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1.
Anatase titania nanotube arrays were fabricated by means of anodization of Ti foil and annealed at 400 °C in respective CO and N2 gases for 3 h. Electrochemical impendence spectroscopy study showed that CO annealed arrays possessed a noticeably lower charge-transfer resistance as compared with arrays annealed in N2 gas under otherwise the same conditions. TiO2 nanotube arrays annealed in CO possessed much improved lithium ion intercalation capacity and rate capability than N2 annealed samples. At a high charge/discharge current density of 320 mA g−1, the initial discharge capacity in CO annealed arrays was found to be as high as 223 mAh g−1, 30% higher than N2 annealed arrays, ∼164 mAh g−1. After 50 charge/discharge cycles, the discharge capacity in CO annealed arrays remained at ∼179 mAh g−1. The improved intercalation capacity and rate capability could be attributed to the presence of surface defects like Ti-C species and Ti3+ groups with oxygen vacancies, which not only improved the charge-transfer conductivity of the arrays but also possibly promoted phase transition. 相似文献
2.
TiO2/multi-wall carbon nanotube (MWNT) heterojunction arrays were synthesized and immobilized on Si(0 0 1) substrate as photocatalysts for inactivation of Escherichia coli bacteria. The vertically aligned MWNT arrays were grown on ∼5 nm Ni thin film deposited on the Si by using plasma enhanced chemical vapor deposition at 650 °C. Then, the MWNTs were coated by TiO2 using dip-coating sol-gel method. Post annealing of the TiO2/MWNTs at 400 °C resulted in crystallization of the TiO2 coating and formation of Ti-C and Ti-O-C carbonaceous bonds at the heterojunction. The visible light-induced photoinactivation of the bacteria increased from MWNTs to TiO2 to TiO2/MWNTs, in which the bacteria could even slightly breed on the MWNTs. In addition, the TiO2/MWNTs annealed at 400 °C showed a highly improved antibacterial activity than the TiO2/MWNTs annealed at 100 °C. The excellent visible light-induced photocatalytic efficiency of the TiO2/MWNTs/Si film annealed at 400 °C was attributed to formation of the carbonaceous bonds at the heterojunction, in contrast to the 100 °C annealed TiO2/MWNTs/Si sample which had no such effective bonds. 相似文献
3.
A clear ethanol based precursor sol obtained using diethanolamine has been utilized for the deposition of TiO2 films annealed at different temperatures. The influence of annealing temperature on the structural, optical and electrochemical properties of TiO2 thin films has been examined. Diethanolamine stabilizes the precursor sol due to its chelate forming ability with the alkoxides. It reacts as a tridentate ligand with the titanium isopropoxide. The threshold for the onset of crystallization in the films is identified at a temperature of 300 °C. The SEM study on the films elucidates segregation of irregularly shaped features into finer round clusters as a function of annealing temperature. As determined from the AFM study, the roughness parameter in the films has shown an increase with the annealing temperature. Photoluminescence measurements have given an indirect evidence for the presence of stoichiometric titanium oxide in the films. An optimum crystallite size and high ion storage capacity in the 300 °C annealed film has led to its superior electrochromic activity with the transmission modulation and coloration efficiency of the same film being 42% and 8.1 cm2 C−1, respectively at 550 nm. The highest degree of porosity in the 300 °C annealed film as established from the SEM study is also the reason behind its best electrochromic performance. In addition, the 300 °C annealed film also exhibits the fastest coloration switching kinetics. 相似文献
4.
Abdul Latif Ahmad Nur Aimie Abdullah SaniSharif Hussein Sharif Zein 《Ceramics International》2011,37(8):2981-2989
A SrCo0.8Fe0.2O3 impregnated TiO2 membrane (TiO2-SrCo0.8Fe0.2O3 membrane) was successfully prepared using a sol-gel method in combination with a wet impregnation process. The membrane was subjected to a single gas permeance test using oxygen (O2) and nitrogen (N2). The TiO2 membrane was immersed in the SrCo0.8Fe0.2O3 solution, dried and then calcined to affix SrCo0.8Fe0.2O3 into the membrane. The effect of the acid/alkoxide (H+/Ti4+) molar ratio of the TiO2 sol on the TiO2 phase transformation was investigated. The optimal molar ratio was found to be 0.5, which resulted in nanoparticles with a mean size of 5.30 nm after calcination at 400 °C. The effect of calcination temperature on the phase transformation of TiO2 and SrCo0.8Fe0.2O3 was investigated by varying the calcination temperature from 300 to 500 °C. X-ray diffraction spectroscopy (XRD) and Fourier transform infrared (FTIR) analysis confirmed that a calcination temperature of 400 °C was preferable for preparing a TiO2-SrCo0.8Fe0.2O3 membrane with fully crystallized anatase and SrCo0.8Fe0.2O3 phases. The results also showed that polyvinyl alcohol (PVA) and hydroxypropyl cellulose (HPC) were completely removed. Field emission scanning electron microscopy (FESEM) analysis results showed that a crack-free and relatively dense TiO2 membrane (∼0.75 μm thickness) was created with a multiple dip-coating process and calcination at 400 °C. The gas permeation results show that the TiO2 and TiO2-SrCo0.8Fe0.2O3 membranes exhibited high permeances. The TiO2-SrCo0.8Fe0.2O3 membrane developed provided greater O2/N2 selectivity compared to the TiO2 membrane alone. 相似文献
5.
