Anodization Of Ti Research Articles

The formation of anatase TiO2 from TiO nanocrystals in sol–gel process

TiO2 anatase has been routinely prepared by a sol–gel method. The purpose of this research is to study if TiO nanocrystals are present which can lead to the formation of anatase. Amorphous powders were first prepared and subsequent thermal annealing in air was used to form anatase. X-ray diffraction and transmission electron microscopy (TEM) were used to study the phase transitions. High-resolution TEM lattice-fringes images were used to identify the TiO nanocrystals. Results show that, similar to vacuum deposition and anodization of Ti reported previously, TiO nanocrystals are present before the formation of anatase.

Ideally ordered porous TiO2 prepared by anodization of pretextured Ti by nanoimprinting process

Ideally ordered anodic porous TiO2 was fabricated through the pretexturing of Ti by nanoimprinting using a metal mold with an ordered array of convexes. The shallow concaves prepared by nanoimprinting acted as initiation sites for hole development during the subsequent anodization and generated ideally hexagonally ordered porous or nanotubular TiO2. The hole interval of the ideally ordered TiO2 could be controlled by changing the pretexturing pattern. This process is a key step towards the preparation of various types of functional devices requiring ideally ordered defect-free hole or pore arrangements.

Improving the Electrochemistry of Anatase for Sodium Ion Batteries by Using Self-Organized TiO2 Nanotubes Prepared by Anodization under Variable Voltage

In order to prepare TiO2 nanotubes of controlled morphology, anodization of titanium under fixed potential or under variable potential was used. Self-organized TiO2 nanotubes with amorphous character are obtained, and after annealing at about 500°C in air atmosphere anatase-phase nanotubes are formed. The resulting areal capacity values in sodium cells are in the order of 1.0-1.5 mAh/cm2, and after 600 discharge-charge cycles the gravimetric capacity vs. Na is about 200 mAh/g [12]. Consequently, the electrochemical behavior of anatase in sodium cell can be competitive in comparison to the behavior in lithium cell. On the other hand, the use of aqueous electrolyte batteries may be an alternative. Using cyclic voltammetry, we have found that self-organized anatase nt-TiO2 electrode in aqueous solution containing lithium (or sodium) ions exhibits reversible redox processes, particularly after optimization of the electrolyte and electrode properties (i.e. anodization of Ti under ramping of voltage).

Self-organization of TiO2 Nanobamboos by Anodization with Deep Eutectic Solvent

We report an unconventional electrochemical spontaneous oscillation of current in Ti anodization by adding deep eutectic solvent (DES) of 2–10% to a fluoride-containing electrolyte; nanobamboos (NBs), i.e., nanotubes decorated with periodic exterior rings, were formed by the DES-assisted anodization. Spontaneous formation of NBs occurred upon application of a constant 20V voltage, together with a self-induced current oscillation that corresponds well to the NB structures. The initial voltage must be higher than a threshold of approximately 14V to induce the self-organization of the NBs. Once a dense layer of TiO2 is formed at 10V or lower, formation of the NBs is suppressed even when a higher voltage (above 15V) is applied. The NBs formed with the spontaneous current oscillation were densely packed (ca. 1.54×1010cm−2) with each NB possessing many rings spaced 20–35nm apart. The thickness of each ring was ca. 10nm. By increasing the DES concentration to 10 wt%, the diameter of the NBs increased from 45 to 110nm and their growth rate increased from 0.16 to 0.3μm/h. The spontaneous current oscillation we observed differs from the conventional electrochemical oscillation because (1) oscillation period is quite long (7min) and (2) the oscillation results in the periodic modulation of TiO2 NBs. The self-organized nanobaoboos were characterized for various anodization conditions, and a mechanism was proposed with the basis of the high conductivity and high viscosity of DES.

TiO2/SnO2 nanotubes for hydrogen generation by photoelectrochemical water splitting

TiO2/SnO2 nanotubes were successfully grown via electrochemical anodization of Ti–Sn 1 μm-thick films deposited onto titanium foil by means of rf sputtering. Two different viscous electrolytes, containing 1 wt% NH4F, were used: ethylene glycol (EG electrolyte), and glycerol + ethylene glycol (GL/EG electrolyte). Self-organized nanotubes prepared in the EG electrolyte exhibited very smooth walls, smaller diameter and were much longer than those obtained in GL/EG. XRD analysis revealed the mixture of anatase with smaller amount of rutile TiO2, however, in the case of EG electrolyte additional phases from the Sn–O system were observed. Contact angle measurements indicated that all the samples were hydrophobic as-prepared and transformed into superhydrophilic upon illumination. Solar-to-hydrogen efficiency was improved by incorporation of Sn up to about 2% which could be attributed to higher photocurrent density reaching 0.2 μA cm−2, longer recombination time 5–15 s and more negative flat band potential VFB = −0.5; −0.6 V.

