Preparation and properties of HNS spherical agglomerates with hierarchical structures†

Spherical agglomeration is an important method for preparing multi-scale particles, especially large-sized particles. To address the issues of small particle size, irregular morphology, and poor flowability associated with existing HNS, the spherical agglomeration behavior of HNS in DMF-H₂O-DCM and DMF-H₂O-Tol solvent systems was systematically studied. The effects of crystallization temperature, the volume ratio of the bridging liquid to the solute (BSR), the volume ratio of the antisolvent to the solvent, the stirring rate, and other parameters on the agglomeration of HNS were determined. HNS spherical agglomerates with a size ranging from 476.28 μm to 886.12 μm were obtained by optimizing the crystallization parameters. The formation of HNS spherical agglomerates involves four processes: crystallization, phase separation, wetting, and adhesion. The agglomeration mechanism was also explained. A comparison of the flowability and combustion performance of spherical agglomerates and raw HNS crystals revealed that the angles of repose for S-HNS-I, S-HNS-II and raw HNS are 20°, 30° and 35°, respectively, while their pressurization rates are 89.21 kPa s⁻¹, 57.47 kPa s⁻¹, and 36.01 kPa s⁻¹, respectively. Spherical agglomerates exhibit enhanced flowability and excellent combustion performance compared with raw HNS. This study provides guidance for applying the spherical agglomeration method in the field of energetic materials.