Epoxy nanocomposites containing magnetite-carbon nanofibers aligned using a weak magnetic field

Novel magnetite-carbon nanofiber hybrids (denoted by Fe3O4@CNFs) have been developed by coating carbon nanofibers (CNFs) with magnetite nanoparticles in order to align CNFs in epoxy using a relatively weak magnetic field. Experimental results have shown that a weak magnetic field (∼mT) can align these newly-developed nanofiber hybrids to form a chain-like structure in the epoxy resin. Upon curing, the epoxy nanocomposites containing the aligned Fe3O4@CNFs show (i) greatly improved electrical conductivity in the alignment direction and (ii) significantly higher fracture toughness when the Fe3O4@CNFs are aligned normal to the crack surface, compared to the nanocomposites containing randomly-oriented Fe3O4@CNFs. The mechanisms underpinning the significant improvements in the fracture toughness have been identified, including interfacial debonding, pull-out, crack bridging and rupture of the Fe3O4@CNFs, and plastic void growth in the polymer matrix.