Insights into combustion mechanisms of variable aluminum-based iron oxide/-hydroxide nanothermites

Aluminum/iron oxide/-hydroxide nanothermite compounds were prepared and investigated in detail. The fast and facile synthesis was undertaken via a coprecipitation route of iron precursor species (sulfate, chloride) in presence of aluminum nanoparticles with an average diameter of 100 nm, terminated by an amorphous Al2O3 passivation layer. The only difference during synthesis is temperature, leading to a non-magnetic (at 20 °C) and magnetic (at 50 °C) nanothermite. HR-TEM and XRPD analysis reveal a predominantly amorphous iron oxide/-hydroxide nanoscaled matrix surrounding the aluminum nanoparticles. Moreover, aluminum nanoparticles and nanoscaled iron oxide/-hydroxide build up a hierarchical Al/Al2O3/FexOyHz core/shell/shell structure in the case of the magnetic nanothermite. The non-magnetic nanothermite system lacks this significant structure. Finally, as-synthesized systems highly differ in reactivity, which is explained by their individual structural discrepancies. Values of flame propagation velocities and distinct threshold values of sensitivity to electrostatic discharge align with comparable reported aluminum/iron oxide aero- and xerogels in the literature.