Biomedical Engineering Reference
In-Depth Information
Karpagavalli et al.
[47]
studied the corrosion behavior and biocompatibility of nanostructured TiO
2
film on Ti6Al4V. They found that nano-TiO
2
coated Ti6Al4V showed a better corrosion resistance
in simulated biofluid than uncoated Ti6Al4V. Furthermore, Nikita et al
.
[48]
also addressed that the
TiO
2
nanoparticle coatings increased the thickness of the pre-existing oxide layer on the Ti6Al4V
surface, serving to improve the bioimplant corrosion resistance. Thus, suggesting that nano-implants
prepared by various technologies will exhibit a different corrosion resistance.
In this section, the behaviors of TiO
2
nanoparticles-coated Ti6Al4V implant in simulated biofluids
will be mainly discussed.
9.2.1
Preparation of the Ti6Al4V Electrode
The Ti6Al4V alloys were used to prepare the samples, which was polished with sand paper and fine
polishing pads, respectively. A titanium wire was spot welded at one end of the Ti electrode. Then, the
total surface of the electrode was coated with an insulating (epoxy) material leaving only the electrode
surface exposed. The coated electrode was thoroughly rinsed by distilled water and left for 24 h to com-
pletely dry.
9.2.2
TiO
2
Nanoparticles Coating
A compound was formed by mixing together 1.2 g of TiO
2
, 0.4 ml of distilled water, 0.02 ml of
Triton-X100, and 0.04 ml of acetyl acetone. Then, in order to obtain a 10% (mass) of TiO
2
aqueous
colloidal suspension, the compound was diluted in deionized water. The suspension was sonicated for
30 min. Then spin coated 6 times on the Ti6Al4V substrate by spin coating. After each spin coating, the
sample was allowed to air dry for 30 s. Finally, the sample was heat-treated in air at 550°C.
9.3
CHARACTERIZATION TECHNIQUES
Presently, a variety of instrumental analysis techniques were applied to access the corrosion phenom-
ena. For example, microscopy techniques include scanning electron microscopy (SEM)
[49]
, atomic
force microscope (AFM)
[50]
, confocal laser scanning microscopy (CLSM), scanning Auger micro-
probe, and X-ray diffraction (XRD)
[51]
.
9.3.1
SEM
Typical SEM micrographs of TiO
2
deposited on Ti6Al4V substrates under different deposition cur-
rents, before and after annealing at 550°C, are shown in
Figure 9.1
. The amorphous particles and
nonuniform clumps were observed before heat treatment (
Figure 9.1A and C
). The agglomeration
of the particles resulted in the formation of clusters. However, after annealing at 550°C, bricklike
crystallites were observed (
Figure 9.1B and D
). The SEM micrograph of as-deposited TiO
2
(
Figure
9.1A
) revealed that the mean particle size of TiO
2
is in the nanometer level (~30-50 nm). It has found
that the TiO
2
crystallite size has been greatly increased during crystallization, a higher crystallite size
after thermal annealing than before heat treatment. The particle size was found to have increased in
size due to the thermal annealing. Moreover, the applied deposition current density can also affect the
particle size.
Figure 9.1A, C, E, and F
shows that when the applied deposition current density was
increased, the agglomeration phenomenon increased.
