Research On The Wetting Properties Of Graphene Based On Molecular Dynamics Method

Due to its unique structure, graphene possesses remarkable mechanical, electronic, thermal and optical properties. As one of the important properties of solid surface, wettability refers to the ability of solid surface to maintain contact with liquid, resulting from intermolecular interactions when the two are brought together. Recently, many researches have been carried out to investigate the wetting properties of graphene film. However, it is still unclear that whether the graphene is hydrophilic or hydrophobic. In this thesis, the molecular dynamics method was adopted to investigate the behavior of water droplet deposited on the graphene film and the properties of graphene. Further, the effects of the temperature, the fluctuation and the charge density of graphene on the wetting results are also discussed.Firstly, a brief introduction of graphene favorable properties is given, along with the advances in the wettability researches and the fundamental principles of molecular dynamics.Secondly, the basic of wetting theories is recommended, containing the surface tension and free energy, wetting behaviors and classical wetting models. And the contact angle of water droplet on ideal graphene is obtained through theory analyses. Reviews on how to obtain the contact angle through experimental and numerical methods are also given.Thirdly, several models for studying the wetting properties of graphene are illustrated, along with the simulation process. The method for gaining the water contact angle from the simulation data is also specified.Finally, a variety of simulations are performed. Based on their results, the wettability of ideal graphene film is investigated at room temperature. Further, the effects of the temperature, the fluctuation and the charge density of graphene on the wetting results are also discussed from three aspects, namely the interaction energy of graphene and water droplet, the mass density of water and the water contact angle on graphene film. It can be concluded from the simulation results that the ideal graphene film is slightly hydrophobic and that both the temperature and the fluctuation of the graphene film play a negative role in the wetting process. The result also infers that once charged, the wetting property of graphene changes massively, from slightly hydrophobic to super-hydrophilic. It can also be deduced that the rise of charge density of graphene accelerates the wetting progress and the positive charges function a little favorable than the negetive ones.In this thesis, the wetting properties of graphene is investigated using molecular dynamics method, the result of which can provide some useful references to the preparation and other applications of graphene.