Pre-burning Characterization of Nanosized Aluminum in Condensed Energetic Systems

Nano-sized aluminum (nAl) particles have several features that make them interesting for energetic applications. Compared to micron-sized aluminum (μAl) higher reactivity, lower ignition temperature and condensed combustion products of reduced size can be achieved. This work focuses on the pre-burning characterization of nAl. In the analysis, different features of various powders (passivated by air or organic compounds, and eventually coated by hydrocarbons and fluorohydrocarbons) are investigated focusing on the application in energetic systems. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), specific surface area (SSA) measurement, and volumetric techniques are considered for an extensive characterization of the powder morphology (particle size, shape, and texture), structure, and composition (active metal content). The reactivity of nAl is investigated at low- and high-heating rates. The behavior of powder suspensions is analyzed by a plate-plate rheometer considering hydroxyl-terminated polybutadiene (HTPB) as the suspending medium. The effects of the nAl passivation/coating layer on the viscosity of HTPB-based slurries are discussed. This information is crucial for an effective evaluation of the nanomaterial dispersion in the HTPB matrix and for the identification of possible limitations in the propellant/fuel manufacturing process. The presented results enable a comprehensive understanding of the relationships between nanosized additives morphology/structure, oxidative reactivity, and propellant/fuel rheological behavior