Next generation composite materials for extreme environments in nuclear fusion power reactors

核聚变，如果利用，可以提供几乎无限的无碳能源。它还可以解决扩散和长期放射性废物的问题，这些问题阻止了核裂变的进一步扩散。为了使核聚变避免产生长寿命的放射性同位素，只有低活化性能的材料才能用于将接受中子辐照的组件中.这极大地限制了材料的选择，为材料科学家提供了一些独特的挑战。其中一个挑战是找到一种适合于屏蔽超导磁性部件的材料，使其免受反应堆中产生的中子的影响。关键是这些部件不被中子辐照，因为中子引起的加热或辐照损伤会严重影响反应堆的效率和寿命。因此需要一种屏蔽材料，其具有优异的中子阻止性能，同时不会变得高度活跃。它还必须具有机械稳定性，能够承受高温和大量的氦气生产。一种材料thathas最近显示出希望为这一应用是碳化钨，虽然其postirradiationmechanical性能的研究很少。虽然硬质合金的广泛应用导致了对这些材料的广泛研究，但对无粘结剂硬质合金的性能仍知之甚少。无金属基体的碳化钨由于其较低的断裂韧性导致其较差的耐磨性而常常被忽视。这使得它在许多工程应用中成为不受欢迎的材料。然而，它确实具有优越的上级化学稳定性和热稳定性以及硬度和耐腐蚀性。由于后者的性能无疑是更有用的中子屏蔽应用比耐磨性，对无粘结剂化合物的研究是必要的，因此，本论文工作的总体目标是检查的变化inproperties所造成的辐射。然而，在实现这一点之前，必须正确理解其在未辐照状态下的机械行为。本项目将致力于探索这一目标，重点是高温。

Nuclear fusion, if harnessed, could provide almost limitless carbon free energy. It could alsoresolve issues of proliferation and long-lived radioactive waste that have prevented nuclearfission from becoming more wide spread. In order for nuclear fusion to avoid the productionof long-lived radioisotopes only materials with low activation properties can be used incomponents that will undergo neutron irradiation. This greatly limits materials choices,providing some unique challenges for materials scientists. One such challenge is to find amaterial that is suitable for shielding the superconducting magnetic components fromneutrons produced in the reactor. It is crucial that these components are not irradiated byneutrons as neutron-induced heating or irradiation damage would seriously impact reactorefficiency and lifetime. A shielding material is therefore required that has excellent neutronstopping properties whilst not becoming highly active. It must also be mechanically stable atelevated temperatures and withstand large amounts of helium production. One material thathas recently shown promise for this application is tungsten carbide, although its postirradiationmechanical properties are little studied. Whilst the wide use of cementedtungsten carbides has led to extensive research in these materials, the properties ofbinderless tungsten carbide remain less understood. Tungsten carbide without a metal matrixhas often been overlooked due to its lower fracture toughness leading to its poor wearresistance. This makes it an undesirable material in many engineering applications. It does,however, have superior chemical and thermal stability as well as hardness and sputteringresistance. Since the latter properties are undoubtedly more useful in a neutronshielding application than wear resistance, research on the binderless compound is needed.The overall objective of this thesis work is therefore to examine the changes inproperties caused by irradiation. Before this can be achieved, however, its mechanicalbehaviour in the un-irradiated state must be properly understood. This project will aim toexplore this goal, with a focus on elevated temperatures.