INNOVATIVE BIOINSPIRED SIC CERAMICS FROM VEGETABLE RESOURCES - Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine - page 57

final bioinspired SiC ceramics obtained from two different natural
resources.
Oak ( Quercus robur ) and sapelli ( Entandrophragma cylindricum )
are angiosperms with bimodal pore distribution in the axial direc-
tion typical of hardwoods. Their hierarchic microstructure shows
theexistenceoflarge-vesselcells,calledtracheas(poresizebetween
50 and 200 m in diameter), and smaller cells, called libri-

form “fibers” (size between 2 and 10

μ

μ

m), with thick walls that
are responsible for imparting mechanical resistance. SEM micro-
graphs (Fig. 2.1) show how the cell structure of the vegetable
precursor is reproduced along the process up to the microscopic
level. The carbonaceous templates preserve the anatomical details
of the original vegetable, like the wood vessels and the perfora-
tion plates that connect two vessel elements. The Si infiltration is
very homogeneous inside the material, confirming the intercon-
nectivity of pores. The ceramic microstructure is basically a well-
connected SiC skeleton that replicates the wood cell wall structure,
where the microporosity is partially filled with unreacted Si. More
detailed analysis of the microstructure indicates that the SiC grains
are present both in microcrystalline ( μ SiC) and in nanocrystalline
(nSiC) form. 12 , 19
Porosity measurements (Fig. 2.2) obtained by image process-
ing from SEM micrographs of wood-derived SiC ceramics support
the fact that a large variety of porous scaffolds can be produced
by an adequate selection of the starting vegetable precursors. Thus,
pine-based SiC offers a high amount of regular pores with a narrow
distribution of pore areas centered at 300 m 2 , while hardwoods

(beech and sapelli) provide SiC ceramics with higher pore sizes but
lower frequency of pores.
The marine medium also offers great biodiversity, algae and
plants, providing interesting precursors for ceramic scaffolds.
Fig. 2.3 shows SEM micrographs of SiC ceramics produced from
marine plant species, such as Juncus maritimus and Zostera marina.
Both marine plants have a totally developed vascular system that
ensures the porosity and interconnectivity required for a successful
bioceramization process. The surface details and internal structure
of the original plants are preserved. Thus, SEM micrographs reveal
that regular macrochannels of 100 μ m with aligned microchannels

μ