Flow-Tube Oxidation Experiments on the Carbon Preform of a Phenolic-Impregnated Carbon Ablator

摘要

Oxidation experiments on the carbon preform of a phenolic-impregnated carbon ablator were performed in a flow-tube reactor facility, at temperatures between 700 and 1300 K, under dry air gas at pressures between 1.6 × 10~3 and 6.0 × 10~4 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, allows identification of 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 surface of the fibers. Calcium- and oxygen-rich residues from the oxidation reactions were observed at several locations.