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• A versatile microreaction system for handling high-solid-content fluids was set up. • The stability of fluids with Zr powder was investigated by UV–vis spectroscopy. • The surface reaction mechanism of Zr powder based on HF concentration was proposed. • The contradiction between the activity and sensitivity of Zr powder was reconciled. The regulation of energy release characteristics and safety of highly active metal fuels has attracted significant attention. In response to the limitations of using hydrofluoric acid (HF) to modify zirconium (Zr) powder in batch reactors, a microfluidic method coupling ultrasound and coaxial flow microreactors was proposed to achieve the control of the microstructure on the surface of Zr powder. The fluid flow and mixing characteristics in the microreactor were analyzed using on-line detection devices, leading to the determination of suitable fluid parameters. Through analysis of the reaction process between Zr and HF, a reaction model based on the HF concentration was established and subsequently verified through a microreaction system. The results indicate that the HF concentration greatly influences the morphology and composition of Zr powder, thereby determining the material and structural transformation of the Zr powder surface. The excellent thermal oxidation performance and electrostatic safety of HF-modified Zr powder were confirmed through thermal analysis and electrostatic discharge sensitivity tests. This study provides valuable insights for controlling the microstructure and properties of ultrafine Zr powder. [ABSTRACT FROM AUTHOR]

Spherical explosives had regular shape and smooth surface, which gave them low sensitivity, excellent flowability, and high bulk density, thereby yield good charging performance. Traditional spherization methods always resulted in irregular shape, low sphericity, and uneven size. In this paper, a novel droplet microfluidic technology was used to fabricate hexanitrostilbene (HNS) microspherical with nitrocellulose (NC) as adhesive. The farication process (e. g., HNS concentration, NC concentration, flow rate) was fully investigated in pursuing for the ideal farication condition. The chemical structures, crystalline structures, and thermal stability of HNS were preserved. Meanwhile, the flowability and bulk density of HNS microspheres were significantly improved (Repose angle: HNS microsphere vs raw HNS, 33.1 vs 39.2°; bulk density: HNS microsphere vs raw HNS, 0.466 vs 0.301 g cm−3), which enhanced the charging and pressing performance of HNS. Unlabelled Image • Droplet microfluidics was firstly used for the spheroidization of HNS. • HNS microspheres with arrow size distribution were successfully synthesized. • The flowability of HNS microspheres were superior to that of raw HNS. • This work provided a novel method for the spheroidization of explosives. [ABSTRACT FROM AUTHOR]