Biomedical Engineering Reference
In-Depth Information
Xie and Li investigated the Ti etching with respect to
photoelectrocatalytic application [108]. They have used two
processes done at: low voltages (20-40 V) and long time (6 h)
anodization in aqueous 1M H
2
SO
4
+ 0.3M H
3
PO
4
+ 0.6M H
2
O
2
+ 0.03M HF solution and at low voltage (10-50 V) and short time
(30 min) anodization in aqueous 0.5M H
3
PO
4
+ 0.1M HF solution
plus post-calcination at 450°C for 2 h. The obtained results
could be easily transferred to implant surface modiication. The
results obtained by Xie and Li conirmed that Ti can be successfully
anodized to TiO
2
in both electrolytes at low voltages.
The TiO
2
/Ti ilm prepared at 40 V for 6 h is shown in
Fig. 9.6. The ilm is composed of a multiporous structure with the
aggregated particles on its surface (a). The average size of the
micropores is up to 1 μm. The thickness of this TiO
2
ilm was
determined to be about 4 μm [108]. The TiO
2
/Ti ilm prepared at
30 V for 30 min with post-calcination at 450°C for 2 h is shown
in Fig. 9.7. The nano-structured TiO
2
thin ilm with a cross-linked
multiporous network structure (a) was formed with average size
of individual pores to be about 50 nm and interconnection wall
thickness was around 30 nm. The thickness of this TiO
2
layer was
measured to be 650 nm (b). The anodic oxidation done at higher
voltage is beneicial to achieve a higher degree of TiO
2
crystallization.
The XRD patterns show that all TiO
2
/Ti etched according to irst
process only exhibited an anatase phase (Fig. 9.8). The nano-
structured TiO
2
thin ilm formed at 30 V for 30 min without calcination
has mainly an amorphous structure due to a very short anodizing
time, but after calcination at 450°C for 2 h, a well-crystallized TiO
2
ilm with an anatase-type is formed (Fig. 9.9). The results indicate
that for both long time anodization without further thermal
treatment and a short time anodization with post-calcination, can
successfully form well-crystallized TiO
2
ilms.
Figure 9.6
Top view (a) and (b) cross-sectional images of TiO
2
/Ti
ilm prepared by anodization at 40 V for 6 h [108].
