The Annealing of Neutron Irradiation-Induced Defects in Silicon Carbide

Radiation-induced changes in the macroscopic dimensions, lattice parameters, strength and thermal diffusivity of various types of silicon carbide suggest that different polytypes of this material may behave differently when subjected to a nuclear radiation field. This paper reports the existence of visible defects in post-irradiation annealed material. RFL (Springfields) self-bonded silicon carbide was irradiated in the WR-1 organic-cooled reactor. The specimens were exposed to a fast neutron fluence of 2.2×1020nvt (E>0.18 MeV) at a temperature of 700°C. Specimens suitable for examination in the electron microscope (3m.m × 1 m.m thick discs) were subsequently annealed for 4 hrs. at temperatures up to 2000°C. The material was ground down from both sides to approximately 0.25 m.m thick and ion thinned for examination in a Hitachi HU-200E electron microscope equipped with a 40° high resolution tilting stage.