How voltage dictates anodic TiO2 formation

This study addresses questions regarding the origin of morphology evolution during Ti anodization. The morphology evolution of anodic TiO2 has been investigated. It is found that voltage dictates the formation of etching pits, which in turn governs anodic TiO2 formation, including nanotube diameter and hexagonal features. It is demonstrated that the surface wettability of anodic TiO2 can be tuned from superhydrophilicity to superhydrophobicity by tailoring the microstructure.

Titanium dioxide nanotubes/calcium silicate composite coatings prepared by alternative loop immersion method

Titania nanotube arrays (TNTs) using self-ordering electrochemical anodization have attracted considerable attention for the development of advanced implants in bone therapies. In this study, titania nanotubes/calcium silicate coating on titanium (Ti) was prepared by a two-step procedure involving the fabrication of TNTs arrays by electrochemical anodization of Ti followed by the formation of CaSiO3 coating over the TNTs by a simple process called “alternative loop immersion method (ALIM)”. To study the effect of ALIM, TNT arrays with different crystal structures were produced by repeated cycles of soaking and zinc (Zn) doping. The results showed that the amount of CaSiO3 deposited increased with the number of immersion treatments. The ability of CaSiO3 to induce the formation of apatite layer was excellent and more significant in the case of ALIM treated amorphous TNTs compared to that of anatase TNTs. Moreover, Zn doped CaSiO3 prepared by adding a certain concentration of zinc nitrate into the soaking system exhibited higher chemical stability and enhanced antibacterial activity. In consideration of the potential clinical applications, in vitro bioactivity was confirmed for the TNTs/CaSiO3 composite by simulated body fluid test, and the result showed that CaSiO3 coating significantly enhanced the apatite-forming ability of TNT arrays.

Density of Deep Trap States in Oriented TiO2 Nanotube Arrays

Correlations between the population of deep trap states in an array of TiO2 nanotubes (NT) and the dynamic photocurrent responses under supra-band-gap illumination are investigated. Ordered arrays of TiO2 NT of 10 μm length, 125 nm inner diameter, and 12 nm wall thickness featuring strong anatase character were obtained by anodization of Ti in ethylene glycol solution containing NH4F. Cyclic voltammograms at pH 10 show the characteristic responses for nanostructured TiO2 electrodes, in particular a sharp cathodic peak as the electron density in the film increases. These responses are associated with the population of deep trap states with an average value of 5 × 104 electrons per NT. Dynamic photocurrent measurements clearly show that the characteristic rise time of the photocurrent increases as the potential is increased above the onset region for charging deep trap states. At potentials in which deep trap states are fully depopulated in the dark, photocurrent rise time approaches values just below 1 s, ...

ARTICLE WITHDRAWN] Synthesis and Characterization of Self-Organized Titania Nanotube Arrays by Electrochemical Anodization of Titanium Metal and Ti–6Al–4V Alloy

<b>ARTICLE WITHDRAWN</b>] Synthesis and Characterization of Self-Organized Titania Nanotube Arrays by Electrochemical Anodization of Titanium Metal and Ti–6Al–4V Alloy

TiO2-WO3 Nanotubular Composite Synthesized by Anodization of Simultaneous Multi-Target Sputtered Thin Films Characterized by Laser Ablation ICP-MS

Electrochemical anodization of Ti–W nano-composite thin films deposited on a Si substrate by simultaneous magnetron sputtering of Ti and W resulted in the formation of TiO2–WO3 nanotubular -arrays. A change in the morphology of TiO2–WO3 composite nanotubes with varying percentage of W in Ti–W composite thin films was observed. The oxide film compositions were characterized by XPS and Laser Ablation ICP-MS, of which the latter demonstrated to give a good representation of the overall oxide composition. With a W density of less than or equal to 5.25 x 1018 of W atoms per cm3, the morphology of the composite nanotubes were similar to that of plain TiO2 nanotubes. Whereas with further increase in W density resulted in a nanoporous morphology.

