The contact between macroscopic surfaces occurs on asperities, which are irregularly shaped protuberances existing on all engineering surfaces. Like fractals, these surface features occur across all length scales. As our understanding of these contacts increases, it is readily apparent that the nanoscale interactions dominate the macroscopic tribological behaviors. It is critically important to evaluate the nanotribology of tribological surfaces to gain further fundamental understanding of the chemical, physical, and morphological processes that govern the tribological behavior of sliding electrical contacts. This work involves a small team of scientists with extensive background and experience in characterization, testing, and simulation of nanoscopic tribological systems, in situ spectroscopy, and computational plasma dynamics. 

The mechanisms responsible for the remarkable tribological properties and performance of these copper brush systems operating in a wet CO2 environment are unknown. A puzzling phenomenon of increased wear on the anode surfaces (as compared to the cathode) is nearly universally observed in macroscopic systems; to date, there is no fundamental understanding of process. The bounds on the operational envelope are also uncertain: upper temperature limits of 80ºC have been observed, there are theories and data that demonstrate an upper limit on nominal contact pressure, and there are maximum nominal current densities above which excessive wear occurs. There are two hypotheses that persist: 1) electric field enhanced preferential oxidation, and 2) micro-arc damage and preferential material remove from the anode surfaces.

This unique team will pursue microscopic modeling and characterization of asperity level sliding electrical contact events under environments relevant to the DoD mission (i.e. the sliding of high current density copper brushed in a wet CO2 environment). In addition, we are pursuing three of the grand challenges identified by the tribology community: 1) predicting the mechanical and tribological behavior of materials from first principles, 2) bridging the gap between nanotribology and macrotribology, and 3) the development of tribological systems capable of operation under extreme environments.