2, U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland, United States
Metal nanoparticles (NPs) specifically Al NPs, have been prominently featured over the years as energetic nanomaterials in the development of solid-state propellants, explosives and pyrotechnics. The promise of such materials has always resided on the kinetically controlled ignition processes in nanoscale regimes due to large specific surface areas, and small diffusion length scales at fuel-oxidizer interfaces. Yet, the reality of a rapidly growing passive oxide shells on NP surfaces has resulted in their performance being largely diffusion-limited thereby eluding the much-anticipated high detonation rates in the past. To overcome this challenge, herein we report the synthesis and characterization of metallic nanoparticles and specifically, Al NPs coated with graphitic shells in our effort to preserve the solid fuel surface from excessive oxidation while allowing heat conduction through the graphitic shells. Specifically, we use our recently developed laser ablation synthesis in solution (LASiS) technique to synthesize Al NP/Graphite core-shell structures by ablating an Al target in various organic solvents (acetone, toluene, ethanol). The structural and crystalline properties of the synthesized metallic Al NP core were measured and compared using Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD). Finally, using Laser-induced Air Shock from Energetic Materials (LASEM) method, the detonation performance of these materials were measured and compared to commercially available solid fuels in order to tailor the interfacial functionalities of these shell-core nanometallic energetic materials.