Oxidation experiments on the carbon preform of a phenolic-impregnated carbon ablator were performed in the NASA Ames ow-tube reactor facility, at temperatures between 700 and 1300 K, under dry air gas at pressures between 103 and 104 Pa. Mass loss, volumetric recession and density changes were measured at different test conditions. An analysis of the diffusion/reaction competition within the porous material, based on the Thiele number, allowed us to identify low temperature and low pressure conditions to be dominated by in-depth volume oxidation. Experiments above 1000 K were found at transition conditions, where diffusion and reaction occur at similar scales. The microscopic oxidation behavior of the fibers was characterized by scanning electron microscopy and energy dispersive x- ray analysis. The material was found to oxidize at specific sites forming a pitting pattern distributed over the fibers' surface. Calcium- and oxygen-rich residues from the oxidation reactions were observed at several locations.

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Published in the Proceedings of the 44th AIAA Thermophysics Conference, Paper 2013-2769, p. 1-14.

Copyright © 2013 by University of Kentucky.

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