Biomedical Engineering Reference
In-Depth Information
FIGURE 4.11
A macrograph of a porous scaffold (a), SEM image of the macrostructure of
the sponge (b) and of the scaffolds sintered at 1300
C with the in-laboratory synthesized
powder (c), and the commercial powder (d). The porosity is open and highly interconnected in
both of the samples. Idea adapted from Ref. 109.
Gervaso et al.
109
produced porous scaffolds with a polymer sponge templating
method using reactive submicrometer powders synthesized by a hydroxide precipi-
tation sol-gel route. The templating method ensured a highly interconnected macro-
channeled porous structure with a more than 500
m mean pore size and 90%
porosity (Fig. 4.11). The high reactivity of the powder led to an efficient sintering
mechanism with a high and crack-free linear shrinkage (19
m
2%) and a significant
BET-specific surface area reduction (from 12 to 0.33 m
2
/g). The powder does not
dissociate into secondary phases during sintering. Despite the extreme porosity, the
scaffolds had high mechanical performance (compressive strength
0.51MPa;
Weibull modulus
4.15) compared with similarly prepared scaffolds from high-
quality commercial HA powder (Fig. 4.12).
The slurry infiltration process for making porous ceramics was studied by
Schwartzwalder and Somers.
110
In this process, PU foam was infiltrated with
ceramic slurry, and the body was compressed by passing it through a set of rollers
to remove the excess slurry. In this manner, the slurry remained coated on the PU
struts, and open pore channels were left in between. The coated PU foam was then
dried followed by burnout of the PU and sintering at a higher temperature. The foams
produced were reticulated foams with porosity within the range of 75-90%.
Zhu et al.
111
investigated the influence of the compressive strain during roll
pressing and the number of passes on the foam microstructure. It was seen that the
quality of slurry coating on to PU struts was strongly dependent on the magnitude of
compressive strain rather than the number of passes. Higher compressive strain
resulted in thinner slurry coating on the struts and a lower bulk density. The coating
Search WWH ::
Custom Search