Illustrations of the reaction- and diffusion-controlled regimes studied with the oxidation model. A cross-section of a composite with a 6-by-6 array of reinforcing fibers is shown from left to center for time equal to t0, t1, and t2 for the reaction-controlled regime (top) and the diffusion-controlled regime (bottom). Photomicrographs showing oxidation patterns for the kinetic regimes are shown to the right. Reaction-controlled kinetics occur at low temperatures. The kinetics depend on the rate at which carbon and oxygen reactions occur. The entire material can become saturated in oxygen so that a somewhat uniform consumption of carbon is obtained. Diffusion-controlled kinetics occur at high temperatures. The kinetics depend on the rate at which oxygen is supplied. A large gradient in oxygen concentration is obtained so that the interior is starved of oxygen and oxidation occurs from the outer perimeter inward.
Last updated: June 25, 2003
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