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6.2.1 Gas PIII&D
Many gas plasmas composed of oxygen, hydrogen, water vapour, and
nitrogen can produce stable nano-topographies on titanium alloys
[19-30]. In comparison with the flat regions and shallow scratches
on the untreated NiTi surface (Fig. 6.2a), Liu et al. produced a
nanostructured surface consisting of fine and uniformly distributed
protrusions by H
O PIII&D (shown in Fig. 6.2b). The thickness of the
surface oxide layer increased from several nanometer to about 40
nm after H
2
O-PIII as shown in the X-ray photoelectron spectroscopy
(XPS) depth profile in Fig. 6.3 [19]. This nano-topographic surface
was produced by bombardment of energetic ions in the water
plasma, namely O
2
+
+
2+
. A similar nanotopography was
obtained on NiTi by nitrogen PIII [20]. By changing the implantation
frequency in N-PIII, the surface roughness could be altered and
different nanoscale morphologies were formed on the NiTi sample.
Hence, the interfacial energy and surface hydrophilicity could be
controlled to influence osteoblast attachment onto the surface.
, OH
, and OH
Figure 6.2
Atomic force microscope (AFM) images: (a) Control sample
and (b) H
O PIII sample. Reprinted from Ref. [19], Copyright
2007, with permission from Elsevier.
2
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