Rapid Breakdown Anodization Research Articles

Erratum Efficient solar energy conversion of TiO2 nanotubes produced by rapid breakdown anodization - a comparison [Phys. Status Solidi RRL 1 , No. 4, 135-137 (2007)

There is an error in the scale bar of the inset of Fig. 1b in the original manuscript. The corrected figure is presented here in Fig. 1. As the originally used figure (see Fig. 2a here) was not very representative for TiO2 nanotubes grown under the described conditions we now provide a more representative picture (Fig. 2b) confirming an average thickness of ∼2.5 µm (as given throughout the paper). No statement or other scientific content of the article is affected by this correction. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Rapid breakdown anodization technique for the synthesis of high aspect ratio and high surface area anatase TiO 2 nanotube powders

Clusters of high aspect ratio, high surface area anatase-TiO 2 nanotubes with a typical nanotube outer diameter of about 18 nm, wall thickness of approximately 5 nm and length of 5–10 μm were synthesized, in powder form, by breakdown anodization of Ti foils in 0.1 M perchloric acid, at 10 V (299 K) and 20 V (∼275 and 299 K). The surface area, morphology, structure and band gap were determined from Brunauer Emmet Teller method, field emmission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman, photoluminescence and diffuse reflectance spectroscopic studies. The tubular morphology and anatase phase were found to be stable up to 773 K and above 773 K anatase phase gradually transformed to rutile phase with disintegration of tubular morphology. At 973 K, complete transformation to rutile phase and disintegration of tubular morphology were observed. The band gap of the as prepared and the annealed samples varied from 3.07 to 2.95 eV with increase in annealing temperature as inferred from photoluminescence and diffuse reflectance studies.

Ultrafast oxide nanotube formation on TiNb, TiZr and TiTa alloys by rapid breakdown anodization

The present work demonstrates ultrafast formation of nanotube bundles on titanium-based alloys, namely TiNb, TiZr and TiTa, by so-called rapid breakdown anodization (RBA). In this process anodization is carried out in chloride–perchlorate based solution for a short period of time. Within seconds, initiation of tube growth appears randomly over the anodized surface, and within a few minutes the entire sample surface can be covered with bundles of nanotubes of several 10 μm in length and some 10 nm in diameter. For all three alloys, the tubes consist of mixtures of oxides of the alloying elements. In every case, the “as formed” oxide tubes are amorphous. By annealing, the oxide nanotube powders can be converted to crystalline mixed oxide in the case of TiNb and TiZr, and a mixture of the individual oxides in the case of TiTa.

Ultrafast Synthesis of Layered Titanate Microspherulite Particles by Electrochemical Spark Discharge Spallation

Recently, a new hydrothermal approach to fabricate titanate materials has attracted much attention. These layered titanate nanomaterials show excellent abilities in ion-exchange, absorption, photoelectronicity, and so on. To satisfy the requirement of different applications, there has been a drastic increase in research to develop new approaches to produce different types of semiconductor oxide nanostructures, especially titanium-based oxides. Up to now, the synthesis of 1D and 2D nanotitanate has been widely investigated with many interesting properties reported. For example, 1D titanate nanotubes, nanowires, nanorods, and 2D titanate nanosheets have been synthesized by hydrothermal, high-temperature oxidation, molten-salt synthesis, and exfoliation methods. Among which hydrothermal synthesis is most widely used. Recent investigations have demonstrated that 3D hierarchical nanostructures could improve the performance of the material in catalysis, biomedical, energy conversion, and water-treatment applications, among others, due to the superior properties derived from the high specific surface area and porous structure. However, it is still challenging to produce 3D hierarchically complex shapes of titanate over multiple scales and the synthetic method is usually not straightforward. Until now, the general approach for preparing hierarchical titanate structures involved the use of sacrificial templates, such as zinc oxide nanotemplate. Alternatively, the template-free methods for generating hierarchical titanates typically employ bottom-up methods, such as reacting agar gel containing a solution of titanium precursor in NH4OH, [5b] two-stage growth through an H2O2-enhanced oxidation process, [5c] twostep synthesis combining hydrolysis and hydrothermal treatment, the chimie douce route by heating TiO2 powder in 15m NaOH solution at reflux, and self-assembly by treating TiCl4 precursor in ethylenediamine at high temperaACHTUNGTRENNUNGtures.[5f] These approaches either take multiple steps or require a long time to ensure complete reaction, for example, the time taken for the reaction between agar gel with Ti precursor and NH4OH is one week. [5b] A simple, fast, and inexpensive method to form 3D hierarchical nanostructures is still lacking and will be of great interest. It is known that a TiO2 porous layer can be formed on a Ti foil surface by mild anodic oxidation in fluoride-containing solutions, rapid breakdown anodization in chloride-/perchlorate-containing electrolytes, or a plasma electrolytic oxidation method. However, to the best of our knowledge, there are no reports using these techniques to generate the titanate materials in powder form, which is traditionally prepared by hydrothermal method. Herein, we report a onestep, template-free method (electrochemical spark discharge spallation) to quickly fabricate layered titanate hierarchical microspherulites (TMSs) with a large surface area (406 mg ) by carefully adjusting the applied electrical spark parameters in the experimental setup (Figure S1 in the Supporting Information). The formation principle of the layered titanate is different from the formation of the TiO2 nanostructures, which include two important steps. First, an ultrahigh anodic reaction oxidizes the Ti surface layer and the formed oxide is immediately broken down by the applied electrical field into the solution in the form of small precipitates. This spallation of the oxide particle is driven by the continuously discharged sparks that simultaneously heat [a] Y. Tang, Dr. Y. Lai, D. Gong, Prof. Z. Dong, Prof. Z. Chen School of Materials Science and Engineering Nanyang Technological University, 50 Nanyang Avenue 639798 (Singapore) Fax: (+65)6790-9081 E-mail : zldong@ntu.edu.sg aszchen@ntu.edu.sg [b] Dr. Y. Lai State Key Laboratory of Physical Chemistry of Solid Surfaces College of Chemistry and Chemical Engineering Xiamen University, Xiamen, 361005 (China) [c] K.-H. Goh, Prof. T.-T. Lim School of Civil and Environmental Engineering Nanyang Technological University, 50 Nanyang Avenue 639798 (Singapore) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201000330.

