Biomedical Engineering Reference
In-Depth Information
Mixing of reagents
Production of sol (dispersion of
colloidal particles in a liquid) via addition of detergent
Gellation of sol (gel is an interconnected ridged
network with submicron pores and
polymeric chains larger than 1µm)
Foaming material via
vigorous mechanical agitation
Cast gel; age gel; dry gel
and thermally stabilize at 600
º
C
Monolith mechanically stabilized
via sintering (600-1000
º
C)
FIGURE 9.5
Schematic showing sol-gel processing of sol-gel glasses [8].
Si dissolution rates can thus be described by (9.2) and (9.3):
D
[Si]/d
t
=
k
1
t
−1/2
for
t
<
t
*
(9.2)
and
D
[Si]/d
t
=
k
1
t
−1/2
for
t
>
t
*
(9.3)
These expressions can be used to describe Si dissolution from melt-derived bioactive
glasses as well.
TABLE 9.5
Characteristics of 45S5 and 58S Glass Compositions
MaterialCharacteristics
45S5
58S
Bulkcomposition(mol%)
SiO
2
46.1
60
CaO
26.1
36
P
2
O
5
2.6
4
Na
2
O
24.4
-
Powders
Surface area (m
2
g 1)
0.3-2.7
126.5-164.7
Pore volume (cm
3
/g)
0.001-0.035
0.213-0.447
Pore diameters (nm)
-
2-5
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