Abstract
The objective of this work was to investigate the effects of anodization parameters on the anatase phase formation of titanium oxide films, which have been grown on both electropolished and non-electropolished titanium surfaces by direct current anodization in 0.25 and 2.5 mol L-1 H3PO4 solutions, respectively, at three anodization times (3, 6 and 12 hours). SEM, Raman spectroscopy and X-ray diffraction techniques revealed the characteristics of anodic films. Films were characterized according to presence of crystalline nuclei of anatase phase on an amorphous matrix. It was found that differences in size, shape and distribution of crystalline grains on anodized surfaces are affected by the type of polishing given to substrates. The particles on electropolished surfaces were grown in well-defined layers following cone-shaped grains. On the other hand, the crystallization phenomenon on non-electropolished substrates has led to the appearance of smaller particle sizes and a larger number of particles distributed along the surface as well.
Highlights
In the last few decades, titanium and its alloys have been widely used in several areas of materials science, and even in biomedicine due to their desirable properties, such as biocompatibility, low density, good corrosion resistance, high mechanical strength, good formability, and on account of not exhibiting ductile-brittle behavior when subjected to low temperatures 1–3.Some of these properties are due to native titanium dioxide film formation after being exposed to a medium containing oxygen
Anodization is an important electrochemical surface modification technique, which consists in growing an oxide film with high adhesion to the substrate which is able to promote an increase in thickness and crystallinity of the passive film . 2,6,7
By analyzing the curves obtained during anodization, it is observed that the current increases gradually at the beginning of anodization until it reaches peak value, i.e. between 3 and 10 mA cm-2, and current density decreases to a value which is close to zero
Summary
In the last few decades, titanium and its alloys have been widely used in several areas of materials science, and even in biomedicine due to their desirable properties, such as biocompatibility, low density, good corrosion resistance, high mechanical strength, good formability, and on account of not exhibiting ductile-brittle behavior when subjected to low temperatures 1–3. Some of these properties are due to native titanium dioxide film formation after being exposed to a medium containing oxygen. Anodization is an important electrochemical surface modification technique, which consists in growing an oxide film with high adhesion to the substrate which is able to promote an increase in thickness and crystallinity of the passive film . 2,6,7
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