Glass Surfaces: Experimental Study and Computer Simulation

玻璃表面：实验研究和计算机模拟

• 批准号: 9803884
• 负责人: Carlo Pantano
• 金额: $ 30.09万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-06-01 至 2002-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9803884&HistoricalAwards=false
• 关键词: Glass; Surfaces; Experimental; Study; Computer

9803884 Pantano The goal of this project is to gain a better understanding of the molecular structure of multicomponent silicate glass surfaces, and especially, the effect of modifier-ions upon the distribution and activity of surface adsorption sites. A coordinated study of multicomponent silicate glass surfaces is proposed in which computer simulation and experimental studies will be directed toward characterization and prediction of adsorption isotherms in terms of the atomic/molecular scale surface structure. The computer simulation of the atomic structure of the silicate-based glasses is based on a novel approach to the simulation of the vitreous silica surfaces. It is assumed that the surface of pure vitreous silica should be hydrophobic. To achieve this in a computer simulation, it is necessary to bring the structural relaxation time within the time limits of computer simulation. Whereas previous computer simulations of glass have focused on the ideal surface created by abrupt removal of periodic boundary conditions with some annealing, this study will focus more specifically on the annealing of surfaces in an effort to simulate lower energy melt surfaces. A novel experimental approach will be used for determining the isotherms and energies of adsorption on glass powders, glass fibers and gels. This approach is an extension of the comparison method in which the gas-adsorption isotherm of an adsorbent (with unknown adsorption characteristics) is plotted against the standard isotherm (of a reference material). The isotherms will be compared with computer simulated isotherms to obtain (i) detailed descriptions of the atomic structure of multicomponent glass surfaces, (ii) the local electric fields associated with modifiers, non-bridging oxygens or surface silanols, (iii) the spatial distributions of modifying cations on the surface and (iv) the mechanism of water (and other reactive specie) adsorption on these heterogeneous surfaces. Static-SIM S, FTIR and related spectroscopic techniques will be employed to further validate surface composition effects and irreversible chemisorption reactions. %%% The ability to accurately simulate the glass surface and physisorption isotherms using computer methods provides a powerful tool to predict the surface thermodynamic properties for new glass compositions, and/or to interpret the adsorption behavior of existing glasses and glass products. The surface and surface chemistry of silica and silicate glasses are fundamental to many of their properties including strength, corrosion, polymer adhesion, bioreactivity, and optical response. The project is being carried-out through the collaboration of scientists simulating and studying the theory of simple gas adsorption on model amorphous surfaces with those whose focus is characterization and processing of more complex glass surfaces. ***

9803884潘塔诺这个项目的目标是更好地了解多元硅酸盐玻璃表面的分子结构，特别是改性剂离子对表面吸附位置分布和活性的影响。提出了一种多组分硅酸盐玻璃表面的协同研究，其中计算机模拟和实验研究将针对原子/分子尺度的表面结构来表征和预测吸附等温线。硅酸盐玻璃原子结构的计算机模拟是基于一种模拟玻璃二氧化硅表面的新方法。我们假定纯玻璃二氧化硅的表面应该是疏水的。为了在计算机模拟中实现这一点，有必要将结构松弛时间限制在计算机模拟的时间范围内。以前对玻璃的计算机模拟主要集中在通过对周期性边界条件的突然去除和一定程度的退火而产生的理想表面，而这项研究将更具体地集中于表面的退火，以努力模拟较低能量的熔体表面。一种新的实验方法将被用来测定玻璃粉、玻璃纤维和凝胶的吸附等温线和吸附能。这种方法是比较法的推广，在比较法中，吸附剂(吸附特性未知)的气体吸附等温线与(标准物质)的标准等温线相比较。这些等温线将与计算机模拟的等温线进行比较，以获得(I)多组分玻璃表面原子结构的详细描述，(Ii)与改性剂、非桥氧或表面硅烷醇相关的局部电场，(Iii)改性阳离子在表面上的空间分布，以及(Iv)水(和其他活性物种)在这些非均质表面上的吸附机理。利用静态SIM S、傅里叶变换红外光谱和相关光谱技术进一步验证表面组成效应和不可逆化学吸附反应。使用计算机方法准确模拟玻璃表面和物理吸附等温线的能力为预测新玻璃成分的表面热力学性质和/或解释现有玻璃和玻璃产品的吸附行为提供了强大的工具。二氧化硅和硅酸盐玻璃的表面和表面化学是其许多性能的基础，包括强度、腐蚀性、聚合物粘附性、生物反应性和光学响应。该项目是通过科学家的合作来进行的，他们模拟和研究了简单气体在模型非晶态表面上的吸附理论，重点是更复杂的玻璃表面的表征和处理。***