Synthesis and Characterization of Nanostructured Electro-active Materials
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With the rapidly increasing demand for better energy sources, material development for alternative energy storage and conversion systems has become extremely important. Among those, lithium ion batteries have achieved huge success in commercial use; however, progress still needs to be made to improve the performance. Toward this end, nanostructured materials have emerged as potential solutions toward smaller, cheaper, safer, and longer lasting batteries. One part of this dissertation focuses on the synthesis and characterization of nanostructured carbon materials for lithium ion batteries using electrospinning and nanoimprint lithography as primary synthesis methods. By appropriate nanostructuring, we have achieved improvement in electrochemical performance compared to that of the current state-of-art graphite anode, yet more effort is needed for further advancement. The other major portion of this dissertation is on the use of various scanning probe microscopy techniques to thoroughly characterize synthetic ferroelectrics for solar cell applications, and biological ferroelectrics for bio-compatible molecular electronics. The fundamentals of each scanning probe microscopy technique are first introduced, followed by a description of how they are applied to the ferroelectric materials to study different properties and behaviors. By combining piezoresponse force microscopy (PFM) and Kelvin probe force microscopy, we are able to establish solid proof that the perovskite is indeed ferroelectric, and also to observe the charge separation process when used as the light absorber layer in solar cells. More importantly, we investigated how the external light illumination interacts with the intrinsic ferroelectricity, to help understand the role of ferroelectricity in its superior performance in solar cells. PFM and conductive atomic force microscopy (c-AFM) also applied to study the ferroelectric resistive switching behavior in the biological ferroelectric elastin and its monomer level tropoelastin. Experimentally, we observed switchable diode-like conductance behavior and strong correlation to ferroelectric polarization which opens up new applications for those biological tissues.
- Mechanical engineering