Smart Electromagnetic Thermites: GO/rGO Nanoscale Thermite Composites with Thermally Switchable Microwave Ignitability.

Abstract

This effort demonstrates the development of a novel, graphene oxide nanoscale thermite composite with thermally tunable microwave ignitability. A model thermite system containing nanoscale aluminum and nanoscale iron(II) oxide in a stoichiometric ratio (30/70 wt %) was combined with sheets of graphene oxide (GO) or reduced graphene oxide (rGO) using an immiscible two-fluid sonication and tape casting process. The samples were microwave irradiated within a single-mode resonant microwave cavity to determine the microwave ignition delay. Neat thermites were found to ignite after 4.34 s of microwave illumination, whereas 30 wt % rGO thermite composite ignition delay was an order of magnitude shorter (0.43 s). For most samples (4 of 6 trials), it was found that application of a 30 wt % GO coating inhibits microwave ignition of the thermite. Thermal treatment of the GO thermite composite led to switching of thermites from unignitable to ignitable with microwave field application as short as 0.24 s due to GO reduction. Optimum heat treatment time and GO content are explored with SEM, DSC/TGA-MS, Raman, and XPS deconvolution. This effort demonstrates the use of GO and rGO addition to achieve thermally switchable microwave ignitability to electromagnetically shield or enhance nanoscale energetic ignition by microwave energy.