Dehydration and dehydroxylation of C-S-H phases synthesized on silicon wafers
Dehydration and dehydroxylation of C-S-H phases synthesized on silicon wafers
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DOI：
10.1016/j.apsusc.2017.10.039
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发表时间：
2018-03
影响因子：
6.7
通讯作者：
Nicolás Giraudo;Samuel Bergdolt;Fabrice Laye;Peter Krolla;J. Lahann;P. Thissen
中科院分区：
文献类型：
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作者：
Nicolás Giraudo;Samuel Bergdolt;Fabrice Laye;Peter Krolla;J. Lahann;P. Thissen
在这项工作中，在硅片上合成了特定的硅酸钙-水合硅酸盐（C-S-H）相，并将其转化为C-S相。识别特定的矿物相，并成功控制合成。利用傅里叶变换红外光谱（FTIR）和X射线衍射（XRD）对样品进行了研究，并基于第一性原理计算对结果进行了分析。当C-S-H相转变为C-S相时，在XRD上只检测到少量的反射，并且相干散射畴随着暴露温度和时间的增加而减小。这种行为是由Ca/Si的变化，这是确定在FTIR光谱的变化解释。热力学分析的第一性原理计算的帮助下进行强调的钙硅（Ca/Si）比在脱羟基的过程中的影响。为了增加Ca/Si比，在合成时用甲醇部分取代水。这在FTIR光谱中观察到，并通过较低的脱羟基温度得到证实。钙对脱羟基的催化性质得到证实。这项工作的核心在于准备一个模型，该模型的完善使得使用第一原理计算来模拟反应性，稳定性和机械性能成为可能，并且是许多其他合成的起点。
In this work, the synthesis of specific ultrathin Calcium-Silicate-Hydrate (C-S-H) phases on silicon wafers and their transformation into C-S phases is achieved. Specific mineral phases are identified, and the synthesis is successful controlled. Samples are investigated by means of Fourier Transform Infrared (FTIR) spectroscopy and X-ray Diffraction (XRD) and the results are analyzed based on first-principles calculations. When C-S-H phases are transformed into C-S phases, only a few reflexes are detected on XRD, and the coherent scattering domains decrease with the increment of the temperature and time of exposure. This behavior is explained by the Ca/Si changes, which are identified by changes in the FTIR spectra. A thermodynamic analysis is performed with the help of first-principles calculations to underline the influence of the calcium-to-silicon (Ca/Si) ratio in the process of dehydroxylation. To increase the Ca/Si ratio water is partially substituted by methanol at the synthesis. This is observed in the FTIR spectra and is confirmed by lower temperatures of dehydroxylation. The catalytic nature of calcium towards the dehydroxylation is confirmed. The core of this work lies in the preparation of a model, which perfection makes possible to model reactivity, stability and mechanical properties using first-principles calculations, and is the starting point for the synthesis of many others.