Abstract
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 (∼50 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.
Highlights
Many applications of polymeric materials in electronic devices, fuel storage and transportation, automotive, and aerospace products demand good mechanical properties for structural integrity and high electrical conductivities to dissipate static electricity [1]
The magnetic nature of the as-prepared Fe3O4@carbon nanofibers (CNFs) was demonstrated by placing a magnet next to an ethanol dispersion of the nanofiber hybrids
Using the techniques of optical microscopy, Scanning electron microscopy (SEM) and transmission electron microscope (TEM), it has been conclusively established that the Fe3O4@CNFs can be aligned in the liquid epoxy resin by the application of a relatively weak magnetic field (~50 mT), and that this alignment of the nanofiber hybrids is maintained after the epoxy nanocomposites are cured
Summary
Many applications of polymeric materials in electronic devices, fuel storage and transportation, automotive, and aerospace products demand good mechanical properties for structural integrity and high electrical conductivities to dissipate static electricity [1] Carbon nanomaterials, such as carbon nanotubes (CNTs), carbon nanofibers (CNFs), and graphene nanosheets (GNSs), have emerged as promising nanofillers for polymer nanocomposites due to their outstanding mechanical and electrical properties [2e4]. S. Wu et al / Polymer 68 (2015) 25e34 to orient and align CNTs in an epoxy resin and found that the properties of the resulting nanocomposites were superior to those prepared in the absence of a magnetic field. The present work aims to explore the functionalisation process to coat carbon nanofibers with magnetic iron oxide nanoparticles by co-precipitation and to align the resultant nanofiber hybrids in an epoxy resin for developing epoxy nanocomposites with anisotropic electrical and mechanical properties.
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