(247d) Challenges in Processing of Aluminum and Metal Oxide Nanopowders in Water

In recent years, the scaling of reactant powders down to the nanoscale level has allowed for much advancement in the area of energetic materials. The nanoscale size of individual particles results in much higher surface area and allows for more intimate mixing of the reactant components in a heterogeneous system. Because of the higher surface area and intimate mixing of reactants, nanoenergetic systems have reaction rates that are several orders of magnitude faster than systems comprised of micron scale reactants. These nanoenergetic mixtures have already found application in lead-free electric matches, lead-free percussion primers and as additives to high explosives, however the safe and efficient processing of these nanopowders is still not optimal. One of the means of increasing the safety of processing of these nanoenergatic is to process these powders in water. This study has been focused on surface functionalization of aluminum nanopowder for its processing in liquid water. Degree of intermixing of the reactants in the heterogeneous system was also investigated by using various modifiers and surfactants in order to improve nanopowder dispersion in water as well as to reduce the effect of stratification and settling of different densities nanopowders during and after mixing. Several methods were used to characterize individual reactants and mixtures used in these studies. The methods include BET specific surface area, scanning electron microscopy (SEM) and transmitting electron microscopy (TEM), thermal gravimetric analysis (TGA), and volumetric determination of reactive metal content. Drop ball test equipment was also used to determine the impact sensitivity of the nanoeergatic powders. Susceptibilities of the system to ignition by thermal impulses and/or electrostatic discharge (ESD) are other factors that were considered and investigated in these studies.