Highly energetic formulations of boron and polytetrafluoroethylene for improved ignition and oxidative heat release

Abstract

Boron (B) is desirable for energetic applications due to high gravimetric and volumetric energy densities. However, their use is limited because the native oxide shells on their surfaces limit oxidation and heat release by acting as a diffusion barrier and dead weight that does not contribute to heat release during oxidation. This paper reports a facile and efficient method of blending B with perfluoro additives to obtain materials with augmented heat release. We use polytetrafluoroethylene (PTFE) as a fluorine source that reacts with the oxide layer exothermally and use thermochemical analysis to identify the optimum composition of PTFE to extract high energy from B as a result of synergistic oxidation and fluorination reactions. The reduction in ignition temperatures of B is also observed due to its blending with PTFE. In this work, we determined B/PTFE blends with lower ignition temperature and higher oxidative heat release. These effects are due to the gasification of native surface oxide by fluorine via exothermic reactions that facilitate the enhanced reactions in the exposed metal core by eliminating the kinetic/thermodynamic barrier in the diffusion of the oxidizer to the B particle core. The study demonstrates the optimized formulation of highly energetic blends of B/PTFE for energetic applications.