Effects of nano-sized aluminum on detonation characteristics and metal acceleration for RDX-based aluminized explosive

Abstract

Nano-sized aluminum (Nano-Al) powders hold promise in enhancing the total energy of explosives and the metal acceleration ability at the same time. However, the near-detonation zone effects of reaction between Nano-Al with detonation products remain unclear. In this study, the overall reaction process of 170 nm Al with RDX explosive and its effect on detonation characteristics, detonation reaction zone, and the metal acceleration ability were comprehensively investigated through a variety of experiments such as the detonation velocity test, detonation pressure test, explosive/window interface velocity test and confined plate push test using high-resolution laser interferometry. Lithium fluoride (LiF), which has an inert behavior during the explosion, was used as a control to compare the contribution of the reaction of aluminum. A thermochemical approach that took into account the reactivity of aluminum and ensuing detonation products was adopted to calculate the additional energy release by afterburn. Combining the numerical simulations based on the calculated afterburn energy and experimental results, the parameters in the detonation equation of state describing the Nano-Al reaction characteristics were calibrated. This study found that when the 170 nm Al content is from 0% to 15%, every 5% increase of aluminum resulted in about a 1.3% decrease in detonation velocity. Manganin pressure gauge measurement showed no significant enhancement in detonation pressure. The detonation reaction time and reaction zone length of RDX/Al/wax/80/15/5 explosive is 64 ns and 0.47 mm, which is respectively 14% and 8% higher than that of RDX/wax/95/5 explosive (57 ns and 0.39 mm). Explosive/window interface velocity curves show that 170 nm Al mainly reacted with the RDX detonation products after the detonation front. For the recording time of about 10 μs throughout the plate push test duration, the maximum plate velocity and plate acceleration time accelerated by RDX/Al/wax/80/15/5 explosive is 12% and 2.9 μs higher than that of RDX/LiF/wax/80/15/5, respectively, indicating that the aluminum reaction energy significantly increased the metal acceleration time and ability of the explosive. Numerical simulations with JWLM explosive equation of state show that when the detonation products expanded to 2 times the initial volume, over 80% of the aluminum had reacted, implying very high reactivity. These results are significant in attaining a clear understanding of the reaction mechanism of Nano-Al in the development of aluminized explosives.