M. Kaltchev, P. Kotvis, T. Blunt
2001
Citations
0
Influential Citations
25
Citations
Journal
Tribology Letters
Abstract
Molecular beam studies carried out in ultrahigh vacuum show that dimethyl disulfide reacts with initially clean iron to evolve methane. The reaction is proposed to proceed via a methyl thiolate intermediate. Reaction ceases at ∼600 K, an effect that is proposed to be due to the surface being blocked by an overlayer of sulfur and carbon. Reaction recommences above ∼950 K as sulfur diffuses into the iron. The activation energy for the film-forming reaction is 52.5±2.1 kcal/mol, in good agreement with the activation energy for the growth of FeS films from dimethyl disulfide at higher pressures measured using a microbalance. A depth profile of the film grown in ultrahigh vacuum shows that the sulfur-containing film grows on a Fe+C underlayer. Similar molecular beam experiments with diethyl disulfide suggest the formation of an intermediate ethyl thiolate species which decomposes via a β-hydride elimination reaction to evolve ethylene. The activation energy for film growth, in this case, is 60±2.4 kcal/mol. The results of tribological experiments using a pin and v-block apparatus are consistent with FeS forming the anti-seizure film.