Time-resolved spectroscopic studies of aluminized explosives: Chemical dynamics and apparent temperatures

Abstract

Time-resolved emission spectroscopy and high-speed photography were used to study the chemical dynamics and thermal history of aluminized hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) charges following detonation. The aluminized RDX charges contained 20 wt. % of either 30-70 nm or 16-26 µm Al particles. Non-aluminized RDX charges were also studied for comparison. Spectra collected from the aluminized charges exhibited Al and AlO emissions during the first ∼60 µs, followed by a broadband emission that evolved over two time scales: one in the early time, 0-200 µsec, and another on late time, 0.5-10 ms. The apparent temperatures of the early-time fireballs were obtained using barium atom thermometry and were found to be ∼2900 K for the RDX-only charges, ∼3600 K for the RDX-micron Al charges, and ∼4000 K for the RDX-nano Al charges. In both types of aluminized samples, once Al and AlO emissions ceased, the fireballs began to cool and approached the temperature obtained for the non-aluminized RDX charges. For aluminized charges, a late-time luminescence was also observed, with the intensity and duration dependent upon the size of the Al particles. Aluminum nanoparticles yielded a higher early-time temperature, but a less intense and shorter duration late-time emission, while micron-sized particles produced a lower early-time temperature, but a longer-lived and more intense late-time energy release. These results indicate that post-detonation Al combustion occurs in multiple stages during the evolution of the fireball.