Intensification of Chemically Assisted Melt–Water Explosive Interactions

This paper investigates avenues for controlled initiation and augmentation of the mechanical and thermal energetic output of shock-triggered vapor explosions (VEs) with Al–GaInSn alloys; furthermore, enabling a means for impulsive hydrogen gas generation within milliseconds. Using a submerged electronic bridgewire detonator or rifle primer caps as the shock trigger for VE initiation, experiments were conducted with 10 g melt drops at initial temperature between 930 K and 1100 K, aluminum mass contents between 0.3 wt.% and 20 wt.%, and water temperatures between 293 K and 313 K. It was found that combined thermal–chemical Al–GaInSn–H₂O explosive interactions can readily be controllably induced via shocks and are of greater intensity than the pure (spontaneous) thermally driven explosions observed with unalloyed Sn and GaInSn. Shock pressures up to 5 MPa were recorded about 10 cm from the explosion zone; a factor of 5 higher than the ∼1 MPa over pressures generated from spontaneous GaInSn–H₂O explosions reported in our previous study. Al–GaInSn–H₂O explosive interactions also exhibited rapid enhancements to the “impulse” H₂ production rate. Hydrogen/vapor bubble volumes up to 460 ml were observed approximately 4 ms after the explosion, equating to a mechanical work and instantaneous power output of 47 J and 11.75 kW, respectively. In comparison with available, analogous, triggered-explosion studies with Al melt drops, our Al–GaInSn alloy melt at 1073 K generated up to 18 times (∼2000%) more hydrogen per gram of aluminum when compared with experiments with molten Al at a much higher melt temperature of 1243 K.