Chowdhury Sanjib, Manara Dario, Dieste-Blanco Oliver, Robba Davide, Gonçalves António Pereira
C2TN, DECN, Instituto Superior Técnico, Campus Tecnológico e Nuclear, Universidade de Lisboa, Estrada Nacional 10, 2695-066 Bobadela LRS, Portugal.
Joint Research Centre (JRC), European Commission, Directorate of Nuclear Safety and Security, P.O. Box 2340, D-76125 Karlsruhe, Germany.
Materials (Basel). 2021 Sep 25;14(19):5568. doi: 10.3390/ma14195568.
Nanograined nuclear materials are expected to have a better performance as spallation targets and nuclear fuels than conventional materials, but many basic properties of these materials are still unknown. The present work aims to contribute to their better understanding by studying the effect of grain size on the melting and solid-solid transitions of nanograined UC. We laser-heated 4 nm-10 nm grain size samples with UC as the main phase (but containing graphite and UO as impurities) under inert gas to temperatures above 3000 K, and their behavior was studied by thermal radiance spectroscopy. The UC solidification point (2713(30) K) and α-UC to β-UC solid-solid transition temperature (2038(10) K) were observed to remain unchanged when compared to bulk crystalline materials with micrometer grain sizes. After melting, the composite grain size persisted at the nanoscale, from around 10 nm to 20 nm, pointing to an effective role of carbon in preventing the rapid diffusion of uranium and grain growth.
与传统材料相比，纳米晶核材料有望作为散裂靶材和核燃料具有更好的性能，但这些材料的许多基本特性仍然未知。目前的工作旨在通过研究晶粒尺寸对纳米晶UC的熔化和固-固转变的影响，来促进对它们的更好理解。我们在惰性气体下将以UC为主相（但含有石墨和UO作为杂质）、晶粒尺寸为4纳米至10纳米的样品激光加热到3000 K以上的温度，并通过热辐射光谱研究其行为。与具有微米晶粒尺寸的块状晶体材料相比，观察到UC的凝固点（2713(30) K）和α-UC到β-UC的固-固转变温度（2038(10) K）保持不变。熔化后，复合晶粒尺寸在纳米尺度上持续存在，从约10纳米到20纳米，这表明碳在防止铀的快速扩散和晶粒生长方面起到了有效作用。
