Formation of Flake-Like Daaf Crystals with Tunable Size Realized on a Microfluidic Platform for Binder-Free Initiator Explosives

Abstract

Flake-like energetic crystals has a great potential to achieve initiator explosives with high reactivity, low initiation threshold, 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 turning of the external crystallization conditions. The results show that the crystal system of f-DAAF is monoclinic system, the (-201) face is the largest exposed face. The f-DAAF possess high crystallinity and tunable flake aspect ratio from 6.15 to 66.8, and high specific surface are 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. Combine with experimental results, a possible growth-dissolution competition mechanism was proposed to understand the source of flake-like morphology. 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 the f-DAAF as high-performance insensitive initiator explosives and also provides an effective way for its preparation.

Keywords: Microfluidic preparation, crystal morphology regulation, formation mechanism, low initiation threshold, flake-like DAAF.