Anodization Of Ti Research Articles

Magnetic-resistive random access memories based on diluted Co-TiO2 nanotubes

In this work, we conducted a study of TiO2 and TiO2:Co nanotubes obtained through the electrochemical anodization of Ti and Ti/Co foils. The presence of the anatase phase and amorphous TiO2 was identified and characterized via XRD and FT-IR measurements. It was possible to establish the formation of oxide-diluted magnetic semiconductors without cobalt binary phases. The morphological properties evidenced the formation of nanotubes with an average size of 163.5 ± 10.12 nm. I–V curves presented SET and RESET processes for sweep cycles, indicating switching properties of the nanotubes. The HRS and LRS were identified as a function of the number of cycles by the determined endurance in the nanotubes. The presence of Co ions in the TiO2 nanotubes contributed to the magnetic dipole moments and the observation of ferromagnetic-like behavior.

New insights into the mechanism causing the loss of anti-corrosion property of superhydrophobic titanium surfaces

In this paper, we provide new insights into the mechanism causing the loss of anti-corrosion property of superhydrophobic titanium (SHP Ti) during potentiodynamic polarization (PDP) measurements. The water contact angle and sliding angle values of the SHP Ti, produced by a facile two-step process: anodizing and coating, were >160° and 6±2°, respectively. The anodization of Ti resulted in randomly distributed micro-clusters of TiO2-xCly covering the Ti surface homogeneously while the low surface energy organic coatings were inhomogeneous in coverage and specifically distributed over the micro-clusters alone of the anodized titanium surface. The electrochemical impedance (EIS) analysis of the SHP CP-Ti samples has shown more than an order of magnitude improvement in their barrier /polarization resistance (Rp) values at ∼ 100 MΩ.cm2 suggesting the effectiveness of the SHP coatings as a barrier against corrosion in neutral chloride environments. However, the Rp values (∼ 10 M Ω.cm2) of the SHP coatings obtained from the PDP analysis were an order of magnitude lower than the Rp values derived from the EIS. SHP CP-Ti samples showed dual passive range behaviour with an initial narrow passive region due to the porous anodized TiO2-xCly layer while the later stage passivity due to the barrier TiO2 layer, where the outer anodized porous TiO2-xCly layer was less effective against corrosion in neutral chloride media. Detailed analysis showed that in PDP, the sample lost its SHP because of the permeation of electrolyte into the hierarchical surface, due to its sensitivity to polarization, owing to the lower thickness of the organic layers. The mechanism involved in the loss of SHP and the limitation of the PDP technique for the corrosion analysis of SHP / organic coatings on metal surfaces is highlighted.

Utilization of glycerol solution for hydrogen production by a combination of photocatalysis and electrolysis processes with Fe-TiO2 nanotubes

A combination of photocatalysis and electrolysis (photoelectrocatalysis) for the simultaneous degradation of glycerol and hydrogen production using Fe-TiO2 nanotubes has been studied. This photocatalyst was synthesized through Ti anodization followed by Fe deposition with Fe(NO3)3 as precursor using the SILAR (successive ionic layer adsorption and reaction) method. The effects of Fe loading (based on the number of SILAR cycles) on TiO2 nanotubes and glycerol concentration were examined. The generated TiO2 nanotubes were 100% anatase phase with crystallite size between 25 and 29 nm. The results of UV-Vis DRS showed that the number of SILAR cycles of Fe dopant determined the magnitude of the decrease in the band gap of photocatalysts up to 2.74 eV, notably lower than a typical value of 3.15 eV associated with TiO2 anatase. FESEM/EDX, TEM, and HRTEM characterizations indicated the formation of neatly arranged TiO2 nanotubes with Fe deposited on the surface. The photoelectrocatalytic process increased the hydrogen produced by up to 5 times compared to a single photocatalytic or electrolysis process. The photocatalyst sample with Fe deposited on TiO2 nanotubes via a SILAR method with 15 cycles outperformed its bare TiO2 nanotube counterpart by producing hydrogen by 2.5 times (405.8 mmol/m2). Glycerol photo-reforming at 10% concentration produced hydrogen 6 times greater than water splitting (0% glycerol).

