Reaction Behaviors of Al-ZnO System Ignited by High-Temperature Al Melt

In this work, a constant heat source, high-temperature Al melt, was used to fast ignite thermite reactions between Al and ZnO nanoparticles (ZnOnp). The effect of initial temperatures (Ti) on reaction behavior was emphasized to reveal underlying mechanisms. The results indicate that there were two reaction modes dependent on Ti, i.e., boundary diffusion and thermal explosion. Specifically, when Ti = 900 °C, the diffusion-assisted nucleation mechanism enabled small amounts of Al2O3 nanodispersions to form on Al powder surfaces. As Ti increased up to 1100 °C and above, self-sustaining combustion remarkably promoted the diffusion fluxes of Al and [O], resulting in almost instantaneous nucleation of Al2O3 throughout the whole region. Moreover, although in situ Al2O3 particles tend to sinter together under higher Ti, their limited growth could be attributed to evaporation and oxidization of the reduced [Zn] that consumed excess reaction enthalpy. Al2O3 particles uniformly dispersed in the aluminum matrix have been obtained by remelting and diluting the master alloy reacted at 1100 °C.