Anodization

The study highlights the corrosion behavior of untreated and treated tantalum with addition of trimanganese tetraoxide (Mn3O4) nanoparticles in simulated inflammatory media. The anodic layer was produced on pure tantalum by anodization in electrolytes composed of ammonium fluoride, ethylene glycol, and water. Nanoparticles were deposited uniformly on the surface of the anodized tantalum with the electrophoretic deposition (EPD) method. The results revealed that the anodic/EPD coating possessed more compact microstructure and higher bond strength than the anodic coating. Simulated inflammatory medium was based on phosphatebuffered saline with additions of H2O2 and HCl. Potentiodynamic polarization and electrochemical impedance spectroscopy studies showed that the anodic and Mn3O4 layers protected the tantalum from corroding in an acidic inflammatory condition. Finally, the corrosion protection mechanism of Mn3O4 NPs in inflammatory condition was presented.

Orthopedic implants, such as those made of stainless steel, cobalt (Co)-based alloys and titanium (Ti) alloys, are commonly used to stabilize, protect, improve, replace or regenerate damaged musculoskeletal tissues both anatomically and functionally in millions of bone injury patients. The biggest drawback of these metallic biomaterials is their non-degradability in the body environment. Magnesium (Mg) and magnesium-based alloys are a new generation of degradable implant materials that have attracted great attention in the past 10 years. There are several advantages of magnesium-based alloys for orthopedic application over other metallic biomaterials. First, magnesium is an essential element for many biological activities, including enzymatic reactions, the formation of apatite and bone cell adsorption. Second, their mechanical properties, including density, elastic modulus and compressive yield strength, are much closer to those of natural bone, and, therefore, they can avoid the stress-shielding effect. Third, magnesium alloys can eliminate the necessity of a second surgery to remove permanent bone implants. Recent results show that alloying of magnesium with aluminum (Al), zinc (Zn), calcium (Ca), zirconium (Zr), yttrium (Y) and rare-earth elements can significantly improve its corrosion resistance and mechanical strength. This paper reviews and compares the mechanical properties, corrosion resistance and biocompatibility of currently researched magnesium-based alloys for use in medical implant applications.

Porous titanium implants are widely employed in the orthopaedics field to ensure good bone fixation.
Recently, the use of porous titanium implants has also been investigated in artificial larynx development in a
clinical setting. Such uses necessitate a better understanding of the interaction of soft tissues with porous titanium
structures. Moreover, surface treatments of titanium have been generally evaluated in planar structures,
while the porous titanium implants have complex 3 dimensional (3D) architectures. In this study, the determining
factors for soft tissue integration of 3D porous titanium implants were investigated as a function of
surface treatments via quantification of the interaction of serum proteins and cells with single titanium
microbeads (300–500 μm in diameter). Samples were either acid etched or nanostructured by anodization.
When the samples are used in 3D configuration (porous titanium discs of 2 mm thickness) in vivo (in subcutis
of rats for 2 weeks), a better integration was observed for both anodized and acid etched samples compared
to the non-treated implants. If the implants were also pre-treated with rat serum before implantation, the integration
was further facilitated. In order to understand the underlying reasons for this effect, human fibroblast
cell culture tests under several conditions (directly on beads, beads in suspension, beads encapsulated in
gelatin hydrogels) were conducted to mimic the different interactions of cells with Ti implants in vivo. Physical
characterization showed that surface treatments increased hydrophilicity, protein adsorption and roughness.
Surface treatments also resulted in improved adsorption of serum albumin which in turn facilitated the
adsorption of other proteins such as apolipoprotein as quantified by protein sequencing. The cellular response
to the beads showed considerable difference with respect to the cell culture configuration. When the titanium
microbeads were entrapped in cell-laden gelatin hydrogels, significantly more cells migrated towards the acid
etched beads. In conclusion, the nanoscale surface treatment of 3D porous titanium structures can modulate
in vivo integration by the accumulative effect of the surface treatment on several physical factors such as
protein absorption, surface hydrophilicity and surface roughness. The improved protein adsorption capacity of
the treated implants can be further exploited by a pre-treatment with autologous serum to render the implant
surface more bioactive. Titanium microbeads are a good model system to observe these effects in a 3D
microenvironment and provide a better representation of cellular responses in 3D.

Plasma electrolyte oxidation (PEO) and anodizing coatings were produced on 7075 Al alloy and compared together. Surface and cross section morphology of the coatings were studied by field emission scanning electron microscope. Phase compositions of coatings were analyzed by the X-ray diffraction Technique. Tafel polarization and immersion tests were done in 3.5.%wt NaCl solution to evaluate the corrosion properties of the coatings and substrate. The antibacterial activity of coatings was evaluated against E. coli bacterium. The PEO and anodized coatings had a completely different surface morphology and microstructure. The PEO coating was not affected by substrate surface features. Coatings cross sectional analysis showed that PEO coating had a dense barrier inner layer and a porous outer layer and it was less uniform in thickness than anodized coating. X-ray diffraction patterns of coatings demonstrated that PEO coating is mainly consisted of a crystalline γ-Al2O3 phase, while in the case of anodized coating no crystalline phase was observed which suggested that it composed of an amorphous phase. Corrosion resistance of 7075 Al alloy were improved after both coating treatments but PEO coating exhibited superior corrosion properties compared to anodized coating because of the crystalline barrier layer. Also, the presence of Silicon in PEO coating resulted in better antibacterial activity than anodized coating.

