Effect of metal ions on the crystal morphology and safety performance of ε-CL-20

Metal ions, as common inorganic residues generated during the industrial production of CL-20, can significantly affect its crystal quality, engineering applicability, and safety performance. However, the corresponding intrinsic mechanisms remain insufficiently understood. Herein, Fe³⁺-, Ca²⁺-, and Zn²⁺-doped ε -CL-20 products were purposefully prepared via solvent-antisolvent recrystallization, and their crystal structure, thermal decomposition behavior, and sensitivity were systematically investigated. Scanning electron microscopy (SEM) analysis indicates that the presence of metal ions distinctly alters the crystal morphology of ε -CL-20. Fe³⁺ leads to pronounced crystal coarsening, cubic-like morphology formation, and severe particle aggregation; Ca²⁺ facilitates crystal enlargement and drives the evolution toward rectangular prismatic particles at elevated concentrations; whereas Zn²⁺ primarily promotes particle growth and clustering without substantially changing the original spindle-like habit. Molecular simulations further demonstrate that Fe³⁺ ions play a critical role in regulating the crystal growth process and morphology of ε -CL-20. Simultaneous thermogravimetry-differential scanning calorimetry (TG-DSC) shows that Fe³⁺ and Zn²⁺ reduce the onset decomposition temperature of CL-20 by up to approximately 4 °C, facilitating thermal decomposition. Safety performance was evaluated through impact, friction, and electrostatic sensitivity tests combined with radar-chart analysis. The results indicate that Fe³⁺ causes the most pronounced deterioration in overall safety, whereas Zn²⁺ exhibits promising comprehensive desensitization potential. In contrast, Ca²⁺ deserves particular attention because it tends to increase electrostatic sensitivity. This work elucidates the role of residual metal ions in regulating the crystal morphology and safety of CL-20, offering practical guidance for improving its storage stability and processing safety.