Nano scale energetic materials: Theoretical and experimental updates

Abstract

Recent advances in nanoscience are providing capabilities to fabricate materials with complex molecular patterns using various novel assembly approaches. This talk will summarize our current progress towards developing a framework of principles for design and fabrication of nano-tailored energetic materials for emerging applications. Nanoscale particles have a significantly higher surface area to volume ratio than microparticles, providing a closer contact between solid particles in a mixture. Kinetics of oxidation of metal nanoparticles acquired practical importance with rapidly developing nanoenergetic systems and materials. Nanoenergetic thermites include mixtures of Al and metal oxides in nanoscale. Our research focuses on modeling aluminum combustion in nanoscale. We consider oxidation in the spherically symmetric case, assuming that aluminum particle of radius 10 to 50 nm is covered by a thin oxide layer (1-4nm) and is surrounded by abundant amount of oxygen stored by oxidizers. The particle is rapidly heated up to ignition temperature to initiate self-sustaining oxidation reaction as a result of highly exothermic reaction. We use nonlinear Cabrera-Mott model with a self-consistent electric potential to compute oxidation reaction power (watts), as a function of temperature and oxidized metal proportion. Knowledge of such reaction power together with a self-heating model allows to predict oxidation time and reaction temperature dynamics. We compare modeling of self-heating based on matched experimentally known maximal reaction temperature with a detailed heat transfer model taking into account heat loss due to convection and radiation.