Progress in analytical spectroscopic methods and in the instrumentation for tribological measurements have contributed in the last decades to the understanding of the mechanism of growth and stability of tribological films. Tribological films (also called tribofilms) are layers that are formed on two counterparts that move in relative motion to each other. These films play an important role in reducing friction and/or wear and their presence may contribute to saving energy and reducing the amount of CO2 produced in an engine. Tribofilms are usually formed in presence of compounds that are added to lubricant oils. The most commonly used additives contain metals such as zinc and non-metallic elements such as as sulfur and phosphorus. The need for reducing the amount of these elements in the environment—in agreement with European regulations—has stimulated research in tribology by means of surface analytical methods that offer the unique opportunity to characterize surfaces that are in mechanical contact. In this talk the results obtained in the characterization of tribofilms by means of X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and in situ attenuated total reflection infrared spectroscopy (ATR FTIR) will be reviewed. X-ray photoelectron spectroscopy has become a very important source of information on surfaces, thin layers and interfaces in the investigation of non-ideal samples such as tribofilms. Nowadays it is possible to use very well focused beams for exciting the sample down to less than 10 μm, so that detailed chemical-state information,composition and thickness of the tribological films and composition of the interface within the reaction layer and the substrate can be obtained uniquely from the contact areas of the two counterparts. Furthermore, imaging capabilities, as well as angleresolved XPS allow the 3D-representation of chemical species. Complementary to XPS is ToF-SIMS. Recent bismuth-cluster sources have become the standard analytical tools for obtaining high-resolution mass spectra, also in the high mass range, and for obtaining images with a lateral resolution down to 80-100 nanometers. It provides not only elemental but also molecular information. The results obtained with a recently developed in situ ATR FT-IR tribometer that allows the identification of the functional groups during the sliding of the two counterfaces will be also presented and the strengths of ex situ analytical methods will be discussed.
Surface chemical characterization of tribological films formed under boundary lubrication conditions
ROSSI, ANTONELLA
2014-01-01
Abstract
Progress in analytical spectroscopic methods and in the instrumentation for tribological measurements have contributed in the last decades to the understanding of the mechanism of growth and stability of tribological films. Tribological films (also called tribofilms) are layers that are formed on two counterparts that move in relative motion to each other. These films play an important role in reducing friction and/or wear and their presence may contribute to saving energy and reducing the amount of CO2 produced in an engine. Tribofilms are usually formed in presence of compounds that are added to lubricant oils. The most commonly used additives contain metals such as zinc and non-metallic elements such as as sulfur and phosphorus. The need for reducing the amount of these elements in the environment—in agreement with European regulations—has stimulated research in tribology by means of surface analytical methods that offer the unique opportunity to characterize surfaces that are in mechanical contact. In this talk the results obtained in the characterization of tribofilms by means of X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and in situ attenuated total reflection infrared spectroscopy (ATR FTIR) will be reviewed. X-ray photoelectron spectroscopy has become a very important source of information on surfaces, thin layers and interfaces in the investigation of non-ideal samples such as tribofilms. Nowadays it is possible to use very well focused beams for exciting the sample down to less than 10 μm, so that detailed chemical-state information,composition and thickness of the tribological films and composition of the interface within the reaction layer and the substrate can be obtained uniquely from the contact areas of the two counterparts. Furthermore, imaging capabilities, as well as angleresolved XPS allow the 3D-representation of chemical species. Complementary to XPS is ToF-SIMS. Recent bismuth-cluster sources have become the standard analytical tools for obtaining high-resolution mass spectra, also in the high mass range, and for obtaining images with a lateral resolution down to 80-100 nanometers. It provides not only elemental but also molecular information. The results obtained with a recently developed in situ ATR FT-IR tribometer that allows the identification of the functional groups during the sliding of the two counterfaces will be also presented and the strengths of ex situ analytical methods will be discussed.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.