Probing the Reaction Zone of Nanolaminates at ∼μs Time and ∼μm Spatial Resolution

Reactive
nanolaminates are a high-energy-density configuration
for energetics that have been widely studied for their tunable energy
release rates. In this study, we characterized Al/CuO nanolaminate
reactions with different fuel/oxidizer ratios and bilayer thicknesses
using both macro- and microscale high-speed imaging/pyrometry. Under
microscopic imaging, we observe significant corrugation (the ratio
of the total geometrical length of the flame to the width of the sample
in the direction perpendicular to propagation) of the flame, which
can increase the reaction surface area by as much as a factor of 3.
This in turn manifests itself as an increase in the global burn rate
(total nanolaminate film length/total burn time). We find that the
global burn rate can be predicted as the product of the microburn
rate (local vector burn rate at the microscopic scale) and the corrugation.
These corrugation effects primarily impact fuel-rich conditions, resulting
in higher global burn rates. We find that the reaction zone has a
thickness of ∼150 μm. Finally, we present a 3D rendering
of what we believe the reaction zone looks like, based on the results
from in-operando observation and SEM cross-sectional
imaging.