New Directions for Ultralow Wear Materials: Order, Organization and Orientation - Nature's Design Strategies for Ultralow Wear Materials
Speaker: Brandon Krick, University of Florida
Department: Mechanical & Aerospace Engineering
Location: Engineering Quadrangle J223
Date/Time: Thursday, February 28, 2013, 12:30 p.m. - 1:30 p.m.
Nature has optimized ultralow wear materials through strategic order, organization and orientation from the atomic scale up. Engineering materials and natural materials have an extremely wide range of intrinsic wear resistance, with wear rates spanning more than seven orders of magnitude! Evidence of extremely wear resistant minerals can be found in natural collections of crystalline materials. In biology, dental materials and the preservation of these materials are essential for life. Enamel, which is a largely mineral based hierarchical composite, generates its intrinsic wear resistance through the order and organization of wear resistant minerals. Inspired by natures design of hierarchical composites, such as dental structures from the dinosaurs from the Cretaceous period, we developed ultralow wear polytetrafluoroethylene (PTFE) based nanocomposites; Natures design strategy of generating a protective tribological surface layer has successfully reduced wear in these PTFE systems by more than 4 orders of magnitude with the inclusion of a few percent or less alumina nanofillers.
Fundamental studies of composites are extremely challenging as the complex material microstructure and composition rapidly evolve during sliding. Single crystalline ionic solids offer a unique scientific opportunity to understand and characterize the structure-function relationship for the fundamental mechanisms of energy dissipation in sliding interfaces that result in wear and friction. Recent studies results show that the wear rates of ionic solids span several orders of magnitude and the scaling of these variations can be explained through simple consideration of charge and crystallography. Preliminary results on the wear rates of ionic solids and a link to their crystalline structure, orientation, and ionic charge will be presented. The primary goal of this proposed research is to link material structure and crystallographic orientation to the atomic origins of energy dissipation in a sliding contact and how that dissipation results in friction and gradual removal of surface atoms, i.e., wear. Ionic solids including oxides, nitrides, and carbides, as well as other mineral and ceramic materials form the basis for the synthesis of novel solid lubricating structures for harsh environments because of their high melting temperatures, hardness and wear resistance.