The Wetting And Coalescence Of Liquid Metal On Carbon Nano Substrate

Wettability and coalescence are common in nature and our daily life.The coalescence of liquid fluids is a key process relevant with raindrops formation in clouds,low energy fusion of atomic nuclei and self-cleaning of leaves.The coalescence of two spreading droplets on a carbon substrate is a key process relevant with industrial applications.In the case of metallurgy industry,the coalescence rate of neighboring drops also plays a vital role in determining the metallurgical quality and yield.The heterogeneous coalescence is relevant to a wide variety of fields,ranging from welding and casting manufacturing to metallurgy industry.For instance,practical applications of the heterogeneous coalescence are found in the welding industry that require joining of different metals because the heterogeneous coalescence of high-temperature liquid metal can affect the structure and properties of the weld line.So far,this phenomenon remains largely unexplored.This study can provide the theoretical guidance on the coalescence,and also on the new and promising applications.In this work,molecular dynamics(MD)simulations are used to study how the droplet geometry and substrate structure influence the coalescence and further discover the early-time coalescence dynamics of the spreading of Au drops.We carry out molecule dynamics simulations to study the heterogeneous coalescence of metal drop on nano substrate.The main results are as follows:(1)By using molecular dynamics simulation,we investigate the drop formation of liquid Au on nano carbon substrates.The simulation results clearly show that the drop formation is affected by not only the drop shape but also the surface structure of substrate due to the different diffusions along x and y directions on different substrates.The complex drop forming process of liquid films is mainly attributed to the combinative motions competitions between contraction and growth of the bridge.(2)In the case of pillared graphene substrates,the unexpected detachment of Au drops is observed due to the dewettability.Furthermore,we confirm that the minimum height of the growing meniscus bridge between the two droplets exhibits power-law behavior,increasing at early time as tk,which indicates that the growing dynamic of the bridge exhibits self-similarity at the early stage of coalescence.The rescaled profiles at different time collapse onto a universal curve which means that the system is governed by a single length scale during the inertial stage of coalescence.Our results reveal that at early stage,the bridge of drops develops a self-similar shape and the height h0 is the only relevant scale.(3)Molecular dynamics simulation has been performed to study the asymmetric coalescence of heterogeneous liquid metal on graphene.Simulation results show that the anomalies in the drop coalescence is mainly caused by the wettability of heterogeneous liquid metal.The silver atoms incline to distribute on the outer layer of the gold and copper droplets,revealing that the structure is determined by the interaction between different metal atoms.The coalescence and fusion of heterogeneous liquid metal drop can be predicted by comparing the wettability and the atomic mass of metallic liquid drops,which has important implications in the industrial application such as ink-jet printing and metallurgy.