Biomedical Engineering Reference
In-Depth Information
and exothermic. The heat generated during the reaction raises
theliquidSitemperatureandenhancestheCsolubility.Thefinal
product is then SiC with a certain amount of unreacted Si and a
smallpercentageofunreactedC.Ifthechanneldiameteriscom-
parable to the C wall thickness, the pores can be blocked by the
precipitation of SiC, preventing the complete reaction of the C
preforminthosezones,whereunreactedCwouldremaininside
the sample. In the final step, most of the excess Si is removed
from the ceramics by cycling it at high temperature over a car-
bon fiber cloth that soaks up the residual Si. The infiltration
process does not significantly change the size and shape of the
pieces (under 0.1%), so this step is oriented to final near-net-
shape products.
12
,
13
To illustrate the bioceramization process, Fig. 2.1 shows typ-
ical carbonaceous scaffolds, after vegetable pyrolyzation, and the
Figure 2.1.
Final SiC ceramics and intermediate carbonaceous products
obtained in the bioceramization process from oak (
Quercus robur
)and
sapelli(
Entandrophragma cylindricum
).Theceramicspreservestheoriginal
porosity and interconnectivity, and the natural microstructure is mimicked
by faceted SiC grains.
Search WWH ::
Custom Search