Sliding friction between two silicon-carbide surfaces

Sliding friction between two SiC surfaces is important due to its relevance to many practical applications. It is also important to study whether kinetic friction at the nanoscale follows Coulomb’s law. Since SiC exists both as an amorphous material and with a crystalline structure, the effect of surface roughness on the kinetic friction may also be significant. We report the results of an 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 to represent the interaction potential for the simulation of sliding friction. As the sliding velocity increases, bond breaking occurs at the interface between the two surfaces, leading to their roughening and formation of excess free volume. They reduce the kinetic friction force, hence resulting in decreasing the difference between kinetic friction in the amorphous and crystalline surfaces. The average kinetic friction force depends nonlinearly on the sliding velocity V, implying that Coulomb’s law of friction is not satisfied by the surfaces that we study at the nanoscale. The average kinetic friction force Fk depends on V as Fk∝ln⁡V.