Double-droplet microfluidic strategy for preparing spherical core–shell structured explosives: controlling shell thickness to enhance safety performance

Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), as a high-performance explosive, is commonly used in military fields such as missile warheads, nuclear weapon charges, and solid rocket propellants. However, the high sensitivity of HMX limits its further applications. The versatility and controllability of core–shell structured explosives (CESs) can effectively achieve the modification research of energetic materials. Here, for the first time, we investigated the formation mechanism of HMX@DAAF core–shell microspheres through the double-droplet microfluidic strategy (DDMS) and successfully prepared core–shell microspheres with varying shell thicknesses according to this strategy. We explored the impact of the DAAF shell thickness on the morphology, structure, and performance of the core–shell microspheres and proposed a potential mechanism for the enhancement of safety performance of the core–shell microspheres. The results show that DDMS can produce HMX@DAAF core–shell microspheres with high sphericity, narrow particle size distribution, and good fluidity. The DAAF shell acts as a “shield” to protect the sensitive HMX inside, with its impact sensitivity and friction sensitivity increased to 100 J and 360 N, respectively. The study has demonstrated certain advantages in the tunability and structural construction of core–shell explosives, providing a simple and safe strategy for the preparation of high-quality core–shell structured materials.