Photoflash and laser ignition of full density nano-aluminum PVDF films

• Published in: Combustion and flame 2021-11, Vol.233, p.111570, Article 111570
• Main Authors: Uhlenhake, Kyle E., Olsen, Daniel, Gomez, Mateo, Örnek, Metin, Zhou, Min, Son, Steven F.
• Format: Article
• Language: English
• Subjects: Aluminum; Broadband; Carbon nanotubes; Combustion modeling; Energetic materials; Energy absorption; Fluorides; Ignition systems; Laser beam heating; Laser ignition; Lasers; Low density materials; Nal-PVDF composite; Neodymium lasers; Optically sensitive; Oxidizing agents; Particle interactions; Photoflash ignition; Photosensitivity; Polyvinylidene fluorides; Porous materials; Semiconductor lasers; YAG lasers
• ISSN: 0010-2180; 1556-2921
• DOI: 10.1016/j.combustflame.2021.111570

Laser or flash excitation is an attractive ignition option for many energetic systems because of increased safety and control. Commonly used electrical ignition systems are more likely to cause accidental ignition due to stray currents. Upgrading to laser or flash ignition mitigates this problem as well as allowing the ignition at multiple sites more easily for improved control of the energy release. Carbon nanotubes and nanoscale aluminum have been shown to be flash ignitable in loose powders or very porous low-density materials; however, these previous low-density formulations may not be as useful in practical energetic systems. In this study, nano aluminum particles are combined with a polyvinylidene fluoride binder/oxidizer in order to create a full-density photosensitive material. Using a low energy broadband flash source and an Nd:YAG laser at 1064 and 532 nm, films of nano aluminum and polyvinylidene fluoride were successfully ignited experimentally and ignition response was quantified. Solids loading was found to be the dominating factor controlling minimum ignition energies, with the lowest energies observed at 20 to 25 wt.% nAl. Simulations of the wave and particle interactions were modeled with COMSOL Multiphysics® for both the flash and laser-induced heating. The results show that optimal energy absorption occurs at nAl particle fractions of 20–25 wt.%, consistent with the experimental observation. Additionally, the results show the effect of plasmonic resonant enhancement of the heating, specifically at lower wavelengths near 250 nm.