Probing the Reaction Dynamics of Thermite Nanolaminates
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Abstract
Al/CuO
reactive nanolaminate ignition was studied using temperature
jump (T-Jump) heating for rates greater than 10<sup>5</sup> K/s. Multilayer
samples were sputter deposited onto thin platinum filaments in alternating
layers of Al and CuO. The filaments were resistively heated in a time-of-flight
mass spectrometer (ToF-MS), while ignition and reaction were observed
with high-speed video. A total deposited thickness of 1800 nm was
maintained for all samples, while the number of bilayers was varied
from 1 to 12. Increasing this value decreased the diffusion distances
and increased the amount of interfacial area across which reaction
could occur, while keeping the overall energy of the system constant.
From 2 to 6 bilayers, the ignition temperature decreased from 1250
to 670 K and the overall reactivity increased. Past 6 bilayers, the
ignition temperature only decreased slightly and there was little
impact on the overall reactivity. This behavior is consistent with
a mass-transport model where the predominant diffusing species exhibits
a low activation energy (50 kJ/mol). Ignition temperature, which depends
upon bilayer thickness, is found to be a good predictor of flame speed