Recovery behavior of SiCf/SiC composites by post-irradiation annealing up to of 1673 K

Silicon carbide fiber-reinforced silicon carbide composite (SiCf/SiC) has been proposed as a satisfied material to accommodate an extreme and corrosive irradiation ambience such as first wall of fusion reactors. Chemical Vapor Infiltration (CVI) and Electrophoretic Deposition (EPD) are the processes those have been conducted in order to fabricate the composites. In this study, CVI-SiC and EPD-SiC composites were neutron-irradiated in the BR2 reactor up to a fluence of 2.0-2.5×1024 n/m2 (E>0.1 MeV) at 333-363 K. Heat treatments were carried out with step-heating method in a precision dilatometer in order to understand their recovery behavior. The specimens were held each temperature step for 6 h. Length change was recorded during each isothermal annealing step from room temperature up to 1673 K with 50 K increment. Between 1473 K and 1523 K, the EPD composite recovered abruptly and completed. However, the CVI specimen did not recover completely even though it was heated up to 1673 K. The recovery curves were analyzed with a first order model, and rate constants at each annealing step were obtained. Activation energies for both specimens were generally increased with increasing the annealing temperature, except for stage 2 in the CVI and stages 2 and 3 in the EPD specimens. Compared to the activation energies of monolithic SiC, nearly similar values were observed except for the activation energy at stage 4. So, the recovery processes of stage 4 for both specimens and stage 3 in the EPD specimen were different from those of high-purity monolithic SiC.