(Invited) TiO2 Single Nanotubes Decorated with Fe3O4 Nanoparticles for Photocatalytical Environmental Applications

Self-organized TiO2 nanotubes arrays, formed by electrochemical anodization of Ti, have attracted tremendous scientific and technological attention, due to their remarkable properties such as the tunability of dimensions, their directionality, high surface area, high stability, and ability to absorb a significant amount of incident light [1,2].The most widely used electrolyte for the synthesis of TiO2 nanotube layers is based on ethylene glycol containing small amounts of water and fluoride ions. However, nanotubes prepared in these electrolytes present a double-walled structure. The outer wall consists of almost pure TiO2, and the inner wall consists of TiO2 contaminated with carbon and fluoride species [3,4]. In recent years, the selective etching of the inner nanotube wall on Ti layer enabled the synthesis of single-wall nanotubes that showed superior photo-electrochemical performance compared to their double-walled counterparts [5]. An extensive etching also enabled the synthesis of single-tube powders, which can be in turn effectively decorated with Fe3O4 nanoparticles to act as magnetically guidable photocatalysts [6,7].The presentation will discuss the synthesis of these nanotube morphologies and their performance in the photocatalytic degradation of model dye in the liquid phase as well as model drugs that are problematic in wastewaters. We will demonstrate how the photocatalytic performance is influenced by the single nanotubes and single nanotubes decorated with Fe3O4 magnetic particles. Experimental details and photocatalytic results will be presented and discussed.

Porous-Wall Titania Nanotube Array Layers: Preparation and Photocatalytic Response

Electrochemical anodization is already a well-established process, owing to its multiple benefits for creating high-grade titanium dioxide nanotubes with suitable characteristics and tunable shapes. Nevertheless, more research is necessary to fully comprehend the basic phenomena at the anode-electrolyte interface during anodization. In a recent paper, we proposed the use of sawtooth-shaped voltage pulses for Ti anodization, which controls the pivoting point of the balance between the two processes that compete to create nanotubes during a self-organization process: oxide etching and oxidation. Under these conditions, pulsed anodization clearly reveals the history of nanotube growth as recorded in the nanotube morphology. We show that by selecting the suitable electrolyte and electrical discharge settings, a nanoporous structure may be generated as a repeating pattern along the nanotube wall axis. We report the findings in terms of nanotube morphology, crystallinity, surface chemistry, photocatalytic activity, and surface hydrophilicity as they relate to the electrical parameters of electrochemical anodization. Aside from their fundamental relevance, our findings could lead to the development of a novel form of TiO2 nanotube array layer.

Bio-AFM exploits enhanced response of human gingival fibroblasts on TiO2 nanotubular substrates with thin TiO2 coatings

The present work studies anodic TiO2 nanotube (TNT) layers and their surface modifications for enhancing the cell behavior of human gingival fibroblast cells (hGFs) with the contribution of bio-AFM (Atomic Force Microscopy) method. TNT layers, prepared via electrochemical anodization of Ti, with an average tube diameter of 15, 30, and 100 nm, were used as primary substrates for the study. Flat Ti foils were used as reference substrates. Part of the substrates was coated by ultrathin TiO2 coatings (≈ 0.3 nm thin) using Atomic Layer Deposition (ALD). The cell growth and adhesion of hGFs on the TNT layers and Ti foils were compared between ALD coated and uncoated ones. The supplemental coatings altered the surface chemistry of the TNT layers, particularly shading the fluorine and carbon impurities within anodic TiO2, while preserving the original structure and morphology. The presented approach of very mild surface modification remarkably effects the material's biocompatibility and possess great prospect as implant materials. For the first time, the TNT/cell interface was investigated using bio-AFM in terms of Young's modulus, stiffness, cell adhesive force and roughness. Improved biocompatibility was studied in terms of increased cell viability, density, cell cytoskeleton orientation and overall stiffness of the hGFs.

