Thermite-Assisted Cu-Coated Al Powder as a Solid Propellant: Expanding the Use of Coarse Al Powder

Aluminum (Al) powder is a key fuel for solid propellants, but its native oxide (Al2O3) layer acts as a diffusion barrier, resulting in incomplete combustion. Although coarse Al powders offer excellent handling stability, their reactivity is considerably lower. To address this limitation, we coated Al powders with copper (Cu) by electroless plating to form a dual-layer shell with an outer Cu layer and an inner Al2O3 layer. During combustion, the Cu layer induces a thermite reaction at the powder surface, generating intense thermal stress that ruptures the dense oxide shell and promotes oxidation of the internal Al core. Thermogravimetric analysis and differential scanning calorimetry showed higher reactivity and significantly greater heat release in the Cu-coated Al (Cu/Al) powders. In combustion and propulsion tests, the 35 μm Cu/Al powder achieved maximum explosion pressures and pressurization rates comparable to those of pristine 5 μm Al powder, together with a higher specific impulse. This surface modification improves the combustion efficiency of coarse Al powders and offers a promising route to high-performance solid propellants. However, the reduced margin against electrostatic discharge must be considered during handling.