The Growth Kinetics Study of Spinel Oxides Nanostructures using In-situ Transmission Electron Microscopy in Solution

• Main Authors: Liang, Wen-I, 梁文怡
• Other Authors: Chu, Ying-Hao
• Format: Others
• Language: en_US
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/15023510121213589066

博士 === 國立交通大學 === 材料科學與工程學系所 === 104 === The formation process and kinetics of nanostructures in solution have long been a myth with only theoretical and ex situ experimental supports in the past. Not until recently could we be able to directly monitor the materials nucleation and growth in solution with extraordinary temporal and spatial resolution by the revolution of in situ liquid cell TEM. As a relatively new technique with great potential, huge efforts have been put into the disclosure of fundamental growth kinetics in various systems. In this thesis, we first studied the oxide nanoparticles formation in a reductive environment under electron beam irradiation. Different from previous reports about noble metal nanoparticles formation, the growth of oxides were studied. We proposed that not only reduction of solvated electrons but electron beam heating effect is considerably important for the growth initiation. Additionally, we found that the reduction potential and the thermal decomposition temperature of loaded solution play a decisive role in the determination of final product. On top of the fundamental understanding about formation pathways in first part, in the second part of this thesis, we addressed the growth kinetics of core-shell nanostructure with complex composition. The formation and structural evolution of PtFe3- Fe2O3 core-shell nanostructure was captured in real time with atomic resolution. The results suggest that the sequential formation of metallic core and oxide sheath was associated with the reduction potential difference and the Pt catalytic effect. In the last part, the complex pattern development was traced in real time. Using the material systems similar to first part, the study in the last part nails the entire development of dendritic nanostructures at nanoscale. The growth kinetics between non-splitting tip and splitting tip were analyzed. In addition, we quantified the characteristic wavelengths to visualize an oscillatory behavior during nanostructure development. Overall, this thesis covers mostly the development process of various functional oxide nanostructures in real time using liquid cell TEM technique, enriching the fundamental understanding of material growth kinetics critical to nanomaterials engineering.