Liu Ting, Dou Xiangyu, Xu Yonghui, Chen Yongjun, Han Yongsheng
State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, 100190 Beijing, China.
State Key Laboratory of Marine Resource Utilization in South China Sea, Hainan University, 570228 Haikou, China.
Research (Wash D C). 2020 Feb 10;2020:4370817. doi: 10.34133/2020/4370817. eCollection 2020.
Rational synthesis of materials is a long-term challenging issue due to the poor understanding on the formation mechanism of material structure and the limited capability in controlling nanoscale crystallization. The emergent in situ electron microscope provides an insight to this issue. By employing an in situ scanning electron microscope, silver crystallization is investigated in real time, in which a reversible crystallization is observed. To disclose this reversible crystallization, the radicals generated by the irradiation of electron beam are calculated. It is found that the concentrations of radicals are spatiotemporally variable in the liquid cell due to the diffusion and reaction of radicals. The fluctuation of the reductive hydrated electrons and the oxidative hydroxyl radicals in the cell leads to the alternative dominance of the reduction and oxidation reactions. The reduction leads to the growth of silver crystals while the oxidation leads to their dissolution, which results in the reversible silver crystallization. A regulation of radical distribution by electron dose rates leads to the formation of diverse silver structures, confirming the dominant role of local chemical concentration in the structure evolution of materials.
由于对材料结构形成机制的理解不足以及控制纳米级结晶的能力有限，材料的合理合成是一个长期具有挑战性的问题。新兴的原位电子显微镜为这个问题提供了一个视角。通过使用原位扫描电子显微镜，实时研究了银的结晶过程，观察到了可逆结晶现象。为了揭示这种可逆结晶，计算了电子束辐照产生的自由基。结果发现，由于自由基的扩散和反应，自由基的浓度在液体池中随时间和空间变化。池中还原水合电子和氧化羟基自由基的波动导致还原反应和氧化反应交替占主导地位。还原导致银晶体生长，而氧化导致其溶解，从而导致可逆的银结晶。通过电子剂量率对自由基分布的调节导致形成多种银结构，证实了局部化学浓度在材料结构演变中的主导作用。
