Kinetics and Mechanism of Ignition in Reactive Al/Ni Nanostructured Materials

A high-speed electrothermography approach is applied to investigate the mechanism and kinetics for nanostructured Al/Ni foils. Application of the Kolmogorov-Johnson-Mehl-Avrami and adiabatic thermal explosion models reveal that the activation energy for nucleation appears to be much higher than that for reaction. It is shown that formation of intermetallic nuclei is the limiting step that defines the ignition characteristics of the foils at temperatures below 500 K, while the process is reaction limited at higher temperatures. Nucleation is also shown to play an important role during rapid (~10 m/s) propagation of the combustion (reaction) wave along the Al/Ni foils. These findings suggest new approaches for controlling the ignition and combustion processes for nanostructured reactive materials.