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Structural role of ZrO 2 and its impact on properties of boroaluminosilicate nuclear waste glasses
npj Materials Degradation ( IF 6.6 ) Pub Date : 2018-06-22 , DOI: 10.1038/s41529-018-0041-6
Xiaonan Lu , Lu Deng , Sebastien Kerisit , Jincheng Du

Addition of zirconia (ZrO2) to nuclear waste glasses, even in small amount, significantly affects physical properties such as chemical durability, density, viscosity, and glass transition temperature. Hence ZrO2 plays an important role in the development of nuclear waste glass compositions. It was found recently that addition of zirconia decreases the initial dissolution rate but increases long-term dissolution by changing the protective properties such as porosity of alteration layers. In this study, the International Simple Glass (ISG) with different amounts of ZrO2/SiO2 substitution was simulated using classical molecular dynamics (MD) simulations and recently developed composition-dependent potential sets. Local structural descriptors such as bond distances, bond angle distributions, and coordination numbers were systematically studied and compared with experimental values. Zr K-edge extended X-ray absorption fine structure spectra were also calculated and compared with experiment to resolve the local coordination environment around Zr. Medium-range structural information (e.g., Qn distribution, network connectivity, and ring-size distribution) showed that ZrO2/SiO2 substitution increases the overall network connectivity and the amount of smaller sized rings, which will decrease the initial dissolution rate by strengthening the glass network and limiting water diffusivity. Finally, diffusion and dynamic properties of the ions were studied and discussed to develop a better understanding of the chemical durability of these glasses.



中文翻译:

ZrO 2的结构作用及其对硼铝硅酸盐核废玻璃性能的影响

即使将少量的氧化锆(ZrO 2)添加到核废玻璃中,也会显着影响物理性能,例如化学耐久性,密度,粘度和玻璃化转变温度。因此,ZrO 2在核废玻璃组合物的开发中起着重要作用。最近发现,添加氧化锆降低了初始溶解速率,但是通过改变了诸如变质层的孔隙率之类的保护性能而增加了长期溶解。在这项研究中,具有不同ZrO 2 / SiO 2含量的国际简单玻璃(ISG)取代是使用经典的分子动力学(MD)模拟和最近开发的依赖成分的电位集进行模拟的。系统研究了局部结构描述符,例如键距,键角分布和配位数,并将其与实验值进行了比较。计算了Zr K-edge扩展的X射线吸收精细结构光谱,并与实验进行了比较,以解决Zr周围的局部配位环境。中等范围的结构信息(例如Q n分布,网络连接性和环大小分布)显示ZrO 2 / SiO 2取代增加了整个网络的连通性,并增加了较小尺寸的环的数量,这将通过加强玻璃网络并限制水的扩散性而降低初始溶解速率。最后,对离子的扩散和动态特性进行了研究和讨论,以更好地理解这些玻璃的化学耐久性。

更新日期:2019-05-16
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