Biomedical Engineering Reference
In-Depth Information
cracks deriving from the decomposition reaction of HA phases and
the difference of sintering shrinkages between Ti and HA, which can
promote the sintering densiication and improve the mechanical
properties of Ti-HA composites [7]. Table 7.2 compares the mech-
anical properties of Ti-HA nanocomposites and microcomposites
with different HA contents, produced by various methods.
Table 7.2
Mechanical properties of Ti-HA nano- and microcomposites
ρ
rel
(%)
P
(%)
HV
(GPa)
E
(GPa)
σ
bs
(MPa)
K
IC
(MPa · m
1/2
)Re .
Materials
Ti-3% HA nano 78.5 22 4.7 — —
—
[23]
Ti-10% HA nano 91.6 8 14.7 127 —
1.64
[23]
Ti-20% HA nano 91.3 9 10.9 110 —
—
[23]
Ti-50% HA nano 92.8 7
8.8 124 —
—
[22]
Ti-20% HA micro 97.9 2.1 3.4 103 170 3.57
[7]
Ti-60% HA micro 93.3 6.7 2.9 80 92
2.69
[6]
Ti-80% HA micro 90.2 9.8 3.1 76 79
0.99
[6]
Note:
ρ
rel
, relative density;
P
, porosity; HV, Vickers hardness;
E
, Young's modulus;
σ
bs
,
bending strength;
K
IC,
fracture toughness.
It could be found that the relative density of Ti-10 vol% HA
is 91.6%, while the one of pure Ti can reach
98.6%. The Vickers
microhardness of the Ti-HA nanocomposites exhibits various
distributions corresponding to constitutional change and increase
with the rise of HA contents (Table 7.2). Reinforced by HA particles,
the Vickers hardness of Ti-10 vol% HA composite is greatly higher
than that of Ti-3 vol% HA composite and about six times that of
pure Ti. It should be pointed out that Young's modulus of Ti-HA
nanocomposities can be signiicantly reduced by introduction a
porous structure. Parameter E obtained for Ti-HA nanocomposites
decreases from 153 GPa (microcrystalline Ti) to 110 GPa (Ti-20
vol% HA nanocomposite). A certain degree of porosity is essential
for this type of materials because, it has been documented that, the
porous structure provides better cell attachment, differentiation
and ingrowth osteoblasts and vascularization [30−32].
Table 7.2 clearly shows that the Ti-HA nanocomposites possess
much higher hardness compared to Ti-HA microcomposites. The
change of the chemical compositions in Ti-HA composites leads to a
continuous distribution of the properties (Fig. 7.5) [23]. The value of
such properties ranks among the values obtained for pure titanium
and hydroxyapatite.
