Characterisation of deuterium transport in the fibres and matrix of a 3D-SiCf/SiC composite

A non-stationary heterogeneous transport model has been used to simulate a series of deuterium absorption–desorption tests carried out with two sets of 3D-SiCf/SiC composite specimens over a temperature range of 675–1029 K and driving pressures ranging from 13 to 101 kPa. The deuterium transport parameters corresponding to each phase of the composite have been derived showing the following Arrhenius tendencies for the diffusivity and solubility in the matrix: Dm (m2 s−1)=9.0×10−8 exp(−39.0 (kJ mol−1)/RT), Sm (mol m−3)=1.9×105 exp(−70.7 (kJ mol−1)/RT), and the fibre: Df (m2 s−1)=1.6×10−11 exp(−91.0 (kJ mol−1)/RT), Sf (mol m−3)=2.1×101 exp(−28.5 (kJ mol−1)/RT), the solubilities being referred to 105 Pa. The different manufacturing procedures followed in the preparation of the specimens have not provoked a noticeable variation of the deuterium transport characteristics of the matrix or the fibres. The results are compared with the parameters previously obtained for different types of silicon carbide and the same material with a homogeneous transport model. The differences found are explained on the basis of the physico–chemical phenomena foreseen within its particular structure.