BN nanotubes coated with uniformly distributed Fe3O4 nanoparticles: novel magneto-operable nanocomposites

An ethanol-thermal process was developed for in situ formation of dense and uniformly distributed Fe3O4 nanoparticles on the surfaces of multi-walled boron nitride nanotubes (BNNTs). The morphology, structures and compositions of the synthesized nanocomposites were characterized by X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), high-angle annular dark-field (HAADF) STEM. selected area electron diffraction (SAED) and electron energy loss spectroscopy (EELS). Magnetic measurements using a superconducting-quantum-interference-device (SQUID) magnetometer showed that the nanocomposites exhibited normal ferromagnetism at low temperature (5 K), while they behaved as soft magnets with negligible coercivity, H-c, and remanance, M-r, at room temperature. Such magnetic behavior was attributed to the superparamagnetic nature of Fe3O4 nanoparticles attached to BNNTs. By virtue of the dense and uniform magnetic Fe3O4 coatings, the BNNTs Could be physically Manipulated in a relatively low magnetic field. The novel BNNT-based magnetic nanocomposites may find a wide range of potential applications in magnetorheological devices, microelectromechanical systems (MEMS), magnetic-targeted drug delivery and boron neutron capture therapy (BNCT).