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Formation of TiO2 Nanotube Layer by Anodization of Titanium in Ethylene Glycol-H2O Electrolyte  [PDF]
Alain Robin, Michele Bernardes de Almeida Ribeiro, Jorge Luiz Rosa, Roberto Zenhei Nakazato, Messias Borges Silva
Journal of Surface Engineered Materials and Advanced Technology (JSEMAT) , 2014, DOI: 10.4236/jsemat.2014.43016

In orthopaedics and orthodontics, the growth of nanotubes of titanium oxide on titanium implants is a promising route for improving the osseointegration. Among the fabrication routes to produce nanotubes, anodization was generally preferred due to its simplicity and low cost. TiO2 nanotubes are formed by the simultaneous anodic reaction and chemical dissolution due to the fluoride species present in the anodization bath. In this work, the formation of TiO2 nanotubes was studied in stirred ethylene glycol-H2O electrolyte (90 - 10 v/v) containing NH4F at room temperature. In order to study the effect of NH4F concentration, voltage and anodization time, and to reduce the number of experiments, a design of experiments (DOE) based on a 2k factorial design with four replicates at the center point was used. The analysis of variance (ANOVA) was used to evaluate the effects of the factors of control and their interactions on the percentage of the titanium surface coated by nanotubes. The dimensions of nanotubes (length and diameter) were also evaluated using field emission gun scanning electron microscopy. The cristallinity and phase composition of the oxide layers was investigated by X-ray diffractometry. The electrochemical behavior of as-received and anodized titanium specimens was studied in Ringer’s solution. The statistical analysis showed that fluoride concentration is the most significant factor. The best condition according to the response surface analysis is the center point (1% NH4F, 20 V, 2 h). The nanotubular oxide layers presented an amorphous structure. Electrochemical tests showed that TiO2 nanotubes coated titanium is less corrosion resistant than

Temporal Evolution of Anodization Current of Porous Silicon Samples  [PDF]
Adriana Gutiérrez, Jairo Giraldo, Mario Enrique Rodríguez-García
Materials Sciences and Applications (MSA) , 2013, DOI: 10.4236/msa.2013.48A005

Temporal evolution of the anodization current of porous silicon samples was studied by means of a model of resistances connected in series that represented the temporal changes of the substrate and of the interface between the substrate and the electrolyte during the porous sample formation process. The porous samples were obtained by means of photoelectrochemical etching of (100) n-type silicon wafers with different resistivity values, all in the range of 1 - 25 Wcm. The samples were formed at room temperature in an electrolytic bath composed by a mixture of hydrofluoric acid (48%) and ethanol having a composition ratio of 1:1 in volume under potentiostatic condition (10 V and 20 V) and an etching time of 2 minutes using back illumination provided by a laser beam with a wavelength of 808 nm.

Anodizing color coded anodized Ti6Al4V medical devices for increasing bone cell functions
Ross AP, Webster TJ
International Journal of Nanomedicine , 2013, DOI: http://dx.doi.org/10.2147/IJN.S36203
Abstract: nodizing color coded anodized Ti6Al4V medical devices for increasing bone cell functions Original Research (879) Total Article Views Authors: Ross AP, Webster TJ Published Date January 2013 Volume 2013:8 Pages 109 - 117 DOI: http://dx.doi.org/10.2147/IJN.S36203 Received: 21 July 2012 Accepted: 17 September 2012 Published: 04 January 2013 Alexandra P Ross, Thomas J Webster School of Engineering and Department of Orthopedics, Brown University, Providence, RI, USA Abstract: Current titanium-based implants are often anodized in sulfuric acid (H2SO4) for color coding purposes. However, a crucial parameter in selecting the material for an orthopedic implant is the degree to which it will integrate into the surrounding bone. Loosening at the bone–implant interface can cause catastrophic failure when motion occurs between the implant and the surrounding bone. Recently, a different anodization process using hydrofluoric acid has been shown to increase bone growth on commercially pure titanium and titanium alloys through the creation of nanotubes. The objective of this study was to compare, for the first time, the influence of anodizing a titanium alloy medical device in sulfuric acid for color coding purposes, as is done in the orthopedic implant industry, followed by anodizing the device in hydrofluoric acid to implement nanotubes. Specifically, Ti6Al4V model implant samples were anodized first with sulfuric acid to create color-coding features, and then with hydrofluoric acid to implement surface features to enhance osteoblast functions. The material surfaces were characterized by visual inspection, scanning electron microscopy, contact angle measurements, and energy dispersive spectroscopy. Human osteoblasts were seeded onto the samples for a series of time points and were measured for adhesion and proliferation. After 1 and 2 weeks, the levels of alkaline phosphatase activity and calcium deposition were measured to assess the long-term differentiation of osteoblasts into the calcium depositing cells. The results showed that anodizing in hydrofluoric acid after anodizing in sulfuric acid partially retains color coding and creates unique surface features to increase osteoblast adhesion, proliferation, alkaline phosphatase activity, and calcium deposition. In this manner, this study provides a viable method to anodize an already color coded, anodized titanium alloy to potentially increase bone growth for numerous implant applications.
