Nanostructured Titania Coatings for Biological Applications: Fabrication and Characterization - Biological and Biomedical Coatings: Processing and Characterization - page 221

10 nm

(a) (b)

100 nm 100 nm

FIGURE 5.16
SEM micrographs of the control (a) and the chemical oxidized pure Ti (b). (From Nanci et al., Surf. Sci. , 600,
4613-4621, 2006. With permission.)

oxide layer is nearly TiO 2 , as suggested by the XPS results. XRD results further show that
the formed layer is mainly amorphous. In fact, oxide layers formed by chemical oxidiza-
tion or electrochemical oxidization are usually amorphous (Nanci et al. 2006).
Variola et al. have produced a nonporous structure in Ti-6Al-4V alloy as shown in Figure
5.17 (Variola et al. 2008). As this alloy consists of two phases, different etching behav-
ior is observed. The β phase tends to form the nanotexture morphology more quickly.
However, after about 2 h of etching, the nanoscaled morphologies in the β and α phase
grains become similar. That is, a uniform nanopit surface is formed. As etching proceeds,
the diameter of pits increases slightly. It has also been demonstrated that the nanoporous

100 nm

SEI 1.5 kV ×10,000 1 µm WD 3.6 mm

FIGURE 5.17
Morphology of nanoporous structure on Ti-6Al-4V alloy fabricated by etching in HNO 3 for electrolyte contain-
ing H 2 SO 4 and H 2 O 2 for 30 min. (From Variola et al., Biomaterials , 29, 1285-1298, 2008. With permission.)