Structure and Dynamics in Boron-Containing Oxide Glasses and Liquids: High-Resolution and High-Temperature Nuclear Magnetic Resonance Studies

9626735 Stebbins 拟议的研究将在环境温度下使用核磁共振（NMR）光谱来确定不同的假想温度对玻璃结构的影响，这将限制温度对玻璃化转变附近的液体结构的影响。 原位，高分辨率，高温核磁共振硼，氧，钠，铝和硅核素将用于确定温度对平均配位环境的影响。将评估所观察到的结构变化对熵、焓、活性、摩尔体积和其他性质的影响 使用简单的热力学模型。 在 在较低的温度但仍在液体范围内，静态和魔角旋转NMR将用于观察结构物种之间的交换并测量它们的交换速率。 自旋-晶格弛豫时间将被测量以获得更宽温度范围内的动力学信息。这些分子尺度动力学的结果将进行比较，从现有的数据粘度剪切松弛时间，电导率和扩散率的数据。 将制定和测试连接微观和宏观的模型。 硅酸盐和硼硅酸盐玻璃及其相应的高温液体在工业和社会中具有广泛的重要性。 为了制定准确的预测模型的玻璃和玻璃熔体的性质，其原子尺度的结构和动力学的基础数据是必需的。 这里提出的工作将扩展我们小组的广泛研究简单的硅酸盐玻璃和液体硼酸盐，硼硅酸盐和硼铝酸盐系统，以解决基本的，但了解甚少的问题，这些技术上更相关的材料。 该项目的重点是使用核磁共振（NMR）光谱来获得定量结构 和动力学信息在环境和高温下，并解释和模拟现有的宏观热力学和传输属性数据，根据这些新的发现。 ***

9626735 Stebbins The proposed studies will use nuclear magnetic resonance (NMR) spectroscopy at ambient temperature to determine the effects of varying fictive temperature on glass structure, which will constrain temperature effects on liquid structure in the vicinity of the glass transition. In situ, high resolution, high temperature NMR on boron, oxygen, sodium, aluminum, and silicon nuclides will be used to determine temperature effects on average coordination environment. The effects of observed structural changes on entropy, enthalpy, activities, molar volumes, and other properties will be assessed using simple thermodynamic models. At lower temperatures but still in the liquid range, static and magic angle spinning NMR will be used to observe exchange among structural species and measure their exchange rates. Spin- lattice relaxation times will be measured to gain dynamical information over wider ranges in temperature. These results for molecular-scale dynamics will be compared to shear relaxation times derived from existing data on viscosity, and to data on electrical conductivity and diffusivity. Models linking the microscopic and macroscopic will be formulated and tested. %%% Silicate and borosilicate glasses, and their corresponding high temperature liquids, are of wide-ranging importance in industry and society. In order to formulate accurate predictive models for the properties of glasses and glass melts, fundamental data on their atomic-scale structure and dynamics are required. The work proposed here will extend our group's extensive studies of simple silicate glasses and liquids to borate, borosilicate, and boroaluminate-systems in order to address basic, but poorly understood questions about these technologically more relevant materials. The focus of this project is to use nuclear magnetic resonance (NMR) spectroscopy to acquire quantitative structural and dynamical information at ambient and high temperature, and to interpret and model existing macroscopic thermodynamic and transport property data in light of these new findings. ***