CCST Seminar: Patricia Kooyman
Patricia obtained her MSc from Leiden University (The Netherlands), studying the selective reduction of nitrosobenzene over mixed manganese oxides. She obtained her PhD from Delft University of Technology (The Netherlands) studying TS-1 zeolite synthesis and catalytic applications. Following a post-doc at Shell research centre (Amsterdam, The Netherlands), she learned all about TEM during a long post-doc period at the NCHREM (Delft, The Netherlands). Subsequently she was appointed assistant professor at the Chemical Engineering department (catalysis engineering group) at Delft University of Technology (The Netherlands). She came to South Africa in 2015 as SARChI Chair Nanomaterials for Catalysis. She has always enjoyed travelling and has held many short-term visiting scientist positions throughout her career. Her research focusses on heterogeneous catalysis, especially catalyst characterisation. She is an expert in high resolution transmission electron microscopy and is one of the pioneers in gas-phase in situ TEM.
"Bridging the Pressure Gap in Transmission Electron Microscopy"
TEM is traditionally a high vacuum (10-6 Torr) technique. However, many materials have a different (surface) structure in vacuum as opposed to gaseous environment. The specific gas present can even influence the structure of a material. This means that traditional TEM images are mostly obtained of materials that are NOT in the state in which they are used in practice. One important area of application is catalysis research. The development of differentially pumped ETEM was a significant step in the direction of real in situ TEM, allowing gas pressures of up to 50 mbar and heating up to about 1000°C. We have developed a micro-electro-mechanical system (MEMS) nanoreactor to bridge the pressure gap. It confines a thin layer of gas (several microns) in a windowed cell, thus retaining atomic resolution at pressures exceeding 1 bar by limiting the path length of gas the electron have to traverse. The catalyst under study (or its precursor) can be loaded into the nanoractor prior to the experiments. Small electron-transparent windows provide both good transmission of the electron beam and stability against the pressure difference. Heating is possible up to about 600°C. This nanoreactor system has now been expanded by adding the possibility of studying gas compositions using mass spectrometry. This means the gas composition can be monitored while simultaneously imaging dynamic changes in eg catalyst metal nanoparticles. We have used this system to study the Kirkendall effect during oxidation of copper nanoparticles. The Kirkendall effect is used in catalyst regeneration procedures. We can now follow the process using live imaging. We have studied the oxidation of CO with O2 on both Pt and Pd nanoparticles. Several process parameters have been varied, such as temperature and CO/O2 ratio. The already known spontaneous oscillations during this catalytic reaction have now been imaged live at the nanoscale. Our most recent data are on the formation of carbon shells around Co nanoparticles in CO.
Thursday, August 3, 2017 at 11:30am
Colburn Lab, 366 CLB
University of Delaware- Colburn Lab, University of Delaware, 150 Academy St, Newark, DE 19716-3196, USA