(189ch) Atomistic Simulation of Sliding Friction between Two Silicon-Carbide Surfaces

Sliding friction between two SiC surfaces is important due to its applications to high performance disc brakes, cutting tools, and blades in gas turbines and jet engines, in addition to its traditional applications in the semiconductor industry. It is also important to study whether at the nanoscale the dependence of kinetic friction on sliding velocity follows Stokes' law. Since SiC exists both as an amorphous material and with a crystalline structure, the effect of surface roughness on the kinetic friction is also of importance. We report the results of extensive molecular dynamics simulation of sliding friction between surfaces of the two types of SiC over a wide range of sliding velocities. The amorphous SiC was generated by the reactive force field ReaxFF, which was also used for the friction simulations. The kinetic friction was computed by averaging the instantaneous friction force over sufficiently long distances. A normal force of 500 MPa was applied to the system, maintained at 300 K, and was used to determine the friction coefficient. At very low velocities, we find that Stoke's law is observed. At much higher velocities, however, there is a marked drop in the friction coefficient for both amorphous and crystalline SiC. For all the velocities, amorphous SiC exhibited a significantly higher friction coefficient. The nature of stick/slip conditions at varying velocities rests at the heart of this study, and has been investigated in detail.