Network polymerization and cation coordination environments in boron-bearing rhyolitic melts: Insights from 17O, 11B, and 27Al solid-state NMR of sodium aluminoborosilicate glasses with varying boron content
Network polymerization and cation coordination environments in boron-bearing rhyolitic melts: Insights from 17O, 11B, and 27Al solid-state NMR of sodium aluminoborosilicate glasses with varying boron content
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含硼流纹岩熔体中的网络聚合和阳离子配位环境：来自不同硼含量铝硼硅酸钠玻璃的 17O、11B 和 27Al 固态 NMR 的见解
DOI：
10.1016/j.gca.2019.10.010
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发表时间：
2020
影响因子：
5
通讯作者：
Sung Keun Lee
中科院分区：
文献类型：
--
作者：
A. C. Lee;Sung Keun Lee
尽管对核废料玻璃的溶解行为和含硼流纹岩熔体的性质具有地球化学意义，但从原子水平上详细了解硼含量对含硼硅酸盐玻璃结构特征的影响仍然是难以捉摸的。本文利用多核磁共振技术研究了钠长石(NaAlSiO4)-孔雀石(NaBSiO4)和钠长石(NaAlSi3O8)-辉长石(NaBSi3O8)连接体系中B/Al和Si/B比对Na2O-Al_2O_3-B_2O_3-SiO_2玻璃的局域构型和网络聚合度的影响。11B核磁共振结果证实，随着B/Al和Si/B比的增加，B的配位数从3([3]B)增加到4([4]B)。~(27)Al核磁共振谱表明，除NaAl_(0.25)B_(0.75)SiO_4玻璃外，Al主要以四配位形式存在，并含有少量的[5]Al物种，说明在Al配位环境中，Si对B的控制作用更为显著。~(17)O核磁共振谱可分辨不同的桥基(BO、Si−O−Al、Al−O−Al、Si−O−Si、B−O−B和Si−O−B)和非桥氧(NbO、Na−O−Si)。相反，B-−-O-−-Al物种的不存在证实了B和Al之间的分离和普遍的熔体解聚只存在于硅酸盐网络中。随着B/Al比的增加，B-−-O-−-B和Na-−-NbO组分增加，导致玻璃的溶解速率显著提高。当组成达到一定的硼含量时，急剧增加也表明相对较弱的键，如B−O−B和Na−O−Si的连接性增强。这与熔体粘度随B2O组分的增加而降低有关。根据不同组成的11B核磁共振谱中[3，4]B的测量分数，估计了钠铝硼硅酸盐熔体中硼同位素组成的演化趋势，证实了随着硼含量的增加，10B优先富集到流纹岩熔体中。[3]B组分随Si/B的增加而减少，这可能是俯冲带深部含硼火山岩中δ11B减少的部分原因。结果表明，为了准确解释弧形火山熔岩的熔体粘度、硼同位素组成和核废料玻璃的溶解速率，应限制成分引起的原子结构变化。
Despite the geochemical implications for the dissolution behaviors of nuclear waste glasses and the properties of boron-bearing rhyolitic melts, a detailed atomic-level understanding of the overall effect of boron content on the structural characteristics of boron-bearing silicate glasses remains elusive. Herein, we explore the effects of B/Al and Si/B ratios on the local configurations around cations and the degree of network polymerization of Na2O-Al2O3-B2O3-SiO2glasses in nepheline (NaAlSiO4) – malinkoite (NaBSiO4) and albite (NaAlSi3O8) – reedmergnerite (NaBSi3O8) joins using multi-nuclear magnetic resonance (NMR). The11B NMR results confirmed an increase in the B coordination numbers from 3 ([3]B) to 4 ([4]B) as B/Al and Si/B ratios increase. The27Al NMR spectra show that the Al is mainly four coordinated, except in NaAl0.25B0.75SiO4glasses, with a minor amount of[5]Al species, revealing a more prominent control of Si over that of B on the Al coordination environments. The17O NMR spectra resolve distinct bridging (BO, Si−O−Al, Al−O−Al, Si−O−Si, B−O−B, and Si−O−B) and non-bridging oxygens (NBO, Na−O−Si). In contrast, the absence of B−O−Al species confirmed the separation between B and Al and prevalent melt depolymerization exclusively in silicate-networks. The fractions of B−O−B and Na−NBO increase as B/Al ratio increases, accounting for a drastic enhancement in the dissolution rate of glasses. A dramatic increase also indicates an enhanced connectivity of relatively weaker bonds such as B−O−B and Na−O−Si as composition reached a certain boron content. This is linked to a decrease in the melt viscosity with increasing B2O3component. Based on the measured fractions of[3,4]B in11B NMR spectra with varying composition, the trend of the evolution of boron isotope composition in sodium aluminoborosilicate melts was estimated, confirming the preferential enrichment of10B into rhyolitic melts with increasing boron content. The decreased fraction of[3]B species with increasing Si/B may partly explain the reduction in δ11B in boron-bearing volcanic rocks at deeper depths in the subduction zone. The results suggest that composition-induced changes in the atomic structures should be constrained to precisely interpret the melt viscosity, boron isotope composition of arc volcanic lavas, and the dissolution rates of nuclear waste glasses.
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影响因子：
5
作者：
P. Kowalski;B. Wunder;Sandro Jahn Gfz German Research Centre for Geosciences-Sandro-Jahn-Gfz-German-Research-Centre-for-103271123;Telegrafenberg;Potsdam;H Germany-
通讯作者：
P. Kowalski;B. Wunder;Sandro Jahn Gfz German Research Centre for Geosciences-Sandro-Jahn-Gfz-German-Research-Centre-for-103271123;Telegrafenberg;Potsdam;H Germany-
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影响因子：
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