Anodic Titanium Oxide Films Research Articles

Effect of Heat Treatment on the Structure and Optical Properties of Porous Anodic Titanium Oxide Films

Effect of Heat Treatment on the Structure and Optical Properties of Porous Anodic Titanium Oxide Films

Electric Resistance Measurements of Anodic Oxide Films on Titanium and Zirconium

Valve metals such as titanium and zirconium can be subjected to anodization to form a thick compact oxide film in fluoride-free electrolytes at room temperature, and the thickness and structure of the film can be controlled by anodization conditions. Although various studies on the formation, characterization and application of anodic titanium oxide film as well as zirconium oxide film have been carried out so far, the electrical resistivity of the anodic oxide films is quite limited. In the present work, we measured electric resistance of the anodic oxide films formed on titanium and zirconium under various anodization conditions, aiming at investigating effects of anodization on electrical resistivity of anodic oxide films.

An Electrochemical Impedance Spectroscopic Study of Oxide Films in Liquid Metal

Electrochemical impedance spectroscopy (EIS) is a powerful technique for the non-destructive, dynamic measurement of electrochemical corrosion behavior in condensed environments, and is a demonstrated, in situ method for monitoring oxide films formed on metal surfaces in liquid metals. To characterize this capability, the impedance properties of three kinds of oxide films (anodic titanium oxide films, deposited Fe2O3 films, and thermally oxidized Fe samples) in liquid metals were examined using the EIS technique. The results show that the impedance response is related to the oxide film thickness and quality. The impedance of thin oxide films ( 200 nm) shows that the oxide film without cracks is stable in LBE and protects the substrate from corrosion. EIS is a promising method for accessing the electrochemical behavior of oxide films on metals and alloys in liquid metals.

Passivity of titanium, part IV: reversible oxygen vacancy generation/annihilation

A simplified Point Defect Model incorporating reversible oxygen vacancy generation/annihilation at the metal/film interface has been used to investigate the impedance of anodized titanium in 0.5 M H2SO4, the oxygen vacancy profile in the anodic titanium oxide film, and the surface oxygen vacancy concentration. This simplified Point Defect Model (PDM), which considers the oxygen vacancy as the only point defect in the film, successfully accounts for the impedance of anodized titanium over the potential range explored. The results indicate that there is a thin region of the non-uniform oxygen vacancy concentration adjacent to the film/solution interface, which has an exponentially decreasing dopant ( $$ {V}_O^{\cdot \cdot } $$ ) concentration. The results of the investigation show that the surface oxygen vacancy concentration normalized to the bulk oxygen vacancy concentration is in the range of 0.05–0.15 and is essentially independent of potential.

Controlled Fabrication of Nanoporous Anodic Titania Films on Ti-6Al-4V Alloy for Enhanced Self-Lubricating Properties by Combining Spark Anodization and Electropulse-Assisted Ultrasonic Rolling

We report the fabrication of self-lubricating nanoporous anodic titania films through spark anodization in an aqueous ammonia sulfate electrolyte on a hardened nanocrystalline layer of Ti-6Al-4V rods after electropulse-assisted ultrasonic surface rolling process (EP-USRP). The spark anodization with an optimum anodizing voltage of 130 V produced sponge-like nanoporous anodic titania films with stable crystalline structure of rutile-phase TiO2, and the EP-USRP resulted in a nanocrystalline layer with a higher surface hardening depth (> 220 µm) through severe plastic deformation. The combinatorial technique resulted in excellent tribological properties, with lower friction coefficient of ~ 0.72 (compared to EP-USRP of ~ 0.80), smoother wear scar with less adhesion and less wear loss (maximum depth of 12 nm, 33.3% lower than the EP-USRP sample). These enhancements are attributed to the synergetic effect of the self-lubricating nanoporous anodic titania films formed by spark anodization (which acted as transition layer and prevented direct contact between the counter materials and the substrate) and the hardened nanocrystalline layer formed by EP-USRP (which slowed down the consumption of the anodic powder).

