Liu Pan, Chen Qing, Ito Yoshikazu, Han Jiuhui, Chu Shufen, Wang Xiaodong, Reddy Kolan Madhav, Song Shuangxi, Hirata Akihiko, Chen Mingwei
Shanghai Key Laboratory of Advanced High-Temperature Materials and Precision Forming, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200030, China.
Nano Lett. 2020 Mar 11;20(3):1944-1951. doi: 10.1021/acs.nanolett.9b05216. Epub 2020 Feb 20.
Understanding the formation and evolution of bicontinuous nanoporous structure during dealloying has been one of the most challenging subjects of dealloying research. However, previous investigations either suffer from insufficient spatial resolution (e.g., X-ray tomography) or lack morphology visualization and mass information (e.g., scanning tunneling microscopy). In this work, we report the kinetics of the whole course of dealloying by utilizing liquid-cell aberration-corrected scanning transmission electron microscopy. With -contrast imaging analysis, the sub-nanoscale characterization reveals two new phenomena, an initial period of dealloying indicative of an initial length scale for bulk dealloying and a large volume shrinkage in a nanoscale alloy precursor. We explain the particle-size-dependent volume shrinkage with the formation of a dense shell and quantify the dependence with a simple geometric model. These insights into the mechanisms of dealloying will enable deliberate designs of nanoporous structures.
理解脱合金过程中双连续纳米多孔结构的形成与演化一直是脱合金研究中最具挑战性的课题之一。然而，以往的研究要么空间分辨率不足（如X射线断层扫描），要么缺乏形态可视化和质量信息（如扫描隧道显微镜）。在这项工作中，我们利用液池像差校正扫描透射电子显微镜报告了脱合金全过程的动力学。通过对比度成像分析，亚纳米级表征揭示了两个新现象：脱合金初期表明了整体脱合金的初始长度尺度，以及纳米级合金前驱体中的大体积收缩。我们用致密壳层的形成解释了粒径依赖性体积收缩，并通过一个简单的几何模型对这种依赖性进行了量化。这些对脱合金机制的见解将有助于对纳米多孔结构进行精心设计。
