Friction in Full View

The primary focus of the proposed work is a combination of in-situ transmission electron microscopy studies of sliding surfaces and materials-science based modeling of the nanoscale processes taking place in the triboactive region using primarily dislocation-based analytic models. The main focus of the experimental work will be to directly resolve in real time the processes taking place, ranging from the motion of dislocations and sliding of interfaces to tribologically induced chemical or structural transitions. This will exploit all the different modes of electron microscope imaging ranging from conventional low-resolution imaging through electron-energy loss spectroscopy to atomic scale imaging. The thrust of the analytical component will be to marry conventional materials science ideas such as the effect of barriers on dislocation motion with what is taking place in the triboactive layer, to develop parameter-free analytic models which have predictive power so can be used in the future to estimate what will be taking place in new tribological problems or systems. The combination of experiment and theory is important, since they are mutually synergistic and each part in isolation could go down incorrect paths. In terms of Intellectual Merit, the work seeks to establish a solid materials science foundation for tribological processes taking place at the nanoscale in the triboactive region, a topic which is relatively unexplored. Both the experimental and theoretical work are new directions in tribology which have been pioneered by the PI, and compliment and extend what is already known from more mechanical, physical or chemical approaches but taking this in a new direction by introducing the core concepts of materials science into the problem. In terms of the Broader Impact, the experimental technique which will be used (in many respects pioneered) can be used by other scientists to probe their own systems, something which is already taking place with others following our lead. The theoretical models can also have a wider impact particularly since the focus is on predictive analytical models which can be used to estimate issues in real engineering situations quickly. In the broader view, energy losses due to frication are going to become a substantial issue in energy needs for the 21st century, and this work can help reduce these. In terms of education, the research will help support both local outreach to high-school students as part of the existing programs with Chute and Nichols Middle Schools and the HANDS program, as well as more international outreach efforts involving efforts to run schools and workshops on electron crystallography in places such as Mongolia, Qatar and South Africa via the International Union of Crystallography.