Study on potential gradient in Ti anodization

Porous oxides or nanotubes are obtained through the anodization of valve metal. However, the mechanism of nanotube growth remains unclear. Traditional field-assisted dissolution (FAD) theory has many limitations, such as its inability to explain the connotation of the three stages in the current–time curve. By placing a container between two electrodes, the ions move around the container in a ring in the present study. The potential gradient during anodization was innovatively changed. Finally, the current–time curve obtained during anodization using the new device is quite different from that obtained using conventional anodizing device. This phenomenon is explained by the electronic current and ionic current theory in this paper.

Photoelectrochemical hydrogen generation with CdS/Ti–Si–O composite photoanode

CdS/TiO2 composite photoanode has attracted great attention due to its favorable electronic and optical properties. In this work, nanostructured Si-doped TiO2 photoanodes modified with CdS were fabricated through anodization of Ti–5Si alloy and depositing CdS by successive ionic layer adsorption and reaction (SILAR) process. The composition and morphology, optical properties and photoelectrochemical (PEC) performance of the composite photoanodes were investigated. The CdS/600-TiSiO composite photoanode with donor density of 2.2 × 1019 cm−3 and flat-band potential of −0.215 V exhibited excellent PEC hydrogen generation properties with remarkable photocurrent density (7.86 mA cm−2 at 0 V vs Ag/AgCl), which was 19.15 times and 9.59 times to that of undoped TiO2 photoanode and Ti–Si–O photoanode, respectively. The joint employment of Si-doping and CdS deposition provided an effective method to prepare excellent photocatalysts for PEC hydrogen generation.

Black Ti–Nb–P–O Nanotubes with Bulk-Phase Doping and Surface Oxygen Defective Engineering for High-Performance Symmetric Supercapacitors

Structural modulation with defective engineering designing is a potential approach for the facilitating electrical conductivity and electrochemical activity of Ti-based oxide. Herein, we develop a blackened codoping system (denoted as black Ti–Nb–P–O) with bulk-phase Nb/P codoping and surface oxygen vacancy (Vo) self-doping through in situ anodization of Ti–Nb alloy with one-step phosphorization process. Electrochemical measurements combined with microstructure analysis and density functional theory (DFT) calculations further revealed that the blackened codoping indeed significantly promoted the carrier density, electrical conductivity, diffusion kinetics, and hydrophilicity of electrode materials. The black Ti–Nb–P–O nanotube arrays exhibited a remarkable areal capacitance of 36.60 mF cm–2 at 0.1 mA cm–2, which was approximately 91.5 times higher than that of pristine TiO2 (0.40 mF cm–2). Besides, the electrode realized superior rate capability (80.75% capacitance retention with the scan rate increased from 10 to 100 mV s–1) and impressive cycling stability (84.00% capacitance retention after 5000 cycles). Furthermore, the assembled symmetric supercapacitors owned a wide potential window (2 V) and performed exceptional energy density (4.32 mWh cm–3) at high power density (186.92 mW cm–3). This work involving bulk-phase Nb/P codoping with surface oxygen defective engineering may help provide an effective strategy to improve areal capacitance of Ti-based nanostructures for enhanced electrochemical energy storage.

