As important energy materials, uranium and its alloys have been widely used in the fields of material sciences and nuclear industrial applications. Applying metal and/or ceramic surface protective coatings can effectively retard easy corrosion of uranium with extremely high chemical activity. In principle, ideal surface protective coatings should possess (1) lowered density of elongated diffusion pathways (i.e. grain boundaries and growth defects) and (2) improved interfacial bonding to substrate by preventing corrosion medium from reacting with uranium. In this work, we have demonstrated that by magnetron-sputtering amorphous AlO (a-AlO) interlayers within Al coatings on depleted uranium (DU), the corrosion resistance is significantly improved as indicated by corrosion potential datum DU substrate (−645 mV), DU with mono-layer Al coating (−610 mV) and DU with Al/a-AlO/Al tri-layer coating (−550 mV). Diffusion pathways are elongated with misalignment of columnar grain boundaries in Al coatings around a-AlO interlayers. Meanwhile, density of diffusion pathways is lowered since a-AlO does not contain conventional crystal defects, and can suppress accumulation and facilitate outgassing of Ar bubbles as major growth defects. The effect of coating/substrate interfacial bonding on corrosion behavior is investigated by introduction of intermixing layers between Al- and UO-rich interfacial regions. A strategy to improve anti-corrosion stability of Al/a-AlO/Al tri-layer coating by optimizing degree of intermixing is proposed. The present findings may shed lights on compositional and microstructural design of anti-corrosion coatings on uranium and its alloys.

中文翻译：

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揭示磁控溅射在贫铀上沉积的Al/非晶Al2O3/Al三层涂层的微观结构和相关腐蚀机制

铀及其合金作为重要的能源材料，在材料科学和核工业应用领域有着广泛的应用。应用金属和/或陶瓷表面防护涂层可以有效地延缓化学活性极高的铀的易腐蚀。原则上，理想的表面保护涂层应具有（1）降低细长扩散路径（即晶界和生长缺陷）的密度，以及（2）通过防止腐蚀介质与铀反应来改善与基材的界面结合。在这项工作中，我们证明，通过在贫铀（DU）上的铝涂层内磁控溅射非晶Al2O（a-Al2O）中间层，耐腐蚀性能显着提高，如腐蚀电位数据DU基板（−645 mV）所示， DU 具有单层 Al 涂层 (−610 mV) 和 DU 具有 Al/a-Al2O3/Al 三层涂层 (−550 mV)。由于 a-Al2O3 中间层周围的铝涂层中柱状晶界的错位，扩散路径被拉长。同时，由于a-Al2O3不包含传统的晶体缺陷，因此扩散路径的密度降低，并且可以抑制作为主要生长缺陷的Ar气泡的积累并促进其脱气。通过在富铝和富铀界面区域之间引入混合层，研究了涂层/基体界面结合对腐蚀行为的影响。提出了一种通过优化混合程度来提高 Al/a-Al2O3/Al 三层涂层防腐稳定性的策略。目前的发现可能有助于铀及其合金防腐涂层的成分和微观结构设计。