An atomic-level insight in the transition from non-reactive to reactive wetting using molecular dynamics simulation

The intrinsic mechanisms that differentiate between non-reactive wetting and reactive wetting are still unclear. In this work, we have compared reactive and non-reactive wetting systems and made an attempt to explain the factors that contribute to the differences between these systems. In this aspect, we modeled five distinct wetting systems with different levels of reactivity between liquid Al droplet and solid Ni substrates. Results show that interfacial reactions during the reactive wetting cause a local increase of the temperature, a change in the droplet properties such as surface tension and self-diffusion, and in the overall substrate composition. This has led to a lower final contact angle and faster spreading rate, both of which point towards improved wettability due to the interfacial reactions. On the other hand, non-reactive wetting is dominated and controlled through the formation of a precursor film on the substrate. On tuning the reactivity, it was revealed that a competition between dissolution and precursor formation occurs where the former is more dominant with increasing reactivity. This study should aid in a better understanding of the wetting process and the atomic-level mechanism controlling the spreading behavior.