Abstract Yttrium dihydride has been considered as potential nuclear reactor moderator for micro-reactors operating in the thermal energy spectrum due to their ability to retain hydrogen to high temperatures while having a relatively low impact on neutron economy. Despite these advantages, it is difficult to prepare yttrium dihydride in high-density, near net-shape monoliths for moderator applications due to volume expansion upon hydriding and the pyrophoric nature of the material. In this work, high-density monoliths of yttrium dihydride were prepared by direct hydriding and using powder metallurgical methods. Resonant ultrasound spectroscopy was used to measure the elastic moduli of the sintered monoliths, while nanoindentation was used to determine the Young’s modulus and hardness of the directly-hydrided yttrium and the sintered monoliths. Single crystal elastic constants and related properties of yttrium dihydride were also determined using density functional theory (DFT) for comparison. Mechanical properties of materials produced by both methods were observed to be consistent with the values from literature for yttrium dihydride. Due to the novelty of producing yttrium dihydride by powder metallurgy, this result indicated that the monoliths produced by powder metallurgy were of high quality. To that end, powder metallurgy is believed to be a viable method for large-scale production of yttrium dihydride monoliths for nuclear reactor moderator applications.

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二氢化钇高密度烧结整料的弹性模量

摘要 二氢化钇被认为是在热能谱中运行的微型反应堆的潜在核反应堆减速剂，因为它们能够将氢气保持在高温下，同时对中子经济性的影响相对较低。尽管有这些优点，但由于氢化时的体积膨胀和材料的自燃性质，难以在高密度、近净形整料中制备用于减速剂应用的二氢化钇。在这项工作中，通过直接氢化和使用粉末冶金方法制备了高密度的二氢化钇整料。共振超声光谱用于测量烧结整料的弹性模量，而纳米压痕用于确定直接氢化钇和烧结整料的杨氏模量和硬度。为了比较，还使用密度泛函理论 (DFT) 确定了二氢化钇的单晶弹性常数和相关特性。观察到通过两种方法生产的材料的机械性能与文献中关于二氢化钇的值一致。由于粉末冶金生产二氢化钇的新颖性，该结果表明粉末冶金生产的整料是高质量的。为此，粉末冶金被认为是大规模生产用于核反应堆慢化剂应用的二氢化钇整料的可行方法。观察到通过两种方法生产的材料的机械性能与文献中关于二氢化钇的值一致。由于粉末冶金生产二氢化钇的新颖性，该结果表明粉末冶金生产的整料是高质量的。为此，粉末冶金被认为是大规模生产用于核反应堆慢化剂应用的二氢化钇整料的可行方法。观察到通过两种方法生产的材料的机械性能与文献中关于二氢化钇的值一致。由于粉末冶金生产二氢化钇的新颖性，该结果表明粉末冶金生产的整料是高质量的。为此，粉末冶金被认为是大规模生产用于核反应堆慢化剂应用的二氢化钇整料的可行方法。