Enhanced Supercapacitive Properties of Mixed Oxide Nanotubes Grown by Anodization of Ti–Fe Alloys

Like titanium metal, nanotube array films can be grown on Ti alloys by anodization in fluoride‐containing electrolytes. Further, the anodization of Ti alloys provide a unique pathway to dope TiO2 nanotubes with the alloying element. However, the details of anodization behaviors of Ti alloys and the obtained nanotubes for application in supercapacitors remain poorly understood. Herein, three Ti–Fe alloys containing different amounts of Fe element (10, 15, and 20 wt%) are fabricated by using a vacuum arc melting furnace. Their anodization behaviors are systematically investigated. The nanotube array films can be achieved on these alloys, which are composed of TiO2, Fe2O3, and Fe‐doped TiO2. Their electrochemical behaviors are completely different from both the pure TiO2 and the pure Fe2O3. The mixed oxide nanotubes on Ti–15 wt%Fe have the maximum capacitance among the three Ti–Fe alloys, which is 3.75 times higher than that of pure TiO2. Moreover, the mixed oxide electrode exhibits high rate capability and excellent cycling stability with only 5.7% loss in capacitance over 10 000 cycles. The presented results suggest that the alloy anodization is an efficient strategy for enhancing the performance of TiO2 electrode materials for supercapacitors.

Gallium-doped dual micro-nano titanium dental implants towards soft-tissue integration and bactericidal functions

Alongside osseointegration, effective soft-tissue integration (STI) is crucial to the long-term success of dental implants by preventing the ingress of oral pathogens. Nanoscale surface modification of titanium dental implants has shown promise in achieving enhanced bioactivity and antibacterial efficacy. We propose the fabrication of dual micro-nano anisotropic titania nanopores (TNPs) via electrochemical anodization of Ti, followed by incorporating gallium (Ga) towards enhanced antibacterial efficacy. Optimization of Ga chemical functionalization on TNPs was followed by in-depth surface topographical/chemical characterizations and in vitro Ga release. This study revealed that the surface chemistry, hydrophilicity, and topography of the TNPs were altered upon Ga-doping, resulting in the formation of Ga-containing nanoscale particulates firmly bound to TNPs. Further, gingival fibroblast bioactivity was favorably maintained on TNPs and Ga-releasing TNPs. Finally, a human oral salivary biofilm model confirmed the significant antibacterial efficacy of Ga-doped TNPs. Ga-doped dual micro-nano Ti dental implants are suitable as the next generation of bioactive and bactericidal dental implants.

Graphene Oxide Loaded on TiO2-Nanotube-Modified Ti Regulates the Behavior of Human Gingival Fibroblasts.

Surface topography, protein adsorption, and the loading of coating materials can affect soft tissue sealing. Graphene oxide (GO) is a promising candidate for improving material surface functionalization to facilitate soft tissue integration between cells and biomaterials. In this study, TiO2 nanotubes (TNTs) were prepared by the anodization of Ti, and TNT-graphene oxide composites (TNT-GO) were prepared by subsequent electroplating. The aim of this study was to investigate the effect of TNTs and TNT-GO surface modifications on the behavior of human gingival fibroblasts (HGFs). Commercially pure Ti and TNTs were used as the control group, and the TNT-GO surface was used as the experimental group. Scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction were used to perform sample characterization. Cell adhesion, cell proliferation, cell immunofluorescence staining, a wound-healing assay, real-time reverse-transcriptase polymerase chain reaction (RT-PCR), and Western blotting showed that the proliferation, adhesion, migration, and adhesion-related relative gene expression of HGFs on TNT-GO were significantly enhanced compared to the control groups, which may be mediated by the activation of integrin β1 and the MAPK-Erk1/2 pathway. Our findings suggest that the biological reactivity of HGFs can be enhanced by the TNT-GO surface, thereby improving the soft tissue sealing ability.

Fabrication and Electrochemical Performance of TiO2–TiN/Sn–SnO2 Composite Films on Ti for LIB Anodes with High Capacity and Excellent Conductivity

