The role of water in coesite crystallization from silica gel
The role of water in coesite crystallization from silica gel
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DOI：
10.1127/0935-1221/2013/0025-2331
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发表时间：
2013-10-01
影响因子：
2.1
通讯作者：
Arai, Shoji
中科院分区：
文献类型：
--
作者：
Arasuna, Akane;Okuno, Masayuki;Arai, Shoji
利用拉曼光谱、红外光谱和X射线衍射仪研究了硅胶在5 Gpa和100℃压缩1小时后的结构变化。在本实验条件下，非粉状硅胶样品完全晶化为柯石英，表明在较低的温度和较短的结晶时间下，硅胶仍能很容易地晶化成柯石英。这可能是因为硅胶的平均结构是由SiO4四面体的四元环主导的，由于硅醇(Si-OH)的存在导致了较少聚合的网络结构，而SiO4四面体的较大的环结构，如六元环和八元环，在压力下被水分子破坏。这些性质可能导致硅胶样品中SiO4四面体的连续聚合和重构，从而容易形成柯石英网状结构。这说明了硅醇和水分子对柯石英形成的贡献的重要性。
Structural changes in silica gel after compression to 5 GPa and 100 degrees C for one hour were investigated using Raman and IR spectroscopies and X-ray diffraction measurements. The non-powdered silica gel sample was entirely crystallized to coesite under these experimental conditions, showing that the crystallization of silica gel to coesite can be readily achieved in spite of the low temperature conditions and short duration. This behavior may result because the average structure of silica gel is dominated by four-membered rings of SiO4 tetrahedra, there is a less-polymerized network structure due to the presence of silanol (Si-OH), and larger ring structures, such as 6- and 8-membered rings, of SiO4 tetrahedra are disrupted by water molecules under pressure. These properties may lead to successive polymerization and reconstruction of the SiO4 tetrahedra in the bulk silica-gel sample, enabling the easy formation of the coesite-like network structure. This shows the importance of the contribution of silanol and water molecules for coesite formation.