From mixed (anatase and rutile) bulk particles, anatase TiO2 nanotubes are synthesized in this study by an alkaline hydrothermal reaction and a consequent annealing at 300-400 °C. The physical and electrochemical properties of the TiO2 nanotube are investigated for use as an anode active material for lithium-ion batteries. Upon the first discharge-charge sweep and simultaneous impedance measurements at local potentials, this study shows that interfacial resistance decreases significantly when passing lithium ions through a solid electrolyte interface layer at the lithium insertion/deinsertion plateaus of 1.75/2.0 V, corresponding to the redox potentials of anatase TiO2 nanotubes. For an anatase TiO2 nanotube containing minor TiO2(B) phase obtained after annealing at 300 °C, the high-rate capability can be strongly enhanced by an isotropic dispersion of TiO2 nanotubes to yield a discharge capacity higher than 150 mAh g−1, even upon 100 cycles of 10 C-rate discharge-charge operations. This is suitable for use as a high-power anode material for lithium-ion batteries. 相似文献
6.
Ibro Tabakovic Venkateswara Inturi Jeremy Thurn Mark Kief 《Electrochimica acta》2010,55(22):6749-6754
Electrodeposition of Ni1−xFex (x = 0.1-0.9) films was carried out from a chloride plating solution containing saccharin as an organic additive at a constant current density (5 mA/cm2) and a controlled pH of 2.5. X-ray diffraction studies revealed the existence of an fcc, or γ phase, in the range of 10-58 wt.% Fe, a mixed fcc/bcc phase in the range of 59-60 wt.% Fe, and a bcc, or α phase in the range of 64-90 wt.% Fe. The saturation magnetization, Bs, of electrodeposited Ni1−xFex alloys at the room temperature was found to increase with the increase of Fe-content and follows the Slater-Pauling curve, but deviates from as-cast bulk NiFe alloys. The coefficient of thermal expansion, CTE, of electrodeposited alloys at room temperature also deviates from as-cast bulk NiFe alloys. Annealing of α-Ni36Fe64 alloy results in a martensitic α → γ phase transformation, which takes place between 300 and 400 °C. It was demonstrated that thermal treatment above 400 °C was necessary to obtain magnetic and mechanical properties similar to those to conventional Invar alloy. Annealing of α-Ni36Fe64 alloy at 700 °C brings about a decrease of Bs from 1.75 to 0.45 T. By controlling the annealing conditions of α → γ martensitic transformation, it is possible to adjust the CTE of Ni36Fe64 alloy over the broad limits from 2.7 to 8.7 × 10−6/°C. 相似文献
7.
To improve the cathodic performance of olivine-type LiMnPO4, we investigated the optimal annealing conditions for a composite of carbon with cation doping. Nanocrystalline and the cation-doped LiMn1−xMxPO4 (M = Ti, Mg, Zr and x = 0, 0.01, 0.05 and 0.10) was synthesized in aqueous solution using a planetary ball mill. The synthesis was performed at the fairly low temperature of 350 °C to limit particle size. The obtained samples except for the Zr doped one consisted of uniform and nano-sized particles. The performance of LiMnPO4 was much improved by an annealing treatment between 500 and 550 °C with carbon in an inert atmosphere. A small amount of metal-rich phosphide (Mn2P) was detected in the sample annealed at 900 °C. In addition, 1 at.% Mg doping for Fe enhanced the rate capability in our doped samples. The discharge capacity of LiMn0.99Mg0.01PO4/C was 146 mAh/g at 0.1 mA/cm2 and 125 mAh/g even at 2.0 mA/cm2. 相似文献
8.
