▎ 摘　　要

In this article, molecular dynamic simulation was used to simulate the wetting process of graphene oxide coated alumina substrate. By changing the density of hydroxyl and epoxy groups on the surface of gra-phene oxide, the influence mechanism of two functional groups on the wetting process of water mole-cules was explored. From the simulation results, the increase of hydroxyl density can enhance the wettability of the substrate and reduce the wettability angle from 64.32 degrees to 54.20 degrees. By calculating the for-mation of the hydrogen bond in the wetting process, it is found that hydroxyl can significantly raise the hydrogen bond lifetime in the system. This increasing effect is particularly prominent in the observation of the hydrogen bond between water molecules and graphene oxide. The hydrogen bond lifetime increases from 2.20 ps to 12.77 ps. The result also reflects the reason why hydroxyl increases the wetta-bility of the substrate. In addition, the increase of hydroxyl density also brings changes in hydrogen bond behavior and the number of hydrogen bonds. Under the condition of high epoxy density, most of the hydrogen bonds between water molecules and the substrate exist in the form of single hydrogen bonds, and the number is small. When the hydroxyl density increases, double-hydrogen bond, triple-hydrogen bond and single hydrogen bond appear in the model. In this process, the number of hydrogen bonds between the water droplet and the substrate is also increasing. Temperature is an important influence on the formation and lifetime of the hydrogen bond. High temperatures can promote the formation of the hydrogen bond between alumina and water molecules. In addition, it can also decrease the lifetime of all types of hydrogen bonds. Through the free energy perturbation theory, we get the free energy of different models in the wetting process. The results show that high hydroxyl density can improve the free energy of the wetting process, reduce the ability of spontaneous desorption and increase the stability of wetting. High temperatures can reduce the free energy and lead to the occurrence of desorption behavior. This article reveals the wetting mechanism of water molecules on graphene oxide coated alumina sub-strate, mainly reveals the influence of hydrogen bond and the change of free energy in the wetting pro-cess, which lays a theoretical foundation for the application of graphene oxide wetted coating on the aluminum alloy surface.(c) 2022 Elsevier B.V. All rights reserved.