Abstract
A new synthesis approach for aluminum particles enables an aluminum core to be passivated by an oxidizing salt: aluminum iodate hexahydrate (AIH). Transmission electron microscopy (TEM) images show that AIH replaces the Al2O3 passivation layer on Al particles that limits Al oxidation. The new core-shell particle reactivity was characterized using laser-induced air shock from energetic materials (LASEM) and results for two different Al-AIH core-shell samples that vary in the AIH concentration demonstrate their potential use for explosive enhancement on both fast (detonation velocity) and slow (blast effects) timescales. Estimates of the detonation velocity for TNT-AIH composites suggest an enhancement of up to 30% may be achievable over pure TNT detonation velocities. Replacement of Al2O3 with AIH allows Al to react on similar timescales as detonation waves. The AIH mixtures tested here have relatively low concentrations of AIH (15 wt. % and 6 wt. %) compared to previously reported samples (57.8 wt. %) and still increase TNT performance by up to 30%. Further optimization of AIH synthesis could result in additional increases in explosive performance.
Highlights
One approach recently introduced involves chemically altering the oxidation shell of an Al particle that is initially composed of an amorphous Al2O3 outer shell and crystalline Al core
Their results show that the Al2O3 passivation layer surrounding Al particles delays the onset of Al oxidation such that Al oxidation does not occur in the detonation wave[9,10]
The concentrations of Al°, aluminum iodate hexahydrate (AIH) and iodic acid from AIH6, AIH15 and another AIH sample mixed at an initial equivalence ratio (ER) of 0.9 discussed in Smith et al.[13,14] are included in Table 1 for comparison
Summary
One approach recently introduced involves chemically altering the oxidation shell of an Al particle that is initially composed of an amorphous Al2O3 outer shell and crystalline Al core. Capellos et al.[9] and Baker et al.[10] developed an eigenvalue detonation model to determine the effects of the Al2O3 passivation layer on Al oxidation when Al powders are used as additives in explosive mixtures. The objective of this study is to examine the energy release from novel Al0-AIH samples that vary slightly in AIH concentration from ~6% AIH to 15% AIH (i.e., AIH6 and AIH15) compare to the reactions of conventional micron-sized Al particles, alumina (Al2O3), and a physical mixture of Al/I2O5 This analysis is further extended to composites of TNT with each of these additives: micron-sized Al, Al2O3, Al/I2O5, AIH6 and AIH15. The uncertainty in the XRD measurements from peak fitting and variation between samples is calculated to be less than 6.9% for all concentrations
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