Biomedical Engineering Reference
In-Depth Information
4.10
Clusters of carbon nanofibers (CNFs) in tetragonal zirconia matrix
(ZrO 2 -2vol% CNF): (a) visible on polished surface; (b) as a fracture origin
observed on fracture surface.
￿ ￿ ￿ ￿ ￿ ￿
where many submicron pores at the grain boundaries could still be found. In
this case, these micropores gave rise to a lower than expected fracture
structural integrity (Puchy´ et al., 2011).
One of the most critical aspects governing the reliability of the
microstructure in fibrous nanocomposites is the homogeneous dispersion
of admixed nanofibres (Bala´ zsi et al., 2006), which has proved difficult to
achieve. Insufficient homogenisation leads to fibre clusters of several
micrometres in size. Such clusters are often the largest defects in the
microstructure (Fig. 4.10) and thus the cause of failure. In other cases they
form small islands, such as CNTs in Si 3 N 4 (Fig. 4.11), which are smaller
than the typical critical defect. They do not become fracture origins or
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