Department of Materials Science and Engineering, University of North Texas, Denton 76203-5017, Texas, USA.
J Chem Phys. 2013 Jul 28;139(4):044507. doi: 10.1063/1.4816378.
Addition of alumina to sodium silicate glasses considerably improves the mechanical properties and chemical durability and changes other properties such as ionic conductivity and melt viscosity. As a result, aluminosilicate glasses find wide industrial and technological applications including the recent Corning(®) Gorilla(®) Glass. In this paper, the structures of sodium aluminosilicate glasses with a wide range of Al∕Na ratios (from 1.5 to 0.6) have been studied using classical molecular dynamics simulations in a system containing around 3000 atoms, with the aim to understand the structural role of aluminum as a function of chemical composition in these glasses. The short- and medium-range structures such as aluminum coordination, bond angle distribution around cations, Q(n) distribution (n bridging oxygen per network forming tetrahedron), and ring size distribution have been systematically studied. In addition, the mechanical properties including bulk, shear, and Young's moduli have been calculated and compared with experimental data. It is found that aluminum ions are mainly four-fold coordinated in peralkaline compositions (Al∕Na < 1) and form an integral part of the rigid silicon-oxygen glass network. In peraluminous compositions (Al∕Na > 1), small amounts of five-fold coordinated aluminum ions are present while the concentration of six-fold coordinated aluminum is negligible. Oxygen triclusters are also found to be present in peraluminous compositions, and their concentration increases with increasing Al∕Na ratio. The calculated bulk, shear, and Young's moduli were found to increase with increasing Al∕Na ratio, in good agreement with experimental data.
氧化铝的加入极大地改善了钠硅酸盐玻璃的机械性能和化学耐久性，并改变了其他性质，如离子电导率和熔体粘度。因此，铝硅酸盐玻璃在包括最近的康宁（®）大猩猩（®）玻璃在内的广泛工业和技术应用中找到了广泛的应用。在本文中，使用包含约 3000 个原子的系统中的经典分子动力学模拟研究了具有广泛 Al∕Na 比（从 1.5 到 0.6）的钠铝硅酸盐玻璃的结构，目的是了解铝在这些玻璃中的化学组成下的结构作用。系统地研究了短程和中程结构，如铝配位、阳离子周围的键角分布、Q(n)分布（每个网络形成四面体的桥氧数）和环大小分布。此外，还计算并比较了包括体、剪切和杨氏模量在内的力学性能与实验数据。结果发现，在过碱性组成中（Al∕Na < 1），铝离子主要以四配位形式存在，并形成刚性硅氧玻璃网络的组成部分。在过铝性组成中（Al∕Na > 1），存在少量五配位的铝离子，而六配位的铝离子浓度可以忽略不计。还发现氧三簇存在于过铝性组成中，其浓度随 Al∕Na 比的增加而增加。计算得到的体、剪切和杨氏模量随 Al∕Na 比的增加而增加，与实验数据吻合良好。
