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Oxygen Diffusion and Reaction Kinetics in Continuous Fiber Ceramic Matrix Composites

出版	National aeronautics and space administration cleveland oh lewis research center, 1999
URL	http://books.google.com.hk/books?id=CUk7AQAAMAAJ&hl=&source=gbs_api

註釋Previous stressed oxidation tests of C/SiC composites at elevated temperatures (350 deg C to 1500 deg C) and sustained stresses (69 MPa and 172 MPa) have led to the development of a finite difference cracked matrix model. The times to failure in the samples suggest oxidation occurred in two kinetic regimes defined by the rate controlling mechanisms (i.e.; diffusion controlled and reaction controlled kinetics). Microstructural analysis revealed preferential oxidation along as-fabricated, matrix microcracks and also suggested two regimes of oxidation kinetics dependent on the oxidation temperature. Based on experimental results, observation, and theory, a finite difference model was developed. The model simulates the diffusion of oxygen into a matrix crack bridged by carbon fibers. The model facilitates the study of the relative importance of temperature, the reaction rate constant, and the diffusion coefficient on the overall oxidation kinetics.