Civil Engineering Reference
In-Depth Information
h e distribution of BC nanoi bers and MWCNTs in BC/MWCNTs hybrids can also
be well illustrated by FESEM images, as showed in Figure 2.32, for a hybrid prepared
by incorporation of the nanotubes during BC biosynthesis. h e uniform dispersion
of MWCNTs is a critical issue in electrical conductive materials, the main application
investigated for BC/MWCNTs hybrids.
BC/MWCNTs have shown conductivities of around 0.14-0.42 S.cm
-1
for membranes
with ~10 wt% MWCNTs content [285, 286], and ranging from 10
-5
to 10
-2
S.cm
-1
for
transparent and bendable papers with wt% of MWCNTs ranging from 0.01 to 0.1% [289].
Conductive BC/MWCNTs were used as nanocomposite electrodes in various applica-
tions [231, 295]. For example, in the immobilization of the enzyme glucose oxidase,
where the electron transference between the enzyme and the BC/MWCNTs was dem-
onstrated, opening potential applications in the biomedical i eld such as biosensors, bio-
fuel cells, and bioelectronic devices. In another example, silver nanowires were deposited
onto the surface of the MWCNTs [231] and tested toward oxygen reduction reaction to
demonstrate their potential as electrodes in membranes for alkaline fuel cells. Although
the improvements in mechanical properties observed in BC/MWCNTs was not accessed
in most reported studies, modulus increments of around 400% have been reported for
1 wt% MWCNTs load in hybrids with regenerated BC nanoi bers, clearly demonstrat-
ing the reinforcing potential of MWCNTs in the ensuing hybrids [291]. Graphene oxide
(GO) has also been investigated for the production of highly l exible conductive BC
hybrids [297]. At er reduction of GO these materials achieved conductivity increments
of six orders of magnitude when compared with pure BC, even for 1% of GO.
Finally, BC hybrids with graphite nanoplatelets (multilayered GO) have shown elec-
trical conductivities one order of magnitude higher (~4.5 S.cm
-1
) than that observed for
loadings of MWCNTs in the same order of magnitude (~10%) [294].
Figure 2.31
Typical aspect of a) BC pelicles produced under agitated conditions and b) the corresponding
BC/MWCNTs hybrids (adapted from [290]); and C) transparent i lms (adapted from [289]).
Figure 2.32
FESEM images of a diferent regions (
a
) surface,
b
) middle and
c
) center) of BC/MWCNTs
hybrid pelicles. Reproduced with permission from [290].
