D. Mukherjee
University of Tennessee,
United States
Keywords: laser ablation synthesis in solution (LASiS), organic solvents, graphitic shell, Al nanoparticles, energetic nanocomposites
Summary:
The large heat release predicted in the early investigations of energetic aluminum nanoparticles (Al NPs) used in solid-state propulsion and pyrotechnics has been offset by hindered diffusion-limited oxidation rates due to excess oxide shell formations and surface area loss from aggregations. Tuning their energetic behaviors through tailored interfacial and metastable structures can effectively circumvent the unwanted oxide shell formation while promoting excessive internal stresses within the metallic cores. Yet, rational design and synthesis of such nanostructured architectures via non-equilibrium plasma-based synthesis routes remain challenging. We address this challenge through rational design and structure-property characterizations of graphitic shell coated Al NPs (< 20 nm sizes) dispersed in pyrolyzed carbon (C) matrices synthesized via high-energy reactive laser ablation synthesis in solution (r-LASiS). Herein, the C coated Al NPs facilitate their safe handling and promote enhanced activities due to the inherent advantages of the C shell retarding the metal NP aggregation while, upon ignition, burning into gaseous products (CO2, CO etc.) without any residual solid ash. Energetic activities of the C@Al shell-core NPs are confirmed from Laser-induced Air Shock from Energetic Materials (LASEM) measurements. Results indicate that LASiS parameters such as solvents, laser flux and ablation times allow superior control on the NP sizes/aggregation, composition, crystallinity, as well as their interfacial C structures which, in turn, tune their energetic behaviors. This work paves the way for tailored design of interfacial/metastable structures in composite ENMs that can exhibit either strain energy manifestation or, rate-controlled energy release under high pressure/temperature by bypassing the diffusion limitations from surface oxide passivation on metal NPs.