Wettability and In Vitro Bioactivity of Doped TiO2 Nanotubes
HUANG Lin, NING Cong-Qin, DING Dong-Yan, BAI Shuo, QIN Rui, LI Ming, MAO Da-Li
无机材料学报 , 2010, DOI: 10.3724/sp.j.1077.2010.09749
Abstract: With low-modulus alloys of Ti35Nb and Ti35Nb15Zr as the anodization substrates, amorphous TiO2 nanotube arrays doped by Nb and Zr elements were fabricated through a surface anodization method. The wettability and in vitro bioactivity of the doped TiO2 nanotubes and undoped nanotubes were investigated. Experimental results indicated that the existence of Nb and Zr elements in the anodic oxides could refine the diameter of the nanotubes and help to grow longer nanotubes. All of the as-anodized nanotubes demonstrated a hydrophobic behavior, which was different from those of the metallic substrate surface. The wettability of the TiO2-based nanotubes varied with the type of the substrate or dopant element. The doping with Nb element could improve the wetting behavior of the TiO2 nanotubes. And simultaneous doping with Nb and Zr elements could have more significant improvement in the wetting behavior. After immersion in simulated body fluids (SBF) the doped TiO2 nanotubes could induce a quick apatite formation. The Nb/Zr doped nanotubes presented quicker apatite formation rate than the Ti-Nb-O nanotubes did at the initial immersion stage. The above findings make it possible to further control or modify the wettability toward either hydrophobic or hydrophilic surfaces, and explore related biological properties of the doped nanotubes.
Size-Tunable Porous Anodic Alumina Nano-Structure for Biosensing  [PDF]
Zhigang Zhu, Luis Garcia-Gancedo, Qiang Liu, Andrew Flewitt, William I. Milne, Francis Moussy
Soft Nanoscience Letters (SNL) , 2011, DOI: 10.4236/snl.2011.13010
Abstract: A porous anodic alumina (PAA) film has been investigated to realise highly-ordered nano-porous structures. A two-step anodization process is used to anodize aluminium into size-controllable aluminium oxide. In this paper, we investigate how anodization parameters affect nano-porous structures, such as voltage and time of pretreatment, anodization voltage and time, pore widening time. The results showed pretreatment is important to obtain a smooth surface for anodizing. The pore size is controllable between 30 and 80 nm, with a linear fit curve. The interpore size is constant at around 95 nm, and the pore densities are between 1010 and 1011 cm–2. The formation of straight vertical walls is crucial if the PAA film is to be subsequently used as the template for the growth of metal nanowire arrays.
Development of Niobium Oxide Coatings on Sand-Blasted Titanium Alloy Dental Implants  [PDF]
Allen C. Mackey, Robert L. Karlinsey, Tien-Mien G. Chu, Meoghan MacPherson, Daniel L. Alge
Materials Sciences and Applications (MSA) , 2012, DOI: 10.4236/msa.2012.35044
Abstract: The purpose of this study was to use scanning electron microscopy (SEM) evaluation to determine the optimal anodizetion conditions needed to generate niobium oxide coatings on titanium alloy dental implant screws. Sand-blasted titanium alloy dental implants were anodized in dilute hydrofluoric acid (HF(aq)) solution using a Sorensen DLM 300-2 power supply. The HF concentration and anodization time were varied and the resulting implant surfaces were evaluated using a Jeol JSM-5310LV Scanning Electron Microscope to determine the ideal anodization conditions. While HF is necessary to facilitate oxide growth, increasing concentrations resulted in proportionate increases in coating delamination. In a similar manner, a minimum anodization time of 1 hour was necessary for oxide growth but longer times produced more delamination especially at higher HF(aq) concentrations. SEM imaging showed that implants anodized for 1 hour in a 0.1% HF(aq) aqueous solution had the best results. Anodization can be used to generate niobium oxide coatings on sand-blasted Ti alloy dental implants by balancing the competing factors of oxide growth and coating delamination. It is believed that these oxide coatings have the potential to improve osseointegration relative to untreated dental implants when evaluated in an in vivo study.
