UTILIZATION OF RAMAN-SPECTROSCOPY IN TRIBOCHEMISTRY STUDIES

Raman spectroscopy is used to investigate the tribochemistry of thin f ilm solid lubricants. The development of an in situ tribotester (pin-o n-disk), to be used in conjunction with a Raman spectrometer, is descr ibed in detail and its utility is demonstrated in several MoS2-based t hin film systems. The films studied include two commercial films and t wo films generated in-house by pulsed laser deposition (PLD). The comm ercial films were MoS2-PbO-graphite and MoS2-Sb2O3. The PLD films were MoS2 and MoS2-PbO. Wear test studies on the commercial films generall y produced MoO3 as a reaction product. PLD films were deposited at roo m temperature and 300-degrees-C. The PLD films formed at room temperat ure are amorphous and do not exhibit Raman scattering. The 300-degrees -C films contain enough crystalline domains to exhibit Raman scatterin g. Initial rubbing of the room-temperature PLD films imparts enough cr ystallinity to support Raman scattering. Wear tests on the PLD films p roduce reaction products containing MoO3 and PbMoO4. These crystalline oxides have a large Raman scattering cross section, making them easil y detectable. These data provide a unique insight into the tribochemic al interactions Of MoS2-based materials.