NASA Logo

NTRS - NASA Technical Reports Server

Back to Results
Oxidation and Volatilization of Silica-Formers in Water VaporAt high temperatures SiC and Si3N4 react with water vapor to form a silica scale. Silica scales also react with water vapor to form a volatile Si(OH)4 species. These simultaneous reactions, one forming silica and the other removing silica, are described by paralinear kinetics. A steady state, in which these reactions occur at the same rate, is eventually achieved, After steady state is achieved, the oxide found on the surface is a constant thickness and recession of the underlying material occurs at a linear rate. The steady state oxide thickness, the time to achieve steady state, and the steady state recession rate can all be described in terms of the rate constants for the oxidation and volatilization reactions. In addition, the oxide thickness, the time to achieve steady state, and the recession rate can also be determined from parameters that describe a water vapor-containing environment. Accordingly, maps have been developed to show these steady state conditions as a function of reaction rate constants, pressure, and gas velocity. These maps can be used to predict the behavior of silica formers in water-vapor containing environments such as combustion environments. Finally, these maps are used to explore the limits of the paralinear oxidation model for SiC and Si3N4
Document ID
20020070889
Acquisition Source
Glenn Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Opila, E. J.
(NASA Glenn Research Center Cleveland, OH United States)
Gray, Hugh R.
Date Acquired
September 7, 2013
Publication Date
January 1, 2002
Subject Category
Chemistry And Materials (General)
Funding Number(s)
PROJECT: RTOP 714-04-70
Distribution Limits
Public
Copyright
Public Use Permitted.
No Preview Available