Underwater microwave ignition of hydrophobic thermite powder enabled by magnetic encapsulation

Highly energetic thermite compounds have potential applications in combustion synthesis of various materials and processes, but they are hard to ignite by conventional means. A new technique for ignition of pure thermite powder in air atmosphere, using localized microwaves, was demonstrated recently. This exothermic zero-oxygen-balanced reaction may occur underwater, but due to the hydrophobic properties of the particles the powder tends to agglomerate in the liquid-air surface when contacting with water. Here we present a utilization of the magnetic features of the thermite powder in order to facilitate the penetration of pure thermite into water without a physical contact. The required magnetic field structure is studied, and its implementation in practice is presented. Thermite ignition underwater is demonstrated by localized microwave heating of the thermite batch. The reaction is confirmed by ex-situ XPS analysis. Potential applications of this combustion technique underwater, e.g. for detonation, wet welding, thermal drilling, and material processing, are discussed.