Enhancement of Friction by Water Intercalated between Graphene and Mica
mediaposted on 11.07.2017, 00:00 by Hyunsoo Lee, Jae-Hyeon Ko, Jin Sik Choi, Jin Heui Hwang, Yong-Hyun Kim, Miquel Salmeron, Jeong Young Park
Common experience shows that friction converts mechanical energy into heat. The first part of this process is vibrational excitation of atoms at the interface between rubbing bodies. The second part is the removal of the vibration energy by transferring it from the interface to the substrate. However, it is difficult to disentangle the excitation and energy transfer processes. We solved this by using a system consisting of a SiO2-terminated tip sliding over graphene deposited on mica with intercalated water between them. The intercalated water was found to increase friction by a factor of ∼3 relative to dry mica. Density functional theory calculations show that water broadens the spectral range of graphene vibrationsparticularly the low-frequency flexural modesthus providing new excitation channels and also by increasing the overlap with the atomic vibrations of the mica substrate, which facilitates coupling and energy transfer.