Transmission Electron Microscopy at Atmospheric Pressure
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The ability to monitor dynamic processes in-situ is crucial for understanding structure-property relationships in nano-engineered materials. In the past decade, the majority of atomic-scale electron microscopy studies involving gas-solid interactions were conducted in an environmental transmission electron microscope (ETEM), where the gas pressure is typically limited to no more than 1/100 of at atmosphere. Recently, it has become possible to overcome this limitation through the use of a MEMSbased, electron-transparent closed cell with sample heating stage. In this talk, we illustrate the power of this device as applied to our study of two important catalyst systems: (1) the structural evolution of supported Pd@CeO2 and (2) the ordering and Pt surface enrichment in supported Pt3Co. For this work, we used the Protochips Atmosphere system [1], in which the sample is situated between two SiN windows, each of 30-50 nm in thickness, with a 5 um gap in between, in combination with a JEOL 3100R05 double aberration corrected transmission electron microscope (TEM) operating at 300kV in scanning mode.
[1] P. Fornasiero,et al. Exceptional Activity for Methane Combustion over Modular Pd@CeO2 Subunits on Functionalized Al2O3 , 2012, Science.
[2] D. Nackashi,et al. Novel MEMS-Based Gas-Cell/Heating Specimen Holder Provides Advanced Imaging Capabilities for In Situ Reaction Studies , 2012, Microscopy and Microanalysis.