Nuclear magnetic resonance studies of disordered materials

材料科学的进步依赖于可靠的结构表征方法。许多种类的固体材料的无序性质使得人们很难对原子级结构有一个详细的了解。核磁共振理论和仪器的最新发展极大地扩展了可用这种技术研究的元素的范围。事实上，核磁共振正在迅速成为一种常规方法，用于表征各种先进材料的结构，包括玻璃、陶瓷、水泥、聚合物和多孔材料。这项提议的广泛目标是建立在核磁共振新开发的技术基础上，旨在识别无序固体中的更远距离结构。这些努力的核心是利用两个原子核之间的相互作用作为距离的直接探测器的方法。与化学位移相比，这种方法提供了更直接的中程有序信息，化学位移只与邻近原子间接相关。没有其他实验技术能够像核磁共振那样直接绘制原子连接性图。这项工作将导致原子级组织和块体性质之间更详细的关联，从而为更全面地描述玻璃结构打开大门，并在结构和功能之间提供关键联系。尽管寻求普遍适用的技术，但最初的应用将针对不同复杂性的硼酸盐玻璃和顺磁有机金属材料，这两个系统都是经过充分研究但尚未完全理解的系统，对商业生产和新材料的开发具有深远影响。除了技术开发和探索之外，这些研究还将对玻璃态的性质产生独特和基本的见解，为合理设计高性能玻璃提供必不可少的结构信息，应用范围从光学透镜到核废料固定化。

Advancement in materials science depends on reliable methods of structural characterization. The disordered nature of many classes of solid materials makes it difficult to obtain a detailed understanding of the atomic-level structure. Recent developments in nuclear magnetic resonance (NMR) theory and instrumentation have greatly expanded the range of elements that can be studied by this technique. Indeed, NMR is rapidly becoming a routine approach for the structural characterization of a wide variety of advanced materials, including glasses, ceramics, cements, polymers and porous materials. The broad objective of this proposal is to build on newly developed techniques in NMR designed to identify longer-range structure in disordered solids. Central to these efforts are methods which exploit interactions between two nuclei as a direct probe of distance. This approach provides more direct information on medium-range order than chemical shifts, which are only indirectly related to neighbouring atoms. No other experimental technique is able to map atomic connectivities as directly as NMR. This work will lead to more detailed correlations between atomic-level organization and bulk properties, thus opening the door to a more comprehensive description of glass structure and providing a critical link between structure and function.  Although generally applicable techniques are sought, initial applications will target borate-based glasses of varying complexity, and paramagnetic organometallic materials, both of which represent well-studied but incompletely understood systems with far-reaching implications in commercial production and the development of new materials. In addition to technique development and exploration, these studies will yield unique and fundamental insight into the nature of the glassy state, providing structural information essential to the rational design of high-performance glasses for applications ranging from optical lenses to nuclear waste immobilization.