Study on the influence mechanism of size effect and alloy doping on the ignition and combustion characteristics of aluminum particle under laser radiation

Aluminum particles suffer from high ignition temperature, slow combustion kinetics, and incomplete oxidation due to a protective oxide shell; these issues are commonly mitigated by reducing particle size or alloying with reactive elements such as Mg and Li. In this study, the ignition and combustion characteristics of aluminum particles (50 nm to 30 μm) and Al–Mg, Al–Li, and Al–Mg–Li alloys were systematically investigated using thermal analysis and laser ignition, with key parameters including ignition energy, ignition delay, combustion temperature, and spectral features evaluated. The results show that both particle size reduction and alloying significantly enhance aluminum reactivity; alloy particles exhibit lower ignition thresholds, shorter ignition delays, and higher combustion intensities, primarily due to micro-explosion-induced fragmentation. A theoretical model coupling laser intensity, ignition temperature, particle size, ignition delay, and ignition energy was developed and showed good agreement with experimental data. Spectral and combustion wave temperature analyses further confirm that smaller particles and alloying improve combustion efficiency under identical conditions.Post-combustion microstructural analysis reveals cracks and openings in alloy particles that facilitate oxygen transport to the particle interior. The combined effects of particle size, melting point, and micro-explosions govern this behavior. These findings provide mechanistic insight and experimental support for optimizing aluminum particle design and alloy composition in propulsion applications.