Biomedical Engineering Reference
In-Depth Information
bands were characteristic of phosphate group of β-TCP and Fap (at 540-600 cm
-1
and 920-
1120 cm
-1
). The peaks at 920 cm
-1
and 1120 cm
-1
are assigned to the stretching vibration of
PO
4
3-
ions and the peaks at 540 cm
-1
and 600 cm
-1
are assigned to the deformation vibration
of PO
4
3-
ions. The bands at 3500 cm
-1
and at 1640 cm
-1
were assigned to the adsorbed water
molecule.
(A)
(B)
(C)
(d)
(d)
(d)
(c)
(c)
(c)
(b)
(b)
(a)
(b)
(a)
(a)
4000
3600
3200
2800
2400
2000
1600
1200
800
400
4000
3600
3200
2800
2400
2000
1600
1200
800
400
4000
3600
3200
2800
2400
2000
1600
1200
800
400
Wavenumber (cm
-1
)
Wavenumber (cm
-1
)
Wavenumber (cm
-1
)
(A) with 13.26 wt% Fap at various temperatures: (a) 1100°C, (b) 1200°C, (c) 1300°C and (d) 1400°C.
(B) with 40 wt% Fap at various temperatures: (a) 1100°C, (b) 1200°C, (c) 1300°C and (d) 1400°C.
(C) at 1400°C with different percentages of Fap: (a) 13.26 wt %; (b) 19.9 wt %; (c) 33.16 wt %
and (d) 40 wt%.
Fig. 8. IR of β-TCP sintered for one hour
Figs. 8A(a-b), 8B(a-b) show the IR spectra of the β-TCP-Fap composites sintered at 1100°C
and 1200°C, respectively. In the spectra absorptions assigned to OH group, are detected at
3510 cm
-1
and 747 cm
-1
. Those absorptions indicate that the OH group substitutes F in the
Fap structure, thus leading to the formation of hydroxyfluorapatite (Ca
10
(PO
4
)
6
F
2-x
(OH)
x
:
FOHap). This compound may be the result of the reaction between Fap and water vapour
traces (Ben Ayed et al., 2001b). This reaction was illustrated by Eq. 5. At higher temperature
(1300°C-1400°C), the intensity of these bands decreases but does not completely vanish
supposing that the amount of fluoride in the samples decreases when the temperature
increases (Figs. 8A(c-d), 8B(c-d)). IR spectra of
different composites sintered at 1400°C with
different percentages of Fap (13.26 wt %; 19.9 wt %; 33.16 wt % and 40 wt %) were
practically similar to the Figs. 8A-8B. Indeed, the typical IR spectra show the characteristics
of the phosphate group of calcium phosphates (at 500-600 cm
-1
, 1019 cm
-1
, 1034 cm
-1
, 1105
cm
-1
).
At higher temperatures, the β-TCP-Fap composites densification and mechanical
properties were hindered by the exaggerated grain growth, the effect of the allotropic
transformation of β-TCP and the formation of intragranular porosity. The SEM
micrograph illustrated the change of microstructure at 1450°C. These results are similar to
the previously obtained by Ben Ayed et al. during the sintering process of TCP-Fap
composites (Ben Ayed et al., 2007).
