J. Phys. IV France 7 (1997) C2-1259-C2-1260
XAFS Study on Decomposition of Molybdenum Dialkyl Phosphorodithioate in Commercial Engine OilsT. Okamoto, K. Fujita and M. Kawamura
Toyota Central Research and Development Laboratories Inc., Aza Yokomichi, Oaza Nagakute, Nagakute-cho, Aichi-gun, Aichi 480-11, Japan
The local structure around Mo atoms in fuel-saving engine oils has been investigated by XAFS using laboratory scale equipment. The EXAFS results suggest that the local structure of the Mo atoms in fresh engine oils is similar to that in the molybdenum dialkyl phosphorodithioate. It is also suggested that the molybdenum compound in the oils changes to a Mo oxide in which a Mo atom is coordinated by six oxygen atoms after 2000km running. XANES spectra of the compounds show that the coordination geometry around the Mo atoms in the Mo oxide is similar to that in MoO3 rather than MoO2. The deterioration of anti-friction effect of the engine oils after use coincides with Mo oxide formation.
© EDP Sciences 1997