Morphological Variations of Explosive Residue Particles and Implications for Understanding Detonation Mechanisms

The possibility of recovering undetonated explosive residues following detonation events is well known, however, the morphology and chemical identity of these condensed phase post-blast particles remains undetermined. An understanding of the post-blast explosive particle morphology would provide vital information during forensic examinations, allowing rapid initial indication of the explosive material to be microscopically determined prior to any chemical analyses, and thereby saving time and resources at the crucial stage of an investigation. In this study, condensed phase particles collected from around the detonations of aluminized ammonium nitrate and RDX-based explosive charges were collected in a novel manner utilising SEM stubs. By incorporating the use of a focused ion beam during analysis, for the first time it has been possible to determined that such particles have characteristic shapes, sizes and internal structures depending on the explosive and the distance from the detonation at which particles are recovered. Spheroidal particles (10 µm to 210 µm) with micro surface features recovered following inorganic charge detonations were dissimilar to the irregularly shaped particles (5 µm to 100 µm) recovered following organic charge firings. Confirmatory analysis to conclude the particles were indeed explosive included HPLC-MS, Raman spectroscopy and MeV-SIMS. The results impact not only on forensic investigation but also on the theoretical constructs which govern detonation theory by indicating the potential mechanisms by which these particles survive and how this varies between the different explosive types