Biomedical Engineering Reference
In-Depth Information
release from the material. Results from experiments demonstrate
that electropolishing removes excess of nickel from surface
and enriches it with titanium [45]. Here, it is crucial to know the
functioning surface's behavior, especially the intrinsic properties of
titanium inherited by its alloys, such as self-passivating abilities. The
formation of a stabile surface oxide layer protects the base material
from general corrosion inluence. Research by Trapanier and co-
workers led irst to the conclusion that optimal corrosion and
biocompatibility results can be obtained for thin oxide layer. Further,
it appears that the uniformity of the oxide layer was more important
for material protection, indicating that passivation process of the
surface was mandatory for improvement in corrosion resistance.
Figure 8.28 Potentiodynamic curves in Hank's solution as received,
EP - electropolished, MP - mechanically polished surface of
NiTi samples [50].
Various approaches are used for electrochemical anodization
[11], which is a well-established surface modiication technique
for titanium orthopedic and dental implants. Of course, it is the
most promising research attempt to combine various kinds of
surface modiication techniques. For example, heat and alkali
treatment results in TiO 2 /HA layer formation; the morphology,
microstructure, and particle size presented by research as shown
in Fig. 8.29, were highly similar to that of the human bone apatite
[34].
 
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