Dependence of Nanotextured Titanium Orthopedic Surfaces on Electrolyte Condition  [PDF]
Sachin M. Bhosle, Radheshyam Tewari, Craig R. Friedrich
Journal of Surface Engineered Materials and Advanced Technology (JSEMAT) , 2016, DOI: 10.4236/jsemat.2016.64015
Abstract: Electrochemical etching of titanium alloy in a fluoride-containing electrolyte results in ordered nanotextured surfaces. The reproducibility of nanotextured surfaces depends on several process parameters, most notably the fluoride ion concentration in the electrolyte. In the present work, electrochemical etching of Ti6Al4V alloy foils in ethylene glycol containing 0.66 wt% NH4F and 2% deionized water was carried out at 60 V for 45 minutes. This paper describes the depletion of fluoride ion concentration and contamination of electrolyte upon reuse. Inductively coupled plasma-optical emission spectroscopy was used to measure the dissolution of metal oxides in the electrolyte during etching. We found increasing concentration of the alloy elements Ti, Al, V contaminated the electrolyte due to repeated reuse of the electrolyte. The results show an appreciable log-linear depletion of fluoride ion concentration resulting in a changed surface morphology, chemical composition and etched volume. This paper provides an important insight to changes in surface morphology and surface chemistry with extended reuse of the etching electrolyte, useful for regulatory approvals.
Electrochemical fabrication of sandwich nanostructures based on anodic alumina
Li, Zhao Jian;Huang, Ke Long;
Journal of the Brazilian Chemical Society , 2007, DOI: 10.1590/S0103-50532007000200024
Abstract: a sandwich porous anodic alumina (paa/al2o3/paa) film was successfully designed and fabricated using the customary two-step anodization approach on both sides of an aluminum foil. the structure of the film was determined with field emission scanning electron microscopy (sem). the sem shows the paa membranes has a well-defined nanostructure. all nanoholes stand symmetrically on both sides of the barrier layer. the average pore diameter reaches 40 nm.
Evaluation of shot peening on the fatigue strength of anodized Ti-6Al-4V alloy
Costa, Midori Yoshikawa Pitanga;Voorwald, Herman Jacobus Cornelis;Pigatin, Walter Luis;Guimar?es, Valdir Alves;Cioffi, Maria Odila Hilário;
Materials Research , 2006, DOI: 10.1590/S1516-14392006000100020
Abstract: the increasingly design requirements for modern engineering applications resulted in the development of new materials with improved mechanical properties. low density, combined with excellent weight/strength ratio as well as corrosion resistance, make the titanium attractive for application in landing gears. fatigue control is a fundamental parameter to be considered in the development of mechanical components. the aim of this research is to analyze the fatigue behavior of anodized ti-6al-4v alloy and the influence of shot peening pre treatment on the experimental data. axial fatigue tests (r = 0.1) were performed, and a significant reduction in the fatigue strength of anodized ti-6al-4v was observed. the shot peening superficial treatment, which objective is to create a compressive residual stress field in the surface layers, showed efficiency to increase the fatigue life of anodized material. experimental data were represented by s-n curves. scanning electron microscopy technique (sem) was used to observe crack origin sites.
Room temperature humidity sensing using nanoporous alumina template fabricated based on hard anodization technique
M Zarei,M Almasi Kashi,A Ramazani,Gh Torkashvand
Iranian Journal of Physics Research , 2010,
Abstract: Humidity sensors are fabricated based on nanoporous alumina, using hard anodization technique. In order to investigate the effect of the anion incorporated in the alumina template during anodization, two different kinds of sensors, wall and barrier layer sensor, with various current densities at 38 V and 44 V anodization voltages are fabricated. The effect of frequency measurement, ranging from 3 to 40 kHz, different applied voltages and relative humidity amplitudes (40% to 90%) are investigated using impedance spectrometry at room temperature. Higher sensitivity is seen for the barrier layer sensors as well as for sensors made at higher anodization current density. It is also found that the sensitivity is inversely proportional to the frequency, and also variation of the applied voltage has no effect on the sensitivity.
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