In situ spectroscopic study of water speciation in the depolymerized Na2Si2O5 melt
In situ spectroscopic study of water speciation in the depolymerized Na2Si2O5 melt
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DOI：
10.1016/j.chemgeo.2015.05.012
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发表时间：
2015-08-20
期刊：
影响因子：
3.9
通讯作者：
Yamashita, Shigeru
中科院分区：
文献类型：
--
作者：
Chertkova, Nadezda;Yamashita, Shigeru
含1.3-8.1重量%的二硅酸钠熔体中的水形态在900 ℃和0.2至1.7 GPa的压力下，使用外部加热的金刚石对顶砧单元，通过近红外光谱研究了总水的含量。含水二硅酸钠熔体在实验中既作为样品又作为压力介质，可以保持熔体的总含水量恒定，从而对水分子的近红外波段的摩尔吸收系数进行内部一致的校准。在所研究的压力范围内没有观察到水形态的压力依赖性，这表明在熔体中以H2O分子为代价形成结构上结合的OH基团伴随着可以忽略不计的体积变化。在900摄氏度，水形态的组成依赖性被发现是弱得多，比预期的从以前报道的数据的低温范围附近的玻璃化转变。这可以通过硅酸钠熔体中的氢键在高温下显著减弱来解释。(C)2015 Elsevier B. V.版权所有。
Water speciation in the sodium disilicate melts containing 1.3-8.1 wt.% of total water was studied by near-infrared spectroscopy at 900 degrees C and pressures from 0.2 to 1.7 GPa using externally heated diamond anvil cell. Hydrous sodium disilicate melt served both as a sample and as a pressure medium in the experiments, which allowed to keep the total water content of the melt constant and thereby to perform an internally consistent calibration of molar absorption coefficients for the near-infrared bands of water species. No pressure dependence of water speciation was observed in the studied pressure range, indicating that formation of structurally bound OH groups at the expense of H2O molecules in the melt is accompanied by a negligible volume change. At 900 degrees C, compositional dependence of water speciation was found to be much weaker than that expected from the previously reported data for low-temperature range near the glass transition. This can be explained by significant weakening of hydrogen bonding in the sodium silicate melts at high temperatures. (C) 2015 Elsevier B.V. All rights reserved.