Deuterium transport in SiCf/SiC composites

A time-dependent gas-phase isovolumetric desorption technique has been used over a temperature range of 675–1029 K and driving pressures ranging from 13 to 101 kPa, to obtain the deuterium transport parameters diffusivity, D, and solubility, S, in a 3-D SiCf/SiC composite. The values obtained are: D(m2s−1)=1.1×10−4 exp[−107.7 (kJ/mol)/RT], S(mol m−3)=1.9×103 exp[−30.2(kJ/mol)/RT]. The set of measurements performed at the same temperature, 871 K, and different loading pressures 13, 33, 60, 101 kPa, has evidenced a power relationship of solubility versus loading pressure with exponent 0.22, departing from Sieverts’ law. These results are compared with the parameters previously obtained for different types of monolithic SiC, and explained on the basis of the physico-chemical phenomena foreseen within its particular structure. The same experiment has been performed with two sets of specimens manufactured using different variants of the hybrid CVI/PIP technique; a negligible variation of transport parameters has been accounted between both groups of specimens.