The passivity of titanium—part III: characterization of the anodic oxide film

The thickness of the anodic titanium oxide film formed on titanium in 0.5 M H2SO4 at 22 °C was measured by ellipsometry, and the Forouhi interband single-layer model was used to analyze the data. The anodizing constant was determined experimentally to be 2.75 nm/V, which is in good agreement with literature data, and indicates that the anodizing constants for barrier layers of anodic oxide films formed on a wide variety of metals and alloys lie within the range of 2.2–3.0 nm/V. Using a value for the polarizability of the barrier layer/solution interface obtained via electrochemical impedance spectroscopy (EIS) together with the anodizing constant, the electric field is estimated to be a voltage-independent 1.82 × 106 V/cm. For the anodic oxide film formed on titanium in 0.5 M H2SO4 solution by galvanostatic polarization, the thickness was maintained to be virtually constant even though the oxygen vacancy concentration (donor density) analyzed by the Mott-Schottky relation varied over a wide range, as a function of the film formation rate (current density), with higher donor densities being found for lower current densities. The increase in the donor density leads to a decrease in the modulus of the impedance.

Passivity of titanium: part II, the defect structure of the anodic oxide film

The kinetic parameters of the formation of the anodic titanium oxide film on Ti in 0.5 M H2SO4 have been determined using potentiostatic polarization, electrochemical impedance spectroscopy (EIS), and the Mott-Schottky analysis (MSA). The findings are interpreted in terms of the point defect model (PDM). The oxygen vacancy is found to be the dominant point defect under all conditions studied with the metal interstitial being the minority defect. From MSA, the oxygen vacancy concentration was found to exponentially decrease from 5.03 × 1020 to 3.91 × 1019 cm−3 as the film formation voltage was increased from 2.24 to 10.24 VSHE. Using a value for the electric field strength of 1.734 × 106 V/cm, as determined by previous modeling with the PDM together with a fitted expression for the donor density and film formation potential, the oxygen vacancy diffusivity was found to be 2.6 × 10−16 cm2/s.

Titania Photonic Crystals with Precise Photonic Band Gap Position via Anodizing with Voltage versus Optical Path Length Modulation.

Photonic crystals based on titanium oxide are promising for optoelectronic applications, for example as components of solar cells and photodetectors. These materials attract great research attention because of the high refractive index of TiO2. One of the promising routes to prepare photonic crystals based on titanium oxide is titanium anodizing at periodically changing voltage or current. However, precise control of the photonic band gap position in anodic titania films is a challenge. To solve this problem, systematic data on the effective refractive index of the porous anodic titanium oxide are required. In this research, we determine quantitatively the dependence of the effective refractive index of porous anodic titanium oxide on the anodizing regime and develop a model which allows one to predict and, therefore, control photonic band gap position in the visible spectrum range with an accuracy better than 98.5%. The prospects of anodic titania photonic crystals implementation as refractive index sensors are demonstrated.

A novel growth strategy of TiO2 anodic films using surface residual stress as driving force

The relationship between residual stress and growth behavior of anodic titanium oxide films (TiO2) was investigated in terms of defect chemistry and the nanocrystalline materials thermodynamic. The results showed that the surface residual stress can be controlled by acting on the duration of the surface mechanical attrition treatment (SMAT). When samples are processed by grinding for 30 min, the residual stress value reaches a maximum of 73.13 MPa, approximately 7.2 times higher than the one obtained with untreated sample. Under these conditions, the thickness of the anodic film was abound 1200 nm, three times that of the TA2 anodic film. Furthermore, the results of electrochemical tests showed that following the surface mechanical attrition treatment, the anodic film show lower density vacancies, higher resistance to the diffusion of Cl−, higher density, and an improved corrosion resistance when compared to TA2. Generally speaking, the growth behavior of the anodic film can be improved by identifying the suitable residual stress.

