The response of silicon carbide composites to He ion implantation and ramifications for use as a fusion reactor structural material

Silicon carbide fibre–reinforced silicon carbide matrix (SiCf/SiC) composites are desirable in structural nuclear applications due to their low density, high temperature strength and tolerance to energetic radiation. We have subjected two industrial grades of SiCf/SiC to high energy He²⁺ ion irradiation, up to 10,000 appm implanted He at 700 °C, to determine their suitability for blanket structural applications in nuclear fusion. Minor crystallographic evolution is observed following irradiation, with evidence of phase localised stress, intragranular strain, and lattice swelling. This is attributed to vacancy production and subsequent He bubble formation, both intragranular and at grain boundaries. During post-irradiation annealing up to 1300 °C, varying degrees of He bubble evolution are observed, with the Si phase showing the highest level of instability. The fibres appear stable, with no detectable radiation-induced defects. Meanwhile, bubbles in the fibre coating and matrix grains grow and agglomerate. Despite this, no delamination or microcracking is observed.