Oxidation behaviour of SiC fibre reinforced SiC
The oxidation behaviour of one-dimensional and two-dimensional SiC fibre reinforced SiC was investigated up to 1520°C in air, as well as in water vapour saturated air and argon by calorimetry, DTA and TGA. The oxidation process takes place in three steps: (1) oxidation of free carbon in the carbon c...
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Published in | Journal of nuclear materials Vol. 227; no. 1; pp. 130 - 137 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
Elsevier B.V
01.12.1995
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Online Access | Get full text |
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Summary: | The oxidation behaviour of one-dimensional and two-dimensional SiC fibre reinforced SiC was investigated up to 1520°C in air, as well as in water vapour saturated air and argon by calorimetry, DTA and TGA. The oxidation process takes place in three steps: (1) oxidation of free carbon in the carbon coated composites between 530 and 690°C with mass losses up to 7.5%; (2) a fast exothermal process associated with mass gain starting at 800°C and terminated below 1500°C within 1 h; (3) the diffusion controlled oxidation of bulk SiC. The processes follow a logarithmic rate law between 875 and 985°C with an effective activation energy Q = 84 kJ/mol. The amorphous reaction product Si0
2 transforms to cristobalite at (930 ± 50)°C. The oxidation kinetics follows a quadratic rate law above 1000°C with rate constants
k = 3.5 × 10
−7g
2/cm
4h for 1D SiC/SiC and
k = 5 × 10
−8g
2/cm
4h for 2D SiC/SiC at 1520°C in air. The rate constants are up to three orders of magnitude higher than that for high density monolithic SiC which is explained by the high porosity of the SiC matrix. |
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Bibliography: | ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 |
ISSN: | 0022-3115 1873-4820 |
DOI: | 10.1016/0022-3115(95)00133-6 |