In Situ High Resolution and Environmental Electron Microscopy Studies of Material Reactions.
In Situ High Resolution and Environmental Electron Microscopy Studies of Material Reactions.
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材料反应的原位高分辨率和环境电子显微镜研究。
DOI：
10.1017/s1431927618015775
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Ai,LK
中科院分区：
文献类型：
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作者：
Robert,S;Yunzhi,L;Sang,ChulL;Ai,LK
自20世纪80年代以来，原位透射电子显微镜（TEM）的应用和广度稳步增长[1]。当时，描述了进行有意义的实验的程序（例如[2]），但认为需要高压TEM和厚样品来再现体行为。然而，在一系列的研究中，我们确定这不一定是这种情况，即使是高分辨率的TEM记录也可以在真实的时间内原位进行，并且可以推断出与界面处材料反应相关的原子行为（例如[3]，[4]）。此外，随着薄膜和纳米技术的出现，对薄和纳米尺度材料的研究成为必要（例如[5]）。近年来，在受控环境（如气体和液体）中的原位透射电镜（如[1]，[6]）的应用又有了新的发展。本文利用原位高分辨率透射电镜研究材料反应。我们工作的一个首要主题是确保原位研究真正代表物质系统的真实的行为，我们已经提出了一些指导方针来确保这一点。[3，7]这些包括将微观结构变化与常规加工材料中的微观结构变化进行比较，例如在整体炉退火中，并测量反应动力学，从Arkenius型图中获得相关活化能。此外，我们还将我们的方法扩展到环境材料-气体反应，如碳纳米管（CNT）氧化[8]，硫化钼催化剂的氢气反应等。[9]（如图1）。成像电子束的影响对于气体反应更重要，因为它使反应气体物质电离，并且有必要开发协议以考虑到这一点。[10[11]下面将介绍我们为此采取的程序。在某些情况下，电离气体条件可以类似于在真实的实验环境中遇到的那些，如ETEM中的氧气环境中场发射CNT的耗散所示[12]。
There has been a steady growth in the applications and breadth of in situ transmission electron microscopy (TEM) since the 1980’s [1]. At that time, the procedures to carry out meaningful experiments were described (eg [2]) but it was thought that high voltage TEM and thick specimens were required to reproduce bulk behavior. However, in a series of studies, we established that this was not necessarily the case and that even high resolution TEM recordings could be made in real time, in situ and that the atomic behavior associated with materials reactions at interfaces could be deduced (eg [3],[4]). Moreover, with the advent of thin film and nanotechnology, the investigation of thin and nano-scale materials became a necessity (eg [5]). In recent years, there has been an additional proliferation, most notably from in situ TEM in controlled environments such as in gases and liquids (eg [1],[6]).This paper draws on the application of in situ high resolution TEM to investigate material reactions. An overarching theme of our work has been to ensure that the in situ studies are truly representative of the real behavior of the material system, and we have advanced a number of guidelines to ensure this.[3, 7] These include comparing the microstructural changes with those in conventionally processed materials, such as in bulk furnace annealing, and to measure the reaction kinetics yielding the relevant activation energy from an Arrhenius-type plot. In addition, we have also expanded our approach to environmental material-gas reactions such as carbon nanotube (CNT) oxidation [8], hydrogen reactions with molybdenum sulphide catalysts, etc.[9](eg Fig. 1). The influence of the imaging electron beam is more important for the gaseous reactions, as it ionizes the reacting gas species, and it is necessary to develop protocols to take this into account.[10, 11] The procedures we have adopted to do this will be described. In some circumstances, the ionized gas conditions can be similar to those encountered in real experimental circumstances, as shown for the dissipation of field-emitting CNT’s in an oxygen environment in the ETEM [12].