Compositional and Temperature Controls on Structural Order and Properties of Technological Oxide Glasses: NMR Studies and Thermodynamic Analyses

该项目的总体目标是更好地了解和预测成分和温度对氧化物玻璃和玻璃形成液，特别是那些含有大量氧化硼的玻璃的物理化学性质的影响。这种材料在技术上有广泛的用途，也是复杂的、部分无序的网络系统的有趣例子。主要的实验方法将是使用固态核磁共振(核磁共振)来定量确定短程到中程结构。将采用先进的方法来提高光谱分辨率，例如多量子11B、17O和27Al核磁共振以及使用超高场光谱仪(例如14.1和18.8特斯拉)。将根据需要合成晶体模型化合物，以帮助将局部原子结构与实验观测结果相关联，并测试玻璃光谱的量化。温度对前体液体结构的影响将通过研究玻璃样品以大范围的速度冷却，并由专门开发的快速冷却装置来促进。将开发基于结构的热力学模型，以便将光谱结果与构型熵、自由能和热膨胀性等关键性质联系起来。还将探索其他氧化物玻璃系统，如氟氧化物、氯氧化合物、磷酸铝和锗硅酸盐。氧化物玻璃用于许多关键技术，从相对普通的(如玻璃纤维)到高科技(如平板计算机显示器和光学数据处理)。这些玻璃中的许多都含有氧化硼，以帮助调整它们的性能以适应应用。这项技术的改进仍然通常是通过昂贵的反复试验的方法进行的。核磁共振(核磁共振)是少数几种可以定量确定这些复杂但至关重要的材料的原子级结构的方法之一，这反过来对于建立准确的预测模型至关重要，这些模型如何利用组成和温度的变化来优化它们的性能和发明新的应用。

The overall goal of this project is to better understand and predict the effects of composition and temperature on the physical and chemical properties of oxide glasses and glass-forming liquids, especially those containing major amounts of boron oxide. Such materials have widespread use in technology and are also fascinating examples of complex, partially disordered network systems. The primary experimental approach will be to use solid-state Nuclear Magnetic Resonance (NMR) to quantitatively determine the short- to intermediate-range structure. Advanced methods to enhance spectroscopic resolution, such as multiple quantum 11B, 17O and 27Al NMR and the use of the very high field spectrometers (e.g. 14.1 and 18.8 Tesla), will be applied. Crystalline model compounds will be synthesized as needed to help correlate local atomic structure with experimental observables, and to test the quantitation of spectra of glasses. Temperature effects on the structure of precursor liquids will be explored by studying samples of glass cooled at a wide range of rates, facilitated by a specially developed rapid quench apparatus. Structure-based thermodynamic models will be developed in order to link spectroscopic results to critical properties such as configurational entropy, free energy, and thermal expansivity. Other oxide glass systems will be explored as well, such as oxyfluorides, oxychlorides, aluminophosphates, and germanosilicates.Oxide glasses are used in many critical technologies, from the relatively mundane (e.g. fiber glass) to the high-tech (e.g. flat screen computer displays and optical data processing). Many of these glasses contain boron oxide to help tailor their properties to the application. Improvements in this technology are still often made by expensive, trial-and-error methods. Nuclear Magnetic Resonance (NMR) is one of the few available methods that can quantitatively determine the atomic-scale structure of these complex but vital materials, which in turn is essential to formulating accurate, predictive models of how variations in composition and temperature can be used to optimize their properties and invent new applications.