Vapor-Phase Lubricants: Nanometer-Scale Mechanisms and Applications to Sub-Micron and Rotating Machinery

摘要

Vapor-phase lubricants: Nanometer-scale mechanisms and applications to sub-micron machinery was a new program supported by AFOSR involving a set of experimental seeking to explore the nanometer-scale origins of the lubricating properties of vapor-phase lubricants in controlled environmental conditions and well-defined contact geometries. Although such lubricants have been the subject of much research for over 40 years, the atomic-scale details of their lubrication mechanisms are far from being satisfactorily understood. We have evaporated high purity Fe and Cr substrates in UHV conditions onto Quartz Crystal Microbalances, and then measured the uptake rates of TCP in the temperature range 25-40 deg C. The Sample's surface chemistries were also investigated by means of Auger Spectroscopy, and, as expected, graphitic carbon was found to be the dominant surface constituent. More surprisingly, we observed the uptake rates to depend on sample history, providing positive confirmation that interdiffusion of TCP with Fe is extensive, and key to its beneficial tribological properties. A second set of experiments has been motivated by the fact that vapor lubrication mechanisms may prove to be of critical importance to sub-micron mechanical systems on account of the difficulty of applying a lubricant to such systems by other techniques. These studies involve characterization of the nanotribological behaviors of simple organics and TBPP on metal surfaces in a simple nanomechanical system consisting of a STM tip sliding along the surface electrode of a QCM electrode. They have revealed that surface regions exposed to lubricants which directly experience rubbing exhibit lower friction and virtually no wear. The phenomenon is attributable to either tribochemically formed graphitic regions or heating induced migration of carbon to the interface.