Advanced crystalline energetic materials modified by coating/intercalation techniques

In the field of energetic materials (EMs), the problems of sensitivity and relatively high cost limit their practical applications in certain conditions. Therefore, various newly developed high energetic compounds are still not in use. The balance between the energy density and safety of EMs remains a highly challenging task. Numerous strategies have been implemented to achieve this balance. The most typical ones are coating, intercalation, recrystallization, cocrystallization, hybridization and chemical grafting methods. Of all the mentioned modification methods, the coating/intercalation have been found to be the best and the most widely used ones, due to their safer but cost-effective operations with well-controlled procedures, which may result in products with tunable properties. In cases of coating/intercalation of energetic crystals, different coating agents and fabrication techniques, including the well-known water suspension, in-situ polymerization, physical vapor deposition (PVD) and chemical vapor deposition (CVD) have been applied to improve the thermal stability and mechanical sensitivity reduction of energetic crystals. The results show that the mechanical sensitivity and performances could be well-balanced in this way. This review summarizes the preparation methods and fundamental properties of coated/intercalated crystalline EMs. It demonstrates that the EMs with better performances could be made by appropriate modification methods, where the modified ammonium salts and nitramine crystals are presented as typical examples.