solvothermal process. The nanostructured Bi2MoO6/TiO2 composites were extensively characterized by X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy and UV-vis diffuse reflectance spectroscopy. The photocatalytic activity of the Bi2MoO6/TiO2 composites was evaluated by degradation of methylene blue. The Bi2MoO6/TiO2 composites exhibit higher catalytic activity than pure Bi2MoO6 and TiO2 for degradation of methylene blue under visible light irradiation (λ > 420 nm). Further investigation revealed that the ratio of Bi2MoO6 to TiO2 in the composites greatly influenced their photocatalytic activity. The experimental results indicated that the composite with Bi2MoO6:TiO2 = 1:3 exhibited the highest photocatalytic activity. The enhancement mechanism of the composite catalysts was also discussed. 相似文献
10.
Mechanical properties and wear rates of Al2O3-13 wt.% TiO2 (AT-13) and Al2O3-43 wt.% TiO2 (AT-43) coatings obtained by flame and atmospheric plasma spraying were studied. The feed stock was either ceramic cords or powders. Results show that the wear resistance of AT-13 coatings is higher than that of AT-43 and it seems that the effect of hardness on wear resistance is more important than that of toughness. Additionally, it was established that, according to conditions used to elaborate coatings and the sliding tribological test chosen, spray processes do not seem to have an important effect on the wear resistance of these coatings. 相似文献
11.
The properties of TiO2 film prepared by titanium tetrachloride were investigated with respect to annealing temperatures in terms of phase change,
crystallite size, and band gap energy. The TiO2 film dried at room temperature exhibited an amorphous phase, while films calcined above 281 and at 990°C displayed anatase
TiO2 and a mixture of anatase and rutile, respectively. The TiO2 film was transformed to an anatase phase through three stages during the annealing processes: (1) removal of water, (2) decomposition
of a peroxo group, and (3) amorphous-anatase phase transformation. It was also found that the bandgap energy of TiO2 film was changed with increasing annealing temperature. This is attributed to the quantum size effect in the range of 475–675°C
and to the formation of rutile phase having lower band gap energy than anatase in the range of 675–990°C. 相似文献
12.
The strategy to perform nanoscale studies of the initial stages of oxidation of TiAl involved first gaining some information on the electronic structure of pure TiO2 surfaces and then on TiAl surfaces before and after oxidation both in low- and high-oxygen potentials. Both materials were studied in atomically-cleaned states generated by repeated sputtering and heating. It was found that the oxygen vacancies created additional defect states in the band gap of stoichiometric TiO2. The results obtained on TiO2 were used as fingerprints to study the oxide nucleation. The results on the initial stages of oxidation of TiAl confirm the nucleation of Ti2O3 islands of nanometer size and monolayer height in a low-oxygen-pressure environment, whilst a TiO2 layer developed in an atmospheric environment. The ledges on atomically-cleaned surfaces usually acted as nucleation sites. 相似文献
13.
《Intermetallics》2015
The phase stability, mechanical properties and electronic structure of C11b and C40 MoSi2 with alloying elements Al, Mg and Ge were systematically investigated using first principles methods. The calculated lattice constants and elastic constants of C11b and C40 MoSi2 are in good agreement with the previous results. It is found that there is a phase transition from C11b to C40 when the concentrations of Al and Mg reach ∼7 at.% and ∼6 at.%, respectively. Based on the elastic constants, the anisotropy, ductility, hardness and melting temperatures are presented for MoSi2 with alloying elements. For C11b, the ductility will be enhanced by increasing the concentrations of Al or Mg. Simultaneously, hardness will be reduced by the increasing of Al or Mg. Ge have a reverse effects. For C40, the ductility is reduced weakly by Al or Mg. In addition, the effects of substitution of Mo by Nb with Si substitution of Si by Al, Mg and Ge are also investigated. Nb and Mg codoping can improve the ductility of MoSi2. Finally, the density of states is used to analysis the effects of alloying elements on the mechanical properties, and the results are in consistent with the predictions based on elastic constants. 相似文献
14.
Xiaoling WeiYin Cao Lei LuHui Yang Xiaodong Shen 《Journal of Alloys and Compounds》2011,509(21):6222-6226
High dense Na-β″-Al2O3 electrolyte materials have been synthesized by solid state reaction with boehmite, magnesia, sodium carbonate and titania as the starting materials. The effects of TiO2 doping percentage on the properties and microstructures of the prepared samples were investigated by X-ray diffraction (XRD), scan electron microscope (SEM), three point bending and ionic conductivity tests. The results indicated that both the relative densities and the phase purities of the samples could effectively improved after doping with TiO2. The proper doping amount of TiO2 was to form the transient liquid phase during the sintering process, which would reduce the steric effect and accelerate the diffusivity. Moreover, the mechanical performance of the obtained sample increased to the value above 280 MPa as the doping amount of TiO2 was larger than 1 wt%. As to the electric properties, if the doping amount was less than 1 wt%, the grain boundary resistivity reduced as the density increased, so the ionic conductivity of the Na-β″-Al2O3 was enhanced obviously. However, when the doping amount was above 1 wt%, the ionic conductivity was deteriorated because of the increased resistivity caused by the broadening grain size. 相似文献
15.
