Biomedical Engineering Reference
In-Depth Information
The DTA thermogramme of TCP - 26.52 wt% Fap composites shows 3 endothermic peaks at
1268°C, at 1280°C and at 1444°C, which are two peaks related with two allotropic
transformations of tricalcium phosphate (Fig. 2d). The temperatures of allotropic
transformations have been decreased about 10°C (1280°C in the place 1290°C) and 20°C
(1444°C in the place 1464°C) with that of the pure β-TCP. This result has been explained
probably by the Fap effect in β-CTCP matrix.
Fig. 2. DTA curves of: (a) β-TCP powder, (b) β-TCP - 13.26 wt% Fap
composites, (c) β-TCP -
19.9 wt% Fap
composites, (d) β-TCP - 26.52 wt% Fap
composites, (e) β-TCP - 33.16 wt% Fap
composites, (f) β-TCP - 40 wt% Fap
composites, (g) Fap powder.
The DTA thermogrammes of β-TCP - 33.16 wt% Fap composites and β-TCP - 40 wt% Fap
composites show only 2 endothermic peaks, which are relative to the allotropic
transformations of tricalcium phosphate (Fig. 2e and 2f). In these curves, the endothermic
peak relative to a peritectic between β-TCP and β-Ca
2
P
2
O
7
is practically disappeared. This
chemical reaction between tricalcium phosphate and pyrophosphate was improved by the
addition of 33.16 wt% or more Fap. Also, the temperatures of allotropic transformations
decreased when the percentage of Fap increases (Fig. 2c-2f). This result has been explained
probably by the Fap effect in β-TCP matrix.
3.2 Sintering and mechanical properties of tricalcium phosphate - fluorapatite
composites
This Table 2 summarizes the mechanical strength of different β-TCP sintered at various
temperatures (1100°C-1450°C) with different amounts of Fap (13.26 wt%, 19.9 wt%, 26.52 wt,
33.16 wt% and 40 wt%).
Fig. 3 illustrates the evolution of density and rupture strength of the composites sintered for
1h at various temperatures (between 1100°C and 1450°C) at different percentages of Fap
(13.26 wt %; 19.9 wt %; 26.52 wt %; 33.16 wt % and 40 wt %). The densification and
mechanical resistance varied as a function of Fap in the β-TCP matrix and sintering
temperature.
