Solid spheres composed of CL-20/HMX co-crystal via droplet-confined crystallization: preparation and characterization

Solid spheres composed of sub-micron CL-20/HMX co-crystal particles with nitrocellulose (NC) as a binder and structural framework were fabricated by droplet-confined crystallization. Optimal preparation conditions were established through single-factor experiments, which evaluated key parameters including the concentration of explosive solution and NC, the temperature of the explosive solution and non-solvent, and the drop height. NC, uniformly distributed, facilitates the aggregation of approximately 2 μm granular CL-20/HMX co-crystal particles into dense spherical structure with a diameter of about 1 mm. The solid spheres exhibit not only regular spherical morphology and uniform particle size distribution but also enhanced flowability and higher packing density compared to previously reported hollow spheres and flake-like co-crystals. Furthermore, the solid spheres show a reduced decomposition temperature and more rapid energy release, along with decreased friction sensitivity, improved ignition performance and pronounced self-sustaining combustion characteristics. This study demonstrates that the structure of energetic materials can influence their properties and also provides a new reference for the preparation of molding powders for press-loaded explosives.