AbstractAccording to the requirements for anode materials of safe and high‐capacity lithium‐ion batteries (LIBs), various Sn/TiO2 and SnO2/TiO2 composite materials have been developed, but no reports have yet combined them by a simple fabrication method. Herein, a novel and simple approach is reported for the fabrication of nanoporous TiO2–TiN/Sn–SnO2 composite films by successive Ti anodization and cathodic hybrid electrodeposition of Sn in a nitric acid‐based aqueous solution containing Sn2+ and/or Sn4+ ions. The conductivity of the anodic TiO2–TiN composite films facilitates the simultaneous electrodeposition of metallic Sn and electrophoretic deposition of SnO2 colloids, both on the surface and inside the nanopores of the film. Notably, the nanoporous structure is preserved, which provides a large surface area. The electrodeposition of Sn–SnO2 nanoparticles on the nanoporous TiO2–TiN film significantly improves the charge transfer and conductivity of the composite film and enhances the discharge capacity to up to 2386.1 µAh cm−2 (approximately sixfold higher than that of the bare matrix film).

Recent Advancements in Morphologies of TiO2 Nanotube Layers and Their Photocatalytic Performance

Self-organized TiO2 nanotubes arrays, formed by electrochemical anodization of Ti, have attracted tremendous scientific and technological attention, due to their remarkable properties such as the tunability of dimensions, their directionality, high surface area, low density, and ability to absorb significant amount of incident light [1,2].The most widely used electrolyte for the synthesis of TiO2 nanotube layers is based on ethylene glycol containing small amounts of water and fluoride ions. However, nanotubes prepared in these electrolytes present a double-walled structure, with the outer wall consisting of almost pure TiO2 and the inner wall consisting of TiO2 contaminated with carbon and fluoride species [3,4]. In the recent years, the selective etching of the inner nanotube wall on Ti layer enabled synthesis of single-wall nanotubes that showed a superior photo-electrochemical performance compared to their double-walled counterparts [5]. An extensive etching enabled also the synthesis of single tube powders, which could be effectively decorated with Fe3O4 nanoparticles to act as magnetically guidable photocatalyst [6,7].The presentation will focus on the influence of all these nanotube morphologies on the photocatalytic degradation in the liquid phase. In particular, we will discuss, how the annealing temperature of single nanotubes influences their photocatalytic performance [7] and how the wall thickness of the single wall nanotubes can be optimized for the best performance [8]. Experimental details and photocatalytic results will be presented and discussed.

Formation of self-organized ZrO2–TiO2 and ZrTiO4–TiO2 nanotube arrays by anodization of Ti–40Zr foil for Cr(VI) removal

In this work, anodic oxidation of Ti-40 wt.% Zr alloy in EG/NH4F/H2O electrolyte was done to produce anodic self-aligned oxide nanotube arrays. The nanotubes were amorphous but upon annealing at 400° C they were crystallized into ZrO2–TiO2 nanotubes and ZrTiO4–TiO2 nanotubes at 600 °C. The nanotubes were used to reduce 60 ppm Cr(VI) ions under sunlight or UV irradiation. 100% removal of Cr(VI) was achieved on ZrTiO4–TiO2 nanotubes after 5 h of exposure to UV light but only 53% removal was obtained on ZrO2–TiO2 nanotubes. The higher photocatalytic activity of the ZrTiO4–TiO2 nanotubes can be related to the presence of the ZrTiO4 phase which has good acid–base properties as well as the junction formation between ZrTiO4 and TiO2 that can further enhance the reduction process.

Electrochemical characteristic assessments toward 2,4,6-trinitrotoluene using anodic TiO2 nanotube arrays

The feasibility of electrochemical detection of 2,4,6-trinitrotoluene (2,4,6-TNT) using TiO2 nanotubes synthesized through electrochemical anodization of Ti was explored. TiO2 nanotube arrays with distinctly different surface features, including an initiation layer and tube wall structures, were prepared, and the efficacy for the electrochemical reduction of 2,4,6-TNT was comparatively evaluated using cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The electrochemical sensing properties of the anodic TiO2 nanotubes were not affected by the surface morphology based on the different anodization conditions. The mechanism governing the mass transfer of 2,4,6-TNT during electrochemical reduction was dominated by diffusion, as determined based on LSV analyses at various scan rates. Importantly, the TiO2 nanotube arrays can distinguish 2,4,6-TNT and cyclotrimethylenetrinitramine (RDX) in mixture solutions of 2,4,6-TNT, RDX, and pentaerythritol tetranitrate (PETN), with four distinct reduction peaks in the voltammogram. Further studies are needed to enhance the efficacy of the TiO2 nanotube arrays for the electrochemical reduction of explosive compounds, where introducing metal dopants, quantum dots, or vacancy engineering are prospectively effective strategies.

