High-yield spray drying assembly and reactive properties of nanoenergetic mesoparticle composites

Abstract

Electrospray has been demonstrated to assemble fuel and oxidizer nanoparticles with a gas-generating binder into microscale particle composites. This approach results in reactivity enhancement of nanothermite systems by alleviating reactive sintering of the nanoparticle components due to rapid gasification. However, this method is not readily scalable and amenable to large-scale manufacturing due to its slow solution processing rates and the risks associated with the presence of high electric fields in the presence of electrostatic discharge-sensitive reactive materials. Here, we explore spray drying as an alternative approach to assemble Al/CuO nanoparticles into nitrocellulose (NC)-based mesoparticle composites and evaluate their energetic performance against physically mixed powders and electrosprayed mesoparticles. The spray dried mesoparticles show ∼2–7-fold higher pressurization rates and shorter burn times than their physically mixed counterparts and follow a similar trend with electrospray. The higher reactivity of the mesoparticles is attributed to rapid gas generation and reduced sintering from the decomposition of the NC binder. We further demonstrate that spray drying generates mesoparticles with size (∼1.5–4 μm), morphology, and reactivity enhancement similar to that from the electrospray method, while achieving remarkably high production rates (as high as ∼275 g h−1). Thus, this work presents spray drying as a highly scalable strategy to achieve reactivity enhancement and processability, thereby enabling high-yield manufacturing of energetic materials, which is a prelude to what might evolve into 3-D printing approaches for propellants.