Lichao JiaCongcong Wu Song HanNian Yao Yuanyuan LiZongbao Li Bo Chi Jian PuLi Jian 《Journal of Alloys and Compounds》2011,509(20):6067-6071
Electronic and optical properties of pure, N-doped, Fe-doped and (N, Fe)-codoped anatase TiO2 were evaluated, respectively, by using the density functional theory. The results indicate that the elemental doping narrows the band gap of TiO2 and realize its visible-light response activity; and incorporation of Fe into N-doped TiO2 further increases the photocatalytic activity under visible-light irradiation compared with that of the N-doped TiO2. 相似文献
16.
G.J. Wan P. Yang A.S. Zhao H. Sun Y.X. Leng J.Y. Chen J. Wang Xi Wu 《Surface & coatings technology》2007,201(15):6889-6892
TiO2−x films were synthesized on carbon by plasma-based ion implantation and deposition (PBII-D). Electrochemical behaviors of the prepared films were investigated in phosphate buffer solution (PBS) and fibrinogen containing PBS solution (PBS(Fn)), to probe charge transfer phenomena between TiO2−x film and fibrinogen. Electrochemical impedance spectroscopy (EIS) as well as simulated values of equivalent circuit units including reaction resistance and electric double layer has been obtained, indicating different charge transfer rate occurred across the interfaces. The shape of Mott-Schottky spectroscopy around the rest-open potential indicates that TiO2−x films are typical n-type semiconductor. Donor density results calculated by Mott-Schottky theory show that TiO2−x films exhibit higher donor density in PBS(Fn) than in PBS, indicating charge transfer from fibrinogen to TiO2−x films, and the space charge layers bend lower. 相似文献
17.
Nano-amorphous TiO2 was prepared by a sol-gel method. The results of X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that
the composite electrode material (TiO2-NiO-C) is made of powder with a grain size of 36.2 nm. Doping of nickel and graphite can increase the electrical conductivity
and the specific surface area of nano-amorphous TiO2. The electrochemical properties of TiO2-NiO-C, such as self-discharge, leakage current, and cycle life, were studied using cyclic voltammetry (CV), electrochemical
impedance spectroscopy (EIS), and charge-discharge test. With a charge-discharge current density of 500 mA/g, the specific
capacity of the TiO2-NiO-C composite material reaches 12.88 mAh/g. Also, the expense of capacity is only 3.88% after 500 cycles. The electrochemical
capacitor with the electrode material of TiO2-NiO-C shows excellent capacity and cycling performance. 相似文献
18.
The corrosion behavior of a Nb-modified Ti3Al intermetallic compound containing 11 at.% Nb in a simulated combustion gas with and without deposits of a Na2SO4–NaCl mixture was examined at 600–800°C for times up to four days. In the absence of salt deposits the corrosion rates were rather low and increased only slightly with temperature, producing very thin scales of mixed oxides of Ti, Al, and Nb without sulfides. The presence of the salt deposits produced higher weight gains during an initial stage of one to two days at 600 and 700°C, after which the reaction stopped. A more important and longlasting effect was observed instead at 800°C, when the kinetics of hot corrosion became nearly linear. The scales formed by hot corrosion were complex mixtures of various corrosion products at all temperatures and showed a porous outer region containing a mixture of unreacted salts with oxides (mainly TiO2), an intermediate region of a mixture of variable composition of oxides of the three metals, and a TiO2-rich layer beneath it. At 800°C the scales tended to form a thin, discontinuous Al2O3-rich layer in the middle and contained an additional innermost region presenting a large concentration of sulfur, very likely as Nb and Ti sulfides. The high rate of hot corrosion at 800°C is attributed to the appearance of sulfides in the inner region of the scale and to a more efficient scale fluxing. 相似文献
19.
《Intermetallics》2016
First-principles calculations have been performed to investigate the phase stability, elastic, and thermodynamic properties of Co3(Al,Mo,Nb) with the L12 structure. Calculated elastic constants show that Co3(Al,Mo,Nb) is mechanically stable and possesses intrinsic ductility. It is found that the shear and Young's moduli of Co3(Al,Mo,Nb) are smaller than those of Co3(Al,W). Calculated density of states indicate the existence of covalent-like bonding in Co3(Al,Mo,Nb). Temperature-dependent thermodynamic properties of Co3(Al,Mo,Nb) can be described satisfactorily using the Debye-Grüneisen approach, including entropy, enthalpy, heat capacity and linear thermal expansion coefficient, showing their significant temperature dependences. Furthermore the obtained data can be employed in the modeling of thermodynamic and mechanical properties of Co-based alloys to enable the design of high temperature alloys. 相似文献
20.
A simple process is employed to increase the efficiency of TiO2 photo-catalytic activity, for which the recombination probability of electron–hole pairs is relaxed. Au is selectively deposited on a high-transparency TiO2-anatase thin film on a glass substrate, and then phenylethyl mercaptan (PEM) is chemisorbed onto the selectively covered Au-clusters/TiO2-anatase thin film. The enhancement of the photo-catalytic activity on the PEM/Au-clusters/TiO2-anatase thin film is evaluated via the induced degradation of methylene blue. The results demonstrate that the Au coverage ratio on TiO2-anatase thin film and the photo-catalytic activity of the chemisorbed PEM/Au-clusters/TiO2-anatase are related. The photo-catalytic contribution of PEM/Au-clusters/TiO2-anatase differs from that of Au on a TiO2-anatase thin film. An optimized photo-catalytic system, a composite of PEM/3.8% Au-clusters/TiO2-anatase thin film, is proposed. The efficiency of the PEM/3.8% Au-clusters/TiO2-anatase thin film is 52.1% higher than that of the as-deposited TiO2-anatase thin film. 相似文献