Micro-electrochemical investigation of the passive behavior of thin anodic titanium oxide films on TiAlV6-4

Micro-electrochemical investigation of the passive behavior of thin anodic titanium oxide films on TiAlV6-4

Anodizations of Al and Ti in NH4F or H3PO4 Solutions and Formation of Porous Anodic Alumina with Special Morphology

Porous anodic alumina (PAA) and anodic TiO2 nanotubes (ATNTs) have been widely investigated for decades. However, their formation mechanism and growth kinetics remain unclear. Here two unconventional and two conventional anodizations of aluminum and titanium are contrasted to overcome this challenge. PAA with special morphology was fabricated in NH4F electrolyte for the first time, which cannot be explained by the popular field-assisted theory. Combining the oxygen bubble mold and the oxide flow model with the dissolution model, a new explanation for the special morphology is presented. In addition, anodic titanium oxide films with plenty of cavities were obtained in H3PO4 electrolyte, which absolutely differ from the general compact films. The cavities in anodic titanium oxide films also result from the oxygen bubbles within the oxide films. The anions in electrolyte (e.g., F–, OH–, PO43–) accumulate, and the anion-contaminated layer (ACL) forms due to the electric field. The ACL plays a decisive role in the generation of the electronic current (Je) and the formation of oxygen bubble mold. Regular ATNTs were obtained as titanium was anodized in NH4F electrolyte. The ACL forms and appropriate Je generates because the dissolution from F– on TiO2 is limited. However, PAA with special morphology was obtained as aluminum was anodized in NH4F electrolyte. Thicker ACL results in the impulse peak of the Je because the dissolution and corrosion from F– on alumina is severe.

Formation mechanism of anodic titanium oxide in mixed electrolytes

The formation mechanism of anodic TiO2 nanotubes (ATNTs) remains mysterious and complicated. Usually, ATNTs are fabricated in pure NH4F electrolytes rather than mixed electrolytes and Ti anodizations are carried out under potentiostatic rather than galvanostatic conditions. In this work, anodizations under the potentiostatic and galvanostatic conditions are conducted. The formation processes of titanium oxide film in different mixed electrolytes are explored in detail. By changing the mass ratios of oxalic acid and ammonium fluoride, different kinds of anodic titanium oxide films are fabricated: the compact anodic titanium oxide (CATO) films, transient-state anodic titanium oxide films and porous films (ATNTs). A distinct transform from CATO films into ATNTs was observed. Cavities within oxide and hemispheric bottoms are found, confirming the presence of oxygen bubble mould. Based on the electronic current and ionic current model, a consistent formation mechanism for three kinds of anodic titanium oxide films in mixed electrolytes is proposed.

Thickness determination of anodic titanium oxide films by electron probe microanalysis

Thin film thickness can be readily associated to the X-ray intensities emitted under electron bombardment. The aim of this work is to develop a method for measuring titanium oxide thicknesses in biomaterials from the X-ray spectra induced in a scanning electron microscope. The oxide layers studied were generated with different anodizing voltages applied in phosphoric and boric acid solution (H3PO4/H3BO3). The oxygen Kα intensity was registered for each sample and related to the corresponding thickness. In order to account for local material alterations, a recalibration is shown to be necessary; Rutherford backscattering spectroscopy was used at this stage. The method is useful for TiO2 thicknesses in the range of interest for dental and orthopedic implants (10–100nm), and it could be extended to greater thicknesses by adequately selecting the electron beam energy.

Effect of the Anodic Titania Layer Thickness on Electrodeposition of Zinc on Ti/TiO2 from Deep Eutectic Solvent

Zinc electrodeposition from a deep eutectic mixture of ZnCl2 and choline chloride/ethylene glycol on titanium covered by an anodic titania film of different thicknesses was studied. It was shown that thin titanium dioxide layers work as high resistive media and the rate of zinc deposition decreases with film thickness. Thicker titania layers (23 nm and higher) have opposite properties and the zinc reduction rate starts gradually increasing with thickness. This happens because at the higher voltage necessary to grow thicker anodic films they become more crystalline and consequently more conductive. There is also evidence that in deep eutectic solvent no dense organic layer forms on the titanium/titania electrodes. The application of an AC signal superimposed on a DC potential only marginally increases the amount of zinc deposited and FTIR measurements did not reveal the formation of any chemical bonds between the film and deep eutectic solvent. Zn deposition onto titanium/titania at −1.6 V is characterized by instantaneous three-dimensional nucleation mechanism, which is independent of the titania thickness.

