随着原位透射电子显微技术的不断发展与成熟,在近使役环境中对材料进行高空间与高时间分辨率下的研究得以广泛开展.而环境透射电镜(Environmental transmission electron microscope,E-TEM)与材料真实服役环境的一个重要区别在于所引入的环境气氛和样品材料本身都不可避免地受到电子束辐照的影响,因此多数研究都聚焦在如何降低或消除电子束辐照对研究结果的负面干扰.但实际上E-TEM中高能电子束可以起到较强的"催化"作用,从而激发出一些原本只有在苛刻条件下才能出现的现象或反应,助力材料改性、新材料合成及相应的微观反应机理的原位研究.本文以近几年作者所在研究团队及合作者利用E-TEM中电子束活化C02和H2气体分子在提升活泼金属耐蚀性、稳定性、辅助陶瓷的室温焊接及样品表面原位清洁等方面的具体应用为例,对电子束促进气固反应、改性材料表面及相关机理进行了介绍,并结合相关实验研究提出了固体表面吸附对电子束诱导气体活化过程的关键作用,更新了之前人们对电子束是通过提高游离态气体反应活性影响气-固间相互作用的认知.
Mechanism and applications of the electron-beam-assisted gas activation in surface modification of materials
With the continuous development of in-situ transmission electron microscopy technology,material behaviors under high spatial and high temporal resolution in near-operational environments have been widely studied by environmental transmission electron microscope(E-TEM).However,E-TEM is significantly different from the real environment where materials work.Both the introduced environmental atmosphere and the sample materials itself are inevitably affected by the electron beam irradiation in an E-TEM.Recently,the elimination of the negative effects of electron beam irradiation has been intensively investigated.However,the high-energy electron beam can trigger some novel catalytic reactions under extreme conditions inside of an E-TEM,which contributes to new material synthesis,modification,and understanding of reaction mechanisms.Here,we show some representative applications of electron beam-activated CO2 and H2 gas molecules in improving the corrosion resistance and stability of active metals,nano-welding of ceramic materials at an ambient temperature,as well as the in-situ cleaning of TEM samples.These applications validate that electron beam can significantly stimulate the gas-solid reaction.Based on these experimental data,we propose that the adsorption of gas on the solid surface plays a crucial role in the electron beam-induced activation of gas molecules,updating the previous understanding that electron beams affect a gas-solid interaction by increasing the reactivity of free gases.
electron beamactivation of gasE-TEMsurface modification
万方数据
维普
