Patel Karishma B, Schuller Sophie, Lampronti Giulio I, Farnan Ian
Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB23EQ, UK.
Phys Chem Chem Phys. 2020 Jul 21;22(27):15616-15631. doi: 10.1039/d0cp02447c. Epub 2020 Jul 3.
A fundamental approach was taken to understand the implications of increased nuclear waste loading in the search for new materials for long-term radioisotope encapsulation. This study focused on the formation and radiation tolerance of glass ceramics with selectively induced CaMoO as a form to trap the problematic fission product molybdenum. Several samples were synthesised with up to 10 mol% MoO within a soda lime borosilicate matrix, exhibiting phase separation on the nano scale according to thermal analysis, which detected two glass transition temperatures. It is predicted that these two phases are a result of spinodal decomposition with Si-O-Ca-O-Si and Si-O-Ca-O-B units, with the latter phase acting as a carrier for MoO. The solubility limit of molybdenum within this matrix was 1 mol%, after which crystallisation of CaMoO occurred, with crystallite size (CS) increasing and cell parameters decreasing as a function of [MoO]. These materials were then subjected to irradiation with 7 MeV Au ions to replicate the nuclear interactions resulting from α-decay. A dose of 3 × 10 ions per cm was achieved, resulting in 1 dpa of damage within a depth of ∼1.5 μm, according to TRIM calculations. Glasses and glass ceramics were then analysed using BSE imaging, XRD refinement, and Raman spectroscopy to monitor changes induced by accumulated damage. Irradiation was not observed to cause any significant changes to the residual amorphous network, nor did it cause amorphisation of CaMoO based on the relative changes to particle size and density. Furthermore, the substitution of Ca to form water-soluble Na/NaGd-MoO assemblages did not occur, indicating that CaMoO is resilient to chemical modification following ion interactions. Au-irradiation did however cause CaMoO lattice parameter expansion, concurrent to growth in CS. This is predicted to be a dual parameter mechanism of alteration based on thermal expansion from electronic coupling, and the accumulation of defects arising from atomic displacements.
为了寻找用于长期放射性同位素封装的新材料，我们采用了一种基本方法来理解增加核废料负载的影响。本研究聚焦于以选择性诱导CaMoO形式捕获有问题的裂变产物钼的微晶玻璃的形成及其耐辐射性。在钠钙硼硅酸盐基体中合成了几种含高达10 mol% MoO的样品，根据热分析，这些样品在纳米尺度上呈现相分离，检测到两个玻璃化转变温度。据预测，这两个相是由具有Si-O-Ca-O-Si和Si-O-Ca-O-B单元的旋节线分解产生的，后一相作为MoO的载体。钼在该基体中的溶解度极限为1 mol%，超过此极限后CaMoO开始结晶，微晶尺寸（CS）随着[MoO]的增加而增大，晶胞参数减小。然后用7 MeV的金离子对这些材料进行辐照，以模拟α衰变产生的核相互作用。根据TRIM计算，实现了每平方厘米3×10个离子的剂量，在约1.5μm的深度内造成了1 dpa的损伤。然后使用背散射电子成像、XRD精修和拉曼光谱对玻璃和微晶玻璃进行分析，以监测累积损伤引起的变化。未观察到辐照对残余非晶网络造成任何显著变化，基于粒径和密度的相对变化，也未导致CaMoO非晶化。此外，未发生钙的取代以形成水溶性的Na/NaGd-MoO组合，这表明CaMoO在离子相互作用后对化学改性具有抗性。然而，金离子辐照确实导致CaMoO晶格参数膨胀，同时CS增大。据预测，这是一种基于电子耦合热膨胀和原子位移产生的缺陷积累的双重参数变化机制。
