Investigation of the crystallization of RDX during spray drying

• RDX based nanocomposite microparticles were produced by spray drying.
• Detailed characterization of nanostructure sheds light on the crystallization of RDX.
• The crystallization begins with a rapid and massive nucleation in spray drying.
• The shell formation controls the size distribution of RDX crystals.
• This knowledge can be used for better size control of RDX crystals in spray drying.

Spray drying is a cost-effective and practical way of manufacturing nanoenergetic materials with novel properties. In this work, cyclotrimethylenetrinitramine (RDX)-based nanocomposite microparticles were prepared by spray drying. To understand the crystallization process during spray drying which is necessary for tailoring the high explosive crystal size, we characterized the nanostructure of the microparticles, which shows that: (1) the size of RDX crystals decreases radially across the microparticles from the center to surface, with RDX crystals on the surface generally within the range of hundreds of nanometers; (2) the droplet size has a considerable effect on the size distribution of RDX crystals in the microparticles; and (3) the binder is distributed uniformly inside the microparticles. The detailed characterization of the nanostructure of the microparticles sheds light on the crystallization of RDX during spray drying. The knowledge gained from this study can help improve the control of RDX crystal size during spray drying and enable achieving a material with near-optimal sensitivity and performance.

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