Constructing solid microspheres of CL-20/MTNP cocrystal via droplet microfluidic for improved performances

Abstract

The design and fabrication of materials with hierarchical structures has drawn great attention, due to the potential for significantly enhancing their functions. Herein, the droplet microfluidic technology was presented to construct binder-free microspheres of CL-20 (8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane) / MTNP (1-methyl-3,4,5-trinitropyrazole) cocrystal, an energetic cocrystal with excellent comprehensive performance. The effects of dispersed phase concentrations, continuous phase flow rates and surfactant concentrations in the continuous phase on the morphology and size of microspheres were studied by the experiments and computational fluid dynamics (CFD) simulations. The optimal parameters were determined under which solid cocrystal microspheres (D50=57.67 μm) with uniform particle size and high sphericity have been obtained demonstrated by scanning electron microscopy, infrared spectroscopy, infrared spectroscopy, Laser particle and laser scanning confocal microscope analyses. The dispersed concentrations mainly affect the crystallization process, while surfactant concentrations in the continuous phase have significantly influence on the droplet formation process. The as-prepared microspheres have high true density (1.8125 g·cm-³) and purity (99.6%), good flowability with an angle of repose of 22.2°, and improved mechanical sensitivity close to raw MTNP. This work not only presents a simple and convenient microfluidic method to fabricate solid microspheres of energetic cocrystals with enhanced performance, but also provides insight into the droplet formation process, promoting the further application of droplet microfluidic technology in energetic material field.