Reactive, Gallium–Aluminum Composite Nanoparticles for Application in Energetics

The favorable properties of aluminum nanoparticles have led to their application in areas ranging from propellants and explosives to plasmonics. In the area of energetics research, where the heating of aluminum (Al) nanoparticles (nAl) is involved, producing materials that maximize heat flow with a low onset temperature is a sought-after goal. This study examined the ability of gallium (Ga) to increase the reactivity of nAl. Three Al/Ga composite nanoparticles were formed by the addition of Ga salt (GaCl₃) at different time points during the nAl synthesis. The timing of Ga addition was found to correlate with the quantity of Ga present in the resulting composite with earlier addition yielding a higher Ga concentration. The thermal behavior of the Al/Ga composites was assessed by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The Al/Ga composite material produced with early Ga addition produced particles with a TGA trace showing an early onset exothermic peak near 480 °C. This coincided with a peak seen at this temperature in the DSC trace for Ga nanoparticles (nGa). Complete oxidization of this material was achieved below 600 °C, while achieving a higher maximum heat flow, a significant improvement over that of pure nAl. Experiments suggest the reduction of gallium (Ga³⁺) to neutral metal Ga⁰, whose presence was detected spectroscopically in the resulting product concentrated between the active Al core and the exterior aluminum oxide shell.