Thermal oxidation and combustion characteristics of single particle AlH3

Abstract

The oxygen content is a key factor influencing the ignition and combustion performance of AlH₃ particles. This study investigated the thermal decomposition and oxidation characteristics of AlH₃ under different oxygen concentrations using thermogravimetric analysis and differential scanning calorimetry. A tube furnace was used to collect reaction products at various temperatures, and their microstructures and crystal transformations were analyzed to explore the hydrogen release and oxidation mechanisms. Additionally, a settling furnace ignition experimental system was established to study the combustion characteristics and flame morphology of single AlH₃ particles under different oxygen content. The thermogravimetric results indicated that the thermal decomposition and oxidation reactions of AlH₃ under different oxygen concentrations could be divided into one weight loss stage and two weight gain stages. Although the amount and rate of reaction varied among the stages, there was little difference in the degree of oxidation at 1200 °C. The oxidation layer undergoes phase transformations from amorphous Al₂O₃ to γ-Al₂O₃ and finally to α-Al₂O₃, with needle-like structures appearing at 1000 °C. The combustion results showed that when the oxygen concentration is high, particles are prone to micro explosions. Simultaneously observed phenomena such as diffusion flames, growth of oxidation caps, and gas emission. The combustion time of AlH₃ was found to be slightly lower than the empirical values for aluminum, and the ignition delay time was also lower compared to aluminum. Both the ignition delay time and combustion time of the particles decreased with increasing environmental oxygen content.