Non-Isothermal Dissolutive Wetting of Al-Ni and Cu-Ni Alloy Nanodroplets on a Cu(100)Substrate

The kinetics of Al-Ni and Cu-Ni nanodroplets spreading over a Cu substrate in the presence of a temperature difference between them is studied via molecular dynamics simulations.The simulations show that significant dissolution reactions occur for the two systems and there is no precursor film generated during spreading.The spreading rate significantly increases when nanodroplets contain less Ni atoms in the Al-Ni/Cu wetting systems.However,a different trend is observed in the Cu-Ni/Cu wetting systems.The spreading rate remains unchanged regardless of the ratio of Cu to Ni atoms owing to the fact that Cu and Ni have almost the same lattice constants.The simulations also demonstrate that,because of the temperature gradient between the nanodroplet and substrate,local solidification takes place in the later spreading stage,which significantly hinders spreading.Due to the mismatch of lattice constants between Al and the Cu atoms in the Al-Ni/Cu wetting systems,hexagonal closest packed(hcp),body centered cubic(bcc),and face centered cubic(fcc)arrangements of atoms are observed when the Al-Ni nanodroplets solidify completely,whereas there is only a fcc arrangement in the Cu-Ni/Cu wetting systems.