J. Lara et Wt. Tysoe, INTERACTION OF EFFUSIVE BEAMS OF METHYLENE-CHLORIDE AND CHLOROFORM WITH CLEAN IRON - TRIBOCHEMICAL REACTIONS EXPLORED IN ULTRAHIGH-VACUUM, Langmuir, 14(2), 1998, pp. 307-312
The growth kinetics of films formed from the thermal decomposition of
small, volatile chlorinated hydrocarbons on iron have been previously
measured at relatively high pressures (a few Torr) using a microbalanc
e. These results were used to model the tribological behavior of these
molecules as extreme-pressure lubricant additives. Similar chemistry
is examined on clean iron prepared in ultrahigh vacuum using a de mole
cular beam created using a directional dosing source where the beam is
incident on the clean sample and the gas-phase products of the reacti
on are detected mass spectroscopically. The temperature-and pressure-d
ependence of the decomposition rate of both methylene chloride and chl
oroform are found to agree well with the kinetics measured in the micr
obalance. In addition, the nature of the reactive film, which consists
of FeCl2 and incorporates carbon, is found to be identical in both re
gimes suggesting that film growth kinetics can be successfully measure
d in ultrahigh vacuum. Finally, the only gas-phase reaction product de
tected in either case was hydrogen, indicating that both reactants the
rmally decompose to form FeCl2, deposit carbon, and evolve hydrogen.