Synthesis of self-organized mixed oxide nanotubes by sonoelectrochemical anodization of Ti-8Mn alloy
Self ordered arrays of titanium manganese mixed oxide nanotubes were prepared by anodization of Ti8Mn alloy (UNS R56080) under ultrasonication in diluted ethylene glycol containing fluoride. The dimensions of the nanotubes (diameter: 20-100 nm and length: 0.5-2.0 μm) could be tuned by changing the synthesis parameters. The as-anodized nanotubes showed a stoichiometry of (Ti,Mn)O2. Upon annealing at 500 °C in oxygen atmosphere, the nanotubes contained a mixture of anatase + rutile phases of TiO2 and Mn2O3. The composition of the oxide nanotubes was influenced by the chemistry of the phases present in the alloy. More manganese content was observed in the oxide formed on the β-phase than in the oxide layer of α-phase. Anodization in the ultrasonic field increased the kinetics of nanotubular oxide formation and resulted in homogeneous ordering of the nanotubular arrays as compared to the anodization by conventional stirring in the fluoride containing ethylene glycol solution. Whereas, anodization in aqueous acidified fluoride solutions resulted in severe attack of the β-phase and did not show presence of nanotubular oxide structure. 相似文献
9.
Guoqiang Wu Jianwei Zhang Xiaoying Wang Jianjun Liao Hui Xia Sheikh A. Akbar Jianbao Li Shiwei Lin Xiaogan Li Jing Wang 《Ceramics International》2012
Hierarchical structured TiO2 nano-tubes were prepared following a two-step method: the highly ordered uniform TiO2 nanotube arrays were first grown by the conventional electrochemical anodization of the Ti metal sheet followed by mechanical milling of the as-fabricated TiO2 nanotube arrays. The obtained nanotubes with a length around 400 nm and opening diameter ∼100 nm were formed mixed with the spherical TiO2 single crystals with a diameter around 10 nm indicating hierarchical nanostructure. The as-synthesized TiO2 hierarchical nanotubes based resistive-type chemical sensor exhibits good sensitivity to formaldehyde at room temperatures with or without UV-irradiation. The response of the sensor increased almost linearly as a function of the concentration of formaldehyde from 10–50 ppm under UV irradiation. The response of the sensor to different relative humidity and other possible interferents such as ammonia, methanol and alcohol was investigated. The larger response of the sensor to formaldehyde relative to these interferents is suggested to be due to the deeper diffusion of formaldehyde into the TiO2 nanotubes. 相似文献
10.
Yu-Lin Kuo Li-Der LiuSung-En Lin Chia-Hao ChouWeng-Cheng J. Wei 《Journal of the European Ceramic Society》2011,31(16):3119-3125
Colloid processing and subsequent pressure filtration were used to prepare 14.3 mol% TiO2 doped Bi2O3 (Bi12TiO20, 14BTO) as solid oxide fuel cell electrolyte. Materials characterization and electrical behaviors of 14BTO samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and two-point probe DC conductivity. A pure 14BTO with a cubic sillenite single phase was prepared at the sintering process of 850 °C with a high relative sintered density of 96.82%. In situ and batch-type long-term conductivity measurements at 600 °C were carried out to verify the possible reason of degradation. Additional reduction-oxidation tests under CH4 atmosphere by thermogravimetric analysis (TGA) revealed possible application temperature of 14BTO electrolytes below 700 °C. 相似文献
11.
65.9Cu-24.4Ti-9.7TiB2 (wt.%) composite filler was used to join Al2O3 and Ti-6Al-4V alloy. 30 vol.% TiB whiskers were in situ synthesized as reinforcements in joints. Brazing temperature was 890 °C, 910 °C, 930 °C, 950 °C and 970 °C, and the holding time was 0, 5, 10, 20, and 30 min. The microstructure and mechanical properties of brazed joints were analyzed by scanning electron microscope equipped with energy dispersive spectrometer, shear test and nano-indentation test. Results show that reaction layer Ti4(Cu,Al)2O forms at Al2O3/brazing alloy interface. The reaction between TiB2 powders and Ti atoms in brazing alloy brings on in situ synthesizing TiB whiskers in (Ti,Al)2Cu and AlCu2Ti intermetallics. Formation of TiB whiskers minimizes the mismatch of thermal expansion coefficient between Al2O3 and brazing alloy, and makes the ductile-rigid-ductile multiple layer present in joints, which reduces residual stress of joints. The maximum shear strength of joints can reach 143.3 MPa when the brazing temperature is 930 °C, and holding time is 10 min. 相似文献
12.
