Development and Application of Space- and Time-Resolved Hyperspectral Raman Imaging to in situ Study Mineral- and Glass-Water Reactions

空间和时间分辨高光谱拉曼成像的开发和应用，用于原位研究矿物和玻璃水反应

• 批准号: 389799517
• 负责人: Professor Dr. Thorsten Geisler-Wierwille
• 金额: --
• 依托单位: Institut für Geowissenschaften
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/389799517?language=en
• 关键词: Development; Application; Space; Time; Resolved

Solid-water reactions are often characterized by the formation of surface alteration layers that complexly affect the dissolution behaviour of the solid. Despite numerous sophisticated experimental studies, there is still an intensive debate about how these alteration layers form and about the rate-limiting reaction step. New insights into the mesoscopic partial reactions underlying their formation can be gained from confocal hyperspectral Raman spectroscopy (CHRS). This technique allows real-time imaging of moving reaction interfaces during fluid-mediated replacement reactions at the micrometer-scale and under elevated temperatures with the use of fluid cells (FC), omitting the imperative to interrupt the replacement reaction. FC CHRS thereby can provide a wealth of information such as, e.g., phase composition, crystallinity, interfacial strain, and, at the same time, the concentration of aqueous species in the solution, from which, in some cases, even the local pH could be determined. Moreover, due to the isotope shift of vibrational modes FC CHRS additionally facilitates to follow the exchange of oxygen and hydrogen isotopes among solids and aqueous molecular species, if isotopically enriched precursors are used. Intriguing proofs of concepts for such in situ FC CHRS studies are given by the results of first experiments which were performed to study the aqueous corrosion of borosilicate glass at 70°C and the replacement of celestine by strontianite in a sodium carbonate solution at 21°C. The experiments were carried out in home-made fluid cells with a sample arrangement that allows measuring the solution and the formation of the reaction product with a micrometer resolution. The results of these experiments are very encouraging. They revealed, in both cases, unpredicted, short-term changes in the mechanism and the overall reaction kinetics. They further demonstrate that dynamic phenomena such as re-equilibration reactions and potentially the diffusion of molecular water through the product layer can be studied and quantified when using 18-O and 2-H as tracers. FC CHRS thus potentially opens up the possibility to gain deeper insights into solid-water reactions. The main objectives of the here proposed project are (A) to develop/advance and eventually establish the experimental method, (B) to in situ study the mesoscopic mechanism(s), and (C) to identify and quantify the rate-limiting steps controlling the corrosion of borosilicate glasses and the replacement of celestine by strontianite at elevated temperatures. The planned experiments will deliver unique insights into the mechanism(s) and kinetics of replacement reactions in aqueous solutions, providing the basis to develop and test numerical models.

固水反应的特征通常是形成表面蚀变层，这复杂地影响固体的溶解行为。尽管进行了大量复杂的实验研究，但关于这些蚀变层如何形成以及限速反应步骤仍然存在激烈的争论。通过共焦高光谱拉曼光谱（CHRS）可以获得对其形成背后的介观部分反应的新见解。该技术允许在微米级的流体介导的置换反应期间和在高温下使用流体池（FC）对移动反应界面进行实时成像，从而无需中断置换反应。因此，FC CHRS 可以提供丰富的信息，例如相组成、结晶度、界面应变，同时还可以提供溶液中水性物质的浓度，在某些情况下，甚至可以确定局部 pH 值。此外，由于振动模式的同位素位移，如果使用同位素富集的前体，FC CHRS 还有助于跟踪固体和水分子物质之间氧和氢同位素的交换。首次实验的结果为此类原位 FC CHRS 研究的概念提供了有趣的证明，这些实验的目的是研究 70°C 下硼硅酸盐玻璃的水腐蚀以及 21°C 碳酸钠溶液中用菱锶矿替代天青石。实验是在自制的流体池中进行的，其样品装置可以以微米分辨率测量溶液和反应产物的形成。这些实验的结果非常令人鼓舞。他们在这两种情况下都揭示了机制和整体反应动力学的不可预测的短期变化。他们进一步证明，当使用 18-O 和 2-H 作为示踪剂时，可以研究和量化动态现象，例如再平衡反应和分子水通过产物层的潜在扩散。因此，FC CHRS 可能为深入了解固水反应提供了可能性。这里提出的项目的主要目标是（A）开发/推进并最终建立实验方法，（B）原位研究介观机制，以及（C）识别和量化控制硼硅酸盐玻璃腐蚀和在高温下用菱锶矿替代天青石的限速步骤。计划中的实验将为水溶液中置换反应的机制和动力学提供独特的见解，为开发和测试数值模型提供基础。