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

为碳化硅基陶瓷基复合材料在核裂变中的应用及其向聚变的转化贡献了一个令人兴奋的机会。对于这个项目，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。这个项目的博士生将在布里斯托尔大学工作，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断层扫描特性。核裂变中的组件需要能够在极端温度下运行、抵抗高通量中子辐射损伤并保持结构稳定的材料，例如，事故容忍燃料包层，以及包括STEP(用于能源生产的球形托卡马克)和演示的核聚变。特别是，碳化硅纤维增强碳化硅复合材料(SiCf/SiCm)具有低中子吸收、高导热系数、高断裂韧性、在高温(例如~1000℃)下具有优异的化学/机械稳定性，能够提供最高的热力学效率的核结构部件。在这个项目中，博士生将首先回顾这类材料的公开文献中可用的辐照数据，并设计后续使用高能离子、质子或中子的辐照实验。辐照后的样品将根据其微观机械性能进行检测，具体取决于辐照表面的厚度、常规的纳米压痕或更复杂的微悬臂梁弯曲/立柱压缩试验。在布里斯托尔拥有20年经验的英国，将使用高分辨率的瞬时热反射(TTR)方法来测量碳化硅纤维和基质的热导率退化，这是辐射损伤的函数。此外，还将使用独特的原位高温X射线微层析成像技术来研究未经辐照的SiCf/SiCm的变形和断裂。这将只研究使用温度对材料在类似使用条件下加载时的强度/失效应变、裂纹萌生和扩展等力学行为的影响。

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.