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

这是一个令人兴奋的机会，有助于SiC基陶瓷基复合材料在核裂变及其转化为聚变中的应用。对于该项目，MSE-F集团（UKAEA）将从国际工业合作伙伴那里提供四种不同等级的SiCf/SiCm。该项目的博士生将在布里斯托大学工作，预计将在英国原子能机构花费大量时间进行相关实验，如微机械测试和聚焦离子束层析成像表征。核裂变组件需要能够在极端温度下工作，抵抗高通量中子辐照损伤，同时保持结构稳定的材料，例如，作为事故容忍燃料包壳，以及核聚变，包括STEP（球形托卡马克能源生产）和DEMO。特别地，已经认识到，碳化硅（SiC）纤维增强SiC基质复合材料（SiCf/SiCm）具有低中子吸收、高热导率、高断裂韧性、在高温下优异的化学/机械稳定性（例如，在本项目中，博士生将首先对这类材料的公开文献中可用的辐照数据进行回顾，并设计随后使用高能离子、质子或中子的辐照实验。根据表面辐照层的厚度，将对辐照样品的微观机械性能进行检查，将进行常规纳米压痕或更复杂的微悬臂梁弯曲/柱压缩测试。SiC纤维和基体的热导率退化是辐照损伤的函数，将使用高分辨率TTR（瞬态热反射）方法进行测量，该方法在英国是独一无二的，布里斯托有大约20年的经验。此外，独特的原位高温X射线显微层析成像技术将用于研究未辐照的SiCf/SiCm的变形和断裂。这将仅研究在类似于使用条件下加载时，使用温度对材料力学行为（强度/失效应变、裂纹萌生和扩展）的影响。

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.