Mechanisms of oxide growth during the combustion of Al:Zr nanolaminate foils

Reactive metal nanolaminates, most notably aluminum/zirconium composites, have been developed as fuels to aid combustion in explosive formulations. Thus far, however, their energy density is limited by incomplete oxidation. An in situ x-ray diffraction (XRD) study was performed on a 40 µm thick Al:Zr (atomic ratio 1:1) multilayer foil to track the growth of reaction products during ignition, combustion, and cooling (over approximately 5 s) to determine the mechanisms that prevent complete combustion from occurring. Simultaneous pyrometry provides the ability to relate the observed phase progression to the foil temperature throughout the reaction, and post-reaction cross-sectional electron microprobe and transmission electron microscopy (TEM) of the combusted foils identify the location, composition, and microstructure of each product phase.