Single-crystal α-Al2O3 hexagonal flakes with a diameter of about 200 nm and 20 nm in thickness were obtained by mixing different molar ratios of potassium sulfate to boehmite and heating at 1000 °C. Co-doping 1 mol% TiO2 can increase the shape anisotropy of α-Al2O3 hexagonal flakes, increasing the diameter to 400 nm. The effects of potassium sulfate, Fe2O3 and TiO2 on the phase transformation and morphology development of alumina were investigated using X-ray diffraction analysis (XRD), differential thermal analysis (DTA) and transmission electron microscopy (TEM). The results indicate that co-doping potassium sulfate, Fe3+ and Ti4+ can promote γ → α-Al2O3 phase transformation and change the morphology from a vermicular structure into hexagonal platelets. The shape anisotropy of α-Al2O3 hexagonal flakes can be increased by adding TiO2 due to the segregation of Ti4+ ions onto the surfaces of basal planes of α-Al2O3 single crystal particle. 相似文献
13.
This paper studies the preparation of UO2/TiO2 composite ceramic fuel through sol gel-press forming. The research shows that at 1200–1300 °C, UO2/TiO2 composite ceramic grains are small, uniform and compact. Among them, UO2–0.5 wt%TiO2 has the highest density and good mechanical strength at 1250 °C. 相似文献
14.
Lei Yang Miao Zhang Shiwei Shi Jianguo Lv Xueping Song Gang He Zhaoqi Sun 《Nanoscale research letters》2014,9(1):621
Highly ordered TiO2 nanotube array (TN) films were prepared by anodization of titanium foil in a mixed electrolyte solution of glycerin and NH4F and then annealed at 200°C, 400°C, 600°C, and 800°C, respectively. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), water contact angle (WCA), and photoluminescence (PL). It was found that low temperature (below 600°C) has no significant influence on surface morphology, but the diameter of the nanotube increases from 40 to 50 nm with increasing temperature. At 800°C, the nanotube arrays are completely destroyed and only dense rutile film is observed. Samples unannealed and annealed at 200°C are amorphous. At 400°C, anatase phase appears. At 600°C, rutile phase appears. At 800°C, anatase phase changes into rutile phase completely. The wettability of the TN films shows that the WCAs for all samples freshly annealed at different temperatures are about 0°. After the annealed samples have been stored in air for 1 month, the WCAs increase to 130°, 133°, 135°, 141°, and 77°, respectively. Upon ultraviolet (UV) irradiation, they exhibit a significant transition from hydrophobicity to hydrophilicity. Especially, samples unannealed and annealed at 400°C show high photoinduced hydrophilicity. 相似文献
15.
Chia-Ching WuCheng-Fu Yang Yuan-Tai HsiehWen-Ray Chen Chin-Guo KuoHong-Hsin Huang 《Ceramics International》2012,38(1):223-227
TiO2 thin films were prepared by RF magnetron sputtering onto glass substrates and tungsten was deposited onto these thin films (deposition time 15-60 s) to form W-TiO2 bi-layer thin films. The crystal structure, morphology, and transmittance of these TiO2 and W-TiO2 bi-layer thin films were investigated. Amorphous, rutile, and anatase TiO2 phases were observed in the TiO2 and W-TiO2 bi-layer thin films. Tungsten thickness and annealing temperature had large effects on the transmittance of the W-TiO2 thin films. The W-TiO2 bi-layer thin films with a tungsten deposition time of 60 s were annealed at 200 °C-400 °C. The band gap energies of the TiO2 and the non-annealed and annealed W-TiO2 bi-layer thin films were evaluated using (αhν)1/2 versus energy plots, showing that tungsten thickness and annealing temperature had major effects on the transmittance and band gap energy of W-TiO2 bi-layer thin films. 相似文献
16.
The presence of Mg2+- and Fe3+-ions has an effect on the formation of Al2TiO5. Crystalline phases produced under the influence of the heat treatment have been identified in a heated X-ray diffraction chamber in the temperature range of 20–1500 °C. In the presence of Mg2+- and Fe3+-ions transitional phases are formed in the temperature range of 1000–1350 °C during Al2TiO5 formation. The XRD technique was used to identify the crystalline phases formed. On addition of MgO, chemical composition of the transitional phase formed is Mg0.3Al1.4Ti1.3O5, whereas on addition of Fe2O3 we have calculated a Powder Diffraction File card data for the transitional phase. Determination of the lattice parameters of the Al2TiO5 ceramics produced enabled verification of incorporation of Mg2+- or Fe3+-ions into the crystal lattice of Al2TiO5, i.e. the formation of Mg2+- and Fe3+-containing solid solutions. 相似文献
17.
