Hazard Characterization of Uncoated and Coated Aluminium Nanopowder Compositions

The thermal properties of various uncoated and coated aluminum nanopowders and their effects on the thermal stability, outgassing behavior, and electrostatic discharge sensitiveness of various energetic materials were studied. These aluminum nanopowders had a mean particle size of 20-120 nm. The coated samples had a layer of 7-25% mass of polymer. The thermal behavior of the aluminum nanopowders in air was determined, and the effects of the particle size and the coating on the reactivity of aluminum nanopowders are discussed. Aluminium nanopowders are very reactive in the presence of water, resulting in aging problems. The coating of polymer has a minor effect on the reactivity of aluminum nanopowders with water. On the other hand, the results from an aging study show that the coated aluminum nanopowder is more stable than the uncoated nanopowder in humid atmospheres. The addition of some coated aluminum nanopowders lowers the onset temperatures of cyclotrimethylenetrinitramine, trinitrotoluene, and glycidyl azide polymer by ∼20°C. Outgassing results obtained for various cyclotrimethylenetrinitramine/aluminum mixtures at 100° C show that the uncoated Al120 enhances the low-temperature solid-phase decomposition of cyclotrimethylenetrinitramine. The addition of uncoated aluminum nanopowders has previously been shown to increase the electrostatic discharge sensitiveness of both ammonium dinitramide and ammonium perchlorate to ignition energies that can easily be carried by a human body. In contrast, the coated aluminum nanopowders do not appear to sensitize ammonium dinitramide and ammonium perchlorate toward electrostatic discharge, which suggests that the coatings can effectively prevent the sensitization effect.