Positronium Study of Structural Nanovoids in Model Glasses

高放射性核废料通过与玻璃混合而被固定，以便安全储存1000多年。这些放射性核素被限制在放射性废物玻璃(RWG)的固有结构纳米空洞中，通常是SiO_2-B2O_3基玻璃。因此，研究纳米空穴在长期储存过程中如何被放射性核素原子(离子)占据并在辐照环境下保持稳定是非常重要的。我们采用了两种独立的实验方法来获得纳米空洞中形成的正电子(Ps)的平均半径，平均半径是由Ps的拾取湮没时间hSetime得到的，使用的是Tao-Eldrup-Nakanishi-Wang-Jean模型和正电子湮没动量分布的二维角关联(2D-ACAR)的零点气泡模型。在SiO_2基模型玻璃中，除了根据含Fe杂质的玻璃的拾取寿命计算出稍小的半径外，两种实验得到的平均半径彼此吻合。属于网络修饰剂(Li、Na和K)的掺杂氧化物的平均半径随着掺杂氧化物摩尔分数的增加而迅速减小，因为氧化物的阳离子占据纳米空穴的大小顺序为纳米空穴，半径随掺杂氧化物的摩尔分数的增加表现出缓慢的线性变化。网络状氧化物(B_2O_3、Al_2O_3)的存在，表明较结实的网络状氧化物存在于玻璃结构处。网络，但不是在纳米空洞内。这些发现为我们深入研究结构纳米空穴提供了一个有用的工具，并为研究RWG在长期储存过程中的稳定性提供了一种有前途的工具。

High-level radioactive nuclear waste is are immobilised by mixing it with glass to be stored safely for a long time more than 1000 years. These radioactive nuclides are confined in the intrinsic structural nanovoids of the radioactive waste glasses (RWG), usually SiO_2-B2O_3 based glasses. Thus it is very important to study haw the nanovoids are occupied by the radioactive nuclide atoms (ions) and stable under the irradiation environment during the long-term storage.Many kinds of SiO_2 based model glasses were prepared. We employed two independent experimental methods of positronium (Ps) formed in the nanovoids to obtain average radius of the nanovoids, the average radii are obtained from pick off annihilation hSetime of Ps using Tao-Eldrup-Nakanishi-Wang-Jean model and from two-dimensional angular correlation of positron annihilation (2D-ACAR) momentum distribution using a zero-point bubbles model.In SiO_2 based model glasses, the average radii from the two experiments agree well with each other except fix slightly smaller radii from the pick-off lifetimes in the glasses containing Fe impurities. The average radius of the nanovoids decreases rapidly with increasing the mole fraction of the doped oxides which belong to the network modifiers (Li, Na and K)because the cation of the oxides occupy nanovoids in the order of the size of them The radius show sluggish and linear change with the fraction. Of the network loaner oxides (B_2O_3, Al_2O_3), which exhibits that the network firmer oxides are incorporated at the glass structural. Networks but not within nanovoids. These findings give us useful into oration on the structural nanovoids and suggest a promising tool for the study of the stability of the RWG during the long-term storage.