Structural and Microstructural Studies of Ti/Zr- and Al-Based Quasicrystals, Approximants and Metallic Glasses

这项资助的主要目的是更好地理解局部结构和长程扩散对玻璃形成和结晶的作用。代表性玻璃将从四个技术上重要的家族（Al基、Ti/Zr基、Fe基和Mg基）中选择。 非晶结构将用广角X射线散射、3D原子探针、EXAFS和可变相干（或波动）暗场透射电子显微镜（TEM）进行研究。将通过对测量的X射线结构因子进行反向蒙特卡罗分析来构建合理的非晶结构。长程扩散对成核和生长的影响将通过能量过滤TEM、原子探针和小角散射来研究，动力学将通过差示扫描量热法和TEM测量来确定。这些数据将适合一个新的模型扩散影响成核在华盛顿大学开发。该资助的第二个目标是继续对Ti/Zr/Hf/Mg基准晶和玻璃进行氢化研究，这些准晶和玻璃具有技术相关特征，例如高储存重量比。从玻璃中的协调测量和建模中获得的见解将澄清玻璃结晶过程中纳米结构形成的机制，这将导致对纳米结构生产的更好控制。除了产生新的基本和技术利益的信息，这项研究具有重要的教育意义。研究生和本科生都将接受材料科学和凝聚态物理学理论和实验方法的培训。将在当地中学介绍这一研究和相关研究，为潜在的科学职业提供信息，并为研究生和本科生提供帮助科学教育的机会。

The primary purpose of this grant is to develop a better understanding of the role of local structure and long-range diffusion on glass formation and crystallization. Representative glasses will be chosen from four technologically important families (Al-based, Ti/Zr-based, Fe-based and Mg-based). Amorphous structures will be studied with wide-angle x-ray scattering, 3D atom probe, EXAFS, and variable coherence (or fluctuation) dark-field transmission electron microscopy (TEM). Plausible amorphous structures will be constructed from a Reverse Monte Carlo analysis of the measured x-ray structure factor. The influence of long-range diffusion on nucleation and growth will be studied with energy filtered TEM, atom probe and small angle scattering, and the kinetics will be determined from differential scanning calorimetry and TEM measurements. These data will be fit to a new model for diffusion-influenced nucleation developed at Washington University. A second goal of the grant is to continue hydrogenation studies of Ti/Zr/Hf/Mg-based quasicrystals and glasses that have technologically relevant features, such as a high storage to weight ratio.%%%The insight gained from the coordinated measurements and modeling in glasses will clarify the mechanisms responsible for nanostructure formation during glass crystallization that will lead to improved control of nanostructure production. In addition to producing new information of basic and technological interest, this research has a significant educational importance. Both graduate and undergraduate students will receive training in theoretical and experimental methods in materials science and condensed-matter physics. Presentations of this and related research will be given in local secondary schools, providing information for potential scientific careers and allowing opportunities for graduate and undergraduate students to help with science education.***