Controllable fabrication of binder-free co-crystal microspheres of CL-20 and TNT using 3D coaxial microfluidics

Abstract

The intrinsic conflict between elevated energy density and diminished sensitivity in energetic materials poses a considerable problem. Co-crystal engineering offers a promising solution, which is further enhanced by droplet microfluidics for producing homogenized microspheres. This study effectively generated binder-free 2,4,6,8,10,12-heanitro-2,4,6,8,10,12-hexaazaisowurtzitane/2,4,6-trinitrotoluene (CL-20/TNT) co-crystal microspheres (Mic) via a droplet microfluidic device, with oscillatory (Osc) and physical mixture (Mix) samples serving as controls. Under optimized conditions, Mic formed highly monodisperse spherical particles with a narrow size distribution (40~60 μm), excellent dispersibility, and outstanding flowability (angle of repose: 9°).Structural characterization confirmed the formation of a co-crystal structure in both Mic and Osc, while thermal analysis showed that Mic exhibited a delayed decomposition peak and higher thermal stability. Significantly, safety performance improved: the impact sensitivity of Mic was approximately 3.36 times greater than that of raw CL-20, while the friction sensitivity and explosion probability diminished by 56%. In conclusion, droplet microfluidics facilitates the creation of homogenous, binder-free co-crystal microspheres that exhibit improved thermal and mechanical stability, offering an innovative and efficient approach for the secure utilization of energetic materials.