Lithium Ion Insertion in Titania Nanotube Powders Synthesized by Rapid Breakdown Anodization

Titania nanotubes are synthesized via rapid breakdown anodization and their lithium insertion properties are investigated. Anodization of Ti thin foil in perchloric acid produces TiO 2 nanotube powders in less than 30 min. Annealing of the synthesized TiO 2 nanotubes results in anatase and rutile phases from the originally amorphous phase. The lithium insertion performance of the TiO 2 nanotube is strongly dependent on the annealing condition. Due to its simplicity and short time for synthesis, rapid breakdown anodization can be a viable option to produce TiO 2 nanotubes for lithium ion battery applications.

A Novel Method for Synthesis of Titania Nanotube Powders using Rapid Breakdown Anodization

The present paper describes a new method utilizing rapid anodization to quickly synthesize high-quality, high aspect ratio, robust titanium dioxide nanotube powders. TiO2 nanotube powders, with a typical nanotube outer diameter of approximately 40 nm, wall thickness of approximately 8−15 nm, and length of about 10−35 μm, were synthesized by potentiostatic rapid breakdown anodization of titanium foils in aqueous electrolytes of 0.3 M NaCl or 0.1 M HClO4 under an applied potential of 20 V. High reactivity and ultrahigh reaction rate are cornerstones responsible for periodic release of TiO2 nanotubes into solution and formation of a white precipitate of TiO2 nanotubes. The reaction yield is approximately 4−6 g in less than 3 h, and the approximate cost of the material is $3.50/g, based on the laboratory-scale production. Various characterization techniques, including FESEM, HRTEM, EDX, XRD, XPS, FT-IR, UV−visible diffuse-reflectance, and N2 adsorption, have been used to probe morphology, microstructure, crys...

Self-organized Anodic TiO2-nanotubes in Fluoride Free Electrolytes

The conventional approach for the formation of highly self-organized nanotube layers is based on anodization of titanium in fluoride containing electrolytes. In the present work we demonstrate that also chloride ions in a suitable organic electrolyte can be used to grow organized nanotube layers. The results show, that under specific electrochemical conditions the growth process can change from a previously reported rapid breakdown anodization mechanism (that leads to disordered nanotube bundles) to a self-organized nanotubular growth mechanism. Under these conditions the nanotubes exhibit the key characteristics of self-ordered tubes (closed tube bottoms, regular dimple structures on the metallic substrate and a linear dependence of the tube diameter on the applied potential).

Efficient solar energy conversion using TiO2 nanotubes produced by rapid breakdown anodization – a comparison

AbstractWe report on dye‐sensitization of different TiO2 nanotube layers, their photoelectrochemical response and their efficiency for solar energy conversion. The tubes compared in this study were either grown by controlled Ti anodization in fluoride containing electrolytes or by rapid breakdown anodization (RBA) of Ti in fluoride free electrolytes. After converting the different tube layers to anatase and sensitizing with Ru‐dye (N719), clearly layers consisting of RBA‐NTs show a significantly higher photoresponse and conversion efficiencies than tubes formed under self‐ordering conditions. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)