Vogelsberger W, Seidel A, Fuchs R
Institute of Physical Chemistry, Faculty of Chemistry and Earth Science, Friedrich-Schiller-University Jena, Lessingstrabetae 10, Jena, D-07743, Germany
J Colloid Interface Sci. 2000 Oct 15;230(2):268-271. doi: 10.1006/jcis.2000.7095.
The system tetraethoxysilane(TEOS)-water-ethanol has been studied by rheological measurements. Different molar ratios of TEOS : water (1 : 4, 1 : 10, and 1 : 20) are studied at different temperatures (30, 40, and 50 degrees C). The dynamic viscosity (rotating mode) at a constant shear rate (100 s(-1)) and the elastic and viscous moduli (oscillating mode) at a constant frequency (1 Hz) are determined. The viscosity-time curves are evaluated by application of a nucleation and particle growth model. Good agreement between experiments and theory is observed. The model allows the determination of the complex rate constant of silica precipitation. The temperature-dependent measurements gave the possibility to determine the apparent energy of activation by common methods. The results are in agreement with data from the literature. The gel time defined as intersection point of elastic and plastic moduli and its dependence on temperature are evaluated by the Smoluchowski model. The energy of activation for the coagulation was determined and found to be in the correct order of magnitude. Copyright 2000 Academic Press.
通过流变学测量研究了四乙氧基硅烷（TEOS）-水-乙醇体系。在不同温度（30、40和50摄氏度）下研究了TEOS与水的不同摩尔比（1:4、1:10和1:20）。测定了在恒定剪切速率（100 s⁻¹）下的动态粘度（旋转模式）以及在恒定频率（1 Hz）下的弹性和粘性模量（振荡模式）。通过应用成核和颗粒生长模型评估粘度-时间曲线。观察到实验与理论之间有良好的一致性。该模型能够确定二氧化硅沉淀的复合速率常数。与温度相关的测量使得通过常用方法确定表观活化能成为可能。结果与文献数据一致。通过Smoluchowski模型评估了定义为弹性和塑性模量交点的凝胶时间及其对温度的依赖性。确定了凝聚的活化能，发现其量级正确。版权所有2000年学术出版社。
