We present a new route for tethering graphene nanoplatelets (GNPs) with Fe3O4 nanoparticles to
enable their alignment in an epoxy using a weak magnetic field. The GNPs are first stabilised in
water using poly(vinylpyrrolidone) (PVP) and Fe3O4 nanoparticles are then attached via coprecipitation.
The resultant Fe3O4/PVP-GNPs nanohybrids are superparamagnetic and can be
aligned in an epoxy resin, before gelation, by applying a weak magnetic field as low as 0.009 T.
A theoretical model describing the alignment process is presented. The resulting nanocomposites
exhibit anisotropic properties with significantly improved electrical conductivities (three orders
of magnitude) in the alignment direction and dramatically increased fracture energy (about 530%)
when the nanohybrids are aligned transverse to the crack growth direction, compared with the
unmodified epoxy. Compared with the randomly-oriented nanocomposites, these aligned
nanocomposites show approximately 50% increase in toughness transverse to the alignment
direction and a seven-fold increase in electrical conductivity in the alignment direction.