Semiconductive Behavior of Anodic Titanium Oxide Films with Different Thicknesses

The high corrosion resistance of metal in aqueous environment depends on a thin oxide film formed on its surface. Oxide films on many metals and alloys exhibit the semiconductive property that is considered to be related to corrosion behavior. Therefore elucidating the semiconductive property of oxide film is necessary to understand corrosion resistance of metals and alloys. In order to discuss the semiconductive property of oxide film, in-situ analytical techniques are desired as the denature of the oxide film during evaluation is avoided. Photoelectrochemical response and electrochemical impedance spectroscopy have been applied to study the semiconductive property of oxide film in-situ. In the present work, the semiconductive property of anodic Ti oxide films with different thickness was analyzed using the techniques. Materials were pure Ti discs embedded into epoxy resin. Prior to experiments, its surface was mirror-finished, then ultrasonically cleaned in methanol, ethanol and deionized water for 5 min, successively. The mirror-finished Ti surface was anodized at various potentials ranged from 3 V to 7 V for 60 min in a 0.01 M Na2SO4 solution and phosphate buffer solution, then examined with electrochemical impedance spectroscopy and photoelectrochemical response. For the electrochemical impedance spectroscopy, the capacitance of space charge region was measured and analyzed to estimate donor density and flat band potential. The donor density decreased and the flat band potential increased with increasing film formation potential for all samples. This result indicates that the electronic property of the oxide films is correlated with the film formation potential. In the photoelectrochemical response, a photocurrent exhibited similar transients under all conditions. A spectrum of the photocurrent was separated into two components; a spike photocurrent and a subsequent steady photocurrent. At high measuring potentials, spike charge estimated from the spike photocurrent and the steady photocurrent decrease with increasing the film formation potential. At lower potentials, on the other hand, the spike charge and the steady photocurrent increase with increasing the film formation potential. This result suggests that not only film formation conditions but also measurement conditions influence the photoelectrochemical response. In the presentation, the results will be discussed based on results for electrochemical impedance spectroscopy.

Nanoporous Anodic TiO2-TiO-TiN Composite Films with Enhanced Capacity As Anode Materials for Lithium Ion Batteries

