Dynamic oxidation and protection of the PAN pre-oxidized fiber C/C composites

摘要

Pre-oxidized fibers as reinforcement are candidates for reducing the overall cost of C/C composites with superior properties. This study investigated the dynamic oxidation and protection of the pre-oxidized fiber C/C composites (Pr-Ox-C-C). According to the Arrhenius equation, the oxidation kinetics of the Pr-Ox-C-C consisted of two different oxidation mechanism with the transition point was at about 700 degrees C. Scanning electron microscopy investigation showed that oxidation initiated from the fiber/matrix interface of composites, whereas the matrix carbon was easily oxidized. To improve the anti-oxidant properties of Pr-Ox-C-C, a ceramic powder-modified organic silicone resin/ZrB2-SiC coating was prepared by the slurry method. The coated samples were subjected to isothermal oxidation for 320 h at 700 degrees C, 800 degrees C, 900 degrees C, 1000 degrees C and 1100 degrees C with incurred weight losses of 1.6%, 0.77%, 1.28%, 0.68% and 1.19%, respectively. After 110 cycles of thermal shock between 1100 degrees C and room temperature, a weight loss of 1.30% was obtained. The Arrhenius curve presented four different phases and mechanisms for coating oxidation kinetics. The excellent oxidation resistance properties of the prepared coating could be attributed to the inner layer which was able to form B2O3-Cr2O3-SiO2 glass to cure cracks, and the ZrB2-SIC outer layer that could provide protective oxides to reduce oxygen infiltration and to seal bubbles.