Liquid cell electron microscopy has been proven to provide high spatial and temporal resolution for studying liquid layers and the solid-liquid interface at the micro and nano scale. The in situ environment allows for spatial and spectral characterization and quantification of the dynamics and kinetics involved with structural and chemical changes of nanostructures, which has seen application is fields of materials science, electrochemistry, corrosion, biomaterials, and nanophysics. The rapid growth of in situ liquid cell electron microscopy has motivated the fabrication of a custom liquid cell for improved control over the experimental conditions, including cell dimensions and materials. In this work, the process flow and micro-fabrication of a custom liquid cell system are proposed and executed, with proof of operation through the in situ imaging of suspended gold nanoparticles and electrochemical characterization. The in situ TEM system is improved upon by forming 1μm diameter holes through the viewing membranes, removing the background noise contribution from imaging electrons through the windows. This allows for high resolution liquid cell imaging. This improved system is used to study the oxidative etching conditions for palladium nanocrystals, which are commonly used as catalysis for hydrogen fuel cells. The dendritic etching is studied through native etching under exposure to hydrochloric acid without the presence of oxidizing species, followed by the radiolytic generation of oxidizing radicals via the microscope electron beam, and finally by the application of electrical biasing. / Thesis / Master of Applied Science (MASc) / Characterization of nanomaterials has been available for several decades and has aided in the improvement of material design, such as steel strength and corrosion resistance, electrical systems such as those involved in computers and smartphones, and biological sensing and detection. Observation of dynamic process which occur at the interface between solid and liquid phases, or purely within liquid layers, has always been a challenging topic due to the difficulty of finding a stable environment for both solids and liquids to exist at the nano scale within a measurement device. In situ liquid cell electron microscopy offers the ability to image this interface with real-time data acquisition for recording of dynamics and kinetics at the nano scale. Previous work has shown the liquid cell to provide high spatial and temporal resolution of systems in an environment which mimics their native operating conditions.
This thesis addresses current developments for in situ systems and works to develop a custom liquid cell to further the applications of the liquid cell and provide improved control over experimental conditions. The work then aims to improve on current technology by increasing the spatial resolution obtainable. Finally, the technique is applied to study the structural changes of nanocrystals under various etching conditions as a demonstration of its’ capabilities.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/23855 |
| Date | January 2019 |
| Creators | Daigle, Eric |
| Contributors | Botton, Gianluigi, Soleymani, Leyla, Materials Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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