Department of Mechanical and Nuclear Engineering, Pennsylvania State University University Park
The Smart Functional Nanoenergetic Materials MURI program explored new methodologies for development of macroscale micron-sized or larger composite energetic materials with nanoscale features that provide improved performance over nanoscale particles and ease of processing and handling, managed energy release, reduced sensitivity, and potential for internalexternal control and actuation. The reactivity and thermal decomposition of nanostructured materials including FGS-tetrazine compounds, encapsulated nanocatalysts in energetic oxidizers, metal alloy particles, mesoscopic aggregates, and aluminum clusters were analyzed along with their combustion performance in liquid and solid composite propellants. Molecular dynamics simulations were performed to understand the decomposition and reactivity of the nanostructured materials and their heat transfer properties in liquid suspensions and gaseous environments. The development of both model systems and new synthesis processes for functionalized graphene sheets FGS-tetrazine compounds, Al and Pt nanoparticles on FGS, metallic Al clusters and mesoscopic aggregates, nanoscale inclusion materials, and encapsulated nanocatalysts in energetic oxidizers were accomplished. Assembling nanoparticles into a microparticle with an embedded gas generator was demonstrated to lead to enhanced combustion, a more consistent burn from particleto-particle, and mesoparticles that burn like independent Al nanoparticles. Nanoconfinement was found responsible for accelerating the decomposition of tetrazines linked to multilayers of FGSs upon rapid heating. The replacement of Al with Al-Li alloy in composite propellants was found to drastically reduce formation of HCl in the products and theoretically increase specific impulse. Theoretical models for the effective thermal conductivity of energetic nanomaterials and the thermal decomposition of hydroxylammonium nitrate and ammonia borane were developed.