Chemical reactivity of SiC fibre-reinforced SiC with beryllium and lithium ceramic breeder materials

SiC fibre-reinforced SiC fabrics (f-SiC/SiC) are considered for structural materials of advanced fusion blanket concepts. Priority tasks are compatibility studies of SiC with Li breeder ceramics and the Be neutron multiplier. Isothermal and anisothermal powder reactions by DTA up to 1220°C were examined between Li4SiO4, Li2ZrO3 and Li2TiO3, respectively, and SiC and SiC/SiO2 mixtures, respectively. The SiC/SiO2 mixture simulated the chemical state of Nicalon fibres. Solid state reactions between SiC and Be pellets were studied by capsule experiments. The reaction products Be2C and Si were observed between the initial phases after annealing at 800°C and 900°C. A parabolic time law with a chemical diffusion coefficient D̃=2.6×10−15 m2/s of Be in the products was deduced at 900°C. Additional oxygen released from SiO2 as a component of the simulated fibres oxidised the reaction products via the gas phase by formation of a Be2SiO4 layer. All reactions are kinetically hindered below 700°C.