Coupled Nucleation, Nanostructure Formation and Hydrogen Storage in Metallic Glasses and Quasicrystals

技术：成核过程比通常认为的要复杂，必须适当考虑到远程扩散和界面附着的随机通量之间的耦合。最近的研究，包括PI的研究表明，化学、结构和磁性有序的有序参数波动也可以与成核相关的有序参数波动耦合。除了他们的基本兴趣之外，这些结果表明，通过改进对这种成核行为的理解，可以增强纳米结构的细化。为了更好地了解成核耦合过程及其改善微观结构的潜力，本项目将通过宽角和小角x射线衍射确定选定的Ti/ zr基、Co/ fe基和mg基金属玻璃的局部原子结构；高分辨率、能量滤波和波动透射电镜；EXAFS;原子探针测量。这些数据将与玻璃形成和结晶动力学相关，由差示扫描量热法和电阻率测量以及基于时间相关成核的TEM研究确定。研究还将继续探讨扩散对成核行为的影响。为了评估其作为储氢材料的潜在用途，将确定体积和纳米结构i（TiZrNi）的高压平台的循环特性和起源。非技术：这些研究的结果将具有广泛的基础和技术兴趣，包括氢储存，对相变的更深入理解和对纳米结构生产的改进控制。Ti/Zr准晶有助于促进向氢基运输系统的过渡。该研究具有重要的教育意义，为研究生和本科生提供培训，并为当地高中生提供材料科学理论和实验方法的经验。PI和他的研究生将向学生和老师介绍研究成果，并直接与学生一起工作，使他们了解科学事业的可能性。

TECHNICAL: Nucleation processes are more complex than often assumed, and proper account must be taken of the coupling between the stochastic fluxes of long-range diffusion and interfacial attachment. Recent studies, including those by PI indicate that order-parameter fluctuations such as those that underlie chemical, structural, and magnetic ordering can also couple with the order parameter fluctuations associated with nucleation. In addition to their basic interest, these results demonstrate that enhanced nanostructural refinement is possible by an improved understanding of this nucleation behavior. To better understand coupled process in nucleation and their potential for improved microstructure refinement, this project will determine the local atomic structure of select Ti/Zr-based, Co/Fe-based and Mg-based metallic glasses by wide and small angle x-ray diffraction; high resolution, energy filtered and fluctuation transmission electron microscopy; EXAFS; and atom probe measurements. This data will be correlated with glass formation and the crystallization kinetics, determined by differential scanning calorimetry and electrical resistivity measurements and by TEM based studies of time-dependent nucleation. Research will also continue to probe the influence of diffusion on nucleation behavior. The cycling characteristics and origin of the high-pressure plateau will be determined for bulk and nanostructured i(TiZrNi) to evaluate its potential usefulness as a hydrogen storage material. NON-TECHNICAL: The results from these studies will be of broad basic and technological interest including hydrogen storage, a deeper understanding of phase transitions and improved control over nanostructure production. The Ti/Zr quasicrystals could help facilitate the transition to a hydrogen-based transportation system. The research has a significant educational importance, providing training to graduate and undergraduate students, and experience to local high school students in the theoretical and experimental methods of materials science. PI and his graduate students will give presentations of research results to the students and teachers and work directly with the students to expose them to the possibilities for scientific careers.