Magnetic structuring of nickel-coated carbon nanotubes with diazonium treatment for tailorable and bulk nanocomposite fabrication

Polymer nanocomposites are novel materials sought-after for their tailorable and advanced mechanical, electrical, thermal, and actuation/sensing properties. Desired property enhancement of nanocomposites relies on controlled distribution of nanofillers. However, it is difficult to achieve controlled distribution of nanofillers in bulk production. In this work, we experimentally investigate active nanofiller assembly using external magnetic fields, as a simple, non-contact, scalable, and energy-efficient manufacturing solution of polymer nanocomposites. Carbon nanotubes (CNTs) are selected as the nanofiller, because of their high mass-specific strength and transport properties. We first processed CNTs to make them magnetically responsive, by e-beam coating the CNT tips with nickel (Ni), after functionalizing their surfaces with oxygen plasma to promote Ni-CNT adherence. Then, we attached diazonium salt on the CNT surfaces, to improve their dispersion in and to promote covalent bonding with the bisphenol-F based epoxy matrix. CNT alignment was achieved within the viscous matrix (~70 cP), after the short (~40 min) magnetic field application of small strength (~400 G vs. ∼50 G of a typical refrigerator magnet). Further 3D tomography inspection will be conducted about CNT structuring, and associated thermal and electrical transport properties will be characterized for structure-property relationship studies in future.