| Achoimre: | <p>Reaction-bonded silicon carbide has properties which make it useful for certain components of a nuclear fusion reactor, but its response to irradiation has not been studied since early work suggested its unsuitability. Modern commercially available samples of RB-SiC, along with some novel samples prepared in-house were investigated to identify links between microstructure and radiation and mechanical performance.</p>
<p>2.5 displacements per atom (dpa)and 0.25 dpa of radiation damage were introduced using ion implantation at 300 °C and 750 °C. The radiation-induced changes to mechanical properties were investigated using nanoindentation, chemical defects by Raman spectroscopy, and structural defects by electron backscatter diffraction.</p>
<p>Residual stresses were found to strongly influence the micromechanical properties of reaction-bonded SiC. Radiation changes these stresses leading to the degradation of macroscopic mechanical properties. Further investigation of these residual stresses found they are caused by radiation swelling of silicon carbide. This swelling is constrained by the unirradiated layer in ion irradiation experiments, creating a lateral stress which increases the apparent toughness and hardness, as assessed by nanoindentation. This constrained swelling effect appears to significantly influence the mechanical properties measured by nanoindentation of ion implanted layers. </p>
<p>Ion irradiation appears unable to recreate defects created by neutron irradiation. The lateral swelling stress prevents chemical bonds reaching their equilibrium length, possibly hindering their evolution. The choice of implanted ion also appears to influence defects in SiC; self-ions change the local chemistry and defect structures. </p>
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