The Setting Behaviour of α‐ and β‐CaSO4 · 0,5 H2O as a Function of Crystal Structure and Morphology
The Setting Behaviour of α‐ and β‐CaSO4 · 0,5 H2O as a Function of Crystal Structure and Morphology
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DOI：
10.1002/1521-4079(200210)37:10
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发表时间：
2002-10
影响因子：
1.5
通讯作者：
S. Follner;A. Wolter;A. Preußer;S. Indris;C. Silber;H. Follner
中科院分区：
文献类型：
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作者：
S. Follner;A. Wolter;A. Preußer;S. Indris;C. Silber;H. Follner
二水合硫酸钙(CaSO4.XH2O，0<；x≤0.8)具有蜂窝状通道结构。对称性要么是三角的，要么是略有偏离的。由于衍射数据不足和结构的高度假对称性，在这一点上不可能确定通道中水分子的具体排列。当用傅里叶变换方法计算半水合物(x=0.5)的生长形态时，只有在基本保持三角结构对称性的情况下，计算的晶体形态才与观察到的形态相对应。在石膏脱水过程中，或相反，在半水石膏的凝结过程中，观察到半水石膏在石膏上异质外延生长，或石膏在半水石膏上异质外延生长。半水石膏的(100)面和石膏的(010)面大部分是平行的。用衍射和光谱方法可以证明，α-和β-半水合物之间存在着结构上的差异，这种差异可能是不同凝结行为的原因。正是在这种背景下，在核磁共振实验中发现的氧离子的存在，特别是在β-半水合物中，是令人感兴趣的。质构研究表明，在硬化石膏中发现的石膏晶体的排列方式是由半水合物决定的。
Calcium sulphate subhydrates (CaSO 4 . x H 2 O, 0 < x ≤ 0.8) have a honeycomb-shaped channel structure. The symmetry is either trigonal or a slight deviation thereof. Due to insufficient diffraction data and the high pseudosymmetry of the structure, it is not possible at this point to determine with certainty the specific arrangement of the water molecules in the channels. When the Fourier transformation method is used to calculate the growth form of the hemihydrate (x = 0.5), the calculated crystal form corresponds to the observed form only when the trigonal structural symmetry is largely retained. During dehydration of gypsum or, conversely, during the setting process of hemihydrate, heteroepitaxial growths of hemihydrate are observed on gypsum, or gypsum is grown heteroepitaxially on hemihydrate. The (100) faces of the hemihydrate and (010) of gypsum for the most part run parallel. Using diffraction and spectroscopic methods, it can be shown that a structural difference exists between α- and β-hemihydrates, and that this difference probably accounts for the different setting behaviours. It is in this context that the presence of oxonium ions, particularly in β-hemihydrate, found in NMR experiments is of interest. Textural studies indicated that the arrangement of gypsum crystals found in hardened gypsum is determined by the hemihydrate.