| The aim of the present work was to address the hazardous vulnerability of energetic materials to accidental initiation. An improved form of the explosive RDX with a significantly reduced sensitivity to stimuli including shock and impact was sought. The direction of this research was to investigate the effect of RDX crystal size reduction down to nano-scale dimensions on the sensitivity characteristics. Although size reduction of energetic crystals has been demonstrated often to result in a sensitivity reduction, the effect at the nano-scale particle size has not been investigated.;The RESS process yielded pure RDX with a mean crystal size ranging from around 100 to 1000 nm with a relatively narrow size distribution and near spherical particle shape. Continuous processing with efficient particle collection and solvent recycling was accomplished enabling bulk production.;The sensitivity of RDX recrystallized by RESS was tested to stimuli including electrostatic discharge, impact, and shock was tested. Both pure samples as well as wax-based formulations were tested. Two types of recrystallized RDX were tested, Type A and Type B, with a corresponding specific surface area of around 20 and 6 m2/g. Both samples exhibited a significantly lower sensitivity to shock and impact compared to the reference 4.8 micron RDX. The coarser Type B nano RDX was found to be the least sensitive with all the tests. This indicates the existence of a minimum in sensitivity with crystal size.;To generate nanocrystalline RDX a recrystallization process was developed based on rapid expansion of supercritical solutions (RESS). Compressed carbon dioxide was utilized as the solvent for RDX. Effect of key process parameters including the pre- expansion temperature and pressure, post-expansion pressure, and nozzle dimensions was investigated experimentally and via mathematical modeling. |
