Biomedical Engineering Reference
In-Depth Information
-88
-200
-150
-100
-50
0
50
100
Chemical Shift / ppm
Fig. 17.
29
Si NMR spectrum of the sample treated at 1000°C.
aluminosilicate crystalline structures. This is consistent with our X-ray data. The
nonhydrolytic sol-gel method has proved efficient for the preparation of materials with
glass properties, as shown in this work. This process enables reaction control and the use of
stoichiometric amounts of Al and Si reagents at low temperatures, near 110
o
C, thereby
reducing production costs.
The preparation of aluminosilicate-based matrices by the nonhydrolytic sol-gel method,
using varying concentrations of the glass components, especially the element phosphorus,
has been accomplished by our group [84]. Figure 18 depicts the X-ray diffractograms for the
samples A2, A3.3, and A4, all dried at 50ºC.
An amorphous structure predominates in sample A2. The A3.3 material displays an
amorphous structure with crystalline phases attributed to fluorapatite (Ca
5
(PO
4
)
3
OH) and
mullite (3Al
2
O
3
2SiO
2
), according to Gorman et al. Sample A4 also presents an amorphous
phase and a crystalline phase, which is ascribed to mullite [85]. The X-ray diffraction
analysis revealed the influence of the phosphorus concentration on the structural formation
of the materials. The material prepared with the Wilson formulation has an amorphous
structure, while the one prepared according to Hill displays an amorphous structure with a
crystalline phase attributed to mullite. An increase in phosphorus in the Hill formulation
allows the formation of an amorphous material with crystalline phases attributed to mullite
and fluorapatite. The increase in phosphorus concentration affects the formation of the
