Enhanced aluminum combustion within supercritical water induced by underwater electrical explosion

In this Letter, we report on the induction of aluminum combustion within supercritical water, facilitated by an underwater explosion bubble. This bubble, initiated using an aluminum-wire electrical discharge in a water-filled tank, typically spans tens of centimeters and undergoes oscillatory dynamics characterized by expansions and compression. When significantly compressed, the bubble reaches conditions of elevated temperature and pressure, sufficient to induce a phase transition of water from its normal to a supercritical state, which provokes the vigorous ignition of micro-sized aluminum particles. We analyze its dynamics by recording the oscillation of the bubble's radius and the corresponding light emission from combustion. Additionally, we observe the cessation of luminescent emissions that last for nearly a millisecond and are attributed to turbulence at the vapor-liquid interface, instigated by hydrodynamic instabilities. These observations elucidate the combustion dynamics of metals in hydrodynamic environments under extreme conditions and pave the way for advanced studies of complex reactive systems.