Biomedical Engineering Reference
In-Depth Information
Fig. 3D shows the results of densification and mechanical properties of β-TCP - 33.16 wt%
Fap composites. The ultimate densification was obtained at 1350°C (93.2%) and the
maximum of mechanical resistance was approached at 1400°C (13.7 MPa). The β-TCP - Fap
composites ratio was strongly dependent on the percentage Fap addition. The densification
and mechanical properties remain low with 13.26 wt% Fap and 19.90 wt% Fap, when β-TCP
sintered with 33.16 wt % Fap, the densification and mechanical resistance increase with the
sintering temperature and reaches its maximum values.
With 40 wt % Fap, the densification and mechanical resistance decrease slowly with
sintering temperature (Fig. 3E). The optimum relative density was obtained at 1350°C (92%)
and the maximum mechanical resistance reached at 1400°C (11.8 MPa). As the amount of
Fap increased (40 wt %), sinterability and mechanical properties considerably decreased.
This result was clarified by the large (increase weight ratio) amounts of Fap used in the
prepared composites. In fact the microstructure and thermal properties of Fap weren't stable
at high temperature (after 1300°C) (Ben Ayed et al., 2000 and 2001b). Above 1400°C, the
densification and the mechanical properties decrease with any β-TCP sintered with different
percentages of Fap (Fig. 3).
Table 3 summarizes the optimum values of density and mechanical resistance of β-TCP
sintered for 1h with different percentages of Fap. Whatever the content of Fap, the
maximum of densification was obtained at 1350°C, whereas the optimum of rupture
strength was reached at 1400°C (Table 3). The optimum values were obtained for β-TCP
sintered with 33.16 wt% Fap (93.2% and 13.7 MPa).
wt % Fap
13.26
19.90
26.52
33.16
40
Optimum density (%)
87.87
89.00
89.10
93.20
92.62
Optimum strength
(MPa)
7.1
7.1
9.6
13.7
11.8
Table 3. Optimum values of density (at 1350°C) and mechanical resistance (at 1400°C) of
different β-TCP-Fap composites.
An increase of β-TCP- Fap density was shown between 1300°C and 1400°C, where the
optimum densities were obtained at 1350°C with 33.16 wt % Fap. The used temperatures are
similar to the densification of tricalcium phosphate when singly used (Ben Ayed et al.,
2006a). But, the temperatures are relatively higher in comparison to those used for
densification of only Fap (Ben Ayed et al., 2000, 2001b and 2006b). Indeed, Fap presents a
good sinterability in the temperature ranging at 900°C-1100°C (Ben Ayed et al., 2000 and
2001b). At 1450°C, the densities decrease at different degrees of Fap additions. These results
are similar to the previously reported by Ben Ayed et al. during the study of elaboration and
characterization of calcium phosphate biomaterial (Ben Ayed et al., 2007).
This study shows the mechanical properties of the β-TCP-Fap composites samples according
to the sintering temperature. At lower temperature (between 1100°C and 1200°C), the
rupture strength of β-TCP-Fap composites was around 1 and 3 MPa (Fig. 3). When sintering
temperature increase above 1200°C, the rupture strength increases slowly. These results are
due to the increase of the densification caused by the growth of the grains size. Beyond
1300°C, the rupture strength increases and reaches maximum value at 1400°C. Between
1350°C and 1400°C, the increase in rupture strength was very clear for all samples with
different weight ratio of Fap in the composites specimens. This is attributed to the influence
and effect of Fap additive in relative densities and mechanical properties of the sintered
composites. In fact, Ben Ayed et al. show that Fap has a good sinterability and mechanical
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