Formation of flake-like DAAF crystals with tunable size realized on a microfluidic platform for binder-free initiator explosives

Abstract

Flake-like energetic crystal has a great potential to achieve initiator explosive with high reactivity, low initiation threshold, high safety, and facile post-processing, but it has been limited for 3,3′-diamino-4,4′-azoxyfurazan (DAAF) by the difficulties in controlling crystal morphology. Here reported is a microfluidic preparation of flake-like DAAF crystals (f-DAAF) with tunable size by combined effect of the adding of facet-controlling agent (nigrosin alcohol soluble) and tuning of the external crystallization conditions. The results show that the crystal system of f-DAAF belong to monoclinic system, the (−201) facet is the largest exposed face. The f-DAAF possess high crystallinity, tunable flake aspect ratio from 6.15 to 66.8 and specific surface area from 2.57 to 5.67 m2·g−1. Molecular dynamics simulations were performed to investigate the selective interactions between the two molecules (facet-controlling agent and solvent) and different crystal faces of DAAF in a real experiment environment. Combined with the experimental results, a possible growth mechanism of the flake-like morphology was discussed. It is found that the f-DAAF not only possess lower impact sensitivity itself, but also can reduce the impact sensitivity of other explosives with high impact sensitivity. The electric explosion derived flyer initiation experiments show that the initiation sensitivity of f-DAAF is much lower than that of raw DAAF in micron size, and comparable to that of ultrafine DAAF. This work demonstrates the promising application potential of f-DAAF as high-performance initiator explosives with low initiation threshold and high safety, and also provides an effective way for their preparation.