Constraints on the incorporation mechanism of chlorine in peralkaline and peraluminous Na2O-CaO-Al2O3-SiO2 glasses
Constraints on the incorporation mechanism of chlorine in peralkaline and peraluminous Na2O-CaO-Al2O3-SiO2 glasses
复制标题
DOI：
10.2138/am.2014.4717
复制
发表时间：
2014-08-01
影响因子：
3.1
通讯作者：
Webb, Sharon L.
中科院分区：
文献类型：
--
作者：
Baasner, Amrei;Hung, Ivan;Webb, Sharon L.
使用 Cl-35、Na-23、Al-27 和 Si-29 魔角旋转 (MAS) 核磁共振 (NMR) 光谱研究了 Cl 在过碱性和过铝质 Na2O-CaO-Al2O3-SiO2 玻璃中的掺入机制，作为声硅熔体的模型系统。 Cl-35 电场梯度的大小和大分布会导致 MAS NMR 实验中信号丢失，再加上 Cl 浓度低和化学位移色散大，意味着即使在最高的可用场中，我们也处于 MAS NMR 的极限。然而，可以很容易地看出全碱性玻璃和过铝玻璃中 Cl 环境的明显差异。在这两种玻璃类型中，Cl 都存在于相对对称的 Na-Ca-Cl 环境中。 Cl-35 化学位移表明 Cl 环境以 Na 阳离子的存在为主，这与玻璃中 5/1 的 Na/Ca 比率一致。过铝玻璃的Cl-35 MAS NMR谱显示出比全碱性玻璃（类似于-100 ppm）更大的化学位移分布和更正的各向同性化学位移（类似于-75 ppm）。它们还具有更大的四极耦合常数和更大的分布，表明过铝玻璃中的无序性更大。尽管 Na/Ca 比率相同，但过铝玻璃中的 Cl 环境中可能存在比全碱性玻璃更多的 Ca 阳离子。在全碱性玻璃中，Na-Ca-Cl环境的形成导致网络改性阳离子数量减少，从而导致玻璃网络聚合。在过铝玻璃中没有观察到对玻璃聚合的影响。一些 Cl-35 信号也会在静态光谱中丢失，这表明，类似于全碱性玻璃的 20% 的 Cl，以及类似于全铝玻璃的 70% 的 Cl，必须处于存在足够大的电场梯度的环境中，以致无法观察到由此产生的非常宽的线。这些环境可能只是 Na-Ca-Cl，其电场梯度高于产生观察到的 Cl-35 信号的环境或非桥接 Cl 环境（例如 Al-Cl）。目前混合的 Na2O-CaO 铝硅酸盐玻璃中的 Cl 环境似乎比之前对更简单的玻璃成分的 NMR 光谱研究所预期的更加无序。
Incorporation mechanisms of Cl in peralkaline and peraluminous Na2O-CaO-Al2O3-SiO2 glasses as a model system for phonolitic melts were investigated using Cl-35, Na-23, Al-27, and Si-29 magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The size and large distribution of electric field gradients for Cl-35 causes loss of signal in the MAS NMR experiment arid this, in combination with the low concentration of Cl and the large chemical shift dispersion, means that even at the highest available fields we are at the limits of MAS NMR. Nevertheless clear differences in the Cl environment in peralkaline and peraluminous glasses can readily be seen. In both glass types Cl exists in relatively symmetric Na-Ca-Cl environments. The Cl-35 chemical shift indicates that the Cl environment is dominated by the presence of Na cations, consistent with the Na/Ca ratio of 5/1 in the glasses. Cl-35 MAS NMR spectra of the peraluminous glasses show a larger chemical shift distribution and a more positive isotropic chemical shift, similar to-75 ppm, than the peralkaline glasses, similar to-100 ppm. They also have a larger quadrupole coupling constant with a larger distribution, indicating greater disorder in the peraluminous glasses. It is likely that there are more Ca cations present in the Cl environments in the peraluminous glasses than in the peralkaline glasses despite their having the same Na/Ca ratio. In the peralkaline glasses the formation of Na-Ca-Cl environments leads to a decrease in the number of network-modifying cations, which causes a polymerization of the glass network. No effect on the glass polymerization was observed in the peraluminous glasses. Some Cl-35 signal is also lost in the static spectra indicating that similar to 20% of Cl for a peralkaline glass and more than similar to 70% for a peraluminous glass must be in environments where there is a large enough electric field gradient that the resulting very broad line is unobservable. These environments could be simply Na-Ca-Cl with higher electric field gradients than those producing the observed Cl-35 signal or non-bridging Cl environments like for example Al-Cl. The Cl environment in the present mixed Na2O-CaO aluminosilicate glasses appears to be more disordered than was to be expected from previous NMR spectroscopic studies on simpler glass compositions.