Kinetic Analysis of the Reaction of Micrometer-Sized Al–Mg Alloy Particles in a Water Vapor Atmosphere

This study investigated the reaction mechanism of aluminum–magnesium (Al–Mg) alloy particles with water (Al–Mg/H2O) through thermogravimetric analysis-differential scanning calorimetry experiments and kinetic analysis using isoconversional methods and the master plot technique to determine the reaction mechanism function, with the aim of providing insights to support metal powder/water ramjet engine design and combustion characteristics. The results showed that the Al–Mg/H2O reaction occurred in two distinct stages, with stage 1 primarily involving the reaction of Mg elements in the L­(Al–Mg) alloy with water while Al played a leading role in stage 2. Notably, the reaction temperatures of Al–Mg particles were significantly lower than those for either Al or Mg particles alone in a water vapor environment. Additionally, the activation energy of stage 1 was lower than that for the individual Al and Mg particles and decreased with increasing Mg content in stage 2. Furthermore, the concentration of Mg in the alloy was found to have a major influence on the reaction mechanism, which followed a random nucleation and growth model. Overall, this work elucidated an alternating endothermic and exothermic staged reaction process for Al–Mg/H2O dominated first by Mg and then Al with kinetic insights providing theoretical support for optimizing Al–Mg alloy compositions for improved ignition and combustion performance in metal powder/water ramjet engines.