Swelling of SiC at intermediate and high irradiation temperatures

This paper presents results from a neutron irradiation campaign on CVD SiC carried out in the High Flux Isotope Reactor. Materials were irradiated in a range of temperature from 200 to 1500 °C and from a fraction of a dpa to ∼6 dpa. Data on swelling and room temperature thermal conductivity are presented. The swelling behavior below ∼800 °C agrees well with the literature values. Data in the range of 1000-1600 °C indicates that swelling increases as the dose is increased from 2 dpa to 6 dpa, at higher-swelling with increasing irradiation temperature. Any peak in void swelling apparently occurs at irradiation temperature >1500 °C (>0.6T_m). In the 1100-1200 °C temperature range, volumetric swelling is apparently at a minimum though increases from ∼0.2% to ∼0.4% as dose increases from ∼2 dpa to ∼6 dpa. The maximum swelling was found to be ∼1.5% at the maximum dose and temperature of this study, ∼6 dpa and ∼1500 °C. Room temperature thermal conductivity data over the entire temperature range are presented and a direct correlation between the thermal defect resistance and swelling is seen for materials irradiated at temperature less than 800 °C. Above 1000 °C the correlation between swelling and thermal defect resistance breaks down indicating a changing microstructure at high temperature to a microstructure less effective at scattering phonons on a swelling-normalized basis.