Anodic Titanium Oxide Films: Photoelectrochemical and Tribocorrosion Behavior

Titanium oxide films are fabricated by Ti anodization in orthophosphoric acid-ammonium fluoride electrolytes. On the mechanically polished semi-bright Ti substrates the continuous TiO2 films are formed, whereas ordered nanoporosity is formed on the mirror-like surface of Ti substrate at temperatures of 10–20 °C in the H3PO4 electrolyte with NH4F. The photocurrents and photopotentials are affected by the amount of fluorine in the electrolyte and consequently in the deposit. Tribocorrosion tests were performed in a neutral solution, and changes of open-circuit potential (OCP) as well as electrochemical impedance spectra were recorded with/without 0.4 N load. The rapid changes of OCP can be explained by the passive film abrasion, when oxide film becomes damaged and bare Ti surface is exposed. The wear loss depends on the NH4F concentration in the solution used for TiO2 films fabrication. TiO2 films destroyed during sliding tend to restore within 300–400 s after unloading.

Surface nanoporosity of β-type Ti–25Nb–25Zr alloy for the enhancement of protein adsorption and cell response

This paper outlines a simple method for the electrochemical anodization of β-type Ti–25Nb–25Zr (Ti25Nb25Zr) alloy with a low elastic modulus (approximately 70GPa) to alter its surface topography for bone implant applications. Surface characteristics including topography, roughness, hydrophilicity, and protein adsorption (fibronectin and albumin) were investigated. Human bone marrow mesenchymal stem cell responses, including adhesion, migration, proliferation, and mineralization, were also evaluated. The experimental results demonstrate that the electrochemical anodization process produced a nanoporous surface (pore size <15nm) on Ti25Nb25Zr alloy. This surface nanotopography did not alter the surface roughness or hydrophilicity of the Ti25Nb25Zr alloy but was capable of enhancing biological responses, including protein adsorption, cell adhesion, cell migration, cell proliferation, and cell mineralization. The created surface nanoporosity on β-type Ti25Nb25Zr alloy has a high potential for bone implant applications.

Effect of phosphorous incorporation on crystallinity, morphology, and photocatalytic activity of anodic oxide layer on titanium

This study investigated the effect of P incorporated into an anodic Ti oxide layer in terms of crystallinity, morphology, and photocatalytic activity. For this purpose, Ti substrates were anodized in H3PO4 aqueous solutions of various concentrations, and some of the substrates were subsequently annealed at 723K in air. The electrolyte with higher concentrations increased the amount of P in the Ti oxide layer, thereby inhibiting the thermal crystallization induced by the post-annealing treatment. Areas of exfoliation of the oxide layer could be observed on the surface. The size of these areas decreased with increasing applied voltage, whereas the use of higher concentrations of electrolytes reduced the size of the exfoliated areas. In the absence of annealing, the photocatalytic activity increased with increasing applied voltage; however, in the case of an applied voltage over 250V, the use of high-concentration electrolytes reduced the photocatalytic activity. When anodizing in the H3PO4 electrolytes, the enhancement of the photocatalytic activity by annealing at 723K was minimal, unlike cases using H2SO4 electrolytes.

Superhydrophobic surface of TiO2 hierarchical nanostructures fabricated by Ti anodization

A hierarchical structure of TiO2 with disordered nanowires on top of regular nanotubes was fabricated. With organic monolayers, it showed stronger superhydrophobic properties than regular nanotubes. The surface roughness was further enhanced by removing the dense nanowires layer, resulting in 172° water contact angle. The potential application for aquatic devices was explored by the treated Ti mesh which showed striking floating stability.

Controlled fabrication of porous double-walled TiO2nanotubes via ultraviolet-assisted anodization

Double-walled TiO2 nanotubes with porous wall morphologies are fabricated by anodization under ultraviolet (UV) irradiation. TiO2 formed by anodization of Ti is activated to generate electrons and holes by UV and the anodization process is influenced by the photo-generated charges. As a consequence, morphologies of the fabricated TiO2 nanotubes can be adjusted by controlling the UV illumination. Double-walled TiO2 nanotubes or single-walled nanotubes can be selectively formed by switching on/off the UV illumination. The thickness of the inner and outer walls of the double-walled nanotubes can be tailored by changing the UV power. Due to their larger surface areas compared to single-walled nanotubes, the porous double-walled nanotubes exhibit an enhanced photo-degradation rate for methylene blue (MB). The mechanism of the porous double-walled TiO2 nanotubes is proposed based on the photoactive semiconducting property of the as-growing TiO2 nanotubes under UV.

