Particle Size-Controllable Preparation of a CL-20/HMX Cocrystal with High Energy and Low Sensitivity

To address the quality issues arising from the uncontrollable morphological grain size in the preparation of CL-20/HMX cocrystals, a novel method for producing high-quality cocrystals with well-defined morphological grain sizes has been developed. The cocrystallization process was conducted using the solvent/nonsolvent method, wherein the mixing efficiency and solution supersaturation were precisely controlled through systematic optimization of key parameters, including solvent composition, solvent/nonsolvent ratio, reaction temperature, and stirring rate. Through systematic optimization of experimental parameters, three distinct rhombohedral CL-20/HMX cocrystal samples with uniform particle size distributions and well-defined morphologies were successfully prepared, exhibiting characteristic <i>D</i> ₅₀ values of 20, 63, and 130 μm. Comprehensive characterization revealed that SEM analysis demonstrated the cocrystals possess smooth surfaces and regular geometric shapes. Combined XRD and micro-CT analyses confirmed the high crystallinity of the cocrystals, particularly noting the reduced internal defects and superior crystal perfection in larger-grained samples. DSC measurements indicated enhanced thermal stability in cocrystals with larger particle sizes. Furthermore, sensitivity testing showed larger-grained cocrystals are less sensitive than smaller-grained ones, which can be attributed to the more compact internal structure of the crystals.