Process Research of Solution‐Enhanced Dispersion by Supercritical Fluids to Prepare Energetic Material Nano‐Capsules

Abstract

Nano‐capsule energetic materials can improve the mechanical properties, combustion/explosion properties, and component compatibility of solid propellants and reduce their toxicity, water absorption capacity, and sensitivity. The following approaches have been performed to obtain nano‐capsule energetic materials. First, the structure of solution‐enhanced dispersion by supercritical fluids (SEDS) core device (nozzle and hanging basket) were modified to improve the atomization performance, eliminate the vortex, and avoid the repeated growth of crystals. The ultrafine RDX particles with average particle size of 705 nm and distribution range of 400–1200 nm were prepared by using the improved devices. Second, the optimal process parameters for the preparation of ultrafine RDX by SEDS were obtained. Reducing the solution concentration or the supercritical CO2 temperature will be beneficial to obtain dry RDX particles with smaller particle sizes. When the solution concentration ratio was 10 g (RDX)/100 mL (DMF), the temperature of supercritical CO2 was 35 °C, and the flow rate ratio of supercritical CO2 to solution was greater than 10 (kg/h): 2 (ml/min), the experiment results were good. Third, to facilitate the detection of shell elements, fluororubber (F26) and RDX were used as raw materials to prepare nano‐capsules. Transmission electron microscopy image showed that the RDX‐F26 particles featured a core‐shell structure with diameters that ranged between 200 nm and 300 nm, spherical shape, and uniform wall thickness. The X‐ray photoelectron spectroscopy showed that the core was RDX, the shell was F26, and the thickness of the shell was 14.6 nm. As the capsule wall material, the F26 also inhibited the overgrowth of RDX crystal in the course of crystallization successfully. Sensitivity analysis showed that the RDX‐F26 nano‐capsules had lower impact and friction sensitivities than the refined RDX. These results show that the use of improved SEDS process is suitable for the preparation of energetic material microcapsules.

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