Velocity dependent adhesion and friction in mesoscopic graphitic contacts in the super lubricity regime

events hall

Ms. Keren Stein MSc candidate

14.07.2022

David Wang Auditorium, 3rd floor Dalia Meidan Bldg.

14:30

Superior lubricants are crucial in all forms of mechanical systems, particularly in scaled-down systems, which have highly reactive surfaces. Atomistic friction is directly related to the periodicity of the atomic structure and the potential energy landscape between the sliding surfaces. The study of atomic-scale friction has enabled better understanding of friction and introduced a new phenomenon with the potential of revolutionizing lubricants: structural superlubricity (SSL).

In our experiments we sheared mesoscale graphite pillars using friction force microscopy (FFM), focusing on how the friction and adhesion forces are influenced by sliding velocities. In particular, we observe an increase in both friction and adhesion with increasing speed. Intriguingly, while the increase in friction can be rationalized by several existing models such as thermal lubricity, the observed change in adhesion, which is typically considered to be speed independent is rather unexpected.

In this seminar, I will describe the phenomena of SSL and how it is realized in vdW materials, such as graphite. I will further present fundamental models used to characterize atomistic friction, and discuss the relations that these models express between friction and sliding velocity, and relate our findings to these models. Finally, the dependence of the measured adhesion on velocity will be explained based on force field numeric simulations of the potential energy landscape.

BIO

B.Sc. from the faculty of Materials Science and Engineering, Technion

Supervisor: Asst. Prof. Elad Koren