PDF(Pubmed)
Abstract：
The structural change in Pt networks composed of multiple chain connections among grains was observed in air at 1 atm using atomic-resolution environmental cell scanning transmission electron microscopy. An aberration-corrected incident electron probe with a wide convergence angle made it possible to increase the depth resolution that contributes to enhancing the signal-to-noise ratio of Pt network samples in air in an environmental cell, resulting in the achievement of atomic-resolution imaging. The exposure of the Pt networks to gas molecules under Brownian motion, stimulated by electron beams in the air, increases the collision probability between gas molecules and Pt networks, and the Pt networks are more intensely stressed from all directions than in a situation without electron irradiation. By increasing the electron beam dose rate, the structural change of the Pt networks became significant. Dynamic observation on an atomic scale suggested that the structural change of the networks was not attributed to the surface atomic-diffusion-induced step motion but mainly caused by the movement and deformation of unstable grains and grain boundaries. The oxidized surface layers may be one of the factors hindering the surface atomic step motion, mitigating the change in the size of the grains and grain boundaries.
摘要：
使用原子分辨率环境细胞扫描透射电子显微镜在1atm的空气中观察到由晶粒之间的多个链连接组成的Pt网络的结构变化。具有宽会聚角的像差校正入射电子探针可以提高深度分辨率，从而有助于增强环境电池中空气中Pt网络样品的信噪比，从而实现了原子分辨率成像。Pt网络在布朗运动下暴露于气体分子，受到空气中电子束的刺激，增加气体分子和Pt网络之间的碰撞概率，与没有电子辐照的情况相比，Pt网络从各个方向受到的应力更大。通过增加电子束剂量率，Pt网络的结构变化变得显著。在原子尺度上的动态观察表明，网络的结构变化不是归因于表面原子扩散引起的阶跃运动，而是主要由不稳定晶粒和晶界的运动和变形引起的。氧化的表面层可能是阻碍表面原子步进运动的因素之一，减轻晶粒和晶界尺寸的变化。
