Abstract
Abstract
Ionic liquid is expected to function as a novel lubricant under vacuum conditions because of its unique properties, such as low volatility, thermal stability, and electrical polarity. The tribological behaviour of an ionic liquid that would be used for four kinds of metals, Al, Cu, Fe, and Ti, was evaluated using a high-vacuum pin-on-disc sliding tester equipped with a Q-mass spectrometer. The ionic liquid exhibited the expected lubricity for Fe and Cu. Increases of several partial gas pressures, which are thought to be caused by the tribo-chemical decomposition of the ionic liquid, were observed in all cases. Deterioration of the vacuum level was seen for Ti and Al. Surface analytical results using X-ray photoelectron spectrometer showed the formation of metal fluoride on the sliding metal surfaces except for Cu. The tribo-chemical reaction and decomposition behaviour of the ionic liquid strongly depended on the kind of sliding metal. The combination of sliding material and ionic liquid appears to be an important factor in the design of high-vacuum sliding systems.
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