Introduction. Recently, nanoporous or nano-tubular TiO2 films on Ti foils formed by anodization have attracted great attention as promising candidate anode materials for Li-ion batteries (LIBs) to substitute the commercially used graphite. TiO2 materials have a theoretical specific capacity of 330 mAh g-1, which is slightly lower than graphite of 372 mAh g-1. Importantly, TiO2 the operating potential of Li insertion is at ~1.8 V vs Li+/Li, which is much higher than graphite (0.2 V vs. Li+/Li), thus assuring an enhanced battery safety. Especially, nanostructured anodic TiO2 films can provide a high surface area that facilitates the intercalation of Li ions, with limited volume change less than 4% upon lithium insertion/deinsertion, thus improving the safety and lifetime of LIBs. Usually, anodic TiO2 films were formed by anodizing Ti foils in ethylene glycol containing corrosive F- ions and a small amount of water, which may cause environmental concerns. It is highly desirable to explore an aqueous electrolyte with less corrosion and low cost, considering on the practical applications. Therefore, the present study proposed a facile anodizing process to fabricate nanoporous TiO2-TiN composite films on Ti foils by using a nitric-based aqueous electrolyte system without containing corrosive F-ions. The microstructures, chemical composition, and the electrochemical charge-discharge performance as binder-free electrode materials for LIBs were investigated. Experimental. Titanium foils (99.5%, 20 × 40 × 0.1 mm) were used as staring specimens without mechanical or electro-polishing. The specimens, after ultrasonically cleaned for 10 min in acetone and then dried under flowing Ar gas were anodized in various acidic electrolytes containing NH+ and/or NO3 - ions in a constant current density or a voltage mode for 1 – 3 h. Moreover, in order to investigate the effects of crystalline structure of the nanoporous anodic TiO2-TiN films on the electrochemical properties, the anodic specimens were annealed at 423 – 573 K for 1 – 4 h. The morphology, chemical composition, chemical state, and crystalline structure of the anodized specimens before and after annealed were investigated FE-SEM, EDS, TEM (FIB), XRD, and XPS. Moreover, various TiO2-TiN composite films on Ti foils after heating at different temperatures were used as binder-free anodes for LIBs. The charge-discharge performances were investigated using a home-made pouch cell assembled in an Ar-filled glove box. The cathode was utilized with a lithium foil, and the electrolyte solution was made of 1M LiPF6 in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) with a volumetric ratio of 1:1:1. The charge-discharge performances were investigated by using a multi-channel battery test unit in a galvanostatic mode over 1.0 – 3.0 V (vs. Li/Li+) at 303 K at 5 – 50 mA cm−2for 1 – 50 cycles. Results and Discussion. Figure 1a demonstrated a cross-sectional TEM image of as-anodized titania film on Ti foil. The anodic film possessed a nanoporous structure with cylindrical pores of ~Φ50 nm and nano-laminated layers with layer thickness of 250 – 600 nm, indicating a 3D nanostructure. Figure 1b shows the XRD patterns of the anodic titania film before and after annealed at 773 K for 4 h. The as-anodized specimen exhibited a crystalline structure with sharp peaks at 37.1º and 43.3º, close to the (111) and (200) facets of cubic TiO, as well as to TiN. Whereas the specimen after annealed delivered several new peaks that indexed to anatase TiO2. Figure 1c gives the XPS spectra of N1s for the as-anodized specimen. The spectrum for the film surface showed two peaks corresponding to NO3 - and NH+, whereas the spectra after Ar+ sputtering revealed a strong peak close to the binding energy of TiN, thus confirming the formation of TiO2-TiO-TiN composite film. Moreover, it was found that the performance or the specific area capacity of the nanoporous TiO2-TiO-TiN composite films was greatly dependent on the anodizing conditions and the crystalline structure. Especially, the anodized specimen after annealed at 523 K for 1 h exhibited the highest initial discharge capacity of 440 μAh cm-2 upon ~1 μm film, in a charge-discharge test as anode material for LIBs at a constant current density of 5 μA cm-2. Figure 1

Reduction and carbonitriding of anodic titanium oxide film by using a mixture of iron and carbon powders

Reduction and carbonitriding of anodic titanium oxide film by using a mixture of iron and carbon powders

