Biomedical Engineering Reference
In-Depth Information
100
TiO
2
-NT
Ti 2p
80
O 1s
60
40
20
0
0
20
40
60
80
100
Sputter time (min)
t
= 70 min
Ti
TiO
Ti
Ti
2
O
t
= 40 min
TiO
2
TiO
Ti
t
= 6 min
Ti
2
O
3
TiO
2
TiO
Ti 2p
TiO
2
t
= 2 min
t
= 0 min
465
460
455
470
450
Binding energy (eV)
FIGURE 5.10
XPS depth profile of Ti and O and fine scanning spectra of Ti 2p in titania nanotube acquired by anodization in
electrolyte containing 0.1 m/L NaF, 0.2 mol/L, citric acid, and 1 M/L Na
2
SO
4
at 20 V for 2 h (sputtering rate is
about 20 nm/min referenced to that SiO
2
).
together with a small amount of Ti
2+
Ti2+/TiO as shown in the spectrum. The XPS results sug-
gest that insufficient oxidization takes place during anodization of pure titanium and the
anodized nanotubes consist of not only titania but also other forms of titanium oxides
such as Ti
2
O
3
and TiO.
Crystalline titania nanotubes can be obtained by annealing in oxygen or air. As shown in
Figure 5.11, peaks from the anatase phase begin to appear at about 280°C. At temperatures
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