Model for Oxygen Atom Recombination on a Silicon Dioxide Surface

摘要

A steady state model for oxygen atom recombination for temperatures from 300 K to 2000 K on a silicon dioxide surface was developed based on the Langmuir-Rideal heterogeneous recombination mechanism. The bonding of atomic oxygen to the surface and the thermal desorption of atomic oxygen from the surface were also included in the model. The hypothesis was made that the gas-phase oxygen atoms combine directly with the oxygen atoms that constitute the silicon dioxide surface, with other gas-phase oxygen atoms replacing the lost atoms that were bonded on the silicon dioxide surface matrix. The model agrees with the experimental data that is available in the literature, and provides an insight into the processes that control the recombination as a function of temperature. A set of two-dimensional, steady-state, laminar boundary-layer calculations was made using explicit numerical methods to demonstrate the use of this model and to explore the rational limits which may be placed on the role of catalysis for oxygen recombination on a silicon dioxide surface like that of the Space Shuttle. The predicted catalycity of the silcion dioxide surface did reduce the overall heating below that which would be predicted by a fully catalytic surface.