Initiation and ignition of nano-aluminum in Teflon

The combustion of nano-aluminum in Teflon was studied using time-resolved laser spectroscopy. This reactive material has a stored energy of ~21 kJ cm-3, nearly twice the energy content of the best molecular explosives. Experiments investigated the fundamental combustion processes of initiation and ignition. Initiation occurs when the first bonds break in the material. This step usually requires energy, but allows the material to undergo the widespread release of energy, known as ignition. These experiments used pulsed laser absorption to heat Al nanoparticles to ~3000 K in ~100 picoseconds. This activated the materials, allowing reactions to proceed. Initiation was studied by tracking changes in the vibrational band structure of Teflon using transient absorption of a femtosecond mid-IR laser pulse. Ignition was studied by analyzing the UV/visible burst of emission from flash-heated materials with an ultrafast streak camera detector. After flash-heating, hot Al attacked the surrounding Teflon, consuming CFO groups in ~50 ps. A confined Al plasma created by the laser registered the ~100 ps release of energy from the relaxation of nascent AlF, an elementary reaction product observed in the electronic ground-state within ~200 ps