Civil Engineering Reference
In-Depth Information
It is i nally clear that an extensive and copious literature exists on the use of cellulose
nanoreinforcements and metal nanoparticles as hybrid systems and signii cant interest
is devoted to the study of such high performance hybrids and new related applications
in the evolving area of nanotechnology.
6.3.2
CNR and Ceramic Nanoparticles
Several approaches have recently been used for self-assembled biomimetic composite
i lms, aiming at combinations of high toughness, strength, and stif ness. However, it
remains challenging to achieve high toughness using simple processes especially for
bulk materials. It was demonstrated that ionically interacting cationic native nanoi bril-
lated cellulose (C-NFC) and anionic nanoclay, i.e., montmorillonite (MTM), allow local
self-assemblies by a simple centrifugation process to achieve 3D bulk materials and the
obtained tough bulk nanocomposites have potential in applications for sustainable and
environmentally friendly materials in construction and transportation [99]. In Wesarg
et al.
[21] , an
in-situ
modii cation route for the preparation of a hybrid material con-
sisting of bacterial nanocellulose (BNC) and photocatalytically active anatase (TiO
2
)
nanoparticles is described. h e inl uence of dif erent nanoparticles concentrations on
the BNC biosynthesis and the resulting supramolecular structure of the hybrids were
investigated and it was demonstrated that the
in-situ
integration of photocatalytically
active nanoparticles into BNC represents an attractive possibility to extend its i elds of
application to porous i ltering media for drinking water purii cation and air cleaning.
h e formation of hybrids of nanoi brillated cellulose and titania nanoparticles in aque-
ous media has been studied by Schutz
et al.
[100], in which they demonstrated that
limiting the titania nanoparticle concentration below 16 vol%, homogeneous hybrids
with a very high Young's modulus and hardness and an optical transmittance above
80% can be obtained. h e incorporation of SiO
2
nanoparticles in cellulose aerogels,
which are ultra-low density materials and generally exhibit poor mechanical proper-
ties, was also investigated: silica/cellulose composite aerogels were prepared by
in-situ
synthesis of silica in the porous structured cellulose hydrogel scaf olds by using water
glass as silica source. h e compressive properties of the silica/cellulose aerogels greatly
exceeded those of pristine cellulose aerogels. Moreover, unlike inorganic silica aerogels,
the composite aerogels had high l exibility, withstanding large amounts of compressive
strain without failure [101]. Novel regenerated cellulose/sepiolite (RC/SEP) nanocom-
posite i lms have been also prepared using an environmentally friendly ionic liquid,
1-butyl-3-methylimidazolium chloride (BMIMCl), through a simple, cost ef ective and
“green” method [102]. h e obtained results revealed interactions between the sepiolite
and regenerated cellulose: mechanical properties of the nanocomposite i lms were sig-
nii cantly improved compared to pure regenerated cellulose i lm, interestingly without
loss of ductility, moreover the presence of sepiolite enhanced the thermal stability and
char yield of the nanocomposites. Recently, nanocomposites of polymers and nanoi -
brillated cellulose as a reinforcing component have been developed, whose interest is
particularly shown in the possibility to modify the matrix properties, also by grat ing of
appropriate moieties on the polymer [103, 104]. A few communications on NFC/clay
composites (also referred to as “nanopaper”) have also been published (Figure 6.2B ):
these indicated some interesting properties, including excellent optical transmittance