Internal anodization of porous Ti to fabricate immobilized TiO2 nanotubes with a high specific surface area

In this paper, internal anodization of porous Ti was performed to fabricate immobilized TiO2 nanotubes with a high specific surface area. The results showed that complete internal anodization of porous Ti was achieved, self-ordered and open-topped TiO2 nanotube arrays were successfully formed within the whole region of porous Ti by applying high anodizing voltage, long oxidation time and enhancing mass transfer. The BET specific surface area of anodized porous Ti reached 16.96 m2/g, which was almost 60 times that before anodic oxidation. Moreover, due to the potential drop and mass transfer, the nanotube growth was larger at the front surface than the back surface, and decreased as they were inward further away from the surface. The anodized porous Ti with a high specific surface area not only benefits the designing of highly active TiO2-based photocatalysts, but also shows great potential for applications in adsorption and electrocatalysis etc.

Unraveling the six stages of the current-time curve and the bilayer nanotubes obtained by one-step anodization of Zr.

The application and growth mechanism of anodic TiO2 nanotubes have been a hot topic in the last ten years, but the formation mechanism of anodic ZrO2 nanotubes has rarely been studied. In one-step constant voltage anodization of Al and Ti, the typical current–time curve has three stages. Moreover, the current–time curves of the three stages can last for 10 min or even 10 hours, resulting in a single layer of nanotubes with the same diameter due to the constant voltage in one-step anodization. However, in this paper, it was found for the first time that the three stages of the current–time curve appeared twice in succession during one-step constant voltage anodization of Zr for only 900 seconds, and bilayer nanotubes with increased diameter were obtained. This six-stage current–time curve cannot be explained by classical field-assisted dissolution and field-assisted flow or stress-driven mechanisms. Here, the formation mechanism and growth kinetics of bilayer ZrO2 nanotubes have been clarified rationally by the theories of ionic current, electronic current and oxygen bubble mold. The interesting results presented in this paper are of great significance for revealing the anodizing process of various metals and the formation mechanism of porous structures.

Anodization of large area Ti: a versatile material for caffeine photodegradation and hydrogen production

Facile, single-step, and scalable fabrication of large-area (∼20 cm2) TiO2 nanostructures (TNS) with promising photocatalytic activity and hydrogen production rate under UVA light was carried out via electrochemical anodization.

Formation process of zirconia nanotubes and porous structures and model of oxygen bubble growth

Preparation and growth mechanism of anodization of Ti and Al has been widely concerned for two decades, but the research on anodic ZrO2 is relatively lacking. In this paper, anodic TiO2 and ZrO2 nanotubes were prepared in glycerol electrolyte containing 0.35 M NH4F and 4 vol% H2O under different anodizing voltages. We had successfully prepared the anodic ZrO2 nanotubes (AZNTs) with a complete top and a “bulb” at the bottom under 60 V, and with the increase of the applied anodizing voltage, the “bulb” cavity also increased. However, under the same anodizing conditions, the surface of anodic TiO2 nanotubes (ATNTs) is a cluster of nano-tip morphology, and the bottom of the ATNTs is a conventional hemisphere shape. In addition, both AZNTs and porous anodic zirconia (PAZ) were found to coexist in the anodic ZrO2 layer prepared at 60 V. Here, we used the oxygen bubble model and ionic current and electronic current theories to analyze the reason of the special morphology. It is confirmed that the porous anodic oxides are actually evolved from nanotubes. In other words, the structure is essentially the same.