Estimation of surface potential energy amplitude of Spinel catalyst from atomic friction force microscopy measurements

Ronen Berkovich, Chemical engineering, Ben Gurion University, Beer-Sheva, Israel
Liron Agmon, Chemical Engineering, Ben Gurion University, Beer-sheva, Israel
Itai Shahar, Chemical Engineering, Ben Gurion University, Beer-sheva, Israel
Danny Yosufov, Chemical Engineering, Ben Gurion University, Beer-sheva, Israel
Juergen Jopp, The Ilze Katz Institute For Nanoscience And Technology, Ben Gurion University, Beer-sheva, Israel

Friction is a phenomenon encountered in everyday life when two surfaces come into contact and move with respect to each other. This motion results with an irreversibly energy dissipation, which ranges from macro- (earthquakes, violin playing, machinery, etc.) to nano-scales (electronic devices, biological machinery etc.). One of the key features that characterize friction is the underlying interfacial interaction potential. Understanding the role of dissipation energy and surface potential in frictional mechanisms is essential for tribology, nanoscale fabrication, catalysis, adhesion and so on. To get an adequate estimation of the free energy landscape of an experimental system, high quality data is required. This necessity is met in measurements performed with Atomic Force Microscope (AFM). The AFM enables probing nanoscale frictional forces due to its ability to approach the single-asperity level, and measure the dynamical interaction between a sharp cantilever tip and the surface of interest, resulting with atomic stick-slip force pattern. Here we perform Friction force microscopy (FFM) experiments on NaCl in ethanol as a reference material, using the Prandtl-Tomlinson phenomenological framework to estimate the amplitude of the surface energy corrugation. The surface potential amplitude scales with the applied normal loads via a power-law dependency. This methodology was then extended to Spinel catalyst, which displayed higher surface energy than the NaCl crystal.