Biomedical Engineering Reference
In-Depth Information
The hardness (H) and elastic modulus (E) of the plasma-sprayed
monoclinic zirconia measured by nano-indentation are listed in
Table 12.4. For comparison, the 3 mol.% Y
2
O
3
-ZrO
2
coating
composed of the tetragonal phase [129] and 12.8 mol.% CaO-ZrO
2
coating composed of mainly the cubic phase [128] are summarized.
The term H/E represents the degree of elastic response in elastic-
plastic materials [72, 78]. It was taken as a useful indicator of a
given incapacity of materials to absorb impact energy, that is to say,
materials with lower H/E value possess stronger capacity to dissipate
impact energy [73]. Table 12.4 shows that the elastic modulus and
nano-hardness of the plasma-sprayed monoclinic zirconia coating
are 139.72 ± 24.96, and 7.60 ± 1.77 GPa, respectively. In comparison
with the 3 mol.% Y
2
O
3
-ZrO
2
and 12.8 mol.% CaO-ZrO
2
coatings,
the plasma-sprayed monoclinic zirconia coating has the lowest
H/E value, indicating that it was more resistant to exterior energy
than the other two coatings. After Vickers indentation, no obvious
cracks were formed around the impression on the plasma-sprayed
monoclinic zirconia coating surface while spallation was observed
on the 12.8 mol.% CaO-ZrO
2
coating, further indicating that the
plasma sprayed monoclinic coating may have better toughness.
Table 12.4
Elastic modulus (E) and hardness (H) of the zirconia coating
in comparison with 3 mol.% Y
2
O
3
-ZrO
2
[129] and 12.8
mol.% CaO-ZrO [128]
Monoclinic
ZrO
2
coating
3 mol.% Y
2
O
3
-
ZrO
2
coating
12.8 mol.%
CaO-ZrO
2
coating
Phase composition M
T
C + 8.7% M
Elastic modulus E
(GPa)
139.72 ± 24.96 136.41 ± 25.95 178.53 ± 27.31
Hardness H (GPa) 7.60 ± 1.77 9.20 ± 2.98 13.05 ± 2.92
H/E
0.055
0.067
0.073
Note:
M, monoclinic phase; T, tetragonal phase; C, cubic phase.
The SEM micrographs of the osteoblast-like MG63 cells seeded
on the plasma-sprayed monoclinic zirconia coating are displayed
in Fig. 12.2. After seeding for 1 h, the cells on the zirconia coating
exhibit a round morphology (Fig. 12.2a), which is consistent with the
LSCM observation. A number of secretory vesicles are observed on
the surface and many ilopodia extend from the MG63 cells as shown
in Fig. 12.2a. After seeding for 2 h, the cells become larger and latter.
The ilopodia become more elongated and extend to all directions
