Dual functionality of hierarchical hybrid networks of multiwall carbon nanotubes anchored magnetite particles in soft polymer nanocomposites: Simultaneous enhancement in charge storage and microwave absorption

Abstract

We demonstrated, for the first time, the use of submicron size insulative junctions of magnetite (Fe3O4) in conductive networks of multiwall carbon nanotubes (MWNTs) for simultaneously achieving enhanced charge storage and superior microwave absorption in X-band (8.2–12.4 GHz) frequency range. Herein, electrical conductivity in fluoroelastomer matrix was attained by dispersion of MWNTs, whereas low dielectric loss was achieved by employing Fe3O4 particles as insulative spacers between MWNT networks. High-performance charge-storing nanocomposites were developed using unique approach where relatively large insulative Fe3O4 spacers were anchored to MWNT networks leading to disrupted conductive pathways. The size of Fe3O4 particles was controlled in such a way that the distance between discrete MWNTs at the insulative junction is larger than the critical distance required for hopping and tunneling of nomadic charges. This also resulted in optimum impedance matching and additional magnetic loss associated with Fe3O4, which led to the synergistic absorption of microwaves. Taken together, the anchoring of sub-micron size Fe3O4 particles with MWNTs provided dual functionality of high real permittivity (ε') along with decreased dielectric loss which are both favorable for charge storage. Furthermore, it led to improved impedance matching and we were able to achieve maximum microwave absorption.