The crystalline product quality is determined by the crystal size distribution, type of solid state, morphology, purity, and internal defects. For energetic materials it is thought that the initiation of an explosion can be caused by an unintentional shock wave hitting a defect upon its propagation through a crystal. Crystal defects like dislocations usually originate from inclusions and, since inclusions are relatively large, a much lower overall defect content is expected in nano- and submicron-sized crystals.

A team from Delft University of Technology and TNO Defence, both in The Netherlands, presents an electrospray crystallization method for producing submicron-sized crystals of the energetic compound cyclotrimethylene trinitramine (RDX). The method combines electrospraying of an undersaturated solution and solvent evaporation from the created droplets.

Using this method, submicron-sized crystals of RDX can be produced. The samples were remarkably insensitive to friction stimuli while an insignificant difference for the impact sensitivity was observed. The operation window to establish a continuous jet and produce submicron-sized crystals is relatively narrow, but experimentally feasible.

Image: (c) Wiley-VCH

• Electrospray Crystallization for High-Quality Submicron-Sized Crystals
  N. Radacsi, A. I. Stankiewicz, Y. L. M. Creyghton, A. E. D. M. van der Heijden, J. H. ter Horst,
  Chem. Eng. Technol. 2011, 34 (4).
  DOI: 10.1002/ceat.201000538