Yonggang Wang Gang Xu Linlin Yang Zhaohui Ren Xiao Wei Wenjian Weng Piyi Du Ge Shen Gaorong Han 《Ceramics International》2009
Bi2Fe4O9 (BFO) nanoparticles were successfully synthesized by a hydrothermal method at a temperature as low as 100 °C. The as-prepared powders, characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), transmission electron microscope (TEM) and physical property measurement system (PPMS), exhibited a pure BFO phase about 100 nm size with uniform sheet-like shape and exhibited an AF order at room temperature. It was found that high alkali concentration and alkali ion Na+ played a key role in the formation of BFO nanoparticles at a low temperature of 100 °C. 相似文献
18.
A new method was proposed to form (Ba0.5Sr0.5)TiO3–Al2O3 composite oxide film on etched aluminum foils. The specimens were covered with (Ba0.5Sr0.5)TiO3 (BST) layer by dip-coating in citrate solution and subsequent heat-treatment under 400–650 °C, finally by anodizing in a hot boracic acid and borate solution. The BST powders heated under different temperatures were characterized by X-ray diffraction (XRD) and the specific capacitance of the coated specimens heat-treated under different temperatures and times was measured. It is found that the specific capacitance increases initially with enhancing the temperature and reaches to maximum at 550 °C, but slightly decreases with the heat-treatment time. The capacitance was increased by about 35% after BST coating. 相似文献
19.
Bo-Ra Kim Hyo-Jin Oh Kang-Seop Yun Sang-Chul Jung Wooseung Kang Sun-Jae Kim 《Progress in Organic Coatings》2013
For an electrochemical water splitting system, titanate nanotubular particles with a thickness of ∼700 nm produced by a hydrothermal process were repetitively coated on fluorine-doped tin oxide (FTO) glass via layer-by-layer self-assembly method. The obtained titanate/FTO films were dipped in aqueous Fe solution, followed by heat treatment for crystallization at 500 °C for 10 min in air. The UV–vis absorbance of the Fe-oxide/titanate/FTO film showed a red-shifted spectrum compared with the TiO2/FTO coated film; this red shift was achieved by the formation of thin hematite-Fe2O3 and anatase-TiO2 phases verified using X-ray diffraction and Raman results. The cyclic voltammetry results of the Fe2O3/TiO2/FTO films showed distinct reversible cycle characteristics with large oxidation–reduction peaks with low onset voltage of I–V characteristics under UV–vis light illumination. The prepared Fe2O3/TiO2/FTO film showed much higher photocurrent densities for more efficient water splitting under UV–vis light illumination than did the Fe2O3/FTO film. Its maximum photocurrent was almost 3.5 times higher than that obtained with Fe2O3/FTO film because of the easy electron collection in the current collector. The large current collection was due to the existence of a TiO2 base layer beneath the Fe2O3 layer. 相似文献
20.
L.M. Wang Ching-Yu ChangShau-Tin Yeh Shinn Wei ChenZi An Peng Shun Chang BairD.S. Lee F.C. LiaoY.K. Kuo 《Ceramics International》2012,38(2):1167-1174
The synthesis and transport properties of n-type thermoelectric oxide (ZnO)mIn2O3 (ZmIO) ceramics prepared by conventional solid-state reaction method have been reported. It is found that the transport properties of ZmIO ceramics are very sensitive to the post-annealing temperature as well as the zinc content m. The resistivity of Z5IO annealed at 1400 °C decreases by more than 2 orders of magnitude in comparison with that of Z5IO annealed at 1200 °C, while the resistivities of Z6IO compounds annealed at 1250 and 1350 °C are more than 3 orders of magnitude larger than that of Z6IO annealed at 1300 °C. All the ZmIO compounds annealed at 1300 °C show electron-type conduction with a lowest resistivity at m = 6. It is suggested that the oxygen defects or vacancies in the InO2 layers play a major role on the carrier scattering mechanism, and the observed temperature-dependent resistivity for Z5IO and Z6IO compounds can be satisfactorily described by the variable-range hopping conduction. Furthermore, it is found that the values of Seebeck coefficient for ZmIO are also very sensitive to the zinc content m. The dimensionless figure of merit of 0.0045 at 300 K for m = 6 has been obtained. 相似文献