Chapter 6. Co-crystallization of Energetic Materials

Energetic materials have widespread, vital uses in many military and civilian applications in which the storage and rapid release of large amounts of chemical energy is required. Key requirements of these materials include high performance combined with sufficient stability to enable them to be manufactured, stored, and transported safely. This chapter highlights how recent developments in the co-crystallization of energetic materials (explosives and propellants) can be used to modify some of the important properties of these materials, such as detonation velocity, detonation pressure, oxygen balance, density, crystal morphology, thermal and long-term chemical stability, melting point, and sensitivity to initiation through mechanical impact, friction, spark, and shock. The importance of intermolecular interactions within crystal structures for the design and discovery of energetic co-crystals is discussed. The influence of structure on the physicochemical properties of the materials is also highlighted. Also discussed are the challenges associated with distinguishing between co-crystals and physical mixtures of materials for which characterization by single crystal X-ray diffraction is not possible. Novel techniques such as resonant acoustic mixing are introduced as a means for the large-scale production of energetic co-crystals. Finally, future challenges and directions in the field are highlighted, including the requirement for the development of more robust structure–property relationships for energetic co-crystals, especially with regard to sensitivity to initiation.