Tribo-chemistry of Boundary Film Studied by Stable Isotopic Tracers

Stable isotopic tracer in combination with TOF-SIMS (time-of-flight secondary ion mass spectroscopy) is proposed as a versatile tool for investigation of tribo-chemistry. This unique technique is based on tracing 2H (deuterium, D)- labeled and/or 13C-labeled hydrocarbon moiety that exist on rubbed surface. Two examples are given in this article: 1) A monomolecular film of perdeuterio-octadecanoic acid was deposited on Si(100) flat specimen. The tribological properties of the monomolecular film were evaluated by a ball-on-flat type tribo-test. Lifetime for low friction is influenced by the ball material. The transfer of the carboxylic acid from the flat specimen onto the ball surface was found to be beneficial for prolong the lifetime. 2) GMO (glycerol mono-oleate) in synthetic hydrocarbon provides extremely low friction at steel-DLC (diamond like carbon) contact. 13C-labeled GMOs were employed to investigate the state of the additive on the DLC surface. Direct interaction of the additive on the DLC surface was suggested by TOF-SIMS analysis.