Nano Engineered Energetic Materials (NEEM)

Abstract

Abstract : The ARO Nano Engineered Energetic Materials (NEEM) MURI program has been exploring new methodologies for developing energetic material formulations with control of all constituents over a wide range of length scales from 1 nm to 1 mm and larger and employing the latest techniques in molecular self-assembly and supramolecular chemistry for synthesizing and assembling NEEMs. The synthetic efforts have been guided by theoretical calculations and dynamic performance testing methodologies that also operate on all length scales. This final report provides a summary of the accomplishments. In particular, new methods to generate metal nanoclusters were developed that are stabilized against environmental degradation while preserving their high energy content. Rapid expansion supercritical solution processes were developed and applied to synthesize nanosized particulate oxidizers and energetic oxidizer shell/fuel core composites. Surface science and experimental chemistry methods were applied to study the structures and energy releasing reaction pathways of NEEMs. Unique diagnostic capabilities were developed and applied to study the fundamental mechanisms that underlie NEEM dynamic performance. Combustion mechanisms of various NEEMs, including nanothermites and nanoparticulate fuel/liquid oxidizer systems, were experimentally analyzed. The reactive and thermal characteristics of NEEMs were studied using large (billion atoms) multiscale simulations that couple quantum-mechanical calculations to molecular dynamics calculations. In particular, the stability, structure and energetics of metallic nanoparticles with a special focus on the relationships between particle size, shape and excess surface free energy were studied. A unified theory of ignition and combustion of aluminum particles for a wide range of sizes, from nano to meso scales was established.