Investigation of the microstructure of energetic crystals by means of X-ray powder diffraction

Abstract

Mechanical sensitivity of energetic materials is discussed as a function of particle size and lattice defects. Therefore an approach is made to quantify and characterize lattice defects of the energetic powders RDX and HMX using X-ray diffraction. The mechanical properties of these cyclic nitramines are supposed to be dominated by different defect mechanisms – deformation twinning and dislocation slip. The energetic powders and the line shape standard SRM 660a (NIST) were measured on a Bragg-Brentano Diffractometer D5000(Bruker-AXS), and the diffraction patterns were evaluated by Rietveld- and peak profile analysis using Williamson Hall plots. Additionally, preparing samples as thin powder layers was tested in order to reduce line broadening due to low absorption. The investigations reveal interesting details. Characteristic line broadening was found for RDX and HMX pointing to a comparably higher micro strain in HMX. Anisotropic line broadening was found for RDX and discussed in terms of strain fields of dislocations.