Structural characteristics of novel Ca-Mg orthosilicate and suborthosilicate glasses: results from 29Si and 17O NMR spectroscopy.
Structural characteristics of novel Ca-Mg orthosilicate and suborthosilicate glasses: results from 29Si and 17O NMR spectroscopy.
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新型 Ca-Mg 原硅酸盐和次原硅酸盐玻璃的结构特征：29Si 和 17O NMR 光谱的结果。
DOI：
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发表时间：
2012
影响因子：
3.3
通讯作者：
G. Papatheodorou
中科院分区：
文献类型：
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作者：
N. Nasikas;T. Edwards;S. Sen;G. Papatheodorou
利用高分辨（29）Si和（17）O核磁共振谱研究了新型碱土次正硅酸盐玻璃沿着（1 - x）（Ca（0.5）Mg（0.5）O）- xSiO（2）（0.28 ≤ x ≤ 0.33）组成连接的结构特征。这些玻璃的结构由孤立的Q（0）和Q（1）阴离子物种以及通过库仑相互作用结合在一起的Mg（2+）和Ca（2+）抗衡阳离子组成。随着SiO（2）含量的降低，Q（1）物种的浓度迅速降低，在x = 28mol%的玻璃中检测不到。这些玻璃的物理性质，如玻璃化转变温度和密度的组成变化可以归因于结构中的Q-物种。NBO与其最近邻配位壳层中碱土金属阳离子的随机分布有关。不同的Ca-NBO和Mg-NBO配位多面体的随机堆积可能会引起结构和拓扑挫折，这是这些具有极低SiO（2）含量的次正硅酸盐液体具有不寻常的玻璃形成能力的原因。最后，Q（1）物质的组成和形成需要在这些玻璃的结构中形成仅与Mg（2+）和Ca（2+）阳离子键合的游离O（2-）离子。在这项研究中提出的（17）O NMR结果允许直接观察到的氧物种。
The structural characteristics of novel alkaline-earth suborthosilicate glasses along the compositional join (1 - x)(Ca(0.5)Mg(0.5)O) - xSiO(2) with 0.28 ≤ x ≤ 0.33 are investigated using high resolution (29)Si and (17)O nuclear magnetic resonance spectroscopy. The structures of these glasses consist of isolated Q(0) and Q(1) anionic species and Mg(2+) and Ca(2+) countercations that are held together by Coulombic interactions. The concentration of the Q(1) species rapidly decreases with decreasing SiO(2) content and becomes undetectable in the glass with x = 28 mol %. The compositional variation of the physical properties of these glasses such as glass transition temperature and density can be attributed to the Q-speciation in the structure. The NBOs are associated with a random distribution of the alkaline-earth cations in their nearest neighbor coordination shell. The resulting random packing of dissimilar Ca-NBO and Mg-NBO coordination polyhedra may give rise to structural and topological frustration responsible for the unusual glass-forming ability of these suborthosilicate liquids with extremely low SiO(2) contents. Finally, the composition and the formation of Q(1) species necessitate the formation of free O(2-) ions in the structure of these glasses that are only bonded to Mg(2+) and Ca(2+) cations. The (17)O NMR results presented in this study allow for direct observation of such oxygen species.