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

摘要

TCP (tricresylphosphate) is a high-temperature vapor-phase lubricant, known for its demonstrated anti-wear properties for macroscopic systems and potential for MEMS applications. We have performed adsorption measurements of TCP on high purity iron and chromium surfaces with a quartz crystal microbalance , in conjunction with Auger electron spectroscopy and scanning tunneling microscopy, yielding values for gas uptake rates, molecular slippage, and tribofilm stress levels in the temperature range 25 - 400 C. At room temperature, TCP uptake is observed to be limited to two layers of intact molecules that are likely to be physisorbed. Above 200 C, the data recorded on both iron and chromium substrates are consistent with far greater uptake levels and extensive interdiffusion of TCP fragments with the substrate. The most noteworthy difference between the two substrates is TCP's fragmentation upon impact on iron, but not chromium, at elevated temperatures. The effect of oxygen on film formation has also been studied Above 3000 C, sizeable frequency and amplitude shifts are observed for oxygen and TCP on iron, interpreted as the formation of a viscoelastic polymer-solid matrix' on the iron surface. The absence of such shifts for chromium indicates its lack of reactivity. These findings corroborate TCP's known ability to lubricate iron, but not chrome. We have thus successfully mapped atomic scale dynamical properties to the lubricant's macroscopic performance.