The Binding of Lubricating Films to Ceramic and Refractory Materials

Abstract

AbstractIn order to better understand the chemical bonding forces which control lubricating film stability and adhesion, the binding of lead and tin atoms on the ceramics alumina and silica was investigated by laser induced thermal evaporation combined with mass spectrometric detection of the evaporated species. The interaction between lead or tin and alumina and silica was studied as a function of coverage. The sticking probability for the interaction was measured and found to be temperature and coverage dependent. At low coverage the binding energy of lead to alumina and silica was determined as 237and 246 KJ mol1 respectively, while the binding energy of tin to alumina and silica is 313 and 331 kJ mol1, respectively. A binding energy model based on thermochemical and crystallographic data was used to predict corresponding values which agree with the experimental values.In addition, temperature programmed desorption and\or decomposition (TPD) was used to investigate the thermal and\or chemical stability of MoS2 films on molybdenum supports. The TPD spectra for S2 from MoS 2 were analyzed, and activation energies were found to be dependent on the film application technique. The binding energy model also provided a useful approximation to the experimental activation energies for the S2 production from MoS2 films. Water and carbon impurities were shown to contribute to the decomposition of MoS2 producing SO2 and CS2. The TPD spectra of S2, SO2, and CS2 provide a measure of the onset of lubricant decomposition.