Thermite powder ignition by localized microwaves

This paper presents a new method to ignite pure thermite powder by low-power microwaves (∼100 W). In this method, the microwave energy is supplied locally to the powder. It creates a confined hotspot, and initiates a self-propagating combustion in the entire powder volume. The coupled thermal-electromagnetic interaction evolved within the powder prior to its ignition is simulated theoretically, taking into account the powder's temperature-dependent parameters. The simulation results show a thermal-runaway instability and localized heating within a confined hotspot, induced mostly by the microwave's electric-field component. The experimental setup employs accordingly an open-end applicator implemented by a miniature solid-state microwave-drill device inserted into the thermite powder as a local igniter. The experimental results show ignition within ∼3 s at 2.1-GHz, 100-W microwave injection, in agreement with the theoretical model. The dependence of the minimal microwave power on the exposure time required to reach combustion is identified. Practical aspects and potential applications of this mechanism, such as rust conversion, energy production, and propulsion are indicated.