Thermal characterization and kinetic analysis of nano‐ and micro‐Al/NiO thermites: Combined experimental and molecular dynamics simulation study

Abstract

In the experimental part of this study, thermal properties of the Al and NiO composites in micro‐ and nano‐sized Al are investigated. Differential scanning calorimetry (DSC) analysis of the onset temperatures of ignition, activation energy (Ea), frequency factor (A), rate constant (k), critical ignition temperature of thermal explosion (Tb), and self‐accelerating decomposition temperature (TSADT), as well as the thermodynamic parameters (ΔS≠, ΔH≠, and ΔG≠) are used to explore the thermal behavior and analyze the kinetics. Thermal analysis suggests that the mechanism is based on solid–solid diffusion and liquid–gas for the nano‐ and micro‐Al/NiO composite, respectively. Our results indicate that the incorporation of nano‐Al particles can significantly reduce the ignition temperature, Ea, A, k, Tb, and TSADT. In the second part of this work, molecular dynamics (MD) simulation is used to investigate the behavior of Al/NiO thermite reaction using the Reaxff force field to evaluate the experimental results. Theoretically, MD results show 1,154 K as the reaction ignition temperature, which is in reasonably good agreement with experimental temperature of 893°C (1,166 K). The radial distribution function (RDF) shows that no reaction occurs at 500 K but it is complete at 1,200 K.