Abstract
The increasing demand for renewable energy has lead to an interest in the field of energy conversion devices to exploit fluctuating energy production from solar cells and wind turbines. One of the solutions is the Solid Oxide Cell (SOC). Some of the new promising materials for SOCs are electrospun nanofibres of e.g. gadolinium doped ceria. However, characterizing these types of structures is challenging as they are polycrystalline complex nanostructured materials composed of hundreds-thousands of nano-grains with down to 1 nm wide grain boundaries. 3D Orientation Mapping in the Transmission Electron Microscope (3D-OMiTEM) is a promising technique that can non-destructively determine crystal orientations and morphology in 3D with a resolution of down to 1 nm. In this exploratory work the emphasis has been on applying 3D-OMiTEM on different materials to find potentials and challenges when applying the method. The three materials, maghemite nanoflowers, silver nanowire and electrospun gadolinium doped ceria nanofibres each showed different potentials of the 3D-OMiTEM technique. The main identified potentials are; the ability to do statistical morphological analysis on an ensemble of particles and crystallites, accurately determination of orientation and structures such as twin-structures and ultimately determination of transport properties through solids. To elaborate on the latter: This work shows how it is possible to determine a relationship between crystal orientation and doping concentration in the grain boundary of polycrystalline solids using a combination of 3D-OMiTEM and Energy Filtered Transmission Electron Microscopy (EFTEM). With this knowledge it is possible to calculate the ion conductivity path through the solid with the least resistance. This provides a new nsights to these kind of materials. Following this, preliminary results are presented showing possible methods for measuring conductivity of nanofibres. This could give a comparison value for the calculated path with least resistance from 3D-OMiTEM/EFTEM. Ultimately, conductivity measurements together with 3D-OMiTEM/EFTEM results can prove to be a strong tool in understanding and describing conductivities in ion conductive solids.
Info
Thesis PhD, 2020
UN SDG Classification
DK Main Research Area
Science/Technology
