Degradation of the thermal and mechanical properties SiCf/SiCm composite with irradiation

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An exciting opportunity to contribute to the application of SiC-based ceramic matrix composites in nuclear fission and its translation to fusion. For this project the MSE-F group (UKAEA) will supply four different grades of SiCf/SiCm available from international industrial partners. The PhD student on this project will be based at the University of Bristol and is anticipated to spend a significant amount of time at UKAEA to conduct relevant experiments, such as micromechanical testing and Focus Ion Beam tomography characterisation.Materials able to operate at extreme temperatures, resisting high-flux neutron irradiation damage while remaining structurally stable are needed for components in nuclear fission, e.g., as accident tolerant fuel cladding, as well as nuclear fusion including STEP (Spherical Tokamak for Energy Production) and DEMO. In particular, it has been recognised that silicon-carbide (SiC) fibre reinforced SiC matrix composites (SiCf/SiCm), which has low neutron absorption, high thermal conductivity, high fracture toughness, excellent chemical/mechanical stability at elevated temperatures (e.g., ~1000C), are able to provide the highest thermodynamic efficiency nuclear structural components.During this project, the PhD student will first conduct a review regarding the available irradiation data in open literature for this class of materials, and design subsequent irradiation experiments using energetic ions, protons or neutrons. The irradiated samples will be examined in terms of their micro-mechanical properties, depends on the thickness of the surface irradiated layer, conventional nano-indentation or more sophisticated micro-cantilever bending/pillar compression tests will be conducted. The thermal conductivity degradation of the SiC fibre and matrix, which is a function of the irradiation damage, will be measured using high-resolution TTR (transient thermoreflectance) method which is unique in the UK where Bristol has about 20 years' experience.In addition, a unique in situ high temperature X-ray micro-tomography technique will be used to investigate the deformation and fracture of unirradiated SiCf/SiCm. This will study only the effect of service temperature on the material's mechanical behaviour in terms of strength/failure strain, crack initiation and propagation when loaded under conditions similar to service.