Nanostructured TiO2 thin films with large surface to volume ratio are fabricated from titanium thin films deposited on various substrates employing an anodization technique. The effect of the electrolytes (e.g. HF-containing electrolyte or neutral electrolyte) and substrates (e.g. silicon substrate or silicon carbide substrate) on the microstructure of the anodized thin films are investigated. Nanoporous films on silicon substrates with an average pore diameter of 25 nm and interpore distance of 40 nm are obtained by anodizing in an aqueous HF electrolyte solution after a comprehensive investigation of the anodization conditions. When the anodization is performed in a neutral electrolyte without HF solution, discrete nanotubular thin films are formed. The anodic film on silicon carbide substrate shows a quite different morphology, which exhibits a layered structure after anodization. The nanostructured TiO2 films are characterized using SEM and XRD techniques and their formation conditions are discussed. In addition, a growth mechanism model is presented to explain the formation of different nanostructures.

The present study is focused on tailoring the morphology of TiO2 nanotubes obtained on Ti6Al7Nb alloy and evaluating their electrochemical behavior in simulated body fluid. The presence of the α and β phases on the Ti6Al7Nb alloy leads to a two-scale organization of the nanotubes on the samples - which in turn affects the electrochemical stability. Furthermore, five different types of TiO2 nanotubes were obtained in various electrolytes (e.g. Generation I, a mixture of Generation II and Generation III, Generation III). Electrochemical behavior analysis of all obtained nanotubes morphologies was composed of Tafel plots, cyclic voltammetry and electrochemical impedance spectroscopy and was correlated with morphology data obtained from SEM (nanotubes diameters from top-view and nanotube length from cross-section view). The electrochemical results showed that morphological modifications of the Ti6Al7Nb alloy's surface by electrochemical anodizing have induced changes to the electrochemical behavior of the material, evident in the corrosion rates.

In this study, a self-organized nanotubular titanium dioxide (TiO2) array was successfully produced by anodizing pure titanium in a mixture of glycerol, distilled water (8% vol.), and ammonium fluoride using a dual electrode system. The size control and distribution of the nanopores were performed in a DC voltage range varying from 30 V to 60 V. The diameter of TiO2 nanopores varies from 59 to 128 nm depending on the anodizing voltage. Energy-dispersive X-ray spectroscopy (EDX) analysis reveals that the as-prepared films are essentially composed of TiO2. According to the X-ray diffraction (XRD) and Raman spectroscopy analysis, the nanotubular arrays of TiO2 annealed at 600°C for 2 hours are composed of a phase mixture of anatase and rutile. Mott-Schottky analysis showed that the TiO2 nanotubes are consistent with an n-type semiconductor with a donor density of about 1017 cm-3. Preliminary results on the photocatalytic degradation of a pharmaceutical pollutant showed that the TiO2 na...

Objective: The objective of this study was to investigate the reproducibility, mechanical integrity, surface characteristics and corrosion behavior of nanotubular (NT) titanium oxide arrays in comparison with a novel nano-pitted (NP) anodic film. Methods: Surface treatment processes were developed to grow homogenous NT and NP anodic films on the surface of grade 2 titanium discs and dental implants. The effect of process parameters on the surface characteristics and reproducibility of the anodic films was investigated and optimized. The mechanical integrity of the NT and NP anodic films were investigated by scanning electron microscopy, surface roughness measurement, scratch resistance and screwing tests, while the chemical and physicochemical properties were investigated in corrosion tests, contact angle measurement and X-ray photoelectron spectroscopy (XPS). Results and discussion: The growth of NT anodic films was highly affected by process parameters, especially by temperature, and they were apt to corrosion and exfoliation. In contrast, the anodic growth of NP film showed high reproducibility even on the surface of 3-dimensional screw dental implants and they did not show signs of corrosion and exfoliation. The underlying reason of the difference in the tendency for exfoliation of the NT and NP anodic films is unclear; however the XPS analysis revealed fluorine dopants in a magnitude larger concentration on NT anodic film than on NP surface, which was identified as a possible causative. Concerning other surface characteristics that are supposed to affect the biological behavior of titanium implants, surface roughness values were found to be similar, whereas considerable differences were revealed in the wettability of the NT and NP anodic films. Conclusion: Our findings suggest that the applicability of NT anodic films on the surface of titanium bone implants may be limited because of mechanical considerations. In contrast, it is worth to consider the applicability of nano-pitted anodic films over nanotubular arrays for the enhancement of the biological properties of titanium implants.

