(712f) Combustion of Nanoscale Silicon with Polytetrafluoroethylene

Nanoscale silicon (nSi) based composite energetic materials have the capability to improve fuzes, initiation systems, and high radiant intensity applications. There are also advantages, including higher reaction temperatures and a thinner passivation layer, of using silicon as a replacement for nano-aluminum in many reactive compositions. While various oxidizers have been observed to show promising combustion behavior with nSi, the high heat of fluorination for Si/polytetrafluoroethylene (PTFE) combustion suggests that this system is of particular interest.

In this study, four nSi powders with varied specific surface area, oxygen content, and morphology were investigated and their combustion parameters compared. Specifically, three commercially available nSi powders and highly porous nano-silicon powder synthesized by a combustion synthesis method were studied. Reactive mixtures consisted of nSi, nano-featured PTFE, and FC-2175. Combustion experiments in ambient air were conducted to compare flame temperatures, spectral emissions, and deflagration rates. Visual and infrared spectrometers were used to analyze spectral emissions and determine grey body combustion temperatures. It was demonstrated that all investigated mixtures combust at 1 atm and depending on the nSi, the maximum combustion temperature varies from 2000 to 2600 K and burning rate varies from 0.6 to 1.7 mm/s.