乙二醇体系中阳极氧化TiO2纳米管制备的研究

采用恒压和原位升压阳极氧化法在含0.3 wt.% NH4F、6 vol.% H2O的乙二醇电解液中，在钛表面分别制备出单层和双层的TiO2纳米管，并通过扫描电子显微镜观察了表面和断面形貌。研究了阳极氧化电压、时间对纳米管管径、管长的影响，初步获得了其相互间的定量关系。结果表明，在实验条件下，纳米管管径和管长随电压增加而增加，在一定电压范围内管径随电压呈线性增长关系，管长在不同电压下表现出不同的增长率；纳米管管长随氧化时间的增加而线性增加，管径则无明显变化。 Single-layer and two-layer TiO2 nanotube arrays were fabricated by anodization of pure Ti in ethylene glycol-based electrolyte containing 0.3 wt.% NH4F and 6 vol.% distilled water in potentiostatic and in-situ voltage up mode respectively. The top-view or cross-sectional morphologies were observed by scanning electron microscope. The effects of applied voltage and anodization time on tube diameter and tube length were studied, as well as their quantitative relationships were preliminarily summarized. The results show that the tube diameter and the length of TiO2 nanotube arrays increase with the applied voltage, and there is a linear dependence between tube diameter and potential in a certain range. The growth rates of the tube length are different at different voltage. The tube length linearly increases with the anodization time, while the tube diameter is little affected by the anodization time.

Fabrication of multilayered TiO2 nanotube arrays and separable nanotube segments

Layered TiO2 nanotube arrays with new structures were prepared by switching the applied voltage of anodization of Ti. Taking advantage of the solvent effect, in an ethylene glycol electrolyte, arrays with thickness-modulated nanotube walls were prepared; in formamide electrolytes, nanotube arrays on 3-D nanopores, arrays with branched structures and arrays with separable nanotube segments were fabricated by designed voltage procedures.

Fabrication of a TiO2 photocatalyst by anodic oxidation of Ti in an acetic acid electrolyte

We anodized Ti substrates in an aqueous acetic acid solution to produce photocatalytic TiO2 films. The TiO2 films were comprised of the anatase phase, but the crystallinity and photocatalytic activity were low, in contrast to films produced by Ti anodization in a sulfuric acid electrolyte. After annealing, the anatase film crystallized and the photocatalytic activity was greatly enhanced. For the anodizations carried out in 0.5 and 2M acetic acid, nonzero current was maintained for the duration of anodization, unlike the other concentrations. We interpret this phenomenon as the layered structure formation from the holes on the substrate surface. Highly crystallized anatase TiO2 therein was thought to mainly contribute to photocatalysis.

A novel self-cleaning, non-enzymatic glucose sensor working under a very low applied potential based on a Pt nanoparticle-decorated TiO2 nanotube array electrode

In this paper, a non-enzymatic amperometric glucose sensor working under a very low applied potential of −0.5V (vs. saturated calomel electrode or SCE) was developed based on a Pt nanoparticle-decorated TiO2 nanotube array (Pt/TiO2 NTA) electrode. A highly ordered TiO2 NTA with a diameter of 200nm was fabricated by anodization of Ti in ethylene glycol containing 0.5wt% NH4F, 10vol% H2O, and 0.9vol% H2SO4. Pt nanoparticles ∼5nm in diameter were uniformly decorated inside the TiO2 nanotubes through ion-exchange reaction with Pt (NH3)4Cl2, followed by reduction with NaBH4. The morphology of the electrode was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The performance of the as-prepared electrode was characterized by cyclic voltammetry and chronoamperometry. The sensor can accurately detect glucose in 0.1M NaOH solution at an applied potential of −0.5V (vs. SCE) in the presence of interferences, such as ascorbic acid and uric acid, with a linear range of 1–15mM and a detection limit of 0.2mM at a signal-to-noise ratio of 3. The Pt/TiO2 synergistic effect shows a good self-cleaning ability. The electrocatalytic ability of the present Pt/TiO2 NTA electrode toward glucose oxidation under a very low applied potential has promising applications in blood glucose measurement and mediator-free anodes for glucose biofuel cells.

Effect of Electrolyte Concentration on the Morphology and Photoelectrochemical Response of Titania Nanotubes Prepared by Electrochemical Anodisation

In this work, the effect of NH4F concentration on the formation, dimensions and photoelectrochemical response of titania nanotubes produced by anodisation of Ti in ethylene glycol has been investigated. The results showed that a minimum amount of 0.25 wt.% NH4F is needed for the formation of uniform and ordered nanotubes in viscous ethylene glycol. Self-organized nanotubes can be synthesized in the concentration range of 0.250.7 wt.%; with a higher fluoride concentration leads to severe etching of the tube tops resulting in a grassy-like appearance. Varying the concentration of NH4F has no effect on the tube diameter and wall thickness. However, nanotubes length increases gradually by increasing the NH4F concentration with preferred growth along the c-axis. Thermal annealing at 500 °C transforms the amorphous nature of as-formed nanotubes into pure anatase phase. Photoelectrochemical response of nanotubes was tested with linear sweep photovoltammetry. It was found that microstructures, crystallinity and geometry of the nanotubes are important factors influencing the photoresponse.