Editorial: LUBMAT 2012 — lubrication, maintenance and tribotechnology

Lubrication ScienceVolume 26, Issue 7-8 p. 447-448 EditorialFree Access Editorial: LUBMAT 2012 — lubrication, maintenance and tribotechnology First published: 10 October 2014 https://doi.org/10.1002/ls.1277Citations: 1AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat LUBMAT 2012 was held in Bilbao, from 6–8 June 2012 in the Euskalduna Palace. LUBMAT was born in 2006, as a collaboration agreement between Jost Institute for Tribotechnology in UK and IK4-TEKNIKER in Eibar, Spain. LUBMAT 2012 contained contributions dealing with lubrication management, tribology, lubricants and additives, special fluids, efficient and operation maintenance, and reliability and sustainability. LUBMAT has been characterised by its effort to reach the biggest number of companies, organising in parallel training courses on 4–5 June, with Congress Collaborators, including the Spanish Association of Maintenance through their review ‘Maintenance’, and the publications F+L Asia, Lubes and Greases, Noria and STLE. Additionally, scientific papers were selected to be published in Lubrication Science, being submitted to a careful expert review. More information about the congress is published under http://www.lubmat.org The first paper selected was related to the physicochemical properties of ionic liquids, specifically the pressure–viscosity behaviour and their relationship with elastohydrodynamic lubrication.1 The second paper refers to the miscibility of ionic liquids in biodegradable esters in order to explore the limitations and challenges when trying to formulate environmentally friendly oils, enhancing their properties with small quantities of ionic liquids.2 The third paper describes the properties of the ionic liquids as hydraulic fluids in comparison with conventional fluids highlighting both tribological and tribocorrosion properties.3 The fourth paper compares the tribocorrosion properties of titanium oxide films produced by plasma electrooxidation and the challenges in using them in dental prosthesis.4 The final paper deals with the friction and wear properties under vacuum and ultrahigh vacuum environment of ionic liquids.5 REFERENCES 1 Fernandez J, Paredes X, Gaciño FM, Comuñas MJP, Pensado AS. Pressure-viscosity behavior and film thickness in elastohydrodynamic regime of lubrication of ionic liquids and other base oils. Lubrication Science 2014; 26(7–8): 449– 462. DOI: 10.1002/ls.1236. Wiley Online LibraryCASWeb of Science®Google Scholar 2 Kronberger M, Pagano F, Pejaković V, Igartua A, Urbistondo E, Kalin M. Miscibility and tribological investigations of ionic liquids in biodegradable esters. Lubrication Science 2014; 26(7–8): 463– 487. DOI: 10.1002/ls.1274. Wiley Online LibraryCASWeb of Science®Google Scholar 3 Regueira T, Lugo L, Fernandez J. Ionic liquids as hydraulic fluids: comparison of several properties with those of conventional oils. Lubrication Science 2014; 26(7–8): 488– 499. DOI: 10.1002/ls.1235. Wiley Online LibraryCASWeb of Science®Google Scholar 4 Alves SA, Bayón R, Igartua A, Saénz de Viteri V, Rocha LA. Tribocorrosion behavior of anodic titanium oxide films produced by plasma electrolytic oxidation for dental implants. Lubrication Science 2014; 26(7–8): 500– 513. DOI: 10.1002/ls.1234. Wiley Online LibraryCASWeb of Science®Google Scholar 5 Totolin V, Conte M, Berriozábal E, Pagano F, Minami I, Doerr N, Brenner J, Igartua A. Tribological investigations of ionic liquids in ultra-high vacuum environment. Lubrication Science 2014; 26(7–8): 514– 524. DOI: 10.1002/ls.1224. Wiley Online LibraryCASWeb of Science®Google Scholar Citing Literature Volume26, Issue7-8Special Issue: LUBMAT 2012 - Lubrication, Maintenance and TribotechnologyNovember-December 2014Pages 447-448 ReferencesRelatedInformation

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.

Thickness determination of electrochemical titanium oxide (Ti/TiO2) formed in HClO4 solutions

Anodic Titanium oxide films were potentiodinamically grown on Ti foil and glass/Ti in 0.010 M HClO4 at 50mVs−1. The current density-potential curves (j−E) showed that the oxide grows according to the physical model for high-field conduction. However, for final potential (Ef) higher than 1.5V vs. Ag/AgCl (sat. KCl) the oxygen evolution reaction becomes more significant, and the formation of bubbles prevented or made more difficult the application of in situ techniques for the simultaneous study of the thickness and optical properties of the anodic layer. We developed a method based on electron probe microanalysis (EPMA) to calculate oxide thickness using ex situ ellipsometry as a reference technique. The normalized intensity of the O Kα peaks was measured for anodic oxides corresponding to Ef values from spontaneous oxide up to 50V, where a linear relationship was observed for a narrower range of final potentials. This behaviour was studied with Monte Carlo simulations. After calibration with ellipsometric results, to take into account sample damage during the electron irradiation, EPMA was applied as a method for thickness determination at Ef ≥ 1.0V. Once the method was established, ex situ thickness determinations became independent of the preparation method of the oxide layer, which represents a comparative advantage against ex situ ellipsometry.