Atomic mobility in nanoglasses

纳米玻璃是一类相对较新的非晶材料，由两个具有不同原子排列的不同非晶区域组成，其特征尺寸为几纳米。已经发现，金属纳米玻璃的原子结构与通过从熔体淬火制备的众所周知的金属玻璃的原子结构明显不同。成分波动（偏析），自由体积的差异和增加中程秩序，但没有结晶，似乎是纳米玻璃和快速淬火的金属玻璃之间的主要结构差异。在这两个区域的结构差异导致急剧变化的机械和功能性能相比，快速淬火金属玻璃。扩散可以用作识别材料中的结构差异的工具，例如，沿沿着界面和在本体中的扩散通常是非常不同的。在目前的项目中，将在纳米玻璃和快速淬火的参考结构中研究原子迁移率，以确定纳米玻璃和传统制备的金属玻璃之间的巨大结构差异的更多细节。扩散过程的研究需要详细了解原子结构，因此，将对金属纳米玻璃进行结构表征，以确定纳米玻璃的微观结构和界面区域的原子结构。采用热蒸发和磁控溅射的惰性气体冷凝法制备了Fe90Sc10、Cu50Zr50和Pd80Si20三种材料体系的纳米玻璃样品。将使用XRD、SEM和TEM对标准样品进行表征，对于选定的样品，还将使用SAXS、EXAFS、径向分布函数和穆斯堡尔谱来表征不同非晶相的形态、微观结构和原子结构。在一个互补的研究方法中，卡尔斯鲁厄理工学院和明斯特大学的两个研究小组将研究三个选定的纳米玻璃系统和快速淬火参考样品中的自扩散、杂质扩散和互扩散。

Nanoglasses are a relatively new class of amorphous materials, consisting of two distinct amorphous regions with different atomic arrangements with characteristic dimensions of a few nanometer. It has been found that the atomic structure of metallic nanoglasses is distinctly different from that of the well-known metallic glasses prepared by quenching from the melt. Compositional fluctuations (segregation), free volume differences and increased medium range order, but without crystallization, seem to be the major structural differences between the nanoglasses and the rapidly quenched metallic glasses. The structural differences in the two regions result in drastic changes of the mechanical and the functional properties compared to rapidly quenched metallic glasses. Diffusion can be used as a tool to identify structural differences in materials, for example, diffusion along interfaces and in the bulk are typically very different. In the current project, atomic mobility will be studied in nanoglasses and in the rapidly quenched reference structure to identify more details of the drastic structural differences between nanoglasses and the conventionally prepared metallic glasses. Studies of diffusion processes require detailed knowledge of the atomic structure, and, consequently, structural characterization of the metallic nanoglasses will be performed to identify the microstructure of the nanoglasses and the atomic structure of the interfacial regions. Nanoglass samples in three materials systems, i.e. Fe90Sc10, Cu50Zr50 and Pd80Si20, will be prepared by inert gas condensation using thermal evaporation and magnetron sputtering. Standard sample characterization will be performed using XRD, SEM and TEM, and for selected samples also SAXS, EXAFS, radial distribution functions and Mössbauer spectroscopy to characterize the morphology, microstructure and atomic structure of the different amorphous phases. In a complementary research approach the two research groups at Karlsruhe Institute of Technology and at University Münster will study the self diffusion, the impurity diffusion and the interdiffusion in the three selected nanoglass systems and the rapidly quenched reference samples.