Key Lab of Structures Dynamic Behavior and Control (Harbin Institute of Technology), Ministry of Education, 150090 Harbin, China.
Laboratory for the Chemistry of Construction Materials (LC), Department of Civil and Environmental Engineering, University of California, Los Angeles, California 90095, USA.
J Chem Phys. 2018 Jun 21;148(23):234504. doi: 10.1063/1.5027583.
The sol-gel method is an attractive technique to synthesize homogeneous silicate glasses with high purity while relying on a lower synthesis temperature than in the melt-quench method. However, the mechanism and kinetics of the condensation of the silicate network in aqueous solution remain unclear. Here, based on reactive molecular dynamics simulations (ReaxFF), we investigate the sol-gel condensation kinetics of a silica glass. The influence of the potential parametrization and system size is assessed. Our simulation methodology is found to offer good agreement with experiments. We show that the aqueous concentration of the Si(OH) precursors and the local degree of polymerization of the Si atoms play a crucial role in controlling the condensation activation energy. Based on our simulations, we demonstrate that the gelation reaction is driven by the existence of some local atomic stress that gets released upon condensation.
溶胶-凝胶法是一种很有吸引力的技术，可用于在比熔融淬火法更低的合成温度下合成高纯度的均匀硅酸盐玻璃。然而，水相溶液中硅酸盐网络缩合的机理和动力学仍不清楚。在这里，我们基于反应分子动力学模拟（ReaxFF）研究了二氧化硅玻璃的溶胶-凝胶缩合动力学。评估了势参数化和系统尺寸的影响。我们的模拟方法被发现与实验很好地吻合。我们表明，Si(OH)前体的水相浓度和 Si 原子的局部聚合度在控制缩合活化能方面起着至关重要的作用。基于我们的模拟，我们证明凝胶化反应是由一些局部原子应力的存在所驱动的，这些应力在缩合时得到释放。
