Young Investigator Program: Tribology of Nanostructured Silicon Carbide for MEMS and NEMS Applications in Extreme Environments.

摘要

Understanding tribological response of materials (adhesion, friction and wear) from atomistic and molecular perspective is essential for design of reliable devices with dimensions in the nanometer regime. In this project atomistic simulations have been carried out to discover fundamental mechanisms that control adhesion, friction, and wear of covalent ceramics with a particular emphasis on the role of refining material's grain size to the nanometer regime. It was discovered that resistance to wear (scratch hardness) of single crystal materials can be predicted based on the dislocation density that develops in the material, while the dislocation density can be quantitatively described using analytical theories. Transition from ploughing to cutting in nanoscale contacts can be predicted using geometric models developed for macroscale contacts. Decreasing the grain size of SiC to the nanometer regime makes the material more pliable and therefore more amenable to machining of engineering components. It was shown that silicon carbide is not only more resistant to oxidation than silicon, but silicon carbide has also a lower adhesion than silicon in the presence of oxidizing environments. Silicon carbide is therefore a promising material for coatings of Si-based MEMS devices.