Aluminum nanoenergetic materials have emerged as promising propellants and fuel additives in civilian and defense-related applications. The native oxide shell on the surface of aluminum nanoparticles (Al NPs) provides passivation during storage and forms a diffusion barrier for oxygen and Al contact that inhibits oxidation during combustion. For nanoparticles, the oxide layer occupies a significant fraction of the particle's mass that adds weight but does not contribute to its energy content. This work demonstrates a perfluoro-based non-thermal plasma process to prepare core/shell nanostructures of Al with significantly improved energy release. The native oxide layer reacts with a fluorocarbon-based plasma film formed on the surface using plasma-enhanced chemical vapor deposition (PECVD) of perfluorodecalin (C10F18). This reaction forms porous AlF3 that provides new reaction channels for the oxidation of Al in the core, thus enhancing the energy release by ~50% and oxidation efficiency by ~19% as illustrated by thermal analysis measurements. Characterization of core/shell nanostructures was performed using various methods. TGA/DSC combined with TEM, was used to determine the plasma film's optimum thickness (~10 nm) that maximizes the energy release (~50%). TEM and STEM-EDS in HAADF demonstrated uniformity and distribution of the surface plasma films. XRD and XPS analyses characterize the respective phases and the chemical bonds present in the plasma films. The combined picture formed from these results is used to explain the mechanism of the interfacial reactions between plasma films and the native oxide, leading to energy release enhancement. This concept of eliminating the surface oxide layer and enhancing the energy release by triggering surface fluorination reactions during thermal oxidation can be applied to the cutting-edge design of metal-based nanoenergetic systems.

Effect of perfluoro-based plasma-enhanced chemical vapor deposition on nanoenergetics of aluminum particles

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.