Novel Pyrophoric Substrates with a Tunable Energetic Output

Highly porous alpha-iron nanoparticles generate a temperature response greater than 900^oC when exposed to ambient air. Porous iron foils are currently used for infrared (IR) decoys for low flying aircraft. An environmentally friendly process and a material for which the pyrophoric response can be easily tuned are highly desirable. Porous self supporting substrates were fabricated by dispersing carbon nanotubes or nanofibers in water followed by vacuum filtration. Several different substrate configurations were tested including: carbon layer-iron oxide nanoparticle layer, carbon-iron oxide nanoparticle-carbon, and graded (e.g. carbon-carbon/iron oxide nanoparticle-carbon). The carbon/iron oxide nanoparticle porous self supporting substrates were subsequently reduced under hydrogen at temperatures between 350-550^oC. The pyrophoric response of the porous self-supporting substrates can be tuned by adjusting the ratio of iron to carbon and/or the addition of other reactive materials to the mixture. It was observed that the carbon material used in the fabrication of porous substrates has a significant effect on the surface temperature of the substrate when exposed to ambient air. The experimental results detailing the effect of iron concentration and the addition of fuels on the surface temperature of a pyrophoric substrate when exposed to ambient air will be presented. The experimental results will be compared to a predicted temperature response from a mathematical model based on measured oxidation reaction kinetics for iron nanoparticles.