Ab initio molecular dynamics studies on the ignition and combustion mechanisms, twice exothermic characteristics, and mass transport properties of Al/NiO nanothermite

Abstract

Ab initio molecular dynamics was used to simulate the ignition and combustion reaction process of the Al/NiO nanothermite. The exothermic characteristics and the role of oxygen migration in the whole reaction were disclosed. The results suggest that the primary and secondary heat release are mainly caused by the interfacial and bulk thermite reaction, respectively. The interfacial oxygen migration and the breaking of Ni–O bonds cause the initial ignition. The destruction of the bulk NiO lattice is the precursor process of the secondary heat release and retards the rapid thermite reaction. The 18O isotope leads to a lower oxygen mass transport rate, having a great influence on the ignition delay time and reaction progress. The metal–oxygen flip mechanism ensures the continuous propagation of the thermite reaction. Our work may be helpful for understanding the reaction mechanisms of the metal/metal oxide thermites and optimizing the formulation design and performance of the nanothermites.