Enhancing combustion efficiency: development and characterization of Al–In–Sn ternary alloy fuel with high reactivity

Aluminum powder, a common metallic fuel for propellants and explosives, is limited by high ignition temperatures, incomplete combustion and particle agglomeration. To mitigate these drawbacks, we synthesize core–shell Al–In–Sn ternary alloy fuel by facile melt casting. Eutectic phase separation drives spontaneous formation of an InSn₄ protective shell on Al particle surfaces. The InSn₄ shell functions as a passivation barrier at low temperatures to inhibit premature oxidation and guarantee storage stability. Upon heating above 250 °C, thermal expansion mismatch ruptures the molten shell, exposing active Al and triggering strong exothermic oxidation. The optimized 80Al–In–Sn sample exhibits an oxidation heat release of 1220 J/g (11.5-fold higher than pristine Al), a mass gain efficiency of 76.3%, and reduced activation energy (242.9 kJ/mol by Kissinger method versus 403 kJ/mol for pure Al), verifying greatly enhanced reactivity. Combined DSC and XRD results reveal the temperature-controlled oxidation mechanism. This work offers guidelines for designing storable, highly reactive alloy fuels and facilitates their engineering applications within energetic materials.