Characterization and differentiation of aluminum powders used in improvised explosive devices-Part 4: Particle morphology and microanalysis of powders produced with different manufacturing methods.

Many readily available online videos and instructional manuals provide information on how to manufacture aluminum (Al) powder, a component in pyrotechnics and improvised explosive devices (IEDs) using common household materials. Given the ease in acquiring and producing Al powders, it is common to observe Al powder in IEDs. Thus, there is a need to characterize Al powders, in a forensic context, to determine whether there are signatures that could be used for sample differentiation and placing potential constraints on the method of Al powder production. In this study, samples of Al powder that were derived from industrial products (including end-use commercial products) and those made using amateur methods were analyzed. The powders were analyzed using a combination of morphology (viewed with light and scanning electron microscopy (SEM)) and elemental profiling (using energy dispersive X-ray spectroscopy (EDS)). The results demonstrate that Al powder manufactured by industrial processes can be readily differentiated from amateur methods. The gross microscopic morphology of the particles provided the basis for the recognition of several different particle types/classes. These types provide insight into their method of production. Of particular note is the ability of morphological characteristics to differentiate between flake-type powders, which are made by both industrial and amateur methods. This differentiation is primarily due to significant differences in the particle size distribution and the particle edge textures.