Carbon/carbon (C/C) composites have been extensively studied due to their low density, excellent high-temperature mechanical properties, low coefficient of thermal expansion (CTE) and good thermal shock resistance. These properties make them particularly attractive for aerospace applications as structural and thermal protection materials. However, the poor oxidation and ablation resistance of C/C composites inhibits their extensive applications in aerospace field. It is of momentous significance to improve the oxidation and ablation resistance of C/C composites to prolong their life span and improve their working reliability and security.
With the background of thermal protection applications of anti-oxidation C/C composites, the ultra-high temperature oxidation and ablation mechanisms of C/C composites modified by ZrC were studied based on thermodynamics and kinetics; the factors relating with oxidation and ablation properties were discussed. On the basis of experimental work, the oxidation and ablation models were established. The main conclusions presented in this thesis can be summarized as follows:
1． The vapour pressure of related oxides such as CO and B2O3 might be very high at the interfaces, even higher than 100000 Pa, which was detrimental to the formation of entire oxide scales on carbides (or borides) during ultra-high temperature oxidation. Only single inhibitor could not effectively hinder oxygen diffusion.
2. ZrC additive improved the ablation properties of C/C composites. The ablation resistance of C/C composites became better with the increase of ZrC content. The linear ablation percentage of modified C/C-ZrC composites followed a linear law with various slope during different period. In addition, the ablation of modified C/C-ZrC composites became worse as the temperature increased.
3. The linear ablation rates of modified C/C-ZrC composites during the static oxidation tests were much lower than those during the ablation tests due to the absence of erosion in the former. In addition, the linear ablation rates increase obviously with temperature and oxygen partial pressure.
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