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 singlemode 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.

Multi‐Material Aerosol Jet Printing of Al/Cuo Nanothermites for Versatile Fabrication of Energetic Antennas

“…Microwave Ignition: A free-space microwave cavity was used for wireless (non-contact) ignition of the printed antennas (Figure S7a, Supporting Information). [38] Anechoic tiles were placed at the end of the cavity to minimize microwave reflection. The experimental setup consists of a 2 kW magnetron (1.7 kW measured at the waveguide exit using a HP 437B power meter), a circulator and dummy load for magnetron protection, Schottky diodes for forward and reflected power measurements, and a WR-284 open waveguide section to direct the free-space field within the cavity.…”

A review of colored light production by pyrotechnic materials

“…In this study, the addition of 30 wt% GO or reduced GO (rGO) drastically changed thermite microwave absorptivity and microwave ignition delay, because GO reflected microwaves whereas upon thermal treatment (400 °C) in Ar, GO reduced into rGO, which absorbed microwaves. This result shows promise in enabling dynamic control of microwave absorptivity and may lead to smart energetics with dynamically controlled electromagnetic functions [66].…”

Microwave Stimulation of Energetic Al-Based Nanoparticle Composites for Ignition Modulation

“…On the other hand, aluminum is nominally the fuel of choice due to its relatively low cost and mass and volume specific energy density. − However, the dielectric properties of nAl render it relatively microwave insensitive. , Thermites of nAl/Fe 3 O 4 previously studied under microwave stimulation show that while initiation can be obtained, the event extended to several minutes . To compensate for the microwave passiveness of nAl, sensitizers, such as graphene, carbon nanotubes, and reduced graphene oxide (rGO), have been added to energetic materials ,, to ignite and modulate combustion via microwave radiation. Since these materials do not participate in the energetic reaction, the increase in the microwave sensitivity decreases the exothermic output of the composites.…”