Boron environments in Pyrex® glass--a high resolution, Double-Rotation NMR and thermodynamic modelling study.
Boron environments in Pyrex® glass--a high resolution, Double-Rotation NMR and thermodynamic modelling study.
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Pyrex® 玻璃中的硼环境 - 高分辨率、双旋转 NMR 和热力学建模研究。
DOI：
10.1039/c1cp20771g
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
R. Dupree
中科院分区：
文献类型：
--
作者：
A. Howes;N. Vedishcheva;A. Samoson;A. Samoson;J. Hanna;Mark E. Smith;D. Holland;R. Dupree
以重要的技术玻璃 Pyrex® 为例，结果表明，一维和二维 (11)B 双旋转 (DOR) NMR 实验与热力学模型相结合，能够提供复杂玻璃的独特结构信息。 (11)B DOR NMR 已应用于 Pyrex® 玻璃，以消除 NMR 线的偶极和四极展宽，从而产生高分辨率光谱，从而可以进行明确、准确的峰拟合，这在 3 配位 [BO(3)] (B3) 三角平面环境中尤其重要。获得的数据质量足够好，可用于测试基于热力学的相关解模型预测的硼酸盐和硼硅酸盐上层结构单元的分布。该模型预测 Pyrex® 玻璃中主要的含硼化学基团是与 B(2)O(3) 和四硼酸钠相关的化学基团（含有少量的三硼酸钠、二硼酸钠、五硼酸钠、铁锰矿和芦镁锰矿）。如果将各向同性化学位移为 -1.4 ppm 和 0.5 ppm 的 (11)B 峰分别分配给来自硼硅酸盐单元（[B(OSi)(4)] 和 [B(OSi)(3)(OB)]）和硼酸盐上层结构单元（主要是带有一些五硼酸盐和二硼酸盐的三硼酸盐环）的 B4 物质，则模型和实验之间发现了极好的一致性。然后，各向同性位移为 14 ppm 和 18.1 ppm 的峰分别分配给硼酸盐上层结构单元中的 B3（主要是三硼酸盐和五硼酸盐以及连接的 B3）和硼氧醇环。 DOR NMR 峰的分配得到了 (11)B 自旋扩散 DOR NMR 光谱中交叉峰的支持，该光谱可用于开发结构模型，其中 B(2)O(3) 类区域通过硼酸盐和硼硅酸盐超结构单元连接到主要的二氧化硅网络。因此，Pyrex® 被证明具有异质结构，具有不同的分子群，远离仅具有短程有序的网络多面体的随机分布。
It is shown, using the important technological glass Pyrex® as an example, that 1D and 2D (11)B Double-Rotation (DOR) NMR experiments, in combination with thermodynamic modelling, are able to provide unique structural information about complex glasses. (11)B DOR NMR has been applied to Pyrex® glass in order to remove both dipolar and quadrupolar broadening of the NMR lines, leading to high resolution spectra that allow unambiguous, accurate peak fitting to be carried out, of particular importance in the case of the 3-coordinated [BO(3)] (B3) trigonal planar environments. The data obtained are of sufficient quality that they can be used to test the distributions of borate and borosilicate superstructural units predicted by the thermodynamics-based Model of Associated Solutions. The model predicts the dominant boron-containing chemical groupings in Pyrex® glass to be those associated with B(2)O(3) and sodium tetraborate (with smaller amounts of sodium triborate, sodium diborate, sodium pentaborate, danburite and reedmergnerite). Excellent agreement is found between model and experiment provided the (11)B peaks with isotropic chemical shifts of -1.4 ppm and 0.5 ppm are assigned to B4 species from borosilicate units ([B(OSi)(4)] and [B(OSi)(3)(OB)]) and borate superstructural units (mainly triborate rings with some pentaborate and diborate) respectively. The peaks with isotropic shifts of 14 ppm and 18.1 ppm are then assigned to B3 in borate superstructural units (mainly triborate and pentaborate along with connecting B3) and boroxol rings respectively. The assignments of the DOR NMR peaks, are supported by the presence of cross-peaks in (11)B spin-diffusion DOR NMR spectra which can be used to develop a structural model in which B(2)O(3)-like regions are linked, via borate and borosilicate superstructural units, to the majority silica network. Pyrex® is thus shown to have a heterogeneous structure, with distinct molecular groupings that are far removed from a random distribution of network polyhedra with only short-range order.
影响因子：
3.3
作者：
Barrow, Nathan S.;Yates, Jonathan R.;Brown, Steven P.
通讯作者：
Brown, Steven P.