Water and hydrocarbon desorption from rapidly-heated metal oxide surfaces

Understanding and controlling water and hydrocarbon desorption from steel surfaces under vacuum are crucial for high-voltage pulsed power applications. Ohmic heating in Sandia’s Z-machine conductors can drive temperature rises of 1000 K over nanoseconds, leading to plasma formation and current loss. We apply reactive and non-reactive classical molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) methods to study the thermodynamics and kinetics of fast desorption from hematite Fe2O3 surfaces. MD simulations are conducted using thermodynamically consistent coverages deduced from GCMC. For water, the resulting time- and temperature-dependent desorption profiles on the Fe2O3 (0001) and (1-102) surfaces show cooperative behavior. Results are in reasonable agreement with simple Temkin isotherm model estimates. Similar reduced models will be discussed for hydrocarbons desorption. The effect of external electric field on desorption profiles will also be discussed.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525.