Stabilising elements in high oxygen coordination numbers: topo-structural implication on glass strength

玻璃拓扑通常描述结构元素在玻璃结构中的短到中间排列，约束理论的最新进展已成功地用于预测某些玻璃系统的力学性能。在这里，我们将使用多种方法来表征玻璃网络的实际拓扑结构：将使用最先进的固态核磁共振波谱来表征中短长度尺度上的玻璃拓扑结构。虽然高分辨率(多量子)魔角旋转核磁共振实验提供了关于短程结构基元(1-2？)的决定性信息，从而允许识别网络多面体的性质，但利用基于现代同核和异核偶极的全部核磁共振实验，在中等长度尺度(2-8？)上追踪结构基元，将使我们能够阐明已识别的网络多面体向扩展玻璃网络的互连。X射线吸收近边结构(XANES)光谱和红外和拉曼光谱等互补技术的结果将有助于完善玻璃拓扑结构的描述。具有低浓度非桥氧的玻璃体系被认为是获得更强玻璃的首选组成，因此，主要由共价键组成。与局部增加的配位数的组合可能由于增加了堆积密度而提供优势，但这可能取决于具有更多离子(Al)或更共价特征(Si)的高配位原子的成键情况。中短长度尺度上的拓扑结构发现将与微观和纳米压痕实验、布里渊光谱分析和(合作)原位力学测试获得的力学数据相关联。其目的不仅是了解杨氏模量、抗裂性、断裂韧性和硬度是如何受不同长度尺度上的玻璃拓扑控制的，而且还为获得强度显著提高的玻璃铺平了道路。

Glass topology usually describes the short-to-intermediate arrangement of structural elements in the glass structure, and recent advances in the constraint theory have been successfully used to predict mechanical properties of certain glass systems. Here, we will characterise the actual topology of the glass network employing a combination of methods: State of the art solid-state NMR spectroscopy will be used to characterize the glass topology on short and intermediate length scales. While high resolution (Multiple Quantum) Magic Angle Spinning NMR experiments provide decisive information about short range structural motifs (1 - 2 Å) and thus allows to identify the nature of the network polyhedra, the employment of the full inventory of modern homo- and heteronuclear dipolar based NMR experiments, tracing structural motifs on an intermediate length scale (2 - 8 Å) will enable us to elucidate the interconnection of the identified network polyhedra towards an extended glass network. Results from complementary techniques such as X-ray absorption near edge structure (XANES) spectroscopy and infra-red and Raman spectroscopy will help to refine the description of glass topology .Glass systems with low concentrations of non-bridging oxygens and, thus, consisting of mostly covalent bonds are considered the compositions of choice to achieve stronger glasses. The combination with locally increased coordination numbers may offer advantages owing to increased packing densities, but this may depend on the bonding situation of the atom in high coordination being of a more ionic (Al) or a more covalent character (Si). The topo-structural findings on short and intermediate length scales will be correlated with mechanical data obtained from micro- and nanoindentation experiments, Brillouin spectroscopy and (in collaboration) in situ mechanical testing. The aim is not only to understand how Young's modulus, crack resistance, fracture toughness and hardness are controlled by the glass topology on various length scales, but to pave the way towards glasses with significantly increased strength.