Various TiO2 nanotubes on Ti50Zr alloy have been fabricated via a two step anodization method in glycol with 15vol.% H2O and 0.2M NH4F under anodization controlled voltages of 15, 30 and 45V. A new sonication treatment in deionized water with three steps and total sonication time as 1min was performed after the first anodization step in order to remove the oxide layer grown during 2h. The second step of anodization was for 1h and took place at the same conditions. The role of removed layer as a nano-prepatterned surface was evidenced in the formation of highly ordered nanotubular structures and morphological features were analyzed by SEM, AFM and surface wettability. The voltage-controlled anodization leads to various nanoarhitectures, with diameters in between 20 and 80nm. As biological assay, cell culture tests with MG63 cell line originally derived from a human osteosarcoma were performed. A correlation between nanostructure morphological properties as a result of voltage-controlled anodization and cell response was established.

The present study deals with surface modification of Ti6Al4V alloy via anodization technique. The morphology, structure, adhesion and bioactivity of Ti6Al4V alloy after anodization process were investigated in detail. The influence of fluoride content and direct circuit (DC) applied voltage during anodization of Ti6Al4V alloy in a bath with electrolytes composed of ethylene glycol (EG) and ammonium fluoride (NH4F) were considered. It was found that the average pore sizes and length of nanoporous or nanotubes were increasing with the fluoride content and applied voltage. A minimum of 3 wt% of NH4F is required to grow a self-organized nanotube arrays. As the fluoride content was increased to 5 wt%, TiO2 nanotubes with average diameter of 110 nm and 3.4 microm lengths were successfully synthesized. It is noteworthy to point out that the rate of the nanotube formation was increasing up to 9 microm thick bioactive TiO2 nanotubes layer as anodization time was increased to 3 h. Based on th...

This work reports on a simple, robust and scientifically sound method to develop surfaces able to reduce microbial attachment and biofilm development, with possible applications in medicine, dentistry, food processing, or water treatment. Anodic surfaces with cylindrical nanopores 15 to 100 nm in diameter were manufactured and incubated with Escherichia coli ATCC 25922 and Listeria innocua. Surfaces with 15 and 25 nm pore diameters significantly repressed attachment and biofilm formation. Surface–bacteria interaction forces calculated using the extended Derjaguin Landau Verwey-Overbeek (XDLVO) theory indicate that reduction in attachment and biofilm formation is due to a synergy between electrostatic repulsion and surface effective free energy. An attachment study using E. coli K12 strains unable to express appendages also suggests that the small-pore surfaces may inhibit flagella-dependent attachment. These results can have immediate, far-reaching implications and commercial applications, with substantial benefits for human health and life.

The electrochemical behavior of Ti–6Al–4V anodized alloy, material employee as orthopedic implants, was investigated in a Ringer solution at 27 ◦C. The aim of this study was to evaluate the corrosion resistance in an artificial physiological solution In Vitro, through the electrochemical impedance spectroscopy (EIS) technique. The obtained spectra of EIS showed a typical behavior of a stable passive layer, composed of a porous outer layer and a dense, compact inner layer, exhibiting high impedance values at low frequencies, indicated the formation of a highly stable film.

In this study, a self-organized nanotubular titanium dioxide (TiO2) array was successfully produced by anodizing pure titanium in a mixture of glycerol, distilled water (8% vol.), and ammonium fluoride using a dual electrode system. The size control and distribution of the nanopores were performed in a DC voltage range varying from 30 V to 60 V. The diameter of TiO2 nanopores varies from 59 to 128 nm depending on the anodizing voltage. Energy-dispersive X-ray spectroscopy (EDX) analysis reveals that the as-prepared films are essentially composed of TiO2. According to the X-ray diffraction (XRD) and Raman spectroscopy analysis, the nanotubular arrays of TiO2 annealed at 600°C for 2 hours are composed of a phase mixture of anatase and rutile. Mott-Schottky analysis showed that the TiO2 nanotubes are consistent with an n-type semiconductor with a donor density of about 1017 cm-3. Preliminary results on the photocatalytic degradation of a pharmaceutical pollutant showed that the TiO2 na...

In this research, porous plasma electrolyte oxidation (PEO) coatings were prepared on AZ31 magnesium alloys with the aim of investigating how PEO competitive mechanism affects the coating properties. Thickness of the coated layer, surface morphology, phase structure and quantitative information about porosity were analyzed by FE-SEM, XRD and MATLAB software. The result showed that PEO competitive mechanism was influenced by process parameters such as time, current density, conductivity and breaking voltage. It was concluded that the competition between dissolution rate of magnesium alloy and ceramic coating formation, determines the pore size, thickness and porosity of coating, which are of great importance in bone cell interlocking after implantation. Moreover, various phosphate salt solutions were studied in terms of conductivity. It was concluded that, the degree of phosphate hydration and hydrogenation affects the conductivity and pH of electrolyte. Also, hydrogenated phosphate ions, caused the formation of PEO coating layer including non-adhesive compound which prevented plasma sparking.

In the near future, potential water shortages are expected to occur all over the world and this problem will have a significant influence on the availability of water for water-splitting processes, such as photocatalysis and electrolysis, as well as for drinking water. For this reason, it has been suggested that seawater could be used as an alternative for the various